水工钢闸门滚轮的滚动摩擦力臂计算方法

为了解决水工钢闸门滚轮在受载荷作用时产生的滚动摩擦力臂的计算方法问题,将滚轮与钢轨的接触问题简化为圆柱与圆柱座之间的接触问题,并以接触线为底作半圆,假设接触线上各点的压力与此半圆在该点的高度成正比。同时根据无限半平面Boussinesq问题的解法推导出滚动摩擦力臂的解析解。最后采用ANSYS建立滚轮全模型与钢轨进行接触分析来验证滚动摩擦力臂解析解的正确性。结果表明该滚动摩擦力臂计算公式简化合理,计算精度能够满足实际要求。     

Interaction of a rotating punch with a half space in the case of partial adhesion in the contact zone

We solve an axisymmetric problem of interaction of a rigid rotating cylinder with an elastic half space. The outer part of the contact zone is subjected to the action of kinematic friction forces and the inner part of this zone is under the action of friction forces of rest. Beyond the punch, the surface of the half space is unloaded. The problem is solved by using the Hankel integral transformation and the method of weighted residuals. We determine the distributions of tangential stresses and displacements on the boundary of the half space and present the plots the internal radius of the sliding zone and the angle of rotation of the punch as functions of the applied moment. Deceased. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 2, pp. 55–61, March–April, 1997.     

Viscoelastic Stress Analysis of a Strip Plate under Moving Contact with Dry Friction

Moving contact problems in a viscoelastic body with a rigidindentor are often seen in an industrial field. An evaluation of thetime-temperature-dependent stress and strain behavior around a contactregion is required in order to make clear the fundamental mechanism ofthe local fracture and wear on the contact surface of the viscoelasticbody under moving loads with dry friction. No analyses have yet beenpublished about the stress/strain of the viscoelastic moving contactproblem with the dry friction using both an experimental and a numericalmethod. The authors discuss an experimental and a numerical model forthe analysis of not only the viscoelastic stress and strain, but alsodeformations, taking into consideration the dry friction. Animage-processing-aided photoviscoelastic technique is applied foranalyzing the principal stress and strain behavior near the contactregion. Also, a two-dimensional plane stress model which consists of aviscoelastic strip and a rigid sliding cylinder is adopted in a finiteelement analysis of the same problem. The time-dependent stress andstrain and the coefficient of dry friction are successfully evaluated byexperimental and numerical methods.     

Plane contact thermoelasticity problem for a two-layer circular hollow cylinder with heat generation

We consider a contact thermoelasticity problem for a two-layer hollow cylinder. One of the layers rotates with respect to the other with a constant angular velocity. Constant stresses on the interface of cylindrical layers are caused by (a) compressive radial stresses or displacements on the side surfaces of the body and (b) a positive difference between ambient temperatures inside and outside the two-layer cylinder. Heat is generated as a result of friction on the contacting surfaces of the layers. We study the effects of the intensity of heat generation and physicomechanical properties of the cylinders on the distributions of stresses, displacements, and temperatures in the body.Franko L'viv State University, L'viv. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 30, No. 6, pp. 24–30, November – December, 1994.     

Specimen shape and the problem of contact in the assessment of concrete compressive strength

This paper proposes a critical analysis of the studies which, since the 1950s, have attempted to quantify the influence of specimen shape on the determination of concrete compressive strength, with special regard to the problem of conversion from cylinder to cube strength and vice versa. From such a retrospective analysis, it emerges that the problem of contact between the platens of the testing machine and the concrete specimen plays a crucial role for the explanation of the variability of the concrete compressive strength as a function of specimen shape. To obtain quantitative predictions and to investigate on the influence of the friction coefficient, uniaxial compressive tests are numerically simulated by using a nonlinear finite element model. Both the constitutive nonlinearity of concrete and the nonlinearity due to contact are taken into account in the formulation. The results of the proposed parametric analysis permit to evaluate the evolution of the conversion ratio between cylinder and cube strength as a function of the friction coefficient. This sheds a new light on the complex nature of this nonlinear relationship, whose value approaches 1 for a friction coefficient close to 0.01, simulating the presence of Teflon, and then approaches asymptotically 0.78 for f = 0.60, as is typical of steel-concrete interfaces.     

