制动管一体式法兰接头热镦挤成形工艺仿真分析

Numerical Analysis of Hot Upsetting-extruding Process for Integrated Flange Fitting on Brake Pipe

目的 针对铁路货车空气管路制动系统中焊接法兰接头连接质量不佳的问题,提出一种制动管一体式法兰接头热镦挤工艺。方法 分析了制动管用AISI321不锈钢的高温变形行为并构建了本构方程,并通过DEFORM–2D软件对制动管件法兰接头热镦挤工艺进行了数值模拟。结果 应力–应变曲线在低应变速率时呈现稳态流动,但在高应变速率下会出现明显的波动。本构方程得到的应力计算值与试验真实值的相关系数为0.986,平均相对误差为6.7%。在热镦挤工艺成形法兰接头过程中,挤压阶段的最大应力位于制动管扩径的圆锥面处;镦粗阶段的最大应力位于法兰接头平面成形处,并最终转移至法兰接头的圆角处。结论 建立的本构方程能够反映AISI 321不锈钢真实应力–真实应变的关系,可用于描述该材料在热镦挤成形工艺中的塑性变形行为。在该制动管一体式法兰接头热镦挤成形过程的镦粗阶段,摩擦因数保持在0.3以下能够有效降低镦粗力。

The work aims to propose a hot upsetting-extruding process for integrated flange fitting on brake pipe to solve the poor connection quality of welded flange on the brake pipeline system of the freight train. The high temperature deformation behavior of AISI 321 stainless steel for brake pipe was analyzed and the corresponding constitutive equations was established.Then the numerical analysis of the hot upsetting-extruding process for flange fitting on brake pipe was conducted with DEFORM-2D software. Results showed that the stress-strain curve presented steady flow at lower strain rates, but had obvious fluctuation at higher strain rates. The correlation coefficient between the calculated stress and the experimental stress of constitutive equation was 0.986 and the average relative error was 6.7%. During the hot upsetting-extruding process to form the flange fitting, the maximal stress of the extruding process was located at the conical surface of the tube expanding part;while the maximal stress of the upsetting process was placed at the flat surface of the integrated flange fitting and finally transferred to the rounded corners of the flange fitting. The established constitutive equation can reflect the relationship between real stress and real strain of AISI 321 stainless steel, and can be used to describe the plastic deformation behavior of this material during hot upsetting-extrusion. In the upsetting stage of the hot upsetting-extruding of integrated flange fitting on brake pipe, keeping the friction coefficient below 0.3 can effectively reduce the upsetting force.