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A new system for testing gears under variable torque and speed

Recent Patents on Mechanical engineering 2009年第3期2卷 179-192页

作者： Mihailidis, Athanassios Nerantzis, Ioannis Laboratory of Machine Elements and Machine Design Department of Mechanical Engineering Aristotle University of Thessaloniki Thessaloniki Greece

In many applications, the transmitted power by a gearbox is fluctuating strongly. For example, in wind energy converters the rotor torque depends on the wind velocity and therefore varyies over a wide range, whereas the rotor speed is constant. In automotive applications, both torque and speed vary according to the driving conditions. It is evident, that in order to test such gearboxes, test rigs are needed that enable torque and speed to vary during the test according to the testing requirements and simulate the actual loading conditions as accurately as possible. The first part of this paper is a review of the many known mechanical devices developed to load gears. Their advantages and disadvantages are commented and presented. The second part describes a novel system designed and built by the authors (patent pending), which makes it possible to apply the test torque and speed according to a given load pattern during the test of the gears. It can further be implemented in close power loop test rigs (known also as back-to-back test rigs) such as the FZG test rig. The gearboxes of the test rig may be similar enabling thus the measurements of the power loss and efficiency of the gear pairs. It can also be used in the research of fatigue related surface failures, such as pittings and micro-pittings. The system consists mainly of a self-locking planetary Wolfrom gear train. Its sun gear is connected to a high starting torque electric motor, while its two ring gears are connected to the shafts ends of the two gearboxes. The operation of the motor is controlled by a computer. The software compares the actually applied torque, which is measured by a contactless torque meter, with the required torque, which has been already prescribed. © 2009 Bentham Science Publishers Ltd.

关键词： Torque

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STATIC AND DYNAMIC BEHAVIOR OF A SANDWICH COMPOSITE machine COMPONENT

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COMPOSITE STRUCTURES 1994年第3期29卷 341-347页

作者： VEDY, B VENKATESH, A [a]Laboratory of Machine Elements Design Department of Mechanical Engineering Swiss Federal Institute of Technology CH-1015 Lausanne Switzerland

This paper describes part of a design validation study of a carbon-epoxy sandwich machine component in the form of a curved beam which is subjected to high angular accelerations (more than 5000 s(-2)) during service. The study is based on the comparison of the results of a static loading experiment and modal testing with the corresponding finite element predictions made by using commercial software (I-DEAS). The close correspondence observed between the experimental and the numerical results, despite the incompatibility between the solid and the shell elements used in the finite element analysis, has been discussed from the point of view of the degree of mesh refinement, the simplicity of the design and the quality of fabrication of the component.

关键词： Carbon fiber reinforced plastics

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Prediction of losses in belt-type continuously variable transmission due to sliding between belt and disc

Prediction of losses in belt-type continuously variable tran...

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作者： Poll, G. Kruse, T. Meyer, C. Department of Machine Elements Institute for Machine Elements Engineering Design and Tribology University of Hannover Hannover Germany Department of Machine Elements Institute for Machine Elements Engineering Design and Tribology Welfengarten 1A Hannover 30167 Germany

The efficiency of belt-type continuously variable transmission (CVT) - apart from the power consumption of auxiliary systems such as hydraulics - predominantly depends on the energy dissipated during sliding at the belt-disc contacts. These sliding motions are a consequence of elastic deformations and misalignments because of clearances, resulting in a so-called spiral path of the belt elements on the discs and hence tangential and radial sliding motions. The performance of such systems can be predicted through an iterative computation by numerically solving a set of differential equations for the forces and motions coupled with a finite-element computation of the deformations. A comparison with elaborate measurements of deflections, belt motions, and losses shows that a relatively simple modified Coulomb type friction model with a steep gradient through the origin delivers sufficiently accurate results. The computations reveal the existence of 'locked' zones with extremely low 'creeping' motions. Thus, the mechanisms of power transmission in belt-type CVT are better understood and designers have a validated tool to optimize shaft and disc geometry concerning maximum efficiency. JET141© IMechE 2006.

关键词： Variable speed transmissions

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Load carrying capacity of a heterogeneous surface bearing

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Friction 2015年第4期3卷 287-293页

作者： Evan THOMAS Mircea D PASCOVICI Romeo P GLOVNEA Tribology Laboratory Department of Engineering and DesignUniversity of SussexUnited Kingdom Machine Elements and Tribology Division Politehnica University of BucharestBucharestRomania

It has been shown before that liquids can slip at a solid boundary,which prompted the idea that parallel-surfaces bearings can be achieved just by alternating slip and non-slip regions in the direction of fluid *** amount of slip at the wall depends on the surface tension at the liquid-solid interface,which in turn depends on the chemical state of the surface and its *** the present study a heterogeneous surface was obtained by coating half of a circular glass disc with a coating repellant to glycerol.A rotating glass disc was placed at a known/calibrated distance and the gap was filled with *** the mobile surface moving from the direction of slip to non-slip region it can be theoretically shown that a pressure build up can be *** pressure gradient in the two regions is constant,similar to that in a Rayleigh step bearing,with the maximum pressure at the separation *** heterogeneous disc was placed on a holder supported by a load cell thus the force generated by this pressure increase can be measured *** were carried out at different sliding speeds and gaps and the load carried was measured and subsequently compared with theoretical *** allowed the slip coefficient to be evaluated.

