外表面ひずみ測定による内表面き裂の成長モニタリング（その２：多点ひずみ測定法による疲労き裂進展のモニタリング）

概要

論文の詳細を見る
A monitoring method using strain gages has been proposed by the present authors. This method estimates the crack depth from the change in outside strains due to internal pressure. From a combination of two strains obtained at different position, the surface length in addition to the crack depth can be estimated. A Monte Carlo technique revealed that the accuracy of the estimation could be improved by using several gages. In this study, the validity of the monitoring method using multiple strain gages, which was referred to as the multiple strain measurement method, was shown by the fatigue crack growth test. A pipe with axial cracks was subjected to a cyclic internal pressure. The strains were measured on the outside surface during the crack growth test. Then, the crack size was estimated using the measured strains and the correlation between the strain and crack size, which was obtained by the finite element analyses. The estimated crack size was compared with the test results, which was identified by beach marks introduced during the test. Although, the change in the surface length could be monitored by the strain measurements, the maximum error was 3.2 mm in the estimation of the crack depth. It was deduced that the error was caused by the difference between the test conditions and the finite element model. The estimation error could be reduced by considering the weights in the estimation procedure.