Thomas Lohner
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View article: Scuffing Calculation of Cylindrical Gears Facing Loss of Lubrication
Scuffing Calculation of Cylindrical Gears Facing Loss of Lubrication Open
Loss of lubrication in aeronautic drivetrains can lead to catastrophic gearbox failure, and drivetrains must be tested to prove their resistance to loss of lubrication. Research led to a better understanding of the modes of action, interde…
View article: Influence of high speeds on operating behavior of gears under loss of lubrication
Influence of high speeds on operating behavior of gears under loss of lubrication Open
Loss of lubrication in aeronautic drivetrains can be caused by failures in the oil supply system or by damage to the gearbox. This can lead to insufficient heat removal, scuffing, thermal runaway, and catastrophic transmission failure. To …
View article: Mixed and thermal elastohydrodynamic simulation of cylindrical gear designs
Mixed and thermal elastohydrodynamic simulation of cylindrical gear designs Open
In light of the current efforts to protect the climate and reduce CO 2 emissions, the reduction of load-dependent gear power loss and extension of lifetime are key objectives in gearbox design. In order to achieve this, accurate and detail…
View article: Influence of water evaporation on the power loss behavior of cylindrical gears lubricated by aqueous polyalkylene glycols
Influence of water evaporation on the power loss behavior of cylindrical gears lubricated by aqueous polyalkylene glycols Open
Aqueous polyalkylene glycols have demonstrated superlubricity in model and gear tests. One challenge for its application in gearboxes is water evaporation and absorption. This study investigated the influence of water evaporation and absor…
View article: Efficiency improvement potential of a BEV gearbox using a mono fluid circuit
Efficiency improvement potential of a BEV gearbox using a mono fluid circuit Open
In Battery Electric Vehicles (BEVs), energy dissipation can potentially be decreased by combining the cooling of electrical components and lubrication of the gearbox in a mono fluid circuit. This can be achieved by using novel fluids with …
View article: Mixed and thermal elastohydrodynamic simulation of a low-loss gear considering the gear system
Mixed and thermal elastohydrodynamic simulation of a low-loss gear considering the gear system Open
The reduction of load-dependent gear power loss is one of the key aspects in gear design. Therefore, a detailed power loss prediction and the local investigation of its drivers are essential. In this study, the model of Farrenkopf et al. i…
View article: Elastohydrodynamic Lubrication Mechanisms of Aqueous Polyethylene Glycols
Elastohydrodynamic Lubrication Mechanisms of Aqueous Polyethylene Glycols Open
Water-soluble polyalkylene glycols have become a growing subject of research to achieve liquid superlubricity in elastohydrodynamically lubricated contacts. While the influence of various factors, including water content and viscosity, has…
View article: Tribology technologies for gears in loss of lubrication conditions: a review
Tribology technologies for gears in loss of lubrication conditions: a review Open
Transmission systems for the aviation industry are continuously pushed to new and extreme limits. Gears in rotorcraft transmissions or geared turbofans must withstand considerable torques while operating at high rotational speeds and tempe…
View article: Elastohydrodynamic lubrication of aqueous hydroxyethyl cellulose-glycerol lubricants
Elastohydrodynamic lubrication of aqueous hydroxyethyl cellulose-glycerol lubricants Open
Continuous growth in lubricant volume worldwide, environmental hazard of fossil-based lubricants and anthropogenic climate change are reflected in an increasing demand for green, sustainable lubrication. In the presented work, the influenc…
View article: A pathway towards energy efficiency classes for gearboxes related to superefficiency
A pathway towards energy efficiency classes for gearboxes related to superefficiency Open
The energy dissipation in the lifecycle of gearboxes is often dominated by the use phase. Energy efficiency targets can accelerate technological development. For tribological contacts, the definition of superlubricity with coefficients of …
View article: Local Calculation of Load-Dependent Gear Power Losses of Cylindrical Gears
Local Calculation of Load-Dependent Gear Power Losses of Cylindrical Gears Open
The primary design criteria for gearboxes are (i) power density and load capacity; (ii) noise, vibration, and harshness; and (iii) efficiency and heat balance. To meet these design criteria, it is essential to use accurate calculation mode…
View article: Friction in Oil-Lubricated Rolling–Sliding Contacts with Technical and High-Performance Thermoplastics
Friction in Oil-Lubricated Rolling–Sliding Contacts with Technical and High-Performance Thermoplastics Open
Thermoplastics show great potential due to their lightweight design, low-noise operation, and cost-effective manufacturing. Oil lubrication allows for their usage in high-power-transmission applications, such as gears. The current design g…
View article: Influence of water evaporation on elastohydrodynamic lubrication with water-containing polyalkylene glycols
Influence of water evaporation on elastohydrodynamic lubrication with water-containing polyalkylene glycols Open
The reduction of frictional power losses in power transmitting gears takes a crucial role in the design of energy- and resource-efficient drivetrains. Water-containing lubricants like glycerol and polyalkylene glycols have shown great pote…