Effect of sliding velocity on capillary condensation and friction force in a nanoscopic contact

The influence of sliding velocity on the friction force in a nanoscopic contact was studied on a hydrophilic silicon nitride surface with an Atomic Force Microscope. By submitting a nanoscopic contact to small oscillating lateral displacements, we observe both decreases of the friction force and of the contact radius with an increase of the sliding velocity. We found experimentally that this decrease of the friction force and of the contact radius is correlated to a decrease of the capillary force.     

Analytical study of energy-force parameters in the upsetting-torsion of cylindrical semifinished products made of a highly ductile material

The upper-bound method is used to solve a problem concerning the upsetting of a solid circular cylinder made of a linear strain-hardening material. The cylinder is upset with the use of flat rotating dies. Total power consumed in the operation is minimized on the basis of a parameter that characterizes slip between the dies and the ends of the semifinished product. Analytic expressions are obtained to determine the upsetting force and turning moment. It is found that a decrease in the upsetting force increases the friction coefficient on the contact surfaces, the rotational velocity of the dies, and strain in the height direction.Translated from Problemy Prochnosti, No. 6, pp. 68–71, June, 1994.     

管式变摩擦阻尼器的减振性能试验与数值模拟

提出了一种具有变刚度特征的管式变摩擦阻尼器,该阻尼器的主要部件包括套筒和装于其内并可来回移动的摩擦环。摩擦环外径略大于套筒内径,当摩擦环装入套筒后将产生装配应力,因而当摩擦环左右移动时接触面上将产生摩擦力。变摩擦的功能是通过在套筒壁中摩擦环初始所在部位适当开缝的方式实现的。由于在套筒壁中部开了缝,在其初始状态阻尼器套筒对内环几乎没有约束应力,这样在非工作状态套筒对内环之间的摩擦力就很小了。研究表明,在结构中安装这类变摩擦阻尼器以后,可以使得系统具有半主动变刚度的特征：即在结构偏离平衡位置时,阻尼器的套筒提供越来越大的围束力,导致套筒和内部摩擦环之间产生越来越大的摩擦力,从而能阻止结构位移增加;在结构返回平衡时,阻尼器提供反向摩擦力,其幅值逐渐减小,使结构在复位过程中振动速度得到抑制。对此种被动变摩擦阻尼器的性能试验和有限元数值模拟都证明在工程结构中应用该阻尼器能够达到主动变刚度控制效果,装置非常简单,而变刚度控制系统则是需要计算机和伺服反馈阻尼器支持的。由于该阻尼器构造简单,出力大,价格低廉,能够适应各种结构和机械工程减振控制的需求,因此具有很好的推广应用前景。     

Evaluation of the contact temperature and wear of a composite friction pad in braking

We suggest an analytical model to determine the contact temperature and wear of the working surface of the elements of friction brakes. It is assumed that one of the elements of the friction pair represents a two-period system of conjugated dissimilar layers and the other represents a homogeneous half-space. In the process of friction the wear factor depends linearly on contact temperature. We have studied the influence of the effective parameters of the composite and also of the parameter that characterizes the change in loading from zero to the nominal value and on the distribution of the contact temperature and wear in braking.     

