钢结构焊接连接延性断裂分析

蔡亮亮; 王玺; 方喆立; 吴川; 李来委

doi:10.13206/j.gjgS22101702

钢结构焊接连接延性断裂分析

doi: 10.13206/j.gjgS22101702

中国人民解放军63926部队, 北京 100096

详细信息

作者简介:
蔡亮亮,高级工程师,主要从事钢结构相关研究。Email:411401022@qq.com

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出版历程
- 收稿日期: 2022-10-17
- 网络出版日期: 2024-05-31
- 刊出日期: 2024-03-22

Study on Ductility Fracture of Welding Connections in Steel Structures

Unit 63926, Chinese People's Liberation Army, Beijing 100096, China

摘要

摘要: 焊接连接是钢结构最主要的连接方式之一,焊接过程中焊缝附近热影响区内的钢材材质可能因金相组织变化而硬化,热影响区内也会存在裂纹等焊接缺陷,因此,热影响区是焊接连接受拉断裂的薄弱环节。为研究梁柱节点和钢梁拼接节点中钢梁受拉翼缘焊接连接热影响区的延性断裂,制作了Q355D钢材十字焊接连接和对接焊接连接试验试件,并对其进行单调拉伸试验研究,分别建立了焊接连接试件的理想有限元模型和在应力集中位置引入钝化缺口的缺陷有限元模型并进行非线性有限元分析,采用孔洞扩张模型预测了焊接连接试件的延性断裂,编制了VUMAT子程序,在有限元分析过程中,依据孔洞扩张模型的断裂判据不断删除断裂失效单元,对焊接连接试件的断裂扩展过程进行了数值模拟,建立了不同大小网格的焊接连接试件有限元模型,对焊接连接试件延性断裂进行了网格敏感性分析。试验结果表明:试验试件达到极限承载力后均在焊接热影响区内发生伴随着明显塑性变形的延性断裂破坏,十字焊接连接试件和对接焊接连接试件的断裂位移分别为15.9,18.3 mm,两种焊接连接具有较好的塑性变形能力;基于理想有限元模型预测的焊接连接断裂位置与试验观察一致,但预测得到两种焊接连接试件的断裂位移分别为30.5,29.1 mm,均明显晚于试验结果,说明缺陷对两种焊接连接试件的延性断裂有较大不利影响;基于缺陷有限元模型预测得到两种焊接连接试件的断裂位移分别为14.9,17.2 mm,与试验结果吻合较好,说明引入钝化缺口是考虑焊接缺陷不利影响的一种可行方法;采用VUMAT子程序进行数值模拟得到的焊接连接试件断裂扩展路径与试验结果基本一致,验证了采用孔洞扩张模型进行钢结构焊接连接延性断裂扩展分析的适用性;网格敏感性分析结果表明,两种焊接连接试件断裂位置处的应力、应变梯度较小,采用较大网格尺寸的有限元模型进行其延性断裂数值分析仍能得到比较准确的结果,且能大幅提高计算效率。
- 焊接连接 /
- 延性断裂 /
- 孔洞扩张模型 /
- 缺陷 /
- 断裂扩展
Abstract: Welding is one of the most widely used techniques for connections in steel constructions. Materials in the heat affected zone ( HAZ) may be hardened due to phase transformation during the welding. Welding defects, such as cracks, may also exist in the HAZ. Therefore, the HAZ is often the most vulnerable link of welding connections. To investigate the ductile fracture at the HAZ of welding connections in beam-to-column joints and beam split joints, two specimens were made of Q355D steels, one for cross welding connections and the other for butt welding connections. The specimens were tested under monotonic tension. Perfect finite element ( FE) models and imperfect ones with a blunt notch at the stress concentration location were setup for the test specimens. Ductile fracture of the test specimens was predicted by the void growth model ( VGM) based on nonlinear FE analysis. A VUMAT subroutine was programmed for the simulation of ductile fracture propagation of the specimens by deleting fractured elements based on fracture criteria of the VGM during the FE analysis. FE models with different mesh sizes were established and mesh sensitivity analysis was conducted for ductile fracture simulation by the VGM. The tests showed that both specimens fractured at the HAZ with obvious plastic deformation after the peak load. The fracture displacements of the cross welding and the butt welding test specimens obtained by the tests are 15. 9 and 18. 3 mm respectively, indicating that both the welding connections have superior plasticity. The fracture locations predicted by the VGM based on the perfect FE models agree very well with the test observation of both specimens. However, the predicted fracture displacements of the two specimens are 30. 5 and 29. 1 mm respectively, which are much larger than the test results, indicating that welding defects have considerable adverse effect on ductile fracture of the welding connections. Based on the imperfect FE models with consideration of the defects, the fracture displacements of the two specimens predicted by the VGM are 14. 9 and 17. 2 mm, which agree well with the test results. The agreement indicates that introduction of blunt notches is a feasible approach of considering welding defects in ductile fracture analysis. The fracture paths obtained with the VUMAT subroutine are consistent with the test results, which verified the applicability of the VGM for the simulation of ductile fracture propagation of welding connections. Mesh sensitivity analysis showed that, because both specimens have low stress and strain gradient at the fracture location, ductile fracture simulation based on FE model with relatively coarse meshes can give accurate results at much lower computational cost.
- welding connection /
- ductile fracture /
- void growth model /
- defect /
- ductile fracture propagation

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