SUMMARYAlgorithms based upon the notion of return mapping have been developed for the Hill yield function of anisotropic plasticity. The relative accuracy of two algorithms is assessed by means of iso-error maps. The choice of the algorithm turns out to be much more critical for the orthotropic Hill criterion than for the underlying isotropic von Mises plasticity model. A tangent operator that is consistent with the developed integration algorithm is formulated and its efficiency is assessed compared with the classical continuum tangent operator. The model has been applied to three shell/platt structures.

A simulation framework for drug-eluting stents (DES) is presented that simulates the two distinct operational phases of a DES: stent deployment is simulated first, a mechanical porohyperelastic/elasto-plastic/contact analysis. This analysis calculates the interstitial fluid velocity as the result of interstitial fluid pressure gradients and mechanical deformations of the vessel wall. The deformed geometry, interstitial fluid velocity field and porosity field are extracted and used as input for the drug release simulation: a reaction-advection-diffusion (RAD) transport analysis calculating the spatial and temporal drug distribution. The advantage of this approach is that the deformed geometry and interstitial fluid velocity field are not assumed a priori, but are actually calculated using a stent deployment simulation. The framework is demonstrated simulating a DES in an idealised, 3D vessel. Varying mechanical and transport properties based on literature data are assigned to each of the three layers in the wall. The results of the drug release simulation for a period of one week show that the drug distributes longitudinally but will remain in the proximity of the stented area.

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This is a case study where the goal is to predict the vibration environment due to a footfall excitation in the vicinity of a replacement Magnetic Resonance Imaging (MRI) unit on a hospital floor. A new MRI unit with a weight of 19,000 lbs replaces an existing, much heavier unit with a weight of 82,000 lbs. Dynamic characteristics of the floor will change when the new unit is installed, affecting the vibration environment of the unit that is generated by nearby footfalls.In this study we use physical heel drop measurements of the existing conditions to calibrate a computer model that we then use to predict the vibrations and compare the calculated vibrations with the criteria for the new unit.The results show that the vibration levels predicted for the new MRI unit do not exceed its vibration criterion. The paper will present detailed analytical model and analysis procedure, together with conclusions.