关键词： bearing slip heterogeneous load

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Additive manufacturing of patient-specific, biphasic implants with zonal design for regeneration of osteochondral defects–critical evaluation of the work flow from clinical MRI data to implantation

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Materials Today Bio 2025年 32卷

作者： von Witzleben, Max Liu, Suihong Sembdner, Philipp Holtzhausen, Stefan Blum, Sophia Freya Ulrike Lützner, Jörg Kilian, David Nimtschke, Ute Gelinsky, Michael Lode, Anja Bretschneider, Henriette Centre for Translational Bone Joint and Soft Tissue Research Faculty of Medicine and University Hospital Carl Gustav Carus Technische Universität Dresden Dresden Germany Institute of Machine Elements and Machine Design Faculty of Mechanical Engineering Technische Universität Dresden Dresden Germany Institute and Polyclinic for Diagnostic and Interventional Radiology University Hospital Carl Gustav Carus Technische Universität Dresden Dresden Germany University Center of Orthopaedics Trauma and Plastic Surgery University Hospital Carl Gustav Carus Technische Universität Dresden Dresden Germany Department of Materials Science and Engineering Stanford University StanfordCA United States Institute of Anatomy Faculty of Medicine and University Hospital Carl Gustav Carus Technische Universität Dresden Dresden Germany

Ideally, the combination of clinical imaging techniques with additive manufacturing processes enables the fabrication of patient-specific regenerative implants that precisely fit into the defect site, promoting native tissue restoration while gradually degrading. Osteochondral defects, affecting both cartilage and subchondral bone in joints are best visualized using magnetic resonance imaging (MRI). In this study, a workflow for computer-aided manufacturing of patient-specific osteochondral implants based on geometrical data obtained from MRI scans was evaluated in a clinically relevant setting. Artificial osteochondral defects were created in femoral condyles of human body donors and scanned with MRI. ‘Computer-Aided design’ (CAD) models for bone and cartilage components served as basis for designing defect-specific trizonal implants consisting of (i) a bone, (ii) an interlocking, and (iii) a cartilage zone. These implants were fabricated using multi-channel 3D extrusion printing, using a calcium phosphate cement as a bone substitute and an alginate-based hydrogel as a cartilage substitute material - with both materials alternately printed in the interlocking zone. After fabrication, the constructs were implanted into the corresponding defects, and assessed for fit accuracy via clinical imaging. The entire process chain was successfully conducted under near-clinical conditions by an interdisciplinary team of engineers, radiologist and surgeons, during which critical points were identified. Due to the inherent resolution limitations of clinical MRI and extrusion-based 3D printing, inaccuracies in implant fitting occurred;strategies to address these challenges were identified by integrating design tolerances and applying minor intraoperative adjustments. © 2025 The Authors

关键词： Extrusion

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Overload capacity of high transmission ratio speed reducers

Overload capacity of high transmission ratio speed reducers

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3rd International Conference of engineering Against Failure, ICEAF 2013

作者： Mihailidis, A. Nerantzis, I. Athanasopoulos, E. Aristotle University of Thessaloniki Department of Mechanical Engineering Lab of Machine Elements and Machine Design Greece

ISBN: (纸本)9789608810433

This paper presents a study on the overloading capacity of a Wolfrom type gear planetary system. Such systems are used as reducers when high transmission ratio and power concentration is needed. When they operate as reducers, the efficiency is acceptable. However, when they operate as increasers, the efficiency ratio is very low. Therefore, in many cases such systems can be used when reverse operation is unwanted. Wolfrom reducers are common in aircrafts, robotic arms, nacelles of wind energy converters and cranes among others. In this paper a Wolfrom planetary system with transmission ratio equal to 19.2 is modelled and simulated using the finite element method. This model has the characteristic that multiple contacts occur between complex geometric pairs. The load distribution from the sun to the three planets is unknown. Even for a single gear with double contact the load distribution between the two teeth pairs cannot be determined analytically. In the model each gear engagement is defined as a contact interaction. A single loading torque is applied at the input shaft and the load distribution derives from the solution when equilibrium is achieved. The load transmitted through gear contacts develops surface pressure which is a key factor that determines the load carrying capacity of the reducer and safety against pitting. The root region of the gear teeth is also a critical area because the bending stress determines the safety against tooth breakage. The aim of the present paper is to investigate the overloading capacity of the reducer. A model with balanced element length at the two regions of interest was built with respect to low solution duration and result accuracy.

