基于非线性超声技术损伤钢筋混凝土无损检测的适用性研究

Research of applicability of non-destructive testing for damaged reinforced concrete basd on nonlinear ultrasonic technology

以27个钢筋混凝土试件拉拔试验和1个立方体试块分级加载试验为基础,利用ZBL-U520非金属超声检测仪对试件进行无损检测,分析了接收器频率、发射电压对激发二次谐波的影响,以确定仪器最佳设置参数.在此基础上利用非线性超声技术,对不同荷载水平下的试件损伤进行了无损检测,研究了考虑锈蚀率以及荷载损伤的二次谐波和非线性系数变化关系,验证了非线性超声技术在钢筋混凝土无损检测中的适用性.结果表明:接收换能器频率为发射换能器2倍时,激发二次谐波效果更佳;对比不同发射电压(65 V、125 V、250 V、500 V、1 000 V)的频谱图,发现随着发射电压增加二次谐波幅值也增加,因此在仪器允许范围内要获得较为精确的非线性超声特征参数,选取发射电压1 000 V.随着试件锈蚀率和拉拔力增加,二次谐波幅值和非线性系数呈非线性变大趋势;配箍率和保护层厚度增加,试件二次谐波和非线性系数增加缓慢,反之二次谐波和非线性系数增加较快.试验分析表明:利用非线性超声技术对钢筋混凝土检测得到的非线性超声特征参数去表征试件损伤程度是较为准确和合适的.

Based on the test results of 27 RC pullout test specimens and a cube block of step loading, the specimens with ZBL-U520 non-metallic ultrasonic detector were non-destructivly tested. The effects that the second harmonic was excited by receiver frequency and transmitter voltage were analyzed so as to determine the suitable test parameters. On the basis of the analysis , the specimens of different corrosion rates with nonlinear ultrasonic technology were non-destructively tested and non corroded specimens graded injury were non-destructively tested under a pullout test. The relationship of nonlinear ultrasonic characteristic parameters （the second harmonic and nonlinear coefficients） and different corrosion rates, different load damage were studied,applicability of nonlinear ultrasonic technology applied RC Non-destructive testing was verified. The results show that the receiving transducer frequency equals the transmitting transducer 2 times more than the second harmonic. Compared with the with spectrums of different voltage （65 V, 125 V,250 V,500 V,1 000 V）,it can be found that with the increase of transmitting voltage, the amplitude of the second harmonic also increased . So the emitter voltage is positioned 1 000 V to obtain more accurate nonlinear ultrasonic characteristic parameters within the limits permitted by the instrument.The second harmonic amplitude and nonlinear coefficient increases nonlinearly with the increase of corrosion rating and pulling force. The second harmonic amplitude and nonlinear coefficients of the specimens increased slowly under higher stirrup ratio and while thicker protective layer. In contrast,Increased rapidly,Tests showed that it’s accurate and suitable to characterize the damage degree of reinforced concrete by using nonlinear ultrasonic technology to measure nonlinear ultrasonic characteristic parameters.