- Edinburgh, Edinburgh, City of, United Kingdom
Francesc Levrero
University of Edinburgh, School of Engineering, Graduate Student
Explicit strategies for the solution of finite element problems, such as crash simulation, scale well on computing platforms with thousands of cores. In contrast, it is a widely held view that implicit analysis is not suited to parallel... more
Explicit strategies for the solution of finite element problems, such as crash simulation, scale well on computing platforms with thousands of cores. In contrast, it is a widely held view that implicit analysis is not suited to parallel computing. The purpose of this paper is to challenge that belief. The open source parallel finite element software, ParaFEM, uses an “element by element” approach with iterative solvers to solve problems in an implicit way; such as static equilibrium, material nonlinearity, fluid flow, and free and forced vibrations. This iterative strategy leads to a program structure similar to explicit algorithms and the consequence is excellent scalability of implicit analysis on parallel platforms. The software is modularised in such a way that the parallel code is hidden away in a library of subroutines, enabling engineers and researchers who have no training in parallel programming to adapt the software for their own needs. In this paper, we report on recent p...
Explicit strategies for the solution of finite element problems, such as crash simulation, scale well on computing platforms with thousands of cores. In contrast, it is a widely held view that implicit analysis is not suited to parallel... more
Explicit strategies for the solution of finite element problems, such as crash simulation, scale well on computing platforms with thousands of cores. In contrast, it is a widely held view that implicit analysis is not suited to parallel computing. The purpose of this paper is to challenge that belief. The open source parallel finite element software, ParaFEM, uses an “element by element” approach with iterative solvers to solve problems in an implicit way; such as static equilibrium, material nonlinearity, fluid flow, and free and forced vibrations. This iterative strategy leads to a program structure similar to explicit algorithms and the consequence is excellent scalability of implicit analysis on parallel platforms. The software is modularised in such a way that the parallel code is hidden away in a library of subroutines, enabling engineers and researchers who have no training in parallel programming to adapt the software for their own needs. In this paper, we report on recent p...
Medialization of the cup with a respective increase in femoral offset has been proposed in THA to increase abductor moment arms. Insofar as there are potential disadvantages to cup medialization, it is important to ascertain whether the... more
Medialization of the cup with a respective increase in femoral offset has been proposed in THA to increase abductor moment arms. Insofar as there are potential disadvantages to cup medialization, it is important to ascertain whether the purported biomechanical benefits of cup medialization are large enough to warrant the downsides; to date, studies regarding this question have disagreed. The purpose of this study was to quantify the effect of cup medialization with a compensatory increase in femoral offset compared with anatomic reconstruction for patients undergoing THA. We tested the hypothesis that there is a (linear) correlation between preoperative anatomic parameters and muscle moment arm increase caused by cup medialization. Fifteen patients undergoing THA were selected, covering a typical range of preoperative femoral offsets. For each patient, a finite element model was built based on a preoperative CT scan. The model included the pelvis, femur, gluteus minimus, medius, and...
Research Interests:
Computational homogenisation approaches using high resolution images and finite element (FE) modelling have been extensively employed to evaluate the anisotropic elastic properties of trabecular bone. The aim of this study was to extend... more
Computational homogenisation approaches using high resolution images and finite element (FE) modelling have been extensively employed to evaluate the anisotropic elastic properties of trabecular bone. The aim of this study was to extend its application to characterise the macroscopic yield behaviour of trabecular bone. Twenty trabecular bone samples were scanned using a micro-computed tomography device, converted to voxelised FE meshes and subjected to 160 load cases each (to define a homogenised multiaxial yield surface which represents several possible strain combinations). Simulations were carried out using a parallel code developed in-house. The nonlinear algorithms included both geometrical and material nonlinearities. The study found that for tension-tension and compression compression regimes in normal strain space, the yield strains have an isotropic behaviour. However, in the tension-compression quadrants, pure shear and combined normal-shear planes, the macroscopic strain norms at yield have a relatively large variation. Also, our treatment of clockwise and counter-clockwise shears as separate loading cases showed that the differences in these two directions cannot be ignored. A quadric yield surface, used to evaluate the goodness of fit, showed that an isotropic criterion adequately represents yield in strain space though errors with orthotropic and anisotropic criteria are slightly smaller. Consequently, although the isotropic yield surface presents itself as the most suitable assumption, it may not work well for all load cases. This work provides a comprehensive assessment of material symmetries of trabecular bone at the macroscale and describes in detail its macroscopic yield and its underlying microscopic mechanics.