应用局部应力-应变法计算联轴器膜片疲劳寿命

由于轴线间的角向不对中,联轴器旋转时膜片中产生交变应力,引起疲劳问题。使用中需要考虑其疲劳寿命。本文对六孔圆环形和束腰形膜片,利用有限元方法和薄板弯曲理论建立膜片应力计算模型。引入改进的局部应力－应变法,建立计算膜片联轴器膜片疲劳裂纹形成寿命的模型和方法。定量分析两种形式膜片的应力、附加载荷和疲劳寿命,最后,得出对膜片组设计有参考价值的结论。结论表明,对于设计合理的膜片,其疲劳寿命能满足机组工作要求。     

汽车空调热力膨胀阀小型化感温元件中膜片结构优化

针对小型化感温元件中膜片行程不足的问题,采用有限元仿真软件Abaqus对不同结构模型开展计算,分析膜片行程及应力分布,研究结构变量对膜片行程的影响。结果表明:在膜片焊接位置均存在应力集中现象,相对于无波纹及三波纹膜片,单波纹和双波纹结构较为合理;膜片厚度、波纹半径及波纹突出距离是影响膜片行程的关键因素,波纹位置对膜片行程的影响较小;针对双波纹膜片,可采用增大外侧波纹半径的结构提升膜片行程。研究结果可为小型化感温元件中膜片的结构优化设计提供理论依据。     

基于灰色关联分析和响应面法的复合材料缠绕成型多目标工艺参数优化

针对复合材料预浸带缠绕过程中制品的残余应力、孔隙率最小化和层间剪切强度（ILSS）最大化的多目标优化问题,采用Box-Behnken Design （BBD）原理设计四因素三水平的T300/环氧树脂预浸带缠绕实验;基于灰色关联分析（GRA）将多目标优化问题转化为单目标优化问题,利用主成分分析（PCA）法确定残余应力、孔隙率和ILSS对灰色关联度（GRG）的影响权重;通过对实验数据的回归分析,建立GRG与主要缠绕工艺参数（缠绕温度、张力、压辊压力和缠绕速度）的二阶预测模型;分析了各工艺参数对残余应力、孔隙率、ILSS和GRG的影响规律,确定缠绕工艺参数优化方案;利用响应面法（RSM）求解工艺参数优化问题并进行复合材料预浸带缠绕实验。结果表明:该优化方法获得的最优工艺参数组合可以有效改善残余应力、孔隙率和ILSS,提高预浸带缠绕制品的性能。      

有限元仿真在硅-蓝宝石高温压力传感器双膜片设计上的应用

本文介绍了在硅-蓝宝石高温压力传感器设计中,运用E型膜片弹性变形原理和传感器压阻效原理,对双E型膜片进行设计,为满足研制实际需求,采用ANSYS M echan ical模块对双膜片力学模型仿真分析,绘出膜片径向应力切向应力的线性分布,合理构建膜片结构的相关参数,将压阻元件布局在应力分布的最佳区域上,研制的传感器满量程输出≥100mV,线性度提高为≤0.01%,传感器精度0.1%。     

电磁喇叭分段线性振动响应及其声学特性的研究

根据电磁喇叭结构特征建立了其工作过程中时变电磁力激励条件下动铁心与膜片构成的分段线性振子动力学模型,应用数值积分方法分析了电磁喇叭振动响应特性。进而根据所得到的稳态振动幅值与频率结果仿真分析了电磁喇叭的声学特性,研究了触头初始压力及间隙参数对振动幅值、频率、声压级的影响规律,所得的结论可直接用于以电磁喇叭为代表的电声器件优化设计。     

隔膜压缩机膜片破裂理论分析

隔膜压缩机膜片裂纹通常产生在支板最外圈环槽边沿及中间处,且裂纹呈周向分布,因此径向应力过大是导致膜片破裂的主要原因。隔膜压缩机中柱塞泵不稳定工作会导致油缸内油量不足,在此情况下当活塞运动到下止点时膜片会紧贴支板,环槽处膜片承受贴合支板引起的大挠度变形径向应力及环槽处附加变形引起的小挠度变形径向应力。该文利用薄板大挠度及小挠度理论对两种应力进行了求解,计算结果表明:当进气压力为1.7MPa,最外圈环槽两边沿处及中间处膜片总径向应力为272.6MPa、275.7MPa、220.4MPa,大于膜片许用径向应力170MPa,其中小挠度变形径向应力为140.1MPa、138.2MPa、107.4MPa,因此附加变形对膜片寿命影响很大。     

