Large Deformation Analysis and Synthesis of Elastic Closed-loop Mechanism Made of a Certain Spring Wire Described by Free Curves

Recently novel mechanisms with compact size and without many mechanical elements such as bearing are strongly required for medical devices such as surgical operation devices. This paper describes analysis and synthesis of elastic link mechanisms of a single spring beam which can be manufactured by NC coiling machines. These mechanisms are expected as disposable micro forceps. Smooth Curvature Model（SCM） with 3rd order Legendre polynomial curvature functions is applied to calculate large deformation of a curved cantilever beam by taking account of the balance between external and internal elastic forces and moments. SCM is then extended to analyze large deformation of a closed-loop curved elastic beam which is composed of multiple free curved beams. A closed-loop elastic link is divided into two free curved cantilever beams each of which is assumed as serially connected free curved cantilever beams described with SCM. The sets of coefficients of Legendre polynomials of SCM in all free curved cantilever beams are determined by taking account of the force and moment balance at connecting point where external input force is applied. The sets of coefficients of Legendre polynomials of a nonleaded closed-loop elastic link are optimized to design a link mechanism which can generate specified output motion due to input force applied at the assumed dividing point. For example, two planar micro grippers with a single pulling input force are analyzed and designed. The elastic deformation analyzed with proposed method agrees very well with that calculated with FEM. The designed micro gripper can generate the desired pinching motion. The proposed method can contribute to design compact and simple elastic mechanisms without high calculation costs.

Static-deformation based fault diagnosis for damping spring of large vibrating screen

Based on the statics theory, a novel and feasible twice-suspended-mass method(TSMM) was proposed to deal with the seldom-studied issue of fault diagnosis for damping springs of large vibrating screen(LVS). With the static balance characteristic of the screen body/surface as well as the deformation compatibility relation of springs considered, static model of the screen surface under a certain load was established to calculate compression deformation of each spring. Accuracy of the model was validated by both an experiment based on the suspended mass method and the properties of the 3D deformation space in a numerical simulation. Furthermore, by adopting the Taylor formula and the control variate method, quantitative relationship between the change of damping spring deformation and the change of spring stiffness, defined as the deformation sensitive coefficient(DSC), was derived mathematically, from which principle of the TSMM for spring fault diagnosis is clarified. In the end, an experiment was carried out and results show that the TSMM is applicable for diagnosing the fault of single spring in a LVS.

考虑环间接头影响的盾构隧道纵向变形简化解

为反映外荷载下盾构隧道相邻环间张开和错台,提出考虑环间接头影响的盾构隧道纵向变形简化解答。首先,引入纵向梁-弹簧模型模拟盾构隧道纵向受力变形,其中采用Timoshenko短梁考虑隧道环段变形,引入转动和剪切弹簧分别模拟环间接头转动与错台。其次,构建弹性地基上纵向梁-弹簧模型的有限差分方程,以解决环间接头-管环非连续变形求解问题,并推导外荷载下既有盾构隧道的纵向变形公式。最后,建立新建隧道上穿和下穿引起既有盾构隧道的纵向变形解答,并与新建隧道上、下穿越工程案例及现有理论方法对比验证。研究结果表明:所提方法预测的隧道位移与Timoshenko连续梁模型,协同变形模型和实测数据均具有较好的一致性,但所提方法得到的环间错台略低于Timoshenko梁模型和协同变形模型;所提方法可考虑环间接头的影响,得到的隧道位移曲线呈现既不光滑也不连续的特征,其中环段变形以刚体位移为主,而环间接头主要发生转动和错台;而基于现有理论所得盾构隧道纵向位移均为连续曲线,无法反映环间接头的真实转动与错台位移。

