Properties and environmental dependencies of mechatronic components like gear-drives and motors i... more Properties and environmental dependencies of mechatronic components like gear-drives and motors impact the overall performance of automated Production Systems. These properties, often in the form of characteristic curves, are only accessible from suppliers' documents, like operating instructions or online catalogs. The proposed SysML' profile integrates artifacts from SysML and UML into disciplinary views. It includes a reference mechanism to REXS (standard for gear properties) and ECLASS (standard for product data like UNSPSC) to overcome the semantic inconsistency of component properties and inclusion of curves. A metamodel is used for a more precise presentation of the proposed reference mechanism. Due to the static nature of a profile, a Business Process Modeling Notation is used to dynamically illustrate the benefits of SysML' in the workflow.
Purpose Numerous metals can be processed using the additive manufacturing process laser-based pow... more Purpose Numerous metals can be processed using the additive manufacturing process laser-based powder bed fusion of metals (PBF-LB/M, ISO/ASTM 52900). The main advantages of additive manufacturing technologies are the high degree of design freedom and the cost-effective implementation of lightweight structures. This could be profitable for gears with increased power density, combining reduced mass with considerable material strength. Current research on additively manufactured gears is focused on developing lightweight structures but is seldom accompanied by simulations and even less by mechanical testing. There has been very little research into the mechanical and material properties of additively manufactured gears. The purpose of this study is to investigate the behavior of lightweight structures in additively manufactured gears under static loads. Design/methodology/approach This research identifies the static load-carrying capacity of helical gears with different lightweight str...
Shear cutting is used for manufacturing various parts ranging from e.g. simple washers to complex... more Shear cutting is used for manufacturing various parts ranging from e.g. simple washers to complex gears. The latter are typically subjected to cyclic loading and fail foremost due to fatigue damages. Hereby, the parts lifetime is mainly determined by: the geometry, the applied load, the material, the hardness, the roughness and the residual stress state. While numerous research works deal with the influence of the process parameters on the hardness and the parts geometry, the influence of the process parameters on the residual stress state and on the resulting fatigue strength has not been investigated in detail, yet. In an earlier publication, suitable shear cutting techniques, which allow to achieve a high amount of clean-cut and a favorable residual stress state were compared. In this paper, the influence of the process parameters on the residual stress state and the resulting bending fatigue strength are addressed. To simulate the bending stress occurring in the tooth root, C-shaped specimens were manufactured by different blanking techniques. The die-clearance and punch and die edge radii were varied with these blanking techniques. After measuring the cut-surface geometry, the hardness distribution and the surface roughness, the fatigue strength was determined in a pulsating test rig. By carrying out residual stress measurements using x-ray diffraction and simulating the material flow behavior using the Finite-Element-Method, basic mechanisms, which are influencing the residual stress state and the resulting bending fatigue strength, were identified and will be presented and discussed in the paper.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The International Journal of Advanced Manufacturing Technology, Nov 19, 2022
The v-ring indenters and their configurations play a major role in the fineblanking process, dire... more The v-ring indenters and their configurations play a major role in the fineblanking process, directly influencing component quality and characteristics. While past studies regarding residual stresses of blanked components focused mainly on the use of a pair of v-rings, so far no efforts were undertaken to compare different v-ring setups, deducing tool design guidelines and enabling possible cost savings. Therefore, a comparative study of different v-ring indenter setups and their influence on cut surface parameters, surface hardness and induced residual stresses of the produced components was performed. The obtained results indicate a minor influence of blank holder-sided v-rings on the observed component characteristics in comparison to indenters situated on the die leading to recommendations with regard to cost-efficient tool design.
A computational fluid dynamics (CFD) model of the thermal elastohydrodynamically lubricated (EHL)... more A computational fluid dynamics (CFD) model of the thermal elastohydrodynamically lubricated (EHL) line contact problem has been developed for the purpose of exploring the physical processes that occur inside a thin EHL film subjected to shearing motion. The Navier-Stokes equations are solved by using the finite volume method (FVM) in a commercial CFD software, ANSYS Fluent. A set of user-defined functions (UDF) are used for computing viscosity, density, heat source, temperature of moving surfaces and elastic deformation of the top roller according to well-established equations commonly used in the EHL theory. The cavitation problem is solved by taking into account multiphase mixture flow. The model combinations of Houpert and Ree-Eyring and of Tait and Carreau were used for modeling the non-Newtonian behavior of Squalane and the results were compared. Both rheological models suggest the existence of shear-band and plug-flow at high fluid pressure. Due to the differences in viscosity at GPa-level pressure, the chosen model has substantial influence on the computed shear stress and temperature distributions in the high-pressure region. This shows the importance of using correct rheology information in the whole range of pressure, temperature, and shear strain rate.
Forschung Im Ingenieurwesen-engineering Research, Jun 7, 2023
Current challenges for today's industry are an increase in gear ratio in one stage, an increase i... more Current challenges for today's industry are an increase in gear ratio in one stage, an increase in load capacity as well as an increase in efficiency compared to standard gears. The standard tooth profile for cylindrical gears is an involute. This tooth profile has certain limits for external gearings regarding its geometry, e.g., undercutting and a small radius of curvature near the base circle. Special gearings overcome these limits and offer an enormous potential in gear design through their adapted profile geometries. New manufacturing possibilities for gears, such as additive manufacturing or 5-axis milling, mean that special gears can also be produced economically. In comparison to involute gears the description of non-involute gears is often not standardized and parameters describing the geometry are not commonly defined. Thus, it is not possible to adequately determine the corresponding properties. One of these special tooth profiles is the eccentric cycloid gearing (EC gearing), in which a circular profile rolls with a profile of a trochoid equidistant. This flank geometry can provide advantages over the standard involute in certain applications. This study introduces a geometric description of the EC gearing, which is based on a defined set of parameters. Besides the geometrical parameters, parameters describing the characteristics of the gearing are proposed in accordance with the description