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刘强,周轶昊*,孙晨,陈巨兵.基于数字图像相关的裂纹端部全场三维变形实验研究[J].实验力学,2018,33(1):49~58
基于数字图像相关的裂纹端部全场三维变形实验研究
Experimental investigation on full three-dimensional deformation near crack tip based on digital image correlation
投稿时间: 2016-11-30  最后修改时间: 2017-01-05
DOI:10.7520/1001-4888-16-259
中文关键词:  数字图像相关  裂纹端部  全场三维变形  焊接
英文关键词:digital image correlation (DIC)  crack tip  full three-dimensional deformation  welding
基金项目:国家自然科学基金(11502143, 11372182)资助
作者单位
刘强 上海交通大学 工程力学系 上海 200240 
周轶昊* 上海交通大学 工程力学系 上海 200240 
孙晨 上海交通大学 工程力学系 上海 200240 
陈巨兵 上海交通大学 工程力学系 上海 200240 
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中文摘要:
      基于三维数字图像相关技术(3D-DIC),结合裂尖定位、链式匹配、相关系数阈值化算法,测量金属焊接件裂纹端部的全场三维变形,分析焊接对材料断裂力学行为的影响。实验中采用预制疲劳裂纹的紧凑拉伸试件,以Q235钢为母材,通过改变焊缝位置制备四种不同试件:无焊缝母材试件、焊缝位于中央试件、焊缝偏离中央5mm试件、焊缝偏离中央8mm试件。实验结果显示,3D-DIC既能获得裂纹张开导致的面内变形,提取裂纹尖端张开位移,还能测量裂尖材料屈服导致的局部离面凹陷。对比不同焊接件的裂纹端部场发现,裂纹与焊缝的相对位置对试件断裂力学行为有很大影响。当裂纹位于焊缝处,裂尖张开位移与局部凹陷最为显著,热影响区内裂纹端部的变形也明显大于母材,因此都具有比母材更高的断裂韧度。随着载荷增加,裂纹周围的焊缝边界处容易产生应力集中和局部损伤,最终影响材料的破坏行为。上述结果表明,3D-DIC可用来分析非均匀材料的断裂力学行为,有望为实际断裂问题的解决和断裂力学理论的验证与完善提供有效的实验依据。
英文摘要:
      In this paper, based on three-dimensional digital image correlation (3D-DIC), combining crack tip location, chain matching and correlation coefficient thresholding algorithm, the full three-dimensional deformation of metal weldment crack tip was measured to analyze the influence of welding on materials fracture behavior. In experiment, adopting the compact tension specimens with prefabricated fatigue cracks and taking Q235 steel as base material, four kinds of specimen were prepared, which have different welded joint distributions: non weld base metal specimen, weld is located at specimen central part, weld deviates from specimen central part 5mm, weld deviates from specimen central part 8mm, respectively. Experimental results show that 3D-DIC can not only obtain the in-plane deformation induced by crack opening, and extract the crack tip opening displacement, but also can measure the local out of plane depression caused by the yielding of crack tip material. Comparing crack tip field of different weldments, it is revealed that the relative position of crack and weld joint has a great influence on fracture mechanics behavior of specimen. When crack is located at the weld seam, the crack tip opening displacement and local depression are most significant, and crack tip deformation in heat affected zone is significantly higher than that of base metal, so the fracture toughness is higher than that of the base metal. With the increase of load, the stress concentration and local damage will occur at the boundary of the weld seam near the crack, which will ultimately affect the failure behavior of the material. Above results demonstrate that 3D-DIC can be applied to analyze the fracture behavior of heterogeneous material. It may provide effective experimental data for study of practical fracture problems and for validation and refinement of fracture mechanics theory.
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