In this second of a three-paper sequence, we developed a standard work using the Smoothed Particle Hydrodynamic (SPH) approach in LS-DYNA and compared the results against those the Lagrangian model and available experimental results. First, the SPH model was validated against a one-dimensional beam centered impact’s analytical solution and the results are within 3% error. Bird-strike events were divided into three separate problems: frontal impact on rigid flat plate, 0 and 30 deg impact on deformable tapered plate. The bird model was modeled as a cylindrical fluid. We successfully identified the most influencing parameters when using SPH in LS-DYNA. The case for 0 deg tapered plate impact shows little bird-plate interaction because the bird is sliced in two parts and the results are within 5% difference from the test data available in the literature, which is an improvement over the Lagrangian model. Conclusion: The developed SPH approach is suitable for bird-strike events within 10% error.
Bird-Strike Modeling Based on the Lagrangian Formulation Using LSDYNAdrboon
In this first paper of a three-paper sequence, we developed a standard work using the Lagrangian approach in LS-DYNA. The results were compared against experimental results. First, a simple one-dimensional beam centered impact problem was solved analytically to validate the results produced by LS-DYNA. For this case, the results were within 2.5% error when compared with the analytical solution. Bird-strike events were divided into three separate problems: frontal impact on rigid flat plate, 0 and 30 deg impact on deformable tapered plate. The bird model was modeled as a cylindrical fluid. The peak pressures and forces were compared to those results available in the literature. The case for 0 deg tapered plate impact shows little bird-plate interaction because the bird is sliced in two parts and the results were within 10% difference from the test data available in the literature. The developed Lagrangian approach is suitable for bird-strike events within 10% error.
Arbitrary Lagrange Eulerian Approach for Bird-Strike Analysis Using LS-DYNAdrboon
In this third and last sequence paper we focus on developing a model to simulate bird-strike events using Lagrange and Arbitrary Lagrange Eulerian (ALE) in LS-DYNA. We developed a standard work for the two-and three-dimensional models for bird-strike events. We modeled the bird as a cylinder fluid and the fan blade as a plate. The case study was that of frontal impact of soft-bodies on rigid plates based on the Lagrangian Bird Model. Results show very good agreement with available test data and within 7% error when compared with the Lagrange and SPH methods. The developed ALE approach is suitable for bird-strike events in tapered plates.
Galerkin’s indirect variational method in elastic stability analysis of all e...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Hyperelastic material models in finite element analysis of polymersKartik Srinivas
This paper describes the Hyperelastic material models and strain energy functions used in the finite element analysis (FEA) of polymers. Material characterization testing
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Characteristic orthogonal polynimial application to galerkin indirect variati...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Bird-Strike Modeling Based on the Lagrangian Formulation Using LSDYNAdrboon
In this first paper of a three-paper sequence, we developed a standard work using the Lagrangian approach in LS-DYNA. The results were compared against experimental results. First, a simple one-dimensional beam centered impact problem was solved analytically to validate the results produced by LS-DYNA. For this case, the results were within 2.5% error when compared with the analytical solution. Bird-strike events were divided into three separate problems: frontal impact on rigid flat plate, 0 and 30 deg impact on deformable tapered plate. The bird model was modeled as a cylindrical fluid. The peak pressures and forces were compared to those results available in the literature. The case for 0 deg tapered plate impact shows little bird-plate interaction because the bird is sliced in two parts and the results were within 10% difference from the test data available in the literature. The developed Lagrangian approach is suitable for bird-strike events within 10% error.
Arbitrary Lagrange Eulerian Approach for Bird-Strike Analysis Using LS-DYNAdrboon
In this third and last sequence paper we focus on developing a model to simulate bird-strike events using Lagrange and Arbitrary Lagrange Eulerian (ALE) in LS-DYNA. We developed a standard work for the two-and three-dimensional models for bird-strike events. We modeled the bird as a cylinder fluid and the fan blade as a plate. The case study was that of frontal impact of soft-bodies on rigid plates based on the Lagrangian Bird Model. Results show very good agreement with available test data and within 7% error when compared with the Lagrange and SPH methods. The developed ALE approach is suitable for bird-strike events in tapered plates.
Galerkin’s indirect variational method in elastic stability analysis of all e...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Hyperelastic material models in finite element analysis of polymersKartik Srinivas
This paper describes the Hyperelastic material models and strain energy functions used in the finite element analysis (FEA) of polymers. Material characterization testing
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Characteristic orthogonal polynimial application to galerkin indirect variati...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
APPLICATION OF COMPUTER FOR ANALYZING WORLD CO2 EMISSIONIJCSEA Journal
Global climate change due to CO2 emissions is an issue of international concern that primarily attributed
to fossil fuels. In this study, Genetic Algorithm (GA) is used for analyzing world CO2 emission based on the
global energy consumption. Linear and non-linear forms of equations were developed to forecast CO2
emission using Genetic Algorithm (GA) based on the global oil, natural gas, coal, and primary energy
consumption figures. The related data between 1980 and 2010 were used, partly for installing the models
(finding candidates of best weighting factors for each model (1980-2003)) and partly for testing the models
(2004–2010). Global CO2 emission is forecasted up to year 2030.
Experimental and numerical analysis of elasto-plastic behaviour of notched sp...IJERA Editor
The objective of the work was to estimate the elasto-plastic stress and strain behaviour at the root of the notch of
an Al 6061 plate undergoing tensile and compressive cyclic loading by both experimental and numerical
methods. This attempt to measured initial elasto-plastic stresses experimentally then verified by numerically.
The various Kt values such as 2, 4 and 6 specimens were subjected to tensile test using a computerised universal
testing machine. Numerical approach associated with body discretization and developed finite element model
with sufficient degree of freedom to analyses elasto-plastic analysis of notched specimen. Experimental results
show that analysis of three Kt notched specimens had similar behaviour of elasto-plastic behaviour but different
magnitude. The experimental results compare well with the numerical results which are obtained during finite
element analysis of notched specimens.
Measuring Plastic Properties from Sharp Nanoindentation: A Finite-Element Stu...CrimsonPublishersRDMS
Measuring Plastic Properties from Sharp Nanoindentation: A Finite-Element Study on the Uniqueness of Inverse Solutions by Fabian Pöhl* in Crimson Publishers: Peer Reviewed Material Science Journals
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Size effect of plain concrete beams–an experimental studyeSAT Journals
Abstract
The paper analyses the size dependency of the fracture energy (GF) and the effective length of fracture process zone (Cf) of concrete
determined as per the Bazant’s Size effect method and RILEM Work-of-fracture methods. The fracture parameters (GF,Cf) are
determined by measuring the maximum loads of geometrically similar notched plain concrete (M25) specimens of different sizes in a
size ratio of 1:5 with different pre-cast notch depths (a/d=0.15, 0.30 and 0.45) under three point bending through load-deflection
curves. In each notch depth ratio, 15 beams are cast and tested with 03 similar specimens in each size of the beams. Total beams
tested are 45.The variation of both the fracture energy and the effective length of fracture process zone as a function of the specimen
size and notch depth is determined using Bazant’s Size effect method and RILEM Work-of-fracture method. Fracture energy and
Fracture process zone length determined by Size effect method are found to be decreasing with the increasing notch depth ratios.
Fracture energy calculated using Work-of-fracture method is increasing with the increase in size of specimen and decreasing with the
increasing notch depth ratios.
Numerical modeling of the welding defect influence on fatigue life of the wel...inventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
Performance of Soft Soil Stabilized by Fly Ash with Natural Fiber Reinforceme...AM Publications
The use of clay as a landfill cover system is a choice of alternative materials that are widely used in almost all the existing landfill system in Indonesia and in the world. In addition to the relatively low cost of procurement is also available in almost all regions in Indonesia. However, alternative reliable overburden landfills has not been much discussed and researched. The purpose of this study is to design an ideal final cover layer landfill technically and mechanically. The results showed that the addition of fly ash and palm oil fiber (POF) between 10% of fly ash and 0.5% of POF can enhance the mechanical value of soils. the compressive strength of soils increase from 39.4 kPa to 89.0 kPa or rose by 129%, decreasing the value of soil hydraulic conductivity is to be 1,2x10-7 from the initial value of 1,17x10-6 or decreased by 850.4%, increase in soil friction angle of 8.55° to 24 °, and lowering the soil liquid limit of 33.48% to 24.5%, decreasing of swelling potential of 8 % to only 1.5% at the end of the wetting cycle, reduce the cracking intensity factor (CIF) from 1.96% to zero cracks. Mechanical behavior is heavily influenced by the nature of fly ash which has of a small water absorption and change the water in the soil for the pozzolanic reaction and produce calcium hydrate silica (CSH), in which the reaction is to form granules (binder) in the soil so that the soil becomes dense and hard, while palm oil fiber have cellulose and lignin as dominant compounds that tend to have high water absorption but serves to strengthen the fiber tensile force between the fibers and the soils surface due to adhesion forces so that the soil is not easily collapse and reduce the potential shrinkages and cracking of the soils.
