Fatigue damage assessment by nonlinear ultrasonic materials characterization
Fatigue damage assessment by nonlinear ultrasonic materials characterization
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DOI：
10.1016/s0041-624x(97)00040-1
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发表时间：
1998-02-01
期刊：
影响因子：
4.2
通讯作者：
Nagy, PB
中科院分区：
文献类型：
--
作者：
Nagy, PB
大多数结构材料的极限强度主要受到作为断裂过程核心的微观缺陷的限制。由于这些核比通常用于超声无损评价（NDE）的频率下的声波波长短得多，因此线性声学特性对材料完整性的这种微观退化不足够敏感。另一方面，即使非常小的缺陷也会产生非常显著的过量非线性，其可以比完整材料的固有非线性高几个数量级。超非线性主要是由微裂纹的强局部非线性产生的，微裂纹的开口小于粒子位移。通过裂纹闭合的参数调制显著增加了疲劳材料的应力依赖性。介绍了一种测量塑料、金属、复合材料和胶粘剂等多种材料二阶声弹性系数的特殊实验技术。实验结果表明，非线性声学参数比线性声学参数更早、更敏感地反映了疲劳损伤。(C)1998年Elsevier Science B.V.
The ultimate strength of most structural materials is mainly limited by the presence of microscopic imperfections serving as nuclei of the fracture process. Since these nuclei are considerably shorter than the acoustic wavelength at the frequencies normally used in ultrasonic nondestructive evaluation (NDE), linear acoustic characteristics are not sufficiently sensitive to this kind of microscopic degradation of the material's integrity. On the other hand, even very small imperfections can produce very significant excess nonlinearity which can be orders of magnitude higher than the intrinsic nonlinearity of the intact material. The excess nonlinearity is produced mainly by the strong local nonlinearity of microcracks whose opening is smaller than the particle displacement. Parametric modulation via crack-closure significantly increases the stress-dependence of fatigued materials. A special experimental technique was introduced to measure the second-order acousto-elastic coefficient in a great variety of materials including plastics, metals, composites and adhesives. Experimental results are presented to illustrate that the nonlinear acoustic parameters are earlier and more sensitive indicators of fatigue damage than their linear counterparts. (C) 1998 Elsevier Science B.V.