Acoustic emission from low-cycle high-stress-intensity fatigue
Acoustic emission from low-cycle high-stress-intensity fatigue
复制标题
低周高应力强度疲劳声发射
DOI：
10.1016/0013-7944(73)90050-7
复制
发表时间：
1973
影响因子：
5.4
通讯作者：
P. Crimmins
中科院分区：
文献类型：
--
作者：
C. Hartbower;C. Morais;W. Reuter;P. Crimmins
本文介绍了高级研究计划局 (ARPA) 的一项研究结果，其总体目标是开发一种无损检测技术，以根据声发射确定缺陷的严重性。该研究包括对传感器和仪器系统进行评估，使用几种材料和低周期、高应力强度疲劳加载的材料条件。研究中使用的材料是在 600 和 1100°F 下回火的 D6aC、经过退火、固溶处理和时效的 6A1-4V 钛和 7075-T6 铝。试件为预裂单边缺口拉伸试件；宏观裂纹通过裂纹张开位移（COD）计检测，微裂纹通过声发射检测。声发射系统采用 400 和 1000 kHz 带通滤波，增益为 100 db。使用双笔记录仪将累加器和 COD 计的输出信号记录在单条图上。样品以 6 c/min 的速度进行低周期、高应力强度疲劳。在一些测试中，循环在空气中开始并在水中结束。声发射被证明是一种非常有效的无损检测方法，用于跟踪低周高应力强度疲劳中的裂纹扩展；声发射证实存在休眠期，中间夹杂着活跃的疲劳裂纹扩展期。使用双笔条形图表记录仪在同一张图表上显示裂纹张开位移和应力波计数，不仅可以观察每个单独周期中是否存在裂纹扩展，还可以观察裂纹在周期中的哪个位置发生，这很简单。此外，通过应力波计数率的显着增加，可以很容易地检测到低周期、高应力强度疲劳期间的应力腐蚀开裂过程。在低周期、高应力强度疲劳以及环境辅助疲劳的情况下，证明了声发射作为即将发生失效的前兆的效用。累积应力波计数与周期数的关系图始终显示，骨折前几个（10-20 个或更多）周期的计数率显着增加。
This paper presents the findings of an Advanced Research Projects Agency (ARPA) study, the overall objective of which was to develop a nondestructive testing technique to determine flaw criticality based on acoustic emission. The research included an evaluation of sensors and instrumentation systems, using several materials and material conditions loaded in low-cycle, high-stress-intensity fatigue.The materials used for the study were D6aC tempered at 600 and 1100°F, annealed and solution-treatedand-aged 6A1-4V titanium and 7075-T6 aluminum. The test specimen was the precracked, single-edgenotch tension specimen; macrocracking was detected by crack-opening-displacement (COD) gage and micro-cracking by acoustic emission. The acoustic-emission system utilized 400 and 1000 kHz band-pass filtering at 100db gain. The output signals of the totalizer and the COD gage were recorded on a single strip chart using a dual-pen recorder. The specimens were subjected to low-cycle, high-stress-intensity fatigue at 6 c/min. In some tests, cycling was begun in air and finished in water.Acoustic emission was demonstrated to be highly effective as a non-destructive test method for following crack growth in low-cycle high-stress-intensity fatigue; acoustic emission confirmed the existence of periods of dormancy punctuated by periods of active fatigue crack growth. Using a dual-pen, strip-chart recorder displaying both crack-opening-displacement and stress-wave count on the same chart, it was a simple matter not only to observe if there was crack growth in each individual cycle but also where in the cycle it occurred. Moreover, the process of stress-corrosion cracking during low-cycle, high-stress-intensity fatigue was readily detected by a marked increase in the stress-wave count rate.The utility of acoustic emission as a precursor of imminant failure was demonstrated for low-cycle, high-stress-intensity fatigue as well as for the case of environmentally assisted fatigue. Plots of cumulative stress-wave count vs cycle number consistently showed a marked increase in count rate several (10–20 or more) cycles before fracture.