of involute gears. This parametric description of the EC gearing enables an analytical determination of the flank, the contact geometry and load-free characteristics. With the parametric description shown and the variation of the geometry possible with it, gearings suitable for practical applications can be generated. Parameterbasierte Definition von Exzenter-Zykloiden-Verzahnungen Zusammenfassung Für die heutige Industrie ist das Offenlegen von Potenzial hinsichtlich einer höheren Übersetzung in einer Stufe, einer Erhöhung der Tragfähigkeit sowie einer Wirkungsgradsteigerung im Vergleich zu Standardverzahnungen wichtig. Evolventenverzahnungen stellen die aktuell bedeutendste Verzahnungsart für Stirnräder im Maschinenbau dar. Durch dieses Verzahnungsprofil bestehen bei Außenverzahnungen aber auch gewisse Probleme wie die Mindestzähnezahl zur Vermeidung von Unterschnitt und die kleinen Krümmungsradien in der Nähe des Grundkreises. Sonderverzahnungen können durch ihre angepassten Profilgeometrien diese Potenziale heben. Durch die neuen Herstellmöglichkeiten von Zahnrädern, wie beispielsweise additive Fertigung oder 5-Achs-Fräsen, können auch Sonderverzahnungen wirtschaftlich erzeugt werden. Im Gegensatz zur Evolventenverzahnung ist die Beschreibung von Sonderverzahnungen oftmals nicht standardisiert und die notwendigen Parameter zur Beschreibung der Geometrie sind nicht einheitlich definiert. Dadurch ist es nicht möglich, die entsprechenden Verzahnungsparameter geeignet zu bestimmen. Eine diese Sonderverzahnungen ist die Exzenter-Zykloiden-Verzahnung (EZ-Verzahnung), bei welcher ein Kreisprofil mit einem Profil einer Trochoidenäquidistante abwälzt. Durch diese Flankengeometrie können Vorteile gegenüber der standardmäßigen Evolvente in bestimmten Anwendungsfällen entstehen. Availability of data and material 'Not applicable' Code availability 'Not applicable'
Forschung Im Ingenieurwesen-engineering Research, Jan 10, 2023
Case hardening represents the most important heat treatment process to increase the load carrying... more Case hardening represents the most important heat treatment process to increase the load carrying capacity of gear components. Beside predominantly martensitic surface layers with low proportion of retained austenite, there were investigated material structures with differing properties in preceding research work. In a previous publication, the results of three variants made of the material 20MnCr5, which is typically used for gears, were presented. The reference heat treatment was a conventional carburizing with subsequent case hardening. The second variant was also gas carburized, but with a high proportion of retained austenite. The last presented variant had a bainitic structure in the surface layer. The second and the third variant showed a similar tooth root bending strength compared to the reference. The numbers of the pitting resistance were significantly higher than for the reference variant. This paper presents the results of further investigations on the influence of different microstructures on the gear load carrying capacity. For this purpose, gears made of 18CrNiMo7-6 were tested with regard to their load carrying capacity. 18CrNiMo7-6 is a case hardening steel like 20MnCr5, too, which is often applied in big gear components. The tooth root bending strength was approximately constant, whereas the pitting resistance decreased compared to the corresponding variants of the material 20MnCr5. In comparison to the carburized 20MnCr5 reference variant, only the 18CrNiMo7-6 variant with a large proportion of retained austenite showed a higher pitting resistance. The tooth root bending strength investigations took place in the cycle regime of limited life as well in the high cycle fatigue regime. The pitting resistance was only determined in the cycle regime of limited life. Einfluss des Werkstoffs auf die Festigkeitseigenschaften von Zahnrädern mit alternativen Randschichtgefügen Zusammenfassung Das Einsatzhärten stellt heute das wichtigste Wärmebehandlungsverfahren zur Steigerung der Tragfähigkeit von Getriebebauteilen dar. Neben vorwiegend martensitischen Randschichtgefügen mit einem geringen Anteil an Restaustenit wurden in vergangenen Forschungsvorhaben Randschichtgefüge mit davon abweichenden Eigenschaften untersucht. In einer früheren Veröffentlichung wurden bereits Ergebnisse aus einem abgeschlossenen Vorhaben vorgestellt. Dabei wurden drei Varianten untersucht, die alle aus dem für Verzahnungen üblichen Werkstoff 20MnCr5 gefertigt waren und unterschiedlich wärmebehandelt wurden. Es wurde eine konventionell aufgekohlte und einsatzgehärtete Referenzvariante, eine gasaufgekohlte Variante mit erhöhtem Restaustenitgehalt und eine Variante mit erhöhtem Bainitgehalt in der Randschicht betrachtet. Die beiden letztgenannten Varianten wiesen eine vergleichbare Zahnfußtragfähigkeit wie die Referenzvariante auf, allerdings konnte jeweils eine erhöhte Grübchentragfähigkeit festgestellt werden. N. Blech
Forschung Im Ingenieurwesen-engineering Research, Sep 9, 2022
The flank load carrying capacity of bevel and hypoid gears is mainly limited by the failure modes... more The flank load carrying capacity of bevel and hypoid gears is mainly limited by the failure modes pitting, scuffing, tooth flank fracture and the phenomenon micropitting. By application of a standardized calculation method, e.g. according to the international standard ISO 10300:2014, a first estimation of the flank load carrying capacity can be made based on the macro geometry of the bevel or hypoid gear set. According to method B of ISO 10300:2014 the complexity of the real geometry of bevel and hypoid gears is reduced to a virtual cylindrical gear geometry. The load carrying capacity regarding scuffing, micropitting and tooth flank fracture can be determined by using the virtual cylindrical gear geometry along the path of contact. However, the determination of the pitting load carrying capacity is carried out on a single representative point on the path of contact of the virtual cylindrical gear. This paper shows an extended calculation method for the determination of the pitting load carrying capacity of bevel and hypoid gears along the path of contact of the virtual cylindrical gear geometry. Due to the calculation along the path of contact the extended method allows a more precise estimation of the pitting load carrying capacity than the current standard calculation method ISO 10300-2:2014 using the same input data. Within this paper all relevant factors of the extended calculation method are explained in detail. Furthermore, the verification of the extended calculation method with calculation results of an intense validated loaded tooth contact analysis, corresponding to method A of ISO 10300-2:2014, is presented. Erweiterte Berechnungsmethode zur Bestimmung der Grübchentragfähigkeit von Kegel-und Hypoidrädern Zusammenfassung Die Flankentragfähigkeit von Kegel-und Hypoidrädern wird hauptsächlich durch die Schadensarten Grübchen, Fressen, Zahnflankenbruch und das Phänomen Grauflecken begrenzt. Durch Anwendung einer standardisierten Berechnungsmethode, wie zum Beispiel der internationalen Normschriftreihe ISO 10300:2014, kann eine erste Abschätzung der Flankentragfähigkeit auf Basis der Makrogeometrie des Kegel-oder Hypoidradsatzes vorgenommen werden. Entsprechend der Berechnungsmethode B der ISO 10300:2014 wird die Komplexität der realen Geometrie von Kegel-und Hypoidrädern auf eine virtuelle Ersatzstirnradverzahnung reduziert. Die Fress-, Grauflecken-und Zahnflankenbruchtragfähigkeit kann entlang der Eingriffsstrecke der virtuellen Ersatzstirnradverzahnung ermittelt werden. Die Bestimmung der Grübchentragfähigkeit hingegen erfolgt an einem einzigen repräsentativen Berechnungspunkt auf der Eingriffsstrecke der virtuellen Ersatzstirnradverzahnung.
