注射成型中浇口形式对塑件质量的影响

用生产实例介绍了不同浇口形式及位置对塑料熔体在型腔中的填充模式和注射成型后塑件的内在机械物理性能及表观质量的影响。     

Finite element analysis of tailored sheet forming processes considering laser welding zone

The finite element formulation for predicting strain distributions and weld line movements in the forming processes of tailored sheet metals is developed. The material properties of the welding zone such as strength coefficient, work-hardening exponent, and plastic anisotropic parameter are analytically obtained from those of base metals based on the tensile tests. The welding zone is modelled with the several, narrow finite elements called by weld elements. To verify the finite element formulation for tailored blanks, the forming processes of autobody door inner panel section and hemispherical dome are simulated. FEM predictions are compared and showed good agreements with experimental measurements.     

压力管道未焊透缺陷安全评定分析

依据GB 50236-98<现场设备、工业管道焊接工程施工及验收规范>对某压力管道未焊透缺陷进行评定,该缺陷不能满足最低等级Ⅳ级的要求,应与判废.而依据<在用压力管道定期检验规程(试行)>进行评定,该缺陷能满足安全等级3级的要求.通过利用GB/T 19624-2004<在用含缺陷压力容器安全评定>中给出的压力管道直管段体积缺陷安全评定方法对该缺陷进行安全评定,结果证明,依据<在用压力管道定期检验规程(试行)>进行评定的结果确能够满足使用条件下的安全要求.本文对特种设备检验工作者进行压力管道未焊透缺陷安全评定具有一定的指导意义.     

内伸入式接管焊接接头应力的有限元分析

本文应用Ansys有限元应力分析软件,根据钢制化工容器结构设计规定(HG20583-1998),分别建立内部施焊和外部施焊的内伸入式接管与壳体间焊接接头的模型,分析焊接接头处应力分布的情况,并对焊接接头处的应力进行对比。对比结果表明:a类焊接接头所受应力最大;c类焊接接头应力相对较小;b类焊接接头受力效果最好。若可以对焊缝的坡口连接拐点附近进行优化,可以大大的减小应力水平,改善焊缝的受力情况。     

埋弧焊焊缝组织与扩散氢的关系

综述了埋弧焊焊缝组织与扩散氢的关系。结果表明,硅酸盐粘合剂中的水分是EM12K焊剂扩散氢的主要来源。镀铜层和表面润滑剂是ER100-S1焊丝中两个主要的氢源。埋弧焊电弧中会发生两个与焊剂中氟化物有关的冶金反应。建立了焊缝组织与扩散氢的关系,其要点是氢在焊缝中的扩散方向和聚集部位,并影响氢致裂纹的发生。所谓低氢化工艺是一种使焊缝中残留的氢很少,不足以引发氢致裂纹的综合工艺措施。提出了低氢工艺合于使用原则。     

Improving the reliability of metallic structures in service in the conditions with low climatic temperatures by efficient application of advanced methods of modification of the zone of the welded joint

The concept of investigations carried out to increase the reliability of metallic structures designed for operation in the conditions of low climatic temperatures is described. The worldwide tendencies in the investigation of the processes of the formation and fracture of materials and components at low climatic temperatures are analysed. The main methodological approaches, directed at ensuring high parameters of the service reliability of structures in low carbon, low alloy steels are outlined. The experimental data obtained in this area are analysed. The directions for further experimental and theoretical studies are indicated.     

Effects of evolution of nanoscale copper precipitation and copper content on mechanical properties of high-strength steel weld metal

Nanoscale copper precipitation in high-strength weld metal was characterised by using atom probe tomography (APT) and transmission electron microscopy. In as-deposited zone, there was no copper precipitation. During welding thermal cycling, nanoscale copper of 2–3?nm in radius precipitated with face-centred cubic (FCC) and body-centred cubic (BCC) structure. During post-weld heat treatment (PWHT), FCC copper precipitate became coarsen and BCC transformed into FCC. The highest hardness was in the reheated zone which subjected to the peak temperature below 500°C; while the lowest hardness was both in deposited zone and the reheated zone which subjected to the peak temperature greater than 810°C. After PWHT, the hardness became homogenous as well as decreased. With increasing copper content, the hardness was increased and the toughness was slightly decreased. After PWHT, the toughness decreased due to the change in the structure of copper precipitates.     

SA738Gr.B钢焊缝裂纹产生原因分析及处理

钢制安全壳是核电站的第三道安全屏障,其作用是在事故工况下,阻止放射性物质向环境逸散。焊接是钢制安全壳制作安装阶段的重要加工工艺方法,焊接裂纹缺陷的存在将影响钢制安全壳的质量,对核电站的安全运行造成极大的安全隐患。针对国内某核电工程钢制安全壳闸门插入板与筒体之间的焊缝产生了裂纹的实际情况,重点围绕焊接过程质量控制,详细分析了焊接热裂纹、冷裂纹、层状撕裂、应力腐蚀裂纹以及再热裂纹产生的原因,通过分析确认SA738钢Gr.B钢焊缝裂纹为再热裂纹,并结合工程实际提出了预防措施和裂纹缺陷处理方法,为后续工程焊接工艺制定提供了参考。     

架桥机大臂钢板开裂分析

架桥机大臂钢板在使用过程中发现表面呈方形开裂,但远未达到设计使用寿命。钢板材料为低合金结构钢Q345,其综合力学性能良好。为了弄清钢板开裂原因,通过宏观观察、扫描电镜及能谱仪分析、光学显微分析等对开裂钢板进行了深入探讨,结果表明:钢板失效属于疲劳断裂,疲劳起源于焊缝夹渣,并沿着方形焊缝路径扩展。焊缝中亦存在马氏体组织,马氏体组织较脆,裂纹遇到这种组织也较容易扩展。因此,在循环使用应力作用下,起源于焊渣的疲劳裂纹沿焊缝不断扩展,最终导致钢板呈方形断裂失效。可通过改善焊接工艺、增加焊接线能量以及焊前预热处理等途径来防止裂纹产生。     

基于激光传感器的弧焊机器人焊缝跟踪研究

采用激光扫描式传感器,设计了一套机器人焊缝自动跟踪系统。开发了相应的焊缝跟踪算法,包括直线、圆弧和直线圆弧组合连续焊缝的跟踪算法。探讨实现这些算法的相关技术问题。计算机仿真结果表明,该算法合理有效,可用于弧焊机器人焊缝在线跟踪作业,改善和提高机器人的焊接精度和质量。