汽车悬架弹簧的CAE研究

根据国内某汽车生产厂对悬架弹簧提出的设计要求,对悬架弹簧的结构设计、材料选择、结构CAE(Computer Aided Engineering)分析进行研究,给出了F1-XXX车型弹簧结构的优化参数、选材,并且对结构进行仿真的CAE分析,表明选用55CrSi油淬火回火钢丝能满足该车型用簧的疲劳强度要求.     

汽车行李箱减压阀的设计及验证

介绍了减压阀的结构设计、布置思路和验证方法。结构设计方面对扇叶的厚度、本体的通过面积、密封条材质等因素进行分析,研究选用不同规格的扇叶、本体、密封条情况下,减压阀的排气量有何变化,并以实验数据图表进行说明,总结出如何设计减压阀的结构,另外还介绍了一种应用于恶劣环境下的双层扇叶结构,以及不同钣金开孔形式对减压阀安装的影响。布置思路方面提出减压阀的数量和位置应遵循便于排气和减小噪声两个原则。验证方法方面从实际应用的角度详细说明关门测试和道路试验的具体步骤,以及对应的指标要求。     

车灯塑件退火状态下应力松弛规律研究

针对注塑件中普遍存在残余应力这一问题,以材料为聚碳酸酯(PC)的车灯塑件为例,对注塑件在退火工艺下的应力松弛规律进行了研究,对工业玻璃在退火状态下的应力松弛计算公式进行了分析,提出了一种针对聚碳酸酯(PC)材料在退火状态下的应力松弛的数学模型。采取实验的方法,利用钻孔法对3种不同退火状态下得到的车灯塑件的残余应力进行了检测,根据其中测得的两组残余应力数据计算出了应力松弛数学模型中的待定参数,建立起了退火时间、退火温度、退火前残余应力以及退火后残余应力四者之间的关系,并将由该数学模型计算得到的残余应力与第3组测得的残余应力数据进行了对比。研究结果表明,通过由模型和实验得到的结果两者的误差非常小,因此说明该数学模型具有较高的可靠性与准确性。     

振动时效的机理工艺与设备

介绍振动时效技术的特点和机理 ,分析在振动时效工艺方案确定和参数选择等方面的有关问题。介绍国内外振动时效设备的基本情况     

Using stress relief grooves to reduce stress concentration on axle drive shaft

The axle drive shaft has important roles such as transferring power and changing the steering angle between the axle and the wheel in a power train system. It is used in most heavy construction machinery, where a high degree of reliability is required in the power train system. However, for axle drive shafts with a long span axle, failures are common at the snap ring cut that is machined on the drive shaft when there is significant fatigue damage under repeated loading conditions. Stress relief grooves have been applied at the snap ring cut to reduce the stress concentration and improve the fatigue life of an axle drive shaft. Although several studies have described how the stress concentration can be reduced by the stress relief grooves, details of the geometries of the stress relief grooves have been subject to debate and even controversy. We investigated the effects of the stress relief grooves on the stress concentration, and estimated the fatigue life of the drive shaft by using finite element analysis, taking into account the geometric parameters such as size and location of the stress relief grooves. As a result, the stress relief grooves presented by non-dimensional geometric parameters for an r/h = 1.2 and a d/b = 2.0 enabled a 22.3% reduction of the stress concentration, and a maximum improvement in the fatigue life that was approximately 3.3 times that of drive shaft with no stress relief grooves applied. These can be an index for selecting optimal geometric shapes of the stress relief grooves.     

Maximum principal tensile stress and fatigue crack origin for compression springs

Contrary to the traditional concepts, for helical compression springs with a large coil radius to wire radius ratio, the most highly stressed region is at the outer surface of the helix rather than inside. The likely fatigue crack origin is also located on the outer surface of the helix where the maximum amplitude of the principal tensile stress was calculated during cyclic loading. An equation is proposed for the maximum tensile stress from loading of a helical spring, and a method is presented to calculate the likely fatigue crack origin. It is demonstrated that for high-stressed springs, fatigue design should be based on the range of the maximum principal tensile stress. The influence of the shot peening on the location of the fatigue crack origin is also investigated.     

