Experimental Investigations of the Superelastic Impact Performance of Nitinol 60

Nitinol 60 (NiTi60) is a nickel–titanium alloy that has a unique combination of properties such as high hardness, low elastic modulus, and superelasticity. Recent studies of static indentation tests on prestressed samples demonstrated a considerable load capacity increase, which led to the current experimental work. The coefficient of restitution (COR) is measured for two NiTi60 spheres of different diameters (0.635 and 1.270 cm). This work shows that mechanically stressing NiTi60 spheres enables them to achieve a normal COR greater than 0.9 when colliding with NiTi60 landing. This is one of the highest ever reported COR values for self-mated crystalline metal alloys at moderate impact velocities. Consequently, it is believed that this material may be a potential candidate for use in applications requiring highly resilient and wear-resistant metallic materials. A well-known analytical formulation for the coefficient of restitution is used to gain insight and to elucidate some of the COR results presented.     

基于有限元分析的可调预压装置的研究

摩擦驱动系统中正压力的大小直接影响系统的位移分辨率,为了获得稳定的、连续可调的正压力,提出了一种新型的基于压电陶瓷驱动的柔性四杆型可调预压装置,可以得到(0～500)N的可计算机控制的正压力输出.并基于有限元分析的方法,系统地分析了铰链的各个几何参数对预压装置的静、动态特性的影响,对预压装置的设计参数进行了优化.     

基于LS-DYNA的电磁冲击器阀芯能量传递效率研究

阐述了电磁冲击器冲击时的能量转换过程,对电磁冲击器阀芯构建了有限元模型,并利用LS-DYNA软件对其冲击过程中阀芯的能量传递效率进行了研究,得出合理的结论,为以后冲击机械的设计开发和优化设计提供了可靠的依据。     

两颗粒弹塑性正碰撞的耗散模型

为了快速地得到颗粒碰撞后的运动状态,从而实现颗粒碰撞阻尼系统的整体仿真研究,建立颗粒在单个碰撞周期中的分段力学模型.该模型将颗粒的单个碰撞周期分为三个阶段,通过三个阶段的力学分析得出颗粒在关键节点的运动状态,最终得到颗粒碰撞后的反弹速度、碰撞过程中的恢复系数和能量损耗的解析表达式.随后采用有限元方法对两颗粒的弹塑性碰撞过程进行模拟,有限元分析结果与分段力学模型的结果吻合较好,证明了分段力学模型的正确性.最后应用此分段力学模型对颗粒的碰撞速度、颗粒材料参数包括屈服点、弹性模量、密度和颗粒大小对耗能效果的影响进行定量的分析计算.计算结果表明,材料的屈服点和弹性模量之比越小,碰撞耗能效果越好;同时,质量密度越大的材料,耗能效果也越好;在设计颗粒阻尼器时可以以此为原则选用碰撞伙伴的材质.以上研究结果可以用于颗粒碰撞阻尼系统的阻尼特性分析和整体仿真研究.     

斜齿轮传动中啮合冲击数值研究

斜齿轮传动是一种应用广泛的机械传动形式,其啮合过程中存在冲击现象。使用MSC．Nastran的非线性仿真(SOL600)功能建立了斜齿轮啮合三维接触有限元分析模型,计算出冲击激励。使用瞬态响应分析法得到了斜齿轮在啮合冲击激励下的动力学特性,为斜齿轮传动系统的优化设计提供参考。     

The response of viscoelastic-frictionless bodies under normal impact

This paper presents a computational finite element model capable of simulation of the impact response of viscoelastic-frictionless bodies. The variational method is developed to drive the equations of motion. The Lagrange multiplier method is exploited to impose the nonholmonic contact constraints and convert the problem form constraint problem to unconstraint one. The constitutive equations are expressed in integral form. and involving relaxation moduli are adopted to describe the nonaging simple material. Generalized Standard Linear Solid (Wiechert) model is adopted to simulate the internal damping (viscoelastic) behavior of the structure. Wiechert model is exploited in order to drive a recursive relationship and thereby eliminate storage problem. Newmark constant average acceleration is proposed to integrate the governing equation numerically and transfer the problem into a static one for each time increment.     

车体结构中圆管撞击吸能特性的有限元研究

运用非线性有限元理论建立了有限元分析模型,讨论了建模过程中的关键问题。结合复合材料的破坏理论研究了金属管、复合材料管(玻璃/环氧)、复合管(缠有玻璃增强环氧的金属圆柱管)在轴向撞击载荷下的能量吸收特性。并从金属材料和复合材料的破坏机理中分析了这3种圆柱管的吸能特性。仿真结果与实验结果基本一致,说明了该模型的正确性。本文的结果对车体结构中的碰撞吸能元件的设计提供了有价值的参考。     

Analytic and FE based estimations of the coefficient of friction of composite surfaces

In this work the coefficient of friction (COF) of a body with a composite surface layer (CSL) in sliding contact with a homogeneous counterbody is studied. With an analytic model the upper and lower bounds of the COF are estimated, whereas the material and surface properties of the CSL components are known and no information about their geometrical arrangement is at hand. An analogy with the Voigt and Reuss bounds is invoked. The analytic results are compared to FE computations. Additionally the influence of plastic deformation and geometric properties of the CSL are treated.     

The deflection coefficient of a rectangular plate reinforced in the middle

In this paper, we investigated the deflection coefficients of rectangular plates that are reinforced in the middle. For reinforced plates with three different aspect ratios and two types of boundary conditions (simply supported and clamped), we derived the deflection coefficients with respect to the elastic modulus ratio and the relative length of the inner plate using the least-squares method. We performed a finite element analysis of the models, and calculated the deflection coefficients of reinforced plates in terms of the deflection coefficients of simple (nonreinforced) plates. The results can be extended to various types of reinforced rectangular plates.     

基于行人保护的溃缩式前大灯设计研究

在轿车主动安全性设计中,行人和车相撞的过程中的头部保护是一个国内外研究的重点.越来越严格的汽车安全性法规对行人保护提出了更高的要求.针对基于行人保护的溃缩式的前大灯设计进行了研究,采用有限元分析的方法,对行人头部和前大灯撞击进行了仿真.结论是:溃缩式前大灯能够很好地减少头部的伤害值;并在某国产轿车品牌新车型自主开发中得到了成功的应用.