Refinement of the rail–wheel contact pair to improve rail–wheel interaction conditions for railway vehicles with an increased axle load

At present, one of the global trends in railway transport development, which becomes clearer and clearer, is increasing the axle load of freight cars, which gives a considerable economic benefit. In this connection, of importance is not only the car design, but also the car capacity utilization factor: the higher this factor, the more economically efficient the car use. Because of this, one of the priority global lines in increasing the volume of fright traffic and the railway operation efficiency is increasing the carrying capacity of freight cars. Preparing the railways for cars with increased axle loads calls for the development of measures to decrease the track deformability, in particular by choosing appropriate wheel and rail profiles. The aim of this work was to develop recommendations on refining the wheel?rail contact pair to improve curve negotiation by railway vehicles with an increased axle loads on the Ukrainian railways. This paper presents the proprietary R-ITM wear-resistant railhead profile. The effect of the new profile on wheel?rail interaction in negotiating a curve of radius 300 m at a constant speed was studied for different cars. In doing so, emphasis was on wheel?rail interaction for a new-generation freight car on 18-9817 trucks with an axle load increased to 36 tf. The studies conducted made it possible to formulate the following recommendations: to improve curve negotiation by railway vehicles with increased axle loads, reduce the adverse effect on the track and improve traffic safety, new proprietary contact pair profiles are recommended: the ITM-73-03 wheel profile for cars, and the R-ITM railhead profile for outer rails together with the standard R65 railhead profile for inner rails.

Method for assessing the thermophysical properties of the contact pair ‘tool – steel workpiece’

To The analysis of methods for evaluating the properties of contact pairs “hard -alloy coated tool-steel billet” is carried out in order to use them to increase the reliability of the choice of turning modes in the generations of CNC systems equipped with technological intelligence. It is proposed to use the value of the thermo-emf of the test pass as an indirect indicator of the properties of contact pairs composed of a coated carbide tool and a processed steel billet. Models for calculating the cutting speed based on a given tool durability period of a coated carbide tool and predicting the actual cutting tool durability period for given processing conditions are proposed by introducing into their structure an additional informative value about the properties of each contact pair - the thermo-EMF of the test pass. The conducted resistance tests of various carbide plates during the processing of P-group steels showed sufficient reliability of the proposed dependences.

Bio-tribological behavior of articular cartilage based on biological morphology

Artificial hemiarthroplasty is one of the effective methods for the treatment of hip joint diseases, but the wear failure of the interface between the hemi hip joint material and articular cartilage restricts the life of the prosthesis. Therefore, it is important to explore the damage mechanism between the interfaces to prolong the life of the prosthesis and improve the life quality of the prosthesis replacement. In this paper, the creep and bio-tribological properties of cartilage against PEEK, CoCrMo alloy, and ceramic were studied, and the tribological differences between “hard–soft” and “soft–soft” contact were analyzed based on biomorphology. The results showed that with the increase of time in vitro, the thickness of the cartilage membrane decreased, the surface damage was aggravated, and the anti-creep ability of cartilage was weakened. Second, the creep resistance of the soft–soft contact pair was better than that of the hard–soft contact pair. Also, the greater the load and the longer the wear time, the more serious the cartilage damage. Among the three friction pairs, the cartilage in PEEK/articular cartilage was the least damaged, followed by CoCrMo alloy/articular cartilage, and the most damage was found in ceramic/articular, indicating that the soft–soft friction pair inflicted the least damage to the cartilage.

METHODS FOR ESTIMATING THERMFISICAL PROPERTIES OF THE "TOOL - STEEL WORKPIECE" CONTACT PAIR AND THE POSSIBILITY OF THEIR USE IN CALCULATION OF THE PARAMETERS OF THE TURNING PROCESS

The analysis of methods for assessing the properties of contact pairs "hard alloy tool - steel workpiece" with the aim of improving the reliability of the choice of turning modes in generations of CNC systems equipped with technical intelligence. The models for calculating the cutting speed, the cutting force, the value of roughness Ra, have been corrected by introducing into their structure an additional informative value about the properties of each contact pair - the thermoEMF of the trial cut.

A lubrication contact pair model for simulating gear micro-pitting damage characteristics based on contour integral

A new two-dimensional finite element model of a lubricated contact pair, based on a contour integral, is proposed to investigate the formation of micro-pitting on gear tooth surfaces. Meanwhile, the contact properties and elasto-hydrodynamic lubrication (EHL) conditions of the gears are considered in the lubricated contact pair model. Then, the stress intensity factors (SIFs) KI and KII and the propagation angle θ C at the crack tip are analyzed by ABAQUS software. Next, the equivalent SIF Kσ can be calculated according to the maximum tangential stress (MTS) criterion, which is often used as the criterion for crack propagation. Considering the effect of a moving contact, the crack more easily propagates under the load x0/ b = −0.895. Furthermore, the pit shapes and variation of stress intensity factor are determined for various combinations of initial crack length a0 and angle β. The results show that longer germinated cracks propagate in areas that are deeper below the tooth surface. And the total length of final crack increases with the initial length and germination angle. These research results provide theoretical support for contact fatigue life analysis and meshing stiffness calculations of micro-pitting gears.