含单侧预制裂纹梁的冲击动态断裂过程试验研究

第一作者 李清 男，教授，1969年生

通信作者 张迪 男，博士，1987年生

邮箱：540375465@qq.com

含单侧预制裂纹梁的冲击动态断裂过程试验研究

李清，张迪，杨阳，郝建伟，薛耀东，王强勋，李进宇

(中国矿业大学 力学与建筑工程学院，北京100083)

摘要：利用动焦散线试验方法研究了冲击下预制裂纹梁的动态断裂行为，对比分析了冲击荷载作用下单裂纹与双裂纹试件的应力强度因子、扩展轨迹以及速度、加速度等参数的变化规律。试验结果表明：冲击荷载作用下，含双裂纹且主裂纹在冲击点正下方的试件起裂时间最早，裂纹扩展后期朝向次裂纹方向发生较小的偏移；含Ⅰ型单裂纹的试件起裂时间次之，裂纹扩展路径呈直线；含双裂纹且两条裂纹均偏置于冲击点的试件起裂时间最晚，扩展过程中发生明显的曲裂现象。同时，裂纹扩展过程中曲裂现象越严重，裂纹扩展的最大速度就越小。在落锤冲击试件到试件断裂的整个阶段，应力强度因子一直表现出振荡变化。含双裂纹的试件，在主裂纹扩展中期，次裂纹上的应力强度因子有一个快速下降的过程。

关键词：预制裂纹；冲击荷载；裂纹扩展；动焦散线

基金项目：国家自然科学基金资助项目(51374212，51134025)

收稿日期：2013-10-09修改稿收到日期：2014-02-20

中图分类号:O348.1文献标志码： A

Dynamic fracture tests for a beam containing unilateral pre-existing cracks under impact loads

LIQing,ZHANGDi,YANGYang,HAOJian-wei,XUEYao-dong,WANGQiang-xun,LIJin-yu(School of Mechanics and Architecture Engineering，China University of Mining & Technology，Beijing 100083, China)

Abstract:By means of experimental method of dynamic caustics, the dynamic fracture behaviors, such as, stress intensity factor, extension track, and crack’s extending velocity and acceleration of precast beams with a single crack and double cracks under impact loads were analyzed comparatively. The experiment results indicated that when the impact point is directly upon the main crack, the double-crack beam’s cracking initiation time is the earliest with a extension track of the main crack slightly offsetting to the secondary crack in the late stage of cracking extension; the single-crack beam of I-type’s cracking initiation time is secondary with a straight line extension track of the main crack; the cracking initiation time of the double-crack beam with two cracks offset to the impact point is the latest with obvious bending fracture; the more serious the bending fracture phenomenon during the process of crack extension, the smaller the maximum extending velocity; in the whole process from the hammer contacting the beams to specimens fracture, their stress intensity factors vary oscillatorily; the stress intensity factors of the secondary crack of the double-crack beam decrease dramatically in the middle stage of the main crack extending.

Key words: pre-existing crack; impact loading; crack propagation; dynamic caustics

梁有着广泛的工程应用，大部分梁结构经常处于冲击荷载的作用下，而含缺陷的梁的动态断裂行为与在静态断裂的情况下有很大的差别[1-4]，这一直是研究的热点。由于裂纹在扩展过程中存在着惯性力，导致裂纹尖端的力学行为十分复杂，单纯的理论计算结果和实际问题相差甚大。……