The document is a thesis report submitted by Ng Jun Jie to the Department of Mechanical Engineering at the National University of Singapore in partial fulfillment of the requirements for a Bachelor of Engineering degree. The report analyzes and aims to improve the jacking systems used for lifting offshore jack-up rigs by studying the fatigue life of the rack and pinion mechanism and proposing ways to reduce stress through modeling and simulation.
Design and Development of Spur Gear by using Three Dimensional Printingijtsrd
Gears are power transmission devices in between input and output of machines, these power transmitting elements are very compact, and they transfer power with minimum loss. Due to the nature of their different speed ratios they are used for different applications like high speed marine engines, automobiles etc. Different materials are used for preparation or fabrication of gears like metals steel or brass , plastics nylon or polycarbonate . In this project spur gear is designed by CAD software and fabricated by using 3D printer, for 3D printing materials require like plastics or ceramics but for this project plastic material is used that is polylactic acid PLA . By using 3D printer spur gear is produced within a small period with better dimensional accuracy than conventional method like milling etc. P. Naresh | Aman Raj | J. Tarun | Ejazur Rahman | G. Bharat ""Design and Development of Spur Gear by using Three Dimensional Printing"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-3 , April 2019, URL: https://www.ijtsrd.com/papers/ijtsrd23236.pdf
Paper URL: https://www.ijtsrd.com/engineering/mechanical-engineering/23236/design-and-development-of-spur-gear-by-using-three-dimensional-printing/p-naresh
This document contains 22 physics questions related to topics like motion, force, energy, density, and power. It provides sample exam questions, diagrams of experimental setups, and asks students to analyze graphs and scenarios involving physical concepts. The questions cover a range of skills like calculations, explaining physical phenomena, describing experimental procedures, and interpreting diagrams and graphs.
The document describes changes made by CIE to question papers for popular assessments with large candidature. CIE uses different variants of question papers that are closely related and give equal assessment standards. This means for some components there are now two variant question papers, mark schemes, and principal examiner reports, rather than just one previously. Centres will receive both variants, giving more past exam material. The diagram shows the relationship between question papers, mark schemes, and principal examiner reports for the first and second variants. Centres with questions should contact CIE customer services. Variant items should be clearly labeled as first or second variant in the document.
This document contains instructions for three physics experiments investigating:
1) The motion of a mass hanging on a spring, measuring spring constants and oscillation times. Results show oscillation time increases with mass.
2) The cooling rate of a thermometer bulb with and without insulation. Results show insulation decreases cooling rate.
3) The resistance of a lamp filament, measuring resistance at different points in a circuit. Results show resistance increases with current.
This document is an exam paper for a Cambridge International General Certificate of Secondary Education (IGCSE) Physics exam. It consists of three experiments on density, cooling of water, and electrical resistance. In the first experiment, students determine the density of water using two methods - measuring the mass and volume of water directly, and using displacement. The second experiment investigates how the temperature of different volumes of water changes over time as they cool. The third experiment involves measuring the potential difference and current for different wires to calculate their resistance. Students are required to record their results, make calculations, draw conclusions, and identify sources of error.
The document describes a laboratory experiment to determine the compressive strength of concrete cubes at 7 days. Three 150mm concrete cubes were cast and tested after 7 days of curing. The average weight of the cubes was 8.65kg. When tested, the cubes failed at an average maximum load of 15.97 MPa. This shows the 7 day compressive strength of the concrete mix met the target strength of 19.5 MPa specified for M30 grade concrete. The results were analyzed to calculate compressive strength and standard deviation according to standard formulas.
The document provides information on using the Q-system for rock mass classification and support design. It discusses the history and areas of application of the Q-system. It then describes how the Q-value is calculated using six parameters: RQD, Jn, Jr, Ja, Jw, and SRF. These parameters characterize the degree of jointing, joint friction, and stress conditions in the rock mass. The document provides guidance on determining values for each parameter based on field observations and mapping in underground excavations. The calculated Q-value can then be used with the support chart to evaluate required rock support.
IRJET- Experimental Stress Analysis of Worm Wheel used in Crate Washer GearboxIRJET Journal
This document describes an experimental stress analysis of a worm wheel used in a gearbox for a crate washer. The gearbox was experiencing failures of the worm wheel teeth due to excessive bending stresses. Both theoretical and experimental analyses were conducted. The theoretical analysis used Lewis' equation to calculate bending stresses. The experimental analysis used photo stress methods to directly measure stresses by applying loads that simulated actual operating conditions and observing colored fringe patterns with a polariscope. This allowed quantification of stresses at points of high stress. The analyses found the worm wheel's material and geometry were improperly selected for the application, leading to failures. The worm wheel was then redesigned with new material and geometry suitable for the required working conditions.
Design and Development of Spur Gear by using Three Dimensional Printingijtsrd
Gears are power transmission devices in between input and output of machines, these power transmitting elements are very compact, and they transfer power with minimum loss. Due to the nature of their different speed ratios they are used for different applications like high speed marine engines, automobiles etc. Different materials are used for preparation or fabrication of gears like metals steel or brass , plastics nylon or polycarbonate . In this project spur gear is designed by CAD software and fabricated by using 3D printer, for 3D printing materials require like plastics or ceramics but for this project plastic material is used that is polylactic acid PLA . By using 3D printer spur gear is produced within a small period with better dimensional accuracy than conventional method like milling etc. P. Naresh | Aman Raj | J. Tarun | Ejazur Rahman | G. Bharat ""Design and Development of Spur Gear by using Three Dimensional Printing"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-3 , April 2019, URL: https://www.ijtsrd.com/papers/ijtsrd23236.pdf
Paper URL: https://www.ijtsrd.com/engineering/mechanical-engineering/23236/design-and-development-of-spur-gear-by-using-three-dimensional-printing/p-naresh
This document contains 22 physics questions related to topics like motion, force, energy, density, and power. It provides sample exam questions, diagrams of experimental setups, and asks students to analyze graphs and scenarios involving physical concepts. The questions cover a range of skills like calculations, explaining physical phenomena, describing experimental procedures, and interpreting diagrams and graphs.
The document describes changes made by CIE to question papers for popular assessments with large candidature. CIE uses different variants of question papers that are closely related and give equal assessment standards. This means for some components there are now two variant question papers, mark schemes, and principal examiner reports, rather than just one previously. Centres will receive both variants, giving more past exam material. The diagram shows the relationship between question papers, mark schemes, and principal examiner reports for the first and second variants. Centres with questions should contact CIE customer services. Variant items should be clearly labeled as first or second variant in the document.
This document contains instructions for three physics experiments investigating:
1) The motion of a mass hanging on a spring, measuring spring constants and oscillation times. Results show oscillation time increases with mass.
2) The cooling rate of a thermometer bulb with and without insulation. Results show insulation decreases cooling rate.
3) The resistance of a lamp filament, measuring resistance at different points in a circuit. Results show resistance increases with current.
This document is an exam paper for a Cambridge International General Certificate of Secondary Education (IGCSE) Physics exam. It consists of three experiments on density, cooling of water, and electrical resistance. In the first experiment, students determine the density of water using two methods - measuring the mass and volume of water directly, and using displacement. The second experiment investigates how the temperature of different volumes of water changes over time as they cool. The third experiment involves measuring the potential difference and current for different wires to calculate their resistance. Students are required to record their results, make calculations, draw conclusions, and identify sources of error.
The document describes a laboratory experiment to determine the compressive strength of concrete cubes at 7 days. Three 150mm concrete cubes were cast and tested after 7 days of curing. The average weight of the cubes was 8.65kg. When tested, the cubes failed at an average maximum load of 15.97 MPa. This shows the 7 day compressive strength of the concrete mix met the target strength of 19.5 MPa specified for M30 grade concrete. The results were analyzed to calculate compressive strength and standard deviation according to standard formulas.