Forschung Im Ingenieurwesen-engineering Research, Jul 6, 2021
Worm gears with wheels of harder materials, such as cast iron or steel, are often prone to the da... more Worm gears with wheels of harder materials, such as cast iron or steel, are often prone to the damage type scuffing, which can cause a sudden and rapid failure of the gear box. Contact temperature is a suitable criterion to determine the scuffing safety for other types of gears. However, for worm gears, a scuffing load capacity calculation is not available at the moment. This paper presents a numerical temperature simulation for worm gears that considers transient multidimensional heat transfer and local frictional loading due to the contact. Based on the results of this simulation, this paper derives a simplified calculation of worm gear contact temperatures. The calculation only contains input parameters that are already part of current standards. Its result, the contact temperature of worm gears, can be used to rate the scuffing load capacity. Fresstragfähigkeitsberechnung von Schneckengetrieben Zusammenfassung Schneckengetriebe mit Rädern aus härteren Werkstoffen, wie zum Beispiel Gusseisen oder Stahl, sind oft anfällig für die Schadensart Fressen, welche zu einem plötzlichen Ausfall des Getriebes führen kann. Für andere Verzahnungsarten hat sich die Kontakttemperatur als ein geeignetes Kriterium zur Bestimmung der Fresssicherheit bewährt. Für Schneckengetriebe ist derzeit jedoch eine verbreitete und genormte Berechnung zur Bestimmung der Fresssicherheit nicht verfügbar. In diesem Beitrag wird dementsprechend eine numerische Temperatursimulation für Schneckenräder vorgestellt, die den instationären und mehrdimensionalen Wärmetransport und die lokale Reibungsbelastung durch den Kontakt berücksichtigt. Basierend auf den Ergebnissen dieser Simulation wird in diesem Beitrag eine vereinfachte Berechnung der Kontakttemperaturen abgeleitet. Die Berechnung enthält nur Eingangsparameter, die bereits Bestandteil der aktuellen Normen sind. Das Ergebnis, die Kontakttemperatur von Schneckenverzahnungen, kann zur Bewertung der Fresstragfähigkeit verwendet werden. Symbols a Center distance [mm] c Specific heat capacity [J =.kgK/] i Gear ratio [−] n Rotational speed [revolutions=mi n] p H m Mean Hertzian contact stress [N=m 2 ] P q Heat flux [W=m 2 ] v g Sliding velocity [m=s] Availability of data and material Not applicable Code availability Not applicable
Forschung Im Ingenieurwesen-engineering Research, Jul 8, 2021
Due to their compactness and power density, planetary gearboxes are used for a wide range of high... more Due to their compactness and power density, planetary gearboxes are used for a wide range of high-performance applications in the automotive, aviation and marine sector. Aerospace applications in particular benefit from a full use of the load capacity potential to meet the requirements for lightweight construction and efficiency. Against this background, the load sharing between the individual planetary gears plays a decisive role. A uniform load sharing enables the design of the single tooth meshes without load increases and oversizing. However, due to manufacturing and assembly deviations, a perfect load sharing is technically not feasible. These load increases are taken into account in the standard calculation of the load capacity of planetary gearboxes by the mesh load factor Kγ. The load sharing in planetary gearboxes is influenced by a number of factors, such as the rigidity of shafts, housing and bearings, the number of planets, the quality of the gear wheels and the operating conditions. Detailed simulations or extensive experimental measurements are required to determine the exact load sharing. For new designs of planetary gearboxes, there are only simplified assumptions available, based on the number of planets and a rough estimation of the operating range. Especially additional dynamic forces, due to operation in high-speed ranges or near resonance frequencies, can lead to a considerable change of the dynamic load sharing compared to the static load sharing and cause an uncertainty in the design. Thus, in this paper the dynamic load sharing behaviour is investigated from 0 to 6800 rpm sun speed for different loads. Based on the experimental data recommendations for the design of planetary gearboxes under consideration of the operating conditions are derived.
Forschung Im Ingenieurwesen-engineering Research, Jul 14, 2021
Zusammenfassung Diese Arbeit verfolgt das Ziel die Zahnfußtragfähigkeit schergeschnittener Verzah... more Zusammenfassung Diese Arbeit verfolgt das Ziel die Zahnfußtragfähigkeit schergeschnittener Verzahnungen zu untersuchen und diese durch Nutzung der beim Fertigungsprozess induzierten Eigenspannungen zu verbessern. Dazu wird eine ausgewählte Zahnradgeometrie durch das Near-Net-Shape-Blanking Verfahren "Feinschneiden" hergestellt. Dabei wird der Einfluss des Prozessparameters "Matrizenschneidkantenradius" auf Schnittflächenkenngrößen und Eigenspannungen untersucht. Die Zahnfußtragfähigkeit der feingeschnittenen Zahnradvarianten wird ermittelt und in bestehende Zahnradnormen eingeordnet. Zusätzlich werden Stichversuche mit einer Zahnradvariante, hergestellt durch Feinschneiden mit geringer Gegenhalterkraft und einer feingeschnittenen und anschließend spannungsarmgeglühten Variante durchgeführt. Die einzelnen Prüfvarianten werden hinsichtlich der ermittelten Zahnfußtragfähigkeit und des vorliegenden Eigenspannungszustands verglichen. Für die Varianten mit Matrizenschneidkantenradius von r M = 50; 100; 150 und 200 m ergeben sich vergleichbare Schnittflächenkenngrößen und Konturen. Für größere Matrizenschneidkantenradien werden höhere Druckeigenspannungen gemessen und höhere Zahnfußtragfähigkeiten ermittelt. Die ermittelten Zahnfußdauerfestigkeiten der feingeschnittenen Zahnräder liegen insgesamt auf einem ähnlichen Niveau, das deutlich höher liegt als für diesen Grundwerkstoff in der ISO 6336-5 angegeben wird. Mit F lim = 317:::327 N/mm 2 liegen die feingeschnittenen Zahnräder auf dem unteren Niveau von ungestrahlten einsatzgehärteten Zahnrädern. Für die weiteren Prüfvarianten zeigt sich im Vergleich zu den feingeschnittenen Zahnrädern eine deutliche Abnahme der ertragbaren Lastwechsel bei kleineren Lasten. Die verminderte Zahnfußtragfähigkeit lässt sich auf geringere vorliegende Druckeigenspannungen zurückführen. Somit lassen sich die Eigenspannungen über die Aktivelementkantenpräparation und die Gegenhalterkraft so einstellen, dass eine möglichst hohe Tragfähigkeit erzielt wird. Influence of process-induced residual stresses on the tooth root bending strength of shear-cut gears Abstract This work pursues the objective of investigating the tooth root bending strength of shear-cut gears and improving it by utilizing the residual stresses induced during the manufacturing process. For this purpose, a selected gear geometry is manufactured by the near-net-shape blanking process "fineblanking". The influence of the process parameter "die edge radius" on the cut surface characteristics and the residual stresses is investigated. The tooth root bending strength of the fineblanked gear variants is determined and compared with the strength numbers given in gear standards. In addition, tests are carried out with a gear variant produced by fineblanking with a low counterpunch force and a fineblanked and subsequently stress-relief treated variant. The individual test variants are compared in terms of the determined tooth root bending strength and the residual stresses present.
Forschung Im Ingenieurwesen-engineering Research, Sep 13, 2021
Plastic gears and their numerous applications have become an integral part of industrial practice... more Plastic gears and their numerous applications have become an integral part of industrial practice. In particular, the ability to produce large numbers of gears cost-effectively using injection molding techniques is making a significant contribution to growing market shares. Compared to conventional steel materials, however, the material properties of thermoplastics differ fundamentally. In particular, the high temperature dependence of the material properties and the lower strength pose challenges for designers. Against this background, theoretical and experimental studies on the operating and service life behavior of different thermoplastic materials have been conducted and evaluated. In addition to theoretical investigations on the tooth flank load carrying capacity, comprehensive measurements on temperature behavior were carried out and compared to common methods of temperature calculation for plastic gears. Experimental investigations on the tooth flank load capacity by means of back-to-back tests of different materials and their evaluation show the potential of thermoplastic materials for the application in power transmitting drivetrains. This contribution will give an overview of the performed research work and summarizes main results of these studies. Betriebsverhalten und Leistungspotential von ölgeschmierten Kunststoffzahnrädern Zusammenfassung Kunststoffzahnräder und ihre zahlreichen Anwendungen sind aus der industriellen Praxis nicht mehr wegzudenken. Insbesondere die Möglichkeit, Zahnräder in großen Stückzahlen kostengünstig im Spritzgussverfahren zu produzieren, trägt wesentlich zu deren wachsenden Marktanteilen bei. Im Vergleich zu herkömmlichen Stahlwerkstoffen unterscheiden sich die Materialeigenschaften von Thermoplasten jedoch grundlegend von den von Stahlwerkstoffen bekannten Eigenschaften. Insbesondere die hohe Temperaturabhängigkeit der Materialeigenschaften und die geringere Festigkeit stellen Herausforderungen im Auslegungsprozess von Zahnrädern dar. Vor diesem Hintergrund wurden theoretische und experimentelle Untersuchungen zum Betriebs-und Lebensdauerverhalten verschiedener thermoplastischer Werkstoffe durchgeführt und ausgewertet. Neben theoretischen Untersuchungen zur Zahnflankentragfähigkeit wurden umfangreiche Messungen zum Temperaturverhalten durchgeführt und mit gängigen Methoden der Temperaturberechnung für Kunststoffzahnräder verglichen. Experimentelle Untersuchungen zur Zahnflankentragfähigkeit verschiedener Werkstoffe und deren Auswertung zeigen das Potenzial von thermoplastischen Werkstoffen für den Einsatz in leistungsübertragenden Antriebssträngen auf. Dieser Beitrag gibt einen Überblick über die durchgeführten Forschungsarbeiten und fasst die wesentlichen Ergebnisse dieser Untersuchungen zusammen.
Forschung Im Ingenieurwesen-engineering Research, Nov 4, 2021
In shot-peened components, failures can be caused by a crack initiation below the surface at a no... more In shot-peened components, failures can be caused by a crack initiation below the surface at a non-metallic inclusion in the steel matrix. This fracture mechanism is called "fisheye failure". In addition, this failure type can lead to a decreased endurance fatigue limit for the component. By preventing this crack mechanism, higher bending strength is expected to be achievable. Various research by universities and research institutes has taken place in this field using standard specimen and sometimes special alloy systems. However, in the tooth root of a gear, a complex multiaxial stress condition is present. Furthermore, the most commonly gears used in transmissions are made out of case-hardened wrought steels. Therefore, in the gear industry, there is only limited knowledge available about this failure type and the failure characteristics, so far. The first step to gain more knowledge requires extended and proper characterization of the crack area. Furthermore, in standardized gear calculation methods a consideration of a crack initiation below the surface at non-metallic inclusions is not possible, yet. Therefore, extended model approaches are still necessary. However, the reliability of such model approaches depends strongly on the quality of the input data, which can only be ensured by a proper fracture surface analysis. As a starting point, the aim of this paper is to characterize systematically the fracture area characteristics in the tooth root fillet of case-hardened, shot-peened gears in detail according to a presented approach to further extend a presented extended model approach in the medium term.
Forschung Im Ingenieurwesen-engineering Research, Nov 10, 2020
In order to increase the power density of BEVs (Battery Electric Vehicles), high-speed concepts a... more In order to increase the power density of BEVs (Battery Electric Vehicles), high-speed concepts are being progressively developed. With increased speed, the power of the electrical machine can be maintained with reduced torque and therefore size, resulting in cost and package advantages. In the joint research project Speed4E with seven industrial and five university partners, such high-speed electromechanical powertrain is being developed and investigated. The electrical machines will run at a maximum rotational speed of 50,000 rpm in the test rig and 30,000 rpm in the test vehicle. The developed lubrication system for the Speed4E transmission aims for high efficiency and optimized heat balance, via a demand-oriented oil flow. In this context, this study investigates how an efficient lubrication system can be designed with respect to the holistic thermal management of the vehicle. Therefore, a hybrid lubrication consisting of dip and injection lubrication is realized. For the analysis and evaluation, efficiency calculations and CFD (Computational Fluid Dynamics) simulations of the oil distribution are presented. Effiziente Schmierung eines elektromechanischen Hochdrehzahlantriebsstrangs mit ganzheitlichem Thermomanagement Zusammenfassung Um die Leistungsdichte von BEVs (Battery Electric Vehicles) zu steigern, werden fortschreitend Hochdrehzahlkonzepte weiterentwickelt. Wegen des niedrigeren Drehmoments bei höheren Drehzahlen kann die Baugröße der elektrischen Maschine bei gleicher Leistung reduziert werden, was zu Kosten-und Packagevorteilen führt. Im Verbundforschungsvorhaben Speed4E, mit sieben Industriepartnern und fünf universitären Partnern, wird solch ein elektromechanischer Hochdrehzahlantriebsstrang entwickelt und untersucht. Im Prüfstand sind die elektrischen Maschinen auf eine maximale Drehzahl von 50.000 min-1 ausgelegt, im Versuchsfahrzeug ist die Drehzahl auf 30.000 min-1 begrenzt. Im Rahmen eines ganzheitlichen Thermomanagements soll das entwickelte Schmierungssystem für das Speed4E-Getriebe möglichst niedrige Verluste aufweisen und einen zuverlässigen Abtransport der Reibungswärme ermöglichen. Dazu wird eine Hybridschmierung durch Kombination von Tauch-und Einspritzschmierung realisiert. Um diese Hybridschmierung zu analysieren und zu evaluieren, werden in dieser Veröffentlichung Wirkungsgradberechnungen und CFD (Computational Fluid Dynamics) Simulationen vorgestellt.
Properties and environmental dependencies of mechatronic components like gear-drives and motors i... more Properties and environmental dependencies of mechatronic components like gear-drives and motors impact the overall performance of automated Production Systems. These properties, often in the form of characteristic curves, are only accessible from suppliers' documents, like operating instructions or online catalogs. The proposed SysML' profile integrates artifacts from SysML and UML into disciplinary views. It includes a reference mechanism to REXS (standard for gear properties) and ECLASS (standard for product data like UNSPSC) to overcome the semantic inconsistency of component properties and inclusion of curves. A metamodel is used for a more precise presentation of the proposed reference mechanism. Due to the static nature of a profile, a Business Process Modeling Notation is used to dynamically illustrate the benefits of SysML' in the workflow.
Purpose Numerous metals can be processed using the additive manufacturing process laser-based pow... more Purpose Numerous metals can be processed using the additive manufacturing process laser-based powder bed fusion of metals (PBF-LB/M, ISO/ASTM 52900). The main advantages of additive manufacturing technologies are the high degree of design freedom and the cost-effective implementation of lightweight structures. This could be profitable for gears with increased power density, combining reduced mass with considerable material strength. Current research on additively manufactured gears is focused on developing lightweight structures but is seldom accompanied by simulations and even less by mechanical testing. There has been very little research into the mechanical and material properties of additively manufactured gears. The purpose of this study is to investigate the behavior of lightweight structures in additively manufactured gears under static loads. Design/methodology/approach This research identifies the static load-carrying capacity of helical gears with different lightweight str...
Shear cutting is used for manufacturing various parts ranging from e.g. simple washers to complex... more Shear cutting is used for manufacturing various parts ranging from e.g. simple washers to complex gears. The latter are typically subjected to cyclic loading and fail foremost due to fatigue damages. Hereby, the parts lifetime is mainly determined by: the geometry, the applied load, the material, the hardness, the roughness and the residual stress state. While numerous research works deal with the influence of the process parameters on the hardness and the parts geometry, the influence of the process parameters on the residual stress state and on the resulting fatigue strength has not been investigated in detail, yet. In an earlier publication, suitable shear cutting techniques, which allow to achieve a high amount of clean-cut and a favorable residual stress state were compared. In this paper, the influence of the process parameters on the residual stress state and the resulting bending fatigue strength are addressed. To simulate the bending stress occurring in the tooth root, C-shaped specimens were manufactured by different blanking techniques. The die-clearance and punch and die edge radii were varied with these blanking techniques. After measuring the cut-surface geometry, the hardness distribution and the surface roughness, the fatigue strength was determined in a pulsating test rig. By carrying out residual stress measurements using x-ray diffraction and simulating the material flow behavior using the Finite-Element-Method, basic mechanisms, which are influencing the residual stress state and the resulting bending fatigue strength, were identified and will be presented and discussed in the paper.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The International Journal of Advanced Manufacturing Technology, Nov 19, 2022
The v-ring indenters and their configurations play a major role in the fineblanking process, dire... more The v-ring indenters and their configurations play a major role in the fineblanking process, directly influencing component quality and characteristics. While past studies regarding residual stresses of blanked components focused mainly on the use of a pair of v-rings, so far no efforts were undertaken to compare different v-ring setups, deducing tool design guidelines and enabling possible cost savings. Therefore, a comparative study of different v-ring indenter setups and their influence on cut surface parameters, surface hardness and induced residual stresses of the produced components was performed. The obtained results indicate a minor influence of blank holder-sided v-rings on the observed component characteristics in comparison to indenters situated on the die leading to recommendations with regard to cost-efficient tool design.
A computational fluid dynamics (CFD) model of the thermal elastohydrodynamically lubricated (EHL)... more A computational fluid dynamics (CFD) model of the thermal elastohydrodynamically lubricated (EHL) line contact problem has been developed for the purpose of exploring the physical processes that occur inside a thin EHL film subjected to shearing motion. The Navier-Stokes equations are solved by using the finite volume method (FVM) in a commercial CFD software, ANSYS Fluent. A set of user-defined functions (UDF) are used for computing viscosity, density, heat source, temperature of moving surfaces and elastic deformation of the top roller according to well-established equations commonly used in the EHL theory. The cavitation problem is solved by taking into account multiphase mixture flow. The model combinations of Houpert and Ree-Eyring and of Tait and Carreau were used for modeling the non-Newtonian behavior of Squalane and the results were compared. Both rheological models suggest the existence of shear-band and plug-flow at high fluid pressure. Due to the differences in viscosity at GPa-level pressure, the chosen model has substantial influence on the computed shear stress and temperature distributions in the high-pressure region. This shows the importance of using correct rheology information in the whole range of pressure, temperature, and shear strain rate.
Forschung Im Ingenieurwesen-engineering Research, Jun 7, 2023
Current challenges for today's industry are an increase in gear ratio in one stage, an increase i... more Current challenges for today's industry are an increase in gear ratio in one stage, an increase in load capacity as well as an increase in efficiency compared to standard gears. The standard tooth profile for cylindrical gears is an involute. This tooth profile has certain limits for external gearings regarding its geometry, e.g., undercutting and a small radius of curvature near the base circle. Special gearings overcome these limits and offer an enormous potential in gear design through their adapted profile geometries. New manufacturing possibilities for gears, such as additive manufacturing or 5-axis milling, mean that special gears can also be produced economically. In comparison to involute gears the description of non-involute gears is often not standardized and parameters describing the geometry are not commonly defined. Thus, it is not possible to adequately determine the corresponding properties. One of these special tooth profiles is the eccentric cycloid gearing (EC gearing), in which a circular profile rolls with a profile of a trochoid equidistant. This flank geometry can provide advantages over the standard involute in certain applications. This study introduces a geometric description of the EC gearing, which is based on a defined set of parameters. Besides the geometrical parameters, parameters describing the characteristics of the gearing are proposed in accordance with the description of involute gears. This parametric description of the EC gearing enables an analytical determination of the flank, the contact geometry and load-free characteristics. With the parametric description shown and the variation of the geometry possible with it, gearings suitable for practical applications can be generated. Parameterbasierte Definition von Exzenter-Zykloiden-Verzahnungen Zusammenfassung Für die heutige Industrie ist das Offenlegen von Potenzial hinsichtlich einer höheren Übersetzung in einer Stufe, einer Erhöhung der Tragfähigkeit sowie einer Wirkungsgradsteigerung im Vergleich zu Standardverzahnungen wichtig. Evolventenverzahnungen stellen die aktuell bedeutendste Verzahnungsart für Stirnräder im Maschinenbau dar. Durch dieses Verzahnungsprofil bestehen bei Außenverzahnungen aber auch gewisse Probleme wie die Mindestzähnezahl zur Vermeidung von Unterschnitt und die kleinen Krümmungsradien in der Nähe des Grundkreises. Sonderverzahnungen können durch ihre angepassten Profilgeometrien diese Potenziale heben. Durch die neuen Herstellmöglichkeiten von Zahnrädern, wie beispielsweise additive Fertigung oder 5-Achs-Fräsen, können auch Sonderverzahnungen wirtschaftlich erzeugt werden. Im Gegensatz zur Evolventenverzahnung ist die Beschreibung von Sonderverzahnungen oftmals nicht standardisiert und die notwendigen Parameter zur Beschreibung der Geometrie sind nicht einheitlich definiert. Dadurch ist es nicht möglich, die entsprechenden Verzahnungsparameter geeignet zu bestimmen. Eine diese Sonderverzahnungen ist die Exzenter-Zykloiden-Verzahnung (EZ-Verzahnung), bei welcher ein Kreisprofil mit einem Profil einer Trochoidenäquidistante abwälzt. Durch diese Flankengeometrie können Vorteile gegenüber der standardmäßigen Evolvente in bestimmten Anwendungsfällen entstehen. Availability of data and material 'Not applicable' Code availability 'Not applicable'
Forschung Im Ingenieurwesen-engineering Research, Jan 10, 2023
Case hardening represents the most important heat treatment process to increase the load carrying... more Case hardening represents the most important heat treatment process to increase the load carrying capacity of gear components. Beside predominantly martensitic surface layers with low proportion of retained austenite, there were investigated material structures with differing properties in preceding research work. In a previous publication, the results of three variants made of the material 20MnCr5, which is typically used for gears, were presented. The reference heat treatment was a conventional carburizing with subsequent case hardening. The second variant was also gas carburized, but with a high proportion of retained austenite. The last presented variant had a bainitic structure in the surface layer. The second and the third variant showed a similar tooth root bending strength compared to the reference. The numbers of the pitting resistance were significantly higher than for the reference variant. This paper presents the results of further investigations on the influence of different microstructures on the gear load carrying capacity. For this purpose, gears made of 18CrNiMo7-6 were tested with regard to their load carrying capacity. 18CrNiMo7-6 is a case hardening steel like 20MnCr5, too, which is often applied in big gear components. The tooth root bending strength was approximately constant, whereas the pitting resistance decreased compared to the corresponding variants of the material 20MnCr5. In comparison to the carburized 20MnCr5 reference variant, only the 18CrNiMo7-6 variant with a large proportion of retained austenite showed a higher pitting resistance. The tooth root bending strength investigations took place in the cycle regime of limited life as well in the high cycle fatigue regime. The pitting resistance was only determined in the cycle regime of limited life. Einfluss des Werkstoffs auf die Festigkeitseigenschaften von Zahnrädern mit alternativen Randschichtgefügen Zusammenfassung Das Einsatzhärten stellt heute das wichtigste Wärmebehandlungsverfahren zur Steigerung der Tragfähigkeit von Getriebebauteilen dar. Neben vorwiegend martensitischen Randschichtgefügen mit einem geringen Anteil an Restaustenit wurden in vergangenen Forschungsvorhaben Randschichtgefüge mit davon abweichenden Eigenschaften untersucht. In einer früheren Veröffentlichung wurden bereits Ergebnisse aus einem abgeschlossenen Vorhaben vorgestellt. Dabei wurden drei Varianten untersucht, die alle aus dem für Verzahnungen üblichen Werkstoff 20MnCr5 gefertigt waren und unterschiedlich wärmebehandelt wurden. Es wurde eine konventionell aufgekohlte und einsatzgehärtete Referenzvariante, eine gasaufgekohlte Variante mit erhöhtem Restaustenitgehalt und eine Variante mit erhöhtem Bainitgehalt in der Randschicht betrachtet. Die beiden letztgenannten Varianten wiesen eine vergleichbare Zahnfußtragfähigkeit wie die Referenzvariante auf, allerdings konnte jeweils eine erhöhte Grübchentragfähigkeit festgestellt werden. N. Blech
Forschung Im Ingenieurwesen-engineering Research, Sep 9, 2022
The flank load carrying capacity of bevel and hypoid gears is mainly limited by the failure modes... more The flank load carrying capacity of bevel and hypoid gears is mainly limited by the failure modes pitting, scuffing, tooth flank fracture and the phenomenon micropitting. By application of a standardized calculation method, e.g. according to the international standard ISO 10300:2014, a first estimation of the flank load carrying capacity can be made based on the macro geometry of the bevel or hypoid gear set. According to method B of ISO 10300:2014 the complexity of the real geometry of bevel and hypoid gears is reduced to a virtual cylindrical gear geometry. The load carrying capacity regarding scuffing, micropitting and tooth flank fracture can be determined by using the virtual cylindrical gear geometry along the path of contact. However, the determination of the pitting load carrying capacity is carried out on a single representative point on the path of contact of the virtual cylindrical gear. This paper shows an extended calculation method for the determination of the pitting load carrying capacity of bevel and hypoid gears along the path of contact of the virtual cylindrical gear geometry. Due to the calculation along the path of contact the extended method allows a more precise estimation of the pitting load carrying capacity than the current standard calculation method ISO 10300-2:2014 using the same input data. Within this paper all relevant factors of the extended calculation method are explained in detail. Furthermore, the verification of the extended calculation method with calculation results of an intense validated loaded tooth contact analysis, corresponding to method A of ISO 10300-2:2014, is presented. Erweiterte Berechnungsmethode zur Bestimmung der Grübchentragfähigkeit von Kegel-und Hypoidrädern Zusammenfassung Die Flankentragfähigkeit von Kegel-und Hypoidrädern wird hauptsächlich durch die Schadensarten Grübchen, Fressen, Zahnflankenbruch und das Phänomen Grauflecken begrenzt. Durch Anwendung einer standardisierten Berechnungsmethode, wie zum Beispiel der internationalen Normschriftreihe ISO 10300:2014, kann eine erste Abschätzung der Flankentragfähigkeit auf Basis der Makrogeometrie des Kegel-oder Hypoidradsatzes vorgenommen werden. Entsprechend der Berechnungsmethode B der ISO 10300:2014 wird die Komplexität der realen Geometrie von Kegel-und Hypoidrädern auf eine virtuelle Ersatzstirnradverzahnung reduziert. Die Fress-, Grauflecken-und Zahnflankenbruchtragfähigkeit kann entlang der Eingriffsstrecke der virtuellen Ersatzstirnradverzahnung ermittelt werden. Die Bestimmung der Grübchentragfähigkeit hingegen erfolgt an einem einzigen repräsentativen Berechnungspunkt auf der Eingriffsstrecke der virtuellen Ersatzstirnradverzahnung.
Forschung Im Ingenieurwesen-engineering Research, Jul 6, 2021
Worm gears with wheels of harder materials, such as cast iron or steel, are often prone to the da... more Worm gears with wheels of harder materials, such as cast iron or steel, are often prone to the damage type scuffing, which can cause a sudden and rapid failure of the gear box. Contact temperature is a suitable criterion to determine the scuffing safety for other types of gears. However, for worm gears, a scuffing load capacity calculation is not available at the moment. This paper presents a numerical temperature simulation for worm gears that considers transient multidimensional heat transfer and local frictional loading due to the contact. Based on the results of this simulation, this paper derives a simplified calculation of worm gear contact temperatures. The calculation only contains input parameters that are already part of current standards. Its result, the contact temperature of worm gears, can be used to rate the scuffing load capacity. Fresstragfähigkeitsberechnung von Schneckengetrieben Zusammenfassung Schneckengetriebe mit Rädern aus härteren Werkstoffen, wie zum Beispiel Gusseisen oder Stahl, sind oft anfällig für die Schadensart Fressen, welche zu einem plötzlichen Ausfall des Getriebes führen kann. Für andere Verzahnungsarten hat sich die Kontakttemperatur als ein geeignetes Kriterium zur Bestimmung der Fresssicherheit bewährt. Für Schneckengetriebe ist derzeit jedoch eine verbreitete und genormte Berechnung zur Bestimmung der Fresssicherheit nicht verfügbar. In diesem Beitrag wird dementsprechend eine numerische Temperatursimulation für Schneckenräder vorgestellt, die den instationären und mehrdimensionalen Wärmetransport und die lokale Reibungsbelastung durch den Kontakt berücksichtigt. Basierend auf den Ergebnissen dieser Simulation wird in diesem Beitrag eine vereinfachte Berechnung der Kontakttemperaturen abgeleitet. Die Berechnung enthält nur Eingangsparameter, die bereits Bestandteil der aktuellen Normen sind. Das Ergebnis, die Kontakttemperatur von Schneckenverzahnungen, kann zur Bewertung der Fresstragfähigkeit verwendet werden. Symbols a Center distance [mm] c Specific heat capacity [J =.kgK/] i Gear ratio [−] n Rotational speed [revolutions=mi n] p H m Mean Hertzian contact stress [N=m 2 ] P q Heat flux [W=m 2 ] v g Sliding velocity [m=s] Availability of data and material Not applicable Code availability Not applicable
Forschung Im Ingenieurwesen-engineering Research, Jul 8, 2021
Due to their compactness and power density, planetary gearboxes are used for a wide range of high... more Due to their compactness and power density, planetary gearboxes are used for a wide range of high-performance applications in the automotive, aviation and marine sector. Aerospace applications in particular benefit from a full use of the load capacity potential to meet the requirements for lightweight construction and efficiency. Against this background, the load sharing between the individual planetary gears plays a decisive role. A uniform load sharing enables the design of the single tooth meshes without load increases and oversizing. However, due to manufacturing and assembly deviations, a perfect load sharing is technically not feasible. These load increases are taken into account in the standard calculation of the load capacity of planetary gearboxes by the mesh load factor Kγ. The load sharing in planetary gearboxes is influenced by a number of factors, such as the rigidity of shafts, housing and bearings, the number of planets, the quality of the gear wheels and the operating conditions. Detailed simulations or extensive experimental measurements are required to determine the exact load sharing. For new designs of planetary gearboxes, there are only simplified assumptions available, based on the number of planets and a rough estimation of the operating range. Especially additional dynamic forces, due to operation in high-speed ranges or near resonance frequencies, can lead to a considerable change of the dynamic load sharing compared to the static load sharing and cause an uncertainty in the design. Thus, in this paper the dynamic load sharing behaviour is investigated from 0 to 6800 rpm sun speed for different loads. Based on the experimental data recommendations for the design of planetary gearboxes under consideration of the operating conditions are derived.
Forschung Im Ingenieurwesen-engineering Research, Jul 14, 2021
Zusammenfassung Diese Arbeit verfolgt das Ziel die Zahnfußtragfähigkeit schergeschnittener Verzah... more Zusammenfassung Diese Arbeit verfolgt das Ziel die Zahnfußtragfähigkeit schergeschnittener Verzahnungen zu untersuchen und diese durch Nutzung der beim Fertigungsprozess induzierten Eigenspannungen zu verbessern. Dazu wird eine ausgewählte Zahnradgeometrie durch das Near-Net-Shape-Blanking Verfahren "Feinschneiden" hergestellt. Dabei wird der Einfluss des Prozessparameters "Matrizenschneidkantenradius" auf Schnittflächenkenngrößen und Eigenspannungen untersucht. Die Zahnfußtragfähigkeit der feingeschnittenen Zahnradvarianten wird ermittelt und in bestehende Zahnradnormen eingeordnet. Zusätzlich werden Stichversuche mit einer Zahnradvariante, hergestellt durch Feinschneiden mit geringer Gegenhalterkraft und einer feingeschnittenen und anschließend spannungsarmgeglühten Variante durchgeführt. Die einzelnen Prüfvarianten werden hinsichtlich der ermittelten Zahnfußtragfähigkeit und des vorliegenden Eigenspannungszustands verglichen. Für die Varianten mit Matrizenschneidkantenradius von r M = 50; 100; 150 und 200 m ergeben sich vergleichbare Schnittflächenkenngrößen und Konturen. Für größere Matrizenschneidkantenradien werden höhere Druckeigenspannungen gemessen und höhere Zahnfußtragfähigkeiten ermittelt. Die ermittelten Zahnfußdauerfestigkeiten der feingeschnittenen Zahnräder liegen insgesamt auf einem ähnlichen Niveau, das deutlich höher liegt als für diesen Grundwerkstoff in der ISO 6336-5 angegeben wird. Mit F lim = 317:::327 N/mm 2 liegen die feingeschnittenen Zahnräder auf dem unteren Niveau von ungestrahlten einsatzgehärteten Zahnrädern. Für die weiteren Prüfvarianten zeigt sich im Vergleich zu den feingeschnittenen Zahnrädern eine deutliche Abnahme der ertragbaren Lastwechsel bei kleineren Lasten. Die verminderte Zahnfußtragfähigkeit lässt sich auf geringere vorliegende Druckeigenspannungen zurückführen. Somit lassen sich die Eigenspannungen über die Aktivelementkantenpräparation und die Gegenhalterkraft so einstellen, dass eine möglichst hohe Tragfähigkeit erzielt wird. Influence of process-induced residual stresses on the tooth root bending strength of shear-cut gears Abstract This work pursues the objective of investigating the tooth root bending strength of shear-cut gears and improving it by utilizing the residual stresses induced during the manufacturing process. For this purpose, a selected gear geometry is manufactured by the near-net-shape blanking process "fineblanking". The influence of the process parameter "die edge radius" on the cut surface characteristics and the residual stresses is investigated. The tooth root bending strength of the fineblanked gear variants is determined and compared with the strength numbers given in gear standards. In addition, tests are carried out with a gear variant produced by fineblanking with a low counterpunch force and a fineblanked and subsequently stress-relief treated variant. The individual test variants are compared in terms of the determined tooth root bending strength and the residual stresses present.