Study of Silica Fume Blended Concrete using Statistical Mixture Experiment an...ijtsrd
The prime objective of this study is to design, analyze and optimize the silica fume blended concrete using Statistical Mixture Experiment and to explore the practicability of Statistical mixture experiment in mix design of concrete containing the several components. The traditional mix design methods have drawbacks. Traditional method of mix design of concrete fails in designing the complex concrete mixture containing the cementitious materials, pozzolanic materials and several admixtures. Traditional methods are based on trial and error method in which effect of only one component can be determined. Trial and error does not provide the whole picture of concrete mixture. In this study, the statistical mixture design method is employed to analyze the effects of silica fume on 28 days compressive strength of concrete and to design and optimize the silica fume blended concrete. The components of concrete mixture are Cement, silica fume, water and aggregate. Total of 15 runs or design points are generated which are combinations of proportions and laboratory experiment is carried out on these design points and 28 days compressive strength is measured. Mathematical relationship is established between 28 days compressive strength and proportions of components using least square technique and then mathematical model is studied to analyze the effects of silica fume in concrete. Pankaj Kumar | M. C Paliwal ""Study of Silica Fume Blended Concrete using Statistical Mixture Experiment and Optimizing of Compressive Strength of Cement Concrete"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-4 , June 2019, URL: https://www.ijtsrd.com/papers/ijtsrd25178.pdf
Paper URL: https://www.ijtsrd.com/engineering/civil-engineering/25178/study-of-silica-fume-blended-concrete-using-statistical-mixture-experiment-and-optimizing-of-compressive-strength-of-cement-concrete/pankaj-kumar
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Improving the Efficiency of Ratio Estimators by Calibration WeightingsPremier Publishers
It is observed that the performances of most improved ratio estimators depend on some optimality conditions that need to be satisfied to guarantee better estimator. This paper develops a new approach to ratio estimation that produces a more efficient class of ratio estimators that do not depend on any optimality conditions for optimum performance using calibration weightings. The relative performances of the proposed calibration ratio estimators are compared with a corresponding global [Generalized Regression (GREG)] estimator. Results of analysis showed that the proposed calibration ratio estimators are substantially superior to the traditional GREG-estimator with relatively small bias, mean square error, average length of confidence interval and coverage probability. In general, the proposed calibration ratio estimators are more efficient than all existing estimators considered in the study.
Possible limits of accuracy in measurement of fundamental physical constantsirjes
The measurement uncertainties of Fundamental Physical Constants should take into account all
possible and most influencing factors. One from them is the finiteness of the model that causes the existence of
a-priori error. The proposed formula for calculation of this error provides a comparison of its value with the
actual experimental measurement error that cannot be done an arbitrarily small. According to the suggested
approach, the error of the researched Fundamental Physical Constant, measured in conventional field studies,
will always be higher than the error caused by the finite number of dimensional recorded variables of physicalmathematical
models. Examples of practical application of the considered concept for measurement of fine
structure constant, speed of light and Newtonian constant of gravitation are discussed.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
APPLICATION OF COMPUTER FOR ANALYZING WORLD CO2 EMISSIONIJCSEA Journal
Global climate change due to CO2 emissions is an issue of international concern that primarily attributed
to fossil fuels. In this study, Genetic Algorithm (GA) is used for analyzing world CO2 emission based on the
global energy consumption. Linear and non-linear forms of equations were developed to forecast CO2
emission using Genetic Algorithm (GA) based on the global oil, natural gas, coal, and primary energy
consumption figures. The related data between 1980 and 2010 were used, partly for installing the models
(finding candidates of best weighting factors for each model (1980-2003)) and partly for testing the models
(2004–2010). Global CO2 emission is forecasted up to year 2030.
Experimental and numerical analysis of elasto-plastic behaviour of notched sp...IJERA Editor
The objective of the work was to estimate the elasto-plastic stress and strain behaviour at the root of the notch of
an Al 6061 plate undergoing tensile and compressive cyclic loading by both experimental and numerical
methods. This attempt to measured initial elasto-plastic stresses experimentally then verified by numerically.
The various Kt values such as 2, 4 and 6 specimens were subjected to tensile test using a computerised universal
testing machine. Numerical approach associated with body discretization and developed finite element model
with sufficient degree of freedom to analyses elasto-plastic analysis of notched specimen. Experimental results
show that analysis of three Kt notched specimens had similar behaviour of elasto-plastic behaviour but different
magnitude. The experimental results compare well with the numerical results which are obtained during finite
element analysis of notched specimens.
Measuring Plastic Properties from Sharp Nanoindentation: A Finite-Element Stu...CrimsonPublishersRDMS
Measuring Plastic Properties from Sharp Nanoindentation: A Finite-Element Study on the Uniqueness of Inverse Solutions by Fabian Pöhl* in Crimson Publishers: Peer Reviewed Material Science Journals
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Size effect of plain concrete beams–an experimental studyeSAT Journals
Abstract
The paper analyses the size dependency of the fracture energy (GF) and the effective length of fracture process zone (Cf) of concrete
determined as per the Bazant’s Size effect method and RILEM Work-of-fracture methods. The fracture parameters (GF,Cf) are
determined by measuring the maximum loads of geometrically similar notched plain concrete (M25) specimens of different sizes in a
size ratio of 1:5 with different pre-cast notch depths (a/d=0.15, 0.30 and 0.45) under three point bending through load-deflection
curves. In each notch depth ratio, 15 beams are cast and tested with 03 similar specimens in each size of the beams. Total beams
tested are 45.The variation of both the fracture energy and the effective length of fracture process zone as a function of the specimen
size and notch depth is determined using Bazant’s Size effect method and RILEM Work-of-fracture method. Fracture energy and
Fracture process zone length determined by Size effect method are found to be decreasing with the increasing notch depth ratios.
Fracture energy calculated using Work-of-fracture method is increasing with the increase in size of specimen and decreasing with the
increasing notch depth ratios.
Numerical modeling of the welding defect influence on fatigue life of the wel...inventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
Performance of Soft Soil Stabilized by Fly Ash with Natural Fiber Reinforceme...AM Publications
The use of clay as a landfill cover system is a choice of alternative materials that are widely used in almost all the existing landfill system in Indonesia and in the world. In addition to the relatively low cost of procurement is also available in almost all regions in Indonesia. However, alternative reliable overburden landfills has not been much discussed and researched. The purpose of this study is to design an ideal final cover layer landfill technically and mechanically. The results showed that the addition of fly ash and palm oil fiber (POF) between 10% of fly ash and 0.5% of POF can enhance the mechanical value of soils. the compressive strength of soils increase from 39.4 kPa to 89.0 kPa or rose by 129%, decreasing the value of soil hydraulic conductivity is to be 1,2x10-7 from the initial value of 1,17x10-6 or decreased by 850.4%, increase in soil friction angle of 8.55° to 24 °, and lowering the soil liquid limit of 33.48% to 24.5%, decreasing of swelling potential of 8 % to only 1.5% at the end of the wetting cycle, reduce the cracking intensity factor (CIF) from 1.96% to zero cracks. Mechanical behavior is heavily influenced by the nature of fly ash which has of a small water absorption and change the water in the soil for the pozzolanic reaction and produce calcium hydrate silica (CSH), in which the reaction is to form granules (binder) in the soil so that the soil becomes dense and hard, while palm oil fiber have cellulose and lignin as dominant compounds that tend to have high water absorption but serves to strengthen the fiber tensile force between the fibers and the soils surface due to adhesion forces so that the soil is not easily collapse and reduce the potential shrinkages and cracking of the soils.