The document provides information on using the Q-system for rock mass classification and support design. It discusses the history and areas of application of the Q-system. It then describes how the Q-value is calculated using six parameters: RQD, Jn, Jr, Ja, Jw, and SRF. These parameters characterize the degree of jointing, joint friction, and stress conditions in the rock mass. The document provides guidance on determining values for each parameter based on field observations and mapping in underground excavations. The calculated Q-value can then be used with the support chart to evaluate required rock support.
IRJET- Experimental Stress Analysis of Worm Wheel used in Crate Washer GearboxIRJET Journal
This document describes an experimental stress analysis of a worm wheel used in a gearbox for a crate washer. The gearbox was experiencing failures of the worm wheel teeth due to excessive bending stresses. Both theoretical and experimental analyses were conducted. The theoretical analysis used Lewis' equation to calculate bending stresses. The experimental analysis used photo stress methods to directly measure stresses by applying loads that simulated actual operating conditions and observing colored fringe patterns with a polariscope. This allowed quantification of stresses at points of high stress. The analyses found the worm wheel's material and geometry were improperly selected for the application, leading to failures. The worm wheel was then redesigned with new material and geometry suitable for the required working conditions.
Centrifuge Testing to Evaluate Seismic Soil-Structure-Interaction and Lateral...Miguel Frias
The document describes centrifuge testing conducted to evaluate seismic soil-structure-interaction and lateral earth pressures near buried water reservoir structures in Southern California. The testing aims to compare the reliability of different pressure sensing technologies in capturing static lateral earth pressures on a simple retaining wall structure. Previous research found obtaining reliable pressure measurements is difficult in a centrifuge environment due to scaling laws. A series of static tests were conducted using Nevada sand backfill and various sensors, including tactile pressure sensors, to test the hypothesis that tactile pressure sensors can provide reliable pressure data in this environment. Soil testing including sieve analysis, specific gravity tests, and pluviation tests were performed to characterize the Nevada sand and calibrate the sensors.
This document contains draft lecture notes on fracture mechanics. It covers several topics:
1) Finite element models for progressive failures using continuum mechanics approaches like plasticity and damage mechanics.
2) An introduction to linear elastic fracture mechanics, including modes of failure, stress intensity factors, and elasticity-based solutions for cracked bodies.
3) Design examples using principles of linear elastic fracture mechanics to assess fracture properties of materials and calculate stress intensity factors.
4) A section on Griffith's theoretical derivation of the strength of solids based on the energy required to create a unit area of new crack surface.
This document summarizes Luigi Gigliotti's 2012 master's thesis which assessed the applicability of the extended finite element method (XFEM) in Abaqus software for modeling crack growth in rubber materials. The thesis first reviewed rubber elasticity, fracture mechanics of rubber, and XFEM. It then formulated static and dynamic analysis problems to evaluate XFEM's ability to model stress/displacement fields and predict crack propagation instant, direction, and speed using neo-Hookean and Arruda-Boyce material models. Results showed XFEM accurately modeled displacement fields but provided no benefits over FEM for stress fields. Difficulties were faced achieving convergence for dynamic analyses. The thesis aimed to help
This document provides recommendations for fatigue design of welded joints and components. It was prepared by the Joint Working Group XIII-XV of the International Institute of Welding and is a revision of previous documents from 1996 and 2002-2007. The document contains contributions from various professors and experts in the field and provides guidelines on determining fatigue actions, fatigue resistance of welded joints, and assessing joints with weld imperfections over multiple chapters and sections. Suggestions to further refine the document can be sent to the chairman.
This document presents a two-rod model to simulate the swing of a golf club. The two-rod model treats the arm and club as two rigid rods connected by a joint representing the wrist. The model calculates the torque applied by the arm and wrist during the swing using Lagrangian mechanics. Numerical solutions of the two-rod model are presented to simulate the clubhead velocity and trajectory for different swing parameters and conditions. Aerodynamic forces on the golf ball and equations to calculate the flight trajectory are also described. The document concludes by outlining a golf simulator software based on the two-rod model and ball flight equations.
This document appears to be an exam paper for physics. It consists of 12 printed pages and contains 11 multi-part questions testing various concepts in physics. The questions cover topics such as springs, motion, forces, gases, temperature measurement, optics, sound, electricity and circuits.
The document describes a numerical simulation of flow through a centrifugal pump impeller. Hassan Adel Talaat El-Sheshtawy conducted 3D CFD simulations using ANSYS/CFX to analyze the flow field and evaluate the slip factor. The simulation results agreed well with the design performance curve, especially near the best efficiency point. Several empirical slip factor correlations were compared to the numerically obtained slip factor. The effects of adding splitters and increasing the number of blades on slip factor, head rise and hydraulic efficiency were also investigated. It was found that while slip factor improved with more blades or longer splitters, hydraulic efficiency did not always increase due to additional losses.
This thesis experimentally and analytically investigates the buckling behavior of graphite/polyimide sandwich panels under edgewise compression loading. Material properties of the panel constituents were determined through flatwise tension and sandwich beam flexure tests. Buckling specimens of varying core thicknesses were tested to investigate failure modes. Specimens with the thinnest core failed by overall buckling near analytical predictions, while thicker cores failed by face wrinkling. Several buckling formulas for wrinkling were found to be unconservative. Recommended wrinkling equations are presented based on the test results. In conclusion, the buckling behavior of the graphite/polyimide sandwich panels was characterized experimentally and compared favorably to analytical predictions.
This thesis examines shallow gas anomalies in the North Sea using AVO analysis and seismic inversion. The author creates a wedge model to estimate the thickness of a thin gas sand detected at 520ms that shows high amplitudes on seismic data. AVO cross-plotting shows the anomaly deviates from the background trend into quadrant III, indicating a Class III gas effect. Tuning curves from the wedge model suggest the anomaly is affected by both gas saturation and tuning effects. Seismic inversion enhances interpretation by showing anomalous low impedance associated with the high amplitude anomaly.
This dissertation applies a modified statistical dynamical diffraction theory (mSDDT) to analyze high-resolution x-ray diffraction (HRXRD) data from C-doped Si and SiGe heterostructures. The mSDDT improves upon previous statistical dynamical diffraction theory by incorporating weighted and layered broadening effects to better model defective and partially relaxed materials. Experimental HRXRD scans of SiGe samples are fitted using mSDDT and compared to commercial software. The results demonstrate mSDDT's ability to quantitatively characterize relaxed and defective semiconductor structures through non-destructive metrology.
MSc_Thesis_Wake_Dynamics_Study_of_an_H-type_Vertical_Axis_Wind_TurbineChenguang He
This thesis investigates the wake dynamics of an H-type vertical axis wind turbine using particle image velocimetry (PIV). Two-component PIV is used to study vorticity shedding and horizontal wake expansion at the turbine mid-span plane. Stereoscopic PIV is performed on 7 cross-stream vertical planes to analyze tip vortex dynamics and the evolution of 3D wake structures. The experimental results show asymmetrical vorticity decay in the horizontal plane, with faster decay on the leeward side. Tip vortices are stronger than shed vortices. Near the turbine axis, tip vortices move inboard behind the rotor before moving outboard towards the windward side further downstream. Vertical
This masters project report describes molecular dynamics simulations performed to study liquid crystals and their potential use in biosensors. Over 50 nanoseconds of simulations were carried out using different atomistic force fields to model the liquid crystal 5CB. The force fields were characterized and compared to experimental data on the phase behavior and properties of bulk 5CB. Simulations were also conducted to study 5CB interactions across water interfaces and observe conformational changes in polypeptides to assess the ability to predict protein structure changes relevant for biosensor applications. Issues encountered are discussed. The work aims to further understanding of liquid crystals at the molecular level to aid the development of liquid crystal-based biosensing technologies.
