The article assesses the structural strength of sample materials destroyed on standard equipment for determining the mechanical properties of materials. The distribution of mechanical stresses of laboratory disk samples with stress concentrators in the form of grooves on the support surfaces was analyzed. It was revealed that the disc truncation along the two symmetrical chords allows for varying the type of stress state in the sample and intensity of stresses in the working zone. The problems of the linear theory of elasticity were solved for samples with different degrees of disc truncation and with different geometric parameters of the groove profile. The analysis of disk deformation showed that these laboratory samples can be used in simulating the type and level of stress-strain state of various parts of machines and mechanisms. This factor significantly expands the possibilities for assessing the structural strength of materials during laboratory studies of the materials. It was revealed that the type of stress-strain state (SSS) plays a role in localizing the sources of destruction of highly loaded structural elements made from structural carbon steel St45. The results can be used both for the experimental assessment of the structural strength of materials and for constructing limit state equations corresponding to a SSS level and type.