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Influence of surface structure on film formation and friction coefficient of elastohydrodynamic contacts

Tribologie und Schmierungstechnik 2009年第4期56卷 14-20页

作者： Mihailidis, A. Bakolas, V. Drivakos, N. Decker, P. Gatsios, S. Laboratory of Machine Elements and Machine Design Greece Laboratory of Machine Elements and Machine Design Department of Mechanical Engineering Aristotle University of Thessaloniki 54124 Thessaloniki Greece Schaeffler KG 91074 Herzogenaurach Germany

Wear and surface fatigue of elastohydrodynamic contacts are strongly affected by asperity collisions. Therefore, the transition from the full to the mixed lubrication regime is of particular interest. In order to quantify this transition, the solid contact time percentage is introduced in this study. It is obtained by an experimental technique based on a two-disk test rig that enables to determine whether asperity collisions occur or not. The influence of the surface finish on the elastohydrodynamic performance is investigated using several disk pairs with the same composite roughness but different surface micro-topography. Results are evaluated using both the solid contact time percentage and the friction coefficient. It is shown that significant improvement on the tribological behaviour can be achieved by properly selecting the surface finish. In this way, the need for special surface texturing can be eliminated in many cases.

关键词： Surface roughness

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Fatigue crack growth at notches considering plasticity induced closure 16

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16th European Conference of Fracture

作者： Bruening, Jutta Hertel, Olaf Vormwald, Michael Savaidis, Georgios Materials Mechanics Group Technische Universität Darmstadt Petersenstrabe 12 DarmstadtD-64287 Germany Division of Mechanical Engineering Laboratory of Machine Elements and Machine Design Aristotle University Thessalonica ThessalonicaGR-54124 Greece

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Fracture mechanics based assessment of fatigue of seam weld ends under shear loading

Fracture mechanics based assessment of fatigue of seam weld ...

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3rd International Conference of Engineering Against Failure, ICEAF 2013

作者： Shams, Ehsan Malikoutsakis, Michail Savaidis, Georgios Vormwald, Michael Technische Universität Darmstadt Department of Civil Engineering and Geodesy Material Mechanics Group Petersenstrasse 12 64287 Darmstadt Germany Aristotle University of Thessaloniki Department of Mechanical Engineering Laboratory of Machine Elements and Machine Design 54124 Thessaloniki Greece

ISBN: (纸本)9789608810433

Stress intensity factors are calculated along the weld root for load carrying welded joints under shear loading. The value of the stress intensity factor increases towards the weld end points as expected. An extrapolation procedure is suggested for the determination of a weld end point associated stress intensity factor where the stress singularity is no longer of the crack front type. In the experimental part of this research fatigue testing of thin sheet plane and cylindrical specimens was performed. The fatigue cracks initiated at the weld end points. A weld-end life curve has been obtained which is expressed in terms of the weld end stress intensity factor range. The thin sheet results are compared to results of a thick sheet member of a motor truck to discuss the transferability of fatigue data for different geometrical items.

关键词： Welds

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Notch stress and fracture mechanics based assessment of fatigue of seam weld ends under shear loading

Notch stress and fracture mechanics based assessment of fati...

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作者： Shams, E. Malikoutsakis, M. Savaidis, G. Vormwald, M. Department of Civil and Environmental Engineering Material Mechanics Group Technische Universität Darmstadt Franziska-Braun-Straße 3 64287 Darmstadt Germany Department of Mechanical Engineering Laboratory of Machine Elements and Machine Design Aristotle University of Thessaloniki 54124 Thessaloniki Greece

Welding processes often lead to pronounced weld termination points (start/end), which are prone to fatigue events such as crack initiation. The fatigue of weld ends under shear loading, especially in thin sheet structures, is not sufficiently explored yet. In the present investigation, the real geometry of welds was obtained by scanning the three-dimensional surface, especially of weld ends. Cryogenic breaking of the weld opened the view to the weld root geometry and especially to the critical location, where the weld root migrates to a weld toe at the weld end. In the experimental part of this research, fatigue testing of thin sheet plane and cylindrical specimens as well as large components containing weld ends was performed. Based on the data, weld end life curves have been obtained. The notch stress concept and a fracture mechanics based approach were applied for describing the results of fatigue tests providing sufficient accuracy. © 2014 Wiley Publishing Ltd.

