QSpace Community:http://hdl.handle.net/1974/7702016-04-29T06:06:13Z2016-04-29T06:06:13ZNonlinear Analysis of Directional MotionRASQUINHA, BRIAN Jhttp://hdl.handle.net/1974/143172016-04-28T22:12:10Z2016-04-28T04:00:00ZTitle: Nonlinear Analysis of Directional Motion
Authors: RASQUINHA, BRIAN J
Abstract: Directional data can be represented as unit vectors. This representation defines a nonlinear geometry, in which directions can be considered as points on the unit sphere. A consistent analysis of directional data would measure distances, calculate means, and describe variations along the surface of the sphere, rather than deviating from the surface using more common Euclidean measures.
Some nonlinear analysis methods developed for statistical shape models use a mapping from a nonlinear geometry to a linear tangent space, where familiar principal component analysis can be applied. In biomechanics, linear principal component analysis has been used to analyze directional motions encoded as high-dimensional points;
however, this approach does not account for the spherical structure of these data.
In this work, these concepts are combined in a novel motion analysis method, Nonlinear Analysis of Directional Motion. The method was applied to quasi-elliptical motions in a set of one-parameter simulations; it was also
applied to wrist circumduction of healthy subjects. The small-circle model, which fits circles smaller than the diameter of a sphere, was used as the comparative standard.
In simulation, the nonlinear method out-performed small-circle fitting using one component; this method also accurately captured the number of parameters of the data. Analyzing wrist circumduction, the method
produced a five-parameter model, with lower fitting error than the small-circle model after two components. Nonlinear directional analysis also described differences between clockwise and counter-clockwise senses of circumduction in these healthy subjects.
Nonlinear analysis of directional motion was demonstrated to provide an accurate model of circumduction with few parameters. This method may be useful for describing kinematic differences in any mechanism that has variable, multi-axial motion.
Description: Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2016-04-28 11:01:59.0142016-04-28T04:00:00ZNONLINEAR FINITE ELEMENT MODELING AND ANALYSIS OF METAL HOT FORMING FOR AUTOMOTIVE WEIGHT REDUCTIONForesi, Danielhttp://hdl.handle.net/1974/142842016-04-27T05:15:12Z2016-04-26T04:00:00ZTitle: NONLINEAR FINITE ELEMENT MODELING AND ANALYSIS OF METAL HOT FORMING FOR AUTOMOTIVE WEIGHT REDUCTION
Authors: Foresi, Daniel
Abstract: This research develops a methodology for three dimensional, multi-stage, large deformation, finite element contact analysis, which considers the effects of thermo-plasticity and austenite decomposition. The developed methodology is applied to the forming process of a transmission clutch hub which is constructed from UHSS 22MnB5 for the purpose of automotive lightweighting. The entire process chain is considered, including the hot stamping process, in which a high temperature blank enters a stamping press with actively cooled tooling. The press then forms the blank and remains closed, so as to cool the part rapidly enough to induce phase transformations in the material. The resulting part increases in strength by up to 250% during this process. This research focuses on simulating the entire multi-stage stamping process including cold formed stages but with the exception of piercing and trimming operations. The clutch hub is currently manufactured from 2.5mm thick HSLA and a transition to 1.5mm thick 22MnB5 is proposed. This would represent a 38% mass reduction if successful. Typically, 22MnB5 has been reserved for structural components, which have substantially less complex geometry than that of a typical transmission clutch hub, thereby increasing the complexity of the problem. Simulations including austenite decomposition were carried out using the non-linear finite element solver LS-DYNA. In order to validate the numerical models, three criteria were evaluated and compared to experimental data: material thickness, lubrication hole geometry, and Vickers hardness. It was found that the thickness distribution of the numerical model accurately represented the thickness distribution of the cold formed stage. The error in thickness estimation was 0.91% for the cold stage. Thickness change during the hot formed stage was only considered at the splines. The final geometry of the lubrication hole presented by the numerical model also closely resembled that of the experimental result: the error between the numerical and experimental model was 1.4% in the major diameter, where the primary stretching occurred. Finally, Vickers hardness values for both models were compared at 11 points distributed along the radial direction and the error was found to be an average of 13.5%.
