A comparison of acoustic and strain gauge techniques for crack closure
A comparison of acoustic and strain gauge techniques for crack closure
复制标题
裂纹闭合的声学技术和应变仪技术的比较
DOI：
10.1007/bf00038901
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发表时间：
1975
影响因子：
2.5
通讯作者：
O. Buck
中科院分区：
文献类型：
--
作者：
J. Frandsen;R. Inman;O. Buck
正应力水平下的裂纹闭合[i]目前正在研究，作为解释试验条件变化引起的疲劳裂纹扩展速率变化的机制。柔度[i-3]、电阻率[4-6]、光学[7，8]和声学[9，10]测量广泛用于监测裂纹扩展，产生有关裂纹闭合的信息。然而，由于涉及不同的监测技术、样品几何形状、材料等，各种结果之间的相关性相当困难。在本研究中，上述裂纹监测技术中的两种用于两种不同的样品几何形状，PTC [I 0]和CT [ii]，以及两炉A1 2219-T851，但在其他方面测试条件相同，PTC样品中的裂纹闭合通过声表面波技术（500 kHz）监测[9]，CT样品中的裂纹闭合使用纵向体波（2.25 MHz），利用透射和反射声束，参见图i。两个顺应性测量仪，传统的开口夹式测量仪和埃尔伯型测量仪[i-3]，安装在CT样本上。在空气（5%相对湿度）中以R= Omin/Sma x值0.08、0.30和0.50进行测试。
Crack closure at positive stress levels [i] is currently being investigated as a mechanism to explain variations in fatigue crack growth rate caused by changes in the testing conditions. Compliance [i-3], resistivity [4-6], optical [7, 8], and acoustical [9, 10] measurements, extensively used to monitor crack growth, yield information about crack closure. Correlation between the various results is quite difficult, however, since different monitoring techniques, sample geometries, materials, etc. have been involved. In the present investigation two of the above crack monitoring techniques are used on two different sample geometries, PTC [I0] and CT [ii], and two heats of A1 2219-T851, but otherwise equal testing conditions, to characterize closure more fully.Crack closure in PTC samples was monitored [9] by an acoustic surface wave technique (500kHz) and in CT samples using longitudinal bulk waves (2.25 MHz), utilizing both the transmitted and the reflected acoustic beam, see Fig. i. Two compliance gauges, the conventional mouth opening clip-on gauge and an Elber-type gauge [i-3], were mounted on the CT specimen. Testing was done in air (5% relative humidity) at R= Omin/Sma x values of 0.08, 0.30, and 0.50.