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3D Methodology for Modeling and Analysis of Medium-Complexity Mechanical Assemblies: Application in Elevator-Car design

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3D RESEARCH 2012年第4期3卷 1-1页

作者： Karaoglanidis, Georgios A. Sapidis, Nickolas S. Univ Western Macedonia Dept Mech Engn GR-50100 Kozani Greece Aristotle Univ Thessaloniki Lab Machine Elements & Machine Design GR-54124 Thessaloniki Greece

This paper deals with design methods for medium-complexity mechanical systems, and focuses on two standard steps in such a method: "2D drawing" (included in the early stages of design) and "3D CADmodel simplification & defeaturing" (in the concluding "analysis stages" of a design procedure), whose contribution to mechanical design has always been a controversial subject. On the basis of the state-of-the-art in mechanical design, this "position paper" advocates complete elimination of the above two steps, and details the corresponding modified mechanical-design method. Application of this new design-method on a real-life industrial case (: elevator-car design) is fully analyzed, demonstrating the method's efficacy for medium-complexity mechanical assemblies.

关键词： design 3D CAD Integrated Analysis Elevator Lift Car and Defeaturing

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Modeling and fatigue assessment of weld start-end locations based on the effective notch stress approach

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MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK 2011年第4期42卷 298-305页

作者： Malikoutsakis, M. Savaidis, G. Aristotle Univ Thessaloniki Fac Mech Engn Lab Machine Elements Machine Design Thessaloniki 54124 Greece

The present paper contains a methodology for modeling and life assessment of fatigue loaded welded components providing distinct weld start and end locations. The proposed methodology follows the IIW recommendation regarding modeling and finite element meshing of weld toe and root by means of an effective notch radius and uses the corresponding Wohler curve (FAT class) to assess the durability. Geometrical singularities and, therewith, numerical discontinuities, can be overcome especially when 3D weld root problems are treated. The fatigue life assessment is performed on the basis of normal stresses acting at the failure-critical weld toe and root locations. Comprehensive experimental database containing stress and fatigue life results derived from motor truck's hypoid rear axles providing complex 3D welds subject to vertical, longitudinal, and torsional loading is used to verify the calculation accuracy of the proposed methodology. The agreement between experimentally determined and calculated fatigue results is satisfactory.

关键词： Fatigue Welds Local Concepts Weld-Ends

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Theoretical and Experimental Analysis of a Laser Textured Thrust Bearing

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TRIBOLOGY LETTERS 2011年第3期44卷 335-343页

作者： Marian, Victor Gabriel Gabriel, Dumitru Knoll, Gunter Filippone, Salvatore Univ Politehn Bucuresti Lab Machine Elements & Tribol Bucharest 060042 Romania BCI Grp CH-2540 Grenchen Switzerland Univ Kassel Inst Engn Design & Machine Elements D-34109 Kassel Germany Univ Roma Tor Vergata Dept Mech Engn I-00133 Rome Italy

In this article, a laser partially textured thrust bearing is theoretically and experimentally analyzed. An adiabatic model is developed in order to theoretically investigate the performances of the bearing. The bearing sample is partially textured both in radial and circumferential direction using the laser texturing process. The performance of the bearing (fluid film thickness and friction torque) is evaluated on a specially adapted test rig and the experimental results are compared with the theoretical model. A good agreement is found between the theoretical model and the experimental data. Also a comparison between a laser textured bearing and a bearing textured using the photolithographic method is presented.

关键词： Hydrodynamic lubrication Hydrodynamic bearings Surface modification Thermal effects in hydrodynamics

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design Optimization of Components Based on Material Mechanics Fatigue Concepts

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MATERIALS TESTING 2011年第3期53卷 136-143页

作者： Savaidis, Georgios Tech Univ Darmstadt Inst Stahlbau & Werkstoffmech Thessaloniki Greece MAN Nutzfahrzeuge Munchen Dept Fatigue & Test Rigs Thessaloniki Greece Aristotle Univ Thessaloniki Dept Mech Engn Lab Machine Elements & Machine Design GR-54006 Thessaloniki Greece

The paper deals with the fatigue design concepts for engineering components based on material properties and mechanics, i.e. the Short Crack Model (SCM), the Local Strain Approach (LSA), and the Effective Notch Stress Concept (ENSC) for welds. The calculation procedures are presented and their accuracy and robustness are demonstrated on the example of a cab bearing console providing complex geometry (geometry notch, weld with pronounced start and ends) and subjected to operating loading with variable stress amplitudes and mean stresses. Parametrical studies considering two ductile steels were performed. Comparison of calculated curves by means of the SCM and the LSA supported by the P-SWT-parameter explores life factors of 3 to 6.7 emphasizing the crucial influence of load sequence effects on fatigue life and the usefulness of the SCM to consider them. The choice of the material influences the lifetime of the console significantly (life factors of 5 to 11 depending on the applied model). The weld design was assessed by the ENSC to be safe.

