ForceArc双面焊熔池流场与温度场的数值模拟

基于超威弧(ForceArc)焊接时电弧的形态特征,及超短电弧下实现强制熔滴喷射过渡的特点,采用双椭圆分布热源模型及峰值指数熔滴热焓衰减分布模型. 通过分析工件坡口形貌对ForceArc焊接物理过程的影响,建立贴体坐标系下的ForceArc焊接过程三维瞬态数值分析模型. 模拟了不同预热温度及层间温度对焊接过程的影响,分析了工件上下坡口形貌对熔池传热、传质的影响,并与试验结果进行了对比. 结果表明,文中所建模型能够较好地模拟ForceArc焊接过程,对优化其焊接工艺参数具有一定的指导意义.     

Prediction and verification of melting front in GTA weld pool of full-penetration

A thermal conduction model is applied to speed up the numerical analysis of the temperature distribution and the weld pool geometry of full penetration in gas tungsten arc （GTA） welding. With considering both top and bottom flee surface deformation of full-penetrated weld pool, three-dimensional weld pool with melting front and solidification front is predicted. Welding experiments are conducted to measure the melting front curves at the top surface and the longitudinal section of the weld. It shows that the predicted and measured results are in good agreement.     

变频技术在纸厂高压水泵中的应用

随着变频技术的发展及其应用的普及,变频器在纸厂得到了越来越广泛的应用,纸机传动用它,匀浆辊调速用它,复卷分切更是离不开它,而在不直接参与纸机运转的高压水泵上的应用却还不多,其实,变频技术在高压水泵中的应用是很值得一试的改造项目。     

熔焊热过程与熔池行为数值模拟的研究进展

熔焊是目前机械制造业中应用最为广泛的材料连接技术。熔焊过程中的传热与熔池流动行为对于焊缝成形、接头微观组织与服役性能等起着决定性作用。准确地分析和计算熔焊热过程与熔池形态,对于焊接冶金分析、应力变形分析、过程控制及工艺优化等都具有十分重要的意义,也是使焊接工艺从"定性"走向"定量"分析、从"经验"走向"科学"的重要途径。对焊接电弧物理、熔滴过渡、熔池形态、高速焊接熔池传热与流动、等离子弧焊和激光焊接的小孔与熔池动态行为、激光-电弧复合热源焊接热过程的数值模拟研究现状与存在问题进行了评述,讨论了上述前沿领域的研究方向与发展趋势,旨在为实现熔焊工艺优化和过程控制提供理论依据。     

焊接数值模拟的标准化与准则制定

为区分各种焊接模拟方法的适用性以及统一模拟的先决条件和步骤,用户需要相关的标准.由于目前在焊接模拟领域仍缺少相关的标准化文件,因此,德国标准化学会筹建了焊接模拟NA 092-00-29 AA标准委员会,对焊接模拟标准化文件开展准备性的工作.此委员会同时隶属于德国焊接学会“焊接模拟应用”工作组.从长远角度看,标准化工作的...     

复卷分切过程撕纸长度补偿分析与设计

通过对复卷分切撕纸过程的分析,设计了直接补偿法和间接补偿法,实现了撕纸长度的精确补偿,为成品长度的精准控制提供了有力保障。     

无损检验在建筑工程检测中的应用

为确定建筑工程施工效果,需要在施工后采取有效的措施对工程结构进行检测,诊断确定其是否存在质量问题。无损检验现在已经被广泛的应用到建筑工程质量检测中,对提高工程检测安全性与可靠性具有重要意义。对于不同的建筑工程结构,所适应的检测技术也不同,需要结合实际情况来确定相应的检验技术。本文对无损检验进行了概述,并重点分析了其在建筑工程检测中的应用。     

Influence of backward flowing molten jet on humping bead formation during high-speed GMA welding

Considering the inflttence of backward flowing molten jet observed by experiments, a new pool surface deformation formula and droplets heat content model are used to investigate the humping formation mechanism during high-speed gas metal arc (GMA) welding. Three-dimensional geometry of the humping bead is numerically simulated only if some extra force and heat acted at the rear part of weld pool are taken into account in the model. It has proved that both the momentum and heat content of backward flowing molten jet must be appropriately treated to quantitatively analyze the physical mechanism of the humping phenomenon.     

Effect of welding current and speed on occurrence of humping bead in high-speed GMAW

The developed mathematical model of humping formation mechanism in high-speed gas metal arc welding (GMAW) is used to analyze the effects of welding current and welding speed on the occurrence of humping bead. It considers both the momentum and heat content of backward flowing molten jet inside weld pool. Three-dimensional geometry of weld pool, the spacing between two adjacent humps and hump height along humping weld bead are calculated under different levels of welding current and welding speed. It shows that wire feeding rate, power intensity and the moment of backward flowing molten jet are the major factors on humping bead formation.     

纸机传动中的同步联锁

目前，新式纸机传动已普遍采用多点交流变频传动，下面笔者就以ABB公司的ACA600系统为例谈一谈纸机传动中同步联锁的原理、设计、调试。