Study of Silica Fume Blended Concrete using Statistical Mixture Experiment an...ijtsrd
The prime objective of this study is to design, analyze and optimize the silica fume blended concrete using Statistical Mixture Experiment and to explore the practicability of Statistical mixture experiment in mix design of concrete containing the several components. The traditional mix design methods have drawbacks. Traditional method of mix design of concrete fails in designing the complex concrete mixture containing the cementitious materials, pozzolanic materials and several admixtures. Traditional methods are based on trial and error method in which effect of only one component can be determined. Trial and error does not provide the whole picture of concrete mixture. In this study, the statistical mixture design method is employed to analyze the effects of silica fume on 28 days compressive strength of concrete and to design and optimize the silica fume blended concrete. The components of concrete mixture are Cement, silica fume, water and aggregate. Total of 15 runs or design points are generated which are combinations of proportions and laboratory experiment is carried out on these design points and 28 days compressive strength is measured. Mathematical relationship is established between 28 days compressive strength and proportions of components using least square technique and then mathematical model is studied to analyze the effects of silica fume in concrete. Pankaj Kumar | M. C Paliwal ""Study of Silica Fume Blended Concrete using Statistical Mixture Experiment and Optimizing of Compressive Strength of Cement Concrete"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-4 , June 2019, URL: https://www.ijtsrd.com/papers/ijtsrd25178.pdf
Paper URL: https://www.ijtsrd.com/engineering/civil-engineering/25178/study-of-silica-fume-blended-concrete-using-statistical-mixture-experiment-and-optimizing-of-compressive-strength-of-cement-concrete/pankaj-kumar
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Improving the Efficiency of Ratio Estimators by Calibration WeightingsPremier Publishers
It is observed that the performances of most improved ratio estimators depend on some optimality conditions that need to be satisfied to guarantee better estimator. This paper develops a new approach to ratio estimation that produces a more efficient class of ratio estimators that do not depend on any optimality conditions for optimum performance using calibration weightings. The relative performances of the proposed calibration ratio estimators are compared with a corresponding global [Generalized Regression (GREG)] estimator. Results of analysis showed that the proposed calibration ratio estimators are substantially superior to the traditional GREG-estimator with relatively small bias, mean square error, average length of confidence interval and coverage probability. In general, the proposed calibration ratio estimators are more efficient than all existing estimators considered in the study.
Possible limits of accuracy in measurement of fundamental physical constantsirjes
The measurement uncertainties of Fundamental Physical Constants should take into account all
possible and most influencing factors. One from them is the finiteness of the model that causes the existence of
a-priori error. The proposed formula for calculation of this error provides a comparison of its value with the
actual experimental measurement error that cannot be done an arbitrarily small. According to the suggested
approach, the error of the researched Fundamental Physical Constant, measured in conventional field studies,
will always be higher than the error caused by the finite number of dimensional recorded variables of physicalmathematical
models. Examples of practical application of the considered concept for measurement of fine
structure constant, speed of light and Newtonian constant of gravitation are discussed.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Dynamics Behaviour of Multi Storeys Framed Structures by of Iterative Method AM Publications
Dynamics refers to the branch of mechanics that deals with the movement of objects and the forces that drive that movement. Structural analysis which covers the behaviour of structures subjected to dynamic (actions having high acceleration) loading. Dynamic loads include people, wind, waves, traffic, earthquakes, and blasts. Any structure can be subjected to dynamic loading. Dynamic analysis can be used to find dynamic displacements, time history, and the frequency content of the load. One analysis technique for calculating the linear response of structures to dynamic loading is a modal analysis. In modal analysis, we decompose the response of the structure into several vibration modes. A mode is defined by its frequency and shape. Structural engineers call the mode with the shortest frequency (the longest period) the fundamental mode. This paper presents a study on mode shape, inertia force, spring force and deflection of multi storied framed structures by comparison of stodola’s and Holzer method. This study involves in examination of theoretical investigations of multi storied framed structures. Overall four storey multi storied framed structures and two methods were analysed & comparison of all the mode shape, inertia force, spring force and deflection at the critical cross-section with same configuration loading by keeping all other parameters constant. The theoretical data are calculated using code IS 1893, IS 4326, IS 13920. The all storey mass and stiffens are analysed under the cantilever condition. The research project aims to provide which method is most accuracy to find the mode shape, spring force deflection and inertia force. The studies reveal that the theoretical investigations Stodola’s method is most accuracy compare to the Holzer method. The maximum mode shape, spring force, spring deflection and inertia force is 87.29%, 80 %, 89% and 72% is higher the Stodola’s method compare than Holzer method in same configuration.
A review and buckling analysis of stiffened plateeSAT Journals
Abstract It happens many times that the structure is safe in normal stress and deflection but fails in buckling. Buckling analysis is one of the method to go for such type of analysis.It predicts various modes of buckling. Plates are used in many applications such as structures, aerospace, automobile etc. Such structures are subjected to heavy uniformly distributed load and concentrated load many times over it’s life span. Strength of these structures are increased by adding stiffeners to its plate. This paper deals with the analysis of rectangular stiffened plates which forms the basis of structures. A comparison of stiffened plate and unstiffened plate is done for the same dimensions. In order to continue this analysis various research papers were studied to understand the previous tasks done for stiffened plate. Hyper mesh and Nastran is used in this research work.Buckling analysis is performed for the component with aspect ratio of 2.Rectangular flat bar is used as stiffener Keywords: Stiffened Plate; Dynamic load; Buckling; Aspect ratio;Buckling Analysis.
In this paper we have analyzed the stress distribution over a rectangular specimen
with hybrid composite material at its central hole. Using Vacuum bag technique the
material has been fabricated and it consists of carbon and glass fiber with epoxy. The
cross ply lamina arrangement with alternate carbon and glass has increased the
strength of the structure. This is because carbon properties are high compared to
glass. The cutouts made in typical aircraft and automobile components reduce the
weight and bulking load carrying capacity of the aircraft according to the weight
reduction law. Three specimens were used to carry out experimental investigations as
per ASTM D5766 in the universal testing machine. We have analyzed and compared
the results of the stress concentration in the rectangular specimen with a hole using
FEA
Damage detection in cfrp plates by means of numerical modeling of lamb waves ...eSAT Journals
Abstract
The paper presents an application of modeling acoustic waves propagation in a carbon fiber reinforced plastic (CFRP) plates for
damage detection. This task is a part of non-destructive testing (NDT) methods which are very important in many industry
branches. Propagation of Lamb waves is modeled using three-dimensional finite element method by means of commercial
software. In the paper three different cases of plate structures with and without flaws are considered to present review of selected
methods for the detection of defects in time and frequency domain. These are comparisons of: A-scans, B-scans, dispersion
curves, spectrograms, scalograms and energy plots. Developed numerical model first has been validated by means of analytical
solution for isotropic plate.
Keywords: Lamb waves, non-destructive testing, finite element method, damage detection
An Overview of Clearance Optimization in Sheet Metal Blanking ProcessIJMER
Abstract: This document prescribes a model investigation the effect of potential parameters influencing the blanking
process and their interaction. The blanking process optimization carried out by using Design of Experiment (DOE), Finite
Element Method (FEM) with ANSYS Package, Simulation with ABAQUS-Explicit software, Blank soft Software and Neural
Network Simulation in order to achieve the intended model objectives.
Keywords: Blanking Process, DOE, FEM, Optimum Clearance and Simulation.
Natural convection in a differentially heated cavity plays a
major role in the understanding of flow physics and heat
transfer aspects of various applications. Parameters such as
Rayleigh number, Prandtl number, aspect ratio, inclination
angle and surface emissivity are considered to have either
individual or grouped effect on natural convection in an
enclosed cavity. In spite of this, simultaneous study of these
parameters over a wide range is rare. Development of
correlation which helps to investigate the effect of the large
number and wide range of parameters is challenging. The
number of simulations required to generate correlations for
even a small number of parameters is extremely large. Till
date there is no streamlined procedure to optimize the number
of simulations required for correlation development.
Therefore, the present study aims to optimize the number of
simulations by using Taguchi technique and later generate
correlations by employing multiple variable regression
analysis. It is observed that for a wide range of parameters,
the proposed CFD-Taguchi-Regression approach drastically
reduces the total number of simulations for correlation
generation.
