Surface Layer Of Elements Research Articles

ВЫБОР ПАРАМЕТРОВ ТЕХНИЧЕСКОГО СОСТОЯНИЯ ЭЛЕМЕНТОВ ПОГЛОЩАЮЩЕГО АППАРАТА, ОПРЕДЕЛЯЮЩИХ ЕГО БЕЗОТКАЗНОСТЬ

The problems to plan and ensure a given level of reliability of mechanical systems at all stages of their design and operation occupy an important place in the problem of ensuring the quality of machine-building products. With a significant number of scientific methods and approaches to solving theoretical and applied issues of reliability theory, one of the key directions is to determine the reliability indicators of technical systems and their elements, in particular a wide range of products including sliding friction pairs with periodic impacts. The study of failure origins, from the point of view of physical-mechanical processes occurring in surface layers of elements, under the influence of external factors, allows selecting parameters characterizing the functional state of the pair, and, as a result, its reliability. For example, for sliding friction pairs with periodic impacts, such a parameter is the geometric dimensions of the conjugate elements. The decrease in the geometric dimensions of conjugate elements, due to wear, characterizes the rate of change of the initial parameter values to the maximum permissible ones determining the failure, and can be approximated by linear, power, exponential and other dependencies obtained from actual measurements. According to the obtained functional dependencies of parameter changes over operating time, it makes possible to determine the norm for the parameter regulating their pre-failure state, beyond which failure prediction is possible with varying probability, and, as a result, the reliability of the system as a whole. The use of this method to reliability forecasting through the determination of the pre-failure state of the system can be projected onto technical objects, which performance indicators are geometric parameters that ensure the performance, first of all, of the functions of the elements themselves and the entire technical system, and worn out during operation.

Topological Design of Stiffener for Static Bending of Stiffened and Sandwiched Plates

This paper presents a 2.5D moving iso-surface threshold (MIST) approach for findingtopological configurations of stiffeners for stiffened and sandwiched plates subjected to staticbending load. In this 2.5D MIST approach, (a) 3D elements are used to discretize a continuum intomulti-layered finite element model with either one or two surface layers of elements as non-designdomain; (b) the 3D non-surface elements, collocated in the thickness direction, are grouped togetherand used to define one amalgamated physical response function for each series of elements in a 2Ddesign domain; (c) optimum designs on the layout of stiffeners attached to a panel or sandwichedbetween two panels are obtained using MIST from the grouped 3D elements. Several numericalexamples are presented to demonstrate the effectiveness of the proposed approach in designingpractical stiffener topology. By using representative volume element and repetitive boundaryconditions as well as loading combinations, designs of stiffener are obtained for selected stiffenedand sandwiched plates under chosen static loading.

Warstwa wierzchnia elementów wycinanych wysokociśnieniowym strumieniem wodnościernym

Warstwa wierzchnia elementów wycinanych wysokociśnieniowym strumieniem wodnościernym

Effect of the geometry and microstructural heterogeneity of ferritic elements on the magnetic hysteresis loop

This study focuses on toroidal elements having dimensions 3.1 × 1.5 × 1.4 mm and composition, mol.%: 37.6 Fe2O3, 38.1 MnO, 9.3 MgO, 11.7 ZnO, 3.3 CaO. It is shown that increase of the innerto-outer diameter ratio of the toroids leads to higher squareness of the hysteresis loop. The geometry of the samples and gradients of coercive force H c caused by structural heterogeneity influence the shape and squareness of the hysteresis loop. In the absence of oxidation, the surface layers of elements have lower H C than the inner ones because their magnetic reversal begins in weaker fields, promoting smooth transition from the horizontal to descending section of the hysteresis loop. The nonequilibrium oxidation of elements cooled down to the hardening temperature leads to an increase in H c: to a greater extent on the surface and to a smaller extent inside the toroids. As a result, the upper half of the descending branch of the hysteresis loop becomes steeper, while the lower half more shallow. Isothermal holding at the hardening temperature reduces the gradients of H c and the squareness of hysteresis loop.

Analysis of a Space-Time Discretization for Dynamic Elasticity Problems Based on Mass-Free Surface Elements

In this paper, a new space-time discretization is proposed which is based on a modified mass matrix. The mass associated with a surface layer of elements is redistributed such that the inertia at the boundary is removed. This approach is motivated by the observation that standard space-time discretization schemes applied to dynamic contact problems yield spurious oscillations. A widely used approach for the numerical simulation of these problems is based on Lagrange multipliers which represent the contact stresses. But the algebraic contact conditions in combination with the inertia volume terms often yield nonphysical results for the contact stresses, and the stability of the algorithm can be lost. Our modified matrix is calculated via nonstandard quadrature formulas that require no extra computational effort. In addition, the conservation properties of the underlying algorithm are carried over to the modified method, and the standard optimal a priori estimates are still satisfied. Numerical examples confirm the optimality of the approach and its stabilization effect applied to contact problems.

Residual stressed condition and the moduluses of elasticity of the surface layers of elements of structures

Residual stressed condition and the moduluses of elasticity of the surface layers of elements of structures