发动机凸轮轴参数化建模与加工力学分析

针对发动机凸轮轴在数控磨削时产生弹性变形与振动的问题,提出了凸轮轮廓曲线相邻三点逐次样条拟合方法。并利用该方法在ANSYS有限元软件中对某凸轮轴进行了APDL参数化建模,对凸轮轴磨削时不同位置和不同转角下凸轮轴的弹性变形量进行了计算公式推导和有限元分析,对凸轮轴的固有频率和磨削约束条件下的振型、谐响应进行了分析。应用三点拟合方法可以快速、准确地建立凸轮轴的有限元模型,而适当选取磨削参数可以减小凸轮轴的弹性变形与振动,从而提高凸轮轴的轮廓精度和升程精度。     

康明斯NT/NTA855型柴油机喷油定时的调整

康明斯NT/NTA855型柴油机喷油定时偏移的调整方法有：＂凸轮轴正时齿轮轴向移动法＂和＂偏移凸轮轴键法＂。对于凸轮轴正时齿轮轴向移动法,移动量一般是根据经验公式计算,这受维修人员经验影响很大,同时有效调整量有限,因此很少使用。本文将重点阐述偏移凸轮轴键法。     

柴油发动机凸轮轴疲劳断裂研究

凸轮轴是发动机关键部件,控制着进排气系统的配气相位,凸轮运转时承受着交变载荷,长时间工作易产生疲劳裂纹,裂纹扩展会导致凸轮轴的断裂,造成配气部件的损坏。针对某柴油发动机凸轮轴断裂情况,根据疲劳断裂生长理论,运用实验分析和有限元分析方法,对凸轮轴疲劳断裂成因进行分析,计算出了凸轮轴极限应力和疲劳安全系数,分析了凸轮轴的疲劳安全可靠性。同时发现柴油发动机凸轮轴在制造和设计中存在的问题,提出避免柴油发动机凸轮轴发生疲劳断裂的措施,为设计高质量的凸轮轴提供依据。     

平板车制动系统凸轮轴断裂分析及工艺改进

通过对焊接后的凸轮轴在校直时产生断裂的原因，进行分析，改进了凸轮轴的焊接和热处理工艺，并根据热处理状态对焊后的凸轮轴进行了抗扭试验对比,证明了工艺改进后的凸轮轴能够满足其使用性能的要求。     

非圆凸轮轴带轮对正时皮带传动系统的影响

采用仿真模拟分析了非圆凸轮轴带轮对正时皮带传动系统的影响。以某3缸增压缸内直喷汽油机为例,首先确定了正时系统的负载,并考虑了VVT和曲轴转速波动的影响,仿真分析非圆凸轮轴带轮对正时皮带受力、皮带颤振及曲轴与凸轮轴相对角度偏差的影响。结果表明:采用非圆凸轮轴带轮不能优化皮带受力,能使各工况下的皮带颤振、曲轴与凸轮轴相对角度偏差满足设计要求。研究结果对改善正时皮带传统系统的动态性、提高正时皮带寿命及发动机的可靠性具有重要意义。     

凸轮磨削形面误差分析及其改进措施

凸轮轴在普通凸轮磨床上加工时通常凸轮形面精度难以保证,本文对凸轮轴在普通凸轮轴磨床加工中所产生的形面误差和磨削过程中余量变化进行了分析,并对其提出改进办法。     

发动机断齿故障机理的动力学仿真分析与实验研究

以一台直列六缸发动机为研究对象,建立发动机齿轮传动系统(曲轴、曲轴齿轮、中间齿轮、凸轮轴齿轮和凸轮轴)的模型,运用ADAMS多体动力学仿真软件,模拟分析凸轮轴齿轮在正常运行和断齿故障及凸轮轴轴向窜动和中间齿轮径向振动两种故障下,凸轮轴齿轮的频率变化情况,并与实际故障案例进行了对比分析。结果表明,当凸轮轴齿轮发生断齿故障时,其基频、三倍频和四倍频均会增加,且各阶频率都会增大,这与实际故障案例非常吻合;当凸轮轴发生轴向窜动和中间齿轮径向振动时,便会引起凸轮轴运动过程中的基频、三倍频和四倍频的增大,各阶频率的明显增大,因此以上两种情况都有可能造成齿轮不平稳运行,导致断齿故障的发生。     

柴油发动机凸轮轴断裂故障分析及处理对策研究

凸轮轴是活塞发动机里的一个部件，也是汽车发动机配气结构中的重要零部件，它的作用是控制气门的开启和闭合动作。因此在设计中对凸轮轴在强度和支撑方面的要求会很高，特种铸铁是它的材质，偶尔也采用锻件，所以在发动机中凸轮轴占据着很重要的地位。但由于凸轮轴运转时需要承受着交变荷载，长时间的工作会产生疲劳裂纹，而造成凸轮轴异常受力疲劳断裂的主要原因是，止推片和凸轮轴两者之间产生摩擦，严重粘着磨损。本文主要针对分析柴油发动机凸轮轴断裂的故障及处理对策。     

反靠靠模时,标准凸轮基圆半径与滚轮半径的关系

凸轮轴是内燃机的一个主要零件。在凸轮轴的制造过程中,首先要加工出一个标准凸轮轴。基圆半径是凸轮轴的一个基本的结构参数。标准凸轮的基圆半径,一般都是采用实际凸轮轴的基圆半径(以下称标准半径)。我们在制造475汽油机标准凸轮轴时,由于受当时设备条件的限制,基圆半径较标准半径大50毫米(以下称大半径)。实践证明,使用大基圆半径的标准凸轮轴生产出的凸轮轴,各项指标均达到设计要求。按此方法,我们又为480汽油机及其改型制造的两种标准凸轮轴,结果均较理     

凸轮磨削形面误差分析及其改进措施

凸轮轴在普通凸轮磨床上加工时通常凸轮形面精度难以保证,本文对凸轮轴在普通凸轮轴磨床加工中所产生的形面误差和磨削过程中余量变化进行了分析,并对其提出改进的办法。     

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。     

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。     

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。     

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.     

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.     

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.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.