超声时效技术在微注塑模具制作中的应用

针对金属微注塑模具UV-LIGA制作过程中由于SU-8胶内应力过大而引起的胶膜破裂、变形甚至脱落等问题,提出将超声时效技术应用于微注塑模具的制作工艺.首先,利用紫外光刻工艺制备了电铸胶膜,在显影前使用自制的超声时效装置对胶膜进行超声处理.然后,采用无背板生长方法在38CrNiMnMo模具钢基底上直接进行镍金属的电铸生长,讨论并解决了工艺过程中遇到的SU-8胶浮胶变形、非圆形基片的匀胶、胶膜中的气泡以及微电铸层结合不牢等问题.最后,制作出微通道宽度和高度分别为80 μm和35 μm的微注塑模具.实验结果表明,超声时效技术的使用避免了由于SU-8胶内应力过大引起的破裂、变形甚至从基底脱落等缺陷,增强了UV-LIGA技术制作微注塑模具的能力,提高了制作微注塑模具的成功率.     

2D shape optimization of leaf-type crossed flexure pivot springs for minimum stress

Leaf-spring crossed flexure pivots are used in an increasingly large number of applications, many of which require the fatigue life and/or the rotational capability of the pivots to be maximized. Since these two qualities are determined by the endurance limit or the yield stress of the leaf-springs’ material, maximizing them will necessarily require reducing the stress levels arising in the aforementioned springs during operation. Partly for the sake of simplicity, partly due to manufacturing constraints, constant thickness leaf-springs have traditionally been used in crossed flexure pivots. However, minimizing stress simply by increasing the length or by decreasing the thickness of the leaf-springs is often not viable, either due to spatial constraints or to the attendant degradation in spring performance. This paper investigates the scope for stress reduction through shape optimization of the leaf-springs. To this end, a procedure combining a linear strain energy formulation, a parametric thickness profile definition and a series of optimization algorithms is employed. The resulting optimized thickness profiles are proven to be not only independent of the angular rotation at which the pivot operates, but also linearly scalable to leaf-springs of any length, minimum thickness and width. Validated using non-linear finite element analysis, the results show very significant reductions in relative maximum stress, of up to as much as 24% in the case of some pivot configurations. The optimized profiles and their corresponding constant thickness counterparts are also compared in terms of stiffness, strain energy and parasitic motion characteristics. It is concluded that shape optimization offers great potential for extending the fatigue life and/or rotational range of crossed flexure pivots.     

Magnetostriction varieties and stress relief caused by pulsed magnetic field

Magnetostriction is investigated to evaluate the stress relief caused by pulsed magnetic field treatment, because this physical property is closely associated with residual stress. Magnetostriction of different stressed samples is measured in this paper. The stress variations caused by pulsed magnetic treatment are also compared. It is found that magnetostriction variations are closely associated with stress changes. Thermodynamic potential is used to find the relationship between them. Based on several assumptions, we find that the product of magnetostriction amplitude and stress magnitude is nearly a constant during magnetic field treatment, which is valuable for stress relief evaluation and optimizing processing parameters. This conclusion is testified by stress measurements, and the calculated values are in accordance with the experiment results.     

基于VB和Matlab混编的振动时效系统研究

针对现有部分振动时效控制系统存在的灵活性差、自动化程度低等问题,对振动时效系统中的数据采集、激振电机控制、变频器控制等方面问题进行了研究,对频谱分析法判定工件固有频率的理论依据进行了推导。采用VB和Matlab混编构建了振动时效控制系统,结合数据采集卡、变频器和激振电机等,开发出了振动时效系统。设计了包括数据采集模块和激振电机模块等硬件系统以及包括人机交互界面、扫频模块、频谱分析模块和时效处理模块的控制系统。利用振动时效前后残余应力实测对比法,对振动时效效果进行了定量评定。研究结果表明,经过该系统处理的试件残余应力平均下降了46.62%,达到了振动时效消除残余应力标准,证明了系统的有效性;并且该系统开发周期短、自动化程度较高。     

Evaluating the effectiveness of vibratory stress relief by a modified hole-drilling method

In this paper, a modified through hole-drilling method is developed to evaluate the effectiveness of the application of vibratory stress relief (VSR). The principal residual stresses at any specified point before and after the treatment of VSR are measured by this method with the same cemented commercially available three-element strain gauge rosette. By comparing the magnitude of the measured results, the effectiveness of the treatment of VSR can thus be determined. Thin butt-welded specimens are prepared to verify the accuracy of the modified hole-drilling method compared to that of the conventional hole-drilling method. The experimental results show that the percentages of the relative errors between these two methods are all within 2.9%. Therefore, this modified method shows good accuracy in the determination of residual stresses before and after VSR. Meanwhile, the maximum principal residual stresses at the measured points are effectively reduced by about 5.8% to 27% after the application of VSR, and the minimum principal residual stresses at the measured points are effectively reduced by about 9.6% to 31%.     