This document describes a thesis presented by Durlav Mudbhari to Lehigh University for a Master of Science degree in mechanical engineering. The thesis involved designing and developing an experimental setup to measure unsteady forces and power of functionally graded, chordwise flexible wings. A flapping wing system was created with rigid and flexible regions to model functionally graded materials. Experiments were conducted in a wind tunnel and vacuum chamber to measure thrust production, lift/drag forces, and power consumption of wings with varying flexibility. The goal was to better understand how non-homogeneous flexibility impacts wing performance. Potential applications include more efficient autonomous underwater vehicles and ship propulsion through flexible hydrofoils.
Analysis of Ferrocement and Textile Reinforced Concrete for Shell StructuresMile Bezbradica
This document is Mile Bezbradica's master's dissertation which analyzes the stiffness properties of ferrocement, glass fiber textile, and carbon fiber textile for concrete shell structures. Three analysis strategies were used: an analytical model, experimental beam prototypes, and numerical analysis. Comparison of mechanical experiments to numerical models showed stiffness deviations of 38% for ferrocement, 272% for glass fiber, and 211% for carbon fiber beams. Ferrocement was stiffest in experiments but carbon fiber was stiffest in analytical and numerical models. The disparity between numerical and experimental results makes the overall comparison inconclusive. Future research should focus on material properties, numerical modeling assumptions, and construction techniques.
This document presents a numerical lifting line model and blade element model to model the aerodynamic effects of a propeller slipstream on a finite wing. The lifting line model uses a numerical vortex lattice method to predict lift distributions across a wing based on 2D airfoil data and known upstream flow conditions. The blade element model uses momentum theory and blade element analysis to model propeller performance and generate upstream velocity profiles. The combined models are expected to be useful for modeling tail-sitting VTOL aircraft where the propeller slipstream affects wing performance. Results are presented comparing the models to experimental data.
Internship Report: Interaction of two particles in a pipe flowPau Molas Roca
The present document sums up the development and results of the research internship carried out at LEGI Laboratory. The study aimed to understand the hydrodynamic forces involvement in the interaction between two red blood cells located in a capillary (pipe flow). The problem regarding Red Blood Cells (RBCs) moving through a capillary has been tackled from a two-dimensional point of view and has been both analytically and numerically outlined. Finite elements have been used to discretize the geometries considered. Several boundary conditions and geometries were simulated and deeply examined aiming to understand the mechanism governing hydrodynamic attraction and repulsion between red blood cells. The consequent results are analyzed in this report.
Modeling and Structural Analysis of a Wing [FSI ANSYS&MATLAB]BahaaIbrahim10
MODELING AND STRUCTURAL ANALYSIS OF A WING
WITH HISTORICAL PERSPECTIVE.
In our study, analyzing aircraft’s wing with the old assumptions will not give an exact solution but
this solution (total deformation) changes according to the geometry of the cross-section of the beam, so
the total deformation of the beam may be greater or lower than the exact solution. In these two cases,
the solution is not acceptable as in the first case which the deformation is greater than the exact solution
will make more weight and cost, and Engineers design aircraft at minimum weight and less cost. But in
the second case which will make lower deformation than exact solution will be much risky as the aircraft
could be fail at any time, and this case much dangerous because it threatens life of people.
This document is a report that analyzes replacing regular transmission line conductors with superconductors. It discusses the problems with current transmission lines, such as losses due to resistance, instability, and environmental/safety issues. The report proposes using superconducting cables cooled by liquid hydrogen in underground conduits as a solution. It evaluates the feasibility and costs/benefits of implementing this system compared to alternatives. The conclusion recommends superconducting cables as they would eliminate losses and provide a more efficient, reliable and environmentally friendly grid.
The document summarizes a numerical simulation of flow over a low-Reynolds-number flat plate airfoil with a passively actuated trailing-edge flap. Direct numerical simulation was performed at a Reynolds number of 1000 for a flat plate airfoil undergoing sinusoidal plunging motion and equipped with a 30% chord trailing-edge flap modeled as a spring-mounted pendulum. It was observed that the amplitude of flap oscillations increased as the natural frequency of the flap approached the plunging frequency, and negative average drag was produced when the natural frequency was lower than or equal to the plunging frequency. This trend differs from previous results at a higher Reynolds number and suggests the effects of viscosity or wing thickness differences are responsible for the discrepancy
SAIL VERSUS HULL FORM PARAMETER CONFLICTS IN YACHT DESIGNBoyang Wang
The document describes a student project that aims to analyze the influence of sail and hull form parameters on yacht performance. It will generate a series of hull forms by modifying parameters of an initial YD-40 hull. Resistance and stability of the hulls will be calculated and their performance tested using sailing simulation software for different sail configurations. The document reviews methods for hull form modification, section mapping, resistance prediction, and stability analysis that will be used in the project.
In this project we studied dynamic loading behaviour of different models of portal frame which are subjected to moving mass on top of horizontal beam. A finite element simulation has been carried out in order to study the behaviour of a transverse open crack in the horizontal segment of a portal frame while it is subjected to a moving mass. This portal frame is hinged to the ground and only in-plane vibrations are considered. The horizontal section is modelled as two segments connected by a rotational mass-less linear elastic spring. Portal frames are modelled using the C-coding. The characteristic equation is obtained with due consideration towards boundary and compatibility conditions. The resulting characteristic equation is a function of the frames natural frequency, crack location and crack depth. The frequency values are used to decide the appropriate time step for the dynamic analysis. The finite element modelling has been done with singular quadratic quadrilateral planar elements. Results are mainly used to calculate crack opening, crack closing and crack growth rate time. Various conclusive inferences have been made from the results obtained. The output solutions such as stress, strain and displacement was studied and discussed.
MSc Thesis - Luis Felipe Paulinyi - Separation Prediction Using State of the ...Luis Felipe Paulinyi
This thesis examines flow separation prediction using state-of-the-art turbulence models. Computational fluid dynamics simulations were conducted on the T106 turbine cascade blade geometry using OpenFOAM. Different turbulence models, including explicit algebraic stress models, were assessed and compared to classical models like Spalart-Almaras at Reynolds numbers of 60,000 and 150,000. At the lower Reynolds number, the φ-α-EASM model showed better agreement with experiments and DNS for attached flow regions, but failed to predict separation. Laminar simulations provided better separation prediction due to the low Reynolds number.
Centrifuge Testing to Evaluate Seismic Soil-Structure-Interaction and Lateral...Miguel Frias
The document describes centrifuge testing conducted to evaluate seismic soil-structure-interaction and lateral earth pressures near buried water reservoir structures in Southern California. The testing aims to compare the reliability of different pressure sensing technologies in capturing static lateral earth pressures on a simple retaining wall structure. Previous research found obtaining reliable pressure measurements is difficult in a centrifuge environment due to scaling laws. A series of static tests were conducted using Nevada sand backfill and various sensors, including tactile pressure sensors, to test the hypothesis that tactile pressure sensors can provide reliable pressure data in this environment. Soil testing including sieve analysis, specific gravity tests, and pluviation tests were performed to characterize the Nevada sand and calibrate the sensors.
This document contains draft lecture notes on fracture mechanics. It covers several topics:
1) Finite element models for progressive failures using continuum mechanics approaches like plasticity and damage mechanics.
2) An introduction to linear elastic fracture mechanics, including modes of failure, stress intensity factors, and elasticity-based solutions for cracked bodies.
3) Design examples using principles of linear elastic fracture mechanics to assess fracture properties of materials and calculate stress intensity factors.
4) A section on Griffith's theoretical derivation of the strength of solids based on the energy required to create a unit area of new crack surface.
