Micromechanical Analysis of Crack Closure Mechanism for the Intelligent Material Containing TiNi Fibers. 2nd Report, Numerical Calculation of the Stress Intensity Factor in the Process of Shape Memory Shrinkage of TiNi Fibers.

Abstract

In the previous study, micromechanical modeling of the intelligent material containing TiNi fibers was performed and the stress intensity factor K1 could be expressed in terms of the magnitude of shape memory shrinkage of fibers and the thermal expansion strain occurred in the material. In this study, by using the analytical results, the value of K1 will be numerically calculated. As a result, we can see that the K1 value decreases with increasing in the shrink strain of fibers. This tendency agree with that of the experimental result obtained by Shimamoto et al. Moreover, it can be seen that there exists the optimal value of shrink strain of fibers to make the K1 value zero. The change in K1 with temperature during heating process to the inverse austenitic temperature of TiNi fiber is also consistent with the experimental result. The results obtained can be explained by the shrink strain, the thermal expansion strain, and the elastic moduli of TiNi fiber. These results may be useful in designing the intelligent material containing TiNi fibers from the viewpoint of crack closure.