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为了识别不同的损伤模式,采用声发射技术对AZ31镁合金拉伸开裂过程进行实时监测。结果显示,拉伸开裂经历了弹性变形、塑性变形、微开裂、稳定扩展和失稳扩展的损伤过程。通过声发射的多参数分析,确定了4种损伤模式,即塑性变形、微开裂、稳定扩展和失稳扩展。位错滑移导致的塑性变形信号幅度小于70 d B,而孪晶信号的幅度位于70~100 d B之间。微开裂信号能量位于2400到4100 a J之间,而信号上升时间小于800μs。稳定裂纹扩展信号具有较高的峰值前计数,主要分布在20~50范围内,而其振铃总计数却较低,主要分布在20~2000范围内。裂纹失稳扩展信号的平均频率分布在100 k Hz左右,持续时间在2000~105μs范围内。还对不同开裂阶段的损伤机理和声发射源进行了讨论。通过实验测试和讨论,利用不同的声发射信号参数,可以有效识别镁合金开裂过程中同时出现的不同损伤形式。
In order to identify different damage modes, real-time monitoring of AZ31 magnesium alloy tensile cracking process was conducted by using acoustic emission technique. The results show that the tensile cracking has undergone the damage process of elastic deformation, plastic deformation, micro-cracking, stable expansion and instability expansion. Through the multi-parameter analysis of acoustic emission, four kinds of damage modes were identified, namely plastic deformation, micro-cracking, stable expansion and unstability expansion. The amplitude of plastic deformation caused by dislocation slip is less than 70 d B, while the amplitude of twin signal is between 70 and 100 d B. Microdissection signal energy lies between 2400 and 4100 aJ, and the signal rise time is less than 800 μs. The stable crack propagation signal has a high pre-peak count, mainly distributed in the range of 20-50, while its ringing total count is low, mainly distributed in the range of 20-2000. The average frequency distribution of cracked propagating signals is about 100 k Hz and the duration is in the range of 2000-105 μs. The damage mechanisms and acoustic emission sources at different cracking stages are also discussed. Through experimental tests and discussions, different acoustic emission signal parameters can be used to effectively identify different damage modes that occur simultaneously in the cracking process of magnesium alloys.