This document summarizes Luigi Gigliotti's 2012 master's thesis which assessed the applicability of the extended finite element method (XFEM) in Abaqus software for modeling crack growth in rubber materials. The thesis first reviewed rubber elasticity, fracture mechanics of rubber, and XFEM. It then formulated static and dynamic analysis problems to evaluate XFEM's ability to model stress/displacement fields and predict crack propagation instant, direction, and speed using neo-Hookean and Arruda-Boyce material models. Results showed XFEM accurately modeled displacement fields but provided no benefits over FEM for stress fields. Difficulties were faced achieving convergence for dynamic analyses. The thesis aimed to help
This document provides recommendations for fatigue design of welded joints and components. It was prepared by the Joint Working Group XIII-XV of the International Institute of Welding and is a revision of previous documents from 1996 and 2002-2007. The document contains contributions from various professors and experts in the field and provides guidelines on determining fatigue actions, fatigue resistance of welded joints, and assessing joints with weld imperfections over multiple chapters and sections. Suggestions to further refine the document can be sent to the chairman.
This document presents a two-rod model to simulate the swing of a golf club. The two-rod model treats the arm and club as two rigid rods connected by a joint representing the wrist. The model calculates the torque applied by the arm and wrist during the swing using Lagrangian mechanics. Numerical solutions of the two-rod model are presented to simulate the clubhead velocity and trajectory for different swing parameters and conditions. Aerodynamic forces on the golf ball and equations to calculate the flight trajectory are also described. The document concludes by outlining a golf simulator software based on the two-rod model and ball flight equations.
This document appears to be an exam paper for physics. It consists of 12 printed pages and contains 11 multi-part questions testing various concepts in physics. The questions cover topics such as springs, motion, forces, gases, temperature measurement, optics, sound, electricity and circuits.
The document describes a numerical simulation of flow through a centrifugal pump impeller. Hassan Adel Talaat El-Sheshtawy conducted 3D CFD simulations using ANSYS/CFX to analyze the flow field and evaluate the slip factor. The simulation results agreed well with the design performance curve, especially near the best efficiency point. Several empirical slip factor correlations were compared to the numerically obtained slip factor. The effects of adding splitters and increasing the number of blades on slip factor, head rise and hydraulic efficiency were also investigated. It was found that while slip factor improved with more blades or longer splitters, hydraulic efficiency did not always increase due to additional losses.
This thesis experimentally and analytically investigates the buckling behavior of graphite/polyimide sandwich panels under edgewise compression loading. Material properties of the panel constituents were determined through flatwise tension and sandwich beam flexure tests. Buckling specimens of varying core thicknesses were tested to investigate failure modes. Specimens with the thinnest core failed by overall buckling near analytical predictions, while thicker cores failed by face wrinkling. Several buckling formulas for wrinkling were found to be unconservative. Recommended wrinkling equations are presented based on the test results. In conclusion, the buckling behavior of the graphite/polyimide sandwich panels was characterized experimentally and compared favorably to analytical predictions.
This thesis examines shallow gas anomalies in the North Sea using AVO analysis and seismic inversion. The author creates a wedge model to estimate the thickness of a thin gas sand detected at 520ms that shows high amplitudes on seismic data. AVO cross-plotting shows the anomaly deviates from the background trend into quadrant III, indicating a Class III gas effect. Tuning curves from the wedge model suggest the anomaly is affected by both gas saturation and tuning effects. Seismic inversion enhances interpretation by showing anomalous low impedance associated with the high amplitude anomaly.
This dissertation applies a modified statistical dynamical diffraction theory (mSDDT) to analyze high-resolution x-ray diffraction (HRXRD) data from C-doped Si and SiGe heterostructures. The mSDDT improves upon previous statistical dynamical diffraction theory by incorporating weighted and layered broadening effects to better model defective and partially relaxed materials. Experimental HRXRD scans of SiGe samples are fitted using mSDDT and compared to commercial software. The results demonstrate mSDDT's ability to quantitatively characterize relaxed and defective semiconductor structures through non-destructive metrology.
MSc_Thesis_Wake_Dynamics_Study_of_an_H-type_Vertical_Axis_Wind_TurbineChenguang He
This thesis investigates the wake dynamics of an H-type vertical axis wind turbine using particle image velocimetry (PIV). Two-component PIV is used to study vorticity shedding and horizontal wake expansion at the turbine mid-span plane. Stereoscopic PIV is performed on 7 cross-stream vertical planes to analyze tip vortex dynamics and the evolution of 3D wake structures. The experimental results show asymmetrical vorticity decay in the horizontal plane, with faster decay on the leeward side. Tip vortices are stronger than shed vortices. Near the turbine axis, tip vortices move inboard behind the rotor before moving outboard towards the windward side further downstream. Vertical
This masters project report describes molecular dynamics simulations performed to study liquid crystals and their potential use in biosensors. Over 50 nanoseconds of simulations were carried out using different atomistic force fields to model the liquid crystal 5CB. The force fields were characterized and compared to experimental data on the phase behavior and properties of bulk 5CB. Simulations were also conducted to study 5CB interactions across water interfaces and observe conformational changes in polypeptides to assess the ability to predict protein structure changes relevant for biosensor applications. Issues encountered are discussed. The work aims to further understanding of liquid crystals at the molecular level to aid the development of liquid crystal-based biosensing technologies.
This document describes a thesis presented by Durlav Mudbhari to Lehigh University for a Master of Science degree in mechanical engineering. The thesis involved designing and developing an experimental setup to measure unsteady forces and power of functionally graded, chordwise flexible wings. A flapping wing system was created with rigid and flexible regions to model functionally graded materials. Experiments were conducted in a wind tunnel and vacuum chamber to measure thrust production, lift/drag forces, and power consumption of wings with varying flexibility. The goal was to better understand how non-homogeneous flexibility impacts wing performance. Potential applications include more efficient autonomous underwater vehicles and ship propulsion through flexible hydrofoils.
Analysis of Ferrocement and Textile Reinforced Concrete for Shell StructuresMile Bezbradica
This document is Mile Bezbradica's master's dissertation which analyzes the stiffness properties of ferrocement, glass fiber textile, and carbon fiber textile for concrete shell structures. Three analysis strategies were used: an analytical model, experimental beam prototypes, and numerical analysis. Comparison of mechanical experiments to numerical models showed stiffness deviations of 38% for ferrocement, 272% for glass fiber, and 211% for carbon fiber beams. Ferrocement was stiffest in experiments but carbon fiber was stiffest in analytical and numerical models. The disparity between numerical and experimental results makes the overall comparison inconclusive. Future research should focus on material properties, numerical modeling assumptions, and construction techniques.
This document presents a numerical lifting line model and blade element model to model the aerodynamic effects of a propeller slipstream on a finite wing. The lifting line model uses a numerical vortex lattice method to predict lift distributions across a wing based on 2D airfoil data and known upstream flow conditions. The blade element model uses momentum theory and blade element analysis to model propeller performance and generate upstream velocity profiles. The combined models are expected to be useful for modeling tail-sitting VTOL aircraft where the propeller slipstream affects wing performance. Results are presented comparing the models to experimental data.
Internship Report: Interaction of two particles in a pipe flowPau Molas Roca
The present document sums up the development and results of the research internship carried out at LEGI Laboratory. The study aimed to understand the hydrodynamic forces involvement in the interaction between two red blood cells located in a capillary (pipe flow). The problem regarding Red Blood Cells (RBCs) moving through a capillary has been tackled from a two-dimensional point of view and has been both analytically and numerically outlined. Finite elements have been used to discretize the geometries considered. Several boundary conditions and geometries were simulated and deeply examined aiming to understand the mechanism governing hydrodynamic attraction and repulsion between red blood cells. The consequent results are analyzed in this report.
Modeling and Structural Analysis of a Wing [FSI ANSYS&MATLAB]BahaaIbrahim10
MODELING AND STRUCTURAL ANALYSIS OF A WING
WITH HISTORICAL PERSPECTIVE.
