Notch Root Biaxial Cyclic Strain Behavior of Type 304 Stainless Steel at Elevated Temperature by Using Laser Speckle Strain/Displacement Gauge.

Abstract

A laser speckle biaxial strain gauge was developed to measure local strains at notch roots. Measurements were made on single edge-notched type 304 stainless specimens under fully reversed cyclic loading at both 637 K and room temperature. The change in the cyclic total strain range was more significant when blunt notched specimens were subjected to a higher applied stress. The measured biaxial strains were discussed in terms of a proposed dimensionless notch deformation constraint parameter which consisted of a notch root radius, a thickness of the plate and a nominal stress level. It was found that the biaxial strain ratio was uniquely correlated with the proposed parameter for all the tested notches. It was also found that the change in the cyclic strain range was correlated with the proposed parameter, and the material didn't show cyclic softening or hardening under an increased value of the parameter. Furthermore, the measured strains were compared with the estimated values by the Neuber's rule.