This document summarizes a study investigating the role of bulkheads and crack stopper straps in the fail-safe design of aircraft fuselages. A finite element analysis was conducted to model a section of fuselage containing longitudinal stiffeners, a bulkhead, and crack stopper straps. Stress intensity factors were calculated with and without the crack stopper straps to determine their effectiveness in arresting cracks. The analysis found that the crack stopper straps reduced stress intensity at the crack tip, improving the structure's ability to arrest cracks before they propagate catastrophically. This demonstrates the importance of bulkheads and crack stopper straps in achieving the damage tolerance designed to safely sustain cracks in aircraft fuselages.
Review of Fault Detection in Rolling Element BearingAM Publications
Defective bearings are the source of vibrations in machines. Due to constructional features of bearing, they generate
vibrations. As the condition of bearings changes during use, the nature of vibrations also changes and it has a definite
characteristics depending upon the cause. This characteristic feature of bearing makes them suitable for vibration
monitoring. This is a review paper for fault detection technique in rolling element bearing, it covers rolling element
bearing components and its geometry, bearing failure modes, bearing condition monitoring techniques, time domain
and frequency domain techniques.
Structural and Vibration Analysis of a Machine Shaft using Finite Element Ana...ijtsrd
The present study is a simulation of a machine shaft. The study will be done on FEM simulation software called Ansys 14.5, where a modal would be developed which will undergo a process of meshing. Meshing will divide the modal in extremely small units without changing the shape of actual geometry which will help the software to study the change at every small unit of the model. Then the of the modal would be defined in terms of inlet and outlet thereafter the boundary condition and design equation would be applied to get the desired result. Syed Minal Hussian Jafri | Prof Amit Kaimkuriya ""Structural and Vibration Analysis of a Machine Shaft using Finite Element Analysis"" 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/ijtsrd23844.pdf
Paper URL: https://www.ijtsrd.com/engineering/mechanical-engineering/23844/structural-and-vibration-analysis-of-a-machine-shaft-using-finite-element-analysis/syed-minal-hussian-jafri
INTERFACIAL STRESS ANALYSIS OF EXTERNALLY PLATED RC BEAMSIjripublishers Ijri
Strengthening reinforced concrete (RC) beams by bonding steel or fibre reinforced polymer (FRP) on its tension face
has become a popular retrofit method due to its rapid, simple and other advantages. However, debonding along the
Steel-RC beam interface can lead to premature failure of the structures. The interfacial stresses play a significant role
in understanding this premature debonding failure of such repaired structures. This paper presents a careful finite
element investigation into interfacial stresses in the adhesive layer bonding RC beam and soffit plate. Finite element
modelling issues like proper selection of contact between adherents and symmetry conditions are first
discussed, with particular attention on appropriate finite element meshes for the accurate determination of interfacial
stresses. The interfacial stress behaviour at plate end has been analysed for two cases of loading taken one by applying
uniformly distributed load and the other with a two point loading. Two special cases are considered in two point
loading – for the cases when the plate terminates with-in the constant moment region (CMR) and for the case when
plate is extended beyond constant moment region where bending moment is minimal. The interfacial stresses are
increasing with a reduction in adhesive layer thickness where as the stresses are increasing with the increase in soffit
plate thickness. Carbon fibre reinforced polymer (CFRP) has shown a significant reduction in interfacial stresses
when compared to steel plate. The interfacial stresses for the plate restricted within the constant moment region are very
high near the plate end leading to flexural debonding compared to the case where plate is extended beyond constant
moment region where bending moment is minimal. The concentration of stresses in the adhesive layer near the plate
end explained the significance in considering their influence in flexural debonding.
Keywords-- Interfacial stresses, flexural debonding, constant moment region, soffit plate, finite element method.
Biomechanical Investigation of Plate Working Length on Fatigue Characteristics of Locking Plate Constructs in Human Cadaveric Distal Metaphyseal Femoral Fracture Models
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.
Review of Fault Detection in Rolling Element BearingAM Publications
Defective bearings are the source of vibrations in machines. Due to constructional features of bearing, they generate
vibrations. As the condition of bearings changes during use, the nature of vibrations also changes and it has a definite
characteristics depending upon the cause. This characteristic feature of bearing makes them suitable for vibration
monitoring. This is a review paper for fault detection technique in rolling element bearing, it covers rolling element
bearing components and its geometry, bearing failure modes, bearing condition monitoring techniques, time domain
and frequency domain techniques.
Structural and Vibration Analysis of a Machine Shaft using Finite Element Ana...ijtsrd
The present study is a simulation of a machine shaft. The study will be done on FEM simulation software called Ansys 14.5, where a modal would be developed which will undergo a process of meshing. Meshing will divide the modal in extremely small units without changing the shape of actual geometry which will help the software to study the change at every small unit of the model. Then the of the modal would be defined in terms of inlet and outlet thereafter the boundary condition and design equation would be applied to get the desired result. Syed Minal Hussian Jafri | Prof Amit Kaimkuriya ""Structural and Vibration Analysis of a Machine Shaft using Finite Element Analysis"" 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/ijtsrd23844.pdf
Paper URL: https://www.ijtsrd.com/engineering/mechanical-engineering/23844/structural-and-vibration-analysis-of-a-machine-shaft-using-finite-element-analysis/syed-minal-hussian-jafri
INTERFACIAL STRESS ANALYSIS OF EXTERNALLY PLATED RC BEAMSIjripublishers Ijri
Strengthening reinforced concrete (RC) beams by bonding steel or fibre reinforced polymer (FRP) on its tension face
has become a popular retrofit method due to its rapid, simple and other advantages. However, debonding along the
Steel-RC beam interface can lead to premature failure of the structures. The interfacial stresses play a significant role
in understanding this premature debonding failure of such repaired structures. This paper presents a careful finite
element investigation into interfacial stresses in the adhesive layer bonding RC beam and soffit plate. Finite element
modelling issues like proper selection of contact between adherents and symmetry conditions are first
discussed, with particular attention on appropriate finite element meshes for the accurate determination of interfacial
stresses. The interfacial stress behaviour at plate end has been analysed for two cases of loading taken one by applying
uniformly distributed load and the other with a two point loading. Two special cases are considered in two point
loading – for the cases when the plate terminates with-in the constant moment region (CMR) and for the case when
plate is extended beyond constant moment region where bending moment is minimal. The interfacial stresses are
increasing with a reduction in adhesive layer thickness where as the stresses are increasing with the increase in soffit
plate thickness. Carbon fibre reinforced polymer (CFRP) has shown a significant reduction in interfacial stresses
when compared to steel plate. The interfacial stresses for the plate restricted within the constant moment region are very
high near the plate end leading to flexural debonding compared to the case where plate is extended beyond constant
moment region where bending moment is minimal. The concentration of stresses in the adhesive layer near the plate
end explained the significance in considering their influence in flexural debonding.
Keywords-- Interfacial stresses, flexural debonding, constant moment region, soffit plate, finite element method.
Biomechanical Investigation of Plate Working Length on Fatigue Characteristics of Locking Plate Constructs in Human Cadaveric Distal Metaphyseal Femoral Fracture Models
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.
