Abstract

Longitudinal and shear ultrasound pulse velocity (UPV) were measured in concrete under tensile stresses. 17 beams made of 7 mixtures were tested under flexural tensile loading until failure while UPVs were recorded. At low stresses, before 30% of the maximum tensile stress, mixtures showed acoustoelastic response, with linear UPV variation as the stress increased. Beyond 30% of the maximum load UPVs started to decay, indicating the degradation of the material due to the onset and propagation of microcracks. Close to failure, mixtures presented an even steeper UPV decay, indicating the degradation of the elastic properties. Measured third-order elastic constants indicate a high acoustoelastic sensitivity of concrete under tensile stresses. The different magnitudes of the third-order parameters of the mixtures demonstrate the potential of acoustoelasticity in ultrasonic investigation of concrete. Results also proved that mechanical damage due to tensile stresses, beyond the acoustoelastic region, induce a decrease in both Lame constants.

中文翻译：

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拉应力下混凝土非线性弹性行为对纵向和剪切超声脉冲传播的影响

摘要

在拉伸应力下测量混凝土的纵向和剪切超声脉冲速度（UPV）。在挠性拉伸载荷下测试了由7种混合物制成的17个梁，直到记录UPV失败为止。在低应力下，在最大拉伸应力的30％之前，混合物表现出声弹性响应，随应力增加线性UPV变化。超过最大载荷的30％，UPV开始衰减，表明由于微裂纹的发生和传播，材料的降解。接近破坏时，混合物呈现出更陡峭的UPV衰减，表明弹性性能下降。测得的三阶弹性常数表明混凝土在拉伸应力下具有很高的声弹性敏感性。混合物的三阶参数的大小不同，证明了在超声研究混凝土中声弹性的潜力。结果还证明，由于拉伸应力引起的机械损伤（超出声弹性区域）导致两个Lame常数均减小。