表征小尺寸构件断裂性能的楔入法研究

WWith widely application of thin plate, thin-walled tube, and the components by made of precious metal in the fields of aeronautics and astronautics, nuclear reactor, and chemical industry, the demand of fracture properties determination for small components in size of a few millimeters has become increasingly prominent. However, due to the limitation of traditional compact tension and three-point bending tests, they can not be directly used for the fracture properties determination of this type of small components. Further, no other effective method can be used at present. This project will carry out a research on the wedge method to represent fracture properties for small components. By designing new specimen configuration in conjunction with wedge loading, the size of specimen may achieve the purpose of miniaturization. The theoretical expressions of the corresponding fracture parameters will be established. The test systems of compliance method and load separation method to determine the instant crack size of small components under wedge loading will be developed, then the representation of fracture properties for the small components in milli-scale is implemented. To certify the validity of the new wedge method, comparative tests on the traditional compact tension and three-point bending will be conducted by use of several typical engineering materials. The research results have important significance in the fracture properties and life assessment of components applied in the nuclear reactor, airplane, and chemical equipment. It is favorable to promote the application of experimental mechanics in the structural integrity assessment.

随着薄板、薄壁管件以及贵重金属零部件在航空航天、核反应堆、化工等工程领域的广泛应用，使得特征尺寸在几毫米的小尺寸构件的断裂性能测试需求日益凸显。然而，传统的紧凑拉伸和三点弯曲试验因其各自的局限而无法直接用于该类含裂纹小尺寸构件的断裂性能测试，目前也无其他的有效技术方案。本申请项目拟开展"表征小尺寸构件断裂性能的楔入法研究"，通过新的试样构形设计并配合楔入式加载达到试样小型化的目的，建立对应于新设计试样构形和楔入式加载的断裂性能表征参量的理论表达式，发展用于构件楔入式断裂加载中的实时裂纹长度预测的柔度法和载荷分离法测试体系，进而实现对毫米级小尺寸构件断裂性能的表征。为验证楔入法的有效性，选用若干典型工程材料开展同传统紧凑拉伸法和三点弯曲法的比对实验。研究成果对于核反应堆、飞机以及化工设备结构部件的断裂性能评定及其寿命评估具有重要意义，有利于推动实验力学在结构完整性评定中应用。

本项目受资助以来共发表论文17篇（已发表论文16篇，录用论文1篇），其中SCI收录论文为6篇，EI收录和EI源刊物录用论文为7篇，申请国家发明专利和实用新型专利各2项，其中授权国家发明专利1项，授权实用新型专利2项。主要工作包括：.（1）开发了用于小型构件和贵重金属断裂性能测试的小尺寸CIET和COEP试样，以及相应的加载系统。.（2）基于有限元分析和柔度测试理论建立了CIET、COEP两类试样的裂纹长度、应力强度因子的计算公式。基于弹塑性有限元分析，提出了CIET试样J积分的理论表达式和塑性因子表达式。.（3）基于载荷分离理论，建立了适用于CIET试样的延性断裂韧性测试的单试样规则化法，并实现了多种工程材料的J阻力曲线测定。.（4）基于K-T 、J-Q-M和J-A2-M约束断裂理论，对CIET试样的的裂尖约束效应进行了细致的分析。基于引入T应力的闭合效应修正，实现了CIET试样同传统CT试样疲劳裂纹扩展曲线的统一。基于J-Q-M和J-A2-M理论，实现了CIET试样J阻力曲线的约束修正。.（5）根据塑性应变能耗散原理，建立了考虑试样构形和加载比影响的疲劳裂纹扩展行为理论预测模型，并基于低周疲劳性能成功实现了CT试样和CIET试样不同加载比下的疲劳裂纹扩展曲线预测。.（6）采用COEP试样完成了几类典型工程材料的疲劳裂纹扩展行为试验，获得了相应的疲劳裂纹扩展规律。