In our study, analyzing aircraft’s wing with the old assumptions will not give an exact solution but
this solution (total deformation) changes according to the geometry of the cross-section of the beam, so
the total deformation of the beam may be greater or lower than the exact solution. In these two cases,
the solution is not acceptable as in the first case which the deformation is greater than the exact solution
will make more weight and cost, and Engineers design aircraft at minimum weight and less cost. But in
the second case which will make lower deformation than exact solution will be much risky as the aircraft
could be fail at any time, and this case much dangerous because it threatens life of people.
This document is a report that analyzes replacing regular transmission line conductors with superconductors. It discusses the problems with current transmission lines, such as losses due to resistance, instability, and environmental/safety issues. The report proposes using superconducting cables cooled by liquid hydrogen in underground conduits as a solution. It evaluates the feasibility and costs/benefits of implementing this system compared to alternatives. The conclusion recommends superconducting cables as they would eliminate losses and provide a more efficient, reliable and environmentally friendly grid.
The document summarizes a numerical simulation of flow over a low-Reynolds-number flat plate airfoil with a passively actuated trailing-edge flap. Direct numerical simulation was performed at a Reynolds number of 1000 for a flat plate airfoil undergoing sinusoidal plunging motion and equipped with a 30% chord trailing-edge flap modeled as a spring-mounted pendulum. It was observed that the amplitude of flap oscillations increased as the natural frequency of the flap approached the plunging frequency, and negative average drag was produced when the natural frequency was lower than or equal to the plunging frequency. This trend differs from previous results at a higher Reynolds number and suggests the effects of viscosity or wing thickness differences are responsible for the discrepancy
SAIL VERSUS HULL FORM PARAMETER CONFLICTS IN YACHT DESIGNBoyang Wang
The document describes a student project that aims to analyze the influence of sail and hull form parameters on yacht performance. It will generate a series of hull forms by modifying parameters of an initial YD-40 hull. Resistance and stability of the hulls will be calculated and their performance tested using sailing simulation software for different sail configurations. The document reviews methods for hull form modification, section mapping, resistance prediction, and stability analysis that will be used in the project.
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1. Thesis Report
On
ANALYSIS AND IMPROVEMENT OF JACKING SYSTEMS
FOR JACK-UP RIG
Submitted by
NG JUN JIE
U048851X
Department of
Mechanical Engineering
In partial fulfillment of the
requirements for the Degree of
Bachelor of Engineering
National University of Singapore
Session 2007/2008
1
2. SUMMARY
As the need for energy increases globally, explorers have went out deeper
and deeper into the ocean for oil and gas which forms the world’s main
energy source. Jack-up rigs, which is one of the offshore structures that is
used in today’s extraction of oil from the seabed, is being analyzed.
This paper attempts to provide an insight to improving the fatigue life of the
lifting mechanism which comprises of the rack and pinion of a jack-up rig
by reducing the mean stress.
A practical model of a rack and pinion in a jack-up rig is modeled using
CAD and simulations are run on the model using finite element method
programs. The strength of the structure would be evaluated according to the
analysis results.
A study of the optimum fillet radius for the contact stress between the rack
and pinion is proposed which helps in reducing the fatigue failures by cyclic
loading of jack-ups.
i
3. Acknowledgement
The author wishes to express his sincere gratitude to his guide, A/P Mr. H.P Lee, for his
valuable guidance, proper advice and constant encouragement during the course or his
work on this project.
The author also feel very much obliged to his co-supervisor, Dr. X.M Tan, Research
Scientist at Institute of High Performance Computing for his encouragement and
inspiration for execution of the project work.
The author is deeply indebted to his parents for their inspiration and ever encouraging
moral support, which enabled him to pursue his studies.
The author is also very thankful to the entire faculty and staff members of Mechanical
Engineering Department for their direct–indirect help and cooperation.
ii
4. TABLE OF CO TE TS
Title Page umber
Summary ................................................................................ i
Acknowledgement ................................................................. ii
Table of Contents ................................................................. iii
List of Figures ........................................................................v
List of Tables ...................................................................... viii
1. Introduction .......................................................................1
1.1 Thesis Outline ...........................................................2
2. Literature Review ..............................................................2
2.1 Jack-up Rigs .............................................................2
2.2 Types of Jack-up Units .............................................3
2.3 Types of Leggings.....................................................4
2.4 Modes of Operations in a Jack-up .............................5
2.4.1 Afloat Transit Mode .....................................6
2.4.2 Preload Mode ...............................................7
2.4.3 Elevated Mode .............................................8
2.5 Lifting Mechanism – Rack and Pinion ......................8
2.6 Failures of Jack-up Rigs ............................................9
2.6.1 Failure of Jack-up Rigs by Fatigue .............10
iii
5. 2.6.2 Stress Reduction by Use of Fillets ...............12
3. Problem Definition ..........................................................13
3.1 Implementation .......................................................14
4. Numerical Investigation...................................................14
4.1Mesh sensitivity .......................................................14
4.1.1 Results ........................................................15
4.2 FEM model .............................................................16
4.3 Boundary Conditions ..............................................21
4.3.1 Displacement ..............................................22
4.3.2 Pressure.......................................................23
4.3.3 Contact........................................................24
4.4 Material ..................................................................25
5. Results .............................................................................26
5.1 Stress against Fillet Radius .....................................26
5.2 Plastic Strain against Fillet Radius ...........................32
5.3 Displacement against Fillet Radius ..........................38
6. Conclusion.......................................................................44
7. Recommendations ...........................................................45
8. References .......................................................................46
iv
6. List of Figures
1. Different working depths of offshore units.
2. Photograph of an offshore Jack-up in operation.
3. Top plane diagrams of (a) 4-legged jack-ups (b) 3-legged jack-ups.
4. Photographs of (a) cylindrical legs (b) truss legs.
5. Photograph of (a) Jack-up with legs retracted. (b) Jack-up under tow
(c) Jack-up on a loading vessel, accompanied by supporting towboats.
6. Photograph of a Jack-up Rig under preload conditions.
7. Diagram of a Jack-up Rig under transition.
8. Photograph of a Rack and Pinion system.
9. Case Histories classified according to causes of failures.
10. Causes of Jack-up Rigs During period of 1979 to 1988.
11. Schematic diagram of contact of pinion and rack with varying fillet radius.
12. Diagram of the changes in mesh sensitivity (a) Mesh = 0.015 (b) Mesh
=0.075 (c) Mesh =0.025 (d) Mesh =0.00125.
13. Table and Graph of Stress against Mesh Size.
14. Different views of rack model.
15. Different views of pinion model.
16. Different views of Rack and Pinion Configuration.
17. Comparison of Model with and without Fillets.
18. The pinion is constrained in all the three directions.
v
7. 19. The rack’s top and bottom is constrained in the x and y directions.
20. The rack’s side is constrained in the x direction.
21. Bottom elements are given pressure.
22. (a) Slave nodes of the rack (b) Master nodes of the pinion.
23. Overview of contact surface of the model.
24. Stress Variation in Rack and Pinion when fillet radius, r = 0mm.
25. Stress Variation in Rack and Pinion when fillet radius, r = 2.5mm.
26. Stress Variation in Rack and Pinion when fillet radius, r = 5mm.
27. Stress Variation in Rack and Pinion when fillet radius, r = 6.25mm.
28. Stress Variation in Rack and Pinion when fillet radius, r = 6.875mm.
29. Stress Variation in Rack and Pinion when fillet radius, r = 7.2mm.
30. Stress Variation in Rack and Pinion when fillet radius, r = 7.5mm.
31. Stress Variation in Rack and Pinion when fillet radius, r = 8.125mm.
32. Stress Variation in Rack and Pinion when fillet radius, r = 8.75mm.
33. Stress Variation in Rack and Pinion when fillet radius, r = 10mm.
34. Graph of Stress Against Fillet Radius.
35. Plastic Strain Variation in Rack and Pinion when fillet radius, r = 0mm.
36. Plastic Strain Variation in Rack and Pinion when fillet radius, r = 2.5mm.
37. Plastic Strain Variation in Rack and Pinion when fillet radius, r = 5mm.
38. Plastic Strain Variation in Rack and Pinion when fillet radius, r = 6.25mm.
39. Plastic Strain Variation in Rack and Pinion when fillet radius, r =
6.875mm.
vi
8. 40. Plastic Strain Variation in Rack and Pinion when fillet radius, r = 7.2mm.