A Review of FDM Based Parts to Act as Rapid ToolingIJMER
Fused Deposition Modeling (FDM) is one from basic Rapid Prototyping (RP) technologies
used in technical practice. In this contribution are presented basic information about parameters such
as layer thickness, part build orientation, raster angle, raster width and air gap. This study provides
insight into complex dependency of strength on process parameters. In this paper microphotographs
are used to show the mechanism of failure. The major reason for weak strength is attributed to
distortion within or between the layers.Developing a curved layer deposition methodology can
improve part quality by reduced lamination, reduction in the staircase effect which leads to improved
dimensional accuracy of the part. Less effort has been made to increase the range of FDM materials
to include metals or metal based composites with the help of metal based composite direct rapid
tooling will allow fabrication of injection moulding dies and inserts with desired thermal and
mechanical properties suitable for using directly in injection moulding machines for short term or
long term production runs
If you are on the search for specialized rug cleaners for your rugs in New York City, it is recommended that once check the background of the company before one seeks their services. It is an added benefit provided that the professional cleaners have adequate experience in cleaning services.
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
An Experimental Analysis of Performance, Combustion and Emission Characteris...IJMER
The use of biodiesel, the methyl esters of vegetable oils are becoming popular due to their
low environmental impact and potential as a green alternative fuel for diesel engine. With this objective,
the present work has focused on the performance and emission characteristics of diesel engine using
rice bran oil and its blends with diesel. In this investigation, the blends of varying proportions of rice
bran biodiesel with diesel (RB20, RB40, RB60, RB80 & RB100) were prepared, analyzed, and compared
the performance and exhaust emission with diesel using 5.2 kW Single cylinder, 4stroke diesel engine.
The performance and emission characteristics of blends are evaluated at variable loads and constant
rated speed of 1500 rpm and found that the performance of RB20 blend of rice bran oil gives result, that
is near to the diesel and also found that the emission CO, CO2, HC, smoke & NOX of this blend is less
than the diesel.
Zigbee Based Wireless Sensor Networks for Smart CampusIJMER
A network which connects a bunch of distributed low-power sensor nodes together, with each node dedicated to a predefined operation can be visualized as a Wireless Sensor Network (WSN).
A Unique Application to Reserve Doctor Appointment by Using Wireless Applicat...IJMER
WAP is a standardized technology for cross-platform, distributed computing, very similar to the Internet’s combination of Hypertext Markup Language (HTML) and Hypertext Transfer Protocol (HTTP). WAP could be described as a set of protocols that has inherited its characteristics and functionality from Internet standards and from standards developed for wireless services by some of the world’s leading companies in the business of wireless telecommunications. This application will help patients, the normal doctor and the medical director. The patient can reserve an appointment. The normal doctor can view and print the lists of patient appointment under his responsibility. The medical director can add new departments, add new doctors, and also can change the password to access the database. He can also modify data and working schedules of doctors assigned. He can add new patients and can have privilege access to transfer any patient appointment to another doctor. This Application which has been developed by using WAP was the first of its kind here, where software has been developed.
Dynamic Organization of User Historical QueriesIJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Comparative study on Garments dyeing process and Fabric dyeing process on var...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Design, Analysis and Testing of Wing Spar for Optimum WeightRSIS International
Aircraft is a complex mechanical structure with flying capability. The structure of an airframe represents one of the finest examples of a minimum weight design in the field of structural engineering. Surprisingly such an efficient design is achieved by the use of simple “strength-of-material” approach. Aircraft has two major components, which are fuselage and wing. For a wing of an aircraft the primary load carrying ability is required in bending. A typical aluminium material 6082-T6 is chosen for the design. A four-Seater aircraft wing spar design is considered in the current study. Wings of the aircraft are normally attached to the fuselage at the root of the wing. This makes the wing spar beam to behave almost like a cantilever beam. Minimum two spars are considered in the wing design. In a conventional beam design approach one will end up in heavy weight for the spar of the wing. In the current project the spar is considered as a beam with discrete loads at different stations. The design is carried out as per the external bending moment at each station. A finite element approach is used to calculate the stresses developed at each station for a given bending moment. Several stress analysis iterations are carried out for design optimization of the spar beam. Linear static analysis is used for the stress analysis. The spar beam is designed to yield at the design limit load. Weight optimization of the spar will be carried out by introducing lightening cut-outs in the web region. The results from the conventional design approach and the optimized design are compared. Weight saving through the design optimization is calculated. Spar will be a built-up structure. A scale-down model of the spar will be fabricated using aluminium alloy 6082-T6 material. Static testing of the spar will be carried out to validate the design and stress analysis results.
A Review of FDM Based Parts to Act as Rapid ToolingIJMER
Fused Deposition Modeling (FDM) is one from basic Rapid Prototyping (RP) technologies
used in technical practice. In this contribution are presented basic information about parameters such
as layer thickness, part build orientation, raster angle, raster width and air gap. This study provides
insight into complex dependency of strength on process parameters. In this paper microphotographs
are used to show the mechanism of failure. The major reason for weak strength is attributed to
distortion within or between the layers.Developing a curved layer deposition methodology can
improve part quality by reduced lamination, reduction in the staircase effect which leads to improved
dimensional accuracy of the part. Less effort has been made to increase the range of FDM materials
to include metals or metal based composites with the help of metal based composite direct rapid
tooling will allow fabrication of injection moulding dies and inserts with desired thermal and
mechanical properties suitable for using directly in injection moulding machines for short term or
long term production runs
If you are on the search for specialized rug cleaners for your rugs in New York City, it is recommended that once check the background of the company before one seeks their services. It is an added benefit provided that the professional cleaners have adequate experience in cleaning services.
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
An Experimental Analysis of Performance, Combustion and Emission Characteris...IJMER
The use of biodiesel, the methyl esters of vegetable oils are becoming popular due to their
low environmental impact and potential as a green alternative fuel for diesel engine. With this objective,
the present work has focused on the performance and emission characteristics of diesel engine using
rice bran oil and its blends with diesel. In this investigation, the blends of varying proportions of rice
bran biodiesel with diesel (RB20, RB40, RB60, RB80 & RB100) were prepared, analyzed, and compared
the performance and exhaust emission with diesel using 5.2 kW Single cylinder, 4stroke diesel engine.
The performance and emission characteristics of blends are evaluated at variable loads and constant
rated speed of 1500 rpm and found that the performance of RB20 blend of rice bran oil gives result, that
is near to the diesel and also found that the emission CO, CO2, HC, smoke & NOX of this blend is less
than the diesel.
Zigbee Based Wireless Sensor Networks for Smart CampusIJMER
A network which connects a bunch of distributed low-power sensor nodes together, with each node dedicated to a predefined operation can be visualized as a Wireless Sensor Network (WSN).
A Unique Application to Reserve Doctor Appointment by Using Wireless Applicat...IJMER
WAP is a standardized technology for cross-platform, distributed computing, very similar to the Internet’s combination of Hypertext Markup Language (HTML) and Hypertext Transfer Protocol (HTTP). WAP could be described as a set of protocols that has inherited its characteristics and functionality from Internet standards and from standards developed for wireless services by some of the world’s leading companies in the business of wireless telecommunications. This application will help patients, the normal doctor and the medical director. The patient can reserve an appointment. The normal doctor can view and print the lists of patient appointment under his responsibility. The medical director can add new departments, add new doctors, and also can change the password to access the database. He can also modify data and working schedules of doctors assigned. He can add new patients and can have privilege access to transfer any patient appointment to another doctor. This Application which has been developed by using WAP was the first of its kind here, where software has been developed.
