循环冲击下大理岩的损伤力学行为及能量耗散特性

Dynamic behaviors and energy dissipation characteristics of marble under cyclic impact loading

为了研究循环冲击荷载作用下大理岩的动态力学行为和能量耗散特性,首先采用分离式霍普金森压杆,通过试冲法确定出5种代表性的入射子弹速度,据此完成了大理岩试样的等幅循环冲击试验,并对试样的应力均匀性进行了检验。接着,从应变率时程曲线、应力-应变关系、冲击次数和能量耗散特性等方面对测试数据进行了系统分析。最后,基于能量演化定义损伤变量,探讨了能量耗散与岩样损伤发展之间的关联机制。结果表明:试样应变率时程曲线在低弹速下会出现变化率恒定的平台段,应力-应变曲线在峰后阶段均产生一定的回弹;随着循环次数的增加,试样峰值应力总体减小,而峰值应变、平均应变率和累积比能量吸收值则变化趋势相反,且在临近破坏或开裂前其变化速率呈现突增现象;峰值应力与平均应变率存在明显的线性关系,弹性模量随平均应变率的变化整体上符合指数衰减规律;试样的耗散比能与平均应变率之间呈线性正相关,基于能量耗散定义的损伤变量可以较好地表征该大理岩试样动载下的损伤破坏过程。

In order to study the dynamic behaviors and energy dissipation characteristics of marble under cyclic impact loading,a split Hopkinson pressure bar system was first adopted to determine the five representative incident velocities of striking projectile through the trial impact method.Based on this,constant amplitude cyclic impact tests of the marble samples were performed,and stress uniformity of the samples was examined.Then,a systematic analysis is conducted on the test data from the aspects of strain rate time history curve,stress-strain relationship,impact times and energy dissipation properties.Finally,a damage variable is defined based on the energy evolution,and the associated mechanism between energy dissipation and damage development of the rock samples is further explored.The results show that the time-history curves of the strain rate of the samples exhibit a plateau segment with a constant rate of change at low projectile velocities,and the stress-strain curve has a certain rebound at the post-peak stage.The peak stress of the rock samples decreases with the increase of the number of cycles,while the peak strain,average strain rate and cumulative absorption specific energy take on the opposite trend,and their change rates all show a sudden increase phenomenon before sample’s break or fracture.The peak stress has a linear relationship with the average strain rate,while the variation of sample elastic modulus with average strain rate generally follows an exponential decay law.There is a positive linear correlation between the dissipated specific energy and the average strain rate of the marble samples.The damage variable defined based on energy dissipation analysis can better characterize the break or fracture process of the marble samples under dynamic loading.The research results of this study have certain reference value for revealing the evolution mechanism of rock internal damage under cyclic load disturbance.