Mechanical Simulation Model for Acoustic Damage Monitoring in Polycrystalline Materials

The paper proposes a mechanical simulation model based on continuum damage mechanics and physical mesomechanics to describe the accumulation of dispersed damages in polycrystalline materials, considering that the main damaging factors are dispersed microcracks and internal stresses produced primarily by linear structural defects. From the proposed model follows a statistical limit state criterion consistent with failure conditions for brittle and ductile structural materials. The limit state criterion is applied to several typical cases of failure and elastic-to-elastoplastic strain transition in polycrystalline structural materials. Based on the model, an acoustic approach to damage assessments of structural materials is also proposed. With the approach, several acoustic effects are identified from the propagation of elastic pulses in a damaged material. Such effects can be useful for instrumental damage assessment of materials (specimens, structural elements) at any time of loading or operation. The acoustic approach can provide a basis for a method of measuring the damage parameters included in the model. The experimental data available to us suggest that the proposed approach to damage assessment is correct for structural materials and is promising for further experimental research to develop instrumental express methods of monitoring dispersed damages in metal structures exposed to thermomechanical loads.