A new significant method of online stress monitoring based on acoustoelastic theory for cylindrical guided wave was proposed aim at the deficiency of steel structure online stress monitoring. The disperse curves of?20 Q235 steel bar were calculated, the frequency ranges fit for acoustoelastic detection of cylindrical guided wave were optimized. According to acoustoelasticity motion equation and Pochhammer frequency equation, the group velocities of longitudinal L(0,1) mode, flexural F(1,1) mode and torsional T(0,1) mode in different stress level were calculated and simulated by theoretical equation and finite element software, and the acoustoelastic coefficients were obtained. The results show that longitudinal L(0,1) mode guided wave is fit for acoustoelastic axis stress monitoring, flexural F(1,1) mode and torsional T(0,1) mode are weak in acoustoelastic effect. Acoustoelastic effect of longitudinal L(0,1) mode is decreasing with the increasing of frequency. The results of theoretical and finite element simulation are consistent well with axial displacement of mode shapes for acoustoelastic effect.%大型钢结构在役应力检测意义重大,基于超声导波声弹性效应进行应力检测具有潜在的优势.该文基于等效弹性常数法研究了杆中超声导波的声弹性效应.通过计算Q235钢结构构件钢杆的频散曲线,确定了检测频率范围,并对不同工作应力状态下L(0,1)、F(1,1)与T(0,1)模态的群速度值进行了理论分析与数值模拟.结果表明:L(0,1)模态较适合于钢杆轴力检测,F(1,1)、T(0,1)模态声弹性效应较弱,不适合于应力检测;L(0,1)模态的声弹性效应随着频率的增加而减弱;通过理论分析与有限元计算对声弹性效应的验证都与波结构轴向位移对声弹性效应的判断得到了较好的吻合.
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