P-1308P-1308

P 1308 – Improved toughness requirements for high strength steels in pressure vessel applications

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P 1308 – Improved toughness requirements for high strength steels in pressure vessel applications

The aim of this work was to define new toughness requirements for HSLA steels, based on damage mechanical methods, in order to create the possibility to increasingly apply higher strength steels and to exploit their potential.
In order to achieve this goal, it was first necessary to refine and extend existing models. In this work, particular attention was paid to the aspects of temperaturedependent material parameters and feasibility with respect to nominal parameters.
The model adaptations for the simulation of the nominal parameters refer primarily to the flow curve. An already existing method was chosen to derive flow curves based on yield strength, tensile strength and uniform elongation. In this way, important and easily determined parameters, which are largely given by standards, are used as a basis. The procedure is thus as simple and efficient as possible.
The second important aspect for the damage-mechanical model is the temperature dependence of the model parameters. First, an efficient and precise concept was developed based on the choice of nominal flow curves, which ensures an adjustment of the flow function with temperature. The results obtained are significantly better than those obtained with the model previously available at IEHK. Furthermore, this continuity allowed to keep the ductile material parameters constant with changing temperature.
In addition, an innovative stress state-based method was developed in this work to accurately represent the temperature transition in the Charpy impact test, which is essential for toughness and based on the change of fracture mechanism. The combination of these steps allows the simulation of nominal toughness requirements in Charpy impact tests and their transferability to components.
Based on this methodology, toughness requirements were derived from the material side and applied to different model pressure vessels. Through the results, maximal loads for steels of strength class 690 MPa could be derived from critical pressure vessel details. The project objective of defining a simplified toughness requirement derived from damage mechanics material simulations was thus achieved

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Published in:
April 2022

Authors:
Prof. Dr.-Ing. S. Münstermann, J. Langenberg, M.Sc., Prof. Dr.-Ing. M. Feldmann, R. Kühne, M. Sc., SFI/IWE