Assessment of the strength of a material using deformable discs with a variable type of stress state

The paper considers a technique for assessing the strength of a material in a complex stress-strain state. For this purpose, the strength of disk-shaped material samples with stress concentrators is being investigated. Stress-strain state modeling was implemented in this work using the finite element method, taking into account the nonlinear nature of the processes under consideration. The reliability of the obtained numerical simulation results was evaluated on the basis of a sequence of FE approximations. The experimental destruction of the proposed samples was carried out on a typical Instron 5989 machine and confirmed the possibility of creating in the tested samples a given level of the ratio of the main stresses arising under biaxial tension conditions. Using the example of steel 45, it is shown that the use of the samples under consideration makes it possible both to evaluate the structural strength of materials and to carry out a local approximation of the corresponding marginal surface. A modified version of the Pisarenko – Lebedev criterion was used as the theoretical basis for its local approximation. It is shown that the proposed disk samples have a relatively simple shape and have a high variability in the type of stress state. This circumstance allows us to transfer the assessment of the structural strength of materials to the stage of its laboratory studies.