Increasing the life of the center plate-center bowl friction unit of a freight car by applying a combined coating formed by electrospark alloying

An increase in the operational reliability of friction units of railway transport by applying antifriction combined coatings formed by electrospark alloying, which ensures their greater strength and adhesion to metal, is considered. Keywords: electrospark alloying combined antifriction coating, strength, adhesion. [email protected]

Two-dimensional Mapping of Bulk Residual Stress Using Cut Mouth Opening Displacement

Background Prior work described an approach for mapping the two-dimensional spatial distribution of biaxial residual stress in plate-like samples, the approach combining multiple slitting measurements with elastic stress analysis. Objective This paper extends the prior work by applying a new variation of the slitting method that uses measurements of cut mouth opening displacement (CMOD) rather than back-face strain (BFS). Methods First, CMOD slitting is validated using an experiment where: BFS and CMOD are measured simultaneously on the same sample during incremental slitting; two residual stress profiles are computed, one from the BFS data and a second from the CMOD data; and the two residual stress profiles are compared. Following validation, multiple adjacent CMOD slitting measurements are used to construct two-dimensional maps of residual stress in plates cut from quenched aluminum. Results The two residual stress versus depth profiles, each computed separately from BFS or CMOD data, are in agreement, with compression near the plate boundaries (-150 MPa) and tension near the plate center (100 MPa); differences between the two stress profiles have a maximum of 25 MPa and a RMS of 7.2 MPa. Repeated biaxial residual stress mapping measurements show the CMOD technique is repeatable, and complementary contour method measurements show the mappings are valid. Aspects of CMOD and BFS deformations during slitting are also described and show they are generally complementary but that CMOD slitting is favorable in narrow samples.

Effects of Elliptical Ring Electrodes on Shear Vibrations of Quartz Crystal Plates

A theoretical analysis is performed on the thickness-shear vibrations of an AT-cut quartz piezoelectric crystal plate with elliptical ring electrodes. The scalar differential equation by Tiersten and Smythe is used. An analytical solution is obtained. Numerical results from the solution show that the thickness-shear mode of interest may be trapped by the ring electrodes and can have a convex, concave, or nearly flat vibration distribution near the plate center, which is fundamentally important when the plate is used as an acoustic wave mass sensor. The vibration distribution is found to be sensitive to both the geometric and physical parameters of the electrodes. Therefore, a careful design is needed to realize the desired trapped mode with suitable center convexity for sensor application

Study on shock resistance of steel plate reinforced with polyurea–woven fiberglass mesh composite under shock wave

To study the dynamic mechanical properties of polyurea–woven fiberglass mesh composite material as a reinforcing layer, the shock resistance tests on plain steel plate, polyurea-reinforced steel plate, and polyurea–woven fiberglass mesh composite–reinforced steel plate were carried out using the large shock tube device. Finite element method simulation was also carried out. The results of experimental and numerical simulation show that the deformation of polyurea–woven fiberglass mesh composite reinforcing layer is smaller than that of pure polyurea reinforcing layer, and the overall deformation of steel plate reinforced by polyurea–woven fiberglass mesh composite is minimal among all the three specimens. With the same polyurea consumption in reinforcing layer, the mass of the 3.5-mm-thick polyurea–woven fiberglass mesh composite–reinforced steel plate is only 2.92% larger than that of the 3.2-mm-thick pure polyurea–reinforced steel plate, but it can reduce the residual displacement of steel plate center by additional 13.03%. The work in this article has some reference value to improve the shock resistance of polyurea-reinforced structure in engineering.

Comprehensive Studies on Rarefied Jet and Jet Impingement Flows with Gaskinetic Methods

This paper presents comprehensive studies on two closely related problems of high speed collisionless gaseous jet from a circular exit and impinging on an inclined rectangular flat plate, where the plate surface can be diffuse or specular reflective. Gaskinetic theories are adopted to study the problems, and several crucial geometry-location and velocity-direction relations are used. The final complete results include flowfield properties such as density, velocity components, temperature and pressure, and impingement surface properties such as coefficients of pressure, shear stress and heat flux. Also included are the averaged coefficients for pressure, friction, heat flux, moment over the whole plate, and the averaged distance from the moment center to the plate center. The final results include complex but accurate integrations involving the geometry and specific speed ratios, inclination angle, and the temperature ratio. Several numerical simulations with the direct simulation Monte Carlo method validate these analytical results, and the results are essentially identical. Exponential, trigonometric, and error functions are embedded in the solutions. The results illustrate that the past simple cosine function approach is rather crude, and should be used cautiously. The gaskinetic method and processes are heuristic and can be used to investigate other external high Knudsen number impingement flow problems, including the flowfield and surface properties for high Knudsen number jet from an exit and flat plate of arbitrary shapes. The results are expected to find many engineering applications.

Simply-Supported Elliptical Auxetic Plates

While the maximum bending moment, and hence maximum bending stress, of a fully clamped elliptical plate under uniform load is independent from the Poisson's ratio of the plate material, the same cannot be said so when the plate is simply supported. This paper develops a simple but sufficiently accurate model for evaluating the bending stresses along the principal axes of a simply supported elliptical under uniform load. Plotted results suggest that bending stresses at plate center along the longer principal axis is minimized by the use of highly auxetic materials if the elliptical plate is almost circular but the use of mildly auxetic material is preferred if the aspect ratio of the elliptical plate is very high. Results also reveal that bending stresses at plate center along the shorter principal axis is minimized when the plate material is highly auxetic. Upon considering the von Mises stress state as the effective stress, it was found that the maximum effective stress is reduced with the use of auxetic and conventional materials for simply supported elliptical plates of low and high aspect ratios, respectively.