Stress and failure analysis of the crankshaft of diesel engine

In this work the failure analysis of the crankshaft of diesel engine was performed. Visual examination of the crankshaft fracture showed that beach marks, typical for fatigue failure were observed. Additional observations of the crack initiation zone indicated that crack origin was not covered by material defects or corrosion products. Performed hardness test of the fractured crank pin showed that large HRC values were observed in central part of the pin only. On the corner of cylindrical pin surface where the crack origin was located the hardness of material was much smaller. In order to explain the reason of premature crankshaft damage, the finite element method was utilized. The results of nonlinear static analysis showed that during work of the engine with maximum power the high stress area was located in crack initiation zone. Based on results of performed investigations it was concluded that the main reason of premature fatigue failure was high-cycle fatigue of the material in external zone of the crank pin where the small structural radius was designed. In final part of the work the recommendations for increase of the fatigue life of analyzed crankshaft were formulated.     

基于ADAMS的柴油机曲轴扭振仿真

以某V型8缸柴油机为研究对象,通过多体动力学方法对该曲轴进行扭振研究。首先在ADAMS中建立曲柄连杆机构的刚体模型;然后把曲轴作为柔性体,建立曲轴的有限元模型并对其进行模态计算;最后用曲轴的柔性体模型代替曲柄连杆机构的曲轴刚体模型,得到曲柄连杆机构的刚-柔混合体动力学仿真模型。对曲轴在正常工况下和单缸熄火时的扭振进行研究,得到曲轴在正常工况下和单缸熄火时的扭振特性。     

利用简谐扭振幅值诊断内燃机故障缸功率损失

依据内燃机曲轴扭转振动的基本理论，提出了一种利用实测曲轴扭振信号单谐次分量的幅值诊断内燃机故障缸功率损失的新方法，该方法能简便地估算出故障缸的停缸率。讨论了引起曲轴扭转振动的激振力矩，给出了简谐扭转振动角位移与对应简谐力矩的关系式。以某6135柴油机为对象进行了仿真计算和实验分析。研究结果表明，利用0．5谐次扭振位移幅值可以判断出内燃机故障缸的停缸率，验证了该方法的可行性和工程应用价值。     

曲柄销轴断裂分析

对曲柄销轴在采油设备上的安装配合情况进行了调查，在此基础上，分析了销轴在采油设备工作时的受力情况，并通过化学分析、金相检验和扫描电镜等方法对销轴断裂失效进行了分析。结果表明，该销轴在交变偏斜拉应力的作用下，在销轴的应力集中处——退刀槽根部产生疲劳裂纹，最终导致疲劳断裂。另外钢材质量欠佳、组织不良也促进了断裂过程的进行。     

Cam Profile Grinding CNC System Based on Open Architecture

This paper studies some key technologies of CNC system for cam grinding. The mathematical motion model for cam grinding is established according to the harmony of re-ciprocating motion of the grinding wheel and the rotating motion of the workpiece. The method of using the linear servomotor to accomplish the grinding wheel tracking is devel-oped and the dynamic model of the system is analyzed. Then the cross-coupled biaxial error compensation model is proposed. Finally,the hardware and software of the control system are designed based on open architecture. Some algorithms, such as spline fitting and inter-polation for cam contour, velocity control and feed control,are presented to improve grinding precision.     

A numerical study of crack shielding and deflection under extensive plasticity

Experimentally observed crack deflection events in multi-layered material systems, occurring even under pure mode-I loading, are here simulated and explained through elasto-plastic finite element modelling. The crack tip opening displacement is adopted as the crack driving force and estimated along crack paths whose deflection is predicted using the maximum tangential strain criterion. Shielding conditions that promote deflection and bifurcation are evaluated. It is shown that, under conditions of extended plasticity, CTOD evolution as a crack approaches an interface can reveal crack shielding and amplification, and that crack deflection and growth can be assessed from the variation of tangential strains around the crack tip.     

花型齿冷精密成形数值模拟及工艺分析

目的研究某曲轴减震皮带轮花型成形板料增厚的可行性及花型齿轮廓度差。方法运用有限元模拟软件,建立了曲轴减震皮带轮的有限元模型,选取了不同的装模方式、凸模分流孔和坯料减压孔,对曲轴减震皮带轮精压成形过程进行了数值模拟。结果模拟获得了不同装模方式、凸模分流孔大小和坯料减压孔大小对载荷和花型齿成形质量的影响,并对结果进行了总结。结论选择合适的装模方式、凸模分流孔和坯料减压孔,不仅可以较好地满足花型齿精度要求,而且还能有效地降低成形载荷和实现薄板局部增厚,实现降本增效的效果。     

Research on Contour Error Based on CNC Multi-axis Motion Control System

The contour error was analyzed based on CNC multi-axis motion control,the contour error model was obtained focused on beeline and different radius of curvature and common contour of curve,for a CNC biaxial motion control system and the mechanism of producing contour error and the relationship between tracking error and contour error were presented.The theoretical and practical significance of modeling error and controlling error in motion control systems was carried out.     

