The opening mode stress intensity factor extraction method from mixed mode crack using single element strain gage.

Abstract

Previously, the authors developed a strain gage (K-value gage) that can analyze the open mode stress intensity factor exclusively. This K-value gage was designed as a one-element strain gage with a gage width of 1 mm and a grid angle of 104° curvature. This paper presents an analysis method that can extract only the opening mode stress intensity factor from mixed mode (opening + shearing) cracks using the developed K-value gage. The extraction analysis method using this K-value gage was derived for the case of Poisson's ratio of the material to be measured 0.3. At the same time, Poisson's ratio led to use other than 0.3. Furthermore, this paper verified the validity of the proposed analysis method from experiments using a K-value gage. In the comparative verification experiment with the theoretical value, a tensile test was performed by inserting simulated cracks of the same length with only the inclination angle changed in a flat plate test piece. As a result, the experimental values of the aperture mode stress intensity factors were obtained within ±10% of the theoretical values.

Keywords

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