FPSO目前已成为深水作业的重要设备之一。FPSO为大型焊接结构，焊接过程中不可避免的会有残余应力产生。而焊接接头的焊趾附近容易萌生表面裂纹，裂纹的产生会使残余应力发生重分布，从而影响焊接残余应力对结构疲劳强度的评估。本文首先基于热-弹塑性基本理论和X射线衍射法对FPSO典型焊接接头初始残余应力进行数值模拟和试验研究，结果发现焊趾附近初始横向残余拉应力较大；随后在焊趾附近引入表面初始裂纹，分析含表面初始裂纹的FPSO典型焊接接头残余应力重分布。结果表明引入初始表面裂纹后，裂纹尖端出现了较大的残余拉应力，而远离裂纹区域的残余应力大小和分布几乎不受表面初始裂纹出现后的影响。本文的研究可为FPSO安全性能评估提供参考。
FPSO has become one of the important equipment for deep-water operation. FPSO is a large welded structure, and residual stress would inevitably occur in the welding process. However, surface cracks are easy to occur near the weld toe of welded joints, and the residual stress would be redistributed because of the generation and propagation of cracks, which would affect the evaluation of structural fatigue strength by welding residual stress. Firstly, the initial residual stress of typical FPSO welded joints is numerically simulated and experimentally studied based on the basic theory of thermal elastic-plastic and X-ray diffraction. The results show that the initial transverse tensile residual stress near the weld toe is large. Then, the surface initial crack is introduced near the weld toe, and the redistribution of the residual stress of the typical FPSO welded joints with surface initial crack is analyzed. The results show that there is a large residual tensile stress at the crack tip after the introduction of initial surface crack, and the magnitude and distribution of residual stress far away from the crack are almost unchanged with the appearance of initial surface cracks. The research of this paper could provide reference for FPSO safety performance evaluation.
2022,44(10): 37-42 收稿日期：2021-08-02
DOI：10.3404/j.issn.1672-7649.2022.10.008
分类号：0671.8
基金项目：国家自然科学基金资助项目（5217110689）
作者简介：张晓飞(1982-)，男，副教授，研究方向为船体结构与性能
参考文献：
[1] CHANG D J, HA C S, YOUNG C J . Fatigue life assessment of fillet welded joint considering the relaxation and redistribution of residual stress[C]// The 23rd International Conference on Offshore Mechanics and Arctic Engineering. Vancouver, British Columbia, Canada, 2004: 1-5.
[2] ESLAMPANAH A H, AALAMI-ALEAGHA M E, FELI S, et al. 3-D numerical evaluation of residual stress and deformation due welding process using simplified heat source models[J]. Journal of Mechanical Science and Technology, 2015, 29(1): 341–348
[3] BACHMANN M, CARSTENSEN J, BERGMANN L, et al. Numerical simulation of thermally induced residual stresses in friction stir welding of aluminum alloy 2024-T3 at different welding speeds[J]. The International Journal of Advanced Manufacturing Technology, 2017, 91(1–4): 1443–1452
[4] 刘川, 沈嘉斌, 陈东俊, 等. 大厚板内部焊接残余应力分布实验研究[J]. 船舶力学, 2020, 24(4): 484–491
[5] WAN Y, JIANG W C, LI J, et al. Weld residual stresses in a thick plate considering back chipping: Neutron diffraction, contour method and finite element simulation study[J]. Materials Science and Engineering A, 2017, 699: 62–70
[6] 谢元峰. 基于Ansys的焊接温度场和应力的数值模拟研究[D]. 武汉：武汉理工大学, 2006.
[7] 姚蔚. 考虑残余应力变化的FPSO典型焊接接头疲劳裂纹扩展研究[D]. 镇江：江苏科技大学, 2017.
[8] DNV GL AS. Fatigue design of offshore steel structures[R]. Recommended practice DNVGL-RP-C203, 2016.
[9] FPSO JIP-Fatigue Capacity. Fatigue test of typical weld joints, a proposal of S-N diagrams for welded ship structure[R]. Dong-gu: Hull Initial Design Department, Hyundai Heavy Industries Co. , Ltd., 2000.
[10] CSR for Bulk Carriers and Oil Tankers[S]. 2013. IACS.
[11] 程书立. 基于温度和应力场的焊接残余应力数值分析[D]. 南昌：南昌大学, 2007.
[12] LIU C, LUO Y, YANG M, et. al Three-dimensional finite element simulation of welding residual stress in RPV with two J-groove welds[J]. Welding in the World, 2017, 61(1): 151–160
[13] 蒋文进. 残余应力对FPSO典型焊接节点疲劳强度影响研究[D]. 镇江：江苏科技大学, 2013.
[14] 杨秉宪. 微小裂纹的产生与扩展[J]. 北京航空学院学报, 1984(2): 67–75