INTERFACIAL DELAMINATION FAILURE IN BONDED CONCRETE OVERLAY SYSTEMS - A REVIE...IAEME Publication
This study reviews the theories and modelling methods for describing interfacial delamination failure process between two bonded cementitious materials. Complex interfacial stress
conditions at discontinuities and areas of high stress concentrations were primary areas of concern. Distinct analytical cases involving intrinsic material and structural property variables were considered. An approach based on plane strain analysis within the context of Interface Cohesive
Zone Model (ICZM) was cited and presented as viable for describing and predicting delamination mode of failure in bonded concrete overlays systems (BCOs).
NUMERICAL STUDY OF FLUID FLOW AROUND A DIVER HELPERijmech
Having access to high speed diving without the use of mechanical science and discovery centers have been
considered. Production of simple, yet effective tool to reduce energy consumption and associated diver is
very valuable. Assistant diver device that works with human muscle power, includes a pair of ballets. This
system reduces the energy required to dive to less than half as the speed increases to 2 to 5 knot. Using
numerical methods can answer a lot of questions and a simulation of the dynamic behavior of the device. In
this article, modeling of fluid flow around the Diver helper of FLUENT software and using Dynamic Mesh
have been done.
Flow lines show an increase in the angle of the fins and causes development of vortices behind them.
Pressure Cantor can also be used in the analysis of the fins. The drag coefficient ballet based on the device
at various angles in a period is reported in charts.
Limitations of symmetry in fe modeling a comparison of fem and a (1)Kunal Bhatt
It has long been an accepted practice to use symmetry in Finite Element Modeling.
Whenever modeling a large structure, we turn to symmetry in order to significantly reduce the model
size and computation time. But is symmetry always the solution to long computation times, and is it
always accurate?
Failure waves in glass were first observed in tests some 30 years ago, with a wave velocity of 1.5-2.5 km/s. In spite of the long time since then, some essential questions concerning failure waves remained unanswered. These are: 1) what is the formation mechanism of failure waves; 2) what is the propagation mechanism of failure waves; and 3) what are the kinetics of the failure process? In the past failure wave researchers assumed that material damage starts from the boundary. But in a recent experimental work on glass [9] the investigators observed that the glass starts to fail within the material behind the shock front, and not from the boundary. This seemingly small change in the way failure waves are started makes it possible to predict the mechanics of failure wave formation and propagation, using existing failure models for brittle materials. We’re using here a dynamic failure model for brittle materials that we’ve developed in recent years [10]. To get a failure wave that lags behind the shock front, we assume in that the rate of damage accumulation behind the shock front decreases exponentially with distance from the boundary. This is a plausible assumption because opening pores and cracks would become more difficult with distance from the boundary. And indeed, using this assumption we get a failure wave that propagates slower than the shock and at an approximately constant velocity.
www.elsevier.comlocatecompstrucComputers and Structures .docxjeffevans62972
www.elsevier.com/locate/compstruc
Computers and Structures 85 (2007) 235–243
On the treatment of uncertainties in structural mechanics and analysis q
G.I. Schuëller *
Institute of Engineering Mechanics, Leopold-Franzens University Innsbruck, Technikerstr. 13, 6020 Innsbruck, Austria
Received 9 August 2006; accepted 31 October 2006
Available online 22 December 2006
Abstract
In this paper the need for a rational treatment of uncertainties in structural mechanics and analysis is reasoned. It is shown that the
traditional deterministic conception can be easily extended by applying statistical and probabilistic concepts. The so-called Monte Carlo
simulation procedure is the key for those developments, as it allows the straightforward use of the currently used deterministic analysis
procedures.
A numerical example exemplifies the methodology. It is concluded that uncertainty analysis may ensure robust predictions of vari-
ability, model verification, safety assessment, etc.
� 2006 Elsevier Ltd. All rights reserved.
Keywords: Uncertainty; Monte Carlo simulaton; Finite elements; Response variability; Model verification; Robustness
1. Introduction
Structural mechanics analysis up to this date, generally is
still based on a deterministic conception. Observed varia-
tions in loading conditions, material properties, geometry,
etc. are taken into account by either selecting extremely
high, low or average values, respectively, for representing
the parameters. Hence, this way, uncertainties inherent in
almost every analysis process are considered just intuitively.
Observations and measurements of physical processes,
however, show not only variability, but also random char-
acteristics. Statistical and probabilistic procedures provide
a sound frame work for a rational treatment of analysis
of these uncertainties. Moreover there are various types of
uncertainties to be dealt with. While the uncertainties in
mechanical modeling can be reduced as additional knowl-
edge becomes available, the physical or intrinsic uncertain-
ties, e.g. of environmental loading, can not. Furthermore,
0045-7949/$ - see front matter � 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.compstruc.2006.10.009
q Plenary Keynote Lecture presented at the 3rd MIT Conference on
Computational Fluid and Solid Mechanics, Boston, MA, USA, June 14–
17, 2005.
* Tel.: +43 512 507 6841; fax: +43 512 507 2905.
E-mail address: [email protected]
the entire spectrum of uncertainties is also not known. In
reality, neither the true model nor the model parameters
are deterministically known. Assuming that by finite ele-
ment (FE) procedures structures and continua can be repre-
sented reasonably well the question of the effect of the
discretization still remains. It is generally expected, that
an increase in the size of the structural models, in terms of
degrees of freedom, will increase the level of realism of the
model. Comparisons with measurements, however, clearly
show that this expect.
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Smooth Particle Hydrodynamics for Bird-Strike Analysis Using LS-DYNA
1. 2013 American Transactions on Engineering & Applied Sciences.
American Transactions on
Engineering & Applied Sciences
http://TuEngr.com/ATEAS
Smooth Particle Hydrodynamics for BirdStrike
Analysis Using LSDYNA
Vijay K. Goyal
a
b
a*
a
, Carlos A. Huertas , Thomas J. Vasko
b
Department of Mechanical Engineering, University of Puerto Rico at Mayagüez, PR 00680, USA
Engineering Department, Central Connecticut State University, New Britain, CT 06050, USA
ARTICLEINFO
A B S T RA C T
Article history:
Received December 23, 2012
Received in revised form
24 February 2013
Accepted February 26, 2013
Available online
March 04, 2013
In this second of a three-paper sequence, we developed a
standard work using the Smoothed Particle Hydrodynamic (SPH)
approach in LS-DYNA and compared the results against those the
Lagrangian model and available experimental results. First, the SPH
model was validated against a one-dimensional beam centered
impact’s analytical solution and the results are within 3% error.
Bird-strike events were divided into three separate problems: frontal
impact on rigid flat plate, 0 and 30 deg impact on deformable tapered
plate. The bird model was modeled as a cylindrical fluid. We
successfully identified the most influencing parameters when using
SPH in LS-DYNA. The case for 0 deg tapered plate impact shows
little bird-plate interaction because the bird is sliced in two parts and
the results are within 5% difference from the test data available in the
literature, which is an improvement over the Lagrangian model.
Conclusion: The developed SPH approach is suitable for bird-strike
events within 10% error.
Keywords:
Finite element;
Impact analysis;
Bird-strike;
Smooth-particle
hydrodynamics.
2013 Am. Trans. Eng. Appl. Sci.
*Corresponding author (V. Goyal), Tel.: 1-787-832-4040 Ext. 2111; E-mail:
2013. American Transactions on Engineering & Applied Sciences.
vijay.goyal@upr.edu.
Volume 2 No. 2
ISSN 2229-1652 eISSN 2229-1660
Online Available at
http://TuEngr.com/ATEAS/V02/083-107.pdf
83
2. 1. Introduction
1.1 Motivation
As we mentioned in the first paper [1], collisions between a bird and an aircraft are known as
bird-strike events. According to the Federal Aviation Administration (FAA), wildlife strikes cost
the U.S. civil aviation industry over $300 million and more than 500,000 downtime hours each
year [2].
We previously developed the Lagrangian model to predict bird-strike events [1]. However,
this description causes losses of the bird mass due to the fluid behavior of the bird, which causes
large distortions in the bird model. This mass loss may reduce the real loads applied to the fan
blade, which is the reason why the Smoothed Particle Hydrodynamics (SPH) is being studied in
this work. LS-DYNA has the capability to use SPH formulation to model this fluid-structure
interaction problem. In this work, we plan on developing a SPH standard work to modeling
bird-strike events.