热模拟圆柱形压缩试样上金相观测点的选取

利用ABAQUS有限元分析软件，模拟了热模拟试验中圆柱形压缩试样上的应变分布以及试样鼓形的变化。通过比较试样的鼓形，确定了在Gleeble3800热模拟试验机进行圆柱形试样压缩试验时压头与试样间的摩擦系数，根据此结果模拟计算得到压缩试样上进行金相观测的合适位置。     

Effects of sliding kinematics and normal load on the tribological behavior of metal/polymer contact

Wear and friction simulator with metal cylinder on flat polymer was developed to analyze the tribological behavior of tibial insert used in Total Knee Replacement (TKR). For the kinematics, flexion/extension motion (F/E) was applied to the metal cylinder and anterior/posterior translation (A/P) was applied to the flat polymer. Tests were first carried out with polymethylmethacrylate polymer (PMMA) for which the tribological behavior has been well developed. High density polyethylene (HDPE) was also characterized. In fact HDPE has been firstly used in the tibial insert before the use of ultra high molecular weight polyethylene (UHMWPE). Sinusoidal motions were considered for the F/E and A/P with 8.185 and 5 mm amplitude respectively. F/E and A/P motions were generated separately under a constant applied normal load and 1 Hz frequency. For each test condition, the damage of polymer surfaces was analyzed by following the evolution with the cycle numbers of the friction coefficient, the surface roughness and the micrograph of the wear scar. Whatever the sliding kinematics is, the initial average value of the friction coefficient measured is 0.3 for the steel/PMMA contact and 0.07 for the steel/HDPE contact. These values are similar to those presented in the literature. Specific tribological behavior, which present direct dependence on the sliding kinematics, was identified for each steel/polymer contact.     

Theoretical study of a novel refrigeration compressor – Part I: Design of the revolving vane (RV) compressor and its frictional losses

This paper presents a new rotary type compressor, named ‘Revolving Vane (RV) compressor’, in which frictional losses are effectively reduced through the radical use of a rotating cylinder. The friction at various contact regions are formulated and analyzed, after which a parametric study is conducted to reveal configurations of the compressor that achieves high mechanical efficiencies. Inadvertently, the rotating cylinder is also found to enhance the smoothness of the compressor's operation by reducing its torque fluctuations. Besides good mechanical performance, the RV compressor is also found to possess a high volumetric efficiency, as shown in Part III of this paper series (Teh and Ooi, in press). In further consideration of the small number of parts and simple geometries of its components, it is believed that the RV compressor is well suited and can be readily adopted for refrigeration and air-conditioning applications.     

多层压配组合圆筒有限元分析的简化

多层压配组合圆筒问题常常是轴对称的,且结构的接触边界不变,摩擦的影响可忽略。利用其简单的变形协调关系,可大大简化其有限元分析的过程、减少占机时间、提高计算精度。     

Torsion of a finite cylinder by locally distributed friction forces

We study the stressed state of a finite cylinder under the action of torsional stresses caused by the action of friction forces. As a result of the separation of the angular variable, we reduce the analyzed three-dimensional problem to the solution of two-dimensional boundary value-problems. It is shown that the loads caused by pure torsion strongly affect the stressed state of the cylinder. The problem of pure torsion of a cylinder by loads locally distributed over its lateral surface is analyzed. It is shown that the singularities of stresses τ_φz at the point of discontinuity of the load are formed under the action of piecewise continuous tangential loads. Finally, we study the variations of the maximum shear stresses in the cylinder when the distribution of load approaches a rectangular distribution.     

Thermoelastic contact of a retaining ring with a cylinder under the conditions of frictional heat generation

We give the mathematical statement and construct the solution of the static thermoelastic problem of contact interaction of an elastic retaining ring with a circular hollow cylinder inserted in it. The bodies are compressed by a load varying along the axis of the system under the conditions of load-free contact on the surface of the ring or along an arc of the circle. In the case where radial displacements of the contact surface of the retaining ring are approximated by displacements of the surface of a long circular hollow cylinder and the process of stationary frictional heat generation is taken into account, we reduce the posed problem to systems of integral equations whose structure is determined by the type of conditions of thermal contact. We propose a numerical algorithm for the solution of these systems and study the influence of the input parameters of the problem on the distributions of contact pressure and temperature. On the basis of these results, we make a conclusion that the influence of the character of variation of the compressive load along the axis on the distribution of contact pressure is significant in the case where the kinematic conditions of interaction of the bodies are described by the Hertz theory. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 36. No. 3. pp. 42–52, May-June, 2000.     

