ANALYSIS OF CONTACT STRESSES AND SLIP IN POWER SHIFT GEARINGS USING MULTI -CRITERION OPTIMISATION

The work analysed contact stresses and slippage occurring in specific toothed pairs of two power shift gearings with eight ratios. The analysed gearings have ratios of identical values. Differences in contact stresses and slippage values within individual toothed pairs of both gearings (at same values of input torque and engine speed) result from the internal configuration of the kinematic chains created by the toothed gears within individual gear ratios. The analysis included 5 characteristic contact points within the tooth engagement area. They were selected analytically depending on geometrical parameters of gears that constitute the toothed pair. Using computer-assisted design works that employ multi-criterion optimisation, it is possible to minimize slippage and take reasonable advantage of the fatigue contact durability of the material that was used for producing the toothed gears.

Tribological Behavior of Polymers and Polymer Composites

This chapter means to explain the tribological behavior of polymer-based materials, to support a beneficial introducing of those materials in actual applications based on test campaigns and their results. Generally, the designers have to take into consideration a set of tribological parameters, not only one, including friction coefficient, wear, temperature in contact, contact durability related to application. Adding materials in polymers could improve especially wear with more than one order of magnitude, but when harder fillers are added (as glass beads, short fibers, minerals) the friction coefficient is slightly increased as compared to neat polymer. In this chapter, there are presented several research studies done by the authors, from which there is point out the importance of composite formulation based on experimental results. For instance, for PBT sliding on steel there was obtained a friction coefficient between 0.15 and 0.3, but for the composite with PBT + micro glass beads, the value of friction coefficient was greater. Adding a polymer playing the role of a solid lubricant (PTFE) in these composites and also only in PBT, decreased the friction coefficient till a maximum value of 0.25. The wear parameter, linear wear rate of the block (from block-on-ring tester) was reduced from 4.5 μm/(N⋅km) till bellow 1 μm/(N⋅km) for a dry sliding regime of 2.5…5 N, for all tested sliding velocities, for the composite PBT + 10% glass beads +10% PTFE, the most promising composite from this family of materials. This study emphasis the importance of polymer composite recipe and the test parameters. Also there are presented failure mechanisms within the tribolayer of polymer-based materials and their counterparts.

Analysis of friction interaction and optimisation of detail surface hardening technologies using non-local mathematical models

Purpose: The aim of the work is to build physically sound engineering and design schemes that take into account the behaviour of polycrystalline metal systems under intense loads and allow optimization of surface treatment technologies to increase the operational reliability parameters of products. Design/methodology/approach: Using the approaches of thermodynamics, a methodological scheme is proposed, on the basis of which it is possible to optimize surface engineering technologies to increase the contact durability of details. Findings: It was found that the maximum increase in the durability of steel 40X13 (AISI 420) is achieved with thermocyclic ion nitriding in a cycle of ± 50°C, and the minimum with isothermal nitriding. Research limitations/implications: In this paper, the optimization of technological solutions to increase the contact durability of structural elements operating under prevailing power loads is given. Practical implications: Using the proposed mathematical relationships, optimal technological regimes of ion-plasma nitriding were established for various operating conditions, under which the maximum durability and wear resistance of 40X13 (AISI 420) steel are ensured. Originality/value: The paper proposes an approach to the formation of functionally gradient surface layers of steel with specified operational parameters when choosing optimal nitriding technology modes based on nonlocal mathematical models.

Determination of the optimal parameters of the structure of functional gradient materials using mathematical modelling approaches

Purpose: Functioning of mechanical friction systems largely depends on the characteristics of the structure of their surface layers. By controlling these parameters, it is possible to significantly adjust the reliability and durability of parts under the conditions of contact interaction. Design/methodology/approach: he proposed approach, which is based on the principle of nonlocality of the operational properties of materials, allows determining the optimal microhardness values of the surface layers and the gradient of this parameter, at which the contact durability of friction pair elements significantly increases. Findings: It is established that by adjusting the ratios of the surface strength of materials and its gradient, it is possible to achieve a significant increase in the operational parameters of friction units. Practical implications: The engineering relationship considered in the work allows to establish functional distributions of microhardness in the structure of surface layers, at which their wear reaches minimum values. Originality/value: Mathematical approaches are proposed, which allow determining the parameters of the structure of the surface layers of parts to increase their durability under conditions of friction contact loads.

ПОДВІЙНА ХІМІКО-ТЕРМІЧНА ОБРОБКА ЗУБЧАСТОГО КОЛЕСА ІЗ СТАЛІ ВКС-5

The process of the double chemical-thermal treatment (DCTT) a gear made of heat-resistant steel VKS-5 is quite common and makes it possible to obtain secondary hardness. Double or combined chemical-thermal treatment is designed to increase the contact durability of steels by nitriding final finished parts that these were carburizing, hardened and ground. Comparison of the process of double chemical-thermal treatment with traditional methods of chemical-thermal treatment(CTT) carburizing and nitriding. Object of the study is a gear wheel treated with the DCTO method, after it was compared the hardness of the wheel past the DCTO using gas nitriding and liquid, with other similar CTT processes such as nitriding and carburizing and nitrocarburizing the results were a graph of hardness and the depth of the strengthened layer for each of the processes. Discussion of the developed technology for the preparation of double chemical-thermal treatment and the results of studies on the use of dispensing methods for obtaining DCTO. Efficiency is justified by metallographic studies of the developed technology. Also, metallographic studies have shown the need to control the surface layer the E-phase is formed due to which it is possible to substantially increase the hardness of the surface while preserving the structure of the entire material without cracking thereby providing increased contact durability. We also consider the possibility of using ion-plasma equipment, which allows to significantly increase the speed of the process, control the thickness of the layer of surface phases and also makes it possible to additionally apply the method of surface deformation to create compressive stresses on the surface. This technology allows to obtain a surface combining the advantages of nitriding and carburizing, excluding useing harmful substances affecting a health and ecology, and also economically more beneficial than nitrocarburizing. DCTT can be used to increase the contact endurance of the gear wheels in a large module, and eliminating the need for further machinary treatment of the surface layer after DCTT.

ANALYSIS INTO THE INFLUENCE OF SELECTED TOOTHED GEAR PARAMETERS ON THE VALUE OF SLIPPAGE AND CONTACT STRESSES IN A CYLINDRICAL GEARBOX

The paper presents issues concerning the geometrical and durability calculations of power shift gearboxes with multi-criterion optimization, using proprietary computer software. Among many parameters influencing the value of slippage and contact stresses, the flank ratio at P-0 correction and P correction, the value of the flank angle, and the module value were analysed. The slippage was analysed at Point B1, which belongs to the beginning of the single tooth engagement area, as well as in Point B2, where the single tooth engagement area ends. Contact stresses were calculated at Point C, which is the pitch point. Their values were referenced to experimentally determined fatigue contact durability σHlim.