1.2 Background on Impact Problems
The impact event is not a new topic and it has been studied by various authors [3, 4, 5, and 6] .
The characterization of birds impacting a rigid plate was studied by Barber et al. [7]. They found
that peak pressures were generated in the impact of the bird against a rigid circular plate. This peak
pressures were independent of the bird size and proportional to the square of the impact velocity.
Four steps concerning the impact pressures were found: initial shock (Hugonniot Pressure), impact
shock decay, a steady state phase and the final decay of the pressure. This pressure plots were used
as a reference to compare the obtained pressures in the LS-DYNA simulation of the bird-strike
event.
Bird-strike events have been studied using Lagrangian method in different finite element
codes [8]. But we seek a model with a better correlation. As we did for the case of Lagrangian
model we will use the work by Moffat et al. [9] and Barber et al. [7] as our reference. The
geometrical model that was used for the bird was a cylinder with spherical ends with an overall
length of 15.24 cm and a diameter of 7.62 cm. The bird density is 950 kg/m3. Moffat et al. [9]
found that the pressures were insensitive to the strength of the bird and a yield stress of 3.45 MPa
84
Vijay K. Goyal, Carlos A. Huertas, and Thomas J. Vasko
3. was taken for the rigid plate impact analysis. For the tapered plate impact simulation a 7.62 × 22.86
cm plate was used. The plate was tapered by 4° and the edge thickness was 0.051 cm which
blended to 0.160 cm for the majority of the plate. The work did not specify the kind of element
that was used for the tapered plate. All LS-DYNA simulation for the tapered plate were simulated
using shell elements.
1.3 Smoothed Particle Hydrodynamics
The SPH is a meshless or griddles technique that does not suffer from the normal problems of
grid tangling in large deformation problems. The major advantages of the SPH technique is that it
does not require a numerical grid and, since it is a Lagrangian method by nature, it allows efficient
tracking of material deformations and history-dependent behavior. Because the SPH method has
not been fully developed there remain some issues in the areas of stability, consistency, and
conservation. Lagrangian motions of mass points or particles are really interpolation points, which
are approximated by a cubic B-spline function. Unlike finite element representations for a
structure, this finite element model does not exhibit a fixed connectivity between adjacent elements
during the impact event. The determination of which elements are nearest neighbors is limited by
the search radius. The search radius defines the maximum distance from the center node that an
element may search for nearest neighbors and becomes in effect a measure of the fluid cohesive
strength.
Martin [10] studied a transient, material, and geometric nonlinear finite element based impact
analysis using PW/WHAM. His work consisted in simulating soft body impact over stainless steel
disc, a deformable flat plate, and a tapered plate. The formulation employed was very similar to the
concept of the meshless finite element technique SPH. Many authors have presented basic
equations related with the SPH approach. Commonwealth Scientific & Industrial Research
Organization (CSIRO) provided the equations for the SPH approximation using the smoothing
kernel function. Lacome [11] described the conventions used for the selection of the smoothing
length. This is a very important parameter because the spatial resolution of the model depends on
the smoothing length and the characteristic length of the meshed particle. La-come [12] also
provided important information regarding the SPH process, the process of the neighbor search in
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4. the interpolation and the SPH approximations for the equations of energy and mass conservation.
A general description of the SPH method was presented by Hut et al. [13]. The authors
presented applications of the method as well as information about the computational parameters for
the SPH method and the expectations for accelerating processing time with the implementation of
faster computers.
In this work, we attempt to create a standard work based on the SPH formulation by
identifying the most important influencing parameters in the bird-strike simulation and validate the
simulation with the test data and compare against the Lagrangian model previously developed
[1].
2. Impact Analysis
The bird-strike events are considered as soft body impact in structural analysis because the
yield point of the bird is far smaller when compared with that of the target. Thus, the bird at the
impact can be considered as a fluid material. The soft body impact results in damage over a larger
area if compared with ballistic impacts. Let us understand the main equations involved in this
study.
2.1 A Continuum Approach
Three major equations are solved by LS-DYNA to obtain the velocity, density, and pressure of
the fluid for a specific position and time. These equations are conservation of mass, conservation of
momentum, and constitutive relationship of the material and are essential to solve the soft body
impact problem (Cassenti [6]). The conservation of momentum can be stated as follows:
(1)
where P represents a diagonal matrix containing only normal pressure components, ρ the density,
and V the velocity vector. The conservation of mass per unit volume equation can be written as
follows:
(2)
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Vijay K. Goyal, Carlos A. Huertas, and Thomas J. Vasko
5. The last equation is that of the constitutive relation and can be expressed in its general form as
follows:
(3)
2.2 SPH Approach
Smooth Particle Hydrodynamics (SPH) formulation is a meshless Lagrangian technique used
to model the fluid equations of motion using a pseudo-particle interpolation method to compute
smooth hydrodynamic variables. Initially this method was used to simulate astrophysical
phenomenon, but recently it has been used to resolve other physics problems in continuum
mechanics, crash simulations, brittle and ductile fracture in solids. Due to the absence of a grid, this
method allows solving many problems that are hardly reproducible in other classical methods
discarding the problem of large mesh deformations or tangling. Another advantage of the SPH
method is that due to the absence of a mesh, problems with irregular geometry can be solved.
Figure 1: Integration cycle in time of the SPH computation process.
In this formulation, the fluid is represented as a set of moving particles, each one representing
an interpolation point, where all the fluid properties are known. Then, with a regular interpolation
function called smoothing length the solution of the desired quantities can be calculated for all the
particles. A real fluid can be modeled as many fluid particles provided that the particles are small
compared to the scale over which macroscopic properties of the fluid varies, but large enough to
contain many molecules so macroscopic properties can be defined sensibly. A large number of
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6. particles are needed for the SPH calculations, since the continuum limit is recovered when the
number of particles goes to infinity. Particles in the SPH method carry information about their
hydrodynamic and thermodynamic information, this in addition to the mass needed to specify the
evolution of the fluid. Nodes in SPH are similar to nodes in a mesh, the difference is that these
nodes are continuously deformable and distort automatically to put more of the computational
effort in regions of relatively high density.
One disadvantage in SPH is that this method is computationally demanding, both in memory
and in CPU time. This can be overcome using a parallel analysis with more than one CPU. There is
also the difficulty of establishing the boundary condition when using the SPH method. Another
disadvantage is that particles may penetrate the boundaries and causing loss of smoothness and
accuracy.
Figure 2: Neighbor search particles inside a 2h radius sphere.
Figure 1 illustrates an integration cycle in time of the SPH computation process (Lacome
[12]). In the SPH analysis, it is important to know which particle will interact with its neighbors
because the interpolation depends on these interactions. Therefore, a neighboring search technique
has been developed, as shown in Figure 2 (Lacome [12]). The influence of a particle is established
inside of a sphere of radius of 2h, where h is the smoothing length In the neighboring search, it is
also important to list, for each time step, the particles that are inside that sphere. If we have N
particles, then it is required (N − 1) distance comparison. If this comparison is done for each
particle, then the total amount of comparisons will be N(N − 1). It is better to have a variable
smoothing length to avoid problems related with expansion and compression of material. The main
idea of this concept is that it is necessary to keep enough particles in the neighborhood to validate
the approximation of continuum variables. The smoothing is allowed to vary in time and space. For
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Vijay K. Goyal, Carlos A. Huertas, and Thomas J. Vasko
7. a constant smoothing length, a material expansion can lead to numerical fracture and a material
compression can slow down the calculation significantly.
2.3 Material Models
The type of materials used for the bird model was material null, which considers a fluid
material composed of 90% of water and 10% of air. This material allows consider equation of state
without computing deviatoric stresses. The equation of state used with this material was the
equation of state tabulated. This equation of state defines the pressure P as follows
For the type of impact problems studied in this work, temperature does not play a big role. In this
context, the term
The volumetric strain
vanishes and thus the equation of state reduces to
is given by the natural logarithm of the relative volume.
Figure 3: Beam impact problem.
3. Beam Centered Impact Problem
Before studying bird-strike events, we proceeded to solve a beam centered impact problem
(Goyal and Huertas [14]). The problem consisted in taking a simply supported beam of length, L,
of 100 mm over which a rigid object of mass, mA, of 2.233g impacts at a constant initial velocity of,
(vA) 1,100 m/s. The beam has a solid squared cross section of length 4 mm, modulus of elasticity,
EB, of 205 GPa, and a density, ρB, of 3.925 kg/m3. Figure 3 shows a schematic of the problem.
