Structural material damage monitoring under variable loading at surface deformation defect density


The process of loading of the mechanical object made of the elastoplastic material is accompanied by the formation of the stochastic structure of deformation defects on its surface due to the natural evolution of micro-plastic strains of polycrystalline. Consequently, the uniform deformation surface pattern formation is observed, which during the coherent beam radiation is responsible for the speckle field structure within the rough material surface zone. The amplitude characteristics of micro-strains of the object surface can be controlled via the statistical energy parameters of the reflected bundle of the coherent beam by the micro-elements of the deformed material zone. The deformation pattern elements on the material surface of the irradiated object serve as the scatter zones. A certain deformation pattern is detected on the object surface due to the kinetic features of deformation damage accumulation in the elastoplastic material. This paper proposes the approach (using DIC method) to the determination of the kinetics of micro-strains on the material surface that allows one to monitor its damage at its non-localized fatigue stage. The obtained damage characteristics allow one to monitor the fatigue failure under variable loading, which can be employed in the determination of residual life and increase their operational reliability.