G0301-6-1 Correlation of Notch Strength Ratio with Critical Strain Ratio

Abstract

The notch tip critical strain was measured at the notch tensile strength for the notched specimens with notch root radius of 0.1 mm to investigate the correlation of notch strength ratio with critical strain ratio. Critical strain ratio was defined as the ratio of critical strain at the notch tip to plastic strain at necking instability, which is numerically equal to strain hardening exponent. The plastic strain distribution below the notch tip was obtained from measurements of Vickers hardness through the calibration curve of plastic strain with hardness. The plastic constraint derived from strain localization due to low rate of strain hardening raised the critical strain ratio at the notch tip. Thus, the critical strain ratio could be a suitable measure to express the intensity of plastic constraint, and increased sharply with decreasing strain hardening exponent. Hence, the notch strength ratio, defined as the notch tensile strength to tensile strength ratio, increased with increasing critical strain ratio for the notched specimens with various strain hardening ability.