Search

The features of the quantitative determination of the reliability of the results of the acoustic- emission (AE) method of monitoring and diagnostics are considered. It has been established that the traditional way of defining reliability via the probability of a controlled parameter falling into a certain interval sometimes suffers from informational underdetermination. It is shown that taking into account the probabilistic and information aspects of the assessment of reliability makes it possible to unambiguously link the concept of reliability of the results of testing and diagnostics with the amount of information obtained in the course of the inspection or diagnostics operation itself. Examples of practical determination of information reliability of the results of AE method are given.

The paper presents numerical and experimental burst pressure evaluation of the gas seamless hot-rolled steel pipe. The main goal was to estimate mechanical toughness of pipe wrapped with composite sleeve and verify selected sleeve thickness. The authors used a nonlinear explicit FE code with constitutive models which allows for steel and composite structure failure modelling. Thanks to the achieved numerical and analytical results it was possible to perform the comparison with data received from a capacity test and good correlation between the results were obtained. Additionally, the conducted analyses revealed that local reduction of pipe wall thickness from 6 mm to 2.4 mm due to corrosion defect can reduce high pressure resistance by about 40%. Finally, pipe repaired by a fibre glass sleeve with epoxy resin with 6 mm thickness turned out more resistant than an original steel pipe considering burst pressure.

Serviceability of metal-polymeric "dry-friction" sliding bearings depends on many parameters, including the rotational speed, friction coefficient, thermal and mechanical properties of the bearing system and, as a result, the value of contact temperature. The objective of this study is to develop a computational model for the metallic-polymer bearing, determination on the basis of this model temperature distribution, equivalent and contact stresses for elements of the bearing arrangement and selection of the optimal parameters for the bearing system to achieve thermal balance. Static problem for the combined sliding bearing with the account of heat generation due to friction has been studied in [1]; the dynamic thermoelastic problem of the shaft rotation in a single and double layer bronze bearings were investigated in [2, 3].

The serviceability of polymer dry sliding bearings is governed by a number of parameters, such as the rotational velocity of the shaft, the friction coefficient, еру thermal and mechanical properties of bearing members, and hence, the resulting contact temperatures. This work was aimed at developing a calculation model of the operation of a two-layer polymer dry sliding bearing, determining the temperatures distributions and the equivalent and contact stresses in bearing members, and choosing the optimum parameters of the bearing system for which heat balance is achieved.

Friction and antifriction composite materials of multilayer structure [1] have recently become very popular in the engineering industry. Antifriction materials are widely used in sliding bearings, and friction materials are widely used in brakes. In the first case, the friction forces between the contacting surfaces are negligible, but in the second case, they are rather large.

The contact problem of the motion of a punch taking into account the heat released due to friction between the punch and a very thick elastic strip is considered. The contact problem of the theory of elasticity regarding a moving punch was previously investigated both ignoring [1, 2] and taking into account [3, 4] the forces of friction and the heat release. Here, unlike [3, 4], when solving the free quasistationary problem of thermoelasticity in a moving system of coordinates a relation is proposed between the coefficient of friction and the temperature. Particular attention is given to the problem of the possibility of a thermal explosion [5–11] or a sharp change (a bifurcation) in the contact temperatures. It is shown that a loss in the quasi-stationary thermoelastic stability occurs if the coefficient of friction increases linearly with the temperature. The proposed model can explain, to a first approximation, the avalanche-type wear of different moving components, for example, thin piston rings, due to their overheating.

Fredholm integral equations of the second kind are obtained and investigated for various boundary conditions on one edge of a wedge which enables one to represent the corresponding Green's functions by integrals of Neumann series in powers of (1 − 2v). Contact problems of the action of a punch in the form of an elliptic paraboloid on an elastic spatial wedge are studied. The asymptotic method of “large λ” [1] is used to solve the integral equations of these problems. The results of the numerical analysis are compared with a well-known contact problem for a half-space [2, 3].