View article: Improved Operating Behavior of Self-Lubricating Rolling-Sliding Contacts under High Load with Oil-Impregnated Porous Sinter Material
Improved Operating Behavior of Self-Lubricating Rolling-Sliding Contacts under High Load with Oil-Impregnated Porous Sinter Material Open
Resource and energy efficiency are of high importance in gearbox applications. To reduce friction and wear, an external lubricant supply like dip or injection lubrication is used to lubricate tribosystems in machine elements. This leads to…
View article: Application of machine learning for film thickness prediction in elliptical EHL contact with varying entrainment angle
Application of machine learning for film thickness prediction in elliptical EHL contact with varying entrainment angle Open
This contribution demonstrates the potential of machine learning (ML) algorithms in predicting elastohydrodynamic lubrication (EHL) film thickness in elliptical contact with varying direction of lubricant entrainment, ranging from wide to …
View article: Numerical Calculation of the Oil Flow in a Truck Rear Axle Transmission and the Influence of Gear-Induced Air Flow
Numerical Calculation of the Oil Flow in a Truck Rear Axle Transmission and the Influence of Gear-Induced Air Flow Open
For the reliable operation of a gearbox, consistently sufficient lubrication of machine elements is necessary. Thus, the gearbox fluid flow plays an important role. The state of the art indicates that computational fluid dynamics (CFD) ena…
View article: Influence of surface and material technologies on the loss of lubrication performance of gears
Influence of surface and material technologies on the loss of lubrication performance of gears Open
Enabling gears to withstand loss of lubrication in gearboxes without secondary oil supply systems can reduce weight and space demand and thus fuel consumption. This study investigates the potential of surface and material technologies on t…
View article: Classification of numerical, experimental, and analytical approaches for gearbox oil flow and no-load gear power loss
Classification of numerical, experimental, and analytical approaches for gearbox oil flow and no-load gear power loss Open
The interaction of rotating machine elements with fluid in gearboxes results in fluid flow and no-load power loss. A targeted design of the gearbox lubrication system enables a reliable operation under economical and sustainable use of lub…
View article: Numerical analysis of the heat transfer of gears under oil dip lubrication
Numerical analysis of the heat transfer of gears under oil dip lubrication Open
Reliable gearbox operation is based on heat balance. The heat transfer of gears is closely related to the fluid flow of a gearbox. This study focuses on the heat transfer between oil dip-lubricated gears and fluid. A numerical analysis of …
View article: Evaluation of friction calculation methods for rolling bearings
Evaluation of friction calculation methods for rolling bearings Open
In gearboxes, rolling bearing power losses often make up a large amount of the total gearbox power losses. Therefore, an exact calculation of rolling bearing power losses is very important for resource and energy efficient gearbox design. …
View article: Review of different calculation approaches for the mean coefficient of friction in ISO 6336
Review of different calculation approaches for the mean coefficient of friction in ISO 6336 Open
Important goals in gear design are high load carrying capacity, good noise, vibration, and harshness (NVH) performance and high efficiency. Regarding the load carrying capacity, the international series of standards ISO 6336 [13–15] is the…
View article: Characteristics in hard conformal EHL line contacts
Characteristics in hard conformal EHL line contacts Open
Purpose Internal gearings are commonly used in transmissions due to their advantages like high-power density. To ensure high efficiency, load-carrying capacity and good noise behavior, a profound knowledge of the local gear mesh is essenti…
View article: Influence of water content on elastohydrodynamic friction and film thickness of water-containing polyalkylene glycols
Influence of water content on elastohydrodynamic friction and film thickness of water-containing polyalkylene glycols Open
Lubricants with a functional water portion have demonstrated a drastic reduction in friction under elastohydrodynamic lubrication conditions. With water-containing polyalkylene glycols, superlubricity with coefficients of friction <0.01…
View article: Numerical Visualization of Grease Flow in a Gearbox
Numerical Visualization of Grease Flow in a Gearbox Open
Lubricating greases are widely used in e.g. open gear drives and gearboxes with difficult sealing conditions. The efficiency and heat balance of grease-lubricated gearboxes depend strongly on the lubrication mechanisms channeling and circu…
View article: Numerical and Experimental Analysis of the Oil Flow in a Planetary Gearbox
Numerical and Experimental Analysis of the Oil Flow in a Planetary Gearbox Open
The circular layout and the kinematics of planetary gearboxes result in characteristic oil flow phenomena. The goal of this paper is to apply a new remeshing strategy, based on the finite volume method, on the numerical analysis of a plane…
View article: Thermal Elastohydrodynamic Analysis of a Worm Gear
Thermal Elastohydrodynamic Analysis of a Worm Gear Open
This study explores the elastohydrodynamic lubrication (EHL) between the contacting tooth flanks of a worm gear with nonconjugate meshing action. The contact is characterized by a slender-like elliptical shape and high sliding. The geometr…