疲劳裂纹闭合的非线性超声在线测量

建立了外部载荷作用下用非线性振动-声场调制指数表征裂纹尺寸的数学模型。根据对外载荷与塑性致闭应力共同作用下裂纹面的开闭响应的分析，提出了裂纹张开和闭合应力的在线测量方法。在一块含中心穿透裂纹的铝合金薄板试件上进行了裂纹闭合参数的测量实验，实验结果表明，使用振动-声场调制技术在线测量裂纹闭合参数是可行且有效的，且该方法还能用于分析小裂纹的特殊开闭行为。
A mathematical model which displays the relation between the vibro-acoustic modulation index and the crack contact area was developed. Based on the analysis of crack faces response to the resultant of applied load and plasticity induced crack closure stress, a procedure of on-line approximating the opening and closure stress was proposed. To study the performance of this measuring method experimentally, the on-line vibro-acoustic modulation tests were carried out on a central cracked aluminum alloy fatigue sample. Analysis of the experimental results suggests that the vibro-acoustic modulation technology is not only capable of measuring the fatigue crack opening and closure stresses, but also capable of analyzing the crack closure behavior, even for physically short cracks.