混凝土压缩试验的改善及动态损伤

为了探求混凝土动态压缩试验入射波形的改善方法,从而进一步研究冲击荷载作用下混凝土动态损伤及力学性能,采用常规的大直径分离式霍普金森压杆(split Hopkinson pressure bar, SHPB)进行混凝土的动态压缩试验。然而入射脉冲的弥散效应和严重的高频震荡现象会对试验结果会产生较大的误差,所以试件在破坏前应力均匀分布要求且保持恒应变率加载是保证试验有效性及试验结果可靠性的关键。通过黄铜整形器改善入射波形以减小试验误差,然后利用理论公式与试验相结合的方式,通过控制变量,进一步研究气压、冲击次数等对混凝土动态损伤的影响。研究结果表明:较薄的小直径实心铜片整形器可以提高试验准确度;随着重复冲击次数的增加,混凝土损伤度逐渐提高,动态弹性模量减小,抵抗冲击的能力减弱。

Improvement method of compression test and the dynamic damage of concrete

In order to explore the incident waveform improvement method in concrete dynamic compression test thus further exploring the dynamic damage and the mechanical property of concrete under the impact loading, the experiment adopted the conventional large diameter split Hopkinson pressure bar(SHPB)to study the dynamic compression test of concrete. The dispersion effect of the incident pulse and the serious high frequency oscillation phenomenon causes large errors in the result of the experiment, but it is the key to ensure the validity of the test and the reliability of the test results to ensure the uniform distribution of stress and to maintain the constant strain rate loading before the test piece destroyed. This study used the brass shaper technology to improve the incident wave to reduce the experimental error and then by controlling variable, then used the method of the combination of theoretical formula and experimental, further researched on the influence of air pressure and impact times on the dynamic damage of concrete. It was concluded that the shaper made of small diameter solid copper thin could improve the accuracy. The damage degree of concrete was gradually augmented with the increase of the repeated impact times the dynamic elastic modulus was decreased, and the ability to resist impact was attenuated.