The Effect of Laser Texturing of Steel Surfaces and Speed-Load Parameters on the Transition of Lubrication Regime from Boundary to Hydrodynamic

Laser surface texturing (LST) is an emerging, effective method for improving the tribological performance of friction units lubricated with oil. In LST technology, a pulsating laser beam is used to create thousands of arranged microdimples on a surface by a material ablation process. These dimples generate hydrodynamic pressure between oil-lubricated parallel sliding surfaces. The impact of LST on lubricating-regime transitions was investigated in this study. Tribological experiments were carried out on pin-on-disk test apparatus at sliding speeds that ranged from 0.15 to 0.75 m/s and nominal contact pressures that ranged from 0.16 to 1.6 MPa. Two types of oil with different viscosities (54.8 cSt and 124.7 cSt at 40°C) were evaluated as lubricants. Electrical resistance between flat-pin and laser-textured disks was used to determine the operating lubrication regime. The test results showed that laser texturing expanded the range of speed-load parameters for hydrodynamic lubrication. LST also reduced the measured friction coefficients of contacts that operated under the hydrodynamic regime. The beneficial effects of laser surface texturing are more pronounced at higher speeds and loads and with higher viscosity oil.     

Hybrid method combining orthogonal projection Fourier transform profilometry and laser speckle imaging for 3D visualization of flow profile

This paper reports a straightforward technique for three-dimensional (3D) visualization of a flow profile by a hybrid algorithm combining Fourier transform orthogonal fringe projection and laser speckle imaging techniques. The use of orthogonal projection aims to suppress the zero order allowing surface reconstruction with high spatial resolution and accuracy while analyzing the intensity fluctuations of diffuse backscattered laser light providing 2D flow information. Once both are achieved, 3D flow visualization can be displayed. The method is experimentally validated first with a plastic tube filled with scattering liquid (milk) running at various controlled flow rates and then with the tube embedded under scattering layers (chicken breast) of varying thickness. The system includes a single, common camera, a commercial projector (profilometry channel), a laser light source (flow channel), and a computer station. In addition, orthogonal projection processing was combined with Hilbert transform, increasing the visualization and resolution of the measured flow profile.     

Nonlinear equations of laminated panels with laminated stiffeners

The nonlinear equations for a stiffened laminated panel, which modeled by plate and beam elements, are derived by applying the variational principle on the potential energy. The equations include the equation for the panel sections between the stiffeners, the continuity requirements and the boundary conditions. These nonlinear equations by which the post-buckling behavior is characterized are exact in terms of Von Karman's kinematic relations.     

Dependence of the wear resistance of high carbon chrome-manganese facings on peculiarities of structurization

Tashkent Institute of Railroad Transport Engineers. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 45–46, February, 1992.     

Imperfection sensitivity of fiber-reinforced, composite, thin cylinders

The imperfection sensitivity of thin cylindrical shells, made out of fiber-reinforced composite material and subjected to uniform axial compression, and the effects upon it of certain parameters, are investigated. The methodology is based on linear constitutive relations, nonlinear kinematic shell equations (Donnell-type) and the usual lamination theory. The laminate consists of orthotropic laminae, stacked in a general manner (asymmetric laminate). The uniform axial compression is applied eccentrically, and the geometrically imperfect cylindrical shell can be supported in various ways at the boundaries. In this investigation a number of parametric studies are performed. The scope of these studies is to establish the effect of (a) in-plane and transverse boundary conditions and (b) load eccentricity, on the imperfection sensitivity of typical boron/epoxy laminated cylindrical shells with various stacking sequences of laminate. The sensitivity is established by calculating critical loads for various imperfection amplitudes and shapes.     

A generalization of Potters' method

A method for the solution of large systems of linear equations is presented, based on a tridiagonal partition with varying order of the submatrices. Though formally similar to the Potters' algorithm it removes all of its significant limitations.     

Application of DSISR program to recessed shells of revolution

Application of the DSISR program to recessed shells of revolution is illustrated on the examples of a cylinder with two diametrically-opposite rectangular cutouts and a sphere with a single trapezoidal cutout. The program which is suitable for a wide range of static and dynamic problems was developed for general linear analysis of shells of revolution with arbitrary stiffness and mass density distributions. In the analysis, the equations of motion are derived with the aid of Sanders' theory, and the numerical solution procedure is based on Fourier expansion in the circumferential direction, on finite differences in the meridional direction, and on Houbolt's method in the time domain.