Improved Exploitation of High-strength Steels in Pressure Vessel Design by Simulations Based on Damage Mechanics

摘要

Pressure vessels are subjected to regulation by European standards, which define design procedures and nominal material properties that are guaranteed by the steel producers. Over-conservative safety factors for materials with high yield-to-tensile ratios hinder the application of modern high-strength steels despite their excellent toughness and possible economic and ecologic benefits. Damage mechanics enable a more adequate failure description for these steels since they can consider ductile crack initiation as limit state. Such concepts should refer to nominal material characteristics to enhance their applicability in design procedures. A method is presented to correlate the nominal Charpy impact toughness to simulations with the Gurson-Tvergaard-Needleman-model (GTN). The resulting GTN parameters are used in cell model simulations to derive strain-based empirical failure criteria as nominal ductility measure for simulations on component level. A sensitivity study on the GTN parameter choice shows that the initial pore volume is the most relevant parameter, but other non-unique parameters also influence the failure prediction. The impact of the individual parameters is discussed. By the definition of a reliable calibration scheme for the GTN parameters this approach enables an identification of adequate lower bound failure criteria for high-strength steels in pressure vessels as a preliminary pressure vessel simulation demonstrates.