INFLUENCE OF RESIDUAL STRESS AND SURFACE MORPHOLOGY ON FATIGUE PROPERTIES OF STEEL 60Mn

Influence of residual stress and surface morphology induced by shot-peening on fatigue behav-ior of a medium temperature tempered spring steel 60 Mn has been studied.The compressiveresidual stress induced in the near-surface region may improve fatigue limit from 930 to 1010MPa,and the very high tensile residual stress in the interior may reduce it from 1010 to 940MPa,whereas the severe surface damage may cause a drop-off of it from 1010 down to 800MPa.Fatigue cracks initiated in such position where the equivalent Mises stress,includingresidual stress,exceeded the local strength of the material.The compressive residual stress,induced by shot-peening,may intensify the effect of crack closure,so as to decrease the crackgrowth rate.     

Electrochemical hydrogen storage performance of as-cast and as-spun RE-Mg-Ni-Co-Al-based alloys applied to Ni/MH battery

The La-Mg-Ni-Co-Al-based AB₂-type La_0.8–xCe_0.2Y_xMgNi_3.4Co_0.4Al_0.1 (x=0, 0.05, 0.1, 0.15, 0.2) alloys were prepared via melt spinning. The analyses of the X-ray diffraction (XRD) and scanning electron microscopy (SEM) proved that the experimental alloys contain the main phase LaMgNi₄ and the second phase LaNi₅. Increasing Y content and spinning rate lead to grain refinement and obvious change of the phase abundance without changing phase composition. Y substitution for La and melt spinning make the life-span of the alloys improved remarkably, which is attributed to the improvement of anti-oxidation, anti-pulverization and anti-corrosion abilities. In addition, the discharge capacity visibly decreases with increasing the Y content, while it firstly increases and then decreases with increasing spinning rate. The electrochemical kinetics increases to the optimum performance and then reduces with increasing spinning rate. Moreover, all the alloys achieve to the highest discharge capacities just at the initial cycle without activation.     

热处理对超声喷丸TC4疲劳性能的影响

对TC4进行超声喷丸（USSP）处理得到表面梯度结构,并于350 ℃分别进行60、120、180和240 min热处理。采用光学显微镜（OM）表征其微观组织,X射线衍射仪（XRD）测得残余应力场分布;通过扫描电镜（SEM）、透射电镜（TEM）分别对其疲劳断口形貌、裂纹源组织进行表征。结果表明,超声喷丸处理引入的残余应力场,随热处理时间的延长,残余应力特征参数值（σ_srs、σ_mrs、Z_m和Z₀）逐渐降低。原始试样疲劳裂纹从表层萌生,超声喷丸试样疲劳裂纹以单一裂纹源形式从次表层萌生,超声喷丸+热处理试样以多源裂纹形式从次表层萌生。     

爆炸焊接最小作用量原理分析

最小作用量原理是自然界的一条基本法则,也是物理学的最后规律.通过爆炸焊接的理论分析、界面测试和生产实践发现,爆炸焊接过程也遵循物理学"最小作用量原理",即以最小的装药量获得最佳的焊接界面.在复板和基板发生非弹性碰撞直至结合这一力学过程中,其"作用量"可认为是"复板和基板的结合能量".为了使界面结合能量为最小,在选取爆炸焊接工艺参数时,需遵循"装药厚度下限法则"和"基复板间隙上限法则"等原则,并优选"最低临界爆炸速度炸药",即可实现爆炸焊接过程"最小作用量原理",从而使爆炸焊接界面状态达到最佳.     

Design and use of a novel sample design for formability testing in pure shear

Existing tests for assessing the formability of sheet metal samples can create strain ratios in the range from uniaxial to biaxial stretching, −1/2 ≤ ?₂/?₁ ≤ 1. A novel sample design is proposed, with shaped cut-outs in a rectangular sheet specimen, intended to produce with strain ratios in the range, −1 ≤ ?₂/?₁ ≤ 1/2 in a small zone, while the sample is uniaxially extended. The strain ratio is controlled by changing the geometry of the cut-outs.     

Effect of WC/C PVD coating on fatigue behaviour of case carburized SAE8620 steel

Case carburizing steels, such as SAE8620, are generally employed in manufacture of automotive components viz. gears and shafts. These components are often subjected to a combination of wear and fatigue loads. Though a number of coatings are available that can enhance performance under such loadings, but high processing temperatures forbid their application to heat-treated components. On the other hand, the low processing temperature for the WC/C coating permits its application to heat-treated parts. The coating exhibits favourable tribological properties, but its influence on fatigue behaviour is yet unexplored. The present work is aimed at investigating the influence of WC/C coating on the fatigue behaviour of case carburized SAE8620 steel, wherein performance of uncoated and coated specimens is compared by subjecting them to four point rotating bending fatigue tests. The results point out that the coating leads to 7% gain in endurance limit without considerably affecting the hardness and tensile strength.     

动力电池组汇流排过载能力及电流均衡性影响因素研究

以某电动汽车动力电池组软包电池单体汇流连接排为研究对象,对不同结构、不同厚度的汇流排进行热电耦合数值计算,探讨了汇流排结构形状、汇流排电流I/O方式、汇流排焊缝宽度、焊缝位置对汇流排温升和电池单体均衡性的影响。以标准汇流排为研究对象,在两进两出电流不同分配方式下,重点分析汇流排对电流均衡性的影响。加工了铝质汇流排,采用多路温度测试仪对铝质汇流排进行实验测试,在不同电流作用下,实验温升和数值模拟温升之间的误差在5%之内。研究结果表明,钣金折弯对汇流排的过载能力影响不大,在汇流排表面开孔会显著降低汇流排的过载能力;在一定范围内增大汇流排厚度可以显著提升汇流排的过载能力;汇流排的焊缝宽度和焊缝位置对过载能力有一定影响,其中焊缝位置影响更大一些。最后对汇流排温升过高以及电流分配不均衡的机理进行了详细分析。     

高比强度多孔铝合金的压缩性能和能量吸收特性

：采用渗流法制备了具有通孔结构的ZL111基多孔铝合金，研究了固溶时效热处理和孔结构参数对多孔铝合金压缩性能和能量吸收特性的影响。结果表明：固溶时效热处理可以有效提高ZL111基多孔铝合金的表观杨氏模量、屈服强度和压缩吸能能力；固溶时效热处理使压缩吸能能力随着孔隙率的增大而呈现规律性减小，并使能量吸收效率对孔隙率和孔径的敏感程度减小。     

改革开放30年:中国的铝板带冷轧工业(2)

到2008年底,中国有180多个铝板带轧制企业,其中大中型企业131个,小企业50个,冷轧生产能力为6 230kt/a,比美国的高2.2%。2002年~2010年,中国的铝板带冷轧能力年平均增长率约31.2%。中国目前拟建的铝板带大项目有十几家。到2010年,中国冷轧铝板带生产能力预计达到8 115 kt/a。     

全自动硫磺灌包机防堵转系统设计

本文针对全自动硫磺灌包机在灌包过程中,破碎机系统易发生堵转,造成全自动硫磺灌包机停机甚至破碎电机过热烧毁的情况,提出了一个防堵转的控制系统设计。该设计通过行程开关判断破碎系统是否堵转,简单、可靠,对生产设备设计和改造具有一定的意义。