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Laser Engineered Net Shaping (LENS) modeling using welding simulation concepts.

机译：使用焊接仿真概念的激光工程净成形（LENS）建模。

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摘要

This study focuses on obtaining residual stresses and molten pool details for LENS (Laser Engineered Net Shaping) produced parts by using finite element analysis. Obtaining residual stresses and deformation is very important for the LENS process since this information is used for improving quality and life of the LENS produced parts. In addition, this information can be used in order to understand and relate input parameters to the results such as stresses and deformation. LENS process is basically a laser welding process, therefore welding simulation concepts provides the background for simulating LENS process. Basics and theory for the welding simulation along with two applications are presented. These applications are; (1) Numerical Simulation of Welding Induced Residual Stresses in a Circular Hollow Section T-joint, and (2) Laser welding of a thin aluminum plate. The difficulties associated with simulating the LENS process are summarized and a "wall" configuration consisting of one hundred deposited layers is calculated using finite element analysis. Two different materials are used, one being a single phase material and the other being a four phase material where phase transformations are taken into account. The stress fields for these two materials are found to be quite different. The results for the single phase material are compared with published experimental results and some agreement is observed. For all welding simulations a welding specific finite element package, SYSWELD, is used.;The heat transfer details in the melt pool such as temperature gradient have very little affect on the overall mechanical results. For example, this was demonstrated on a simple bead on a plate problem by calculating the melt pool from four different heat source definitions and comparing the residual stress levels for each melt pool. However, it has been known that temperature gradients are very important if a certain solidification pattern is desired. Repairing single crystal turbine blades by using a LENS machine, requires precise control of the temperature gradient in order to prevent columnar to equiaxed transition (CET) during solidification. Computational fluid dynamics is used in order to model the problem and predict the temperature gradient within the melt pool. The solid-liquid boundary is also calculated. Energy, momentum and continuity equations are solved in order to accurately take fluid flow into account. The Marangoni force is found to be the main driving force. This force is caused by the temperature dependent surface tension on the free surface. Fluid flow calculations were performed by using the FIDAP computational fluid dynamics code.
机译：这项研究着重于通过有限元分析获得LENS（激光工程净成形）生产零件的残余应力和熔池细节。对于LENS工艺而言，获得残余应力和变形非常重要，因为此信息用于提高LENS生产零件的质量和寿命。此外，可以使用此信息来理解输入参数并将其与结果（例如应力和变形）相关联。 LENS过程基本上是激光焊接过程，因此焊接模拟概念为模拟LENS过程提供了背景。介绍了焊接模拟的基础知识和理论以及两个应用。这些应用是： （1）圆形空心截面T型接头中焊接引起的残余应力的数值模拟，以及（2）薄铝板的激光焊接。总结了与模拟LENS过程相关的困难，并使用有限元分析计算了由一百个沉积层组成的“墙”结构。使用两种不同的材料，一种是单相材料，另一种是四相材料，其中考虑了相变。发现这两种材料的应力场完全不同。将单相材料的结果与已发表的实验结果进行了比较，并观察到了一些一致性。对于所有焊接模拟，都使用特定于焊接的有限元软件包SYSWELD 。；熔池中的传热细节（例如温度梯度）对整体机械结果的影响很小。例如，通过根据四种不同的热源定义计算熔池并比较每个熔池的残余应力水平，可以在板上问题的一个简单珠子上证明这一点。但是，已经知道，如果需要某种固化方式，则温度梯度非常重要。使用LENS机器维修单晶涡轮叶片需要精确控制温度梯度，以防止凝固过程中柱状到等轴转变（CET）。使用计算流体动力学来对问题进行建模并预测熔池内的温度梯度。还计算了固液边界。求解能量，动量和连续性方程，以便准确地考虑流体流动。发现马兰戈尼力是主要驱动力。该力是由自由表面上与温度相关的表面张力引起的。通过使用FIDAP计算流体动力学代码进行流体流量计算。

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  • 作者

    Semetay, Cumali.;

  • 作者单位

    Lehigh University.;

  • 授予单位 Lehigh University.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 125 p.
  • 总页数 125
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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