METHODOLOGY FOR DETERMINING THE LEVEL OF PERFORMANCE OF A WORKING PART WITH SIGNS OF MECHANICAL DAMAGE

The article discusses the urgent problem of the operability of a working part with signs of mechanical damage in the form of cracks, which negatively affects the performance of the object. Premature, sometimes sudden destruction occurs even when subjected to minor loads. The purpose of the article is to analytically determine the critical state of a structural element in terms of its performance through stress intensity factors (SIF), which are a numerical characteristic of the material's crack resistance. Cracks can be technological: they occur during casting, forging, welding, as well as acquired; during installation of the object or operation (from overload), The occurrence of cracks also depends on the type of load: static, alternating and dynamic; on the type of deformation: tension-compression, shear, torsion, bending, as well as on the physical and mechanical characteristics of the material and the geometry of the object. Practice shows that the presence of a crack does not mean the loss of the bearing capacity of the structure: damage up to a critical crack size can be safe if it is possible to detect and track the development of the defect, which will justify the further operation of the valuable object. Given the complexity of the problem under consideration, we solve it using the energy balance method. Its essence is as follows. Elastic bodies accumulate mechanical energy potential during deformation. It cannot disappear without a trace, and in the presence of a crack, it is accumulated by the surfaces of its banks, or rather in the tension deformation of these banks, which leads to the development of a crack. The critical state of crack resistance is determined by the ratio between the stress intensity coefficients (SIC), which reflect the size of the crack and the acting stresses. In this case, the structure will be inoperable, or such that the destruction process can be prolonged in time.