Study of Weibull parameters at different loading rates for 20MnMoNi55 steel using Beremin model

This work considers the influence of loading rate on the Weibull stress parameters in the Beremin model for 20MnMoNi55 RPV steel using finite element modelling of compact tension specimen. For failure analysis of cleavage fracture at component level, the Beremin model is very useful. To implement the Beremin model, the model parameters needed to be calibrated for this particular material with experimental observation. In the first portion of this study, some fracture experiments are conducted at -100°C for four different loading rates ranging from quasi-static to dynamic rates (0.625–255.8 MPa√m/s) to obtain master curves and reference temperatures. Then calibration of the Weibull stress parameters is done in a specific loading rate by linear regression analysis for different a/W ratios. For the other loading rates, Monte Carlo simulation technique along with respective master curve is used to calibrate the model parameters. Then variation of the Weibull stress parameters with loading rate is studied. This study shows that loading rate has a significant effect on the Weibull stress parameters. Reference temperatures are also determined for different a/W ratios and loading rate by calibrated Weibull stress parameters from experiments as well as Monte-Carlo simulation. Obtained reference temperatures are compared with experimental values for respective loading rates. With the increasing loading rate reference temperature, obtained from the Beremin model is found to be increased and it matches well with the experimental reference temperature values.