| 引用本文: | 韩涛,乔羚.微缺陷对在役焊接接头力学性能的影响[J].材料科学与工艺,2019,27(6):75-83.DOI:10.11951/j.issn.1005-0299.20180230. |
| HAN Tao,QIAO Ling.Effect of micro defects on mechanical properties of in-service welded joints[J].Materials Science and Technology,2019,27(6):75-83.DOI:10.11951/j.issn.1005-0299.20180230. |
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| 摘要: |
| 为了从原子层次揭示裂纹、空位等微缺陷对在役焊接接头力学性能的影响,从而得到焊接接头中最易失效的区域,本文采用焊接模拟软件SYSWELD对在役焊接过程进行模拟,计算熔池周围的温度场和应力场分布,然后利用LAMMPS软件建立含微缺陷的结构模型,以在役焊接过程中熔池下方区域的瞬时温度、应力状态作为计算条件,研究其在服役环境下的力学性能及微缺陷积累、扩展的动态演化机理.结果表明:在役焊接烧穿是一个宏观、微观结合的多层次过程；焊接电弧经过时,烧穿失稳更易发生在熔深最大处后方；熔池下方的各微区中,熔合线附近力学性能较差,在焊接热和应力的作用下最先失效；管壁材料烧穿时经历了微缺陷的形核、积累及扩展,整个失效过程伴随着空位、微裂纹的形成和扩展；空位、裂纹等微缺陷显著降低了结构的强度,在应力集中的作用下沿缺陷处起裂,严重破坏了结构的稳定性,大大加速了失效进程. |
| 关键词: 关键词:在役焊接 有限元模拟 分子动力学模拟 裂纹 空位 |
| DOI：10.11951/j.issn.1005-0299.20180230 |
| 分类号:TG402 |
| 文献标识码:A |
| 基金项目:山东省自然科学基金项目(ZR2018MEE012)；中国石油大学(华东)研究生创新工程资助项目(YCX2018057). |
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| Effect of micro defects on mechanical properties of in-service welded joints |
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HAN Tao, QIAO Ling
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(College of Mechanical and Electronic Engineering, China University of Petroleum (East China), Qingdao 266580, China)
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| Abstract: |
| To investigate the effect of crack and vacancy on the mechanical properties of in-service welded joints and find the most vulnerable region of welded joints at the atomic level, simulation of in-service welding process was performed by SYSWELD, and the temperature and stress fields around molten pool were calculated. Then the LAMMPS was used to establish structural model with micro defects, and the temperature and stress state of the region below molten pool were taken as service condition. Results indicate that burn-through during in-service welding is a multi-level process combining macro and micro levels. A burn-through would be easier to occur behind the maximum depth of the molten pool when the welding arc passed through. The mechanical properties near fusion line were poor and easy to fail under the welding heat and stress. The pipe wall materials experienced nucleation, accumulation, and expansion of micro defects when a burn-through occurred. Formation and expansion of vacancies and microcracks often occurred during the whole failure process. Furthermore, the micro defects such as vacancy and crack qreatly reduced the strength of the structure, and they started to crack along the defect subjected to the stress concentration. These micro defects significantly destroyed the stability of the structure and accelerated the failure process. |
| Key words: in-service welding finite element simulation molecular dynamics simulation crack vacancy |
