Metals Machining—Recent Advances in Experimental and Modeling of the Cutting Process

Metal machining involves severe loading in the cutting zone. [...]

Numerical predictions of the behaviour of plain concrete targets subjected to impact

One widely used model implemented in the hydrocode ANSYS Autodyn is the Riedel–Hiermaier–Thoma material model, which is used for the prediction of concrete behaviour under severe loading, such as blast and impact. In the Riedel–Hiermaier–Thoma model, parameters are adjusted to be a function of the compressive strength of specific concrete. This advantage enables occasional users (and those who cannot conduct experiments to determine all the required concrete parameters) to input only this parameter, while the rest is automatically calculated by default settings. This study is an attempt to calibrate (not modify) this model, with the least number of possible changes, to better predict the performance of concrete targets, particularly spalling and scabbing phenomena, impacted by hard projectiles. It is shown that the present calibration of the Riedel–Hiermaier–Thoma material model performed well when compared to the default settings currently available in the model.

Application of XFEM to Model Crack Initiation and Propagation During a PTS Event

The integrity of a reactor pressure vessel (RPV) has to be ensured throughout its entire life in accordance with the applicable regulations. Typically an assessment of the RPV against brittle failure needs to be conducted by taking into account all possible loading cases. One of the most severe loading cases, which can potentially occur during the operating time, is the loss-of-coolant accident (LOCA), where cold water is injected into the RPV at operating conditions. High pressure in combination with a thermal shock of the ferritic pressure vessel wall caused by the injection of cold water leads to severe loading conditions at the beltline area known as Pressurized Thermal Shock (PTS). Usually the assessment against brittle failure is based on a deterministic fracture mechanics analysis, in which common parameters like the J-integral or stress intensity factor are employed to calculate the load path during the PTS event for an assumed (postulated) flaw. Subsequently the results of the fracture mechanics analysis are compared with material properties obtained from the irradiation surveillance program of the RPV to demonstrate the exclusion of brittle fracture initiation. In this paper an alternative novel method for the calculation of the crack initiation and possible crack propagation by means of the eXtended Finite Element Method (XFEM) will be introduced and compared with results of the standard PTS analysis.