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    - CHEMICAL ENGINEERING (161 journals)
    - CIVIL ENGINEERING (154 journals)
    - ELECTRICAL ENGINEERING (86 journals)
    - ENGINEERING (1135 journals)
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    - INDUSTRIAL ENGINEERING (52 journals)
    - MECHANICAL ENGINEERING (75 journals)

ENGINEERING (1135 journals)            First | 1 2 3 4 5 6 7 8 | Last

Developments in Clay Science     Full-text available via subscription  
Developments in Geotechnical Engineering     Full-text available via subscription   (Followers: 1)
Developments in Mineral Processing     Full-text available via subscription   (Followers: 1)
Diálogos Interdisciplinares     Open Access  
Diamond Light Source Proceedings     Full-text available via subscription  
Digital Signal Processing     Hybrid Journal   (Followers: 7)
Discrete Optimization     Full-text available via subscription   (Followers: 4)
Doct-Us Journal     Open Access  
Documents pour l'histoire des techniques     Open Access   (Followers: 1)
Dyes and Pigments     Hybrid Journal   (Followers: 3)
Dyna     Open Access  
Dynamical Systems: An International Journal     Hybrid Journal   (Followers: 1)
El Hombre y la Máquina     Open Access  
Electromagnetics     Hybrid Journal   (Followers: 1)
Electrophoresis     Hybrid Journal   (Followers: 5)
Elsevier Geo-Engineering Book Series     Full-text available via subscription   (Followers: 2)
Elsevier Ocean Engineering Series     Full-text available via subscription   (Followers: 1)
Embedded Systems Letters, IEEE     Hybrid Journal   (Followers: 18)
Energies     Open Access   (Followers: 2)
Energy and Power Engineering     Open Access   (Followers: 9)
Energy Conversion and Management     Hybrid Journal   (Followers: 8)
Energy Engineering     Full-text available via subscription   (Followers: 9)
Energy for Sustainable Development     Hybrid Journal   (Followers: 9)
Energy Procedia     Open Access   (Followers: 3)
Energy Science & Engineering     Open Access   (Followers: 4)
Energy Science and Technology     Open Access   (Followers: 12)
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects     Hybrid Journal   (Followers: 2)
Energy Sources, Part B: Economics, Planning, and Policy     Hybrid Journal   (Followers: 6)
Energy Systems     Hybrid Journal   (Followers: 10)
ENGEVISTA     Open Access  
ENGI : Revista Electrónica de la Facultad de Ingenieria     Open Access  
Engineer : Journal of the Institution of Engineers, Sri Lanka     Open Access  
Engineering     Open Access   (Followers: 2)
Engineering & Technology     Hybrid Journal   (Followers: 17)
Engineering Analysis with Boundary Elements     Hybrid Journal   (Followers: 1)
Engineering Computations     Hybrid Journal   (Followers: 3)
Engineering Economics     Open Access   (Followers: 4)
Engineering Economist, The     Hybrid Journal   (Followers: 2)
Engineering Education     Open Access   (Followers: 1)
Engineering Failure Analysis     Hybrid Journal   (Followers: 27)
Engineering Geology     Hybrid Journal   (Followers: 7)
Engineering Journal     Open Access   (Followers: 1)
Engineering Management Journal     Hybrid Journal   (Followers: 12)
Engineering Management Research     Open Access   (Followers: 4)
Engineering Management Reviews     Open Access   (Followers: 1)
Engineering Optimization     Hybrid Journal   (Followers: 6)
Engineering Sciences     Open Access  
Engineering Studies     Hybrid Journal  
Engineering With Computers     Hybrid Journal   (Followers: 5)
Engineering, Technology & Applied Science Research     Open Access  
Entramado     Open Access  
Entropy     Open Access   (Followers: 3)
Environmental & Engineering Geoscience     Full-text available via subscription   (Followers: 2)
Environmental and Ecological Statistics     Hybrid Journal   (Followers: 5)
Environmetrics     Hybrid Journal  
Épités - Épitészettudomány     Full-text available via subscription   (Followers: 1)
EPJ Photovoltaics     Open Access   (Followers: 1)
Épsilon     Open Access  
Ergonomics in Design: The Quarterly of Human Factors Applications     Hybrid Journal   (Followers: 6)
ESAIM: Control Optimisation and Calculus of Variations     Full-text available via subscription  
ESAIM: Mathematical Modelling and Numerical Analysis     Full-text available via subscription   (Followers: 2)
ESAIM: Proceedings     Open Access  
Estuaries and Coasts     Hybrid Journal   (Followers: 3)
European Journal of Combinatorics     Full-text available via subscription   (Followers: 3)
European Journal of Engineering Education     Hybrid Journal   (Followers: 2)
European Journal of Lipid Science and Technology     Hybrid Journal   (Followers: 1)