关键词： Welds

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Detail and structural design of a fixed-wing BWB UAV 13

Detail and structural design of a fixed-wing BWB UAV

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13th EASN International Conference on Innovation in Aviation and Space for Opening New Horizons

作者： Psarros, A. Kapsalis, S. Dimopoulos, T. Mitridis, D. Terzis, D. Giannakis, E. Panagiotou, P. Savaidis, G. Yakinthos, K. Laboratory of Machine Elements & Machine Design Department of Mechanical Engineering Aristotle University of Thessaloniki Thessaloniki54124 Greece Laboratory of Fluid Mechanics & Turbomachinery Department of Mechanical Engineering Aristotle University of Thessaloniki Thessaloniki54124 Greece Aristotle University of Thessaloniki Thessaloniki57001 Greece Aristotle University of Thessaloniki Thessaloniki57001 Greece

The current study focuses on the development of a prototype BWB UAV for highway traffic monitoring by supporting a Cooperative Intelligent Transport System (C-ITS). This system allows the monitoring of traffic conditions at large roads and highways. Having determined the mission requirements and concluded the aerodynamic conceptual and preliminary design phases, high fidelity CFD simulations are performed, aiming to calculate the key aerodynamic and stability characteristics of the platform and to optimize its performance throughout the mission. More specifically, regarding the aerodynamic vehicle design, results concerning the calculation of stability derivatives, control surfaces sizing, trim analysis and flight envelope (V-n diagram) are presented, along with the respective methodologies. Considering the structural design of the aircraft, a combination of layout, FE simulations and parameterized design tools were employed, allowing the design and sizing of the skin and the internal structural parts. The parts are mainly made of composite and additively manufactured nylon materials. Coupled interaction loops are conducted among the aerodynamic and structural analyses to optimize the overall performance of the aerial vehicle, maximizing the aerodynamic efficiency, and reducing the structural weight. Finally, the study is concluded by the presentation of the manufactured prototype of the UAV, which satisfies all the structural, aerodynamic, stability and performance requirements for the established highway traffic monitoring mission. © Published under licence by IOP Publishing Ltd.

关键词： Intelligent systems

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Fatigue assessment of stress peened leaf springs supported by microstructural surface analyses

Fatigue assessment of stress peened leaf springs supported b...

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3rd International Conference of Engineering Against Failure, ICEAF 2013

作者： Savaidis, Georgios Karditsas, Stelios Savaidis, Alexander Stergioudi, Fani Michailidis, Nikolaos Aristotle University of Thessaloniki Department of Mechanical Engineering Laboratory of Machine Elements and Machine Design 54124 Thessaloniki Greece School of Pedagogical and Technological Education Dept. Mechanical Engineering Educators 14121 N. Heraklion Athens Greece Aristotle University of Thessaloniki Department of Mechanical Engineering Physical Metallurgy Laboratory 54124 Thessaloniki Greece

ISBN: (纸本)9789608810433

Taking high-performance parabolic steel leaves from serial springs used for the suspension of front axles of trucks as an example, the present paper focuses on the influence of the material, the heat treatment and the stress peening processes on the microstrucure, the surface properties (residual stresses, micro- and macro-hardness, roughness, decarburization zone and percentage) and, especially, the fatigue life of parabolic leaf springs. Hardnessess of the leaf core and surface, roughness profiles and residual stress profiles of both the stress peened and untreated leaf surfaces were determined to quantify the influence of the applied heat treatment and stress peening. Analytical calculations based on the FKM guideline were performed to evaluate every above mentioned fatigue life influencing factor. Comparison of the analytical results with the corresponding experimentally determined ones reveal the accuracy of the current theoretical tools.

关键词： Fatigue of materials

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Formalizing Selected Mechatronic Component's Constraints in SysML Models 49

Formalizing Selected Mechatronic Component's Constraints in ...

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49th Annual Conference of the IEEE Industrial Electronics Society, IECON 2023

作者： Vogel-Heuser, Birgit Hujo, Dominik Volpert, Marcus Landler, Stefan Otto, Michael Stahl, Karsten Zimmermann, Markus Technical University of Munich Tum School of Engineering and Design Institute of Automation and Information Systems Garching Germany Technical University of Munich Tum School of Engineering and Design Chair of Machine Elements Garching Germany Technical University of Munich Tum School of Engineerring and Design Laboratory for Product Development and Lightweight Design Garching Germany

ISBN: (纸本)9798350331820

One of the limitations of classical SysML is that it does not provide information on how to model system component's constraints, which can result in individual model solutions for the same elements. To address this issue, we propose utilizing the reference mechanism in SysML to refer to REXS and ECLASS data standards, which can unambiguously define characteristic properties. Environmental factors such as temperature or humidity constraints play a vital role in designing components of mechatronic systems, like transmissions, or electrical and electronic components like sensors and actuators. Mechatronic component's properties may change depending on temperature and humidity and may show degradation. Such information is provided to some extent in the component's classified properties, like ECLASS and/or REXS, the engineering tool to configure gears. Such properties and constraints are further detailed in specification sheets provided by the manufacturer, e.g., by multi-dimensional manufacturer-specific parametric curves which are proposed to be explicitly included in the modeling process as SysML constraints. The proposed approach allows to include additional, not yet standardized environmental effects such as dirt layers in a formalized way. The formalized properties are modeled in parametric diagrams of SysML. © 2023 IEEE.

