基于声发射技术的混凝土剪切损伤研究

Study of concrete shear damage based on acoustic emission technique

为研究混凝土的受剪损伤演化情况,同时定量评估混凝土的剪切损伤,对C40、C50和C60这3种强度的Z型混凝土试件进行直剪试验,并利用声发射(AE)技术对试件剪切破坏区域的破坏演化规律进行动态分析。同时,根据试件受剪损伤时释放的声发射信号与能量,定性地分析材料的损伤演化状况,以累计振铃计数为基础,建立损伤演化方程,并利用ABAQUS软件对试验过程进行模拟验证。研究结果表明:不同强度的Z形素混凝土试件均表现为脆性破坏形式。在达到极限荷载之前,试件表面未出现明显的裂缝,一旦达到极限荷载后,沿着剪切截面迅速发展出上下2条裂缝,最终导致试件迅速破坏。累计声发射能量与累计振铃计数曲线均呈现线弹性、稳定增长、爆发增长三阶段变化。随着混凝土强度的提高,声发射振铃计数与声发射能量在混凝土的损伤稳定增长阶段也随之增大,同时,累计声发射能量与累计振铃计数曲线的拐点也愈发明显。基于声发射参数累计振铃计数与应力的关系,采用指数函数建立混凝土剪切损伤演化模型,并将该剪切损伤模型代入塑性损伤FEA模型中,对比分析剪切破坏过程和荷载−应变关系与损伤演化发展情况。结果显示模拟值与实测值吻合良好,论证了基于声发射技术的混凝土剪切损伤模型的准确性,同时表明该模型具有良好的应用前景。

In order to study the shear damage evolution of concrete and also to quantitatively assess the shear damage of concrete,straight shear tests were carried out in this paper on Z-type concrete specimens of three strengths,C40,C50 and C60.The damage evolution law in the shear damage region of the specimens was dynamically analyzed by using acoustic emission(AE)technology.Meanwhile,this paper qualitatively analyzed the damage evolution condition of the material according to the acoustic emission signal and energy released when the specimen was damaged by shear,established the damage evolution equation based on the cumulative ringing counts,and simulated and verified the test process using ABAQUS software.The results show that the Z�shaped vein concrete specimens with different strengths exhibit brittle damage.Before the ultimate load is reached,no obvious cracks appear on the surface of the specimen;however,once the ultimate load is reached,the upper and lower cracks along the shear cross-section develop rapidly,which ultimately leads to the rapid damage of the specimen.The cumulative acoustic emission energy and cumulative ringing counts curves show the three�phase changes of linear elasticity,steady growth,and bursting growth.With the increase of concrete strength,the acoustic emission ringing counts and acoustic emission energy in the steady growth stage of concrete damage also increases.Meanwhile,the inflection point of the curves of cumulative acoustic emission energy versus cumulative ringing counts also becomes increasingly profound.Based on the relationship between the cumulative ringing counts of the acoustic emission parameters and the stress,this paper adopted the exponential function to establish a concrete shear damage evolution model,and substituted the shear damage model into the FEA model of plastic damage to compare and analyze the shear damage process and the load-strain relationship with the development of damage evolution.The results show that the simulated values are in good agreement with the measured values,which demonstrates the accuracy of the concrete shear damage model based on the acoustic emission technology;meanwhile,it shows that the model has a promising application prospect.