FATIGUE CRACK CLOSURE ANALYSIS USING NONLINEAR ULTRASOUND
FATIGUE CRACK CLOSURE ANALYSIS USING NONLINEAR ULTRASOUND
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DOI：
10.1063/1.1711761
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发表时间：
2004-04
期刊：
影响因子：
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通讯作者：
Masashi Akino;T. Mihara;K. Yamanaka
中科院分区：
文献类型：
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作者：
Masashi Akino;T. Mihara;K. Yamanaka
非线性超声是评价闭合裂纹的一种很有前途的工具，而线超声很难评价闭合裂纹。最近，人们观察到亚谐振动，并用参数振动或强迫振动对其进行解释。然而，由于裂纹没有完全闭合，裂纹行为复杂，理论和实验还没有达到定量的对比。通过对裂纹尖端回波的原位监测控制裂纹张开，制备了铝合金闭合疲劳裂纹。当6.4 MHz的纵波斜入射到闭合裂纹上时，观察到3.2 MHz的强次谐波。当施加拉应力减小裂纹闭合时，强度先增加，最大值大于基波，然后随着裂纹的进一步张开而适度减小。从理论上用输出裂纹面因惯性而产生的低通滤波位移解释了亚谐强度。
Nonlinear ultrasound is a promising tool for evaluating closed cracks which is difficult with the linear ultrasound. Recently, subharmonics was observed and explained either by a parametric or a forced vibration. However, because the crack was not completely closed, the behavior of crack was complicated and quantitative comparison between theory and experiment has not been achieved. We prepared a closed fatigue crack in an aluminum alloy by controlling the crack opening with in‐situ monitoring of the crack tip echoes. When a tone burst of 6.4 MHz longitudinal waves was obliquely incident on the closed crack, a strong subharmonics at 3.2 MHz was observed. The intensity first increased as the crack closure was reduced by applying a tensile stress, took a maximum larger than the fundamental wave and then decreased moderately as the crack was further opened. The subharmonic intensity was theoretically explained by a low‐pass filtered displacement of output crack plane due to the inertia when it is driven by v...