基于VB编程的振动时效装置监控软件的开发

通过Visual Basic6.0编程开发振动时效装置的监控软件,详细说明了该系统开发的各个功能模块的实现过程.首先,介绍了振动时效处理装置的原理,基本工艺过程,系统设计基本参数指标.然后,开发了成套振动时效装置的监控软件具有智能化的功能.监控配套装置软件能够准确控制电机动作,实时采集到加速度值和频率值,并进行振动时效结果分析.开发软件还可以绘制直观明了的振动图形,很大程度上提高了振动时效结果分析处理的效率.     

基于MATLAB汽车发动机配气凸轮的型线设计与接触应力分析

在汽车发动机配气凸轮的型线设计过程中,通过选用合适型线函数,设定预期从动件运动边界条件,推导凸轮接触应力计算公式,进而通过MATLAB编程,可生成预设的从动件升程、速度、加速度和凸轮接触应力曲线。文中所涉及的MATLAB程序以期快速完成凸轮设计和分析凸轮接触应力为目的,应用此方法可显著提高配气凸轮设计的速度和精度,并为凸轮机构的优化提供理论依据。     

谈谈振动时效及其在衡器制造中的应用

介绍了振动时效的原理、发展,讨论了振动时效在衡器产品的秤体及传感器制造中的应用,指出振动时效可提高大型衡器机械部分的质量,降低或消除大型衡器秤体焊接加工中的残余应力,消除称重传感器弹性体机械加工应力,提高称重传感器的技术指标.     

A one-dimensional model for the prediction of residual stress and its relief in welded plates

The simulation of the welding process by means of continuum mechanics models has a very high cost both in input data preparation time and in computing time required for the integration of the complex thermoelastoplastic equations involved in solids with temperature dependent properties. For this reason, the plates in this study will be visualized as formed by a certain number of bars that can carry out elastoplastic behaviour and having temperature dependent properties. The thermal loads are simulated by analytical singular solutions, the thermomechanical problem being solved by means of an incremental algorithm of high efficiency. An excellent agreement has been found between the results numerically predicted and those previously obtained with an experimental technique and the Finite Element Method. Finally, the one-dimensional model developed here is used to predict the effects of a local heat treatment on the residual stresses originated by the welding. The versatility and rapidity of the use of this model makes it specially suitable to be used as a tool to select among different stress relieving procedures.     

On the compliance of coiled springs

The 6×6 spatial compliance matrix for a helical spring is computed. The method used is to find the compliance of infinitesimal elements along the length of the spring. Then integration is used to sum the compliances and produce the total compliance of the spring. A key point in the method is that the compliance matrix for each element must be expressed in a common coordinate frame. The results produced are significantly different from the those given in elementary texts. However, it is shown how these results can be recovered by making the standard “closely coiled” approximation. Next, the principal wrenches and eigencompliances of the spring are studied, both for the closely coiled spring and for the case where these assumptions are not made. Finally, some numerical examples are given.     

Folding and deployment of curved tape springs

This paper presents a study of a special type of tape springs, that are both longitudinally and transversely curved, as required for the ribs of a novel deployable reflector. It is shown that, although curved tape springs have much in common with straight tape springs, there is an important difference for equal-sense folds with small rotation angles. Thus, it is shown that full deployment of the reflector cannot be guaranteed if equal-sense folds are used when packaging it.     

On the large deformations of C-shaped springs

Large deflections of C-shaped springs are studied using the theory of the Elastica. The resulting nonlinear differential equation is integrated by a new homotopy method. It is found that the force-displacement curve is decidely nonlinear and depends heavily on the free shape of the spring. The maximum moment is also obtained.     

碟形弹簧的非线性稳定性分析

建立了碟形弹簧的单自由度保守系统的非线性振动控制方程，通过对其奇点性质的分析，研究了该系统的稳定性。研究表明，碟形弹簧属于物理非线性软弹簧；当弹簧极限行程与弹簧钢板厚度之比小于√2时，若该系统有一奇点，则该奇点是稳定的中心；当该比大于压时，碟形弹簧既具有稳定的中心，也具有不稳定的鞍点，从而为碟形弹簧的设计提供了理论依据。