Asymmetry Behaviour between Tension and Compression for Prestrained Materials under Cyclic Loading

The prestrained metals show substantial asymmetry between tension and compression in addition tothe softening under cyclic loading, thus the cyclic creep takes place at a load-control test. The soft-ening reflects the decrease in density of dislocation and total internal stress, and the creep implies theasymmetry in back stress between tension and compression, The mechanical behaviour of the soft-ening is similar for materials with different slip modes, but their features of creep differ significantly.The creep of planar slip Cu-Zn alloy exhibits“explosively”, while that of wavy slip Cu and low car-bon steel occurs continuously and slowly. The explanation of creep behaviour via the internal dislo-cation structure was presented in this paper. According to asymmetw behaviour, it can be concludedthat the internal processes of softehing also strongly depend on the slip mode. In addition, underhigh stress amplitude the opposite asymmetries take place for Cu and Cu-Zn alloy, it indicates thatasymmetric back stresses developed in pretension have been eliminated even though the density andthe configuration of dislocations have not reached equilibrium.     

大麻织物有机硅柔软整理及染色性能研究

针对大麻纤维木质素含量高、表面粗糙、手感硬挺等缺点,采用4种不同类型有机硅3种整理工序对大麻织物进行处理,并采用正交设计法对环氧有机硅整理工艺进行优化分析,给出了大麻织物环氧有机硅最佳整理工艺配方.结果表明,先染色再有机硅整理,大麻织物色牢度好、染色均匀,织物柔软性能提高.有机硅含量对K/S值影响显著,焙烘时间次之,焙烘温度和浸渍时间影响最小.有机硅最佳整理工艺为:有机硅30 g/L,渗透剂JFC2 g/L,常温浸渍5 min,100 ℃预烘3 min,150 ℃焙烘3 min.     

Effect of Pre-loading on Short Fatigue Crack Growth at a Notch

Results indicate that under cyclic tension thegrowth rate of short fatigue crack from notch rootwill be lowered greatly by tensile pre-loading,butonly a little change by compressive pre-loading.The effect of tensile pre-loading will decrease withthe increase of stress ratio.The variation of shortfatigue crack growth rate is related to the residualstress distribution around notch root.     

冰箱室内温度场和流场的仿真及结构优化

具有冷冻冷藏双重功能的家用冰箱既能提高食品的储藏品质又能延长食品的储藏时间，在现代的家庭生活中发挥着重要作用，成为现代家庭必备的家用电器之一。冰箱冷冻冷藏室的布置方式对其室内温度场和流场的分布以及冰箱的能耗有较大的影响。通过对上冷藏室下冷冻室结构冰箱和上冷冻室下冷藏室结构冰箱室内温度场和流场的仿真发现：相对于上冷藏室下冷冻室冰箱而言，上冷冻室下冷藏室结构冰箱冷冻、冷藏室内温度分布均匀合理，既有利于食品的储存，又能降低冰箱的能耗。     

疲劳断裂过程中渗碳层残余奥氏体的转变

研究了20CrNiMo钢微氮渗碳层中残余奥氏体的形态,及其在疲劳断裂过程中的转变和作用。结果表明:渗碳层残余奥氏体有薄膜状和块状两种形态,由于界面取向的影响,疲劳裂纹更易于穿过块状奥氏体,促使其发生应变诱发马氏体相变。在疲劳断裂过程中,裂纹面附近的残余奥氏体大部分转变成马氏体,这种转变是在断裂瞬间发生的,与疲劳力学条件无关。转变所引起的体积膨胀增强了裂纹闭合效应。相变诱发闭合是渗碳表层高碳区疲劳裂纹扩张行为的主要因素之一。     

激光熔化处理对灰铸铁显微组织的影响

本文借助光学显微镜,透射电镜和扫描电镜,分析了HT20-40灰铸铁于激光熔化处理后表面显微组织特征,并探讨其形成原因。     

基于嫁接GA的车间作业调度问题研究

针对现有遗传算法在解决大规模车间作业调度问题时存在进化速度过慢与早熟的矛盾，提出了一种改进的遗传算法一嫁接遗传算法。算法的改进之处有3点：①引入嫁接种群来加快进化速度并提高抗早熟的能力；(多引入交叉概率矩阵来进一步防止出现早熟；(9采用3种不同的交叉算子来扩大搜索范围，提高解的质量。通过经典调度例子测试，该算法在进化速度和求解精度方面同时取得了比较满意的效果，不失为一种解决遗传算法矛盾问题的新途径。     

基于STEP的CAID信息建模

提出了CAID系统与CAD／CAPP／CAM系统相集成的完整集成概念。分析了自主开发的工业设计软件系统中的信息构成。以机床门为例，基于STEP标准，用EXPRESS语言对产品部件建立了工业设计领域信息模型，分析了工业设计领域STEP标准应用协议的发展方向。为建立正式的STEP标准的工业设计领域应用协议奠定了基础。     

MODIFICATION OF SEEMANN-BOHLIN METHOD FOR STRESS MEASUREMENT

The scattered distribution of the lattice parameters in the Seemann-Bohlin method forstress measurement was discussed.A linear relation can be achieved by modification withthe theory deduced from Kroner model.However,the Seemann-Bohlin method cannotachieve good accuracy in comparison with the Bragg-Brentauo method,particularly forlow stress values.     

RESIDUAL STRESS CONCENTRATION AND ITS EFFECTS ON FATIGUE LIMIT AND SHORT CRACK GROWTH

Residual stress concentration at a notch depends on both notch geometry and yield strength ofthe material.It varies through the depth,and its magnitude may be higher than the theoreticalone.Compressive residual.stress concentration at the notch of shot-peened specimen of softmaterial is easily to he relaxed,with the surface damage during shot-peening results in a mi-nor contribution to the fatigue limit.Compressive residual stress increases the crack closureeffect at the notch and may lead to a non-propagating crack.