The goal of this problem is to obtain the pressure maximum peak pressure exerted at the moment of
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8. impact. The problem is solve analytically and then compared to the corresponding outputs from
LS-DYNA for the Lagrange method.
Figure 4: Beam impact problem simplification.
3.1 Analytical Solution
Since the impact occurs at only one point, the problem can be solved by concentrating all the
mass of the beam at the point of impact, i.e., at the center of the beam. This will simplify the
problem to a problem of central impact between two masses, as shown in Figure 4. The theorem
of impulse and momentum may be divided into two parts, as shown in Figure 5. We show [1] that
the impulsive time-average constant force Fave acting during the time of the impact is found using
the following equation:
(4)
Where ∆ is the time it takes to complete the impact. Equation (4) has two unknowns: the average
force and the impact time. The impact time is taken to match the impact time given by LS-DYNA,
and thus perform a fair comparison. Once the impact time in known, the force is obtained straight
forward using Eq. (4).
Figure 5: Visualization of the theorem of impulse and momentum.
3.2 SPH Simulation
Now we solve the problem using the SPH description in LS-DYNA. In this case the projectile
was composed of SPH particles and a large modulus of elasticity was used to model the rigid target.
Figure 6 shows the SPH simulation and Figure 7 shows the plot for the impact force. The measured
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Vijay K. Goyal, Carlos A. Huertas, and Thomas J. Vasko
9. impact time was ∆ = 8.03 µs. Substituting values in Eq. 4, the analytical impact force is 29.02 kN
and the pressure as 1.161 GPa. The peak force in this SPH simulation was 27.84 kN which is 4.06%
lower than the analytical value. The pressure from the SPH method is calculated as 1.11 GPa. Thus,
there is 2.4% difference when comparing the peak force with the Lagrangian simulation to the
analytical solution. The Lagrangian model produced an impact force is 27.65kN and the pressure
1.106 GPa [1]. The values obtained with the SPH model are within 3% with those obtained using
the Lagrangian model.
Figure 6: SPH simulation of traverse beam impact.
4. BirdStrike Impact Problem
The beam centered impact problem was based on rigid body impact in which the analytical
load computation is relatively easily taking. The results obtained from this example provided us
confidence in the methods being used and thus we proceeded to analyze the bird-strike impact
problem. Although the bird-strike event may occur in different parts of an aircraft, the scope of
this work is to study bird-strike against fan-blades. Figure 8 shows the damage caused by bird
impact on the turbine fan blades. This only shows us that this problem is crucial and that by
predicting the impact pressure will help us design better fan blades. Furthermore, a fan blade is
composed of both flat and tapered sections. Thus, we focus our attention on analyzing bird-strikes
against flat and tapered plate using the SPH formulation in LS-DYNA. We use the work by
Barber et al. [7] as a mean of comparison. The results within 10% would be acceptable since the
actual testing model is not available.
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10. 4.1 Preprocessing
In order to achieve a fair comparison with the Lagrange simulations and test data, we kept the
same bird properties as in the Lagrangian case [1]. Because the SPH model is represented by a
group of elements or small spheres, and is not continuous along the whole space they are
occupying, it is necessary to calculate the physical properties for each element by taking into
account that each element should have the same bird density. It is also important to highlight that
the sum of masses of all small elements or spheres must be equal to the mass of the bird. The rigid
and tapered plates used for the SPH model have the same dimensions and properties as in the case
of the Lagrangian simulation.
Figure 7: Impact force for the SPH simulation.
Figure 8: Damage caused by bird-strikes.
4.1.1 BirdModel
How to model a bird is quite challenging and a model that best meets the testing bird properties
must be used. The model considered in this work is that of a cylinder, as suggested by Bowman and
Frank [15]. It has been shown that this model of bird produce close results to real birds. In
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Vijay K. Goyal, Carlos A. Huertas, and Thomas J. Vasko
11. addition, the bird model is assumed isotropic, symmetric and homogeneous. An approximate
aspect ratio (L/D) of 2.03 was used for our bird model. The dimensions vary depending on the
mass of the bird, and are selected from the test data by Barber et al. [7]. The material properties of
the bird were similar to a gelatin material with 90% water and 10% air mixture.
Figure 9: SPH Element generation for the bird model.
To model the bird, first a square mesh with equivalent sides to the pre-calculated diameter are
constructed, and then extruded to a length with different number of subdivisions, as seen in Figure
9(a). The elements located in the square mesh are eliminated to approximate the mesh shape to
that of the circular (cylindrical) mesh used in the Lagrangian simulation, as shown in Figs. 9(b) and
9(c). The remaining nodes are used to calculate the mass and dimensions of each spherical
element, and the SPH particles were constructed in each remaining node (Goyal et al. [16]). The
lumped mass for each SPH element is calculated using the following equation:
(5)
Note that the number of nodes is equal to the number SPH elements. For the shot reproduced the
dimensions of the bird (cylindrical representation) were: D = 41.4431 mm, L = 60 mm, ρ = 912.60
kg/m3, V = 80936.7 mm3, and m = 0.073863 kg. Table 1 summarizes the main properties used for
modeling the bird.
4.1.2 Rigid Flat Plate Target
Here we used two different targets: a rigid flat plate and a deformable tapered plate. The
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12. purpose of using a rigid flat plate target is to compare the simulations with the experimental data
obtained from Barber et al. [7]. Barber et al. [7] used a rigid flat plate for their experiments which
was modeled as a circular rigid plate with dimensions of 1 mm thickness and 15.25 cm of diameter.
The material of the target disk was 4340 steel, with a yield strength of 1035 MPa, Rockwell surface
hardness of C45, modulus of elasticity modulus of 205 GPa, and a Poisson’s ratio of 0.29. These
properties of the material will be used in LS-DYNA to model the flat rigid plate.
Table 1: Properties for the model of bird.
Table 2: Tapered plate properties (fixed at the two shortest sides).
4.1.3 Deformable Tapered Plate Target
The deformable tapered plate target properties were taken from the work by Moffat et al. [9],
which simulated the impacting bird (as a sphere) on a tapered plate using MSC/DYTRAN
software. The properties for the tapered plate are given in Table 2.
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Vijay K. Goyal, Carlos A. Huertas, and Thomas J. Vasko
13. 4.1.4 Test Data for BirdStrike Event
Barber et al. [7] simulated the bird-strike event as a solid cylinder with dimensions that vary
depending on the mass of the bird. The birds used in the tests weigh about 100 grams and are fired
at velocities ranging from 60 to 350 m/s. To achieve a better simulation of the bird-strike event the
densities of the computer simulated bird must be calculated based on the masses of the tests and the
recommended bird cylinder-like computer model.
Figure 10: Graphical representation of Pressure Time oscillograph for shot 4992-B [7].
Here we compared the tendencies on the pressure-load curves of the computer simulations
with experimental data, and determined velocities and densities based on the mass and velocity
quantities of the test data. To have a fair comparison of the results obtained by the bird-strike
simulation using LS-DYNA and the Barber et al. [7] research it is necessary to reproduce as
accurate as possible the results displayed from the pressure transducers recording the impact event.
Because of not having the digital experimental data of the test results to be reproduced, the graphs
presented on Barber’s report are imported into MatLab to obtain approximate readings, which are
later compared with those obtained by LS-DYNA.
Figure 11: Geometric model for the Lagrangian bird and Target shell.
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14. The pressure plots shown in Figure 10 depict the data by Barber et al. [7] in which the loads
generated in the impact are characterized. This is done in an effort to study the loading caused by
this kind of impact in a real aircraft. All the SPH LSDYNA simulations performed in this work
were compared with this test data. It is important to identify the stages in the loading which are
observed by Barber et al. [7].
The first simulation consisted in the bird strike event against solid rigid plates as done by
Barber et al. [7]. The second simulation model was based in the work of Moffat et al. [9],
bird-strikes on tapered plates. All simulations using the SPH model are compared with their
respective available test data and the Lagrangian models (Goyal et al. [1]). Now we proceed to
explain the results obtained by the SPH model using LS-DYNA.