退火和变形温度对Ti-Ni-Cr形状记忆合金弹簧低温超弹性的影响

利用拉伸试验研究了350~800℃退火态Ti-50.8Ni-0.3Cr合金弹簧在-20~20℃温度范围变形时的低温超弹性。结果表明,在350~800℃温度范围退火时,随退火温度升高,该合金弹簧对外输出应力先降低再升高,而后趋于稳定。在-20~20℃温度范围变形时,随变形温度升高,该合金弹簧对外输出应力增大。要使该合金弹簧在-20℃下获得残余应变较小的超弹性,可对其进行350~400℃或550~800℃退火处理;要使该合金弹簧在-10~20℃下获得残余应变较小的超弹性,可对其进行350~500℃退火处理;要使该合金弹簧在-20~20℃下获得较大的能耗,可对其进行450~800℃退火处理。随退火温度升高,该合金弹簧的应变恢复率降低;随应力-应变循环次数增加,该合金弹簧的应变恢复率先降低后趋于稳定。预循环训练能明显提高该合金弹簧应变恢复率的稳定性。

圆弧叶形弹簧的大变形分析

目的通过对圆弧叶形弹簧缓冲器非线性大变形特性的研究,为其缓冲设计与应用提供理论参考。方法基于Euler-Bernoulli梁理论,以叶形弹簧的初始圆弧半径及截面角为基本参数推导弹簧的大变形控制方程,考虑压板作用下弹簧的多种变形情况给出圆弧叶形弹簧变形的边界条件,进而利用两点边值问题的数值解法计算不同顶角的叶形弹簧在外力作用下的变形情况。结果理论计算结果与数值解高度吻合,表明了计算方法的可靠性,计算得到了不同压力下叶形弹簧变形后的位形图及弹簧的非线性力-变形曲线。结论所讨论的叶形弹簧具有明显的非线性大变形特性和良好的减震及缓冲吸能特性,能够较好地替代传统缓冲材料用于运输系统的缓冲设计。

自复位复合阻尼耗能支撑滞回性能研究

为解决自复位支撑耗能能力不足且来源单一、耗能材料成本高昂的问题,提出了一种新型自复位复合阻尼耗能支撑。支撑由金属屈服阻尼装置、黏弹阻尼装置并联预压碟簧自复位装置组成。对其基本构造和工作原理进行阐述,通过精细化模拟研究了支撑的耗能、复位、承载和变形能力。结果表明,在往复荷载作用下,支撑的滞回响应具有稳定饱满的旗形特征,拉压对称、无残余变形,能够兼顾不同加载频率下的性能需求。揭示了支撑加载制度和设计参数对其滞回性能的影响规律,结果表明:加载频率从0.3 Hz增加到2.0 Hz,黏弹阻尼装置提供的阻尼力增大,支撑耗能量由8.32 kJ增加到11.93 kJ;随着碟簧预压力的增加,支撑激活力从378.98 kN增加到562.67 kN,复位性能始终得到充分发挥;支撑耗能能力主要受三角形钢板个数和黏弹材料剪切面面积影响,增加4个三角形钢板或将黏弹材料剪切面面积从140 mm×140 mm增加到300 mm×140 mm,支撑的等效黏滞阻尼比分别同比增长39.93%和16.09%。

组合碟簧自复位防屈曲支撑滞回性能试验

为控制防屈曲支撑(BRB)的残余变形,采用碟簧自复位系统(DS)和BRB并联形成自复位防屈曲支撑(SBRB)。通过拟静力试验考察组合碟簧刚度、端部连接、复位比率等对SBRB滞回性能的影响。结果表明:与BRB相比,SBRB的残余变形大幅降低;SBRB表现出旗型的滞回曲线,试验后期钢板支撑受拉断裂,其他部件保持完好;SBRB试件中DS部分和BRB部分分别是承载力和累积耗能的主要来源;由于组合碟簧间的摩擦等作用,DS部分的耗能占整个SBRB耗能的23%~36%;其他构造相同时,采用组合碟簧刚度较大的DS部分启动后承载力增幅较多,且DS部分启动力较大的复位比率也较大,残余变形更小。总体上,端部连接形式对残余变形影响不大,刚接SBRB试件因承受额外的端部弯矩,钢板支撑断裂更早,铰接SBRB试件表现出更好的耗能能力。随复位比率增大,SBRB的残余变形逐渐减小,为有效地控制支撑残余变形,同时避免对DS部分要求过高,复位比率宜取0.7~0.9。