铍青铜膜片的分级时效

本文根据铍青铜时效变形规律,对QBe1.9合金膜片的分级时效工艺进行了研究。采用该工艺能有效地降低残余应力对时效变形的影响,保证膜片形面与时效夹具更贴合,获得一致性更高的膜片形面尺寸。此工艺提高了产品合格率。     

表面离化微热板的结构设计和优化

对微热板温度、应力的分布以及功耗等情况的了解有利于微热板的优化设计，从而设计出性能符合要求的表面离化微热板．为此，用有限元方法对膜片型及梁支型微热板的温度和应力分布以及形变进行了模拟分析．结果表明：梁支型微热板不仅温度分布均匀，而且机械稳定性好，但是功耗较大；通过加热面积和梁长等结构尺寸的优化，可以有效降低功耗，同时能满足表面离化源对离化面积的要求．因此，梁支型微热板比膜片型微热板更适用于表面离化．     

铝硅双金属驱动膜片形变方向控制及其结构参数的优化

对三种典型的铝硅双金属驱动膜片结构进行了有限元分析，结果表明，铝硅双金属驱动膜片的结构参数与驱动膜片的弯曲变形方向，中心最大挠度和有效形变体积具有紧密的联系，通过不同的结构设计可以控制驱动膜片结构的弯曲变形方向，另外，通过结构参数优化，可使驱动膜片的中心最大挠度和有效形变体积达到最大值，驱动膜片的性能得到显著提高。     

基于神经网络焊接数值模拟研究及工艺参数优化

在有限元分析的基础上,利用RBF神经网络针对汽车后桥壳焊接过程中的工艺问题及焊接残余应力的影响进行了研究,利用正交试验找出焊接工艺参数的主要因素,利用MATLAB软件提供的径向基函数工具箱设计神经网络训练样本,采用有限元分析软件ANSYS对汽车后桥壳体焊接过程进行了模拟分析,分析结果与神经网络预测结果进行比较,得到不同焊接工艺参数组合下的最大残余应力值,获得提高焊接质量的优化焊接工艺参数．     

Failure analysis of an automobile damper spring tower

The cause of a passenger car’s damper spring tower early failure is investigated in this paper. Inspection of the road surface, tire inflation pressure, suspension, and service load are firstly done in order to determine the further test procedures and analysis methods. The static stress of the spring tower caused by the body weight is calculated by finite element model. Public road tests with an equipped car are carried out to simulate the real usage by the customers. With the measured strain signals of different test conditions and local strain–life method, fatigue life prediction is made. The calculated fatigue life coincides with the actual failure mileage, and it turns out that the broken spring damper causes the early failure of the spring tower. It is suggested that more emphasis should be taken on the durability design and test of the spring damper.     

多重四边形环索-张弦穹顶局部断索冲击分析

多重环索-张弦组合屋盖为复杂的弦支穹顶结构。任一拉索瞬断均会对屋盖结构产生十分显著的动力冲击作用。针对多重环索-张弦穹顶屋盖的结构特点,提出基于AP法的断索冲击动力分析方法。针对断索失效路径、断索持续时间、结构阻尼比及屋盖初始荷载等参数开展敏感性分析,得到适用于多重环索-张弦屋盖的断索冲击动力分析的适用参数。剩余屋盖结构的动力分析结果表明:拉索瞬断冲击下,剩余屋盖的位移及内力响应均会不同程度地大于拉索静力失效,拉索瞬断引起的冲击效应不可忽视。而且,部分结构响应的动力放大系数会大显著大于规范所推荐的放大系数DAF=2.0。不同类型的拉索瞬断分析结果表明:同一重环索中任一拉索瞬断引起的动力效应大致相同;外环索瞬断引起的动力效应会显著大于其他拉索;虽然外环索和张弦索的瞬断均会引起较大的动力响应,但是两者的分布规律差异较大;多根拉索瞬断引起的动力响应并非总是大于单根拉索瞬断。     

