焊接接头微观组织演化的可视化模拟

本文主要针对焊接接头微观组织演化建模及其可视化方法进行研究。采用元胞自动机模型,通过对焊接接头的微观组织晶粒生长进行模拟来分析和研究微观组织的形态学和动力学特征;通过微观组织图像人工生成技术,直观、精确地展现出微观组织演化的可视化效果。实验结果表明,经过回归分析得到的晶粒生长指数同主流的Burke经验公式相符,使用元胞自动机算法对微观组织演化进行的可视化模拟得到了令人满意的效果。     

A study on HAZ’s microstructure and grain size of 10CrNi3MoV steel

0　Introduction10CrNi3MoVsteelisakindofquenchedandtemperedsteelwith 5 90MPahighyieldstrength .Duetoitsexcellentweldabilityandimpacttoughness,10CrNi3MoVsteeliswide lyusedinmainpartofshipstructure .However,itswellpropertiesareachievedinvirtueofcontrollingweldingparam eterstrictly .Atthesametime ,owingtoitscoldcrackingsusceptibility ,10CrNi3MoVsteelneedspreheatingweld .Meanwhile,structureandpropertiesofsteelwillbechangedundertheconditionofweldingthermalcycle .Forexample,twinedmartensitehasb…     

Micro-mechanical properties of 2219 welded joints with twin wire welding 

0IntroductionWith the rapid developmentof modern manufacturing,applications of aluminum alloy welded structures with bigthickness are becoming more and more widely. As a kindof efficient welding method, twin wire welding has suchmerits as big deposition rate, little heat input and narrowheat-affected zone. At the same time, the defects such asincomplete penetration, discontinuous beam or undercutcan be avoided effectively[1 -5]. 2219 aluminum alloy hasthe wider application foreground due to it…     

New development in welding thin-shell aluminum alloy structures with high strength

From the viewpoint of welding mechanics, two new welding methods-welding with trailing peening and welding with trailing impactive rolling were introduced. For aluminum alloy thin-shell structures with high strength, welding will lead to hot cracking, poor joint and distortion. In order to solve them, trailing impactive device was used behind welding torch to impact the different positions of welded joints, thus realizing the welding with free-hot cracking, low distortion and join tstrengthening. By use of impactive rolling wheels instead of peening heads, the outlook of welded specimen can be improved and stress concentration at weld toes can be reduced. Equipment of this technology is simple and portable. It can used to weld sheets, longitudinal and ring-like beams of tube-like structures, as well as the thin-shell structures with closed welds such as flanges and hatches. So the technology has the wide application foreground in the fields of aviation and aerospace.     

Theoretical study and numerical simulation of the stress fields of the Al2O3 joints brazed with composite filler materials

Non-linear finite element code MSC. Marc was utilized to analysis the field of stress of the Al2O3 joints brazed with composite filler materials. The properties of the filler materials were defined by using the mixing law, method of Mori-Tanaka and theory of Eshelby to ensure the accuracy and reliability of results of finite element method （FEM）. The results show stress in brazed beam is higher than that in base material. The maximal stress can be found in the interface of joint. And the experimental results show that the shear strength of joints increases from 93.75 MPa （ Al2O3p Ovol. % ） to 135.32 MPa （ Al2O3p 15vol. % ） when composition of titanium is 3wt% in the filler metal.     

混流式水轮机转轮简化模型焊接应力场的数值模拟

在确定混流式水轮机转轮简化模型、解决分段焊焊接热源加载问题及解决各独立实体间接触边界节点不重合的热传导问题的基础上，对转轮模型焊接过程的应力场进行了数值模拟。得到了焊接过程中纵向应力的演变规律与焊后应力场的分布情况。结果表明，焊后应力的峰值出现在叶片与上冠或叶片与下环接触面的附近的叶片上。这个结果可以较好地解释水轮机转轮叶片疲劳裂纹的产生和扩展的失效行为。     

考虑金属逐步填充的多道焊温度场数值模拟

采用“单元死活”有限元技术自行编制了控制焊接过程金属填充的子程序,利用Marc有限元软件以低碳钢为例进行了三维多道焊温度场的数值模拟。实现了模拟过程中焊接材料的逐步填充,温度场计算结果与试验测量值十分吻合。将计算结果与未考虑材料逐步填充的多道焊计算结果进行了比较。结果表明,是否考虑金属逐步填充对多道焊计算结果影响很大,在多道焊次数较多时不可忽略。为更准确的多道焊应力分析打下了基础。     

复合钎料的特点及研究现状

为缓解钎焊接头的列余应力，人们提出了在普通钎料中加入一定体积比的作为增强相的各种形态的高温合金、碳纤维及陶瓷颗粒等形成复合钎料方法。该钎料不仅具有较好的填缝能力，同时获得的钎缝接头具有良好的高温强度和抗冲击性能，复合钎料钎焊方法是一种很有潜力的钎焊陶瓷与金属的方法。     

偏析对纳米贝氏体钢再纳米化焊缝组织性能的影响

采用扫描电镜、透射电镜TEM和电子背散射衍射EBSD分析了焊接偏析对纳米贝氏体钢再纳米化焊缝中的残余奥氏体的影响.结果表明,焊接偏析导致了粗大奥氏体的形成,该粗大奥氏体集中分布于枝晶间位置.粗大奥氏体的含碳量低于块状奥氏体,稳定性降低.母材残余奥氏体尺寸为亚微米级且均匀分布,而焊缝残余奥氏体的平均晶粒尺寸为微米级,且分布不均匀.焊接偏析导致的焊缝残余奥氏体的变化对焊缝延伸率有重要影响.力学测试结果表明再纳米化焊缝强度与母材相当,延伸率明显小于母材.     

铝合金非承载十字接头疲劳特性

基于结构应力法,计算拉伸疲劳加载时不同几何尺寸的7N01铝合金非承载十字接头的结构应力,并结合疲劳试验数据建立其疲劳失效的主S-N曲线.结果表明,与名义应力法相比,基于结构应力法的主S-N曲线线性相关性更好,能够适应不同几何尺寸十字接头疲劳的计算.进一步分析相同名义应力下,承载板厚度对疲劳寿命的影响,结果表明,接头疲劳承载能力的增加与板厚的增加并非线性关系,随着承载板厚度增加,接头疲劳寿命降低.