Entwicklung von Verfahren zur Ermittlung von Risswiderstandskurven verschiedener Probengeometrien aus der Kerbschlagarbeit

The assessment of the reliability of components requires the knowledge of their crack resistance curves, which are often not available due to lack of specimen material. More likely is the availability of typical material parameters such as the yield strength, tensile strength, uniform elongation, fracture strain as well as upper shelf impact energy and the lateral elongation of notched-bar impact test specimens. The goal of the current work consists in developing a method with which one can construct fracture resistance curves using such information. To this end, three different kinds of steels were investigated, each quite different form the others in terms of its yield strength and upper shelf impact energy. Crack resistance curves for specimens made form each of these steels were determined experimentally for temperatures between 23 C and 300 C. In addition, the respective yield curves were obtained. To determine the influence of the notch geometry on fracture behaviour, tests on radially notched tensile specimens with different notch radii in the above temperature range were carried out. Using the low-blow method, J-resistance curves for Charpy specimens were determined in instrumented notched-bar impact tests performed between 23 C and 300 C. The material model of Gurson describes ductile crack growth due to the nucleation, growth and coalescence of damage pores in the material. Although dependent on the material and temperature, the material parameters of the Gurson model are independent of the specimen geometry and rate of loading. This latter fact allows one to use the values of these parameters determined on statically-loaded fracture mechanics specimens to model specimens with other geometries and subjected to other loading conditions, in particular to model impact loaded Charpy-V specimens. The material parameters of the Gurson ductile damage model were identified for each of the three above-mentioned steels with the help of quasi-static fracture tests on different specimen geometries at different temperatures. On the basis, it was confirmed that these parameters are in fact independent of the specimen geometry. In addition, good agreement was obtained between experimentally-determined and numerically-simulated curved crack fronts in non-side-grooved specimens. Taking advantage of the fact that the material parameters are independent of the rate of loading, notched-bar impact tests were also successfully modelled using these. (orig.)SIGLEAvailable from TIB Hannover: RA 2565(228) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman