Grinding and fine finishing of future automotive powertrain components

The automotive industry is undergoing a major transformation driven by regulations and a fast-paced electrification. A critical analysis of technological trends and associated requirements for major automotive powertrain components is carried out in close collaboration with industry – covering the perspectives of OEMs, suppliers, and machine builders. The main focus is to review the state of the art with regard to grinding, dressing, texturing and fine-finishing technologies. A survey of research papers and patents is accompanied by case studies that provide further insights into the production value chain. Finally, key industrial and research challenges are summarized

Surface Integrity of Case-hardened Gears - with Particular Reference to Running-in and Micropitting

A gearbox with gears of different sizes is part of a vehicle transmission system and plays an important part in transmitting the engine power to the wheels. The efficient energy transmission highly relies on the performance of gears. Together, the mesh efficiency and durability determines the performance of gears.The hard finishing of gear surfaces by means of different methods; grinding, honing and superfinishing etc., produces unique characteristics in terms of surface roughness, microstructure and residual stresses. These characteristics of tooth affect the gear performance. Running-in process is known to alter them along with surface chemistry and presets the gear for service. This fact creates an interest to understand the initial running-in with the purpose to improve the performance of gears. Thus, this study addressed, the influence of running-in on the evolution of surface characteristics generated by the mentioned methods, and how they developed further during initial usage, represented by efficiency test. Gears tested in a FZG back-back test rig were characterized by combining different analytical techniques. These included scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Surface roughness was found to be the most influential factor and virtually all changes were confined to ~5 μm below the surface. The running-in process smoothened the surface asperities through plastic deformation and the severity of deformation increased with load. Micropitting was also associated with asperity deformation and hence only seen in ground and honed gears, while being absent for superfinished gears. Micropitting was promoted by higher running-in load and this trend continued for subsequent efficiency testing. The running-in load also promoted the deformation bands frequently found in connection with the cracks. Compressive residual stresses beneficial for fatigue life varied between finishing methods, highest stresses recorded for honed gears. The stresses differed between profile and axial direction after manufacturing and, reached similar levels after efficiency testing, but remained compressive throughout the test. The initial increase in compressive residual stresses was linked to retained austenite transformation and its later decrease to crack formation. The indicated tribofilm formation was connected to the surface roughness and promoted by running-in load.Micropitting is a surface contact fatigue failure that occurs in all types of gears. This failure mechanism was also investigated from material perspective. Gears were tested in a sequence from 200 to 2.2 x 107 cycles. The micropitting initiated due to the deformation of asperities and associated microstructural changes; plastically deformed regions (PDR) and deformation bands (thin martensite lath with epsilon carbides precipitated at boundaries). These structural changes started already within 200 cycles and cracks occurred after 2000 cycles, signifying that micropitting can initiate already after short period of operation. Thus, the running-in of gears from materials perspective can be as short as 2000 cycles. The findings presented are expected to contribute to the technical and industrial aims for optimized gear preparation

Recent developments in sustainable manufacturing of gears: a review

Abstract: Environment awareness is of the utmost importance to all socially responsible manufacturers. To be competitive on a global scale manufacturing needs to be aligned with various strict environmental regulations. The manufacturing industry at large is striving to improve productivity and product quality while maintaining a clean and sustainable environment. This can only be achieved by adopting sustainable techniques of manufacturing which include minimizing the number of manufacturing steps by employing advanced and alternative methods, environment-friendly lubricants and lubrication techniques while machining, reducing wastage, active waste management and minimizing energy consumption etc. Gear manufacturing industries, the major service providers to all other industrial and manufacturing segments are also focusing on to implement the techniques targeting overall sustainability. Some of the recent developments to achieve sustainability in gear manufacturing can be summarized as reducing the use of mineral-based cutting fluids by employing alternative lubrication techniques i.e. minimum quantity lubrication (MQL) and dry machining, material saving, waste reduction, minimizing energy consumption and maintaining economic efficiency by reducing the number of gear manufacturing stages (eliminating the necessity of finishing processes) by utilizing advanced methods such as gear rolling and wire electric-discharge machining (WEDM), and finally increasing productivity by minimizing tool wear at high gear cutting speeds through the use of alternative tool materials and coatings. This paper reviews and amasses the current state of technology for sustainable manufacturing of gears and also recommends ways to improve the productivity and quality while simultaneously ensuring environmental sustainability

Machining and grinding of ultrahigh-strength steels and stainless steel alloys

Machining and grinding of ultrahigh-strength steels and stainless steel alloy

Професійна технічна термінологія у галузі машинобудування

Рецензенти: Д. В. Криворучко – доктор технічних наук, доцент, професор кафедри технології машинобудування, верстатів та інструментів Сумського державного університету; В. І. Шатоха – доктор технічних наук, професор, проректор із науково-педагогічної роботи Національної металургійної академії України.Навчальний посібник є важливою формою міждисциплінарної та міжвузівської інтеграції, створений для зацікавлення студентів у якісному та поглибленому вивченні спеціальних дисциплін та професійної англійської мови, розвитку вмінь самостійної роботи і навичок при написанні та оформленні науково-дослідних робіт, активізації пізнавальної й дослідницької діяльності, стимулює наукові пошуки, обмін досвідом засобами англійської мови у галузі машинобудування. Навчальний посібник призначений для інженерно-технічних і науково-педагогічних працівників, аспірантів і студентів інженерних спеціальностей вищих навчальних закладів.Розроблено в рамках виконання проекту Темпус «Модернізація вищої інженерної освіти в Грузії, Україні та Узбекистані відповідно до технологічних викликів» (ENGITEC 530244-TEMPUS-1-2012-1-SE-TEMPUS-JPCR

Професійна технічна термінологія у галузі машинобудування

Рецензенти: Д. В. Криворучко – доктор технічних наук, доцент, професор кафедри технології машинобудування, верстатів та інструментів Сумського державного університету; В. І. Шатоха – доктор технічних наук, професор, проректор із науково-педагогічної роботи Національної металургійної академії України.Навчальний посібник є важливою формою міждисциплінарної та міжвузівської інтеграції, створений для зацікавлення студентів у якісному та поглибленому вивченні спеціальних дисциплін та професійної англійської мови, розвитку вмінь самостійної роботи і навичок при написанні та оформленні науково-дослідних робіт, активізації пізнавальної й дослідницької діяльності, стимулює наукові пошуки, обмін досвідом засобами англійської мови у галузі машинобудування. Навчальний посібник призначений для інженерно-технічних і науково-педагогічних працівників, аспірантів і студентів інженерних спеціальностей вищих навчальних закладів.Розроблено в рамках виконання проекту Темпус «Модернізація вищої інженерної освіти в Грузії, Україні та Узбекистані відповідно до технологічних викликів» (ENGITEC 530244-TEMPUS-1-2012-1-SE-TEMPUS-JPCR

Micropitting and martensite decay in gears

PhD ThesisMicropitting is a type of surface contact fatigue often observed in gears and rolling element bearings operating under mixed or elastohydrodynamic lubrication (EHL). Once initiated, micropitting will lead to the catastrophic failure of the affected components which then requires unplanned industrial shutdowns to allow for their replacement. Micropitting in carburised gears has become a major concern in the wind power industry and other sectors where gears operate at relatively high loads and relatively slow speeds. It occurs most often in parallel axis gears (spur and helical) but it was also reported in other types of gears such as spiral bevel gears. An important feature that has been observed in bearings damaged by micropitting was the transformation of the initial microstructure. The change in microstructure, known as martensite decay, consists in the development of a new phase known as Dark Etching Region (DER) due to its appearance in reflected light microscopy. This microstructural change which has also been observed in gears leads to changes in the mechanical properties in the affected regions with implications on the initiation and propagation of the cracks leading to the formation of micropits. The fatigue life of gears can be extended by controlling the formation of micropits but this requires an in-depth understanding of the micropitting mechanism. The aim of this project was to identify and characterise the microstructural changes accompanying micropitting in gears and to develop a micropitting mechanism which describes the formation of the micropits. The microstructure has been investigated by electron microscopy techniques such as Scanning Electron Microscopy (SEM), Electron Backscattered Diffraction (EBSD), and Transmission Electron Microscopy (TEM). Nanoindentation was used to determine the mechanical properties of the affected regions. The proposed micropitting mechanism is based on the results from the above investigations as well as Density Functional Theory (DFT) calculations of material properties combined with Finite Element Analysis (FEA) of the contact region

Tribological optimisation of the internal combustion engine piston to bore conjunction through surface modification

Internal combustion (IC) engines used in road transport applications employ pistons to convert gas pressure into mechanical work. Frictional losses abound within IC engines, where only 38- 51% of available fuel energy results in useful mechanical work. Piston-bore and ring-bore conjunctions are fairly equally responsible for circa 30% of all engine friction - equivalent to 1.6% of the input fuel each. Therefore, reduction in piston assembly friction would have a direct impact on specific performance and / or fuel consumption. In motorsport, power outputs and duty cycles greatly exceed road applications. Consequently, these engines have a shorter useful life and a high premium is placed on measures which would increase the output power without further reducing engine life. Reduction of friction offers such an opportunity, which may be achieved by improved tribological design in terms of reduced contact area or enhanced lubrication or both. However, the developments in the motorsport sector are typically reactive due to a lack of relative performance or an ad-hoc reliance, based upon a limited number of actual engine tests in order to determine if any improvement can be achieved as the result of some predetermined action. A representative scientific model generally does not exist and as such, investigated parameters are often driven by the supply chain with the promise of improvement. In cylinder investigations are usually limited to bore surface finish, bore and piston geometrical form, piston skirt coatings and the lubricant employed. Of these investigated areas newly emerging surface coatings are arguably seen as predominate. This thesis highlights a scientific approach which has been developed to optimise piston-bore performance. Pre-existing methods of screening and benchmarking alterations have been retained such as engine testing. However, this has been placed in the context of validation of scientifically driven development. A multi-physics numerical model is developed, which combines piston inertial dynamics, as well as thermo-structural strains within a thermoelastohydrodynamic tribological framework. Experimental tests were performed to validate the findings of numerical models. These tests include film thickness measurement and incylinder friction measurement, as well as the numerically-indicated beneficial surface modifications. Experimental testing was performed on an in-house motored engine at Capricorn Automotive, a dynamometer mounted single-cylinder ‘fired’ engine at Loughborough University, as well as on other engines belonging to third party clients of Capricorn. The diversity of tests was to ascertain the generic nature of any findings. The multi-physics multi-scale combined numerical-experimental investigation is the main contribution of this thesis to knowledge. One major finding of the thesis is the significant role that bulk thermo-structural deformation makes on the contact conformity of piston skirt to cylinder liner contact, thus advising piston skirt design. Another key finding is the beneficial role of textured surfaces in the retention of reservoirs of lubricant, thus reducing friction

Advances in CAD/CAM/CAE Technologies

CAD/CAM/CAE technologies find more and more applications in today’s industries, e.g., in the automotive, aerospace, and naval sectors. These technologies increase the productivity of engineers and researchers to a great extent, while at the same time allowing their research activities to achieve higher levels of performance. A number of difficult-to-perform design and manufacturing processes can be simulated using more methodologies available, i.e., experimental work combined with statistical tools (regression analysis, analysis of variance, Taguchi methodology, deep learning), finite element analysis applied early enough at the design cycle, CAD-based tools for design optimizations, CAM-based tools for machining optimizations

Micropitting and related phenomena in case carburised gears

Micropitting is a form of surface contact fatigue encounteredin bearingsa nd gears, under lubricating conditions, which lead to their premature failure. All gears are susceptible to micropitting, including spur, helical and bevel. Micropitting can occur with all heatt reatmentsa ppliedt o gearsa nd with both, synthetica nd mineral lubricants. It can occur after a relatively short period of operation and, after a certain number of cycles,g earsn eedt o be replacedd ue to the increasedn oisea nd vibrations causedb y the deviations of the tooth profile. Continuing operation of affected gears can lead to a catastrophic type of failure (i. e., tooth breakage). These considerations explain the increasing current interest in micropitting. It has been reported that micropitting in bearings is associated with a specific microstructural transformation in steel, i. e. martensite decay. However, to the authoes knowledge, this transformation has not been reported in gears. In the present work, extensive metallurgical investigations have been carried out and they revealed that the same transformation occurs in gears. The aim of this project was to describe the mechanism of micropitting by taking into account the influence of several controlling factors such as, material, surface finish, lubricant, load, temperature,s peeda nd, slide-to-roll ratio. Their influence is assessed with a fractional factorial experimentadl esign.S everaln on-destructivete chniquesh ave been used in order to monitor the specimen condition during and after running, such as X-ray diffraction, optical profilometry, light microscopy. The mechanical properties of the products of martensite decay, known as dark etching regions, white etching bands and butterflies are highly relevant to the fatigue behaviour of the steel. Nanoindentation and AFM techniquesh aveb eenu sedt o determinet hesep roperties. A micropitting mechanism correlated with the mechanism of martensite decay in gears is suggestedb asedo n thesea nalyses.EThOS - Electronic Theses Online ServiceNewcastle University Research Committee : Caterpillar Inc. : Design Unit - Gear Technology CentreGBUnited Kingdo