Dynamic Organization of User Historical QueriesIJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Comparative study on Garments dyeing process and Fabric dyeing process on var...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Design, Analysis and Testing of Wing Spar for Optimum WeightRSIS International
Aircraft is a complex mechanical structure with flying capability. The structure of an airframe represents one of the finest examples of a minimum weight design in the field of structural engineering. Surprisingly such an efficient design is achieved by the use of simple “strength-of-material” approach. Aircraft has two major components, which are fuselage and wing. For a wing of an aircraft the primary load carrying ability is required in bending. A typical aluminium material 6082-T6 is chosen for the design. A four-Seater aircraft wing spar design is considered in the current study. Wings of the aircraft are normally attached to the fuselage at the root of the wing. This makes the wing spar beam to behave almost like a cantilever beam. Minimum two spars are considered in the wing design. In a conventional beam design approach one will end up in heavy weight for the spar of the wing. In the current project the spar is considered as a beam with discrete loads at different stations. The design is carried out as per the external bending moment at each station. A finite element approach is used to calculate the stresses developed at each station for a given bending moment. Several stress analysis iterations are carried out for design optimization of the spar beam. Linear static analysis is used for the stress analysis. The spar beam is designed to yield at the design limit load. Weight optimization of the spar will be carried out by introducing lightening cut-outs in the web region. The results from the conventional design approach and the optimized design are compared. Weight saving through the design optimization is calculated. Spar will be a built-up structure. A scale-down model of the spar will be fabricated using aluminium alloy 6082-T6 material. Static testing of the spar will be carried out to validate the design and stress analysis results.
Fatigue life estimation of rear fuselage structure of an aircrafteSAT Journals
Abstract Integrity of the airframe structure is achieved through rigorous design calculations, stress analysis and structural testing. Finite element method (FEM) is widely used for stress analysis of structural components. Each component in the airframe becomes critical based on the load distribution, which in-turn depends on the attitude of the aircraft during flight. Fuselage and wing are the two major components in the airframe structure. The current study includes a portion of the fuselage structure. Empennage is the rear portion of the aircraft, which consists of rear fuselage, Horizontal tail and vertical tail. The air loads acting on the HT also get transferred to rear portion of the fuselage. First step in ensuring the safety of the structure is the identification of critical locations for crack initiation. This can be achieved through detailed stress analysis of the airframe In this project one of the major stress concentration areas in the fuselage is considered for the analysis. Rear fuselage portion with a cargo door cutout region will be analysed. The structure considered for the stress analysis consists of skin, bulkheads and longerons, which are connected to each other through rivets. Aerodynamic load acting on the aircraft components is a distributed load. Depending on the mass distribution of the fuselage structure the inertia forces will vary along the length of the fuselage. The inertia force distribution makes the fuselage to bend about wing axis. During upward bending, bottom portion of the fuselage will experience tensile stress. A cutout region in the tensile stress field will experience high stress due to concentration effect. These high stress regions will be probable fatigue crack initiation locations in the current work, fatigue damage calculation will be carried out to estimate the fatigue life of the structure under the fluctuating loads experienced during flight. Miner’s rule will be adopted for fatigue damage calculation. Keywords: Transport aircraft, Rear fuselage, Cargo door, Finite element method, Stress concentration, Fatigue damage, Miner’ rule
Studies on Strength Evaluation of Fiber Reinforced Plastic CompositesIJERA Editor
Fiber Reinforced Polymer (FRP) composites are extensively used for primary structural components such as wing, empennage and fuselage; and sub-structures such as wing ribs and intermediate spars in new generation aircraft as they give rise to high stiffness and strength to weight ratio. The failure load predictions of such composites are extremely important in order to ascertain the flight safety during its service periods. The stress analysis is a part of failure prediction process, since the failure criterion, in order to predict failure load, requires information about stresses and strains in a structure. In the present investigation, the stress analyses of CFRP composite laminates with and without cut-outs have been carried out by using both analytical and finite element approaches. In analytical approach, a mat lab code has been developed for a flat panel using Classical Laminated Plate Theory (CLPT) and different composite failure theories. MSC.NASTRAN finite element analysis code is used for carrying out finite element analysis. Convergence study has been carried out for the flat composite panel in order to ascertain the best mesh size. Comparison of stress and strain values obtained from both analytical and finite element methods shows that they are in good agreement for flat panel. This further validates the best mesh sizes obtained from the convergence study. This similar mesh sizes are further considered for flat panel with circular and elliptical cut-outs with some mesh refinements around the cut-out regions. Failure load of the flat composite laminate (without cut-out) is determined using four different failure criteria such as maximum stress, maximum strain, Tsai-Hill and Tsai-Wu criteria. The predicted values are compared with experimental results. It is found that the most appropriate theory is Tsai-Wu failure criterion, since the predicted value based on this theory is very closure to experimental failure loads. This theory is used further for predicting the failure loads of composite laminates with cut-outs. The average value of stresses in each lamina has been used for determining the failure indices of the lamina for such cases. The results are compared with experimental failure loads available in the literature. The comparison shows that they are in very good agreement. Tsai-Wu failure criterion best predicts the failure load of a composite laminate with and without cut-outs.
FE Based Crash Simulation of Belly Landing of a Light Transport AircraftRSIS International
Crash survivability is one of the key features to be
attended during the design of an airworthy aircraft. Belly/crash
landing is the most common phenomenon to be considered in
developing a crashworthy product. That makes it essential to
have redundant structure to enhance the safety of occupants and
also limit the damage to easily repairable state in case of such
event. Even from the certification point of view, it is necessary to
investigate this event by test/analysis. Recent development of
advance computing and their capability to simulate such
phenomenon to acceptable accuracy under given conditions
conveniently replace the need for test which is otherwise costly.
At the same time, one has to be cautious while selecting the
modeling parameters to simulate the condition near to reality.
Taking advantage of this feature an effort is made to simulate the
belly landing and its consequences on the structure complying to
the guidelines of the federal aviation regulations. This paper
presents the methodology adopted to successfully simulate the
belly landing phenomenon for a light transport aircraft flying
prototype.
