No description available.

No description available.

No description available.

No description available.

Bone is porous and has a complex microstructure. This study considers the effect of microstructural morphology on the macrolevel mechanical properties of bone. Improved incorporation of such properties is required to advance current finite element approximations of bone behaviour. A technique to computationally generate realistic trabecular bone microstructures is developed. This provides the possibility of examining the effect of different microstructures on the macrolevel mechanical behaviour of bone. They would also permit direct incorporation of bone microstructure in macroscale finite element analyses without the prohibitive computational and experimental costs of donor-image based mesh generation. Micro- finite-element analyses are used for the first time to evaluate the macrolevel orthotropic elastic constants of cortical bone resulting from variations of microstructural morphology. It is concluded that the ratio of canal volume to tissue volume is the most powerful predictor of cortical bone elastic constants and that considerable periosteal-endosteal variations in these constants can develop with bone loss. The role of microstructure in cortical bone toughness is investigated using nano- finite-element analyses of murine cortical bone samples to simulate the initiation and propagation of microcracks. Results confirm the experimentally observed ability of canal and lacuna pores to act as stress raisers, thereby guiding the growth of microcracks. A novel and numerically efficient strain-based plasticity algorithm is presented which permits easy incorporation of strength anisotropy in finite element analyses of bone. The previously evaluated elastic properties of cortical bone are combined with the developed plasticity algorithm to conduct a detailed macro-finite-element investigation of external fixation of tibial midshaft fractures. Old patients are found to be at considerably higher risk of implant loosening under both unilateral and Ilizarov fixation, compared to younger patients.

No description available.

The Finite Element Method (FEM) is a technique for finding the approximate solution of differential equations. It is commonly used in structural analysis to evaluate the deformation and internal stresses of a structure that is subject to outer loads. This thesis investigates the Finite Element Analysis (FEA) workflow that is used at Andritz Hydro AB, with the objective to find solutions that make the workflow more time effective. The current workflow utilises Siemens NX and Salomé for pre- and post-processing, and Code Aster as the FEM solver. Two different approaches that improve the workflow are presented. The first suggest that the entire FEA workflow is migrated to NX using the built-in FEM package of NX called Advanced Simulation. The second approach utilises the Salomé API (Application Programming Interface) to create a customised toolbox (a script containing several functions) that automate several repetitive and cumbersome steps of the workflow, therefore effectively reducing the time that is required by the analyst to perform FEA. Due to the positive results and ease-of-use, the Salomé toolbox is preferred over the license cost and steep learning curve that is related to NX and Advanced Simulation.

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 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.

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.