Research on lateral stability and rollover mechanism of articulated wheel loader

A seven-degrees-of-freedom (DOF) dynamic model was established based on the Lagrange equation to analyse the lateral stability and instability mechanism of an articulated wheel loader. A scale wheel loader was designed and manufactured to validate the dynamic model in two conditions, namely turning on slopes and passing over obstacles. Experimental data and simulated data fitted well on the whole, so the developed dynamic model was proved to be useful and could serve as an important tool to analyse the stability of wheel loaders. At last, the lateral stability of one ZL50 wheel loader was analysed by using this dynamic model. The results showed that there is a phenomenon of sudden stability losing during the wheel loader cornering due to the relative rotation between the subframe and the rear axle. The subframe can enhance the stability when the wheel loader is passing over obstacles but reduces the stability when it is turning.     

Influence of the rail pad on a vehicle travelling on a straight track

In the following text, the influence of the stiffness of rail fastening systems of high‐speed railway lines on the dynamic stability of a vehicle travelling along a straight track is investigated. The dynamic behaviour of the rail head in lateral direction is incorporated in the model by means of mechanical models derivedfrom a preceding frequency analysis of the track. For the wheel‐rail interface, linear contact mechanics and kinematic relations are applied. The investigation leads to the conclusion that on high‐speed lines the critical velocity of vehicles is reduced as a result of the increased elasticity of the rail pads. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

关于轮网络的一簇猜想

轮网络是由Cayley图模型设计出来的一种新型互连网络模型.星网络、冒泡排序网络、修正冒泡排序网络可嵌入轮网络.为了揭示它的整体结构,对轮网络提出如下一簇猜想:轮网络是边不交的i个Hamilton圈及2(n-i)-2个完美匹配的并,其中1≤i≤(n-1);并证明了当n=4,5,6,1≤i≤3时,猜想成立.     

On the decay of solutions in nonsimple elastic solids with memory

The decay of solutions in nonsimple elasticity with memory is addressed, analyzing how the decay rate is influenced by the different dissipation mechanisms appearing in the equations. In particular, a first order dissipation is shown to guarantee the asymptotic stability of the related solution semigroup, but is not strong enough to entail exponential stability. The latter occurs for a dissipation mechanism of the second order, that is, the same order as the one of the leading operator.     

Modelbased Investigations of Gyroscopic Effect on the (Elasto-)Kinematics of Suspension Systems

During wheel bumping caused by stochastic road excitation, the wheel performs rotational and translational movements. The bump and rebound wheel velocity leads to significant angular velocities based on the (elasto-)kinematics of the suspension system. Based on the gyroscopic effect, moments arise about the rotating wheel induced by the angular change while bumping. Therefore it leads to undesirable wheel changes and degrades the tire contact and finally decreases the driving stability. A flexible MBS-model of the five-link rear axle system that includes these effects has been built up to allow a detailed investigation of the gyroscopic effect. Using the simulation results, conclusions can be drawn for refining design criteria for the kinematics, elastokinematics and topology of the suspension system to increase the active safety of the vehicle. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Stability of steady motions of a mobile robot with roller-carrying wheels and a displaced centre of mass

The motion of a mobile three-wheel robotic vehicle on a horizontal surface is investigated. Passive rollers are fastened along the rim of each wheel, enabling each wheel not only to roll in the usual manner, but also to move perpendicular to its plane. Each of these wheels, as well as the ordinary wheels, is equipped with one drive, which rotates the wheel about its axis. The vehicle equipped with roller-carrying wheels can move in any direction with any orientation. The motion of the robot on a horizontal surface is studied in the case where the centre of mass of the robot deviates from the geometric centre of the triangular platform, and there is no slip at the points of contact of the rollers with the supporting surface. In the case of free motion of the robot, an additional first integral is pointed out and the exact solution found is analysed. An equation for specifying steady motions, under which a constant voltage is supplied to the DC motors that drive the wheels, is constructed. The stability of the rectilinear motion of the robot is investigated.     

