鼓泡床密相区多组分床料扩散的CPFD模拟

鼓泡床密相区颗粒的混合和扩散对炉内反应速率影响巨大,研究冷态鼓泡床密相区的混合情况,对热态锅炉研究提供参考。采用计算颗粒流体力学(CPFD)方法,对158 mm (长)×158 mm (宽)×400 mm(高)的长方体模型进行模拟。主要研究不同流速下,不同质量分数的压缩木屑、稻壳的颗粒体积分数和横向扩散系数。模拟结果表明,与稻壳相比,压缩木屑颗粒体积分数更大,床层膨胀程度更小;生物质的质量分数越大,密相区颗粒体积分数越大,床层膨胀程度越小,床层整体流化不均匀性越小;扩散系数随流化风速、生物质的质量分数的增加而增大;相同质量分数下,压缩木屑的扩散系数略小于稻壳。     

轻钢框架节点在反复荷载作用下的有限元模拟分析

目的为检验利用柱腹板屈曲后强度的轻钢框架节点板域的抗震性能．方法在试验的基础上，采用有限元分析软件ANSYS建模，通过施加低周反复荷载，分析框架节点的力学性能．结果框架节点的破坏属于局部屈曲破坏，节点板域无显著加强的节点，破坏发生在节点板域上，显著加强的节点破坏发生在梁端．结论研究表明，有限元计算结果与试验结果吻合较好．剪切变形很大，拉伸变形和弯曲变形很小；显著加强的节点，抗剪切变形的能力很好，拉伸变形和弯曲变形不显著．对节点板域进行加厚并布置对角肋是减小节点剪切变形的一种很有效的节点构造形式．由于周围约束板件能提供强力支撑，这样节点板域屈曲以后并不立即失效．     

Finite element simulation of chip formation in peripheral milling mild carbon steel

The metal cutting process is actually a process ofchip formation,in which almost all of the cutting ener-gy is consumed for chip formation.The process of chipformation has attracted great attention for a long time.This is due to the fact that most of the information usedfor evaluation of the cutting process,such as controlimprovement of chip handling,tool wear,dimensionalaccuracy,and surface integrity,are closely related toit.During the milling process,the chip thickness va-ries along the cutt…     

Finite element and experimental analysis of Vickers indentation testing on Al2O3 with diamond-like carbon coating

Numerical simulation and experimental study of the Vickers indentation testing of the Al₂O₃ ceramic coated by diamond-like carbon (DLC) layer were conducted. The numerical analysis was implemented by a two-dimensional finite element (FE) axis symmetry model. FE analysis results gave insight into the fracture mechanism of DLC films coated on brittle ceramic (Al₂O₃) substrates. The maximum principal stress field was used to locate the most expected area for crack formation and propagation during the Vickers indentation testing. The results show that the median crack initiates in the interface under indenter, before ring crack occurs as the indenter presses down. Finally, the plastic deformation appears when the indenter penetrates into the substrate. The thicker DLC coating increases the Vickers hardness and fracture toughness.     

Finite Element Analysis of Thermal Stresses in Ceramic/Metal Gradient Thermal Barrier Coatings

This paper studied the thermal stresses of ceramicl metal gradient thermal barrier coating which combines the conceptions of ceramic thermal barrier coating （TBC） and functionally gradient material （FGM）. Thermal stresses and residual thermal stresses were calculated by an ANSYS finite element analysis software. Negative thermal expansion coefficient method was proposed and element birth and death method was applied to analyze the residual thermal stresses which have non-uniform initial temperature field. The numerical results show a good agreement with the analytical results and the experimental results.     

TC4/ZQSn10-10扩散连接接头残余应力的数值模拟

对TC4/ZQSn10-10异种材料扩散连接接头处的残余应力分布进行了有限元模拟,并结合组织和应力分布讨论了接头的断裂原因。结果表明,TC4/ZQSn10-10接头的最大残余应力出现在金属间化合物Cu3Ti2上,导致裂纹在Cu3Ti2上萌生;最大剪应力也出现在Cu3Ti2上,最大剪应力的存在使裂纹得到扩展,最终导致接头断裂。通过填加中间层Cu可以缓解接头处的应力分布,使接头强度达到192 MPa,相当于铜合金母材强度的80%以上。     

Effects of CeO2 coating on oxidation behavior of T91 steel in water vapor

Oxidation behaviors of blank and CeO2 coated T91 steel were investigated at 600 °C in water vapor for up to 150 h.Gold marker was used to define the mass transport direction.The oxide scales were studied with X-ray diffractometry (XRD),scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA).The oxidation resistance of the steel is improved by CeO2 coating,though the improvement is not remarkable.Ce-rich oxide band is located at the interface of the inner equiaxed layer and the outer colum...