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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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Fatigue design and testing of automotive stabilizer bars 5

Fatigue design and testing of automotive stabilizer bars

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5th International Conference of Engineering Against Failure, ICEAF-V 2018

作者： Giannakis, Efstratios Sivena, Elli Malikoutsakis, Michail Savaidis, Georgios Aristotle University of Thessaloniki Laboratory of Machine Elements and Machine Design Thessaloniki54124 Greece

Stabilisers are components of the axle suspension system of cars trucks, trains and other moving road vehicles that connect the movement of the two sides of the suspension (right and left) to keep the vehicle levelled. Stabilizers experience bending and torsion at operation. In particular, their arms experience bending while the main body mainly torsional loading. In both cases, the highly stressed area is the surface, where the maximum tensile and shear stresses are acting. High strength steels and special treatments, thermal and/or mechanical, are used for the stabilisers' manufacturing. The present study deals with necessary input data for fatigue life assessments based on the FKM guideline [1]. In addition, fatigue tests are conducted to calculate the stress-life curves of two different manufacturing processes. © The Authors, published by EDP Sciences, 2018.

关键词： Fatigue testing

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Wind turbine power transmission systems without rotor shaft

Wind turbine power transmission systems without rotor shaft

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作者： Mihailidis, A. Makropoulou, I. Laboratory of Machine Elements and Machine Design Aristotle University of Thessaloniki Greece

During the last decades, the power rating and consequently the size of wind energy converters (WEC's) follow an increasing trend. The resulting demand for higher load carrying capacity and transmission ratios is expected to rise since larger wind turbines imply lower cost per unit power and allow for a more efficient land use. Following this trend, a new design of a power transmission system for power ratings greater then 1 MW is proposed in the current study. It mainly consists of a common ring gear double stage planetary gearbox, assembled inside two large diameter rolling bearings (also known as slewing bearings) with internal gearing. The rotor hub is directly connected to the inner ring of the outer bearing. Apart from omitting the rotor shaft, this design promotes power splitting, resulting in a compact and lightweight construction.

关键词： Power transmission

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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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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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design Right Once for Additive Manufacturing 5

Design Right Once for Additive Manufacturing

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5th International Conference of Engineering Against Failure, ICEAF-V 2018

作者： Tsakiris, Antonios Salpistis, Christos Mihailidis, Athanassios Aristotle University of Thessaloniki Faculty of Engineering School of Mechanical Engineering Laboratory of Machine Elements and Machine Design Thessaloniki54124 Greece

Additive Manufacturing (AM) has been widely considered a key factor for innovative design. However, the utilization of AM has not been as high as expected, although the technology offers key innovative design capabilities, weight reduction, parts count and assembly consolidation as well as material saving. This low utilization is attributed to the lack of AM understanding, mature CAE/CAM software tools addressing AM specific issues such as design support structure generation and removal, residual stresses, surface quality. In most cases, design for AM (DfAM) is a crucial requisite for a "design Right Once" approach. Such an approach is shown in the current study using three parts as example: an arthropod's leg, a gearshift drum and an electric motor mounting frame. The implementation of geometrical conformal lattice structures and lattices with variable density are discussed. A structured design approach is presented and design dilemmas are solved in terms of a DfAM approach. Primary design optimizations are evaluated. Weight reduction is considered throughout the design and free form surfaces are being used. "Freedom to design" principle is also portrayed and assembly parts consolidation occurs as a natural process of DfAM in comparison with previous design practices. It is concluded that, even from the primary design phase the design engineer can reveal his creativity because of the absence of constraints set by the traditional manufacturing technologies. © The Authors, published by EDP Sciences, 2018.

关键词： 3D printers

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Parametric design and Finite Element Analysis of metallic tanks transporting dangerous goods 5

Parametric design and Finite Element Analysis of metallic ta...

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5th International Conference of Engineering Against Failure, ICEAF-V 2018

作者： Sykaras, Konstantinos Malikoutsakis, Michail Loulas, Minas Mihailidis, Athanassios Aristotle University of Thessaloniki Faculty of Engineering School of Mechanical Engineering Laboratory of Machine Elements and Machine Design Thessaloniki54124 Greece

Metallic tanks are widely used for the transportation of dangerous goods. Manufacturers utilize standards in conjunction with European legislation concerning the international carriage (ADR and RID) to specify the minimum design and construction requirements. The analysis of the tank's attachment to the vehicle is not covered by analytical calculation methods, and only the Finite Element stress analysis can be used prior to manufacture. New ADR amendments demand that the certification authorities conduct stringent examinations that the manufacturer has the ability to perform high quality weldings. Applying the structural strength concept implemented in the International Institute of Welding (IIW) guidelines into the calculation is a protracted task. Aiming at speeding up the procedure, a parametric design and an efficient FE analysis is developed for a LGBF tank. Utilizing parametric design offers sufficient overview of the whole structure, while a supplementary surface model is generated to reduce pre-processing time. The tank is subjected to prescribed load cases, while the meshing directives of the structural hot spot stress concept (SHSSC) according to the IIW recommendations are incorporated in the procedure, in order to assess both the static and fatigue strength of the weld details. Using a multi-compartment LGBF tank as a case study, it is shown that the proposed detailed and automated analysis succeeds in reducing the time and effort needed, as well as in allocating the critical spots, substantially increasing the calculation accuracy. © The Authors, published by EDP Sciences, 2018.

关键词： Welding

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