铝含量对粉末冶金制备镁铝锆合金组织和力学性能的影响

运用粉末冶金工艺制备了Mg-xAl-1.5Zr(x=0,2,4,6,8,质量分数/%)合金,研究了铝含量对其组织和力学性能的影响。结果表明:镁铝锆合金主要由α-Mg基体、锆颗粒、β-Mg17Al12相组成,还存在一些微小的孔洞;铝含量的增加使合金组织趋于均匀化;Mg-6Al-1.5Zr合金具有最高的硬度和抗弯强度,分别为79.7HV和224MPa,但其塑性较差,断口呈准解理断裂的特征。     

电极形状对铝-钢点焊接头组织及力学性能的影响*

研究6061-T6铝合金-SUS301L不锈钢异种金属电阻点焊接头的微观组织特点及电极形状的影响规律。结果表明,铝-钢点焊接头具有熔-钎焊特征,铝合金熔核由α-Al胞状晶、胞状树枝晶和树枝晶组成,铝/钢界面层具有双层结构,靠近铝熔核侧主要为细针状Fe₄Al₁₃,靠近不锈钢侧主要为Fe₂Al₅金属间化合物,接头主要为界面断裂模式,铝/钢界面是点焊接头最薄弱的区域。电极形状对铝合金-不锈钢点焊接头具有明显的影响。获得的优化电极形状为：不锈钢侧为圆形平面电极,电极端面直径为10 mm;铝合金侧为球面电极,球面半径为35 mm。在优化电极条件下,铝合金-不锈钢点焊接头的熔核直径、拉剪力及压痕率分别为7.5 mm、4.7 kN和13.5%。与采用F型电极相比,其熔核直径和拉剪力分别提高53.1%和56.7%,压痕率降低47.3%。因此,采用优化电极更有利于改善铝合金-不锈钢电阻点焊接头的力学性能及表面质量。     

T4热处理对不同钕含量AM60镁合金显微组织和力学性能的影响

用真空电阻炉、在氩气保护下制备了不同钕含量的AM60合金,用箱式电阻炉对其进行了T4热处理;研究了两种状态合金显微组织和力学性能随钕元素含量的变化规律.结果表明:铸态合金的显微组织均主要由α-Mg基体相、β-Mg17 Al12相和Al11 Nd3相组成;T4热处理后,β-Mg17Al12相溶解到α-Mg基体相中,合金晶...     

AZ31/7005异种材料填丝GTAW接头组织分析

为获得良好的镁铝异种金属焊接接头,采用钨极氩弧焊填加镁铝合金焊丝ER5183、ER5356的方法进行焊接,利用金相显微镜、扫描电镜对两种焊接接头的微观组织对比分析,利用电子探针、能谱仪研究接头的元素分布,利用显微硬度计对两种焊接接头的显微硬度对比分析。结果表明,采用ER5183、ER5356镁铝合金焊丝,接头未形成连续片状金属间化合物层,能够形成良好的焊接接头;采用ER5183焊丝获得焊缝比采用ER5356组织更为致密,脆硬的Mg-Al金属间化合物少;两种焊接接头镁侧熔合区主要组织为α-Mg固溶体+γ-Al12Mg17的共晶组织和晶界析出相γ-Al12Mg17组织;镁侧焊缝区主要为α-Mg固溶体+γ-Al12Mg17的固溶体组织。焊接接头以Mg、Al元素为主,在镁侧熔合区,Mg、Al质量分数保持稳定,镁侧焊缝区,Mg质量分数逐渐降低,Al质量分数逐渐升高,到铝侧焊缝区达到稳定值。适当控制焊丝中Mg的质量分数,使金属间化合物弥散分布,能够改善AZ31镁合金和7005铝合金的焊接性。     

钕变质处理对Mg-8Al合金显微组织和拉伸性能的影响

在Mg-8Al合金中加入不同含量(质量分数0~0.8%)的稀土钕对其进行变质处理,研究了钕变质处理对合金显微组织和拉伸性能的影响。结果表明:钕的加入改变了合金中初晶α-Mg的形态,使α-Mg树枝晶分支发达,但细化晶粒的效果不明显;加入钕变质前,合金的共晶组织为部分离异共晶,加入钕后的共晶组织为完全离异共晶,共晶组织由未变质时的连续网状分布变为断续分布;当加入钕的质量分数为0.4%时,合金的室温拉伸性能最佳,抗拉强度、屈服强度和伸长率分别较变质前提高了24%,11%和61%,此时的组织中开始有少量板条状稀土相Al11Nd3析出。     

