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为满足评价承压钢材高温蠕变损伤的需求,建立了一种利用有限元来计算钢材高温热损伤的非线性超声效应的方法。非线性现象是由于材料的微结构变化导致的波形畸变,即高频谐波的产生,其随着传播距离的增大而累积。据此建立了P91钢经过高温蠕变的理论模型和非线性超声的二维理论模型,对P91钢进行高温热损伤的模拟仿真,对超声换能器和超声波在损伤钢材试样中的传播进行了有限元仿真,分析了在经过高温蠕变损伤后的钢材试样中声场的分布情况,对回波信号进行频谱分析发现明显的二次谐波分量,研究了热处理温度和非线性系数的关系。理论和实验结果都表明:随着热处理温度的升高,非线性系数逐渐增大,承压钢材的蠕变损伤程度加深,因此可将非线性效应作为有效评价材料高温蠕变损伤的特征参数。
In order to meet the need of evaluating creep damage of high temperature steel under pressure, a method of calculating nonlinear ultrasonic effect of high temperature heat damage of steel by finite element method was established. Nonlinear phenomenon is due to the microstructure of the material caused by the waveform distortion, that is, the generation of high-frequency harmonics, which increases with the propagation distance of accumulation. Based on this, the theoretical model of high temperature creep of P91 steel and the two-dimensional theoretical model of nonlinear ultrasonic were established. The simulation of high temperature thermal damage of P91 steel was carried out. The propagation of ultrasonic transducer and ultrasonic wave in damaged steel samples The finite element simulation was used to analyze the distribution of sound field in steel samples after creep damage at high temperature. The second harmonic component was found by spectrum analysis of the echo signal. The relationship between the heat treatment temperature and the nonlinear coefficient . Both theoretical and experimental results show that as the heat treatment temperature increases, the nonlinear coefficient increases gradually and the creep damage of the steel under pressure increases. Therefore, the nonlinear effect can be used as a characteristic parameter to effectively evaluate the creep damage at high temperature.