5. Analysis and Results
5.1 Frontal Impact against Rigid Flat Plate
Figure 11 shows the uniform cylindrical representation of the bird used for the Lagrangian
model and the target plate for the frontal impact of the bird. Now, we study the effect of various
contact types for the bird model composed of 8700 SPH particles. The goal is to determine the best
contact type for bird-strike modeling. The final results are compared to those obtained using the
Lagrangian simulation [1].
5.1.1 Parameter Variation for SPH Modeling
Several simulations are performed in which the variables inside the *CONTROL_SPH card,
type of contact and number of SPH particles were changed in order to study their sensitivity on the
impact loads and pressures. For all the contacts, the flat plate was assigned as the master part and
the SPH bird as the slave part.
Here, we explain the variables that affect directly the output data for a bird-strike event
modeled in LS-DYNA using the SPH approach. The two most important parameters that
influenced the desired response are the type of contact between the SPH particles and the target
surface, and the Particle Approximation Theory (keyword: FORM inside the SPH card
*CONTROL_SPH). The contacts used for the simulations performed included only those that
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Vijay K. Goyal, Carlos A. Huertas, and Thomas J. Vasko
15. define contact between the SPH nodes to the surface of the Lagrangian target these types of
contacts are one-way contact types.
Figure 12: Snapshots at different times of deformation of the SPH bird
varying the *FORM parameter.
Figure 13: Deformation of the SPH bird for different time intervals.
The FORM parameter (Particle Approximation Theory parameter) inside the *CONTROL
SPH card can be changed and set to FORM=1 (remoralization approximation). This generates a
deformation similar to that predicted by Wilbeck and Barber [7] of the impacting cylinder reducing
the effect of bouncing of the particles when entering in contact with the target. By changing this
parameter, a bounce-off effect is produced and thus it affects the interaction of the upcoming
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16. particles when entering in contact with the target and the particles already in contact with it. Figure
12 illustrates the interaction for *CONTACT AUTOMATIC NODE TO SURFACE ID with
FORM=0 and FORM=1.
With FORM=1 the particles best represent the bird-strike event.
However, the maximum force obtained for FORM=1 is 0.048 MN which differs from the 0.0581
MN of the Lagrange simulation with a 17.38% of difference.
The variable NCBS (Number of Cycles Between particle Sorting) of the *CONTROL SPH
card is varied between 2 and 5. The same force at the interface surface is used for each value for the
NCBS variable. Figure 13 shows the deformation at different time intervals for the case when
NCBS is 2 and 5. The final deformation is in good agreement to that predicted by Wilbeck and
Barber [7]. There is no difference between the resultant force at the interface of the SPH bird and
the Shell Target and have a peak value of 5.4 kN. Thus, NCBS is a nonaffecting variable in the
simulation. The contact used for this simulation was *CONTACT CONSTRAINT NODE TO
SURFACE contact type.
5.1.2 Different Material NULL Models
Many cases where ran using Material_NULL. The maximum force obtained was higher than
400% when compared with the 0.0581 MN peak force obtained using the standard Lagrangian case
for the same contact type. Now we use a solid transducer in the center of the target to measure the
pressure in that region. The material of this solid transducer was varied from *MAT_PIECE_
WISE_LINEAR_PLASTICITY to *MAT_RIGID. The contact used was *CONTACT_
CONSTRAINED_NODE_TO_SURFACE.
The behavior of the deformation of the bird
resembles the one predicted by Barber et al. (1975). This simulation did not provide acceptable
results and thus is not recommended.
Figure 14: Deformation of the SPH bird at different time intervals using a transducer.
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Vijay K. Goyal, Carlos A. Huertas, and Thomas J. Vasko
17. Figure 15: Top view of the impact of the SPH particles against the transducer.
Table 3: Peak impact Pressure comparison between SPH and Lagrangian simulations.
For this simulation, we used *MAT_NULL and *CONTACT_CONSTRAINT_NODE_TO_
SURFACE. Some solid elements are created in the center of the target to simulate a transducer.
Using the area of these elements the pressure is calculated by dividing the resultant force generated
in the contact between the bird and the transducer over the area of the transducer. Figure 14 shows
the deformed SPH bird at different time intervals. Figure 15 shows the top view of the SPH
particles impacting the simulated transducer. Approximately 81 columns of SPH particles
impacted the transducer which is higher to the previous simulations. The peak force obtained in
this case was 0.0054 MN. Then, dividing this value over 144 mm2 the pressure for this simulation
was 37.23 MPa (5409.7 psi) which was 7.05% lower than the 40 MPa (5801.2 psi) measured by
Barber et al. for shot 5126A. The pressure comparison for different SPH simulation with test data
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18. and the Lagrangian case is shown in Table 3. Thus, for a constant contact for the simulations
performed when the number of SPH particles was increased, the maximum pressure value obtained
from the simulation also increased. All the pressures were calculated using the approximate area
measured at the time in which the peak force occurs for each simulation.
Figure 16: SPH simulations of shot 5126 A for different number of particles.
Figure 16 shows different deformation plots for SPH simulations using different number of
particles in the model. As explained, this variation in number is considered in order to study its
influence in the stability of the model, in the deformation and in the resultant force plot along the
whole simulation. The simulation obtained with 2464 particles was unstable, which could be
caused by the non-uniform distribution of the particles across the entire model of the bird. All the
other models were constructed with a more uniform distribution of the particles and with a distance
between adjacent particles almost constant. These models produced deformations close to
experimental data. Models with 4700, 8700 and 22,000 SPH particles showed deformation with a
sliding behavior in the steady phase of the impact. In contrast, models using 5000 and 10000 SPH
particles presented bouncing of the particles in the steady phase of the bird-strike. However this
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Vijay K. Goyal, Carlos A. Huertas, and Thomas J. Vasko
19. bouncing effect is more affected by the type of contact used than for the amount of SPH particles
used for the creation of the model, as shown in Figure 17.
Figure 17: Peak force for SPH simulations of shot 5126 A.
Figure 18: Comparison of peak pressure obtained in Lagrangian and SPH simulation using the
nodes to surface contact TEROD=1.1.
Figure 18 shows that the *CONTACT_ERODING_NODE_TO_SURFACE and the in the
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20. *CONTACT_NODE_TO_SURFACE simulation with 8,700 particles have a peak pressure close
to the peak pressure obtained in the Lagrangian simulation. These contact types are then one of the
indicated to be used in SPH simulation of bird-strike because of its capability of reproduce the
loads in the impact close to the Lagrange model and to the test data.
Using the results obtained it is observed that the mesh density affects the simulation.
Simulated transducers make possible getting the pressure distribution graph. When two different
mesh resolutions are used, the results are more accurate with respect to the maximum pressure
obtained.
5.2 Impact for a Tapered Plate (Impact at 0 deg)
Using the previous framework, we considered two different bird impact angles: 0 and 30
degrees. The dimension and properties of the tapered plate are identical to those of previous
simulations. The number of SPH particles created for this simulation was 26195 and its distribution
was arranged to form the cylinder.
Figure 19: Result of the interaction for the SPH simulation of the tapered plate impact using
material NULL.
Table 4: Peak force comparison for various SPH tapered plate impact at 0 degrees.
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21. When using Material NULL, little or no interaction between the tapered plate and the bird is
observed, suggesting that the bird is sliced in two parts. This is the same behavior observed in the
Lagrangian approach. Only few particles are involved in the impact for the SPH simulation. The
results for the 0 degrees of impact simulation show that there is an only slight deformation in the
tapered plate. Figure 19 shows that the particles aligned with the plate were the ones suffering
deflection while the other particles continued their trajectory.
When using elastic fluid material, there was interaction of the plate and the bird, but as the
impact is a 0 degrees the plate slices the bird in two parts. This occurs because the bird impacts at
the narrowest side of the plate. Figure 19 shows that the maximum peak force computed for this
case was 0.001694 MN. This force is 88.66% lower than the computed for the Lagrangian case.
One reason for this is that the elastic fluid accounts for the deviatoric stresses, computing the
stresses that cause deformation in the solid elements of the bird. The impact energy therefore will
be absorbed for the material of the bird, decreasing the force generated in the impact. Table 4 lists
the peak forces obtained for the Lagrange and SPH simulations of the bird-strike on tapered plates
impacting at an angle of 0 degrees. The simulation that best converges to the Lagrangian case is
the SPH simulation using the material null for a SPH model with 26,000 particles.
Figure 20: Result of the interaction for the SPH simulation of the tapered plate.