钢轨高速打磨试验台的切向磨削力修正方法研究

进行钢轨高速打磨试验是研究钢轨高速打磨机理的重要手段。而钢轨高速打磨试验台与打磨列车现场打磨作业的主要差别是试验台的钢轨沿纵向方向具有有限曲率半径,而现场钢轨沿纵向的曲率半径接近无限大。这一现象使得试验台上测得的砂轮与钢轨间的切向磨削力与现场打磨过程中的实际磨削力有差别。该文根据砂轮磨削原理建立了一种可考虑钢轨沿纵向曲率半径的砂轮切向磨削力计算方法。通过与试验数据的对比,表明该方法计算得到的磨削切向力与试验数据有较好的吻合。该文利用所建立的方法给出了将试验台切向磨削力修正到现场切向磨削力的修正系数k,并分析了打磨过程中的法向加载力以及圆盘曲率半径对k值的影响。     

航空活塞发动机曲轴配重组件失效机理研究

某型飞机在使用过程中,多次发生配重组件破损,滚柱飞出而击伤发动机,严重威胁飞行安全.为分析配重组件破损的原因,基于配重的工作原理,分析了发动机油门快速操纵对曲轴扭转振动的影响,依据扭纵耦合理论,对滚柱冲击挡片的机理进行了研究,并完成了试验验证.建立了配重组件在冲击载荷作用下的有限元计算模型,并对配重组件进行了机械性能测...     

诊断内燃机各缸作功均匀性的曲轴简谐扭振反算法

简要介绍了各种诊断内燃机各缸作功均匀性的方法及其局限性；依据内燃机动力学的基本理论，提出了一种利用轴系一个惯量的扭振信号多谐次分量反算内燃机各缸作功均匀性的新方法；详细推导和说明了该方法的基本原理；以某6L240柴油机为对象，进行了选用3个谐次的扭振简谐分量准确反算出各缸作功均匀性的仿真研究。理论分析和仿真研究表明．新方法只需以各缸停缸实验得到的扭振幅频特性参数为基础，利用一个惯量的扭振信号多谐次分量就可反算出内燃机各缸平均有效压力。方法简便准确，既不依靠轴系结构参数等较难获得的先验知识，又适用于内燃机轴系存在扭振的情况。     

RR装置上曲轴镦锻工艺优化研究

以16V280曲轴为试验对象,通过对RR装置的镦锻工艺、曲柄臂锻件形状和锻造模具结构优化,研究了采用小直径坯料的情况下16V280曲轴曲柄臂的成形情况。试验结果显示,优化后的预上弯镦锻工艺,能保证在RR装置上采用小直径坯料镦锻曲轴可行。     

Boundary element solution of thermal creep flow in microfluidic devices

Flow in rarefied gases can be caused by a tangential temperature gradient along the contour boundaries (tangential heat flux), without the presence of any other external driven force, inducing a fluid motion from colder to hotter regions. This phenomenon is known as thermal creep and has gained importance in recent years in connection with micro-scale gas flow systems. Prediction of the flow field in micro-systems can be obtained by using continuum based models under appropriate boundary conditions accounting for the slip velocity due to tangential shear rate and heat flux. In this work a boundary integral equation formulation for Stokes slip flow, based on the normal and tangential projection of the Green's integral representational formulae for the velocity field is presented. The tangential heat flux is evaluated in terms of the tangential gradient of the temperature integral representational formulae presenting singularities of the Cauchy type, which are removed by the use of an auxiliary potential field. These formulations are used to evaluate the performance of different microfluidic devices.     

Three Dimensional FE Analysis on Flange Bending for TC4 Alloy during Shear Spinning

In this paper, the 3D elastic-plastic simulation was carried out by using finite element （FE） code according to the phenomena of flange keeping straight, bending towards headstock and bending towards tailstock in the shear spinning experiments for TC4 alloy. The simulation results for the three kinds of deformations of the flange agree well with the experimental results. So it is possible to explain the reason of flange bending by analyzing the strain vectors in the flange for the three kinds of deformation, which shows that it is important to apply the FE simulation technology for predicting the defects and optimizing the spinning process of TC4 alloys.     