European Journal of Mass Spectrometry     Full-text available via subscription   (Followers: 10)
European Medical Device Technology     Full-text available via subscription   (Followers: 2)
European Physical Journal - Applied Physics     Full-text available via subscription   (Followers: 5)
European Transport Research Review     Open Access   (Followers: 10)
Evolutionary Intelligence     Hybrid Journal  
Evolving Systems     Hybrid Journal  
Exacta     Open Access  
Experimental Techniques     Hybrid Journal   (Followers: 30)
Experiments in Fluids     Hybrid Journal   (Followers: 6)
Fibers and Polymers     Full-text available via subscription   (Followers: 3)
Filtration & Separation     Full-text available via subscription   (Followers: 2)
Finite Fields and Their Applications     Full-text available via subscription   (Followers: 2)
Fire Science Reviews     Open Access   (Followers: 2)
First Monday     Open Access   (Followers: 208)
Flexible Services and Manufacturing Journal     Hybrid Journal   (Followers: 1)
Flow, Turbulence and Combustion     Hybrid Journal   (Followers: 17)
Fluid Dynamics     Hybrid Journal   (Followers: 5)
Fluid Dynamics Research     Full-text available via subscription   (Followers: 7)
Fluid Phase Equilibria     Hybrid Journal   (Followers: 1)
Focus on Catalysts     Full-text available via subscription  
Focus on Pigments     Full-text available via subscription   (Followers: 4)
Focus on Powder Coatings     Full-text available via subscription   (Followers: 3)
Focus on Surfactants     Full-text available via subscription   (Followers: 4)
Food Engineering Reviews     Hybrid Journal   (Followers: 2)
Food Science and Technology     Open Access  
Formación Universitaria     Open Access   (Followers: 3)
FORMakademisk     Open Access  
Formal Methods in System Design     Hybrid Journal   (Followers: 6)
Forschung     Hybrid Journal  
Forschung im Ingenieurwesen     Hybrid Journal  
Foundations and Trends in Systems and Control     Full-text available via subscription  
Foundations and Trends® in Communications and Information Theory     Full-text available via subscription   (Followers: 6)
Foundations and Trends® in Electronic Design Automation     Full-text available via subscription  
Foundations of Science     Hybrid Journal  

  First | 1 2 3 4 5 6 7 8 | Last

Journal Cover Forschung im Ingenieurwesen
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1434-0860 - ISSN (Online) 0015-7899
     Published by Springer-Verlag Homepage  [2210 journals]   [SJR: 0.131]   [H-I: 10]
  • Varianten des Zweizonen-Modells von Ludwig Prandtl für den
           Wärmeübergang beim turbulent durchströmten Rohr
    • Abstract: Zusammenfassung Eine direkte Berechnung des Temperaturprofils eines strömenden Fluids zur Ableitung von Wärmeübergangskoeffizienten ist nur in wenigen Ausnahmefällen möglich. In einigen Fällen hilft man sich durch Analogiebetrachtungen, wie z. B. der Analogie zwischen Impuls- und Wärmeübertragung bei der vollturbulenten Rohrströmung. Diese auf W. Reynolds und L. Prandtl zurückgehende Analogie nutzt fluiddynamische Ansätze, um auf den Wärmeübergang zwischen Fluid und Wandoberfläche zu schließen. Im Beitrag wird das gut bekannte Zweizonen-Modell von Prandtl analysiert und mit einem Dreibereiche-Modell verglichen. Es wird ein korrigiertes Modell abgeleitet, welches Vorteile gegenüber dem klassischen Zweizonen-Modell nach Prandtl aufweist.
      PubDate: 2014-10-10
  • New design and construction of expandable casing tubes
    • Abstract: Abstract Exploration for deep-geothermal resources is still a costly and high risk operation. The research association “Geothermal Energy and High Performance Drilling Research Program, gebo” was founded to improve the cost effectiveness of geothermal energy production in particular by developing new drilling concepts for deep geological layers. A mono-diameter borehole casing concept is developed to achieve this ambitious aim. To accomplish this, a special type of casing is essential, structured from folded tubulars for expandable casing applications featuring clover-like cross sections and expandable to a cylindrical form when the casing is at its downhole position. A smaller borehole volume and a reduction of drilling time and casing related costs are the main advantages of this method compared to conventional drilling. Design, material selection and realization of the folded tubulars take place at the Institut für Werkstoffkunde (Materials Science). The evaluations of the results are based on residual stress analysis and the measurement of the geometry after each deformation step at the Institute of Production Engineering and Machine Tools (IFW).
