焊后热处理对7A04铝合金水下搅拌摩擦焊接接头组织性能的影响

对7A04铝合金板进行水下搅拌摩擦焊接(Submerged Friction Stir Welding,SFSW),并对焊接接头进行焊后热处理(Post Weld Heat Treatments,PWHT),研究焊后热处理对接头组织性能的影响。结果表明:焊后热处理接头呈现出弥散分布的细小析出相形貌,明显优于SFSW接头呈现出的少量析出相分散分布的特征。与SFSW接头相比,焊后热处理明显改善接头的力学性能。接头焊核区的平均硬度值提高了39.7HV,抗拉强度提高了67MPa,达到母材抗拉强度的96.1%,接头的应变硬化能力增强,拉伸断口呈现微孔聚合和解理混合断裂特征。     

7A52铝合金搅拌摩擦焊的焊缝成形

针对7．6mm厚的7A52铝合金，研究了搅拌头的形状和焊接工艺参数对焊缝成形的影响，分析了搅拌摩擦焊缺陷产生的原因。结果表明，搅拌头的形状决定了焊接时焊缝成形的旋转速度范围；搅拌头旋转速度、焊接移动速度、焊接倾角、搅拌头轴肩压入被焊接件表面深度等都对搅拌摩擦焊焊缝成形有重要影响，只有合适的工艺匹配才能保证焊缝成形良好。     

机动武器系统的含间隙动力学研究——上篇:含摩擦碰撞模型

在对若干模型比较的基础上 ,提出一种新的含摩擦碰撞模型。该方法将一些基本关系设定为由试验或理论估算得到的一般函数的形式 ,在近似“磁滞”碰撞力模型中引入了速度因子 ,得到碰撞力模型 ;将摩擦作用划分为滑动、滚动和转动三种类型 ,分别考虑其影响 ;综合考虑接触力和摩擦力 ,最终得到了三维空间内矢量形式的机动武器系统含摩擦碰撞模型     

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激光重熔对NiCrBSi等离子喷涂层显微结构和性能的影响

1Crl8Ni9Ti不锈钢表面的NiCrBSi等离子喷涂层存在孔洞及与基体结合差等缺陷,为此进行了激光重熔处理.采用扫描电镜和显微硬度压痕仪分别对涂层的显微结构和力学性能进行了对比研究,采用SRV试验机评价了涂层激光重熔前后的滑动摩擦磨损性能,研究了激光重熔对NiCrBSi等离子喷涂层结构和性能的影响.结果表明:经过激...     

A novel equal channel angular pressing design to eliminate punch deflection and to reduce the pressing force

In the present study a new design of the equal channel angular pressing die and punch is introduced. The new design eliminates the deflection of the punch and at the same time lowers the frictional forces by reducing the contact area. In order to show the capability of the new design, the Al-7075 alloy samples were processed in two equal channel angular pressing dies. The measured data for the novel and conventional equal channel angular pressing processes were compared. The microstructure of the processed samples was examined with scanning electron microscopy and transmission electron microscopy. The results of the experimental study revealed that the novel die can fully eliminate the risk of the punch deflection and simultaneously reduce the maximum required pressing force by about 3.1 % to 9.8 % for 16 % to 40 % reduction in frictional contact surfaces. The analysis of experimental results showed that there is non-linear relation between the frictional contact area and the pressing load. In addition, it is shown that despites high contact pressures and high temperatures the use of graphite as a lubricant between sliding surfaces can considerably reduce the pressing load.     

磁悬浮拉幅定型传送单元

提出了一种新型的用于拉幅定型机中的磁悬浮拉幅定型传送单元,介绍了该传送单元的结构及其工作原理,分析了磁悬浮垂直支承系统和水平导向系统的工作过程及受力情况。初步试验表明：与传统的拉幅定型传送装置相比,该传送单元具有传送精度高、抗干扰能力强、能耗低、噪音小、结构紧凑等优点。     

Strength and Frictional Properties of Popcorn Kernel as Affected by Moisture Content

Strength properties and dynamic coefficient of friction of popcorn kernels were evaluated as a function of moisture content in the range of 7.78–16.72 g/100 g dry solids. In order to determine strength properties of the kernels that are in terms of deformation at rupture point, rupture force, energy absorbed, hardness, and toughness of the popcorn kernels were quasi-statically loaded between two parallel plates. To determine frictional properties, friction tests were performed on aluminum, steel, and fiberglass surfaces. The values related to the strength properties, in general, decreased as the moisture content increased. On the other hand, the dynamic coefficient of friction of the popcorn kernels increased with increasing moisture content.     

有机导电纤维嵌织织物摩擦静电性能研究

通过理论分析获得有机导电纤维嵌织织物摩擦静电电压衰减规律以及摩擦静电峰值电压变化情况,并对有机导电纤维不同间距嵌织织物摩擦静电性能进行测试验证.结果表明,导电纤维嵌织织物摩擦静电电压衰减规律呈现自然对数底的负指数函数的变化规律;摩擦静电荷的感应峰值电压随导电纤维的不同嵌织距离的增加而增大,两者变化关系呈现为指数变化规律.     

丁腈胶辊技术特性及应用技术与成纱质量的关系(二)

以棉纺牵伸理论为基础,全面论述了胶辊的结构、弹性和硬度与成纱条干均匀度、强力的关系;胶辊硬度与摩擦因数、钳口线宽度的关系;胶辊直径、套差与成纱质量的关系;分析了高弹性低硬度胶辊的技术特性及改善成纱条干均匀度的机理,指出胶辊制作与维护保养工作中要特别重视的问题和适宜的纺纱工艺配置,认为理想的纺纱牵伸胶辊,必须具有优良的弹性、较小的压缩变形和优良的耐磨性、良好的抗静电性与吸放湿性、稳定的硬度和抗臭氧老化龟裂性能等,才能保证其适纺性和改善成纱质量