尺度效应对含缺陷/焊接结构断裂性能和完整性评价的影响

项目名称： 尺度效应对含缺陷/焊接结构断裂性能和完整性评价的影响

项目编号： No.51305295

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 机械、仪表工业

项目作者： 龚宝明

作者单位： 天津大学

项目金额： 25万元

中文摘要： 尺度效应是指材料的力学性能不再是一个常数，随着结构几何尺寸变化而改变，尤其是结构的断裂行为。对于实际较大结构，目前多在实验室条件下通过小尺寸试样试验结果预测。但随着工程结构尺寸和强度级别增加，实验室尺度和实际尺度的差别越来越大，因此，实验室数据对实际结构的指导意义如何成为工程设计和安全性评价中面临的重大难题。因此，尺度效应直接关系到结构的真实强度、承载能力和使用寿命等方面的安全评价.有鉴于此，本课题拟通过对不同尺寸试样的焊接接头断裂试验评价尺度效应的影响，从有限断裂力学和分形能量耗散率的角度，研究起裂韧性和裂纹扩展阻力中尺度效应的根本原因；最后，在评估程序中合理地引入尺度效应，以保证获得精确安全。

中文关键词： 尺度效应；面外拘束度；完整性评估；单边缺口拉伸；管道钢

英文摘要： Size effects are understood as the change in the response of a given structure when the spatial dimensions are scaled up or down while the geometry and other relevant properties of the structure are preserved. For large scale engineering strucutures, the experimental results performed at the laboratory scale usually are used to predict the full scale response of structures, but this practice is very sceptical without taking size effects into account, especially for welded structures with flaws. Therefore, size effects have great influence on the true strength, fracture toughness and structural integrity assessment of welded structures, and can lead to erroneous conservatism and engineering critical assessment. The present work is planning to design some fracture tests with scale variations to capture the scaling phenomena in welded specimen fracture behavior; Finite Fracture Mechanics and the fractal energy dissipation rate theory are first adopted to analyze the crack initiation and propagation in welded joints; considering the coupling between size effects and constraint effect, it is essential to clarify the correlation between fracture properties and their coupling effects; at last, the ultimate aim is to introduce size effects into the structural integrity assessment procedures to ensure the accuracy of the

英文关键词： size effect；out-of-plane constraint；structural integrity assessment；SENT；pipeline steel