41. Plastic Strain Variation in Rack and Pinion when fillet radius, r = 7.5mm.
42. Plastic Strain Variation in Rack and Pinion when fillet radius, r =
8.125mm.
43. Plastic Strain Variation in Rack and Pinion when fillet radius, r = 8.75mm.
44. Plastic Strain Variation in Rack and Pinion when fillet radius, r = 10mm.
45. Graph of Plastic Strain against Fillet Radius.
46. Displacement Variation when fillet radius, r= 0mm.
47. Displacement Variation when fillet radius, r= 2.5mm.
48. Displacement Variation when fillet radius, r= 5mm.
49. Displacement Variation when fillet radius, r= 6.25mm.
50. Displacement Variation when fillet radius, r= 6.875mm.
51. Displacement Variation when fillet radius, r= 7.2mm.
52. Displacement Variation when fillet radius, r= 7.5mm.
53. Displacement Variation when fillet radius, r= 8.125mm.
54. Displacement Variation when fillet radius, r= 8.75mm.
55. Displacement Variation when fillet radius, r= 10mm.
56. Graph of Displacement Against Fillet Radius.
vii
9. List of Tables
1. Results of mesh element size and corresponding highest stress.
2. Table of property of steel
3. Table of Results of Fillet radius and Stress
4. Table of Results of Fillet radius and Strain
5. Table of Results of Fillet radius and Displacement
viii
10. 1. Introduction
The continuously rising oil price has been driving oil companies to put increasingly more
efforts in exploring and producing oil from the sea. The demand for oil has pushed
explorers to venture deeper and deeper into the ocean. There are now a lot of facilities
used for the extraction of oil from the seabed. They vary from Jack-ups to drill ships.
They are used in different environments and they are used for different sea depths. Figure
1 illustrates further on the different working depths of the mobile offshore units.
Fig 1: Different working depths of offshore units
Jack-up rigs are capable of working in sea depths up to 400ft (121m). For
semisubmersible rigs, they usually work up to a depth of 3280ft (1000m) [9]. Lastly,
drillships are usually used in very deep waters to extract oil from the seabed.
Jack-up rigs are mobile and they would be towed from one place to another after the
original oil site has either low production and cannot meet the demand or it is no longer
commercially profiteering to produce from that well. The legs of the jack-up would
1
11. retract and extended during the transition. The upwards and downwards linear motion of
the lifting mechanism- the rack and pinion, would be experiencing stress repeatedly. It is
then proposed through the chamfering of the rack edges, to reduce the maximum contact
stress and thus increasing its fatigue life.
The purpose of this project is to conduct a parametric study of the relationship between
highest contact stress and the fillet radius of the rack edge.
1.1. Thesis Outline
Chapter 2 provides an introduction to the jack-up rig and some of the causes of failures
that offshore mobile units undergo. The chapter also goes through some of the past
statistics of jack-up rigs failures and its causes. Chapter 3 presents the problem of the
prevailing jack-up rigs and the numerical approach to solve for the optimum solution.
Chapter 4 shows the lifting mechanism which the rack and pinion is being developed into
a CAD model. It also presents the boundary conditions used in the simulation of real
environmental loads as well as the material properties. Chapter 5 presents the findings of
the simulations. Chapter 6 gives the conclusion of the study done. Lists of
recommendations are made in Chapter 7.
2. Literature Review
2.1 Jack-ups Rigs
Jack-up rigs are used in the exploration of oil since the 1950’s. They have been used for
exploration drilling, tender assisted drilling, production, accommodation, and work or
maintenance platforms. [1]
2
12. A Jack-up rig is an offshore structure composed of a hull, legs and a lifting system that
allows it to be towed to a site, lower its legs into the seabed and elevate its hull to provide
a stable work deck capable of withstanding the environmental loads.
Jack-up rigs are used because they can be towed to another oil well after the well
production no longer can produce the required demand. A fixed platform would be
similar to a jack-up rig just that it is only built at that particular worksite and cannot be
moved. Jack-up rigs are thus more expensive to build than a fixed platform.
(b)
(a)
Fig 2: Photograph of an offshore Jack-up in operation
2.2 Types of Jack-up Units
There are typically 3-legged and 4-legged jack-ups in the world today. However the
majority of the jack-ups that are produced are 3 legged. [1]
The advantages of 4-legged jack-ups are that they have more work space as they require
no preload tankage and they are usually stiffer in the elevated mode because of the extra
leg. It is also because of the extra leg that the jack-up would experience additional wind,
3
13. current and wave conditions. In the afloat transit mode, the jack-up would also have a
greater draught due to the weight of the additional leg.
The 3-legged jack-ups on the other hand weighs lesser for a given hull size and can carry
more load. They also eliminate the construction of an additional leg, thus reducing the
number of lifting mechanism (racks, pinions, etc). This helps to reduce the power and
maintenance requirements. However unlike 4-legged jack-ups they require preload tanks
onboard which take up usable space.
(a) (b)
Fig 3: Top plane diagrams of (a) 4-legged jack-ups (b) 3-legged jack-ups
2.3 Types of Leggings
There are two main types of leggings: cylindrical and trussed.
Cylindrical Legs are made up of hollow steel tubes. They may be fitted with rack and
pinions or holes in the shell to allow jacking up or down of the hull. They belong to an
older class of jack-ups rigs and they are used in water depths less than 300 ft. The main
advantage of using cylindrical legs is that it is smaller in cross-section and takes up less
deck space.
The newer jack-up units are equipped with truss legs as they are lighter and use less
material whilst providing the same resistance to the environmental loads. For the truss
4
14. legs to be able to match the strength of the cylindrical legs, one must carefully consider
its flexural and axial strength of the trusses’ chords and braces.
(a) (b)
Fig 4: Photographs of (a) cylindrical legs (b) truss legs
2.4 Modes of Operations of a Jack-up
There are basically 3 types of modes a jack-up would experience when transiting from an
work site to another. They are the afloat transit mode, preload mode and the elevated
mode.
2.4.1 Afloat Transit Mode
When the hull of a jack-up is lowered from its elevated mode, the legs are retracted and
they leave the seabed. It is not necessary to full retract the legs as long as they have
enough clearance from the seabed. This would increase stability of the jack-up and
reduces the risk of wind overturning. The jack-up floats on the sea on its own hull and it
5
15. is towed by several towboats to the location. In some other cases, the jack-up unit is
brought up onto the deck of another vessel. In this case, the legs of the jack-up unit must
be retracted to the maximum before loading onto the loading vessel.
(a) (b)
(c)
Fig 5: Photograph of (a) Jack-up with legs retracted. (b) Jack-up under tow
(c) Jack-up on a loading vessel, accompanied by supporting towboats.
2.4.2 Preload Mode
The jack-up unit has to be preloaded to simulate operating conditions. In this mode, the
hull is jacked up slowly to a height no more than 5 feet above the sea level. By pumping
in seawater from the surroundings to the onboard preload tanks, the hull carries extra
weight apart from its own weight. In this mode, there are chances that a leg shift or soil
failure might occur. If that happens, the jack-up would lose its balance, dropping its hull
6
16. into the water. The consequences are kept to a minimal as the hull is near the water, thus
reducing the wave impact.
For the 4-legged jack-up rigs, there is little or no preload water. It is usually done by
preloading 2 of its diagonally opposite legs by the weight of the hull itself. After settling
occurs, the 2 legs are lifted slightly to bring the other 2 legs to its preload period. After
the 4 legs are settled, the hull is then brought up to its operating height.