Cavity identification in linear elasticity and thermoelasticity

The aim of this paper is an analysis of geometric inverse problems in linear elasticity and thermoelasticity related to the identification of cavities in two and three spatial dimensions. The overdetermined boundary data used for the reconstruction are the displacement and temperature on a part of the boundary. We derive identifiability results and directional stability estimates, the latter using the concept of shape derivatives, whose form is known in elasticity and newly derived for thermoelasticity. For numerical reconstructions we use a least‐squares formulation and a geometric gradient descent based on the associated shape derivatives. The directional stability estimates guarantee the stability of the gradient descent approach, so that an iterative regularization is obtained. This iterative scheme is then regularized by a level set approach allowing the reconstruction of multiply connected shapes. Copyright © 2007 John Wiley & Sons, Ltd.     

The Mechanical Stability for the Hand-Arm System

The present paper contains a study regarding importance stability in the mechanical systems, mechanical systems are emerging under mechanical vibrations action, it referring especially to the human hand–arm system. Mechanical systems stability is directly influenced of the dumper and the elasticity factors. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The mixed boundary value problem for the elasticity theory system in unbounded domains

The paper deals with the uniqueness and stability of generalized solutions to the mixed boundary-value problem for the elasticity theory system in an unbounded domain, coinciding with a cone in a neighborhood of infinity. It is assumed that the boundary of the domain consists of two parts: the Dirichlet condition is prescribed on one of them, denoted by Γ₁, and the Neumann condition is prescribed on the other. The paper contains sufficient conditions (in terms of metric properties of Γ₁) for the validity of the Korn and Hardy inequalities, which imply the uniqueness and stability of the solution to the considered problem in appropriate function spaces. Bibliography: 8 titles. Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 18, pp. 106–156, 1995.     

Mechanisms for flow and forced high elasticity of cross-linked polymers

A quantitative model is proposed for flow and forced high elasticity of cross-linked polymers based on the cluster model of amorphous state structure. The flow process is seen as the loss of displacement stability by the clusters, while forced high elasticity is related to the mechanical devitrification of the softpack matrix. Fractal analysis was used to show a turbulent regime for the forced high elasticity of cross-linked polymers.Kabardino-Balkariya State University, Nal'chik. Russia. Donetsk Physics and Mechanical Sciences University. Ukraine. Branch of the Institute of Ecology. Kashkhatau, Kabardino-Balkariya. Russia. Center for Composite Materials, Moscow State Open University, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 2, pp. 270–278, March–April, 1996.     

Stability of Timoshenko systems with thermal coupling on the bending moment

The Timoshenko system is a distinguished coupled pair of differential equations arising in mathematical elasticity. In the case of constant coefficients, if a damping is added in only one of its equations, it is well‐known that exponential stability holds if and only if the wave speeds of both equations are equal. In the present paper we study both non‐homogeneous and homogeneous thermoelastic problems where the model's coefficients are non‐constant and constants, respectively. Our main stability results are proved by means of a unified approach that combines local estimates of the resolvent equation in the semigroup framework with a recent control‐observability analysis for static systems. Therefore, our results complement all those on the linear case provided in [22], by extending the methodology employed in [4] to the case of Timoshenko systems with thermal coupling on the bending moment.     

Control of the rolling of a wheel by changing its imbalance

The motion of a wheel (rolling without slipping) in a vertical (longitudinal) plane is considered. The load, which is modelled as a point mass, can be moved within the wheel in a hollow which is positioned along its diameter. By moving the load from one end of the hollow to the other in a specific way, it is possible to manage the rolling of the wheel. An algorithm is constructed for control of the position of the load using which the load is periodically moved from one end of the hollow to the opposite end while the wheel rolls (non-uniformly) over the surface.     

Control of the elastic properties of a shell working at stability

This examines a shell with elastic properties varying across the coordinates, which are prescribed by means of scalar functions of the invariants of the elasticity tensor. The basis of the arrangement of the tensor for the elasticity consists of q linear-independent tensors of the fourth range (q is the number of linear-independent components of the elasticity tensor) which are obtained by multiplying and turning the first tensor of the surface and the tensor characterizing the class of symmetry of the medium. The invariants of the elasticity tensor present in the stability equation and their derivatives are taken to be the equations and parameters for the state of the system (shell), and the problem is thus reduced to a problem of optimum equations. As an example we shall examine an orthotropic cylindrical shell with a model varying over the length under the action of external pressure.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 93–100, January–February, 1974.     