温度场下功能梯度圆锥壳-环板振动特性分析

针对功能梯度圆锥壳-环板组合结构振动问题,本文采用一阶剪切变形理论和Rayleigh-Ritz法分析了温度场下组合结构的振动特性。组合结构位移变量采用谱几何法来表征,考虑材料参数与温度相关并引入人工边界弹簧建立了组合结构振动特性分析模型。数值算例中,通过将文中求解结果与文献解和有限元法结果进行对比验证了模型的正确性,进而分析尺寸、材料、温度和连接位置等参数对结构振动特性的影响。研究结果表明:组合结构基频随厚度增加而增加,随着幂律指数、半顶角和温度场参数增加而降低,随环板内径和连接位置变化会呈现非单一变化趋势。

基于质点弹簧模型和骨架球模型的虚拟肾脏建模

针对软组织建模中的几何剖分、物理建模和数值解算方法选择等关键问题,在软组织的几何剖分中采用德劳内法,提出了质点-弹簧模型和骨架球模型相结合的方法,解决了单一质点-弹簧模型形变仿真效果不佳问题。通过对比各数值分析方法选择改进显示欧拉法完成对虚拟肾脏物理模型运动学方程的数值求解,并提出对于虚拟软组织模型运动形变区域的确定与限定方法,提升了虚拟手术系统的图像刷新率与力反馈刷新率。

车桥耦合系统结构初始变形伪惯性力模型研究

以往车桥耦合动力分析中不考虑结构初始变形与轨道不平顺两者的差异。研究将高速铁路轨道-桥梁结构初始变形与轨道不平顺分开考虑,提出伪惯性力结构初始变形影响分析新模型,采用经典的Hertz弹簧-质量车辆模型,理论推导了车桥动力方程及轮轨力解析式,以高速铁路简支梁为对象,通过MATLAB自编程序,系统开展了车速及接触刚度影响分析。研究表明:整体上,轮轨力响应较车体加速度、桥梁位移响应对初始变形更敏感,Hertz弹簧刚度对轮轨力的影响要大于车速的影响;将初始变形作为附加轨道不平顺线性叠加模型受Hertz弹簧刚度影响大,伪惯性力模型受车速影响大;线性叠加模型高估了结构初始变形对车桥系统动力响应的影响。该研究可为我国即将到来的高速列车-轨道-桥梁系统大批量运维养护潮,提供更精细准确的模拟方法。

圆弧形蜂窝夹芯板在低速冲击下的动力响应研究

为了研究具有负泊松比特性的圆弧形蜂窝夹芯板的动力响应,基于哈密顿原理和一阶剪切变形理论推导了圆弧形蜂窝夹芯板的运动方程,同时建立两自由度的质量-弹簧模型来获得蜂窝夹芯板与冲击器之间的接触力,利用Navier法和Duhamel积分对圆弧形夹芯板的运动方程解析求解。在理论模型有效性验证方面,低速冲击下蜂窝夹芯板中心最大横向位移的理论模型计算结果与ABAQUS有限元仿真结果的最大相对误差为4.9%,同时求得理论模型与已发表文献计算出的接触力最大相对误差为8%,验证了理论模型的有效性。通过理论模型研究了蜂窝胞元参数变化对蜂窝夹芯板动力响应的影响,研究结果表明:随着球形冲击器的冲击速度递增,圆弧形蜂窝夹芯板中心最大横向位移也呈现出递增的规律;圆弧形蜂窝夹芯板的抗冲击特性随着蜂窝胞元半径或角度的增大而减小,当蜂窝胞元半径从5 mm增加至7 mm时,蜂窝夹芯板的抗冲击特性减少40.28%;当蜂窝胞元角度从30°增加至60°时,蜂窝夹芯板的抗冲击特性减少83.64%;蜂窝夹芯板的抗冲击特性随着蜂窝胞元壁厚的增大而增大,当蜂窝胞元壁厚从1 mm增加至3 mm时,蜂窝夹芯板的抗冲击特性提升59.51%。通过减小胞元角度和半径,增加胞元壁厚可以提升圆弧形蜂窝夹芯板的抗冲击特性。