Forschung Im Ingenieurwesen-engineering Research, Sep 13, 2021
Plastic gears and their numerous applications have become an integral part of industrial practice... more Plastic gears and their numerous applications have become an integral part of industrial practice. In particular, the ability to produce large numbers of gears cost-effectively using injection molding techniques is making a significant contribution to growing market shares. Compared to conventional steel materials, however, the material properties of thermoplastics differ fundamentally. In particular, the high temperature dependence of the material properties and the lower strength pose challenges for designers. Against this background, theoretical and experimental studies on the operating and service life behavior of different thermoplastic materials have been conducted and evaluated. In addition to theoretical investigations on the tooth flank load carrying capacity, comprehensive measurements on temperature behavior were carried out and compared to common methods of temperature calculation for plastic gears. Experimental investigations on the tooth flank load capacity by means of back-to-back tests of different materials and their evaluation show the potential of thermoplastic materials for the application in power transmitting drivetrains. This contribution will give an overview of the performed research work and summarizes main results of these studies. Betriebsverhalten und Leistungspotential von ölgeschmierten Kunststoffzahnrädern Zusammenfassung Kunststoffzahnräder und ihre zahlreichen Anwendungen sind aus der industriellen Praxis nicht mehr wegzudenken. Insbesondere die Möglichkeit, Zahnräder in großen Stückzahlen kostengünstig im Spritzgussverfahren zu produzieren, trägt wesentlich zu deren wachsenden Marktanteilen bei. Im Vergleich zu herkömmlichen Stahlwerkstoffen unterscheiden sich die Materialeigenschaften von Thermoplasten jedoch grundlegend von den von Stahlwerkstoffen bekannten Eigenschaften. Insbesondere die hohe Temperaturabhängigkeit der Materialeigenschaften und die geringere Festigkeit stellen Herausforderungen im Auslegungsprozess von Zahnrädern dar. Vor diesem Hintergrund wurden theoretische und experimentelle Untersuchungen zum Betriebs-und Lebensdauerverhalten verschiedener thermoplastischer Werkstoffe durchgeführt und ausgewertet. Neben theoretischen Untersuchungen zur Zahnflankentragfähigkeit wurden umfangreiche Messungen zum Temperaturverhalten durchgeführt und mit gängigen Methoden der Temperaturberechnung für Kunststoffzahnräder verglichen. Experimentelle Untersuchungen zur Zahnflankentragfähigkeit verschiedener Werkstoffe und deren Auswertung zeigen das Potenzial von thermoplastischen Werkstoffen für den Einsatz in leistungsübertragenden Antriebssträngen auf. Dieser Beitrag gibt einen Überblick über die durchgeführten Forschungsarbeiten und fasst die wesentlichen Ergebnisse dieser Untersuchungen zusammen.
Forschung Im Ingenieurwesen-engineering Research, Nov 4, 2021
In shot-peened components, failures can be caused by a crack initiation below the surface at a no... more In shot-peened components, failures can be caused by a crack initiation below the surface at a non-metallic inclusion in the steel matrix. This fracture mechanism is called "fisheye failure". In addition, this failure type can lead to a decreased endurance fatigue limit for the component. By preventing this crack mechanism, higher bending strength is expected to be achievable. Various research by universities and research institutes has taken place in this field using standard specimen and sometimes special alloy systems. However, in the tooth root of a gear, a complex multiaxial stress condition is present. Furthermore, the most commonly gears used in transmissions are made out of case-hardened wrought steels. Therefore, in the gear industry, there is only limited knowledge available about this failure type and the failure characteristics, so far. The first step to gain more knowledge requires extended and proper characterization of the crack area. Furthermore, in standardized gear calculation methods a consideration of a crack initiation below the surface at non-metallic inclusions is not possible, yet. Therefore, extended model approaches are still necessary. However, the reliability of such model approaches depends strongly on the quality of the input data, which can only be ensured by a proper fracture surface analysis. As a starting point, the aim of this paper is to characterize systematically the fracture area characteristics in the tooth root fillet of case-hardened, shot-peened gears in detail according to a presented approach to further extend a presented extended model approach in the medium term.
Forschung Im Ingenieurwesen-engineering Research, Nov 10, 2020
In order to increase the power density of BEVs (Battery Electric Vehicles), high-speed concepts a... more In order to increase the power density of BEVs (Battery Electric Vehicles), high-speed concepts are being progressively developed. With increased speed, the power of the electrical machine can be maintained with reduced torque and therefore size, resulting in cost and package advantages. In the joint research project Speed4E with seven industrial and five university partners, such high-speed electromechanical powertrain is being developed and investigated. The electrical machines will run at a maximum rotational speed of 50,000 rpm in the test rig and 30,000 rpm in the test vehicle. The developed lubrication system for the Speed4E transmission aims for high efficiency and optimized heat balance, via a demand-oriented oil flow. In this context, this study investigates how an efficient lubrication system can be designed with respect to the holistic thermal management of the vehicle. Therefore, a hybrid lubrication consisting of dip and injection lubrication is realized. For the analysis and evaluation, efficiency calculations and CFD (Computational Fluid Dynamics) simulations of the oil distribution are presented. Effiziente Schmierung eines elektromechanischen Hochdrehzahlantriebsstrangs mit ganzheitlichem Thermomanagement Zusammenfassung Um die Leistungsdichte von BEVs (Battery Electric Vehicles) zu steigern, werden fortschreitend Hochdrehzahlkonzepte weiterentwickelt. Wegen des niedrigeren Drehmoments bei höheren Drehzahlen kann die Baugröße der elektrischen Maschine bei gleicher Leistung reduziert werden, was zu Kosten-und Packagevorteilen führt. Im Verbundforschungsvorhaben Speed4E, mit sieben Industriepartnern und fünf universitären Partnern, wird solch ein elektromechanischer Hochdrehzahlantriebsstrang entwickelt und untersucht. Im Prüfstand sind die elektrischen Maschinen auf eine maximale Drehzahl von 50.000 min-1 ausgelegt, im Versuchsfahrzeug ist die Drehzahl auf 30.000 min-1 begrenzt. Im Rahmen eines ganzheitlichen Thermomanagements soll das entwickelte Schmierungssystem für das Speed4E-Getriebe möglichst niedrige Verluste aufweisen und einen zuverlässigen Abtransport der Reibungswärme ermöglichen. Dazu wird eine Hybridschmierung durch Kombination von Tauch-und Einspritzschmierung realisiert. Um diese Hybridschmierung zu analysieren und zu evaluieren, werden in dieser Veröffentlichung Wirkungsgradberechnungen und CFD (Computational Fluid Dynamics) Simulationen vorgestellt.
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