AZ31B镁合金在不同温度下的微动磨损行为

采用球/平面接触方式在自制的试验设备上对AZ31B镁合金进行切向微动磨损试验,研究了AZ31B镁合金在20,100,200,300℃下的微动磨损行为,并分析了其磨损机制和摩擦氧化作用。结果表明:在不同试验温度下,镁合金的微动主要通过滑移来实现;随着试验温度的升高,上升阶段时的摩擦因数增大,摩擦因数到达峰值和稳定阶段所需的循环次数减小;随着试验温度的升高,AZ31B镁合金的磨损体积和摩擦副的总磨损体积均先减小后增大,200℃时,AZ31B镁合金的磨损体积最小;在微动磨损过程中,AZ31B镁合金磨痕表面的摩擦氧化起主导作用;当试验温度低于200℃时,AZ31B镁合金磨痕表面形成了铁的氧化物转移膜,磨损体积随试验温度的升高而减小,但在300℃时,铁的氧化物转移膜被破坏,磨损体积增大。     

温度对AZ31B镁合金扩散连接接头性能的影响

为实现镁合金AZ31 B的可靠连接,根据原子扩散理论,对AZ31 B镁合金进行了扩散连接工艺研究.利用VDW-15型扩散设备,对AZ31B镁合金进行了在不同连接温度条件下的扩散连接.利用金相显微镜、扫描电镜、能谱分析仪器等对扩散连接接头组织及连接界面元素成分进行了分析,测试了接头的剪切强度.结果表明,AZ31B镁合金的...     

AZ31B镁合金的数控热渐进成型工艺

采用正交试验方法,对交叉轧制AZ31B镁合金进行数控热渐进成型的工艺试验,考察了AZ31B镁合金板在不同温度和成型工艺参数下的热渐进变形规律。结果表明:最佳成型工艺条件为在250℃时采用0.1 mm的进给量和1 800 mm.min-1的进给速度,此时板材成型极限角可达61°;在热渐进成型工艺条件下板材的厚度变化仍遵循余弦法则。     

AZ31B镁合金板热成形温度优化及合理温度下成形件的组织与性能

研究了温度对AZ31 B镁合金板显微组织与拉伸性能的影响,分析了不同温度热成形件的成形质量,确定了合理的热成形温度并研究了该温度下热成形件的显微组织与拉伸性能.结果表明:200℃热处理后AZ31B镁合金板能较好地保持细小等轴晶组织,随温度升高,晶粒明显粗化;随温度升高,合金的强度下降而塑性提高,200℃时即可具有良好的...     

AZ31B镁合金手机外壳拉深模具设计

以AZ31B镁合金手机外壳的拉深模具设计和实际生产为例,对AZ31B镁合金的拉深成形过程进行研究。实际生产表明,选取合适的模具结构和参数可以改善AZ31B镁合金板材的拉深成形性能;在拉深成形时,通过对坯料温度和模具温度等主要影响因素的控制,可有效地消除AZ31B镁合金在拉深过程中的拉裂缺陷。     

AZ31镁合金方管挤压成型的数值模拟

基于AZ31镁合金热压缩真应力-真应变曲线,计算得到了流变应力方程,分析了合金压缩变形后的显微组织,并用HyperXtrude有限元分析软件对AZ31镁合金方管挤压成型进行了数值模拟,最后进行了试验验证。结果表明:AZ31镁合金的流变应力随变形温度的升高而减小,并在350℃以上较快达到稳态,易于加工成型;热压缩变形后合金中的孪晶组织随温度的升高有所减少,且晶粒不断长大,在高应变速率时由于动态再结晶不充分,晶界附近形成类似"项链"状的细小晶粒组织;有限元模拟分析发现方管角部金属流速低于中心位置,在HyperStudy中经工作带优化后流速分布均匀,采用优化设计的模具挤压生产出了合格的AZ31镁合金型材。     

AZ31镁合金静液挤压试验研究

针对镁合金静液挤压工艺所需设备价格昂贵、没有国产设备的问题,研制了能应用在国产低成本普通压力机上的静液挤压试验装置,并解决了耐高压模具、镁丝挤压速度控制、挤压过程温度自动控制及高压热密封等几个关键技术问题。应用最小二乘法进行曲线拟合,得到了不同挤压比条件下温度与单位静液挤压力数量关系的回归方程。应用国产3150kN 液压机进行了静液挤压工艺试验,得到了力学性能优于轧制丝材的AZ31静液挤压镁合金丝。     

AZ31镁合金静液挤压试验研究

针对镁合金静液挤压工艺所需设备价格昂贵、没有国产设备的问题,研制了能应用在国产低成本普通压力机上的静液挤压试验装置,并解决了耐高压模具、镁丝挤压速度控制、挤压过程温度自动控制及高压热密封等几个关键技术问题。应用最小二乘法进行曲线拟合,得到了不同挤压比条件下温度与单位静液挤压力数量关系的回归方程。应用国产3150kN液压机进行了静液挤压工艺试验,得到了力学性能优于轧制丝材的AZ31静液挤压镁合金丝。     

挤压温度对AZ31镁合金电化学性能和腐蚀形貌的影响

采用平面分流模具热挤压成型制备了内部镶嵌钢芯的AZ31镁合金牺牲阳极,研究了挤压温度对其成形性能、显微组织、电化学性能以及在模拟土壤环境(饱和CaSO4-Mg(OH)2溶液)中腐蚀形貌的影响。结果表明:当挤压比为12,挤压温度为320~410℃时,AZ31镁合金阳极表面成形良好;晶粒尺寸随着挤压温度的升高先减小后增大,最小晶粒尺寸达到12.2μm;随着挤压温度的升高,镁合金电流效率和开路电位均先增大后减小,而表面腐蚀程度先减轻后加深,当温度为380℃时,电流效率和开路电位达到最大,分别为63.93%,-1.586V,此时表面点蚀孔数量最少,腐蚀程度最轻。     

AZ31B镁合金板材旋压成形工艺研究

采用摩擦旋压成形工艺,研究了AZ31B挤压板材供应态试样在不预热的条件下直接进行旋压成形的可行性。结果表明,摩擦升温效应能迅速将坯料温度提高到200～450℃,从而提高镁合金板料的塑性变形能力,可旋压成形出最小直径为31.5mm、高度为9.22mm的镁合金碟形件。实验发现旋压成形的旋轮轴向进给量、旋轮运动轨迹、坯料旋转速度和润滑剂等对镁合金板材的旋压成形有较大的影响。当旋轮采用梳形运动轨迹、轴向进给量为0.22mm、坯料转速ω=900r/min时,采用MoS2钙基脂润滑,可获得较好的旋压成形效果。     

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...     

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.     

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。     

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。     

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.     

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.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

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.