初始应力对瑞利波无损评价45钢表层应力的影响

基于瑞利波声弹效应理论,在瑞利波无损表征45钢表层应力的基础上分析了45钢表层初始应力状态对应力评价结果的影响。采用声程固定不变中心频率为5MHz的双瑞利波探头对45钢表层应力进行评价,在归一化互相关函数基础上计算了应力引起的瑞利波信号间时间差。结果表明:初始应力不会影响瑞利波在45钢表层中传播速度随拉伸应力的变化规律,即随拉伸应力的增加,瑞利波在45钢表层中的传播速度基本呈线性规律增加,当应力达到一定值时,再随应力的增加,瑞利波传播速度不再呈线性规律变化;但初始应力和去应力退火状态45钢的名义瑞利波声弹性系数不同,分别为0.838和1.041,最大时间差对应的应力值也不同,去应力退火前后应力评价结果的误差约为22%。

Influence of Initial Stress on Surface Stress Measurement of 45 Steel by Rayleigh Wave

Based on Rayleigh wave acoustoelastic theory,surface stress measurement of 45 steel and the influence of initial stress state on stress measurement were introduced.Two Rayleigh wave transducers with 5MHz frequency,the fixed distance,were employed to detect the surface of 45 steel as an emitter and a receiver.The difference in time of flight between free loaded signal and loaded signal corresponding to different tensile stress was determined with normalized cross correlation function.Results show that the influence of initial stress state on relationship between propagation velocity of Rayleigh wave and tensile stress is faint,the propagation velocity of Rayleigh wave increases linearly with tensile stress increasing,when tensile stress attains a value,the relationship between velocity of Rayleigh wave propagating in the surface of 45 steel and tensile stress is nonlinear further.Nominal Rayleigh wave acoustoelastic coefficients corresponding to different initial stress state of 45 steel are obtained,and they are 0.838 and 1.041,respectively.The stress corresponding to the maximum difference in time of flight is also different,the relative error of stress measurement corresponding to different initial stress state is about 22%.