Estimation of strength properties of functionally graded structures with elliptical stress concentrators

Purpose: The purpose of this paper is to elaborate new calculation schemes for evaluating the strength parameters of railway rolling stock parts with non-local properties of surface layers in the presence of elliptical stress concentrators. Design/methodology/approach: Using the proposed approaches of developed mathematical modelling and open software for calculating FEniCS, it were established the most dangerous angles of stress concentrator orientation and the required thickness of the hardened zones of parts, which ensures their minimum softening during operation. Findings: It is shown that for an elliptical stress concentrator with any orientation angle, there is a certain key size of surface hardening thickness, the exceeding the value of which does not have influence on the operational strength of the parts, but rise the price of technological operations. Research limitations/implications: In this paper proposes a method for computation the impact of the orientation of the surface elliptical stress concentrators on the contact strength of parts under conditions of dominate friction power loads. Practical implications: The obtained results were used to set the modes of plasma hardening, which increase the contact strength of railway parts with elliptical stress concentrators. Originality/value: Using the approaches of contact mechanics, mathematical and computer modelling, methods of controlling the contact strength of the parts with the surface elliptical stress concentrators were proposed for the first time.

Improvement of mechanical processing equipment due to synthesis of initial circuits of outpole gears

The synthesis of the initial contours of the teeth of out-of-pole gears on parallel axes according to the criterion of the contact strength of the working surfaces is presented, the geometric parameters of the original contours of the gear teeth with high contact strength of the working surfaces are determined. An assessment was carried out according to the following performance criteria: power loss in the engagement, the thickness of the oil layer, the specific work of friction forces, galling. transmission.

ANALYSIS OF METHODS FOR CALCULATING SPUR GEAR FOR DEEP CONTACT STRENGTH

Spur gear is an integral part of transport and technological machines structure. To increase the load ability of the spur gear, chemical heat treatment of the working cogs surfaces is used. Spur gear with chemical heat treatment must be checked for deep contact strength. The article analyzes various methods (according to GOST 21354-87, methods using the generalized criterion of the limit state for structurally inhomogeneous material by Lebedev-Pisarenko, methods from the handbook describing reducers of power machines etc.) for calculating spur and helical gearing for deep contact strength. The author presents all necessary formulas and graphs for the implementation of each methods, and compares the calculations results of these methods with the results of experimental studies of cemented cylindrical rollers for deep contact destruction.

Гистерезис в адгезионном контакте при изменении направления сдвига: эксперимент и феноменологическая модель

A phenomenological model is proposed that describes hysteretic behavior of an adhesive contact between a soft elastomer and a rigid indenter when the direction of the indenter shear is changed. The model takes into account the increase of contact strength with contact time. The dependences of the elastic force and contact radius on the indentation depth were obtained. It is shown that the adhesive strength of the contact increases with an increase in the indentation depth. An experiment on the indentation of a steel spherical indenter into a rubber sheet of a fixed thickness was carried out. A qualitative agreement between the experimental and theoretical results is shown.

Technological support of wear-resistance and contact strength of production tools alignment elements by method of laser alloying

The technological potentialities of laser alloying are considered for operation properties increase of supporting prisms in machine equipment. The information on techniques used is shown: methods for alloying component introduction, a lute structure, modes of laser working are presented. Test results of coatings obtained and recommendations for their use are presented.