Description: Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2016-04-25 20:56:18.6292016-04-26T04:00:00ZWRIST MOTION SIMULATION WITH A RIGID BODY SPRING MODEL COMPARING DIFFERENT ELEMENTS MODELING APPROACHESAlsanawi, Hishamhttp://hdl.handle.net/1974/142002016-04-09T20:15:39Z2016-04-08T04:00:00ZTitle: WRIST MOTION SIMULATION WITH A RIGID BODY SPRING MODEL COMPARING DIFFERENT ELEMENTS MODELING APPROACHES
Authors: Alsanawi, Hisham
Abstract: A rigid body spring model was used to simulate wrist motions. The carpal bones were constructed based on a computed tomography of a cadaver wrist. Bony structures were assembled as a wrist model in the simulation software, RecurDyn. Articulations between wrist joint bones were modeled using gliding surfaces, each was attached to its bone surface and this articulation was controlled by contact forces in the simulation software. Wrist ligaments were modeled by either one or two spring elements for each ligament or major component. Muscles of the wrist were represented by axial force elements. The force exerted by each tendon in each wrist movement was computed using either exponential function or sigmoid function in two different models. Each of these force functions were proportional to the distance between the simulation capitate and the capitate in the desired position. Capitate was chosen as tracking marker because the common center of rotation of wrist is within the capitate head.
Each of these approaches were simulated alone or with addition of a time factor. Eight wrist models were created. Each model simulated 34° extension, 57° extension, 30° flexion, 65° flexion, radial deviation and ulnar deviation. The root mean square error was calculated for linear and angular position for each carpal bone, each wrist movement, and for each model. The combined overall RMS errors for each model were calculated. The double spring ligament model with sigmoid force function considering time factor showed the least overall RMS error and most joint stability. The single spring ligament model with exponential force function without the time factor showed the highest RMS error and joint instability in some wrist motion simulations. The different modeling approaches used in this study helped in understanding the kinematics of the wrist joint and the wrist ligaments and tendons.
The results of this work encourage using these models for further kinematic studies in tandem with in vivo or in vitro studies for further validation. These models can be helpful in simulating non-physiological conditions of the wrist. Further work related to result validation using data from multiple wrists, further enhancements of ligaments and muscles modeling will improve the accuracy of these wrist models.
Description: Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2016-04-08 13:02:01.0412016-04-08T04:00:00ZCharacterization of hydrides and delayed hydride cracking in zirconium alloysFang, QIANGhttp://hdl.handle.net/1974/140882016-03-30T21:44:50Z2016-03-01T05:00:00ZTitle: Characterization of hydrides and delayed hydride cracking in zirconium alloys
Authors: Fang, QIANG
Abstract: This thesis tries to fill some of the missing gaps in the study of zirconium hydrides with state-of-art experiments, cutting edge tomographical technique, and a novel numerical algorithm. A new hydriding procedure is proposed. The new anode material and solution combination overcomes many drawbacks of the AECL hydriding method and leads to superior hydriding result compared to the AECL hydriding procedure. The DHC crack growth velocity of as-received Excel alloy and Zr-2.5Nb alloy together with several different heat treated Excel alloy samples are measured. While it already known that the DHC crack growth velocity increases with the increase of base metal strength, the finding that the transverse plane is the weaker plane for fatigue crack growth despite having higher resistance to DHC crack growth was unexpected. The morphologies of hydrides in a coarse grained Zircally-2 sample have been studied using synchrotron x-ray’s at ESRF with a new technique called Diffraction Contrast Tomography that uses simultaneous collection of tomographic data and diffraction data to determine the crystallographic orientation of crystallites (grains) in 3D. It has been previously limited to light metals such as Al or Mg (due to the use of low energy x-rays). Here we show the first DCT measurements using high energy x-rays (60 keV), allowing measurements in zirconium. A new algorithm of a computationally efficient way to characterize distributions of hydrides - in particular their orientation and/or connectivity - has been proposed. It is a modification of the standard Hough transform, which is an extension of the Hough transform widely used in the line detection of EBSD patterns Finally, a basic model of hydrogen migration is built using ABAQUS, which is a mature finite element package with tested modeling modules of a variety of physical laws. The coupling of hydrogen diffusion, lattice expansion, matrix deformation and phase transformation is investigated under striation crack growth conditions. The result is a progress in applying diffusion of H and crack propagation within a commercial finite element package.
Description: Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2016-02-26 08:25:27.6922016-03-01T05:00:00Z