5.3 Impact for a Tapered Plate (Impact at 30 deg)
Now we explain the simulation of a cylindrical bird impacting a tapered plate along the
thinnest side. The deflection of the leading edge and the loads generated in the impact were
computed for LS-DYNA. The type of material was the *MAT_NULL. Figure 21 shows the
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22. deformation of the tapered plate at different times of the simulation. In this case, the maximum
normal deflection was 1.12 inches which was 6.96% higher than the value obtained by Moffat et al.
[9]. The maximum value of the force had a value of 0.049 MN, 13.46% lower than the 0.0566 MN
in the Lagrange simulation of the same impact which shows that a good convergence both for force
and deflection occurs in this simulation.
Figure 21: Deformation of the tapered plate using material null using SPH model.
Table 5: Maximum normal deflection for a bird impacting a tapered plate at 30°.
Other cases where also ran and results are enclosed in Table 5. Thus, the simulation that has
better convergence to the maximum deflection found by Moffat is the SPH simulation using
material null and 26,000 particles. In addition, for this model the peak force obtained was only
13.4% different from the one calculated using the Lagrange simulation with material elastic fluid.
But if the peak force is compared with the Lagrangian case using the same null material the error is
8.93%. However, changing the material in the SPH simulation to the material elastic fluid does not
result in a convergence of the force to the Lagrangian model using the same elastic fluid material.
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23. 6. Final Remarks
After studying the influence of various parameters involved in the SPH bird model, we
compared the peak pressure and we are ready to make some recommendation on when is it best to
use this approach. First and foremost, the SPH bird model is far more complex than the Lagrangian
bird model and the number of variables influencing the SPH model is higher than for the
Lagrangian one. For the SPH bird model, the mesh density or number of particles included has a
strong influence in the peak impact pressure. This causes the selection of an optimum number of
particles before beginning further simulations.
For the first case, the frontal impact against a flat rigid plate, a bird model with 8700 particles
with one-way constraint contact type and a null material type can be used. The error obtained in the
pressure after comparing with the experimental data is within 10%. For the Lagrangian model the
error when using elastic fluid material and an eroding contact type produced and error of 9%.
Therefore, the SPH model can successfully be used in this kind of frontal impacts.
For the second case, 0 and 30 degrees impact against a tapered plate, the SPH model validates
the results obtained in the literature. The SPH model is recommended over the Lagrangian model
for angled impacts on tapered plates since the error of the maximum normal deflection in less than
7% when compared with the experimental data available in literature. These results are validated
using 26,000 SPH particles, a eroding contact type and a null material. For the 0 degree impact,
neither the Lagrangian nor the SPH provide any significant deformation. Results show very little
interaction between the bird and the tapered plate because the bird is being sliced in two parts,
being the null material the best approximation when using SPH.
Based on the results, the SPH method can be considered as a good alternative to simulate
bird-strike events although it is more complex in the model creation.
7. Acknowledgments
This work was performed under the grant number 24108 from the United Technologies Co.,
*Corresponding author (V. Goyal), Tel.: 1-787-832-4040 Ext. 2111; E-mail:
2013. American Transactions on Engineering & Applied Sciences.
vijay.goyal@upr.edu.
Volume 2 No. 2
ISSN 2229-1652 eISSN 2229-1660
Online Available at
http://TuEngr.com/ATEAS/V02/083-107.pdf
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24. Pratt & Whitney. The authors gratefully acknowledge the grant monitors for providing the
necessary computational resources and support for this work. The research presented herein is an
extension of the work presented at the 47th AIAA/ASME/ACE/AHS/ASC SDM Conference,
Rhode Island, May 2006, AIAA.
8. References
[1] V. K. Goyal, C. A. Huertas, T. J. Vasko, 2013. Bird-Strike Modeling Based on the Lagrangian
Formulation Using LS-DYNA. Am. Trans. Eng. Appl. Sci. 2(2): 057-081. Available at:
http://TuEngr.com/ATEAS/V02/057-081.pdf. Accessed: March 2013.
[2] J. Metrisin, B. Potter, Simulating Bird Strike Damage in Jet Engines, ANSYS Solutions 3 (4)
(2001) 8–9.
[3] E. Parkes, “The permanent deformation of a cantilever strucks transversely at its tip”, in:
Proceedings Roy. Soc. Lond., England, 1995.
[4] W. J. Stronge, T. Yu, Dynamic Models for Structural Plasticity, Springer-Verlag, London,
Great Britain, 1993.
[5] W. Goldsmith, IMPACT: The Theory and Phisical Behaviour of Colliding Solids, Dover
Publications, Mineola, New York, 2001.
[6] B. N. Cassenti, Hugoniot Pressure Loading in Soft Body Impacts.
[7] J. P. Barber, H. R. Taylor, J. S. Wilbeck, “Characterization of Bird Impacts on a Rigid Plate:
Part 1”, Technical report AFFDL-TR-75-5, Air Force Flight Dynamics Laboratory,
Wright-Patterson Air Force Base, OH (1975).
[8] E. Niering, Simulation of Bird Strikes on Turbine Engines.
[9] W. Moffat, Timothy J. and Cleghorn, “Prediction of Bird Impact Pressures and Damage Using
MSC/DYTRAN”, in: Proceedings of ASME TURBOEXPO, Louisiana, 2001.
[10] N. F. Martin, Nonlinear Finite Element Analysis to Predict Fan Blade Impact Damage.
[11] J. Lacome, “Smooth Particle Hydrodynamics (SPH): A New Feature in LS-DYNA”, in:
Proceedings of the 6th International LS-DYNA Users Conference, 2000.
[12] J. Lacome, Smooth Particle Hydrodynamics-Part II (2001) 6–11.
[13] L. H. Hut, P., G. Lake, S. M. J. Makino, T. Sterling, “Smooth Particle Hydrodynamics:
Models, Applications, and Enabling Technologies”, in: Proceedings form the Workshop
Presented by the Institute for Advance Study, Princeton., 1997.
[14] V. K. a. C. A. H. Goyal, “Robust Bird-Strike Modeling Using LS-DYNA”, in: Proceeding of
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Vijay K. Goyal, Carlos A. Huertas, and Thomas J. Vasko
25. the 23th Southeastern Conference on Theoretical and Applied Mechanics Conference,
Mayaguez, Puerto Rico., 2006.
[15] D. R. Bowman, G. J. Frank, “IBRG ARTIFICIAL BIRD PROJECT”, Work programmed and
Schedule, United Kingdom (2000).
Dr. V. Goyal is an associate professor committed to develop a strong sponsored research program for
aerospace, automotive, biomechanical and naval structures by advancing modern computational
methods and creating new ones, establishing state-of-the-art testing laboratories, and teaching
courses for undergraduate and graduate programs. Dr. Goyal, US citizen and fully bilingual in both
English and Spanish, has over 17 years of experience in advanced computational methods applied to
structures. He has over 15 technical publications with another three in the pipeline, author of two
books (Aircraft Structures for Engineers and Finite Element Analysis) and has been recipient of
several research grants from Lockheed Martin Co., ONR, and Pratt & Whitney.
C. Huertas completed his master’s degree at University of Puerto Rico at Mayagüez in 2006.
Currently, his is back to his home town in Peru working as an engineer.
Dr. Thomas J. Vasko, Assistant Professor, joined the Department of Engineering at Central
Connecticut State University in the fall 2008 semester after 31 years with United Technologies
Corporation (UTC), where he was a Pratt & Whitney Fellow in Computational Structural
Mechanics. While at UTC, Vasko held adjunct instructor faculty positions at the University of
Hartford and RPI Groton. He holds a Ph.D. in M.E. from the University of Connecticut, an M.S.M.E.
from RPI, and a B.S.M.E. from Lehigh University. He is a licensed Professional Engineer in
Connecticut and he is on the Board of Directors of the Connecticut Society of Professional Engineers
Peer Review: This article has been internationally peer-reviewed and accepted for
publication according to the guidelines given at the journal’s website.
*Corresponding author (V. Goyal), Tel.: 1-787-832-4040 Ext. 2111; E-mail:
2013. American Transactions on Engineering & Applied Sciences.
vijay.goyal@upr.edu.
Volume 2 No. 2
ISSN 2229-1652 eISSN 2229-1660
Online Available at
http://TuEngr.com/ATEAS/V02/083-107.pdf
107