单边缺口板材试样的J积分试验标定

 单边缺口试样的J积分,当取其缺口内表面为积分回路时,有特别简单的形式,即,并可进一步简化为,其中。 本文对两种单边缺口试样（缺口根部曲率半径ρ分别为20毫米和9毫米）,测定了缺口内表面的应变分布ε（θ）,再经应力-应变曲线转换成形变功密度分布W（θ）,最后通过数值积分求出系数A。试验结果与考虑了Weiss塑性区修正的线弹性断裂力学方法做了比较。

J-INTEGRAL EXPERIMENTAL CALIBRATION OF SHEET SPECIMENS WITH SINGLE EDGE NOTCH

J-integral of sheet notched specimen has the simplest form when the notched surface has been taken as the integral contour, i. e.it can be still simplifiedwhereandit can be seen that the ratio of J-integral to radius of curvature P is proportional to the maximum deformation work density W0 at notch root.The specimens were cut from hot rolled sheet of aluminium alloy LY12 with yield strength σ0.2=11.2 kgf/mm2. The specimen sizes are: thickness B = 30mm, width W= 150mm, notch depth a=40mm, and the radiuses of notch curvature ρ=20mm and 9mm, respectively. The resistance strain gauges of 1 by 1mm were adhibited on the inner surface of notch at angles θ being 0°, 10°, 20°, 30°, 45°, 60°, 75° and 90°, respectively. And then, the measurement of strain distribution ε（θ） at various load levels was made and deformation work density distribution W（θ） was derived from stress-strain curve. The value A, at last, has been determined by means of numerical integration and the approximation function, and varied in a range of 0.9 to 1.2.Owing to the limitation of the experimental accuracy and the difficulty in determining exact degree of plane strain, the agreement of experimental calibration of J-integral in the present work with J converted from equivalent stress intensity factor Keff considering Weiss's correction of plastic zone can be considered as an approximation for engineering.