Mg74Zn25Y1三元合金中的准晶相

旨在研究高镁、低锌和低钇合金中准晶的形成和分布,降低材料的密度,研究制备准晶增强自生复合材料的可行性。用金相显微镜和SEM分析低Zn和低Y含量下,Mg74Zn25Y1合金普通凝固组织;EDS分析合金和凝固组织中各相的成分;XRD分析凝固组织的相组成;TEM确定准晶的结构。研究结果表明,Mg74Zn25Y1合金的凝固组织为?-Mg+MgZn+Zn60Mg30Y10。其中,Zn60Mg30Y10准晶为五次对称的20面体结构,微观形貌呈现出完整五瓣花瓣和没有完全长大的五边形。准晶晶粒尺寸小于50 ?m。     

2A02铝合金棒材粗晶环对航空发动机叶片的影响

2A02铝合金是制备航空发动机压气机叶片的重要材料,该合金棒材存在一种铝合金棒材特有的组织缺陷——粗晶环,对棒材的力学性能有不利影响。文章针对2A02铝合金棒材的粗晶环形成机制、影响因素、控制措施以及粗晶环对铝叶片的影响进行研究。研究表明：2A02铝合金棒材的粗晶环深度是固定不变的,但热处理保温时间将影响粗晶环显示的深度;粗晶环深度在棒材长度方向上是不均匀分布的,可导致棒材的粗晶环遗传至铝叶片锻件表面;铝叶片表面的局部粗晶将导致铝叶片的力学性能降低。     

双辊连铸AZ61镁合金薄带坯的工艺与显微组织

采用规格为φ250 mm x 150 mm的立式双辊连铸系统制备了3～4 mm厚、150 mm宽的AZ61镁合金薄带坯;研究了水口形状和浇铸温度等连铸工艺参数对薄带坯显微组织和表面质量的影响.结果表明:采用B型水口制备的AZ61薄带坯的表面裂纹较少,表面质量较好;随着浇铸温度的降低,薄带坯表面裂纹数量增多,AZ61薄带坯的组织由先析α-Mg和过饱和α-Mg基体组成;当浇铸温度为630℃时,薄带坯的组织细小均匀;当浇铸温度介于固相线和液相线之间时,薄带坯组织中存在局部粗大的α-Mg树枝状晶.     

Al-5Ti-1B细化剂添加量对含铈铸造铝合金组织和拉伸性能的影响

在添加质量分数0.1%铈的基础上,对比研究Al-5Ti-1B细化剂质量分数(00.4%)对A356铸造铝合金组织及拉伸性能的影响。结果表明:随着Al-5Ti-1B细化剂含量的增加,α-Al树枝晶的平均二次枝晶间距先降后增,当细化剂的质量分数为0.2%时,平均二次枝晶间距最小,为37.3μm;添加适量细化剂能促使共晶硅由狭长纤维状向粗短棒状的转变,从而降低共晶硅的等效直径和长宽比,过量细化剂则会引起共晶硅的尖锐化;添加细化剂后,铝合金的抗拉强度和断后伸长率均提高,且随着细化剂含量的增加呈先增后降的趋势;添加质量分数0.2%细化剂时铝合金的综合变质效果最佳,此时铝合金的拉伸性能最佳,抗拉强度和断后伸长率较未添加细化剂时的分别提高了20.7%和66.7%。     

铜和锶对铝-镁-硅基合金板材显微组织及力学性能的影响

采用DSC、XRD、SEM及TEM等分析手段,研究了铜和锶对铝-镁-硅基铝合金汽车车身板材显微组织和力学性能的影响。结果表明：铜的加入,可以使合金形成强化的四元相-Q相,随着铜含量的增加,合金板材的力学性能明显增加,当铜含量为0．86％（质量分数）时,合金的巩达到333MPa,σ0．2达到182MPa;加入锶,可明显细化晶粒,促进时效相的析出,并将β（Al5FeSi）相转变为α（AlsFe2Si）相,提高合金板材的力学性能;在不同铜含量的合金中加入0．033％锶后,可使其抗拉强度提高10～20MPa。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...