A discussion of the scaling effect in numerical simulation of the extrusion process

The main objective of the work of this paper is to study the possibility of using a small scale geometrical model in the numerical simulation of aluminium extrusion. The advantages and shortcomings of the application of the geometrically similar model in FEM simulation are discussed. Thermal – mechanical and metallurgical combined simulations are performed within two tests using geometrically similar models and assessment is made in terms of mechanical and material properties. It was found that small scale simulation could not reproduce most of the important forming parameters of the original process, although it could help to bring about significant savings in computation time

Investigation of metal flow in bridge die extrusion of Alloy 6063 and subsequent effect on surface quality and weld seam integrity

This paper describes a detailed study of tube extrusion by simulation using finite element method (FEM). The finite element model used one-sixth of symmetry. The extrusion load, emperature evolution and metal flow were predicted. Innovative methods, combining both grid and surface tools, were used to define in detail the flow of material. These showed clearly the inner and outer surface formation mechanisms of the tube extrusion. The seam weld, an important quality indicator, was also evaluated by selecting an appropriate criterion

Numerical modeling and analysis of Ti6Al4V alloy chip for biomedical applications

The influence of cutting forces during the machining of titanium alloys has attained prime attention in selecting the optimal cutting conditions to improve the surface integrity of medical implants and biomedical devices. So far, it has not been easy to explain the chip morphology of Ti6Al4V and the thermo-mechanical interactions involved during the cutting process. This paper investigates the chip configuration of the Ti6Al4V alloy under dry milling conditions at a macro and micro scale by employing the Johnson-Cook material damage model. 2D modeling, numerical milling simulations, and post-processing were conducted using the Abaqus/Explicit commercial software. The uncut chip geometry was modeled with variable thicknesses to accomplish the macro to micro-scale cutting by adapting a trochoidal path. Numerical results, predicted for the cutting reaction forces and shearing zone temperatures, were found in close approximation to experimental ones with minor deviations. Further analyses evaluated the influence of cutting speeds and contact friction coefficients over the chip flow stress, equivalent plastic strain, and chip morphology. The methodology developed can be implemented in resolving the industrial problems in the biomedical sector for predicting the chip morphology of the Ti6Al4V alloy, fracture mechanisms of hard-to-cut materials, and the effects of different cutting parameters on workpiece integrity

Motor expertise for typing impacts lexical decision performance

The massive shift in writing habits calls for a better understanding of the possible consequences of typing practice on language processing, including reading. To assess a possible impact of typing knowledge on word recognition, we built a set of words and pseudowords differing by their ratio of bimanual transitions between letters, an index of typing difficulty for experts. An effect of typing difficulty was observed in expert participants who were actually typing the items and not in a control group of hunt-and-peck typists. We then tested whether word recognition, measured with the task of lexical decision, was impacted by the typing difficulty of words. We found that lexical decision latencies varied as a function of typing difficulty, but differently for experts and non-experts. The effect was mostly driven by pseudowords. This suggests that motor representations built during the practice of typing have a collateral effect on visual recognition processes. The implications for education are discussed