Stress-Based Uniaxial Fatigue Analysis Using Methods Described in FKM-Guideline

The process of prevention of failure from structural fatigue is a process that should take place during the early development and design phases of a structure. In the ground vehicle industry, for example, the durability specifications of a new product are directly interweaved with the desired performance characteristics, materials selection, manufacturing methods, and safety characteristics of the vehicle. In the field of fatigue and durability analysis of materials, three main techniques have emerged: nominal stress-based analysis, local strain-based analysis, and fracture mechanics analysis. Each of these methods has their own strengths and domain of applicability??for example, if an initial crack or flaw size is known to exist in a structure, a fracture mechanics approach can give a meaningful estimate of the number of cycles it takes to propagate the initial flaw to failure. The development of the local strain-based fatigue analysis approach has been used to great success in the automotive industry, particularly for the analysis of measured strain time histories gathered during proving ground testing or customer usage. However, the strain life approach is dependent on specific material properties data and the ability to measure (or calculate) a local strain history. Historically, the stress-based fatigue analysis approach was developed first??and is sometimes considered an ??old?? approach??but the stress-based fatigue analysis methods have been continued to be developed. The major strengths of this approach include the ability to give both quantitative and qualitative estimates of fatigue life with minimal estimates on stress levels and material properties, thus making the stress-based approach very relevant in the early design phase of structures where uncertainties regarding material selection, manufacturing processes, and final design specifications may cause numerous design iterations. This article explains the FKM-Guideline approach to stress-based uniaxial fatigue analysis. The Forschungskuratorium Maschinenbau (FKM) was developed in 1994 in Germany and has since continued to be updated. The guideline was developed for the use of the mechanical engineering community involved in the design of machine components, welded joints, and related areas. It is our desire to make the failure prevention and design community aware of these guidelines through a thorough explanation of the method and the application of the method to detailed examples.     

基于FVM数值分析的海工混凝土结构耐久可靠度Monte Carlo模拟

为研究海工混凝土结构耐久性设计及寿命预测的可靠度方法,分析了耐久性设计与寿命预测的半理论、半经验解析模型方法,讨论了截面形状等条件对氯离子扩散传输的影响。该文研究应用有限体积法(FVM)分析求解混凝土中氯离子含量和蒙特卡罗(Monte Carlo)模拟求解耐久失效概率,分析海工混凝土结构耐久可靠度。这种方法可简称FVM-MC方法。在FVM-MC方法中,首先采用FVM方法求解混凝土中的氯离子含量,然后采用Monte Carlo方法对失效概率进行模拟求解。验证分析表明,FVM-MC方法分析模拟精度高,是海工混凝土结构可靠度分析的一种可靠方法。计算结果表明,截面形状等对混凝土结构的耐久可靠度具有显著的影响,采用Fick第二定律解析解的半理论、半经验模型,由于没有考虑截面形状效应,增加了矩形截面构件的耐久失效风险;圆形截面具有近似一维的扩散传输特点,在条件相同情况下,其构件耐久可靠度显著地高于方形或矩形截面的构件。     

Design and failure modes of automotive suspension springs

This paper is a discussion about automotive suspension coil springs, their fundamental stress distribution, materials characteristic, manufacturing and common failures. An in depth discussion on the parameters influencing the quality of coil springs is also presented.

Following the trend of the auto industry to continuously achieve weight reduction, coil springs are not exempt. A consequence of the weight reduction effort is the need to employ spring materials with significantly larger stresses compared to similar designs decades ago. Utilizing a higher strength of steel possesses both advantages and disadvantages. The advantages include the freedom to design coil springs at higher levels of stress and more complex stresses. Disadvantages of employing materials with higher levels of stress come from the stresses themselves. A coil’s failure to perform its function properly can be more catastrophic than if the coil springs are used in lower stress. As the stress level is increased, material and manufacturing quality becomes more critical. Material cleanliness that was not a major issue decades ago now becomes significant. Decarburization that was not a major issue in the past now becomes essential.

To assure that a coil spring serves its design, failure analysis of broken coil springs is valuable both for the short and long term agenda of car manufacturer and parts suppliers. This paper discusses several case studies of suspension spring failures. The failures presented range from the very basic including insufficient load carrying capacity, raw material defects such as excessive inclusion levels, and manufacturing defects such as delayed quench cracking, to failures due to complex stress usage and chemically induced failure. FEA of stress distributions around typical failure initiation sites are also presented.     

