基于非线性兰姆波的热双金属残余应力表征

Characterization of Residual Stressin Thermostat Metal Based on Nonlinear Lamb Waves

该文研究了热双金属带材的兰姆波非线性效应与温度、应力的关系,建立了非线性超声检测系统,结合X线衍射(XRD)法确定应力值。将热双金属分别加热到100℃、200℃和310℃,保温1 h后空冷,对比不同温度对非线性系数的影响,分析常态和热处理降应力后热双金属的非线性系数和应力值的关系。实验结果表明,热双金属在常温和经100℃、200℃加热后的非线性系数基本不变,而经过310℃稳定化热处理降低应力后,非线性系数明显降低;验证了热双金属中兰姆波二阶、三阶非线性系数对应力值敏感且随应力增大而增大,其均可用于表征残余应力状态;根据应力值与非线性系数的关系得到拟合函数,并验证了通过拟合函数计算应力的可行性,这为使用非线性系数评估应力提供了一种参考方法。

The relationship between the nonlinear effect of Lamb wave and temperature and stress of thermostat metal strip is studied,and the nonlinear ultrasonic testing system is established,and the stress value is determined by X-ray diffraction method.Heat the thermostat metal to 100℃,200℃and 310℃respectively for one hour and then air cool it.Compare the influence of different temperatures on the nonlinear coefficient,and analyze the relationship between the nonlinear coefficient and the stress value of the thermostat metal under normal conditions and after stress reduction by heat treatment.The experimental results show that the nonlinear coefficient of the thermostat metal under normal temperature and after heating at 100℃and 200℃is basically unchanged,but after the stress reduction by heat treatment at 310℃.The nonlinear coefficient is significantly reduced.It is verified that the second-order and third-order nonlinear coefficients of Lamb wave in thermostat metal are sensitive to the stress value and increase with the increase of stress,which can be used to characterize the residual stress state.The fitting function can be obtained according to the relationship between the stress value and the nonlinear coefficient,and the feasibility of calculating the stress through the fitting function is verified,which provides a reference method for using the nonlinear coefficient to evaluate the stress.