振动顺料机动态特性仿真研究及优化设计

目的为保证振动顺料机在各种复杂工况下的工作可靠性,通过对振动顺料过程的仿真研究,优化其动态特性,提高顺料效率。方法从振动系统激振方式的角度出发,对运动激励和力激励2种激振方式的动态可靠性进行分析和比较,在此基础上以采用曲柄滑块机构的强制运动激励为激振方式的振动顺料机为研究对象,利用Solid Works软件建立振动顺料机的三维装配体模型,并在ADAMS中进行相关仿真模型的建立及其参数试验与优化。结果曲柄转速和曲柄长度对顺料效率具有明显影响,通过仿真得到了振动顺料机曲柄滑块机构中曲柄转速和曲柄长度的一组最优参数值分别为376 r/min和12.85mm。结论通过对曲柄转速和曲柄长度参数的仿真试验及其优化设计,提高了振动顺料机的顺料效率。     

Equivalence of the driving elastic forces in flexible multibody systems

When the driving joint forces, determined using the inverse dynamics procedure, are applied in the feedforward control of mechanical systems, discrepancies between the specified and the actual motion are observed. In some recent publications, these discrepancies were attributed to the wave phenomenon. It is shown in this investigation that the solution of the inverse dynamics of flexible mechanical systems defines two types of driving forces which can be classified as driving joint forces and driving elastic forces. The driving joint forces which depend on the deformation of the flexible bodies define the torque and the actuator forces which must be applied at the joints. The driving elastic forces are associated with the deformation degrees of freedom, and therefore, there is no gaurantee that an algorithm that ignores these driving elastic forces will converge and achieve the desired solution. It is the objective of this investigation to examine the nature of the driving elastic forces in the solution of the inverse dynamics problem, and demonstrate that the driving elastic forces associated with two different sets of vibration modes which produce the same physical displacements are basically the same and they differ only by a co-ordinate transformation. The effect of the selection of the deformable body co-ordinate system on these forces is also examined numerically using a slider crank mechanism with a flexible connecting rod.     

Cam Profile Grinding CNC System Based on Open Architecture

This paper studies some key technologies of CNC system for cam grinding. Themathematical motion model for cam grinding is established according to the harmony of re-ciprocating motion of the grinding wheel and the rotating motion of the woorkpiece. Themethod of using the linear servomotor to accomplish the grinding wheel tracking is devel-oped and the dynamic model of the system is analyzed. Then the cross-coupled biaxial errorcompensation model is proposed. Finally,the hardware and software of the control systemare designed based on open architecture. Some algorithms, such as spline fitting and inter-polation for cam contour, velocity control and feed control, are presented to improvegrinding precision.     

Numerical implementation of generalized Coddington equations for ophthalmic lens design

A method for general implementation in any software platform of the generalized Coddington equations is presented, developed, and validated within a Matlab environment. The ophthalmic lens design strategy is presented thoroughly, and the basic concepts of generalized ray tracing are introduced. The methodology for ray tracing is shown to include two inter-related processes. Firstly, finite ray tracing is used to provide the main direction of propagation of the considered ray at the incidence point of interest. Afterwards, generalized ray tracing provides the principal curvatures of the local wavefront at that point, and its orientation after being refracted by the lens. The curvature values of the local wavefront are interpreted as the sagital and tangential powers of the lens at the point of interest. The proposed approach is validated using a double-check of the calculated lens performance in the spherical lens case: while finite ray tracing is validated using a commercial ray tracing software, generalized ray tracing is validated using a software application for ophthalmic lens design based on the classical version of Coddington equations. Equations of the complete tracing process are developed in detail for the case of generic astigmatic ophthalmic lenses as an example. Three-dimensional representation of the sagital and tangential powers of the ophthalmic lens at all directions of gaze then becomes possible, and results are presented for lenses with different geometries.     

On the prediction of the roundness error in BTA deep hole machining based on the stochastic description of the cutting tool motion

This paper presents a methodology of predicting the maximum possible out-of-roundness of the hole produced, in BTA deep hole machining, as a function of certain machining parameters. Based on the solutions of the stochastic differential equations representing the machine tool-workpiece system in BTA deep hole machining, and the true cutting tool motion, an index describing the upper bound of the roundness error is defined. A parametric analysis of the out-of-roundness index is carried out. This analysis points out that at a low length-to-diameter ratio of the cutting tool, the axial force is the predominant factor causing the tool-tip deviation from the ideal motion, and that the radial and tangential forces are the major causes for the tool tip deviation at high length-to-diameter ratio of the cutting tool. The experimental measurement of out-of-roundness of the specimens under different machining conditions shows that the roundness error obtained lies within the zone described by the theoretical prediction.     

基于 ADAMS 的推烟机构推手中曲柄滑块机构的动态研究

目的研究在理论条件下,推烟机构推手装置中曲柄滑块机构的动态运动情况。方法借助动力学分析软件ADAMS对曲柄滑块机构进行研究,分析其运动学曲线和动力学曲线。结果直观形象地仿真出了曲柄滑块的运动情况。结论通过对相同速度下推手中曲柄滑块的研究,获得了其位移、速度、加速度的曲线图,并研究了当曲柄受到临界载荷F=80 kN的阻力时,其驱动力矩的大小和方向的变化情况,最终获知当阻力改变方向时驱动力矩恰为0。