Optimization of a crankshaft rolling process for durability

A crankshaft is often designed with a small fillet radius. The crankshaft fillet rolling process is one of the commonly adopted methods in engineering to improve fatigue life of the crankshaft. Compressive residual stresses on and below the fillet radius surface are induced through the fillet rolling operation. Consequently, fatigue life of the crankshaft is improved. An analytical technique is used to optimize the crankshaft rolling process to comply with a crankshaft design criterion for durability. A nonlinear finite element analysis is implemented to approximate the stress distributions induced by the crankshaft rolling process, and a crack modeling technique is developed to calculate the equivalent stress intensity factor ranges based on the combined residual and operational stress distributions along various crack growth planes. The threshold equivalent stress intensity factor range is obtained from previous staircase testing on crankshaft sections. The durability design criterion is met if the threshold equivalent stress intensity factor range exceeds the largest calculated equivalent stress intensity factor range. Due to the complexity of the modeling techniques in simulating the rolling process and calculating the equivalent stress intensity factors, a meta-model is generated based on the uniform design method for the choice of sample points and the quadratic polynomial fitting technique for a response surface generation. In the meta-model optimization process, rolling force, rolling angle, and fillet radius are the control factors, while the variations of the threshold equivalent stress intensity factor range, rolling force, rolling angle, and fillet radius are considered as the noise factors. By using the Hooke–Jeeves direct pattern search method and the Monte Carlo simulation technique, the optimal design is obtained for the highest reliability and the smallest coefficient of variation (COV).     

面向软磁铁氧体去毛刺的超声波变幅杆设计

为了去除软磁铁氧体毛刺且不损伤工件,设计了一种复合高斯变幅杆。介绍了超声波去毛刺的原理。将超声波去毛刺的振动过程近似为由两根劲度系数不同的弹簧组成的质点弹簧系统受迫振动模型,得到毛刺断裂条件,以此计算复合高斯变幅杆的最小放大倍数,经理论计算,在满足最小放大倍数的条件下,高斯变幅杆的形状因数比指数杆高40%,大大改善应力集中问题。最后,通过有限元分析验证了上述设计过程的正确性。     

Modeling analysis and fabrication of MEMS capacitive differential pressure sensor for altimeter application

This paper proposes the modeling analysis of MEMS highly sensitive Capacitive Differential Pressure Sensor (CDPS) and also the development of a fabrication process for CDPS structures for aircraft altimeter applications. Highly sensitive CDPS structure models using circular and square sandwich polyimide diaphragm membranes, with and without center boss, were adopted, whereas other studies report on silicon diaphragms. CDPS characterization was carried out to analyze the deflection sensitivity, capacitive sensitivity, stress on diaphragm membrane and the effect of temperature on capacitive sensitivity. Simulation results of square diaphragm without center boss show better characteristics than other proposed diaphragm structures. This design yields 145.8 nm/mbar and 0.574 fF/mbar of deflection and capacitive sensitivity, respectively. The maximum stress developed on the diaphragm at maximum working pressure is less than the yield stress of polyimide material by a factor of 1.77 and capacitive sensitivity deviates at ±0.00195%/°C. From the modeling analysis, square diaphragm CDPS structure yields better characteristics and hence the fabrication process for CDPS has been developed, and its fabrication process flow verified using Intellisuit virtual fab tool.     

On the Problems of Cracking and the Question of Structural Integrity of Engineering Composite Materials

Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large engineering structures. Where human life depends upon engineering ingenuity, the burden of testing to prove a “fracture safe design” is immense. For example, when human life depends upon structural integrity as an essential design requirement, it takes ten thousand material test coupons per composite laminate configuration to evaluate an airframe plus loading to ultimate failure tails, wing boxes, and fuselages to achieve a commercial aircraft airworthiness certification. Fitness considerations for long-life implementation of aerospace composites include understanding phenomena such as impact, fatigue, creep, and stress corrosion cracking that affect reliability, life expectancy, and durability of structure. Structural integrity analysis treats the design, the materials used, and figures out how best components and parts can be joined. Furthermore, SI takes into account service duty. However, there are conflicting aims in the complete design process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk.