基于TIG焊接的AISI 4130车架钢管的有限元分析及疲劳寿命评估研究

Finite Element Analysis and Fatigue Life Assessment of AISI 4130 Frame Steel Tubes Based on TIG Welding

  • 摘要: 本文以中国汽车工程学会巴哈大赛U20防滚环焊接直角对接试样为研究对象,针对AISI 4130车架钢管在TIG焊接工艺下的力学性能及疲劳特性展开系统研究。通过构建基于Goldak双椭球热源模型的焊接热-力耦合有限元模型,结合ANSYS Workbench平台实现了焊接温度场与残余应力场的动态模拟,并基于nCode Design Life软件建立考虑平均应力修正的Morrow修正模型与E-N曲线法的多轴疲劳寿命评估体系。研究创新性地提出采用响应面法优化焊接工艺参数,通过设计三因素三水平正交试验发现:当焊接枪头速度为3mm/s、焊接时长为20s、源功率强度为40W/mm²时,焊缝熔深可达3.2mm且熔宽均匀性系数提升18%,残余应力峰值降低至285MPa,最大变形量仅为0.08mm,较传统参数方案提高成形质量23%。微观组织分析表明优化参数下的焊缝区晶粒尺寸细化至12-15μm,热影响区硬度梯度降低37%。基于多体动力学仿真的载荷谱分析显示,疲劳寿命分布呈现显著的空间梯度特征,距离施力点15mm处的疲劳寿命最低为7.37×107次循环,而30mm外的寿命值达7.311×108次循环,满足SAE J1099标准要求,为高强钢赛车车架的结构优化提供了基于损伤容限设计的工艺窗口选择依据。

     

    Abstract: This study systematically investigates the mechanical properties and fatigue characteristics of AISI 4130 chassis steel tubes under TIG welding processes, focusing on the U20 roll cage welding right-angle butt joint specimens from the China SAE Baja Competition. A thermomechanical coupled finite element model based on the Goldak double ellipsoid heat source was constructed to dynamically simulate the welding temperature field and residual stress field using ANSYS Workbench. A multiaxial fatigue life evaluation system integrating the mean stress-corrected Morrow model and the E-N curve method was established via nCode Design Life. Innovatively adopting response surface methodology to optimize welding parameters, a three-factor three-level orthogonal experiment revealed that optimal weld quality is achieved at a torch speed of 3 mm/s, welding duration of 20 s, and power density of 40 W/mm². Under these conditions, the weld penetration reached 3.2 mm, with an 18% improvement in weld width uniformity, a residual stress peak reduction to 285 MPa, and a maximum deformation of 0.08 mm, representing a 23% enhancement in forming quality compared to conventional parameters. Microstructural analysis indicated refined grain sizes (12–15 μm) in the weld zone and a 37% reduction in hardness gradient within the heat-affected zone. Multibody dynamics-based load spectrum analysis demonstrated spatially graded fatigue life distributions: the minimum life of 7.37×10^7 cycles occurred at 15 mm from the loading point, while regions beyond 30 mm exhibited a maximum life of 7.311×10^8 cycles, compliant with SAE J1099 standards. Experimental validation confirmed a prediction error of less than 9.2% for the finite element model. The study establishes a quantitative mapping relationship among welding parameters, microstructural properties, and fatigue life, providing a damage tolerance design-based framework for selecting process windows in high-strength steel racing chassis optimization.

     

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