腐蚀疲劳裂纹内溶液的两维运动模型

以单边穿透裂纹为背景,建立了描述腐蚀疲劳裂纹内溶液的流体运动两维方程。通过解偏微分方程组,用解析法得到了腐蚀疲劳裂纹内溶液的两维运动规律。据此,以紧凑拉伸试样为例,讨论了影响速度的各参数及裂纹内的流态。     

耐候钢连铸工艺的改进

分析耐候钢连铸出现的问题,认为凝固时应力过大和磷铜元素偏析造成晶界脆化是出现铸坯纵裂的主要原因;结晶器中喂稀土丝恶化保护渣性能,影响结晶器与坯壳间的润滑与传热,并使热流不均匀是连铸漏钢的主因。采用钙处理代喂稀土丝工艺,以及减缓连铸一、二次冷却强度,改进保护渣后,连铸缺陷获得极大改善。     

FeCrCoWCBY2O3合金激光熔覆层的性能研究

通过对FeCrCoWCBY2O3合金粉末在低碳钢表面进行激光熔覆，获得了C、B含量较高的无裂纹熔覆层，其厚度在1．0～1．5mm之间。利用XRD、SEM等分析了熔覆层的成分及显微组织结构，并测试了涂层的硬度和耐磨性。结果显示：激光处理后表面迅速熔化和冷却，组织由马氏体、残余奥氏体枝晶和枝晶间碳化物组成；熔覆层的硬度比熔覆基体提高3倍多，且硬度最高值不在表层，而在距离表面0．3mm处；耐磨性相对基体提高接近2倍。     

汽轮机叶片金属磁记忆诊断技术

介绍电站汽轮机叶片的金属磁记忆检测原理及应用，用磁记忆诊断技术可快速、准确检测出汽轮机叶片的裂纹和应力集中区。     

连铸管坯裂纹在加热穿孔过程中的变化

研究了连铸管坯表面不同深度裂纹在加热穿孔过程中的变化。结果表明，在连铸管坯内部质量良好时，剥皮能显著改善穿孔毛管表面质量；加热穿孔可以消除或减少管坯表面的微裂纹；管坯表面较深的裂纹穿孔后将在毛管表面以外折的形式出现。     

铸钢车轮材料在600℃-200℃循环温度幅下热疲劳断裂行为探讨

研究了铸钢车轮材料在循环温度幅600-20℃下的热疲劳断裂行为。研究发现，试样表面氧化较为严重，表面开裂加速了次表层裂纹的形核扩展。断口裂纹以沿晶为主，并有少量穿晶裂纹，表明高温蠕变对热疲劳试验过程有着相当的作用。同时，断口的破坏和表面的破坏起到了相互促进的作用。     

基于冲击回波法的混凝土板块开口裂纹的研究

用冲击回波法对混凝土板块不同深度开口裂纹进行了测量，并对获取数据进行后处理和分析，得出了有关混凝土板块开口裂纹用冲击回波法测量的一些结论。     

电脉冲孕育处理对Al-5Cu合金热裂的影响

研究了不同电脉冲孕育处理参数对Al-5Cu合金热裂倾向的影响.结果表明,不同电脉冲孕育处理参数均可降低Al-5Cu合金的热裂倾向,处理后该合金热裂临界应力比未处理试样提高了约3倍.合金热裂倾向改善的原因是,电脉冲孕育处理细化了Al-5Cu合金组织,减少了共晶相的数量,缩短了合金凝固温度区间.     

Crack initiation in relation to the tool edge radius and cutting conditions in nanoscale cutting of silicon

In cutting of brittle materials, experimentally it was observed that there is a ductile–brittle transition when the undeformed chip thickness is increased from smaller to larger than the tool cutting edge radius of the zero rake angle. However, how the crack is initiated in the ductile–brittle mode transition as the undeformed chip thickness is increased from smaller to larger than the tool cutting edge radius has not been fully understood. In this study, the crack initiation in the ductile–brittle mode transition as the undeformed chip thickness is increased from smaller to larger than the tool cutting edge radius has been simulated using the Molecular Dynamics (MD) method on nanoscale cutting of monocrystalline silicon with a non-zero edge radius tool, from which, for the first time, a peak deformation zone in the chip formation zone has been found in the transition from ductile mode to brittle mode cutting. The results show that as the undeformed chip thickness is larger than the cutting edge radius, in the chip formation zone there is a peak deformation depth in association with the connecting point of tool edge arc and the rake face, and there is a crack initiation zone in the undeformed workpiece next to the peak deformation zone, in which the material is tensile stressed and the tensile stress is perpendicular to the direction from the connecting point to the peak. As the undeformed chip thickness is smaller than the cutting edge radius, there is no deformation peak in the chip formation zone, and thus there is no crack initiation zone formed in the undeformed workpiece. This finding explains well the ductile–brittle transition as the undeformed chip thickness increases from smaller to larger than the tool cutting edge radius.