Abstract Cylindrical pressure vessels are widely used for commercial, under water vehicles and in aerospace applications. At present the outer shells of the pressure vessels are made up of conventional metals like steels and aluminum alloys. The payload performance/ speed/ operating range depends upon the weight. The lower the weight the better the performance, one way of reducing the weight is by reducing the weight of the shell structure. The use of composite materials improves the performance of the vessel and offers a significant amount of material savings. Moreover, the stacking sequence is very crucial to the strength of the composite material. This Project involves various objective functions such as stiffness, buckling load and Weight at each level of optimization. Usually composite pressure vessels are designed for minimum mass under strength constraints. A graphical analysis is presented to find optimum fiber orientation for given layer thicknesses. In the present work, an analytical model is developed for the Prediction of the minimum buckling load with / without stiffener composite shell of continuous angle ply laminas (±45°,±55°,±65°,±75°,±85°) for investigation. Comparisons are made for two different approaches i.e. the finite element model and the theoretical model. A 3-D finite element analysis is built using ANSYS-12.0 version software into consideration, for static and buckling analysis on the pressure vessel. Index Terms: Composite material, Shells, Fiber orientation, Layer thickness, Stiffeners, Critical Pressure and Buckling
Optimizationof fuselage shape for better pressurization and drag reductioneSAT Journals
Abstract
The fuselage of any aircraft is essentially to accommodate the payload. It is normally not as streamlined as the wing. Cabin pressurization has been a major concern in the manufacturing of aircrafts. Generally, a cylindrical shape is preferred from a pressurization point of view as it has a higher strength and weighs less too. On the other hand, a sphere is considered as the best pressure vessel among all the shapes, but, sphere being a bluff body is not suitable for carrying payloads. On this note, a cylinder is considered to be better than a sphere to carry the payload and mainly to achieve a streamlined flow. In this paper, the shape chosen is a combination of the sphere and the cylinder to achieve optimum results for pressurization as well as a better streamlined flow. Our prime aim is to convert this bluff body into something more efficient and useful, rather than only for carrying the payload. We have focused basically on two details viz. 1) Better Pressurization and 2) to assist in minimizing the drag, thereby increasing the overall lift of the aircraft and hence increasing the fuel efficiency. The proposed fuselage structure was designed in CATIA V5 software and structural analyses were done in Auto-Desk Multi-Physics software. As a result, a better structural load capacity was found. A load of 10 N/mm2 was applied on both the bodies under consideration (cylinder and ellipse) having the same material, surface area, volume and weight. For the proposed elliptical design, 78% reduction in the minimum stress value and 10% reduction in the maximum stress value were noticed.
Keywords: Fuselage, Lifting Fuselage, Drag Reduction, Pressurization, Hoop Stress, Multi body design, Toroidal Shells, Multi-cylinder, Channel Propeller Configuration, Carbon Fiber, Graphite Fiber, Stabilization and Carbonization.
Determination of Stress Intensity Factor for a Crack Emanating From a Rivet ...IJMER
Modern aircraft structures are designed using a damage tolerance philosophy. This design philosophy envisions sufficient strength and structural integrity of the aircraft to sustain major damage and to avoid catastrophic failure. The rivet holes location are one of the stress concentration region in fuselage skin. The current study includes a curved sheet with rivet holes is considered as part of the
fuselage skin. During the service life of aircraft fatigue cracks will emanate from rivet holes simultaneously as they experience identical stresses due to internal pressure. In fracture mechanics, Stress Intensity Factor (SIF) is an important criterion to evaluate the impact of crack as the magnitude of SIF determines the propagation of crack. The objective is to investigate the SIF for crack emanating from one rivet hole and approaching another using isplacement Extrapolation Method (DEM) in F.E.M that would aid in the determination of the critical nature of such cracks.
MODELING, ANALYZING AND SAFETY ASPECTS OF TORSION AND NOISE EFFECTS ON ROUND ...msejjournal
Each material has its own effect and behavior on external impacts like heat, force, tension, compression,
torsion etc. It is important to study and analyze these behaviors before selecting a material for an
engineering application in the design aspects itself. If predicted values analyzed by both mathematical and
software are available it is easy to get the reliable details in the pre design itself. By this one can ensure the
safety of the component and the system also. In this investigation, the effects of torsional loads on mild steel
round shafts with various diameters and lengths have been analyzed. The additional effects like angle of
rotation, rpm and duration also considered to find the optimum predicted value. The data observed by
various experiments are analyzed by design of experiments especially by response surface methodology.
Minitab software is used for canalization. The data are tabulated and kept for future reference. Noise effect
due to the gradual torsional load performed in the gear box and other rotating components is also studied
for healthy working environment. The nature and characteristics of material also be explained by this noise
analysis.
Modeling, Analyzing and Safety Aspects of Torsion and Noise Effects on Round ...msejjournal
Each material has its own effect and behavior on external impacts like heat, force, tension, compression,
torsion etc. It is important to study and analyze these behaviors before selecting a material for an
engineering application in the design aspects itself. If predicted values analyzed by both mathematical and
software are available it is easy to get the reliable details in the pre design itself. By this one can ensure the
safety of the component and the system also. In this investigation, the effects of torsional loads on mild steel
round shafts with various diameters and lengths have been analyzed. The additional effects like angle of
rotation, rpm and duration also considered to find the optimum predicted value. The data observed by
various experiments are analyzed by design of experiments especially by response surface methodology.
Minitab software is used for canalization. The data are tabulated and kept for future reference. Noise effect
due to the gradual torsional load performed in the gear box and other rotating components is also studied
for healthy working environment. The nature and characteristics of material also be explained by this noise
analysis.
MODELING, ANALYZING AND SAFETY ASPECTS OF TORSION AND NOISE EFFECTS ON ROUND ...msejjournal
Each material has its own effect and behavior on external impacts like heat, force, tension, compression, torsion etc. It is important to study and analyze these behaviors before selecting a material for an engineering application in the design aspects itself. If predicted values analyzed by both mathematical and software are available it is easy to get the reliable details in the pre design itself. By this one can ensure the safety of the component and the system also. In this investigation, the effects of torsional loads on mild steel
round shafts with various diameters and lengths have been analyzed. The additional effects like angle of rotation, rpm and duration also considered to find the optimum predicted value. The data observed by various experiments are analyzed by design of experiments especially by response surface methodology. Minitab software is used for canalization. The data are tabulated and kept for future reference. Noise effect
due to the gradual torsional load performed in the gear box and other rotating components is also studied for healthy working environment. The nature and characteristics of material also be explained by this noise analysis.
The Study of Premature Failure of Springs Used In Railway CoachesIOSR Journals
The springs used in the bogie suspension of railway coaches are compression springs. They are
made of an elastic wire material formed into the shape of a helix. They are commonly referred to as a coil
spring or a helical spring. They are used to store energy and subsequently release it to absorb shock or to
maintain a force between contact surfaces. The spring returns to its natural length or position when unloaded.
Springs used in railway coaches have been failing prematurely much before their intended service life. The
springs are made with quality materials. Before being put to service, the springs are tested with extensive Non
Destructive Testing Methods which are approved by ISO standards to make sure that quality parts are used.
However the springs still fail before their service life ends
A Study on Translucent Concrete Product and Its Properties by Using Optical F...IJMER
- Translucent concrete is a concrete based material with light-transferring properties,
obtained due to embedded light optical elements like Optical fibers used in concrete. Light is conducted
through the concrete from one end to the other. This results into a certain light pattern on the other
surface, depending on the fiber structure. Optical fibers transmit light so effectively that there is
virtually no loss of light conducted through the fibers. This paper deals with the modeling of such
translucent or transparent concrete blocks and panel and their usage and also the advantages it brings
in the field. The main purpose is to use sunlight as a light source to reduce the power consumption of
illumination and to use the optical fiber to sense the stress of structures and also use this concrete as an
architectural purpose of the building
Developing Cost Effective Automation for Cotton Seed DelintingIJMER
A low cost automation system for removal of lint from cottonseed is to be designed and
developed. The setup consists of stainless steel drum with stirrer in which cottonseeds having lint is mixed
with concentrated sulphuric acid. So lint will get burn. This lint free cottonseed treated with lime water to
neutralize acidic nature. After water washing this cottonseeds are used for agriculter purpose
Study & Testing Of Bio-Composite Material Based On Munja FibreIJMER
The incorporation of natural fibres such as munja fiber composites has gained
increasing applications both in many areas of Engineering and Technology. The aim of this study is to
evaluate mechanical properties such as flexural and tensile properties of reinforced epoxy composites.
