Model heat source using actual distribution of laser power density for simulation of laser processing

The model of heat source(MHS) which reflects the thermal interaction between materials and laser during processing determines the accuracy of simulation results. To acquire desirable simulations results, although various modifications of heat sources in the aspect of absorption process of laser by materials have been purposed, the distribution of laser power density(DLPD) in MHS is still modeled theoretically. However, in the actual situations of laser processing, the DLPD is definitely different from the ideal models. So, it is indispensable to build MHS using actual DLPD to improve the accuracy of simulation results. Besides, an automatic modeling method will be benefit to simplify the tedious pre-processing of simulations. This paper presents a modeling method and corresponding algorithm to model heat source using measured DLPD. This algorithm automatically processes original data to get modeling parameters and provides a step MHS combining with absorption models. Simulations and experiments of heat transfer in steel plates irradiated by laser prove the mothed and the step MHS. Moreover, the investigations of laser induced thermal-crack propagation in glass highlight the signification of modeling heat source based on actual DLPD and demonstrate the enormous application of this method in the simulation of laser processing.

General expression of double ellipsoidal heat source model and its error analysis

In order to analyze the maximum power density error with different heat flux distribution parameter values for double ellipsoidal heat source model, a general expression of double ellipsoidal heat source model was derived .front Goldak double ellipsoidal heat source model, and the error of maximum power density was analyzed under this foundation. The calculation error of thermal cycling parameters caused by the maximum power density error was compared quantitatively by numerical simulation. The results show that for guarantee the accuracy of welding numerical simulation, it is better to introduce an error correction coefficient into the Goldak double ellipsoidal heat source model expression. And, heat flux distribution parameter should get higher value for the higher power density welding methods.

焊接热源计算模式的研究进展

总结了计算焊接温度场过程中焊接热源模式的改进过程。首先讨论了传热学中常用的以集中热源为基础的线热源与面热源的解析模型、以及能量在空间以高斯函数形式分布的焊接热源模式 ,以高斯分布函数为基础 ,引出了半球能量密度分布的热源模式、椭球能量密度分布的热源模式、双椭球能量密度分布等焊接热源模式。并对比了不同热源分布函数对计算结果的影响 ,讨论了不同焊接计算过程中对热源函数的选择。结果表明 ,通常的工程运算仍可采用解析模型函数进行简化计算 ,高斯分布函数、半球能量密度分布函数、椭球能量密度分布函数常应用在有限元计算过程中 ,但由于未精确考虑电弧对熔池的冲击作用 ,在熔池附近有一定误差 ,而双椭球能量密度分布的热源模式 ,不仅可以处理一般的电弧冲力小的焊接热源 ,也可以处理具有强烈穿透作用的激光焊和电子束焊过程的焊接热源 ,进一步提高焊接热循环的计算精度。

Q345E钢焊接热影响区相变的计算机模拟

以Kirkaldy和Koistinen-Marburger相变模型为基础,建立焊接热影响区相变模型。以Q345E钢平板对接焊为例,用Goldak双椭球功率密度分布热源模型计算焊接热循环,用ABAQUS有限元分析软件对焊接过程中的热影响区的相变进行数值模拟。以相同焊接规范进行焊接试验,利用Image-pro-plus软件进行组织测定。将试验结果与模拟结果进行比较分析,二者吻合良好,证明本焊热影响区相变模型可以准确分析焊接热影响区相变情况,对优化焊接工艺参数、改善焊接接头性能、提高焊接产品质量具有重要指导作用。