《未来加工工业的材料技术》要点及对我国传统产业改造与新材料研发的启示

概述了美国国家材料咨询委员会报告《未来加工工业的材料技术－管理战略和研究机会》要点，对比了美国“未来工业”与中国“传统产业”，鉴于两者的诸多相似特征，指出了该报告中所提出的“市场推动”和“共性技术”开发策略对于中国传统产业改造的借鉴意义，并探讨了报告中所建议的项目管理战略对于中国新材料研发工作的启示。     

Nb双晶中晶界腐蚀与位向差的关系

用干涉显微镜研究了具有对称倾斜晶界的Nb双晶的晶界腐蚀。除了在靠近重合位置点阵(CSL)晶界处出现极小值外,腐蚀深度d是随位向差θ的增大而增加的。对小角度晶界,d随θ的变化遵循Read—Shockley关系。用计算机模拟方法计算了晶界的原子结构及其局部膨胀,用自由体积的变化解释了晶界腐蚀的结构依赖性。     

连接SiCp/6063Al复合材料的Al-Si-Cu-Ce-Ti箔状钎料制备及其性能研究

采用快凝甩带技术制备了6组不同Ti含量的(Al-10Si-20Cu-0.05Ce)-xTi急冷箔状钎料,并对SiCp/6063Al复合材料进行真空钎焊,然后对钎料及接头的显微组织和性能进行分析。结果表明,急冷箔较常规铸态钎料的组织细小、均匀;固、液相线降低,熔化区间变窄;随着Ti含量的增加,急冷箔中片状Al-Si-Ti金属间化合物相增多,导致钎料脆性增加;6组钎料在复合材料上润湿性较差,但在6063Al合金上润湿性良好。在580℃钎焊温度、保温30min条件下,采用1%Ti含量急冷箔状钎料成功连接了SiCp/6063Al复合材料,钎焊接头组织致密、完整,急冷箔状钎料与6063Al合金基体连接界面可进行充分的冶金结合,且接头剪切强度达到104.9 MPa;钎焊前采用夹具增加接头压力可显著提高接头的连接质量。     

Optimal control of unknown nonaffine nonlinear discrete-time systems based on adaptive dynamic programming

An intelligent-optimal control scheme for unknown nonaffine nonlinear discrete-time systems with discount factor in the cost function is developed in this paper. The iterative adaptive dynamic programming algorithm is introduced to solve the optimal control problem with convergence analysis. Then, the implementation of the iterative algorithm via globalized dual heuristic programming technique is presented by using three neural networks, which will approximate at each iteration the cost function, the control law, and the unknown nonlinear system, respectively. In addition, two simulation examples are provided to verify the effectiveness of the developed optimal control approach.     

一套用于激光多步共振电离截面测量的多定标数据获取系统

本文主要介绍了一套应用于激光多步共振电离截面测量的CAMAC多定标数据获取系统.它可以实现严格同步采集多个实验参数,并能灵活适应实验条件的宽范围变化.CAMAC前端的定标器数目可通过更改数据读出表文件来任意增减;获取方式分为自动重复获取和手动单次获取;获取时间单位可在1ms-800s范围内调节.经过测试得到,本数据获取系统的获取时间单位选择100s时长时间工作的稳定性(△t/t)好于±0.01%,充分证实了该套数据获取系统长时间在线采集实验数据的可靠性.最后利用这套系统同步测量了三台热电偶激光功率探头的功率-响应时间曲线.     

Crystal Plasticity Finite Modelling of 3D Surface Asperity Flattening in Uniaxial Planar Compression

Rate-dependent crystal plasticity constitutive model has been employed into finite element software ABAQUS to simulate surface asperity flattening in uniaxial planar compression. Measured textures and surface roughness are introduced into the 3D surface roughness model. The calculated results show a good agreement with the experimental results. With an increase of reduction, the surface asperity flattening tends to increase, and Goss texture {011} 〈100〉 and brass component {110} 〈112〉 become stronger, whilst the cubic texture {001} 〈100〉 becomes weaker. If the reduction reaches 40%, Schmid in-grain shear band appears and the strain localisation starts. The evolution of surface feature (roughness) shows the obvious sensitivity on the orientation {111} of near-top surface.     

北京大兴国际机场南航基地1号机库大厅弹塑性时程分析

为充分考察北京大兴国际南航基地1号机库大厅结构抗震性能,采用ABAQUS6.11对结构进行弹性时程分析和弹塑性时程分析,分析中采用ABAQUS提供的材料本构模型和用户自定义材料本构模型,计算了小震和大震作用下机库大厅的响应.计算结果表明:小震和大震作用下,机库大厅的柱顶最大位移角均小于规范限值.网架整体保持弹性,局部与柱顶相连部分有轻微屈曲;工字形双肢格构柱保持弹性,多肢格构式钢管混凝土柱的柱底有轻微屈服;格构柱柱间防屈曲支撑有轻微屈服,大门角柱普通支撑屈曲失稳.多肢格构式钢管混凝土柱和大门中柱的混凝土历史最大压应变均小于峰值应变.由于结构X方向长度较长,在计算的过程中,考虑了行波效应对结构的影响.大震作用下,考虑行波效应后,整体结构最大柱顶位移角有所增加,但依然满足规范限值.     

Mechanism of Macrosegregation Formation in Continuous Casting Slab: A Numerical Simulation Study

Metallurgical and Materials Transactions B - Solidified shell bulging is supposed to be the main reason for slab center segregation, while the influence of thermal shrinkage rarely has been...