Effects of Temperature on Fatigue Crack Propagation in Pseudoelastic NiTi Shape Memory Alloys

Fatigue Crack Growth in Austenitic and Martensitic NiTi: Modeling and Experiments

“…6). In the following, a summary description of the method is provided for the sake of completeness but full details about the nonlinear regression are given in [34].…”

“…This leads to a new set of nonlinearly coupled equations and, as reported in [34], the estimation of the new unknowns requires a nonlinear fitting process by an iterative procedure based on Newton-Raphson method. To this aim, Eq.…”

“…Localized near-crack-tip martensitic transformations were also observed by infrared thermography (IR) [28,29] and instrumented nanoindentation [30][31][32]. Furthermore, digital image correlation (DIC) was used to analyze the strain field in the proximity of the crack tip [16,29,30,[33][34][35][36][37] and special correlations methods were developed to estimate the effective stress intensity factor (SIF) [30,[34][35][36][37] by a fitting to the William's solution [38].…”

“…The SIF range was also computed by linear elastic fracture mechanics (LEFM) as well as by a special analytical method for SMAs [50,51]. It was shown that this latter method can be successfully used to analyze both fracture properties and fatigue crack propagation of austenitic NiTi SMAs [34,35]. However, the method is applied for the first time in this study to analyze the effects of nonlinear crack-tip transformation phenomena in martensitic NiTi alloys.…”

Inverse problems with the digital image correlation: approach and applications

“…The mixed mode generalized stress intensity factors (GSIF) was experimentally evaluated from DIC displacement and strain fields by means of a path independent integral in [33]. An over-deterministic approach, based on the least square regression of the DIC measured displacement, was also applied to estimate the stress intensity factor of non-conventional materials such as Shape Memory Alloys (SMA) and super-alloys [34][35][36][37][38][39][40][41][42][43], where common elastic and/or elastic-plastic theories cannot be directly applied. Similar approaches have been used for the estimation of the elastic constants of brittle materials by means of Brazilian tests [44][45][46][47].…”