Experimental and numerical investigations of the warm-prestressing (WPS) effect considering different load paths

The effect of warm prestressing has been investigated representative for the core weld metal of the RPV state. Model experiments on CT specimens show a significant rise of effective fracture toughness K sub eff after warm prestressing and the conservative WPS hypothesis, 'no failure, if delta K sub 1 / delta t < = 0', is verified. Partial unloading and reheating show no influence on the effective fracture toughness K sub eff . The magnitude of the WPS effect as a function of warm prestress level and temperature, path of unloading and cooling can be predicted using a modified Beremin model with temperature dependent parameters. It is shown that the Weibull stress is an appropriate crack tip loading parameter for decreasing load paths. Weld metal was a nickel chromium molybdenum steel.