简支梁金属橡胶本构模型

依据金属橡胶细观接触作用特点及受力变形特征为基础,对金属橡胶准静态压缩情况进行分析.从金属橡胶的微单元体出发,以单匝螺旋卷为基本受力单元,根据单匝螺旋卷与简支梁的几何关系,及单元体内螺旋卷的串并联关系,提出了简支梁金属橡胶本构模型,并用不同工艺参数的金属橡胶试件对所建模型进行试验验证,同时与悬臂梁模型、多孔模型作误差对...     

金属橡胶恢复力的迟滞模型研究

依据金属橡胶变形的主要特征,对金属丝螺旋卷的空间位形、接触模式进行了分析。提出了基于变长度曲梁的细观结构单元和接触作用模型,考虑摩擦接触点分布规律,建立了金属橡胶恢复力的迟滞模型,实现了金属橡胶在不同变形幅值下的加卸载恢复力的预测。通过不同相对密度的金属橡胶试件对所建模型进行了试验验证,发现理论计算结果和试验结果有较好的一致性。     

金属橡胶非成形方向迟滞特性力学模型研究

金属橡胶是一种各向异性材料,其非成形方向与成形方向的力学特性存在显著不同。依据金属橡胶非成形方向变形的主要特征,对金属丝螺旋卷的空间位形、接触模式进行分析,揭示金属橡胶非成形方向变形的细观物理机制。结合螺旋卷的弹性变形特征和金属橡胶内部摩擦力接触点分布规律,建立金属橡胶非成形方向的力学模型,实现不同预变形下金属橡胶加载和卸载过程迟滞力学特性的预测。该模型包含金属丝直径和弹性模量、螺旋卷直径、材料相对密度等基本的材料结构参数,从理论上解释金属橡胶非成形方向的弹性特性和多点接触的干摩擦特性产生的机理。通过不同相对密度的金属橡胶试件对所建模型进行试验验证,发现理论计算和试验结果有较好的一致性,为分析和预测金属橡胶非成形方向的刚度和阻尼提供理论依据。     

金属橡胶减振器随机振动有限元仿真

提出一种金属橡胶减振器随机振动有限元仿真方法,采用正交各向异性阻尼材料模拟金属橡胶材料。相关仿真参数由金属橡胶减振器正弦扫频试验确定。对金属橡胶减振器进行正弦扫频试验和随机振动试验,利用有限元仿真软件ANSYS Workbench对金属橡胶减振器随机振动进行有限元仿真模拟,并将仿真结果与试验结果进行对比分析。研究结果表明,所提出的有限元仿真方法能够很好地对金属橡胶减振器随机振动进行仿真,且计算结果具有较高精度。     

金属橡胶与弹簧组合型隔振器动静态性能的分析

研究了金属橡胶与弹簧组合型隔振器的刚度和阻尼性能与弹簧的刚度，金属橡胶元件的相对密度，以及金属橡胶元件的成形工艺之间的关系，建立了单向载荷作用下金属橡胶与弹簧组合型隔振器的能量耗散系数与阻尼系数之间的关系。分析了载荷作用次数及振动频率对隔振器性能的影响，提出了提高其寿命的方法。     

金属橡胶构件的性能分析与实验研究

利用金属橡胶的弹性性能,设计了一种以金属橡胶作为阻尼元件的隔振器,对其进行了理论分析和静态实验研究,通过实验获得了金属橡胶隔振器刚度,密度及振幅之间的相互关系,并利用Masing理论,建立了金属橡胶隔振器数学模型,利用数学模型对实验结果进行了验证,为金属橡胶隔振器的应用提供了理论依据。     

金属橡胶阴尼元件减振性能的试验研究

对金属橡胶阻尼元件的减振性能进行了试验研究,并进行了机理分析。     

环形金属橡胶的径向压缩性能及力学模型分析

采用试验的方法分析了密度、金属丝直径、螺旋卷直径及温度对环形金属橡胶径向刚度的影响,以悬臂曲梁为基本单元,分析了金属橡胶的受力变形情况,结合温度对金属丝弹性模量及接触曲梁的影响,建立了包含主要制备参数及温度影响的金属橡胶径向力学模型。同时,依据试验结果,对力学模型的参数进行拟合求解,确定了模型的具体表达式。通过将模型计算结果与试验结果对比后发现,力学模型有较高的精度,可以比较全面地反映环形金属橡胶的径向刚度特性,为金属橡胶的实际应用提供了理论参考。     

