基于应力腐蚀和腐蚀疲劳的焊缝磁记忆信号分析

为了研究不同腐蚀条件下的焊缝磁记忆特征信号,对20号钢板状焊缝试件进行残余应力腐蚀、35kN恒拉伸应力腐蚀和35kN静载、25kN动载拉拉腐蚀疲劳对比实验,分析焊缝正、反面磁记忆信号的变化规律,获得焊缝腐蚀发展进程中应力腐蚀与腐蚀疲劳各自对应的磁记忆特征信号.结果表明:在应力腐蚀状态下,不同拉伸载荷对应的磁记忆信号特征不同,35kN恒拉伸应力腐蚀与残余应力腐蚀相比,焊缝区磁记忆信号峰峰值及其梯度更大,磁记忆曲线分布的分散度更大;35kN静载、25kN动载拉拉腐蚀疲劳与35kN恒拉伸应力腐蚀相比,焊缝区磁记忆曲线上下波动多,过零点次数多,磁记忆曲线分布的分散度小.这为磁记忆技术在焊缝工程检测的定性与定量分析提供基础数据.

MMM signal analysis based on stress corrosion and fatigue corrosion

In order to study the metal magnetic memory(MMM) corrosion characteristic of welded joint,steel 20 plate specimens with welded joints are tested by MMM method under 0 kN residual stress corrosion,35 kN static tension stress corrosion and 35kN dynamic tension-tension fatigue corrosion experiments.The results have showed that MMM characteristics are different with the increasing of tension stress under the stress corrosion experiments.The peak-peak value and gradient of magnetic density at 35 kN are bigger than ones at 0 kN,and dispersion degree of MMM curves are bigger at 35 kN than that at 0 kN.Compared with stress corrosion,MMM signals of fatigue corrosion have more up and down fluctuates and more zero values at the critical stage of welded joint cracking,but the dispersion degree of MMM curves are smaller.These MMM corrosion experimental results have provided the foundational data for qualitative and quantitative analysis with MMM method in practical engineering.