关键词： Welds

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Wear and smearing resistance of black iron mixed oxide coated steels

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INTERNATIONAL JOURNAL OF SURFACE SCIENCE AND ENGINEERING 2010年第4-6期4卷 337-359页

作者： Mihailidis, A. Salpistis, C. Panagiotidis, K. Sachanas, C. Gatsios, S. Aristotle Univ Thessaloniki Lab Machine Elements & Machine Design Thessaloniki 54124 Greece

Surface coatings increase the wear and smearing resistance of a machine element. Nevertheless, most of the coating processes are expensive and time-consuming. By contrast, Schaeffler's Durotect (R) B coating seems attractive regarding production expenditure and price. However, the literature about the behaviour of this coating is very limited. This paper describes the experimental setup and the experiments that were carried out in order to evaluate the wear and smearing resistance of the Durotect (R) B coated 100Cr6 steel in reference to plain 100Cr6 through hardened steel. Durotect (R) B is a mixed black iron oxide coating developed by Schaeffler especially for use in machine elements. The main measured parameters (mass loss, smearing slide-to-roll ratio, friction and normal force, surface roughness and bulk temperature) are presented. Comparative charts of the monitored parameters are given and discussed. It is concluded that this coating decreases friction coefficient and improves both the smearing and wear resistance.

关键词： black iron mixed oxide coating Durotect (R) B bluing friction coefficient running-in wear rate smearing two discs test rig solid contact time percentage mixed lubrication surface coating

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Influence of the bushing geometry on the thermohydrodynamic performance of a misaligned journal bearing

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY 2010年第J1期224卷 37-53页

作者： Mihailidis, A. Bakolas, V. Panagiotidis, K. Poulios, K. Sachanas, C. Aristotle Univ Thessaloniki Lab Machine Elements & Machine Design Thessaloniki 54124 Greece Schaeffler KG Corp Basic Projects & Long Term Qual Bearing Fundamentals Herzogenaurach Germany

Often journal bearings have to support shafts that run misaligned into the bushing bore because of the combined effect of elastic deformations and manufacturing tolerances. In such cases, the thermo-hydrodynamic behaviour of the bearing needs to be investigated in detail in order to ensure the safe operation of the device, or, in other words, to avoid asperities contact. The difficulties to model the thermal phenomena comprise one of the main reasons for the limited contribution of theoretical models to the designing efforts. In this article an accurate thermo-hydrodynamic simulation of journal bearings operating under misalignment conditions is introduced at first. Then, the computed film thickness, pressure and temperature distribution, as well as the friction coefficient are shown for several variations of hour-glass profiled bearings operating under a misalignment of up to 5'. From the results shown it can be concluded that the load-carrying capacity of journal bearings can be greatly enhanced if a properly selected hourglass design is applied. The results show further that a three-dimensional thermo-hydrodynamic analysis, as the one shown here, should always be carried out in order to verify the bushing design.

关键词： journal bearing thermo-hydrodynamic lubrication misalignment multi-grid method

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Theoretical and experimental analysis of a partially textured thrust bearing with square dimples

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY 2007年第J7期221卷 771-778页

作者： Marian, V. G. Kilian, M. Scholz, W. Polytech Univ Lab Machine Elements & Tribol Dept Machine Elements & Tribol Bucharest 060042 Romania Univ Kassel Inst Engn Design & Machine Elements Kassel Germany Univ Kassel Inst Nanostruct Technol & Analyt Kassel Germany

Surface texturing has proved to be very efficient in full and mixed lubrication, reducing the friction coefficient and the wear rate of mating surfaces. By partially texturing the inlet zone of a thrust washer pad load carrying capacity is generated in the system. In the present paper, a partially textured thrust bearing with square dimples is analysed theoretically using a thermo-hydrodynamic model. The equations are solved numerically by the finite-difference method. The bearing was realized by the photolithographic method and the theoretical results (fluid film thickness and friction torque) were compared with the experimental data obtained on the test rig. It is found that an optimal number of 12 sectors maximize the load carrying capacity of the bearing. The optimal textured fraction, which maximizes the load carrying capacity is 0.5 on the circumferential direction and 0.9-1 on the radial direction. A good correlation was found between the theoretical and experimental results for the two measured parameters (fluid film thickness and friction torque).

