This paper presents an experimental and numerical study of the mechanical behaviour of SAE 1045 steel sheet specimens during the conventional tensile test. Due to the complex stress state that develops at the neck for high levels of axial deformation, an experimental-numerical methodology is proposed in order to derive the elastic and hardening parameters which characterize the material response. Such methodology is essentially an extension to sheet samples of the well established procedure used for cylindrical ones. The simulation of the deformation process during the whole test is performed with a finite element large strain elastoplasticity-based formulation. Finally, the experimental validation of the obtained numerical results allows to assess the performance of the proposed methodology for the 3D analysis of sheet specimens and, in addition, to discuss the range of applicability of plane stress conditions.

The mechanical properties of aortic wall, both healthy and pathological, are needed in order to develop and improve diagnostic and interventional criteria, and for the development of mechanical models to assess arterial integrity. This study focuses on the mechanical behaviour and rupture conditions of the human ascending aorta and its relationship with age and pathologies. Fresh ascending aortic specimens harvested from 23 healthy donors, 12 patients with bicuspid aortic valve (BAV) and 14 with aneurysm were tensile-tested in vitro under physiological conditions. Tensile strength, stretch at failure and elbow stress were measured. The obtained results showed that age causes a major reduction in the mechanical parameters of healthy ascending aortic tissue, and that no significant differences are found between the mechanical strength of aneurysmal or BAV aortic specimens and the corresponding age-matched control group. The physiological level of the stress in the circumferential direction was also computed to assess the physiological operation range of healthy and diseased ascending aortas. The mean physiological wall stress acting on pathologic aortas was found to be far from rupture, with factors of safety (defined as the ratio of tensile strength to the mean wall stress) larger than six. In contrast, the physiological operation of pathologic vessels lays in the stiff part of the response curve, losing part of its function of damping the pressure waves from the heart.

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This paper is focused on the numerical and experimental analyses of the collapse of a liquid column. The measurements of the interface position in a set of experiments carried out with shampoo and water for two different initial column aspect ratios are presented together with the corresponding numerical predictions. The experimental procedure was found to provide acceptable recurrence in the observation of the interface evolution. Basic models describing some of the relevant physical aspects, e.g. wall friction and turbulence, are included in the simulations. Numerical experiments are conducted to evaluate the influence of the parameters involved in the modeling by comparing the results with the data from the measurements. The numerical predictions reasonably describe the physical trends.

This paper presents an experimental and numerical characterization of ductile damage evolution in steels subjected to large plastic deformations. To this end, a set of tensile tests combining load-unload cycles is firstly carried out in order to evaluate the deterioration exhibited by the Young's modulus for increasing levels of plastic deformation. This task allows, in turn, to derive the characteristic parameters involved in a well-established evolution equation for the isotropic damage variable. All these material parameters are the basic data to be considered in the simulations that are performed afterwards: the analysis of the tensile test is mainly aimed at assessing the proposed characterization while the modelling of the flattening process of a cylinder is considered to discuss the possibilities and limitations of the constitutive model.

SUMMARYWe describe, for simulation of ows with moving interfaces, a computational method based on the edgetracked interface locator technique (ETILT). The method described has been designed by bearing in mind the ease in managing a node-based interface representation and the interface sharpness and volume conservation features of the Moving Lagrangian Interface Technique. We evaluate the performance of the method with a number of test problems: ÿlling of a step cavity, gravity-driven ow of an aluminium alloy in an obstructed channel, collapse of a liquid column, and the bore problem.

This work presents experiments and modelling aimed at characterising the passive mechanical behaviour of the human thoracic descending aorta. To this end, uniaxial tension and pressurisation tests on healthy samples corresponding to newborn, young and adult arteries are performed. Then, the tensile measurements are used to calibrate the material parameters of the Holzapfel constitutive model. This model is found to adequately adjust the material behaviour in a wide deformation range; in particular, it captures the progressive stiffness increase and the anisotropy due to the stretching of the collagen fibres. Finally, the assessment of these material parameters in the modelling of the pressurisation test is addressed. The implication of this study is the possibility to predict the mechanical response of the human thoracic descending aorta under generalised loading states like those that can occur in physiological conditions and/or in medical device applications.

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