Thermal performance of multilayer insulation around a horizontal cylinder

Thermal performance of multiplayer insulation (MLI) is affected by contact pressure between adjacent layers. In order to evaluate the thermal performance of the MLI fabricated in the horizontal cryostats of superconducting magnets, it is important to investigate the contact pressure in the MLI. In case of a horizontal cryostat, the MLI is wound around horizontal cylindrical surface and is compressed at the upper part of the cylinder due to the MLI self-weight. At first, a single thin film wound around the horizontal cylinder was analyzed to evaluate the contact pressure acting on the cylinder. The analysis has been extended to the multiply wound film around horizontal cylinder, in order to investigate the distribution of contact pressure between adjacent layers. By using experimental data obtained with a flat panel calorimeter, the results of this analysis have been applied to evaluate the thermal performance of MLI around a horizontal cylinder. And the non-dimensional contact pressure parameter P^* has been introduced as a useful parameter to evaluate and compare the thermal performance among different kinds of MLI.     

钢板弹簧刚度特性及接触摩擦的非线性有限元分析

传统的钢板弹簧计算方法在精确建立力学模型时难度较大。考虑钢板弹簧实际工作过程中的大变形、片间接触和摩擦等多种非线性因素,建立某钢板弹簧的计算模型。提出考虑由相邻叶片所组成的接触对上接触压力和应力的分布分析方法,计算不同摩擦系数和载荷情况下的变形、等效应力和接触摩擦力对板簧力学性能的影响,以及不同簧片接触对之间接触压力、摩擦应力,接触总应力的相关性,得到若干研究结果。所提出的方法为进一步研究钢板弹簧中相邻叶片之间的非线性状态提供参考。     

Frictional contact of an inertial cylinder with casing under the conditions of heat generation and wear

We construct the solution of the problem of thermoelastic contact of an inertial cylinder with rigid casing under the conditions of frictional heating and wear of the material of the cylinder and perform the numerical analysis of contact characteristics in the processes of acceleration and deceleration of the cylinder. Translated from Fizyko-Khimichna Mekhanika Materialiv. Vol. 36, No. 3, pp. 53–58. May-June. 2000.     

Pressure of the lateral surface of a cylinder on a periodically layered half space

We consider a two-dimensional contact problem of indentation of an absolutely rigid cylinder into an inhomogeneous half space with periodic structure. The zone of periodicity consists of two homogeneous elastic layers. The solution of the classical problem of the theory of elasticity is compared with the solution of the problem in which the inhomogeneous half space is replaced by a homogenized space. We propose simple engineering formulas for the evaluation of contact characteristics (the width of the contact zone and the distribution of contact pressure) approximating the solution of the problem in the case where the homogenized medium inadequately models the inhomogeneous medium. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 3, pp. 51–57, May–June, 2007.     

Standing contact fatigue with a cylindrical indenter

A hardened steel cylinder was repeatedly pressed against a flat case‐hardened steel specimen that was equally wide as the cylinder was long. Some contact end effects were noted as a result of limited plastic deformation. A strain gauge on the contact surface, just outside the contact and oriented perpendicular to the cylinder detected a surface strain when the cylinder was loaded. The non‐zero surface strain was the result of boundary effects of the finite specimen. Four different types of contact fatigue cracks developed in and below the specimen contact surface. The cracks were named lateral, median, contact end and edge cracks. Changes in the measured surface strain values could be used to determine when the lateral and edge cracks developed. The order in which all four crack types typically developed was determined from optical crack observation at test termination, strain measurements and stress computations. Numerical computations using finite‐element (FE) analyses were used to verify the surface strain behaviour due to loading and cracking; to verify contact end effects; crack locations and crack orientation by aid of the Findley multi‐axial fatigue criterion.