Development and analysis method of single element strain gage for stress intensity factor analysis in crack opening mode (2nd report, development of grid angle 104° K value gage)

Abstract

This paper shows the development and analysis method of a single element strain gage (K value gage) used to analyze the stress intensity factor of mode I (opening type) cracks. The K-value gage reported in the previous report collected the strain εθ with a grid angle of 52 °, and was able to obtain the stress intensity factor within an error of 10% from the theoretical value. The purpose of this study was to develop a K-value gage with even higher accuracy. As a result, the developed single-element K-value gage had a total grid angle of 104 ° extended to ± 52° from the crack tip extension line. Using the developed 104° K-value gage, two types of experiments were conducted to investigate the analysis accuracy of the stress intensity factor. One is a comparative experiment with a conventional grid angle 52 ° K value gage. The second was to change the simulated crack length of the test piece by three types. The following was found from the experiment. (1) The 52 ° K-value gage had a maximum error of 10% from the theoretical value, while the 104 ° K-value gage was obtained within a maximum of 5%. (2) All three types of test pieces with different simulated crack lengths were obtained within 5% of the theoretical value and the maximum error.

Keywords

• experimental stress analysis
• strain gage
• stress intensity factor
• fracture mechanics
• crack
• experimental mechanics
• stress concentration
• nondestructive inspection
• stress-strain measurement