金属橡胶干摩擦阻尼系统动态性能分析方法的研究

以干摩擦阻尼系统动态性能表征方法的前期研究成果为基础，针对金属橡胶构件的非线性力学性能，分析了金属橡胶构件的干摩擦阻尼的成因，对金属橡胶干摩擦隔振系统的运动微分方程的建立与求解进行了探讨，将方程的数值解与试验结果进行了对比。结果表明，在建立金属橡胶干摩擦阻尼系统的运动微分方程时，可以直接采用非线性恢复力，而不采用当量粘性阻尼项。试验结果表明该方法具有足够的精度。     

金属橡胶材料干摩擦阻尼的产生机理及力学模型

金属橡胶材料干摩擦阻尼、非线性刚度的产生机理是一个较为复杂的问题,其内部存在大量的干摩擦接触,通过螺旋型金属丝相互摩擦接触来损耗振动能量。干摩擦阻尼与物体表面的微观结构密切相关,从微观角度分析了金属橡胶材料干摩擦阻尼的产生机理,欲准确地揭示干摩擦阻尼的减振规律,还必须正确的提出描述干摩擦规律的数学模型。由于金属橡胶客观存在不光滑的非线性泛函本构关系,使得含有干摩擦环节的金属橡胶结构的响应计算问题非常困难。介绍了关于两固体接触表面间的干摩擦问题的四种数学模型,即Sgn摩擦模型、滞迟模型、动态系统中干摩擦力的数值计算模型、三次非线性粘性阻尼双线性滞迟模型,这四种模型为后人在该领域的继续研究奠定了坚实的理论基础。     

Flapwise bending vibration analysis of rotating composite cantilever beams

A modeling method for the modal analysis of a rotating composite cantilever beam is presented in this paper. Linear differential equations of motion are derived using the assumed mode method. For the modeling, hybrid deformation variables are employed and approximated to derive the equations of motion. Symmetrical laminated composite beams are considered to obtain the numerical results. The effects of the dimensionless angular velocity, the hub radius and the fiber orientation angle on the variations of modal characteristics are investigated.     

High-throughput analysis of thin-film stresses using arrays of micromachined cantilever beams

We report on a technique for making high-throughput residual stress measurements on thin films by means of micromachined cantilever beams and an array of parallel laser beams. In this technique, the film of interest is deposited onto a silicon substrate with micromachined cantilever beams. The residual stress in the film causes the beams to bend. The curvature of the beams, which is proportional to the residual stress in the film, is measured by scanning an array of parallel laser beams generated with a diffraction grating along the length of the beams. The reflections of the laser beams are captured using a digital camera. A heating stage enables measurement of the residual stress as a function of temperature. As the curvature of each beam is determined by the local stress in the film, the film stress can be mapped across the substrate. This feature makes the technique a useful tool for the combinatorial analysis of phase transformations in thin films, especially when combined with the use of films with lateral composition gradients. As an illustration, we apply the technique to evaluate the thermomechanical behavior of Fe-Pd binary alloys as a function of composition.     

Hardening-softening behaviour of tubular cantilever beams

In the large plastic deformation of a tubular cantilever beam loaded by a force at its tip, the strain hardening of the material tends to increase the load-carrying capacity, while local buckling and cross-sectional ovalization (flattening) occurring in the neighbourhood of the root tends to reduce the moment-carrying capacity and results in structural softening. Experiments were carried out for seamless mild steel tubular cantilevers of radius/thickness ratio ranging from 9 to 20 to explore the development of local buckling and flattening and to examine its influence on the global load-carrying capacity of the beam. A simple theoretical model is proposed to predict the global hardening-softening behaviour of tubular cantilever beams in terms of the material properties and geometric parameters of the tube.     

