Abaqus焊接模拟的例子

Low Stress Welding Simulations

Welding is a fundamental manufacturing technique used to join metal components. While a variety of welding processes exist, most involve the application of heat to induce coalescence of the metal in the adjoining parts.

The gas welding technique uses the heat from a gas flame to melt together the contacting edges of the parts being joined. A filler material may or may not be used.

The introduction of very high temperatures in the region of the welded joint causes steep temperature gradients in the structure. As a weld cools, residual stresses may be produced in the weld zone; such stresses may cause the structure to distort. The ability to predict the residual stress state allows for the prediction of final part shapes and a more complete understanding of how residual stresses can affect the load capacity of a structure.

低应力焊接模拟

焊接是一个基本的制造技术，用来连接金属部件。虽然各种焊接过程存在，大多数涉及应用热诱导聚合的金属连接部分。

气体焊接技术使用的热气体火焰熔化在一起的边缘接触部分被加入。填充材料可能会或可能不会被使用。

引进的温度很高，在该地区的焊接接头的原因，陡峭的温度梯度的结构。作为一个焊接冷却，残余应力的产生可能是在焊缝区；这种压力可能导致结构扭曲。预测能力的残余应力状态，可以预测最终零件的形状和一个较完整的理解如何残余应力会影响的承载结构

The finite element models described in this article represent structural beams. These structures are formed by welding plate sections together rather than producing the section directly in a mill. The cross-sectional size of these components can make direct manufacture impractical.

The techniques discussed here are based on a generic model but are transferable to a range of applications.

Finite Element Analysis Approach

The simulation uses a sequentially coupled approach in which a thermal analysis is followed by a stress analysis. The temperature results from the thermal analysis are read into the stress analysis as loading to calculate the thermal stress effects. The thermal analysis makes use of ABAQUS user subroutines DFLUX, GAPCON, and FILM. The objective of the simulation is to predict post-weld deformation and residual stress distribution.

有限元模型，本文中所描述的结构梁。这些结构是由焊接板部分连接在一起，而不是生产的部分直接在轧机。截面大小这些组件可以直接制造不切实际。

这里讨论的技术是基于一个通用的模型，但可以转让给应用范围。

有限元分析方法

仿真使用顺序耦合方法，热分析，其次是应力分析。温度的热分析结果读取到应力分析荷载计算热应力影响。热分析采用ABA QUS用户子程序dflux，gapcon，和电影。在模拟的目的是预测焊接变形和残余应力分布

Figure 1: Mesh of the structure being welded.

The model is constructed using solid and shell elements. A solid representation is used in the weld area to ensure more accurate capture of the high solution gradients. Regions outside the weld zone, where thermal gradients are not as severe, are modeled with shell elements to reduce the overall model size. The transition between the shell and solid regions is achieved using tied contact for the thermal analysis and shell-to-solid coupling for the stress analysis. The mesh is shown in Figure 1 (left). The weld bead is shown in red.

Thermal Analysis Procedure

The thermal analysis is performed to calculate the heat transfer resulting from the thermal load of the moving torch. Three user subroutines are activated for the thermal analysis:

DFLUX: Used to define the welding torch heat input as a concentrated flux. The heat source travels along the weld line to simulate the torch movement.

GAPCON: Used to activate the conduction of heat between the deposited weld material and the parent materials once the torch has passed a given location.

FILM: Similar to GAPCON in functionality, but used to activate film coefficients to simulate convective ambient cooling once the torch passes a given location.

The simulation is run as a fully transient heat transfer analysis.

Structural Analysis Procedure

The structural analysis uses the thermal analysis (temperature) results as the loading. The objective of the structural analysis is to determine the stresses and strains induced in the weld region during the cooling transient. Boundary conditions are applied to restrain the system against rigid body motion.

Figure 2: Nodal temperatures in a typical region of the weld as the torch traverses the weld

line.

Results and Conclusion

Typical thermal results are shown in Figure 2 (left), which displays a contour of nodal temperature as the torch travels along the weld line.

The weld is initialized at 1800° C, but no heat is allowed to transfer from the weld until the torch passes. As the torch passes a given point on the weld line, the flux input is initiated, resulting in a localized increase in temperature to more than 2000° C.

Figure 3: Transient temperature profile at three points in the torch path.

In addition, as the torch passes the same weld line point, conductive and convective heat transfer is activated, causing a rapid drop in temperature as thermal energy is transferred to the surrounding structure and environment.

Figure 3 (right) shows the 35 s transient temperature profile at three points close to the start of the torch path. The peak temperature is reached when the torch is activated. A sharp temperature drop is observed after the torch passes.

Figure 4: Von Mises stress in the weld region at t=35 s.

The stress response of the structure is driven by the high thermal gradients. Figure 4 (left) and Figure 5 (below), respectively, show plots of the von Mises stress and the effective plastic strain approximately 35 s into the process.

Figure 5: Effective plastic strain in the weld region at t=35 s.

In conclusion, ABAQUS/Standard provides a set of general, flexible modeling tools that allow for the prediction of residual stresses and final shapes in welded components.

图1：网格结构焊接。

该模型采用实体单元与板壳单元。一个坚实的代表是用来在焊接领域，确保更准确的捕捉高溶液梯度。焊缝区以外的地区，那里的温度梯度不严重，是模仿与壳元素降低整体模型尺寸。过渡之间的外壳和固体区域是通过使用绑联系的热分析和shell-to-solid耦合应力分析。网格是图1所示（左）。焊缝是红色显示。

热分析程序

热分析是进行计算传热引起的热负荷的火炬。三用户子程序被激活的热分析：dflux：用来确定焊接热输入作为集中通量。热源沿焊缝模拟焊枪的运动。gapcon：用来激活传导热沉积之间的焊接材料和母材一旦火炬传递了一个给定的位置。

电影：gapcon功能类似，但是用来激活膜系数模拟对流空气冷却一次火炬传递给定位置。

仿真运行作为一个完全瞬态传热分析。

结构分析程序

结构分析采用热分析（温度）的结果作为加载。客观的结构分析是确定应力和应变诱导的焊接区域的冷却过程中瞬态。边界条件适用于抑制系统对刚体运动。

图2：结温度在一个典型的焊缝区域作为火炬穿越焊缝线。

结果与结论

典型的热结果显示在图2（左），其中显示一个轮廓节点温度作为火炬沿焊缝。

焊接是在初始化的1800°，但不允许转让从焊接到火炬传递。作为火炬传递一个给定的点焊接线，通量输入启动，导致局部温度上升超过2000°C

图3：瞬态温度分布在三点的火炬路。

此外，作为火炬传递相同的焊接线点，传导和对流传热被激活，造成气温急剧下降的热能量转移到周围的结构和环境。

图3（右）显示，35的瞬态温度分布在三点附近开始的火炬路。达到峰值温度时，火炬被激活。气温急剧下降的观察后，火炬传递。

图4：冯米塞斯应力焊缝区=35秒。

应力响应的结构是由高温度梯度。图4（左）和图5（下），分别为，表明地块的冯米塞斯应力和有效塑性应变约35秒的过程。

图5：有效塑性应变焊缝区=35秒。

总之，ABA QUS /标准提供了一套通用的，灵活的建模工具，可用于预测残余应力和最终形状的焊接组件。