一种新型沙漏式橡胶辅助弹簧的设计

轨道车辆对空气弹簧的横向变形能力以及无气下的垂向刚度要求越来越高,这对空气弹簧的辅助弹簧提出了更高的设计要求。通过总结现有轨道车辆中不同类型的橡胶辅助弹簧,对比分析其优缺点。并针对轨道交通更高的舒适性、轻量化要求,创新地设计了一种新型沙漏式橡胶辅助弹簧,既可以通过上盖接触曲面与橡胶接触形成非线性,又通过设计隔板分隔橡胶,使上下部分橡胶分别承担旋转和横向变形,从结构上解决了现有橡胶辅助弹簧横向变形能力不足的难题。通过对该产品进行有限元计算、试制试验和实际应用证明,新型沙漏式橡胶辅助弹簧可以提供较小的垂向刚度和较强的横向变形能力,并且具有重量轻、成本低和工艺简单等诸多优点,可以有效提升轨道车辆无气状态下的安全性和舒适性。

基于DEFORM-3D的高压断路器操作弹簧应力分析

采用有限元分析软件DEFORM-3D,分析了某型号的高压断路器操作弹簧在不同拉伸变形量下的应力变化和应力的分布,同时将模拟值与理论计算值进行了对比分析。分析结果显示:随拉伸变形量的逐渐增大,弹簧所受的载荷呈线性增长;操作弹簧内侧所受应力值大于外侧,在中径处应力值最小,内径处应力值最大。在拉伸行程达100 mm时,操作弹簧未失效,有限元模拟值与理论计算值相符合。

Universal scaling law of an origami paper spring

This letter solves an open question of origami paper spring risen by Yoneda et al.(Phys.Rev.E 2019).By using both dimensional analysis and data fitting,an universal scaling law of a paper spring is formulated.The scaling law shows that origami spring force obeys power square law of spring extension,however strong nonlinear to the total twist angle.The study has also successfully generalized the scaling law from the Poisson ratio 0.3 to an arbitrary Poisson's ratio with the help of dimensional analysis.

Method for secondary spring load equalization of railway vehicles with two-stage spring suspension: Modeling and optimal regulation

To ensure running safety,the secondary spring loads of railway vehicles must be well equalized.Due to the coupling interactive effects of these hyper static suspended structures,the equalization adjustment through shimming procedure is quite complex.Therefore,an effective and reliable method in application is developed in this paper.Firstly,the best regulation of spring load is solved based on a mechanical model of the secondary suspension system,providing a target for actual adjustment.To reveal the relationship between secondary spring load distribution and shim quantity sequence,a forecasting model is constructed and then modified experimentally with consideration of car body’s elastic deformation.Further,a gradient-based algorithm with a momentum operation is proposed for the load optimization.Effectiveness of the whole method has been verified on a test rig.It is experimentally confirmed that this research provides an important basis for achieving an optimal regulation of spring load distribution for multiple types of railway vehicles.

The Application of Similarity Theory in Designing Large Deflection Buckling Spring-Piece

Large Deflection Buckling Spring-Piece (LDBSP) refers to the deformation of an end-fixed flat spring-piece under normal loadings. Plastic deformation usually appears in LDBSP.The static characteristic curve is very particular, because within its linear deflection region, the spring constant can be designed to be any value from minus to plus. With its obvious advantages of large liner deflection range, low spring constant, etc., the LDBSP has now been extensively applied to the exciting device, low-frequency shock absorbers and so on. The static characteristic curve of LDBSP belongs to the nonlinear problem of an arch with varying section. Therefore, it is difficult to obtain it theoretically. The formulae for designing LDBSP have not been set up yet. In this study,the authors apply similarity theory to analyze the liner deflection range A and the spring constant K, and derive the relationship of similarity criterion, finally obtain a set of formulae for designing LDBSP by model test and the least square method, which can be applied in engineering design.Through the research, it is proved that it is unnecessary to keep geometrical similarity of spring-piece shape. This fact extends the application scope of the formulae. The proposed formulae for designing LDBSP thereby can be applied for any dimensions within the range allowed.

