Novel damage calibration test based on cross-wedge rolling
Z. Pater, J. Tomczak, Tomasz Bulzak, Patrycja Walczuk-Gągała
Abstract
This article presents a new calibration test for damage functions that uses the cross-wedge rolling method (CWR). In this test, the forming conditions were altered by applying wedges with decreasing forming angle on conical-cylindrical samples. The conditions worsened as the distance from the centre of the sample increased. At a certain point, the conditions became sufficiently unfavourable that the material cracked. To determine the critical values of material damage, the location of cracking in the sample was determined. Then, based on a numerical simulation, the value of the damage function in this area was determined and assumed to be the critical damage value. Using the presented method and normalised Cockcroft–Latham criterion, critical damage values for C45 grade steel in the temperature range 900–1100 °C were determined. It was observed that the critical material damage was highly dependent on the forming temperature. The determined critical damage value was used to model material fracture in a CWR process that was performed using parameters ensuring that this internal defect would occur. A comparison of the numerical and experimental crack lengths showed that they were in perfect agreement, which confirms that the developed calibration test can be used for modelling damage in CWR processes.