关键词： Finite element method

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Fatigue life assessment of thin welded joints based on local approaches

Fatigue life assessment of thin welded joints based on local...

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3rd International Conference of engineering Against Failure, ICEAF 2013

作者： Malikoutsakis, Michail Savaidis, G. Aristotle University of Thessaloniki Department of Mechanical Engineering Laboratory of Machine Elements and Machine Design 54124 Thessaloniki Greece

ISBN: (纸本)9789608810433

The present paper examines the potential of applying the Notch Strain Approach to the fatigue assessment of thin welded joints. Detailed analysis of weld geometry along with the experimentally determined fatigue life curve 1, offering weld-end toe failures, is presented using various combinations of parameters for each step of the approach. The Effective Notch Stress Concept described within the IIW guideline2 and properly extended for application on weld-end locations1,3 is used in conjunction with Neuber's sharp and mild notch formulas4, Seeger-Beste formulation5 and Glinka's strain energy density rule6. The fundamental strain-life material curve in combination with the damage parameters after Smith-Watson-Topper7 and Morrow 8 or the mean stress sensitivity factors proposed by Olivier 9 are subsequently applied. The Parent Material, Weld filler Material and Heat Affected Zone are assessed separately with their corresponding ultimate tensile strength values being estimated from hardness measurements and the respective cyclic properties deriving from the Uniform Material Law 10.

关键词： Fatigue of materials

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Fatigue assessment of thin-welded joints with pronounced terminations

Fatigue assessment of thin-welded joints with pronounced ter...

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作者： Malikoutsakis, M. Savaidis, G. Department of Mechanical Engineering Laboratory of Machine Elements and Machine Design Aristotle University of Thessaloniki 54124 Thessaloniki Greece

The present paper reviews and contains simple modifications to extend the applicability of global and local fatigue concepts to thin-welded specimens with pronounced weld terminations (starts/ends). Experimental fatigue data reported by Kaffenberger and Vormwald have been used for the validation of the proposed procedures. Special attention is paid to the notch strain concept. The material state is explicitly considered by means of corresponding strain-life curves in conjunction with PSWT, PMorrow or the experimental mean stress sensitivity factors proposed by Olivier. The accuracy of Neuber's sharp and mild notch formulas, Seeger-Beste's formulation and Glinka's strain energy density rule within the context of the notch strain approach has been investigated. Simple rules accounting for stress relaxation effects have been additionally proposed and implemented into the calculations. Comparison of experimental with theoretical fatigue lives validates the accuracy and robustness of the proposed procedures to calculate fatigue design S-N curves. © 2014 Wiley Publishing Ltd.

关键词： Welds

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design of heavy duty parabolic front leaf-springs with respect to kinematics and stress behavior

Design of heavy duty parabolic front leaf-springs with respe...

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3rd International Conference of engineering Against Failure, ICEAF 2013

作者： Karditsas, S. Savaidis, G. Malikoutsakis, M. Aristotle University of Thessaloniki Department of Mechanical Engineering Laboratory of Machine Elements and Machine Design 54124 Thessaloniki Greece

ISBN: (纸本)9789608810433

The present paper deals with the influence of leaf-spring design parameters on axle kinematics and stress behavior. Parametrical studies on asymmetrical parabolic front mono-leaf springs for heavy duty vehicles were exemplarily performed considering the most significant driving maneuvers using the Finite elements Method. Kinematic curves of the wheel joint were determined and their influence on the steering kinematics was assessed. Additionally, the developed stress distributions along the leaf-spring's arms were determined. The results reveal the influence of each design parameter on the kinematic and stress behavior of leaf springs both qualitatively and quantitatively.

关键词： Finite element method

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Extending rolling element bearing life in hydraulic systems with water-based fluids - The grease lubrication option

Extending rolling element bearing life in hydraulic systems ...

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Hydraulic Failure Analysis

作者： Poll, Gerhard W. Department of Machine Elements Engineering Design and Tribology University of Hannover Welfengarten 1A 30167 Hannover Germany

This paper deals with the influence of rolling bearing lubrication on bearing operation and service life. Hydraulic fluids, especially when they contain water, do not always provide optimum conditions. Coatings or bearing steels specifically developed for such applications cannot completely compensate for the negative effects. It is therefore interesting to consider a separate lubrication system for the bearings, e.g. one based on grease. Then, however, grease service life can be more critical than bearing fatigue or wear. Accordingly, recent experimental and theoretical investigations into the tribological performance characteristics of bearing lubricating greases, especially the effect of their composition on service life, are presented.

关键词： Hydraulic machinery

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