P91钢焊缝蠕变的非线性超声检测

Detection of creep damage in P91 steel weldments using nonlinear ultrasonic technique

分析了金属材料蠕变过程中的非线性应力—应变关系,指出在蠕变超声检测过程中存在非线性波动现象.讨论了使用脉冲超声实现非线性检测的方法,即利用超声检测信号高频段与低频段的能量之比作为非线性的表征.分析了衰减对非线性检测的影响,并根据频率-衰减关系对非线性参数的计算方法做出了修正.应用该方法对不同蠕变状态的P91钢母材及焊缝热影响区进行了检测.结果表明,非线性参数随蠕变时间的增加呈上升趋势;该方法可以有效区分同一材质的不同蠕变状态,可以作为P91钢焊缝蠕变程度相对性检测的有效方法.

Nonlinear stress-strain relation in creeping metal was analyzed. The nonlinear fluctuation in creep damage detection with ultrasound was described. A new nonlinear ultrasonic method using pulse wave was proposed,in which the energy ratio of high frequency band to low frequency band of ultrasonic signal was used to characterize the nonlinearity caused by creeping. The influence of attenuation was discussed,and correction to the new nonlinear ultrasonic method was obtained according to frequency-attenuation relation. The base metal and heat-affected zone( HAZ) of P91 steel weldments in different creeping states were detected with this corrected nonlinear ultrasonic method. And the results showed that the nonlinear ultrasonic parameter increased while the creep time increased,and the new method could distinguish different creep states of the same texture. Therefore,this new nonlinear ultrasonic method could be effective for detecting the creep damage degree of P91steel weldments.