Effect of operation parameters on thermal loading of wet brake discs: Part 2. Study results

The paper presents the results of a numerical study of a number of operation parameters on the thermal loading of the friction pairs of an wet brake with the radial arrangement of oil grooves. The regularities of the formation of the three-dimensional transient temperature field in the brake discs in the stationary friction mode are determined. The functional dependences of the maximal temperature of the discs with the linings made of various frictional materials on the operation parameters are obtained.     

Low and high cycle fatigue of automotive brake discs using coupled thermo-mechanical finite element analysis under thermal loading

Journal of Mechanical Science and Technology - To predict the thermal fatigue life and thermal stress phenomena of a brake disc, it is necessary to study the thermo-mechanical coupling effect in...     

Numerical simulation of thermal conditions in the oil-cooled friction multidisc clutch of a power-intensive wheel tractor. Part 1. Problem formulation

Numerical study is performed of the effect of the inertial force parameters on the thermal conditions of a multidisc oil-cooled friction clutch of a rear power take-off shaft of a power-intensive wheel tractor. A system of differential equations is shown of the dynamics of slippage of the driven and driving disks when the clutch is actuated and it is solved numerically with the Runge-Kutt method. An initial boundary problem is formulated describing the thermal processes in the package of disks when friction heats the clutch; it is solved numerically with the finite elements method.     

A study of airborne wear particles generated from organic railway brake pads and brake discs

Brake pads on wheel-mounted disc brakes are often used in rail transport due to their good thermal properties and robustness. During braking, both the disc and the pads are worn. This wear process generates particles that may become airborne and thus affect human health. The long term purpose of ‘Airborne particles in Rail transport’ project is to gain knowledge on the wear mechanisms in order to find means of controlling the number and size distribution of airborne particles. In this regard, a series of full-scale field tests and laboratory tests with a pin-on-disc machine have been conducted. The morphology and the matter of particles, along with their size distribution and concentration, have been studied. The validity of results from the pin-on-disc simulation has been verified by the field test results. Results show an ultra-fine peak for particles with a diameter size around 100 nm in diameter, a dominant fine peak for particles with a size of around 350 nm in diameter, and a coarse peak with a size of 3–7 μm in diameter. Materials such as iron, copper, aluminum, chromium, cobalt, antimony, and zinc have been detected in the nano-sized particles.     

Numerical simulation of operation heat modes of multidisc oil-cooled vehicle brake. Part 1. Heat problem solution

The paper considers the operating heat modes of multidisc oil-cooled vehicle brakes under single and multiple braking, as well as under deceleration over a long downgrade. The initially boundary-value heat problem for the given operating modes of the brake is formulated and solved by the finite-element method. The regularities of formation of nonstationary temperature fields both on the contact surfaces and in the bulk of the brake friction elements are obtained for preset braking modes. The dependences are obtained for the maximal contact surface temperature on the metal counterbody and frictional material vs. the load and velocity parameters of vehicle motion. A method for forecasting the critical operating regimes of multidisc oil-cooled brakes is proposed for the given operation conditions of the vehicle.     

Range of operation of thermal imaging systems. Part I. Calculation technique

A method of calculating the range of operation of thermal imaging systems during detection, classification, recognition, and identification of objects is considered. The method is based on finding the functional relationship of the sought quantities with the threshold temperature sensitivity and the temperature-frequency characteristic of thermal imaging systems in the cases of tracking objects in homogeneous and non-homogeneous fields of thermal radiation.     

Noise and vibration in brake systems of vehicles. Part 1: Experimental procedures

The paper describes the vibroacoustic phenomena generated during frictional interaction of solid bodies. A classification is given for brake-induced noise. Modern experimental methods for studying vibroacoustic phenomena in metal-polymer friction contacts are analyzed. The main approaches to reducing noise and vibration in vehicle brakes are considered.     