This is mainly due to their applicable benefits as they are light weight and offer low cost compared to
synthetic fibre composites. Munja fibres recently have been a substitute material in many weight-critical
applications in areas such as aerospace, automotive and other high demanding industrial sectors. In
this study, natural munja fibre composites and munja/fibreglass hybrid composites were fabricated by a
combination of hand lay-up and cold-press methods. A new variety in munja fibre is the present work
the main aim of the work is to extract the neat fibre and is characterized for its flexural characteristics.
The composites are fabricated by reinforcing untreated and treated fibre and are tested for their
mechanical, properties strictly as per ASTM procedures.
Hybrid Engine (Stirling Engine + IC Engine + Electric Motor)IJMER
Hybrid engine is a combination of Stirling engine, IC engine and Electric motor. All these 3 are
connected together to a single shaft. The power source of the Stirling engine will be a Solar Panel. The aim of
this is to run the automobile using a Hybrid engine
Fabrication & Characterization of Bio Composite Materials Based On Sunnhemp F...IJMER
The present day technology demands eco-friendly developments. In this era the
composite material are playing a vital roal in different field of Engineering .The composite materials
are using as a principle materials. Nowaday the composite materials are utilizing as a important
component of engineering field .Where as the importance of the applications of composites is well
known, but thrust on the use of natural fibres in it for reinforcement has been given priority for some
times. But changing from synthetic fibres to natural fibres provides only half green-composites. A
partial green composite will be achieved if the matrix component is also eco-friendly. Keeping this in
view, a detailed literature surveyed has been carried out through various issues of the Journals
related to this field. The material systems used are sunnhemp fibres. Some epoxy and hardener has
been also added for stability and drying of the bio-composites. Various graphs and bar-charts are
super-imposed on each other for comparison among themselves and Graphs is plotted on MAT LAB
and ORIGIN 6.0 software. To determining tensile strengths, Various properties for different biocomposites
have been compared among themselves. Comparison of the behaviour of bio-composites of
this work has been also compare with other works. The bio-composites developed in this work are
likely to get applications in fall ceilings, partitions, bio-degradable packagings, automotive interiors,
sports things (e.g. rackets, nets, etc.), toys etc.
Geochemistry and Genesis of Kammatturu Iron Ores of Devagiri Formation, Sandu...IJMER
The Greenstone belts of Karnataka are enriched in BIFs in Dharwar craton, where Iron
formations are confined to the basin shelf, clearly separated from the deeper-water iron formation that
accumulated at the basin margin and flanking the marine basin. Geochemical data procured in terms of
major, trace and REE are plotted in various diagrams to interpret the genesis of BIFs. Al2O3, Fe2O3 (T),
TiO2, CaO, and SiO2 abundances and ratios show a wide variation. Ni, Co, Zr, Sc, V, Rb, Sr, U, Th,
ΣREE, La, Ce and Eu anomalies and their binary relationships indicate that wherever the terrigenous
component has increased, the concentration of elements of felsic such as Zr and Hf has gone up. Elevated
concentrations of Ni, Co and Sc are contributed by chlorite and other components characteristic of basic
volcanic debris. The data suggest that these formations were generated by chemical and clastic
sedimentary processes on a shallow shelf. During transgression, chemical precipitation took place at the
sediment-water interface, whereas at the time of regression. Iron ore formed with sedimentary structures
and textures in Kammatturu area, in a setting where the water column was oxygenated.
Experimental Investigation on Characteristic Study of the Carbon Steel C45 in...IJMER
In this paper, the mechanical characteristics of C45 medium carbon steel are investigated
under various working conditions. The main characteristic to be studied on this paper is impact toughness
of the material with different configurations and the experiment were carried out on charpy impact testing
equipment. This study reveals the ability of the material to absorb energy up to failure for various
specimen configurations under different heat treated conditions and the corresponding results were
compared with the analysis outcome
Non linear analysis of Robot Gun Support Structure using Equivalent Dynamic A...IJMER
Robot guns are being increasingly employed in automotive manufacturing to replace
risky jobs and also to increase productivity. Using a single robot for a single operation proves to be
expensive. Hence for cost optimization, multiple guns are mounted on a single robot and multiple
operations are performed. Robot Gun structure is an efficient way in which multiple welds can be done
simultaneously. However mounting several weld guns on a single structure induces a variety of
dynamic loads, especially during movement of the robot arm as it maneuvers to reach the weld
locations. The primary idea employed in this paper, is to model those dynamic loads as equivalent G
force loads in FEA. This approach will be on the conservative side, and will be saving time and
subsequently cost efficient. The approach of the paper is towards creating a standard operating
procedure when it comes to analysis of such structures, with emphasis on deploying various technical
aspects of FEA such as Non Linear Geometry, Multipoint Constraint Contact Algorithm, Multizone
meshing .
Static Analysis of Go-Kart Chassis by Analytical and Solid Works SimulationIJMER
This paper aims to do modelling, simulation and performing the static analysis of a go
kart chassis consisting of Circular beams. Modelling, simulations and analysis are performed using 3-D
modelling software i.e. Solid Works and ANSYS according to the rulebook provided by Indian Society of
New Era Engineers (ISNEE) for National Go Kart Championship (NGKC-14).The maximum deflection is
determined by performing static analysis. Computed results are then compared to analytical calculation,
where it is found that the location of maximum deflection agrees well with theoretical approximation but
varies on magnitude aspect.
In récent year various vehicle introduced in market but due to limitation in
carbon émission and BS Séries limitd speed availability vehicle in the market and causing of
environnent pollution over few year There is need to decrease dependancy on fuel vehicle.
bicycle is to be modified for optional in the future To implement new technique using change in
pedal assembly and variable speed gearbox such as planetary gear optimise speed of vehicle
with variable speed ratio.To increase the efficiency of bicycle for confortable drive and to
reduce torque appli éd on bicycle. we introduced epicyclic gear box in which transmission done
throgh Chain Drive (i.e. Sprocket )to rear wheel with help of Epicyclical gear Box to give
number of différent Speed during driving.To reduce torque requirent in the cycle with change in
the pedal mechanism
Integration of Struts & Spring & Hibernate for Enterprise ApplicationsIJMER
The proposal of this paper is to present Spring Framework which is widely used in
developing enterprise applications. Considering the current state where applications are developed using
the EJB model, Spring Framework assert that ordinary java beans(POJO) can be utilize with minimal
modifications. This modular framework can be used to develop the application faster and can reduce
complexity. This paper will highlight the design overview of Spring Framework along with its features that
have made the framework useful. The integration of multiple frameworks for an E-commerce system has
also been addressed in this paper. This paper also proposes structure for a website based on integration of
Spring, Hibernate and Struts Framework.