Instability of cantilever beams with non-linear elements: Butterfly catastrophe

The instability of an elastic cantilever beam combined with a non-linear element, which is subjected to axial and normal concentrated and distributed loads was studied.It was shown that the total potential energy u of the system was equivalent to a universal unfolding of a butterfly catastrophe and, therefore, its approximate locus of failure may be studied by means of the bifurcation set of this type of elementary catastrophe. The problem is a generalization of the case of cantilever beams connected with elastic elements, whose solution is in agreement with the general results. established in the paper.     

麻花钻刚度的有限元分析

钻头的刚度对于研究钻削机理和改进钻头结构具有重要意义。利用有限元分析方法,建立了麻花钻有限元力学模型,对钻头的扭转刚度、弯曲刚度和受压刚度进行了分析计算。结果表明在钻削过程中,横刃处和钻头螺旋槽根部应力最集中,最容易产生损坏,加大钻芯厚度可以大大提高钻头刚度和强度。为优化钻头结构参数,提高其切削性能和耐用度的研究提供了基础。     

Four-beam model for vibration analysis of a cantilever beam with an embedded horizontal crack

As one of the main failure modes, embedded cracks occur in beam structures due to periodic loads. Hence it is useful to investigate the dynamic characteristics of a beam structure with an embedded crack for early crack detection and diagnosis. A new four-beam model with local flexibilities at crack tips is developed to investigate the transverse vibration of a cantilever beam with an embedded horizontal crack; two separate beam segments are used to model the crack region to allow opening of crack surfaces. Each beam segment is considered as an Euler-Bernoulli beam. The governing equations and the matching and boundary conditions of the four-beam model are derived using Hamilton's principle. The natural frequencies and mode shapes of the four-beam model are calculated using the transfer matrix method. The effects of the crack length, depth, and location on the first three natural frequencies and mode shapes of the cracked cantilever beam are investigated. A continuous wavelet transform method is used to analyze the mode shapes of the cracked cantilever beam. It is shown that sudden changes in spatial variations of the wavelet coefficients of the mode shapes can be used to identify the length and location of an embedded horizontal crack. The first three natural frequencies and mode shapes of a cantilever beam with an embedded crack from the finite element method and an experimental investigation are used to validate the proposed model. Local deformations in the vicinity of the crack tips can be described by the proposed four-beam model, which cannot be captured by previous methods.     

基于固有频率的悬臂梁裂缝识别

结构中裂缝的存在使其模态参数发生改变 ,如局部刚度减小、阻尼增大、固有频率降低。把裂缝梁模拟成由扭曲弹簧连接 ,并对其前三阶固有频率的变化与裂缝位置和深度之间的关系进行计算和分析 ;利用特征方程以及前三阶固有频率 ,通过作图法对裂缝参数进行识别。识别结果证明 ,这种方法精度较高、简单可行 ,可用于机械工程实时监测。     

承载面积对金属橡胶材料本构有关系的影响

通过对空心圆柱形金属橡胶材料试件做静态试验并对试验数据进行拟合,得到了非线性本构关系模型中各系数与材料承载面积的变化关系式,从而实现了对金属橡胶材料在密度和高度一定、承载面积发生变化情况下的非线性本构关系的预估.算例验证表明,运用金属橡胶材料非线性本构关系的各系数和材料承载面积的关系式,可较为准确地预估材料的非线性本构关系.     

变截面悬臂梁的 Pro／Mechanica有限元法设计

由于工程中所使用的承受均布载荷的等截面积悬臂梁并不经济,使用Pro／Mechanica对受均布载荷的变截面矩形悬臂梁进行等强度分析设计,使得矩形截面梁的质量在强度允许范围内达到最小,从而可以避免材料的浪费,有工程的实用价值和现实意义。     

Shape optimization of rotating cantilever beams considering their varied modal characteristics

The modal characteristics of rotating structures vary with the rotating speed. The material and the geometric properties of the structures as well as the rotating speed influence the variations of their modal characteristics. Very often, the modal characteristics of rotating structures need to be specified at some rotating speeds to meet their design requirements. In this paper, rotating cantilever beam is chosen as a design target structure. Optimization problems are formulated and solved to find the optimal shapes of rotating beams with rectangular cross section.