节理充填物厚度对运动裂纹扩展的影响

宋彦琦; 李向上; 刘济琛; 王鹏懿

doi:10.11883/bzycj-2019-0358

节理充填物厚度对运动裂纹扩展的影响

doi: 10.11883/bzycj-2019-0358

中国矿业大学（北京）力学与建筑工程学院，北京 100083

基金项目: 国家自然科学基金联合基金（U1704242）；国家重点研发计划（2018YFC0808402）

详细信息

作者简介:
宋彦琦（1969－　），女，博士，教授，songyq@cumtb.edu.cn

通讯作者:
李向上（1991－　），男，博士研究生，xiangshang_li@126.com

中图分类号: O346.1
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出版历程
- 收稿日期: 2019-09-17
- 修回日期: 2019-10-28
- 网络出版日期: 2020-06-25
- 刊出日期: 2020-08-01

Effects of joint filling thickness on crack propagation behaviors

School of Mechanics and Civil Engineering, China University of Ming and Technology (Beijing), Beijing 100083, China

摘要

摘要: 为研究冲击载荷作用下节理充填物厚度对裂纹扩展行为的影响，以石膏为有机玻璃预制裂纹充填物，利用新型数字激光动态焦散线实验系统，对3种不同节理充填物厚度的有机玻璃进行三点弯冲击实验。实验结果表明，相同冲击载荷作用下，竖向预制裂纹均竖直向上扩展，是典型的Ⅰ型裂纹，充填物越厚，竖向裂纹越容易起裂。竖直裂纹扩展至水平预制裂纹后，充填物厚度为1、3、5 mm的试件的水平预制裂纹汇聚能量的时间分别为433、2 200、2 580 μs，起裂时的应力强度因子分别为635.2、742.4、906.8 kN/m^3/2，表明充填物越厚，水平裂纹越难起裂。水平预制裂纹扩展过程中共发生2次曲裂，是典型的Ⅰ-Ⅱ复合型裂纹，节理充填物越厚，其扩展轨迹越弯曲；当裂纹扩展至距离试件上边界3 mm时，扩展方向偏离第1次裂纹曲裂切线而朝向试件上边界扩展，试件最终断裂，测量发现充填物厚度为1、3、5 mm的试件的断裂点与冲击载荷作用点的距离分别为16.5、11.0、6.0 mm。
- 节理充填物 /
- 动焦散线 /
- 冲击载荷 /
- 应力强度因子
Abstract: To explore the effects of the thickness of joint-filling material on the dynamic fracture properties of cracks under impact load, the gypsum was used as the material filled into the prefabricated cracks in polymethyl methacrylate (PMMA) specimens, three-point bending impact tests were conducted on the PMMA specimens with different joint filling thicknesses by using a novel digital laser dynamic caustics experimental system. The experimental results show that the vertical prefabricated cracks propagate vertically upward toward the free surface under the same impact load, which is a tytical mode-Ⅰ crack, and the thicker the filling, the easier the vertical crack initiation. When the vertical crack propagates to the horizontal prefabricated crack, the energy gathering times of the horizontal prefabricated cracks in the specimens with a filling thickness of 1, 3 and 5 mm are 433, 2 200 and 2 580 μs, respectively. And the stress intensity factors of crack initiation are 635.2, 742.4 and 906.8 kN/m^3/2, respectively. It indicates that the thicker the filling, the more difficult the horizontal crack initiation. The horizontal prefabricated crack is a typical Ⅰ-Ⅱ composite crack. The thicker the joint filler, the more curved the propagation path of the horizontal prefabricated crack. When the distance between the crack and the upper boundary of the specimen is 3 mm, the horizontal crack propagates towards the upper boundary of the specimen, and the specimen finally breaks. It is found that the distances between the fracture points and the impact load points of the specimens with the filling thicknesses of 1, 3 and 5 mm are 16.5, 11.0 and 6.0 mm, respectively.
- joint filler /
- dynamic caustics /
- impact load /
- stress intensity factor

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图 1 焦散线成像原理

Figure 1. The principle of caustics formation

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图 2 落锤冲击加载平台

Figure 2. Drop-weight impact loading platform

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图 3 动态焦散系统光路

Figure 3. Optical light path of experimental system of dynamic caustics

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图 4 试件模型

Figure 4. Specimen model

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图 5 各试件断裂示意图

Figure 5. Fracture patterns of experimental specimens

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图 6 试样S_1-3中裂纹扩展过程动焦散斑图片

Figure 6. Photos of dynamic caustic spots in specimen S_1-3 during crack growth

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图 7 试样S_3-1中裂纹扩展过程动焦散斑图片

Figure 7. Photos of dynamic caustic spots in specimen S_3-1 during crack growth

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图 8 试样S_5-2中裂纹扩展过程动焦散斑图片

Figure 8. Photos of dynamic caustic spots in specimen S_5-2 during crack growth

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图 9 不同试样不同部位动态应力强度因子随时间的变化

Figure 9. Change of dynamic stress intensity factors at different positions of different specimens with time

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表 1 试件断裂破坏各阶段对应的开始时刻

Table 1. Start times corresponding to different stages of fracture failure of specimens

试件 t₁/μs t₂/μs t₃/μs t₄/μs t₅/μs

S_1-3 500 527 960 1 107 1 360
S_3-1 507 541 2 741 2 847 3 067
S_5-2 493 533 3 113 3 166 3 312

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