关键词： Life cycle

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Continuous integrity monitoring of large transportation products using Acoustic Emission

Continuous integrity monitoring of large transportation prod...

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3rd International Conference of Engineering Against Failure, ICEAF 2013

作者： Tscheliesnig, Peter Savaidis, Georgios Baran, Ireneusz Jagenbrein, Andreas TÜV AUSTRIA SERVICES GMBH Department for Technical Physics Deutschstr. 10 1230 Vienna Austria Aristotle University of Thessaloniki Department of Mechanical Engineering Laboratory of Machine Elements and Machine Design 54124 Thessaloniki Greece Cracow University of Technology Faculty of Mechanical Engineering Laboratory of Applied Research al. Jana Pawla II 37 31-864 Cracow Poland

ISBN: (纸本)9789608810433

An advanced methodology for integrity monitoring of structures based on Acoustic Emission and follow-up non-destructive testing has been developed and verified in laboratory1, 2. Current research activities3 focus on application to large-scaled transportation products (ships, road tankers, railway cars). Monitoring during operation enables early detection of degradations (corrosion, fatigue cracks) and condition-based maintenance. Consequently, transportation of (hazardous) goods will become safer and economically compared to conventional time-based inspections. Main features of the developed monitoring technique are: (a) identification of degradation using FEA based on load data, (b) use of advanced and intrinsically safe AE equipment, redesigned for application at transport products, identification of degradation mechanisms and separation of background noises, (c) on-line acquisition, assessment and storage of AE signals, and (d) follow-up non-destructive testing for verification of degradations. The developed monitoring technique and its validation on test objects are presented. AE signals are assessed to identify and locate degradation mechanisms. The results reveal capability and accuracy of the proposed methodology in the large-scale application field.

关键词： Structural health monitoring

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A unified fatigue life calculation model for notched components based on elastic-plastic fracture mechanics

A unified fatigue life calculation model for notched compone...

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作者： Savaidis, G. Savaidis, A. Hertel, O. Vormwald, M. Aristotle University of Thessaloniki Department of Mechanical Engineering Laboratory of U Machine Elements and Machine Design GR-54124 Thessaloniki Greece Division of Mechanics Zografou Campus National Technical University of Athens GR-15773 Athens Greece Technische Universität Darmstadt Materials Mechanics Group Petersenstr. 12 D-64287 Darmstadt Germany

Based on Dankert's et al. [1] initial model for the elastic-plastic evaluation of fatigue crack growth in sheets providing elliptical notches, a generalized procedure enabling an improved evaluation of the effective ranges of the crack driving force (i.e. the J-Integral) as well as the application to arbitrary notched components has been developed [2], The present paper presents the basic topics of the calculation model as well as its verification using experimental results from notched specimens with various notch shapes subjected to cyclic loading with various load ratios.

关键词： Crack propagation

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Composite armor philosophy(CAP):Holistic design methodology of multi-layered composite protection systems for armored vehicles

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Defence Technology（防务技术） 2024年第11期41卷 181-197页

作者： Evangelos Ch.Tsirogiannis Foivos Psarommatis Alexandros Prospathopoulos Georgios Savaidis EODH SA Research and Development Department63080LakkomaChalkidikisGreece SIRIUS Department of InformaticsUniversity of OsloGaustadalleen 23B0373OsloNorway Physical Metallurgy Laboratory(PML) Mechanical Engineering DepartmentAristotle University of Thessaloniki54124ThessalonikiGreece Centre for Research&Development of Advanced Materials(CERDAM) Center for Interdisciplinary Research and InnovationBalkan CenterBuilding B’10th km Thessaloniki-Thermi Road57001ThessalonikiGreece Laboratory of Machine Elements&Machine Design School of Mechanical EngineeringAristotle University of Thessaloniki54124ThessalonikiGreece Digital Representation and Additive Manufacturing(DRAM) Center for Interdisciplinary Research and InnovationBalkan CenterBuilding B’10th kmThessaloniki-Thermi Road57001ThessalonikiGreece

A philosophy for the design of novel,lightweight,multi-layered armor,referred to as Composite Armor Philosophy(CAP),which can adapt to the passive protection of light-,medium-,and heavy-armored vehicles,is presented in this *** can serve as a guiding principle to assist designers in comprehending the distinct roles fulfilled by each *** CAP proposal comprises four functional layers,organized in a suggested hierarchy of *** notable is the inclusion of a ceramic-composite principle,representing an advanced and innovative solution in the field of armor *** paper showcases real-world defense industry applications,offering case studies that demonstrate the effectiveness of this advanced *** represents a significant milestone in the history of passive protection,marking an evolutionary leap in the *** philosophical approach provides designers with a powerful toolset with which to enhance the protection capabilities of military vehicles,making them more resilient and better equipped to meet the challenges of modern warfare.

关键词： Passive armor protection Composite armor Ballistic performance Protection systems Vehicle protection Armor design

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