      PubDate: 2014-10-10
  • Spray cooling of extruded EN AW-6082 aluminium alloy sheets: spatial heat
           transfer coefficients
    • Abstract: Abstract Quenching profiles during their extrusion with subsequent ageing can increase their strength by a factor of 1.5–2 compared to the as-extruded state. Water-air spray cooling is a quenching technology which allows the desired profile temperature to be reached with high accuracy and which is characterised by low energy demand. To apply this cooling technique correctly, the heat transfer coefficient’s dependence on the surface temperature and properties of the extruded profile, made from EN AW-6082 alloy, and on the spray cooling parameters was determined using the lumped heat capacitance method. The absence of a significant impact of the spraying distance and inclination angle on the average heat transfer coefficient within the investigated range was noted. Dependencies of the relative heat transfer coefficient on the temperature and the distance to the spray axis were derived. It was shown that these dependencies, which can be used for modelling such processes, are practically identical for all considered spraying parameters.
      PubDate: 2014-10-08
  • Influence of the shape of the blade tip on the emitted noise in the
           air-gap between the rotor and the housing of an axial fan
    • Abstract: Abstract The paper presents influence of the rotor blade tip shape of an axial fan on the emitted noise and on its aerodynamic characteristic. Appropriate measurements were first performed on the integral level of the same rotor with the two blade tip shapes: blade tip configuration A where the blade tip has the form of the prolonged basic blade, and configuration B with the winglet where the tip was slightly pushed towards the suction side of the blade. Moreover results of local pressure and sound pressure measurements in the area of the air gap made possible detailed analysis of the avarage pressure distribution and its time variance. The results showed strong dependence of the blade tip design on the emitted noise distribution, whereas changes of the aerodynamic characteristic with both tip designs were hardly noticed. The correlation between the emitted sound power level of the fan and the air pressure variance enabled to locate mechanism and origin of the noise generation in the zone between two consecutive rotor blades.
      PubDate: 2014-10-07
  • Numerical analysis of the twin-roll casting of thin aluminium-steel clad
    • Abstract: Abstract The production of thin aluminium-steel clad strips by means of twin-roll casting is one of the prospective trends in the development of sheet production. The main advantages of twin-roll casting are low specific energy and resource consumption. Besides this, the resulting compound has a high bonding strength owing to the presence of a continuous thin layer of intermetallic phases having an approximate thickness of 3 µm at the interface of the two metals. At the same time, the quality of the clad strip depends on the microstructure and properties of the aluminium layer formed directly from a melt. A deformation immediately following the solidification of the metal between the two rotated, internally water-cooled rolls has a substantial influence on this aluminium layer. Due to the complexity of observing the processes occurring in the melt pool, a numerical simulation became one of the main methods for their investigation. Simulation is widely used to describe the process of twin-roll casting of monomaterial strips, but so far it has not been used for to comprehensively analyse the process of twin-roll casting of clad strips. In the present paper, a two-dimentional finite-element simulation of the system “clad strip—water-cooled rolls” using the ANSYS software is proposed. A joint analysis is carried out of the heat transfer, viscous flow of aluminium melt, its solidification and deformation resulting in the temperature distribution in the cast metal as well as in the tool. The dependences of the deformation strain and outlet temperature of the clad strip on the main technological process parameters; obtained by numerical simulation, are shown.