关键词： hydrodynamic lubrication thrust bearings surface texturing thermal effects in hydrodynamics

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Calibration of phase shifter in phase-shifting shearography

Calibration of phase shifter in phase-shifting shearography

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Conference on Interferometry XIII

作者： Gan, Y. Steinchen, W. Univ Kassel Inst Machine Elements & Engn Design Dept ME Lab Photoelastic Holog Shearog Moenchebergstr 7 D-34125 Kassel Germany

ISBN: (纸本)081946371X

The temporal phase shifting method (TPS) is the most powerful technique in phase-shifting shearography. Numerous different phase-shifting algorithms have been developed to determine phase distribution for different applications. Most of them are applied with known phase shifts. In these cases, the accuracy of quantitative measurement using phase-shifting technique depends strongly on the accuracy of the phase shifter e.g. a piezoelectric transducer (PZT) which is responsible for generating the known phase shifts. Thus, phase shifter has to be calibrated. A new calibration method based on the so-called advanced iterative algorithm which provides stable convergence and accurate phase distribution with minimum three randomly shifted interferograms will be proposed in this paper. A fully automatic calibration procedure for calibrating of desired phase shifts and for evaluating the characteristic curve of phase shift over voltage change will also be presented.

关键词： speckle interferometry phase-shifting shearography calibration

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Correlation between model test devices and full bearing tests under grease lubricated conditions

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IUTAM Symposium on Elastohydrodynamics and Microelastohydrodynamics

作者： Baly, H Poll, G Cann, PM Lubrecht, AA Leibniz Univ Hannover Inst Machine Elements Engn Design & Tribol D-301671 Hannover Germany Imperial Coll London Dept Engn Mech Tribol Sect London SW7 2AZ England CNRS 5514 INSA UMR Lab Mecan Contacts & Solides F-75700 Lyon France

ISBN: (纸本)1402045328

This paper compares friction and film thickness measurements from a full-scale bearing test device and optical ball-on-disc results. The lubricants used were commercial greases with a range of base oil viscosities and thickeners formulated for high-speed applications. The bearing tests operated in the semi-starved regime over most of the speed range. The film thickness evolution shows the similarity in starvation curves, as well as the influence of the running-in speed, on subsequent runs. Indirectly the paper shows the influence of spin on relubrication and that lubricant reflow occurs primarily in the vicinity of the contact.

关键词： rolling element bearings grease lubrication friction starvation

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Subsurface stress field of a dry line contact

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WEAR 2001年第7期249卷 546-556页

作者： Mihailidis, A Bakolas, V Drivakos, N Aristotle Univ Thessaloniki Lab Machine Elements & Machine Design Dept Mech Engn GR-54006 Thessaloniki Greece INA Walzlager Schaeffer CAE Dev Anal & Simulat D-91074 Herzogenaurach Germany

The calculation of the pressure distribution and the subsurface stress field developed at the dry line contact of two cylinders, can be carried out with sufficient accuracy, using the Hertzian theory assuming that both cylinders are smooth. However, for the investigation of surface failures, such as micro-pitting, Hertz's solution cannot be applied, because the effect of roughness is significant. This paper presents a model for the determination of the asperity pressure distribution at the contact of two rough cylinders, assuming elastic-perfectly plastic deformation. Having determined the surface load, the subsurface stress field is then calculated. The effect of roughness on the stress field is investigated. For this investigation, numerically generated rough surfaces are used. The results show that the maximum shear stresses developed in small depths are significantly higher than those predicted by the Hertzian solution. This conclusion is in good agreement with the small depth of cracks observed on the flanks of gears that have suffered from micro-pitting. (C) 2001 Elsevier Science B.V All rights reserved.

关键词： micro-pitting real pressure distribution subsurface stress field surface roughness

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