Fig 6: Photograph of a Jack-up Rig under preload conditions
2.4.3 Elevated Mode
Once the hull is in the operating height, the brakes are set and its weight lies fully on the
strength of the legs. The jack-up rig is ready to begin operations. Figure 7 illustrates the
various modes of operation from arriving at the oil site to operational mode.
7
17. Fig 7: Diagram of a Jack-up Rig under transition
2.5 Lifting Mechanism – Rack and Pinion
All Jack-ups have mechanisms for lifting and lowering the hull. Majority of Jack-ups are
equipped with a Rack and Pinion system for continuous jacking operations. The power
sources used for jacking include both electric and hydraulic. Figure 8 shows a typical
rack and pinion system found on a jack-up rig.
8
18. Fig 8: Photograph of a Rack and Pinion system
One point to take note is that the cross-sectional thickness of the pinion is usually larger
than the thickness of the rack. This is to prevent slipping of the rack off the pinion.
2.6 Failure of Jack-up Rigs
According to a report by MSL Engineering Ltd prepared for Health and Safety Executive
in 2004, 53% of the failures that jack-up rigs experiences is due to punch through of the
legs. Other causes include uneven seabed, volcanic activities, unexpected penetration of
the legs, sliding of mat foundation and mudslide.
9
19. Fig 9: Case Histories classified according to causes of failures
2.6.1 Failure of Jack-up Rigs by Fatigue
In high cycle fatigue situations, materials performance is normally characterized by the
S-N curve. The graph depicts of a cyclical stress(S) against cycles to failures (N). Failure
due to repeated loading is called fatigue.
Fatigue failures are often caused by the degradation of metal surface. A rough surface
finish, a scratch or oxidation will provide an initial crack. Cracks will propagate after
cyclical loading and eventually lead to fatigue failure.
10
20. The factor that determines fatigue failure is mean stress. As the mean stress decreases, the
fatigue life increases. The defects on the contact surface will cause a decrease in the life
of a material. As such, sharp corners which stresses concentrate on will probably be the
first where cracks will occur and propagate.
In another paper by B. P. M. Sharpies, W. T. Bennett, Jr and J. C. Trickey, it spoke of the
failures that jack-up rigs experience due to a certain factor during the period 1979 to 1988.
Fatigue was one of the factors with 13 accidents out of the 226 accidents that occurred
during this period.
11
21. Fig 10: Causes of Jack-up Rigs During period of 1979 to 1988
2.6.2 Stress Reduction by Use of Fillets
Gears develop high stress concentration at the gear tooth root stress and the contact point.
It is usually at these areas where there is a higher chance of fatigue failure. In normal
operations the contact point shifts along the profile of the tooth and a surface fatigue
failure is likely. In the normal jack up operation, the rack and pinion is held in place after
the hull is at its operational height. In this case, the contact point between the rack and
pinion will stay in one place for an extended period of time. This is when the relief
features are needed to reduce the highest stress at the contact point. Fatigue life will be
increased if fillets are introduced at the contact point.
Vasilios [21] introduces another method to find the minimum fillet stress using BEM and
further verification has been done using 2D photoelasticity. Math [20] proposes an
approach to determine the geometry of the spur gear tooth fillet. Equations have been set
up for the tangency of the involute curve and root fillet.
12
22. 3. Problem Definition
The hull is supported by the Jack-up’s lifting mechanism; the consequences would be
catastrophic if the rack and pinion were to fail by fatigue. In recurring instances of
jacking up and down the legs due to its mobile nature, the rack and pinion experiences
repeated contact stress at sharp corners, especially at the edges of the rack. The cyclic
nature of loading and unloading the hull causes the rack to fail possibly by fatigue.
Therefore, it is paramount that the rack and pinion has relief features in areas where the
highest stress occurs. Presently there are no studies on this aspect of study. This is a new
area of study to look into. It could have possible tremendous positive impacts if this were
to be put into practice in the offshore industry. The relief fillet causes a lower distributed
stress at the edges. The chamfering of the edges of the rack at the contact surface gives
the rack a longer fatigue life. It is then proposed to investigate the relationship between
the fillet radius and its corresponding stress level at the point of contact to find an
optimum fillet radius for the rack.
Highest Highest
stress stress
Fig 11: Schematic diagram of contact of pinion and rack with varying fillet radius
The highest stress is found at the sharp corners of the rack. The rationale of the
simulation is that by chamfering the edges, the highest stress is reduced by distributing
13
23. the stress around the fillet radius. However with larger fillet radius, the area of contact of
the rack with the pinion is reduced. There is a point where the highest stress will start to
increase with larger fillet radius. The aim of this simulation is to find out the optimum
fillet radius.
3.1. Implementation
Software used: -
Modeling using Solidworks 2005, transferring of coordinates to MSC Patran 2005r3 and
analysis is done using Abaqus Version 6.41.
4. umerical Investigation
4.1 Mesh Sensitivity
A study of varying element size on the rack surface has been done for convergence
purposes. This study is done on the purpose that the computational result does not deviate
too much from the actual stress. The convergence test is done on a single model.
Mesh size (mm) HighestStress (Pa)
0.00125 7.55E+08
0.0025 7.53E+08
0.0075 7.36E+08
0.015 7.10E+08
Table 1: Results of mesh element size and corresponding highest stress
14
24. (a) (b)
(c) (d)
Fig 12: Diagram of the changes in mesh sensitivity (a) Mesh = 0.015 (b) Mesh =0.075
(c) Mesh =0.025 (d) Mesh =0.00125
4.1.1 Results
The results of convergence are shown in the form of a table and graph shown below.
15
25. Graph of Stress against Mesh Size
8.00E+08
7.50E+08
Stress, σ (Pa))
7.00E+08
6.50E+08
6.00E+08
5.50E+08
5.00E+08
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016
Mesh Size (mm)
Fig 13: Table and Graph of Stress against Mesh Size
The graph above shows the variation of element size and its corresponding stress. It
shows that even after the element size has been halved to 0.00125, the stress deviate from
the previous stress by less than 1%. Thus it would be more computationally expensive to
use element size of 0.00125 and below. It would be fairly accurate to use element size of
0.0025 in area of analysis.
4.2 FEM model
The model is based on a practical Rack and Pinion that is in a commercial Jack-up. The
original Rack and Pinion has been cut into half since it is symmetrical about its central
plane.
The rack is modeled and meshed as shown in Figure 15. Similarly the pinion can be
found in Figure 16. The final rack and pinion configuration is shown in Figure 17.
Finally, a contrast is shown between a rack with and without fillets in Figure 18.
16
26. The FEM model is made up of all solid tetrahedral elements.
17
30. Fig 16: Different views of Rack and Pinion Configuration
Fig 17: Comparison of Model with and without Fillets
4.3 Boundary Conditions
The model has boundary conditions like displacement, pressure and contact.
21
31. 4.3.1 Displacement
Firstly the pinion is given the boundary condition that the inner bore is constrained in all
the 3 directions. Figure 19 shows the boundary condition given to the pinion.
Fig 18: The pinion is constrained in all the three directions
22
32. Fig 19: The rack’s top and bottom is constrained in the x and y directions
Fig 20: The rack’s side is constrained in the x direction
4.3.2 Pressure
The rack is given an upwards pressure of 1 kipf/sq in (6.89 MPa) and is applied at the
bottom surfaces of bottom elements.
23
33. Fig 21: Bottom elements are given pressure
4.3.3 Contact
The surface of the rack has slave nodes and the surface of the pinion has master nodes in
defining the contact. A friction coefficient of 0.1 is being applied here.
