浅谈曲轴的冷滚压强化工艺

内燃机曲轴的主要破坏形式是断裂和轴颈磨损，其断轴率为0．5％～2％，这是因为曲轴的结构及其所受的载荷使其应力分布极不均匀，在主轴颈、连杆轴颈与曲拐相连接的过渡圆角处产生了比曲拐同截面的名义应力高出数倍的集中应力峰值所导致的。过渡圆角处的最大弯曲应力占80％，扭转应力仅占20％，一系列的应力分析和大量的曲轴断裂实例表明，断裂一般发生在连杆轴颈过渡圆角与主轴颈过渡圆角的对角线上。     

空压机曲轴动力学仿真与有限元分析

结合虚拟样机技术和有限元分析技术,利用Pro/E、ADAMS以及NX软件,建立空压机曲轴连杆机构实体模型,对曲轴连杆机构进行动力学仿真,并对曲轴进行有限元分析。根据在ADAMS软件中曲轴连杆机构的运动仿真,得到曲轴连杆轴颈处的受力情况;进而在NX-NASTRAN软件中对曲轴整体进行应力、应变分析,从分析结果可以知道,曲轴连杆轴颈与连杆臂过渡圆角处极易发生应力集中现象,而空压机曲轴在循环工况下所受的交变应力也会加剧影响曲轴的疲劳寿命。这对曲轴寿命研究与分析具有重要意义,也为曲轴圆角滚压强化工艺提供了支持。     

曲轴深滚压工艺及滚压力异常分析和处理

曲轴作为典型的非均质结构零件,尺寸过渡处存在应力集中。研究和实践表明,曲轴的疲劳破坏大多发生在曲柄与主轴颈、连杆轴颈的过渡圆角处。为了提高其抗疲劳强度必须对曲轴的这些部位实施滚压强化工艺。结合曲轴圆角滚压强化和校直系统,对德国Hegenscheidt圆角滚压校直机床的原理、滚压工艺以及滚压校直过程中滚压力的变化进行研究．并对滚压力异常进行分析。     

内燃机曲轴动态特性分析及结构改进

为了减少曲轴在工作时振动断裂,本文针对曲轴的振动特性进行研究。利用有限元软件对三种不同材料曲轴进行模态分析和谐响应分析,分析结果表明QT800为材料的曲轴在防振动方面的效果好于其他两种材料,曲轴的断裂部位最有可能发生在曲拐之间过渡圆角处。通过增大曲轴过度圆角半径和连杆轴颈直径能减少曲轴出现振动断裂情况的发生。     

汽油机曲轴断裂故障的原因分析

通过对汽油机曲轴断裂断口部位的金相组织、力学性能及轴颈与曲柄过渡圆角处进行的检测和分析,结果表明,曲轴的硬度偏低于技术标准要求,再加上连杆颈与平衡块直角交接处应力集中是导致曲轴疲劳断裂的主要原因。通过改进设计和工艺整改,可使曲轴完全符合发动机安全性能的技术要求。     

柴油机曲轴应力敏感度分析

曲轴是柴油机的重要组成部分,为了确定曲轴的主轴颈半径、连杆轴颈半径、过渡圆角半径和曲柄臂厚度这几个尺寸参数中,哪一个对曲轴危险部位的应力影响最大,用ANSYS软件对简化的曲轴单拐进行参数化建模,再用ANSYS软件的PDS模块对其进行了基于Spearman秩相关系数的敏感度研究。分析结果表明:过渡圆角半径对曲轴危险部位的应力敏感度最大。     

球墨铸铁曲轴表面强化处理技术

柴油机曲轴承受复杂交变的弯曲-扭转载荷和一定的冲击载荷,疲劳断裂是曲轴的主要破坏形式,裂纹源易发生在连杆轴颈与曲臂过渡圆角处,工艺上提高曲轴疲劳强度的方法主要是圆角强化,在其表层形成一定的压应力来实现的。介绍了滚压、淬火、氮化、喷丸、激光冲击强化等工艺方法,分析曲轴强化机理和工艺方法,为提高曲轴使用寿命提供了参考。     

重卡六缸内燃机曲轴不同位置角静力学分析与结构优化

为研究内燃机曲轴在实际工况下不同位置角的应力应变分布特征,利用Creo软件建立材质为QT700-2的重卡直列六缸内燃机左式曲轴三维模型,根据内燃机实际受载情况对曲轴施加约束和载荷并进行静力学仿真。结果表明：曲轴上最大应力发生在曲轴轴颈与曲柄臂的过渡圆角处,连杆轴颈中心出现最大形变,工作过程中第4缸对应曲轴轴段部分的应力变化最大。据此对曲轴结构进行优化,将过渡圆角半径增加40%后,最大应力值减小了约10%;结合企业曲轴故障返修情况,发现优化之后减少了曲轴早期故障率,提高了内燃机曲轴的可靠性。     

柴油机曲轴圆角处激光喷丸后的残余应力分布特牲研究

采用ANSYS有限元软件,研究了柴油机曲轴圆角处激光喷丸后的残余应力分布规律,并得到相应的模拟数值。将圆角处模拟的结果与未喷丸曲轴的实测点应力值进行对比分析,结果得出,经过喷丸处理后,曲轴连杆轴颈部位的圆角处残余应力由拉应力变成压应力．材料的硬度和强度明显得到提高。通过此类的有限元仿真,可以对激光喷丸的相关参数进行优化。     

曲轴激光淬火处理方法的研究

本文从曲轴实际受力分析出发,提出了曲轴轴颈及过渡圆角处采用激光淬火表面处理的两种方法,并讨论了各自的优缺点.实验与分析证明采用轴颈周向螺旋扫描,过渡圆角处激光束与轴心线成45°角的部分圆角的激光扫描处理方法,更能获得较为均匀的硬化层和残余应力,从而达到了提高曲轴抗磨损,抗疲劳的综合机械性能.     

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...     

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.     

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.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

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...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.