Development of strain gages to analyze the stress intensity factor of a crack tip

Abstract

There are currently one or two kinds of strain gages to measure the stress intensity factor. It might not be sometimes easy to analyze the stress intensity factor with those gages. In this paper, it is reported that our development of the new stain gage enables us to measure the stress intensity factor more easily and practically. The following features of this strain gage to evaluate the stress intensity factor are presented in this paper. (1) Strain component εr measured around the crack tip is used to calculate the stress intensity factor. (2) To be more specifically, we employed the first and second terms of the series at the strain component εr around the crack tip for an evaluation of the stress intensity factor. The calculation method with using our developed strain gage does not require the crack length. The newly developed strain gage was bonded to around the crack tip of the specimens, where cracks were of the opening mode or the mixed mode. We carried out tensile tests on the test pieces bonded with the gage. In conclusion, the results indicate that the developed strain gage enables us to measure stress intensity factor with an error margin within ±10% of the analytical values.

Keywords

• experimental stress analysis
• strain gage
• stress intensity factor
• fracture mechanics
• crack
• experimental mechanics
• stress consentration
• nondestractive inspection
• stress-strain measurement