Computer-controlled elastic-plastic fatigue crack growth testing using multi-task programming

Conclusions

The automated test system for computer-controlled low-cycle fatigue crack growth can be achieved using multi-task programming. The results of constant ΔJ test show the degree of success achieved with this system. This automated system integrates the ΔJ range in real time and controls it. It was shown that task priorities in the multi-task system gave great efficiency in developing the automated elastic-plastic fatigue crack growth system. The test system described herein was used to produce results of the constant ΔJ test for the material of JIS SM41B. The crack growth rates remained constant for many constant ΔJ tests as expected. This shows the effectiveness of the developed system. In these elastic-plastic crack growth rate experiments, the property of the closure load was also analyzed and was shown to be always compressive and to be a function of both the magnitude of ΔJ and crack length. An availability of such precise analysis for crack closure behavior is also a great advantage of using a multi-task system.