冷热循环工艺中冷热转移速率对LY12铝合金尺寸稳定性的影响

研究了冷热转移速率对LY1 2铝合金微屈服强度和残余应力的影响。结果表明 ,提高冷热转移速率易使材料中形成稳定的位错组态 ,从而有利于提高微屈服强度 ;对于圆柱和圆环试样 ,提高冷热转移速率不利于降低残余应力。分析认为 ,冷热转移速率应根据工件几何形状和尺寸进行相应调整。     

考虑材料参数的刚粘塑性有限元初始速度场自动生成方法

本文采用一种包含材料硬化指数ｎ和速率敏感性指数ｍ的刚粘塑性有限元模型，阶段硬化处理考虑到等效应力公与应变率有关，依据线粘性材料假设，提出了考虑材料参数ｎ、ｍ影响的刚粘塑性有限元初始速度场自动生成方法，改进了文献［３］方法。数值模拟结果与有关文献的计算和实验结果进行了比较，表明本文方法是有效的。     

圆柱体平板镦粗应力场的有限元分析

应用刚粘塑性有限元法对圆柱体在两平板间镦粗时的应力场进行了分析 ,给出了毛坯在不同初始高径比时的心部应力随压下量的变化曲线。由此得出 :在变形过程中 ,圆柱体心部存在两向拉应力 ;并且在墩粗过程中 ,当瞬时高径比约为 1 .0时 ,心部σθ、σr 由拉应力转变为压应力。     

Coupling control on pillar stress concentration and surface cracks in shallow multi-seam mining

In order to ensure safe mining and reduce surface damage in shallow multi-seam mining, the failure characteristics of interburden strata with different coal pillars offset distances between pillars in the upper and lower seams, the distribution characteristics of stress concentration in coal pillars, and the development characteristics of stratum cracks and subsidence were investigated by physical and UDEC2 D simulation. Meanwhile, the effect of different coal pillar offset distances on stress concentration of coal pillar and development of stratum cracks were studied. Based on those results, a formula for safe mining and reducing surface damage was established, which provided a theoretical basis for safe and environmentally friendly mining in shallow multi-seam. According to the results, the optimal coal pillar offset distance(the side to side horizontal distance of the upper and lower coal pillars) between the upper and lower coal seams was developed to reduce the stress concentration of coal pillars and surface damage.The results of this study have been applied in Ningtiaota coal mine and have achieved good results in safe and environmentally friendly mining.     

00Crl8Nil0N奥氏体不锈钢200 - 600℃高温疲劳性能的研究

试验用00Cr18Ni10N钢（/%:0.018C,0.41Si,1.68Mn,18.18Cr,10.38Ni,0.16N）经1t EAF-AOD-ESR冶炼,锻成Φ30 mm材和1 050℃固溶处理,进行了00Cr18Ni10N钢200～600℃光滑（K_t=1）、缺口（K_t=3）的轴向高周疲劳性能研究,绘制了疲劳S-N曲线、计算了疲劳极限,并对疲劳试样的典型断口进行了SEM观察。结果表明,光滑试样的疲劳极限随试验温度升高而降低,缺口试样的疲劳极限对试验温度变化不敏感。当应力集中系数由K_t=1提高到K_t=3时,00Cr18Ni10N钢的200、400、600℃下10⁷周次条件疲劳极限分别从530、506、410 MPa,降低到323、370、392 MPa。表明在高温下00Cr18Ni10N钢存在疲劳极限对应力集中敏感,且应力集中敏感性随着试验温度的升高而降低。疲劳试样的断口形貌由疲劳源区、疲劳裂纹扩展区和瞬断区组成,疲劳起源于表面加工刀痕的不连续位置,呈韧性断裂特征。     

轴对称与非轴对称截面冷拔棒材表面残余应力的比较

用物理测定法测定了矩形截面冷技型钢表面的残余应力，并与圆形截面冷拔型钢表面残余应力进行比较。提出用高温近火方法来改善矩形截面冷拔型钢表面残余应力的工艺探索。     

Effect of temperature on the stress corrosion cracking of zircaloy-4 in iodine alcoholic solutions

Zircaloy-4 is susceptible to stress corrosion cracking (SCC) in solutions of iodine dissolved in different alcohols (methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol and 1-octanol). The crack propagation rate is known to decrease as the solvent molecular weight increases, as a consequence of steric hindrance. However, the mechanism that operates during SCC is still unknown. In the present work the effect of temperature on SCC susceptibility was evaluated in 1-butanol and 1-pentanol iodine containing solutions. The dependence of the crack growth rate with temperature follows an Arrhenius law, and the activation energy obtained from experimental data is consistent with a process controlled by volume diffusion of the active species (the iodine-alcohol complex) to the crack tip.     

非晶态Pd—Cu—Si合金的晶化动力学研究

本文应用DSC研究了非晶态Pd-Cu-Si合金的晶化过程动力学.根据Kissinger峰移法和Arrhenius方程分别计算了晶化激活能,发现等温晶化动力学在0.15相似文献   

A model to predict the evolution of pitting corrosion and the pit-to-crack transition incorporating statistically distributed input parameters

A model based on deterministic equations with statistically distributed input parameters has been developed for simulating the evolution of the pit depth distribution at different exposure times and the percentage of pits that transform to stress corrosion cracks. The model has been applied to the specific case of steam turbine disc steel exposed to a range of environments under applied stress. With preliminary fitting at one exposure time, the simulation not only reflects the trends in the experimental measurement but also the model, uniquely, reproduces the statistical variability or “noise” associated with the measurements.     

Ti40阻燃钛合金的高温蠕变行为

计算了Ti40合金在不同应力、不同温度下的稳态蠕变速率、应力指数及在460℃－540℃范围内蠕变激活能Q＝94.0kJ/mol，并以此基础上研究了其蠕变强化机制。实验结果表明：该合金在此温度范围内的蠕变受位错和扩散双重机制控制，晶界移动对蠕变也有一定的贡献。在目前实验条件下，Ti40合金在620℃蠕变性能较差。