(a) (b)
Fig 22: (a) Slave nodes of the rack (b) Master nodes of the pinion
24
34. Fig 23: Overview of contact surface of the model
4.4 Material
All the models are given the property of steel. The properties of steel are presented in a
form of graph below.
Properties of Steel
Elastic Modulus 2e11 Pa
Poisson Ratio 0.3
Density 7850 kg/m3
Yield Stress 7.24e8 Pa
Table 2: Table of property of steel
25
35. 5. Results
The results of the simulations can be summarized into the following: Stress variation
against fillet radius, plastic strain against fillet radius and displacement against fillet
radius.
5.1 Stress Variation against Fillet radius
The following results are presented in the form of pictures shown below.
Fig 24: Stress Variation in Rack and Pinion when fillet radius, r = 0mm
26
36. Fig 25: Stress Variation in Rack and Pinion when fillet radius, r = 2.5mm
Fig 26: Stress Variation in Rack and Pinion when fillet radius, r = 5mm
27
37. Fig 27: Stress Variation in Rack and Pinion when fillet radius, r = 6.25mm
Fig 28: Stress Variation in Rack and Pinion when fillet radius, r = 6.875mm
28
38. Fig 29: Stress Variation in Rack and Pinion when fillet radius, r = 7.2mm
Fig 30: Stress Variation in Rack and Pinion when fillet radius, r = 7.5mm
29
39. Fig 31: Stress Variation in Rack and Pinion when fillet radius, r = 8.125mm
Fig 32: Stress Variation in Rack and Pinion when fillet radius, r = 8.75mm
30
40. Fig 33: Stress Variation in Rack and Pinion when fillet radius, r = 10mm
Fillet radius r, mm Stress x108 , Pa
0.000 7.53
2.500 7.20
5.000 7.10
6.250 6.98
6.875 6.95
7.200 6.99
7.500 7.01
8.125 7.06
8.750 7.11
10.000 7.19
Table 3: Table of Results of Fillet radius and Stress
The highest stress from the diagrams is presented in a form of graph shown below.
31
41. Stress Against Fillet Radius
7.6
7.5
Stress, σ (Pa) x108
7.4
7.3
7.2
7.1
7
6.9
0 2 4 6 8 10 12
Fillet Radius, r (mm)
Fig 34: Graph of Stress Against Fillet Radius
5.2 Plastic Strain against Fillet Radius
The following pictures depict the plastic strains that are found by the edges of the rack.
Fig 35: Plastic Strain Variation in Rack and Pinion when fillet radius, r = 0mm
32
42. Fig 36: Plastic Strain Variation in Rack and Pinion when fillet radius, r = 2.5mm
Fig 37: Plastic Strain Variation in Rack and Pinion when fillet radius, r = 5mm
33
43. Fig 38: Plastic Strain Variation in Rack and Pinion when fillet radius, r = 6.25mm
Fig 39: Plastic Strain Variation in Rack and Pinion when fillet radius, r = 6.875mm
34
44. Fig 40: Plastic Strain Variation in Rack and Pinion when fillet radius, r = 7.2mm
Fig 41: Plastic Strain Variation in Rack and Pinion when fillet radius, r = 7.5mm
35
45. Fig 42: Plastic Strain Variation in Rack and Pinion when fillet radius, r = 8.125mm
Fig 43: Plastic Strain Variation in Rack and Pinion when fillet radius, r = 8.75mm
36
46. Fig 44: Plastic Strain Variation in Rack and Pinion when fillet radius, r = 10mm
Fillet radius r, mm Plastic Strain x10-2
0.000 6.92
2.500 5.00
5.000 4.66
6.250 4.21
6.875 4.13
7.200 4.17
7.500 4.23
8.125 4.43
8.750 4.68
10.000 4.98
Table 4: Table of Results of Fillet radius and Strain
37
47. Plastic Strain Against Fillet Radius
8
7
Plastic Strain x10 -2
6
5
4
3
2
1
0
0 2 4 6 8 10 12
Fillet Radius, r (mm)
Fig 45: Graph of Plastic Strain against Fillet Radius
5.3 Displacement against Fillet Radius
This simulation serves as a preliminary study of displacement. The following shows the
results of varying fillet radius against displacement. Figure 54 shows the graph of the
displacement and fillet radius.
38
48. Fig 46: Displacement Variation when fillet radius, r= 0mm
Fig 47: Displacement Variation when fillet radius, r= 2.5mm
39
49. Fig 48: Displacement Variation when fillet radius, r= 5mm
Fig 49: Displacement Variation when fillet radius, r= 6.25mm
40
50. Fig 50: Displacement Variation when fillet radius, r= 6.875mm
Fig 51: Displacement Variation when fillet radius, r= 7.2mm
41
51. Fig 52: Displacement Variation when fillet radius, r= 7.5mm
Fig 53: Displacement Variation when fillet radius, r= 8.125mm
42
52. Fig 54: Displacement Variation when fillet radius, r= 8.75mm
Fig 55: Displacement Variation when fillet radius, r= 10mm
43
53. Fillet radius r, mm Displacement x10-3 , mm
0.000 1.89
2.500 1.71
5.000 1.69
6.250 1.55
6.875 1.55
7.200 1.56
7.500 1.58
8.125 1.59
8.750 1.60
10.000 2.00
Table 5: Table of Results of Fillet radius and Displacement
Displacement Against Fillet Radius
2.5
Displacement (mm) x10 -3
2
1.5
1
0.5
0
0 2 4 6 8 10 12
Fillet Radius, r (mm)
Fig 56: Graph of Displacement Against Fillet Radius
6. Conclusion
From this study, we have found out an optimum fillet for the edges of the rack. It can be
concluded from the studies that a fillet radius of 6.875mm is the optimum radius. It
shows that with fillet radius of 6.875mm would yield the lowest stress of 6.95e8 Pa. It
means there is a reduction of about 7.7% in contact stress compared with the rack that is
44
54. without the fillets. The plastic strains are also the lowest when the fillet radius is
6.875mm. The maximum displacements are near the applied pressure and they are found
at the places where there is the least deformation. At fillet radius of 6.875mm and
6.25mm, the rack and pinion exhibits the least displacement.
All of the results that are exhibited are static stresses produced from constant loads. In
actual operation, the rack and pinion experiences dynamic loads variations. However the
dynamic loads will be small as the rotational speed of the pinion will be slow when
elevating the hull. For actual determination of the stresses, programs that are able to
calculate dynamic loads are suggested, for instance LS-DYNA.
7. Recommendations
In practical offshore industry, there is no record of filleting the edges of the rack.
However from this study, it shows that by chamfering the edges of the rack, one is able to
reduce the maximum contact stress, thus reducing mean stress. From there, the chances of
fatigue failure can be reduced too.
One recommendation is that instead of chamfering special fillet radius of 6.875mm which
requires precise machining, one can opt for common fillet radius like 6mm or even an
odd number 7mm which is close to the optimum fillet radius to reduce chances of fatigue
failure.
Another recommendation is that designers of jack-up rigs can indicate that in the
manufacture of the rack; to save cost, chamfer only the operational range. That is to say
only chamfer the range where the hull is in elevated mode. There is no need to chamfer
the whole rack as at full operational height of the hull would experience more cycles to
failure with real environment loads in times of storms.
45
55. 8. References
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1, 2005). “Jack up units: A technical primer for the offshore industry
professional.” Retrieved 23 Sep 2007, from
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Jackup Rigs.” Marine Structures, Vol. 2, pp. 281-303.
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Cheng-Chung Yen (2002), “Integration of Finite Element Analysis and Optimum
Design on Gear Systems”, Finite Elements in Analysis and Design, Vol. 38, pp.
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http://www.keppelfels.com.sg/products
46
56. 10) Litvin, F.L (1996), “Application of Finite Element Analysis for Determination of
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47
57. 18) Shuyan Ji, Daizhong Su and Jiansheng Li (2006), “Gear Design Optimisation
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110–114.
48