A finite element model is developed for the process of squeeze casting of metal matrix composites in cylindrical molds. The fluid flow and the heat transfer are fundamental phenomena in squeeze casting. To describe heat transfer in the solidification of molten aluminum, the energy equation written in terms of temperature and enthalpy are applied in an axisymmetric model which is similar to the experimental system. A 1-D flow model simulates the transient metal flow. A direct iteration technique was used to solve the resulting nonlinear algebraic equations, using a computer program to calculate the enthalpy, temperature and fluid velocity. The cooling curves and temperature distribution during infiltration and solidification were calculated for pure aluminum. Experimentally, the temperature was measured and recorded using thermocouple wire. The measured time–temperature data were compared with the calculated cooling curves. The resulting agreement shows that the finite element model can accurately estimate the solidification time and predict the cooling process.
This study introduces implementation of a nodal release technique into a FEM/continuum model to enable simulation of fully plastic crack growth. The nodal release technique is implemented in the user-defined element form on the symmetry line of a deeply single-edge cracked specimen so that the force at the crack-tip node on the symmetry line is made zero after several steps upon the satisfaction of a chosen fracture criterion, and an incremental crack extension is achieved. The fracture criterion adopts the crack-tip opening angle (CTOA) which is determined from the specimen's loading geometry [1]. For evaluation of the present model, the crack growth simulation results from the present FEM model were compared to those from the line-spring model of Lee and Parks [2].
The objective of this work is to study the crack-tip field of plane strain fully plastic crack growth of a single-edge cracked specimen subject to pure extension. The nodal release technique [1] was implemented into an FEM model so that the nodes arranged in the crack path are released. The fracture criterion for the crack growth in the model adopts the loading geometry-based crack-tip opening angle-(CTOA) proposed in the work of Ref.[2]. The crack-tip field from the CTOA-based crack growth was investigated and characterized with a slip line field. It was observed that the backface configuration of the specimen, which evolves with the crack growth, is engaged in the formation of the shear band and, as a result, significantly elevates the triaxiality at the crack-tip during the crack growth.
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