Numerical analysis of temperature fields and thermal stresses in the friction discs of a multidisc wet clutch

The subject of the considerations in this paper is a multidisc wet clutch embodying alternately assembled discs of two types: discs made entirely of steel and discs with a steel core lined with layers of friction material. A model of the unsteady heat conduction process in such discs has been developed with account taken of the non-homogeneity of the thermal properties of these discs. Heat conduction equations have been derived and initial and boundary conditions given. To solve this problem, the finite difference method was used. Next, the thermal stresses in the steel discs, regarded as quasi-static, were considered. The stresses were calculated by the finite element method. Calculations of the temperature fields and thermal stresses were performed for a specific typical clutch engagement. Discussion of the results obtained is presented. In the analysis of the temperature distributions and stresses, attention has been focused on the determination of factors permitting a reduction in stresses.     

High voltage electron microscopy of wet whole cells. Effect of different wet cell preparation methods on visibility of structures

Dimensional measurements have been made on a small number of tracings of low magnification scanning electron micrographs of trabecular bone sections, using the Quantimet Image Analysing Computer, with a view to expressing the properties of the local bone pattern in a quantitative manner. Measurements of the orthogonally projected length of the boundary profile of the interface between bone and marrow were made as a function of the direction of projection, and these showed that the majority of the patterns were distinctly anisotropic. A formula is proposed for calculating the mean widths of the trabecular bands as they appear on the surfaces of the sections, from the mean area of bone and the boundary profile length. As the validity of this formula is not theoretically evident, the results have been compared with direct experimental measurements, and found to agree very well. The mean intercept lengths in the bone and in the marrow spaces have been calculated as a function of direction across the section. The polar diagrams of these lengths are found to have the shapes of ellipses, to an unexpected degree of accuracy. This makes it possible to express the departure from isotropy of the pattern by a single number, for instance by the ratio of the axes of the ellipse. The essential limitations of the methods used in these experiments are briefly discussed, in particular the impossibility of finding the exact symmetry properties of the surface patterns by experiments of this type.     

Range of operation of thermal imaging systems. Part II. Algorithm,initial data,and calculation results

Optoelectronics, Instrumentation and Data Processing - Results of a computational experiment, the choice of initial data, and the algorithm of calculating the range of operation of thermal imaging...     

Effect of loading and lamination parameters on the optimum design of laminated plates

This paper illustrates the effect of loading conditions and lamination parameters on the optimum design of the laminated composite plates. Optimum design procedure based on the flexibility criterion is presented in this paper. The objective is to determine the optimum thickness of the laminate layers and its optimum orientations without exhibiting any failure. The finite element method based on Mindlin plate theory is used in conjunction with an optimization method in order to determine the optimum design. Newmark implicit time integration scheme is used to discretize the time domain and calculate the transient response of the laminated plate. Exterior penalty method is exploited as a constrained minimization technique. For this purpose, four numerical examples are presented to figure out the effects of dynamic loading profile, boundary conditions, number of layers, and degree of orthotropy on the optimum weight design.     

Gas-phase basicities of polyfunctional molecules. Part 1: Theory and methods

The experimental and theoretical methods of determination of gas-phase basicities, proton affinities and protonation entropies are presented in a tutorial form. Particularities and limitations of these methods when applied to polyfunctional molecules are emphasized. Structural effects during the protonation process in the gas-phase and their consequences on the corresponding thermochemistry are reviewed and classified. The role of the nature of the basic site (protonation on non-bonded electron pairs or on pi-electron systems) and of substituent effects (electrostatic and resonance) are first examined. Then, linear correlations observed between gas-phase basicities and ionization energies or substituent constants are recalled. Hydrogen bonding plays a special part in proton transfer reactions and in the protonation characteristics of polyfunctional molecules. A survey of the main properties of intermolecular and intramolecular hydrogen bonding in both neutral and protonated species is proposed. Consequences on the protonation thermochemistry, particularly of polyfunctional molecules are discussed. Finally, chemical reactions which may potentially occur inside protonated clusters during the measurement of gas-phase basicities or inside a protonated polyfunctional molecule is examined. Examples of bond dissociations with hydride or alkyl migrations, proton transport catalysis, tautomerization, cyclization, ring opening and nucleophilic substitution are presented to illustrate the potentially complex chemistry that may accompany the protonation of polyfunctional molecules.     