Microcontroller Based Automatic Sprinkler Irrigation SystemIJMER
Microcontroller based Automatic Sprinkler System is a new concept of using
intelligence power of embedded technology in the sprinkler irrigation work. Designed system replaces
the conventional manual work involved in sprinkler irrigation to automatic process. Using this system a
farmer is protected against adverse inhuman weather conditions, tedious work of changing over of
sprinkler water pipe lines & risk of accident due to high pressure in the water pipe line. Overall
sprinkler irrigation work is transformed in to a comfortableautomatic work. This system provides
flexibility & accuracy in respect of time set for the operation of a sprinkler water pipe lines. In present
work the author has designed and developed an automatic sprinkler irrigation system which is
controlled and monitored by a microcontroller interfaced with solenoid valves.
On some locally closed sets and spaces in Ideal Topological SpacesIJMER
In this paper we introduce and characterize some new generalized locally closed sets
known as
δ
ˆ
s-locally closed sets and spaces are known as
δ
ˆ
s-normal space and
δ
ˆ
s-connected space and
discussed some of their properties
Intrusion Detection and Forensics based on decision tree and Association rule...IJMER
This paper present an approach based on the combination of, two techniques using
decision tree and Association rule mining for Probe attack detection. This approach proves to be
better than the traditional approach of generating rules for fuzzy expert system by clustering methods.
Association rule mining for selecting the best attributes together and decision tree for identifying the
best parameters together to create the rules for fuzzy expert system. After that rules for fuzzy expert
system are generated using association rule mining and decision trees. Decision trees is generated for
dataset and to find the basic parameters for creating the membership functions of fuzzy inference
system. Membership functions are generated for the probe attack. Based on these rules we have
created the fuzzy inference system that is used as an input to neuro-fuzzy system. Fuzzy inference
system is loaded to neuro-fuzzy toolbox as an input and the final ANFIS structure is generated for
outcome of neuro-fuzzy approach. The experiments and evaluations of the proposed method were
done with NSL-KDD intrusion detection dataset. As the experimental results, the proposed approach
based on the combination of, two techniques using decision tree and Association rule mining
efficiently detected probe attacks. Experimental results shows better results for detecting intrusions as
compared to others existing methods
Natural Language Ambiguity and its Effect on Machine LearningIJMER
"Natural language processing" here refers to the use and ability of systems to process
sentences in a natural language such as English, rather than in a specialized artificial computer
language such as C++. The systems of real interest here are digital computers of the type we think of as
personal computers and mainframes. Of course humans can process natural languages, but for us the
question is whether digital computers can or ever will process natural languages. We have tried to
explore in depth and break down the types of ambiguities persistent throughout the natural languages
and provide an answer to the question “How it affects the machine translation process and thereby
machine learning as whole?” .
Today in era of software industry there is no perfect software framework available for
analysis and software development. Currently there are enormous number of software development
process exists which can be implemented to stabilize the process of developing a software system. But no
perfect system is recognized till yet which can help software developers for opting of best software
development process. This paper present the framework of skillful system combined with Likert scale. With
the help of Likert scale we define a rule based model and delegate some mass score to every process and
develop one tool name as MuxSet which will help the software developers to select an appropriate
development process that may enhance the probability of system success.
Material Parameter and Effect of Thermal Load on Functionally Graded CylindersIJMER
The present study investigates the creep in a thick-walled composite cylinders made
up of aluminum/aluminum alloy matrix and reinforced with silicon carbide particles. The distribution
of SiCp is assumed to be either uniform or decreasing linearly from the inner to the outer radius of
the cylinder. The creep behavior of the cylinder has been described by threshold stress based creep
law with a stress exponent of 5. The composite cylinders are subjected to internal pressure which is
applied gradually and steady state condition of stress is assumed. The creep parameters required to
be used in creep law, are extracted by conducting regression analysis on the available experimental
results. The mathematical models have been developed to describe steady state creep in the composite
cylinder by using von-Mises criterion. Regression analysis is used to obtain the creep parameters
required in the study. The basic equilibrium equation of the cylinder and other constitutive equations
have been solved to obtain creep stresses in the cylinder. The effect of varying particle size, particle
content and temperature on the stresses in the composite cylinder has been analyzed. The study
revealed that the stress distributions in the cylinder do not vary significantly for various combinations
of particle size, particle content and operating temperature except for slight variation observed for
varying particle content. Functionally Graded Materials (FGMs) emerged and led to the development
of superior heat resistant materials.
Energy Audit is the systematic process for finding out the energy conservation
opportunities in industrial processes. The project carried out studies on various energy conservation
measures application in areas like lighting, motors, compressors, transformer, ventilation system etc.
In this investigation, studied the technical aspects of the various measures along with its cost benefit
analysis.
Investigation found that major areas of energy conservation are-
1. Energy efficient lighting schemes.
2. Use of electronic ballast instead of copper ballast.
3. Use of wind ventilators for ventilation.
4. Use of VFD for compressor.
5. Transparent roofing sheets to reduce energy consumption.
So Energy Audit is the only perfect & analyzed way of meeting the Industrial Energy Conservation.
An Implementation of I2C Slave Interface using Verilog HDLIJMER
The focus of this paper is on implementation of Inter Integrated Circuit (I2C) protocol
following slave module for no data loss. In this paper, the principle and the operation of I2C bus protocol
will be introduced. It follows the I2C specification to provide device addressing, read/write operation and
an acknowledgement. The programmable nature of device provide users with the flexibility of configuring
the I2C slave device to any legal slave address to avoid the slave address collision on an I2C bus with
multiple slave devices. This paper demonstrates how I2C Master controller transmits and receives data to
and from the Slave with proper synchronization.
The module is designed in Verilog and simulated in ModelSim. The design is also synthesized in Xilinx
XST 14.1. This module acts as a slave for the microprocessor which can be customized for no data loss.
Discrete Model of Two Predators competing for One PreyIJMER
This paper investigates the dynamical behavior of a discrete model of one prey two
predator systems. The equilibrium points and their stability are analyzed. Time series plots are obtained
for different sets of parameter values. Also bifurcation diagrams are plotted to show dynamical behavior
of the system in selected range of growth parameter
Discrete Model of Two Predators competing for One Prey
Ijmer 46060714
1. International
OPEN ACCESS Journal
Of Modern Engineering Research (IJMER)
| IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 6| June. 2014 | 7|
Investigation of the Role of Bulkhead and Crack Stopper Strap in
the Fail-Safe Design of a Wide Bodied Transport Aircraft
Shadrak Babu.Katta1
, Dr M.V.Mallikharjuna2
1, 2
PG Student, Professor, Department of Mechanical Engineering , QIS College Of Engineering &Technology,
Ongole
I. Introduction
The basic functions of an aircraft’s structure are to transmit and resist the applied loads; to provide an
aerodynamic shape and to protect passengers, payload systems, etc., from the environmental conditions
encountered in flight. These requirements, in most aircraft, result in thin shell structures where the outer surface
or skin of the shell is usually supported by longitudinal stiffening members and transverse frames to enable it to
resist bending, compressive and torsional loads without buckling. Such structures are known as semi-
monocoque, while thin shells which rely entirely on their skins for their capacity to resist loads are referred to as
monocoque.
The load-bearing members of these main sections, those subjected to major forces, are called the
airframe. The airframe is what remains if all equipment and systems are stripped away. In most modern aircrafts,
the skin plays an important role in carrying loads. Sheet metals can usually only support tension. But if the sheet
is folded, it suddenly does have the ability to carry compressive loads. Stiffeners are used for that. A section of
skin, combined with stiffeners, called stringers, is termed a thin-walled structure.
