Bayesian method approach for fatigue life distribution estimation of rubber components

The constantly increasing market requirements of high-quality vehicles compel automotive manufacturers to perform lifetime testing to verify the reliability levels of new products. A common problem is that only a small number of samples of a system\u27s component can be tested. In automotive applications, mechanical components subjected to cyclic loading have to be designed against fatigue. In this paper, the Bayesian estimation of lognormal distribution parameters (usually used to define the fatigue lifetime of rubber components) is studied to improve the accuracy of estimation while incorporating the available knowledge on the product. In particular, the finite element results and experts\u27 opinions are considered prior knowledge. For lifetime prediction by Finite Element Method (FEM), a model based on the Brown-Miller law was developed for the rubberlike boot seal material

Finite element 3D modeling of mechanical behavior of mineralized collagen microfibrils

The aim of this work is to develop a 3D finite elements model to study the nanomechanical behaviour of mineralized collagen microfibrils, which consists of three phases, (i) collagen phase formed by five tropocollagen (TC) molecules linked together with cross links, (ii) a mineral phase (Hydroxyapatite) and (iii) impure mineral phase, and to investigate the important role of individual properties of every constituent. The mechanical and the geometrical properties (TC molecule diameter) of both tropocollagen and mineral were taken into consideration as well as cross-links, which was represented by spring elements with adjusted properties based on experimental data. In the present paper an equivalent homogenised model was developed to assess the whole microfibril mechanical properties (Young's modulus and Poisson's ratio) under varying mechanical properties of each phase. In this study both equivalent Young's modulus and Poisson's ratio which were expressed as functions of Young's modulus of each phase were obtained under tensile load with symmetric and periodic boundary conditions.Comment: Journal of Applied Biomaterials and Biomechanics 9, 3 (2011) xx

Application of spectral/hp element methods to high-order simulation of industrial automotive geometries

Flow predictions around cars is a challenge due to massively separated flow and complex flow structures generated. These flow features are usually poorly predicted by present industrial computational fluid dynamics (CFD) codes based on a low fidelity Reynolds averaged Navier Stokes (RANS) approach simulating the mean effects of turbulence. On the other hand, high fidelity approaches resolve turbulent scales but require many more degrees of freedom than classical techniques for an accurate solution. Previous applications have shown that the coupling of the spectral/hp element method and implicit large eddy simulation (iLES) turbulence treatment could be a potential candidate to perform high-fidelity simulations. This work aims at transferring the spectral/hp element technology to the automotive industry in which high Reynolds numbers and complex geometries are typical. Recent developments in stabilisation techniques such as the discontinuous Galerkin kernel spectral vanishing viscosity (SVV) and high-order meshing capabilities open the possibility of the application of the spectral/hp element method to complex cases. The technology is first implemented to an industrial case proposed by McLaren Automotive Limited (MLA) at a realistic Reynolds number of 2,3 million based on the front wheel diameter and is compared to a RANS numerical development tool. Differences in terms of vortical structures arrangement, principally due to the front wheel wake are highlighted. In parallel, a workflow is developed to systematically address similar complex cases. The interaction between h-refinement, related to the size of the elements of the mesh, and p-refinement, corresponding to the polynomial expansion order, is investigated on the SAE notchback body. Two different hp-refinement strategies with similar numbers of degrees of freedom are employed, the first one with a fine mesh and a third-order accurate polynomial expansion and the second one with a coarse mesh and a fifth-order accurate polynomial expansion. Results show that a minimum level of h-refinement is necessary to capture flow features and that p-refinement can subsequently be used to improve their resolution. The final part focuses on wheel rotation modelling. Scale-resolving techniques are intrinsically unsteady and therefore require sophisticated techniques to correctly model rotating wheels. A procedure, built upon an immersed boundary method (IBM) called the smoothed profile method (SPM), is developed to model complex three-dimensional rotating geometries, in particular rim spokes. It is finally applied to an isolated rotating wheel case and results are compared to the moving wall (MW) and the moving reference frame (MRF) modelling techniques. It is concluded that the SPM is in better qualitative agreement with experimental results present in the literature than the two other modelling strategies.Open Acces

Numerical investigation of key stamping process parameters influencing tool life and wear

The influence of various combinations of punch and die materials, such as different carbide grades, and also the cutting radius on tool wear is the aim of this investigation. The numerical analysis results are supported by the relevant experimental evidence to validate the main model assumptions such as assumed material flow stress curve and the damage criteria. Taguchi method is utilised to effectively model and analyse relationship between process parameters. Roll-over and burr formation for a given punch-die clearance and cutting radius have been discussed and analysed in terms of tool wear reduction for different materials

Editorial: Bone integrity in patients with osteoporosis: Evaluation of fracture risk and influence of pharmacological treatments and mechanical aspects

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