Normality Condition in Elasticity

Strong local minimizers with surfaces of gradient discontinuity appear in variational problems when the energy density function is not rank-one convex. In this paper we show that the stability of such surfaces is related to the stability outside the surface via a single jump relation that can be regarded as an interchange stability condition. Although this relation appears in the setting of equilibrium elasticity theory, it is remarkably similar to the well-known normality condition that plays a central role in classical plasticity theory.     

The rolling of a wheel along a corrugated rail

The rolling without detachment of a rigid massive wheel, carrying a static load, along a rail with undulations on the running surface, which arises as a result of non-uniform wear, is investigated. The rail is supported by an elastoviscous base. Because of the inertia of the wheel and the carriage the horizontal component of the velocity of the wheel centre differs only slightly from a constant quantity, and hence the motion of the wheel along the rail is assumed to be uniform. Steady vertical vibration of the wheel is considered. The vertical coordinate of the wheel centre, and also the difference between the longitudinal coordinates of the wheel centre and the point of contact of the wheel and the rail, are periodic and, correspondingly, even and odd functions of the longitudinal coordinate of the wheel centre, and their period is equal to the wave length on the rail surface. The periodic force of interaction of the wheel and the rail is given in the form of a Fourier series. Short waves, the amplitude of which is much less than their length, are often observed on the rail surface, and this length is much less than the wheel radius. In this case the coefficients of the Fourier series are expressed in terms of Bessel functions of the first kind of integer order. Observations show that the depth of the short wave on the rail surface increases until the radius of curvature in the rail trough approximates to the wheel radius, and hence it is assumed that these radii are close to or equal to one another. In this case the trajectory of the wheel centre differs considerably from the wave on the rail surface.     

Optimization of a member with variable modulus of elasticity

The problem of the optimal (from the weight standpoint) law of longitudinal variation of the modulus of elasticity is considered with reference to a member in axial compression when the limit state is reached as a result of loss of stability. Constraints are imposed on the modulus of elasticity. The problem is solved with the aid of the apparatus of the generalized maximum principle.     

Investigation of the stability of the physicomechanical properties of carbon fibers 1. Dependence of Young's modulus on the cross-sectional area of the fiber

The modulus of elasticity in tension and the density of various carbon fibers (re-inforcement for high-modulus carbon-reinforced plastics) have been studied. There is an experimentally confirmed dependence of the modulus of elasticity on the orientation and density of the monofilament which explains the variation of this characteristic in a fiber bundle. It is shown that the principal factor determining the modulus of elasticity and its stability in a bundle of carbon fibers is the orientation and its variation for the individual fibers.     

Stability of a Circular Sandwich Ring under an Axially Symmetric Temperature Field Inhomogeneous across the Thickness

The linearized problems on the stability of a circular sandwich ring of symmetric structure under an axially symmetric temperature field inhomogeneous across the core thickness are stated and analytical solutions to them are given. The first problem deals with the mixed flexural buckling form (BF) of the ring as a whole, realized as a result of buckling in one of the load-carrying layers due to formation of precritical pressure stresses in the layer. The second problem considers purely shear BFs when one load-carrying layer is rotated relative to the other. The deformation processes for the load-carrying layers are described by the Kirchhoff-Love model, and for the core of arbitrary thickness - by two models, namely by the equations of the plane problem of elasticity theory and by the model of a transversely soft layer of arbitrary thickness (the same equations simplified by the assumption of zero circumferential normal stresses). Within the frames of the first model adopted for the core, the shear BF is theoretically possible but practically unrealizable, since the mixed flexural BF arises earlier than the shear BF.     

径向轴对称冲击载荷下正交异性固支圆板的Liapunov稳定性

本文用Ｌｉａｐｕｎｏｖ第二方法分析了周边受轴对称径向冲击载荷作用的极正交各向异性固支圆板的稳定性．分析是在小挠度和弹性范围内进行的．冲击载荷被假定具有阶梯脉冲形式．导出了相应的稳定性条件．     

Effect of price elasticity of demand in monopolies with gradient adjustment

We study a monopolistic market characterized by a constant elasticity demand function, in which the firm technology is described by a linear total cost function. The firm is assumed to be boundedly rational and to follow a gradient rule to adjust the production level in order to optimize its profit. We focus on what happens on varying the price elasticity of demand, studying the effect on the equilibrium stability. We prove that, depending on the relation between the market size and the marginal cost, two different scenarios are possible, in which elasticity has either a stabilizing or a mixed stabilizing/destabilizing effect.