The main body structure is the fuselage to which all other components are attached. The fuselage
contains the cockpit or flight deck, passenger compartment and cargo compartment. While wings produce most
of the lift, the fuselage also produces a little lift.
A bulky fuselage can also produce a lot of drag. For this reason, a fuselage is streamlined to decrease
the drag. We usually think of a streamlined car as being sleek and compact - it does not present a bulky obstacle
to the oncoming wind. A streamlined fuselage has the same attributes. It has a sharp or rounded nose with sleek,
tapered body so that the air can flow smoothly around it.
As a result of the investigations into the accidents in the 1950’s, aircraft manufacturers began to
incorporate into their fuselage designs features which would increase the ability of the aircraft to sustain damage
caused by fatigue cracking; i.e., a damage tolerant design philosophy. A reinforced doubler on the inside of the
fuselage skin, termed tear strap, crack stopper strap, or fail-safe strap, is commonly employed. Tear straps are
simply strips of material attached circumferentially to the skin of the fuselage which capitalize on the advantage
of flapping. A tear strap locally reduces the hoop stress thus causing the bulge stress to become greater than the
hoop stress for an axial crack length that is less than the axial crack length for flapping the un-stiffened cylinder.
Properly designed tear straps are able to induce flapping and contain the damage between two tear straps.
These tear straps are made up of aluminum alloy and are placed between the bulkhead and skin and
they run below the bulkhead as shown in the figure1
Abstract: One of the fail-safe design features is the two-bay crack arrest capability of the airframe. In
particular two-bay longitudinal and two-bay circumferential crack arrest feature is the main aspect of
design for damage tolerance of the pressurized fuselage cabin. Under fuselage pressurization load cycles
fatigue cracks develop at location of maximum tensile stress. There are locations on the airframe which
are favorable for the initiation of longitudinal cracks and other locations for circumferential cracks.This
investigation identifies one such location from where a longitudinal crack can initiate and studies the fast
fracture and crack arrest features under the action of uni-axial hoop stress. The main crack arresting
features are the bulkheads and crack stopper straps.A finite element modeling and analysis approach will
be used for a realistic consideration of bulkheads and crack stopper straps and their role in the two-bay
crack arrest capability of the aircraft.In particular through a stress analysis at a hoop stress
corresponding to the design limit load, the load carrying ability of the bulkheads and the crack stopper
straps will be assessed.For a realistic representation of two-bay cracking scenario it will be examined
under what condition a two-bay crack can be arrested.
Keywords: Damage tolerance, circumferential crack, fracture, bulkhead, tear strap, Finite element
analysis, fail-safe design.
2. Investigation Of The Role Of Bulkhead and Crack Stopper Strap In The Fail-Safe Design Of A Wide
| IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 6| June. 2014 | 8|
ref: H. Vlieger,
Figure.1 (a) Frame with Crack stopper
(b) Frame without Crack stopper
1.1 The problem
Stiffened panels are the most generic structural elements in an airframe. Currently large transport
airplanes are being developed with “Large damage tolerance capability” as a design goal. An important concept
in the design of the pressurized fuselage of large transport aircraft is the provision of crack stopper straps to
arrest the fast fracturing of a crack.
1.2 Objective of the present work
In this project the role of the crack stopper strap in the fail-safe design of the fuselage is investigated. As
a first approximation a stiffened flat panel with a center longitudinal crack is considered. The strength of this
cracked panel is investigated as a function of crack length in the absence of crack stopper straps. Crack stopper
straps is then introduced at the locations of stiffeners perpendicular to the crack line and strength of the cracked
flat panel is investigated as a function of crack length in the presence of crack stopper straps.
The failure criteria that is used in this study are
The skin crack will have a fast fracture when the maximum stress intensity factor becomes equal to the fracture
toughness of the skin material at that thickness
1. There is no rivet failure
2. There is no failure of the stiffener normal to the crack Line
A Finite element analysis approach is followed in this investigation. Industry relevant data is used in
this investigation .Geometrical dimensions representative of actual aircraft in service is considered. The material
is taken as 2024-T3 sheet aluminum alloy.
A panel strength diagram is derived from the stress analysis of this cracked stiffened panel. This
diagram illustrates the strength of the skin and the stiffener as function of crack length
SKIN
STRINGER
R
BULKH
EAD
3. Investigation Of The Role Of Bulkhead and Crack Stopper Strap In The Fail-Safe Design Of A Wide
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II. Material Properties
The material considered for the structure is Aluminum Alloy – 2024-T351, with the following
properties.
Young’s Modulus, E = 70,000 N/mm2
Poison's Ratio, μ = 0.3
Ultimate Tensile Strength, σu = 420 N/mm2
Yield Stress, σy = 350 N/mm2
The following table shows the composition of the material considered.
Table.1 Chemical composition of AA 2024-T351 aluminum alloy
M Wt. % M Wt. %
Al 90.7-94.7 Mn 0.3-0.9
Cr max. 0.1 Si max. 0.5
Cu 3.8-4.9 Ti max. 0.15
Fe max. 0.5 Zn max. 0.25
Mg 5.2-5.8 Others max. 0.15
A small part of fuselage is taken, which is rectangular stiffened panel as shown in the Figure 2 and relevant loads
and boundary conditions are applied and analyzed. The stiffened panel consists of, Skin, Bulkhead, Crack
stopper strap (tear strap), Longerons (stringer) Fasteners (rivets).
Figure.2 Detailed view of fuselage part
All the components of the stiffened panel are assembled together by riveting with the rivet pitch 25mm
and diameter of the rivet is 5mm.
The following Figure.4 show the details about the finite element mesh generated on each part of the
structure using MSC PATRAN.
Fig 3: Close up view of stiffened panel
Figure.4Complete finite element mesh on stiffened panel
Figure.5 Geometric dimensions of tear strap (crack stopper)
In the Finite element meshing of tear strap nodes are placed at calculated distance so that the riveting
could be carried out in a proper way. The tear straps are placed on the skin and the rivet nodes are aligned so that
the riveting could be carried out once the rest of the components are ready. These tear straps are placed in
between the skin and bulkhead and runs below the bulkhead in the circumferential direction and perpendicular to
the longitudinal crack. The close up view of the meshed tear strap is shown in
4. Investigation Of The Role Of Bulkhead and Crack Stopper Strap In The Fail-Safe Design Of A Wide
| IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 6| June. 2014 | 10|
Figure.6 Finite element mesh on Tear strap
Loads and boundary conditions
A differential pressure of 9 psi (0.062066MPa) is considered for the current load case. Due to this
internal pressurization of fuselage (passenger cabin) the hoop stress will be developed in the fuselage structure.
The tensile loads at the edge of the panel corresponding to pressurization will be considered for the linear static
analysis of the panel.
