Development of Micro-mechanical Models of Fatigue Damage

Nonlinear Guided Wave Tomography for Detection and Evaluation of Early-Life Material Degradation in Plates

“…In this work, RAPID based on ray tomography was used for reconstruction. Two aluminum plate models with and without degradation were established, whose parameters were set the same except for the degraded regions, following the findings that degradation can be accounted for by using higher TOECs in the Murnaghan model [ 26 , 27 ]. The aluminum plate model has a size of , which was spatially discretized into a structured mesh using 1 mm cubic C3D8R elements.…”

“…As shown in Figure 4 , three circular degradations with diameters , and depths are defined on some nodes on the aluminum plate, whose coordinates of the center are (−200, −200), (100, −100) and (0, 200), respectively. The TOECs ( , , and ) of the degraded regions are modelled as , , and of that of the intact material to indicate different degrees of degradation [ 26 , 27 ].…”

“…Therefore, Murnaghan’s model acts as a weakly nonlinear model, as opposed to the linear (Hookean) model [ 24 , 25 ], to define the various degrees of degradation. On the other hand, it was demonstrated that the third-order elastic constants (TOECs) in Murnaghan’s model are sensitive to fatigue damage [ 26 ]. In the early stage of degradation, the TOECs of the material will increase with the degree of fatigue [ 27 ].…”