Many soft food materials, including vegetable shortening, exhibit complex rheological behaviour with properties that resemble those of a solid and a liquid simultaneously. The fundamental parameters used to describe the rheological response of vegetable shortening were obtained from uniaxial compression tests, including monotonic and cyclic compression, as well as creep and stress relaxation tests. The fundamental parameters obtained from the various compression tests were then used in two mechanical models (viscoelastic and elasto-visco-plastic) to predict the compression and conical indentation response of vegetable shortening. The accuracy of the two models was studied with the help of the commercially available finite element analysis software package Abaqus. It was determined that the viscoelastic model was not suitable for the prediction of the rheological response of shortening. On the other hand, the proposed elasto-visco-plastic model predicted with reasonable accuracy the uniaxial compression and indentation experimental response of vegetable shortening.

Elevated intracranial pressure (ICP) in closed head injury may lead to a vegetative state and even death. Current methods available for measuring ICP may cause infection, haemorrhage or not reliable. A patient-specific correlation between ICP and an external vibration response was used for ICP evaluation, which based on finite element (FE) modeling. In FE modeling, a two dimensional FE model of human head was built in ANSYS. Geometry information was obtained from a magnetic resonance image of the human head, while the material properties were acquired from literatures. Vibration responses, e.g., displacement, velocity, acceleration and equivalent strain, were obtained for applied ICPs in FE analyses. Correlations between ICP and vibration responses were established. Effects of impact magnitude and impact duration were studied. Response sensitivity was defined to find a vibration response that is sensitive to ICP change. A procedure based on response sensitivity was proposed for ICP evaluation.

The thesis proposes a new procedure to describe bone anisotropy in the finite element model using computed tomography (CT) images. First, bone density was correlated to CT numbers using the empirical function established in previous studies; pointwise bone density gradient was then calculated from interpolation functions of bone densities. Second, principal anisotropic directions were defined using the bone density gradient. Third, the magnitude of bone density gradient was incorporated to an existing bone elasticity-density correlation established by experiments. A method was also introduced to assign the anisotropic material properties to finite element models in Abaqus. The effect on the predicted von Misses stresses and principal strains in the bone by adopting the anisotropic or isotropic material model was investigated by finite element simulations using Abaqus.

This dissertation reports investigations on shear in cracked reinforced concrete (RC) elements including the development and implementation of a material subroutine for the commercial finite element (FE) program ABAQUS. The material subroutine UMAT is intended to substantially improve the shear behaviour of the standard concrete options of ABAQUS. At first the important shear theories are reviewed in detail and their advantages and drawbacks are summarised. The modified compression field theory (MCFT) is identified as a suitable shear theory worth being coded for its application in FE analysis. A comprehensive check on the MCFT confirms its suitability in a slightly modified form for the investigation of a variety of cracked structural RC elements. This check is conducted on a section analysis level by means of a developed program called LAYER which is coded according to the MCFT. The main part of the work is the implementation and testing of the material subroutine UMAT which is added to the source code of ABAQUS via an interface provided by the commercial FE program. Finally, the UMAT is utilised for examining the ductility of RC walls. It is concluded that shear deflections can influence the displacement and curvature ductility of squat structures in a substantial way, even though a flexural type of failure might prevail.

No description available.

No description available.

The key to the co-rotational (CR) finite element is the separation between the rigid body motion and the deformational motion. It is this separation which makes it superior to other methods in the analysis of large displacement problems. Since the dynamic analysis of a guyed transmission line system contains large displacements from the vibration of the cable, it is considered appropriate to utilize the technique in the analysis. This thesis re-formulates and simplifies the CR method for such a purpose. Numerical tests show that the time step required for convergence in the present technique is ten times less than that is required for convergence in ANSYS. In the construction of the equation for the prediction of the longitudinal load factor (LLF) for the A402-M guyed transmission line due to cable break events, the tower is modelled using a simplified model of a detailed lattice tower. The simplified model considers latticed tower segment as an equivalent beam segment. The use of the simplified model enables to perform the broken wire dynamic analysis of the ten-span transmission line system within a day or two on a personal computer. Two initiating events are considered: all conductors on one arm break and all cables in one span break. Based on the analysis results, it is found that the LLFs for the all cables break event for the A402-M tower are 5% less than that calculated using the EPRI equation. It is therefore recommended that either the LLFs derived from the EPRI equation or from the proposed equation be used in the design of a guyed transmission tower for the broken wire event. The developed procedure can also be used to predict the LLF for the other type transmission line systems.

No description available.

The jaw musculature of Champsosaurus has been enigmatic since the taxon was first described. The extant phylogenetic bracketing method is used to determine the morphology of the jaw adductor musculature. Rotational mathematics is used to calculate the muscle forces, torques, angular accelerations, and angular velocities generated by the jaw muscles. The mechanical strength of the skulls of neochoristoderes and crocodilians are investigated using finite element analysis. Finally, the hydrodynamic performance of the skulls of neochoristoderes and crocodilians is studied. The analysis is used to compare neochoristoderes to their extant ecological analogues, crocodilians, and determine the palaeoecological implications of the results. It was found that Champsosaurus rotates the lower jaw faster, the mechanical strength was lower, and shows better hydrodynamic performance than crocodilians. The results suggest that Champsosaurus was ideally suited to prey upon small or juvenile fish, and did not overlap its niche with sympatric crocodilians. / Systematics and Evolution

Scoliosis is defined as the abnormal three dimensional curvature of the spine with 80% of all cases being idiopathic in nature. If left unchecked, this condition can cause cardio-pulmonary complications and occasionally death. Currently, the most common method of treatment of scoliosis is through mechanical bracing or in extreme cases, corrective surgery. Current treatments can be further improved with a greater understand of the growth patterns of scoliotic spines. The objective of this study is to develop a finite element spine model capable of responding to loading conditions in a similar fashion to previous finite biomechanics spine model and utilize the ‘vicious cycle’ scoliosis theory in an effort to model scoliosis growth. Using CT images of a healthy spine, a three dimensional finite element model of the L3-L4 vertebra is generated. Asymmetric loading due to compression and muscle forces can then be applied on the spine and the resultant stresses are then translated into equivalent thermal load. Using this thermal load, it is possible to cause the spine model to grow, thereby predicting the growth pattern of a spine due to asymmetric loading.