Hoop stress is given by
σ hoop =
Where
Wh Cabin pressure (p) = 9 psi= 0.062066MPa
Radius of fuselage(r) = 1500 mm
Thickness of skin (t) = 1.5mm
After substitution of these values in (Eq6.1) we will get
σ hoop =6.327 N/mm2
We know that
σ hoop =
Above equation can be written as
P = σ hoop *A ------ Eq.1
Load on Tear strap
Here
Pts=Load on skin
σ hoop =6.327 Kg/mm2
A=Cross sectional area of each Tear strap in mm2
i.e. Width *Thickness(30*1.5)
Substituting these values in the Eq.1
we get
Pts=1423Kg On each Tear strap
Uniformly distributed load on Tear strap will be
Pts =9.4905Kg/mm
Fig 7.Stress counter for tear strap
5. Investigation Of The Role Of Bulkhead and Crack Stopper Strap In The Fail-Safe Design Of A Wide
| IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 6| June. 2014 | 11|
Figure shows the stress contour on the tear strap from global analysis results. It is clear that the
maximum stress on tear strap is at the rivet location where the rivets are used to fasten tear strap, bulkhead and
longeron on skin.
Stress intensity factor (SIF) approach
There are different methods used in the numerical fracture mechanics to calculate stress intensity factors
(SIF). The Virtual Crack Closure Technique (VCCT) originally proposed in 1977 by Rybicki and Kanninen, is a
very attractive SIF extraction technique because of its good accuracy, a relatively easy algorithm of application
capability to calculate SIF for all three fracture modes. The VCCT has a significant advantage over other
methods, it has not yet been implemented into most of the large commercial general-purpose finite element
codes.
The detail calculation of the energy release rate is,
G= ------Eq.2
Where
G=Strain energy release rate
F=Forces at the crack tip in kg or N
𝜟c=change in virtual crack length in mm
t= thickness of skin in mm
Then the SIF is calculated by FEM method by substituting Eq.2 in below Eq.3
KI= --MPa -----Eq.3
Where,
KI= stress intensity factor (SIF)
E =young’s modulus =7000Kg/mm2
= 68670 Mpa
G=Strain energy release rate
Theoretically SIF value is calculated by
KI = * f ( ---MPa --- (Eq.4)
And
f ( = ---(Eq.5)
Where
= Crack length in mm
f ( =Correction factor
b=Width of the plate (1500mm)
SIF (stress intensity factor) has been calculated by FEM (by using VCCT technique). SIF values are
obtained analytically(FEM) by using EQUATIONS 2 AND 3 for un-stiffened panel having same dimension as
skin in stiffened panel by applying boundary conditions which are discussed earlier. SIF values are also obtained
for stiffened panel using FEM.
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Crack
length mm
SIF by Theoretical in
MPa√m
SIF by FEM
Analytical in
MPa√m
50 26.1 26.53
100 36.92 37.59
150 45.25 46.13
200 52.30 53.39
250 58.54 59.85
300 64.23 65.75
350 69.50 71.25
400 74.46 76.45
450 79.16 81.39
500 83.68 86.16
550 88.04 90.78
600 92.28 95.28
Table 2. comparison between theoritical and fem
From the table 2 it is clear that SIF values obtained by using FEM (by using VCCT technique) for un-
stiffened panel agrees with the SIF values calculated theoretically.Therefore FEM (by using VCCT method) for
finding SIF value is valid. For the evaluation of effect of tear strap (crack stopper strap) for crack arrest
capability, as a first approximation a stiffened flat panel with a center longitudinal crack is considered. The SIF
value of this cracked panel is investigated as a function of crack length in the absence of crack stopper straps.
Crack stopper straps are then introduced at the locations of stiffeners perpendicular to the crack line. The SIF
Values of the cracked flat panel is investigated as a function of crack length in the presence of crack stopper
straps. In the parametric study the thickness is varied. The SIF values obtained for stiffened panel without tear
strap and stiffened panel with tear strap are compared with the critical stress intensity factor KIc (Fracture
toughness of the material) If SIF (K) at the crack tip approaches or exceeds an upper limit of stress intensity
factor (KIc), then the crack will zip through leading to catastrophic failure of the structure. The upper limit is
known as critical stress intensity factor (Fracture toughness of the material) which is the material property and is
usually denoted by KIc. Graph 1. sif vs cracklength
The stress intensity factor is a parameter to measure severity of stress at the crack tip but critical stress
intensity factor is the limit on SIF such that if SIF exceeds beyond the critical stress intensity factor, the crack
will grow rapidly leading to the final failure.
When the crack stress intensity factor due to remote loading reduces below the fracture toughness of the
material then a crack will get arrested. We know that aluminum maximum yield strength is 35 kg/mm2
. The
structure is normally designed in such a way that the maximum stress developed at design limit load will be
equal to the yield strength of the material. By using incremental ratio, which is ratio of aluminum yield strength
to the obtained maximum stress.
= = 1.35
So we can increase the stress to 1.35 times the originally obtained values. Those values are calculated and
tabulated below.
Crack
length
(a) in mm
KI FEA
without Tear
strap
(MPa√m)
KI FEA with
Tear strap
(MPa√m)
100 56.06 82.35
200 68.58 69.57
300 78.92 79.21
400 88.74 88.12
500 96.43 95.40
600 103.63 101.97
700 108.37 104.71
800 102.80 94.44
Table 3. Comparison of KI FEA values with tear strap and without tear strap of stiffened panel for actual loads
and boundary conditions
7. Investigation Of The Role Of Bulkhead and Crack Stopper Strap In The Fail-Safe Design Of A Wide
| IJMER | ISSN: 2249–6645 | www.ijmer.com | Vol. 4 | Iss. 6| June. 2014 | 13|
S.I.F as a function of crack length without tear strap
Graph 2. S.I.F as a function of crack length with tear strap
From the results it is clear that the SIF value increases as crack length increases, as the crack approaches
near to the stiffening member (bulkhead and tear strap) SIF decreases because near the stiffener region the load
gets transferred from skin to the stiffener. Therefore the SIF in the skin reduces. When the crack is propagated
beyond the bulkhead position, there will be an increase in SIF because the load shared by the skin increases
gradually. The increasing trend in the curve is observed as the crack moves away from the bulkhead position. So
by using the tear strap we can control the crack growth rate (kI) within the two-bay structure.
III. Conclusion
1. A stiffened panel which is generic structural element of the fuselage structure is evaluated analytically for its
crack arrest capability.
2. Finite element analysis (FEA) approach is used for structural analysis of the stiffened panel.
3. Stress analysis is carried out to identify the maximum tensile stress location in the stiffened panel. The
magnitude of maximum tensile stress in loading direction is 23.3 Kg/mm2
(228.59 MPa) which is in the
bulkhead at the stringer cut-out. The maximum stress locations are the probable locations for crack
initiation. Invariably these locations will be at stringer cut-out locations in the bulkhead.
4. There are other possibilities of crack initiation at different locations in the stiffened panel due to discrete
source of damage. It may be due to bird hit, foreign object hit. For the analysis centre cracked stiffened
panel with central broken bulkhead and tear strap is considered which is due to discrete source of damage.
5. Modified virtual crack closure technique (VCCT) along with FEA analysis results are used for calculation of
stress intensity factor (SIF). The effect of tear strap in arresting two-bay crack is studied.
6. Tear straps (crack stopper straps) with thickness 1.5 mm shows that a two bay crack is arrested it the
stiffened panel.
7. These results were obtained for the rivet pitch of 25mm in the bulkheads by varying the pitch of the rivet
may alter the crack arrest capability of the stiffened panel.
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