Vibration and noise in brake systems of vehicles. Part 2: Theoretical investigation techniques

The paper reviews theoretical research into vibroacoustic phenomena in transport brake systems. The mechanisms of occurrence of different types of noise and vibration in brakes are described. Analytical, numerical, and experiment-calculated methods for studying brake noise are discussed and their disadvantages from the point of view of obtaining adequate calculation models are analyzed. The results of prediction of the vibroacoustic activity of friction units based on calculation methods are considered.     

Effect of methods for fixing and loading of cylindrical shells on their stability and supercritical behavior

The effect of the methods of fixing and external-pressure loading of an elastic isotropic cylindrical shell on its sub- and supercritical deformation is investigated. A geometrically nonlinear statement of the edge problem in the form of the technical theory of finite deflection hollow shells is applied. The edge problem is digitized with the Rayleigh-Ritz method. The solution to the set of nonlinear algebraic equations is sought using the methods of continuation by the parameter close to the optimal one. The versions of shell sealing and supporting as well as uniform lateral pressure and uniform compression are considered. The trajectories of shell loading are plotted and the shapes of their supercritical equilibrium states are found. The axial compressing load is found to exert a larger effect on the upper and lower critical pressure as compared to the conditions of shell end fixing. Moreover, axial loading of short shells yields an increase in the critical pressure rather than its decrease, as is customary in the theory of shell stability.     

Effect of damping parameters on dynamic behavior of program controllable drives of coordinate systems with belt drive: Part 1

The results of a study on how damping affects the parameters of oscillations that appear in belt drives of coordinate systems when used in the process equipment for diamond disk cutting of plates from semiconducting materials (silicon, sapphire, etc.). Oscillation often impair workmanship. Methods of reducing the amplitude of oscillations by controlling the damping parameters are shown.     

An experimental study of the ratchetting and creep of thick flanged tubes subjected to steady axial mechanical loading and transient thermal loading

The aims of the investigation were to obtain experimental data against which finite element predictions can be assessed and to see whether the lead alloy used was suitable as a “ratchetting” model material. Thermal ratchetting tests were performed on lead alloy flanged tube components. In some of the tests, dwell periods were allowed between successive thermal shocks. Electrical resistance strain gauges were used to measure the ratchet and creep strains in plain tube and stress concentration regions.It was found that both the plain tube and peak fillet ratchet strains increased with increasing mechanical and thermal load for short dwell periods. However, the ratio of the peak fillet to plain tube ratchet strains reduced with increasing mechanical and thermal load. Also, the ratio of the peak fillet to plain tube ratchet strains increased with increasing dwell period.The data obtained from the lead alloy model component tests were found to correlate with data from a number of different components made from various materials, indicating that the material may be useful as a “ratchetting” model material.     

Management of the variability of vibration response levels in mistuned bladed discs using robust design concepts. Part 1: Parameter design

Small unavoidable differences (e.g. 5%) between blades on a bladed disc, called mistuning, can lead to a huge variation of forced vibration response levels, and some of them are extremely high (e.g. 500% of the level experienced on every blade is all blades are identical). In this first half of a two-part article, a novel approach of designing a bladed disc with a lower chance of encountering high vibration response levels is evaluated. A robust design concept is applied to manage the variability of the vibration response levels, and the new approach resembles parameter design in Taguchi method of robust design. A “robustness map” is created using simulations results of a 6-degree-of-freedom (6-DOF) system, and such a map is validated by two more complicated models. The robustness map is used to explain the behaviour of bladed discs investigated in previous studies and to give possible methods of delivering more robust bladed disc designs.     

Effect of surface roughness on elastohydrodynamic traction: Part 1

The effect of surface roughness on traction performance was experimentally studied using a two‐roller tester. The nature of the contact was investigated using electrical resistance and electrical capacitance methods. Increased shear stress was observed in the viscous region, which could be attributed to a higher average shear rate and to greater viscosity under EHD contact conditions due to pressure fluctuations caused by the surface texture.     

起重机制动下滑量检测的现状分析和研究

起重机在制动后,负载由于自重将向下滑动一个距离,即制动下滑量。制动下滑量过大将直接影响到现场工作人员的安全,因此,制动下滑量是衡量起重机性能的重要指标。对于制动下滑量的测量,虽然各生产厂家在设备出厂时均已采用不同的测量方法进行测量,但从使用安全出发,