A new model to describe effect of plastic deformation on elastic modulus of aluminum alloy

In order to improve the prediction capability of spring-back in aluminum sheet metal forming, the influence of the plastic deformation on elastic modulus is considered when the material undergoes a large plastic deformation. The present work focused on establishing a new model to accurately describe the relation of elastic modulus and plastic deformation. The tensile tests were performed to investigate the influence of plastic deformation on elastic modulus at low strain rate. Two different aluminum sheets were used, AA2024-T3 and LY12-CZ, and the thickness of sheet metals was 1.3 mm and 2.0 mm, respectively. In order to overcome the drawback, which is directly measuring the slope of tension curve to obtain elastic modulus, an extrapolation method was adopted. The proposal macroscopic piecewise sinusoidal function can accurately model the elastic modulus variation.

A Numerical Approach on Reduction of Young’s Modulus During Deformation of Sheet Metals

The paper investigates the elastic behavior of the metal after unloading. For this purpose the strip of metal with tensile gauge length was simulated with high and low strength material. Further the channel forming was modeled for combination of materials to predict the spring-back and compared the results. It is observed that the Young’s modulus (E-value) decreases with the increase in plastic strain. The strength of the material has no effect on the decrease in the E-value after unloading during tension test. However in channel forming the E-value after unloading depends on the starting E-value, spring-back angle and maximum strain achieved in the channel. The proposed mathematical equations to determine the E-value after unloading from the tension test and channel forming test gives very good prediction with each other. It is also found that the lowest spring-back occurred in the channel with the composite Hard-Soft material.

盾尾非对称推力作用下盾构隧道纵向变形分析

盾构机在沿曲线掘进或轴线纠偏过程中,盾尾非对称推力会在管片端部产生附加弯矩,从而引起隧道发生纵向变形。现有解析方法多是将盾构隧道简化为等效连续梁,不能考虑隧道管片环间接头的弱化。首先,建立一种能够同时考虑环间张开和剪切错台的简化纵向梁-弹簧盾构隧道模型(simplified longitudinal beam-spring shield tunnel model,简称SLBSM);其次,将在建隧道简化为Winkler地基上的SLBSM,采用状态空间法推导了非对称推力作用下盾构隧道纵向变形解析解答。通过与既有文献有限元及现有两种连续梁模型计算结果进行对比,验证了所提方法的可靠性和适用性,并对部分参数进行敏感性分析。研究结果表明:连续梁模型计算得到的隧道纵向位移表现为连续特征,而所提方法得到的隧道纵向位移表现为非连续特征,隧道纵向位移在接头处会发生突变;通过参数分析可知:增大接头转动刚度可有效降低隧道隆起和环间张开量;增大接头剪切刚度可有效降低环间错台量,但会导致隧道隆起和剪力的增加;增大地基刚度能显著降低隧道环间张开量和隆起,但会导致环间错台量的增加;管片始端轴力对隧道纵向变形的影响不可忽略,增大始端轴力能显著降低隧道隆起值、环间张开量和错台量。

52CrMoV4弹簧钢热变形行为的本构模型

基于导向臂用52CrMoV4弹簧钢的热锻及热压变形工艺研究,采用Gleeble-3500型热模拟实验机,在变形温度(1 173~1 373 K)和应变速率(0.01~10 s^(-1))下对52CrMoV4弹簧钢进行等温热压缩实验。基于实验所得真应力-真应变曲线,分析了热变形参数与流变应力之间的关系,建立了修正的Johnson-Cook本构模型和基于应变补偿的Arrhenius本构模型,并对两种本构模型的准确性和有效性进行了比较。结果表明,52CrMOV4弹簧钢的流变应力随着温度的升高和应变速率的降低而降低。通过精度分析可知,修正Johnson-Cook模型的相关系数为0.989 55,平均绝对相对误差为5.4625%,均方根误差为6.870 29 MPa,计算较为简单却具有较高的准确性。而应变补偿的Arrhenius模型的相关系数为0.990 23,平均绝对相对误差为4.4319%,均方根误差为6.226 64 MPa,其精度较修正Johnson-Cook模型更高,可以更 好地预测52CrMoV4弹簧钢的流变应力行为并作为热变形工艺及有限元模拟参数选择的依据。