      PubDate: 2014-10-07
  • Zur Anwendbarkeit des Massenstrom-Modells nach ISO 6358 mit den
           Kennwerten Leitwert C und kritisches Druckverhältnis b für Gase
           im Hochdruckbereich bis 300 bar
    • Abstract: Zusammenfassung Massenstrom-Modelle für gasförmige Medien beschreiben den Zusammenhang zwischen Gasdurchfluss durch Drosselelemente in Abhängigkeit der Eingangsgrößen Druck, Temperatur und Medium. Diese Modelle werden verwendet, um pneumatische Komponenten zu berechnen, pneumatische Systeme zu simulieren oder Anlagen zu planen. Im Gegensatz zum realen Gas sind für ideale Gase einige Massenstrom-Modelle bekannt und verifiziert, wie z. B. nach ISO 6358 (International Standard ISO 6358: pneumatic fluid power – components using compressible fluids – determination of flow-rate characteristics, 1989). Bei der Entwicklung und Anwendung von Systemen mit realen Gasen, z. B. bei der Berechnung von Sicherheitsventilen, wurde festgestellt, dass Gleichungen – ohne Berücksichtigung der Realgaseigenschaften – nur eingeschränkt nutzbar sind, wie auch Schmidt et al. (Forschung im Ingenieurwesen 73:105–117, 2009) feststellten. Mit dieser Veröffentlichung soll ein Beitrag geleistet werden, um für die Berechnung des Massenstroms im Zustandsgebiet realer Gase ein einfach anwendbares Modell bereitzustellen. Dazu wird das bestehende Massenstrom-Modell nach ISO 6358, das auf Gleichungen für den idealen Gasbereich basiert, für ein reales Gas angewendet und verifiziert. Die Parameter kritischer Leitwert C und kritisches Druckverhältnis b werden im Zustandsbereich realer Gase bestimmt, angewendet und Abweichungen aufgezeigt. Die mittlere Abweichung zwischen gemessenem und berechnetem Massenstrom liegt im Realgasbereich bei 1,0 %. Daher wird das Massenstrom-Modell nach ISO 6358 als geeignet vorgeschlagen, sofern die Parameter C und b im Realgasbereich identifiziert werden. Zusätzlich wurde untersucht, dass Abweichungen von über 10 % entstehen, wenn die Parameter C und b bei idealem Gas bestimmt und im realen Gasbereich angewendet werden. Diese hohe Abweichung kann mit einer iterativen Berechnung unter Verwendung von realen Zustandsdaten des verwendeten Gases teilweise kompensiert werden, so dass die Abweichung auf 4,3 % sinkt.
      PubDate: 2014-10-07
  • Rise of oil drops in water and fall of water drops in oil
    • Abstract: Abstract Rise and fall velocities of oil drops in water and water drops in oil, respectively, are measured in a liquid column. The main perspective is on the similarity of the flows in these largely different cases. When the experimental data are plotted as the normalized rise velocity, which is the Reynolds number, versus the Archimedes number a common curve appears. This proves that similarity exists at least with respect to the velocity. Larger drops deviate considerably from the spherical shape. Nevertheless the data set can be represented by a formula derived from data on hard spheres. In particular the Stokes limit for Re→0 is nicely confirmed by measuring down to 10− 4.
      PubDate: 2014-08-26
  • Auslegung von Probekörpern aus Hartschaum zur Ermittlung der
           biaxialen Zugfestigkeit
    • Abstract: Zusammenfassung Harte Polymerschäume haben mittlerweile eine breite Anwendung gefunden. Ihre Auslegung basiert allerdings auf Festigkeitswerten, die aus Versuchen an Probekörpern unter Zug-, Druck-, Torsions- und hydrostatischer Druckbelastung gewonnen werden. Für die materialgerechte Validierung einer Festigkeitshypothese sind weitere Beanspruchungszustände erforderlich. Dies gilt speziell für mehraxialen Zug: Es liegen bisher fast keine Messungen für gleichmäßige biaxiale und hydrostatische Zugbelastungen vor. Zuerst wird ein geeigneter Versuchsaufbau erarbeitet, der sich mit einer konventionellen Zugprüfmaschine realisieren lässt. Neben dem gleichmäßigen biaxialen Spannungszustand können dabei weitere biaxiale Spannungszustände beim Zug erzeugt werden. Das einfache Schema der Kraftverteilung erfordert eine spezielle Form des Probekörpers. Die folgende Ausarbeitung beschreibt die Auslegung von zwei verschiedenen Probekörpern aus Hartschaum. Dafür wird Hartschaum als quasihomogener isotroper Werkstoff betrachtet. Für die Auslegung der Probekörper wird vom linear-elastischen Verhalten des Materials ausgegangen. Zur Bewertung der mehraxialen Spannungszustände wird die Festigkeitshypothese von Mohr–Coulomb herangezogen. Die maximalen Spannungen, die in den Kerben zwischen den Stellen der Krafteinleitung entstehen, werden durch die Geometrie des Probekörpers minimiert, so dass ein Versagen im Prüfbereich gewährleistet ist. Die Abmessungen der Probekörper werden an die kommerziell hergestellten Schaumblöcke angepasst. Hydrostatische Zugbelastung bis zum Versagen lässt sich kaum realisieren. Ausgehend von den Versuchsergebnissen beim Zug und beim gleichmäßigen biaxialen Zug wird die Abschätzung der hydrostatischen Bruchspannung (Grenzspannung) vorgeschlagen.
      PubDate: 2014-05-27
  • Elastic-plastic states of a radially heated thick-walled cylindrically
           curved panel
    • Abstract: Abstract A cylindrically curved panel in a state of plane strain subject to a radial temperature gradient is investigated. The ends of this thick-walled shell are presupposed to be guided in such a way that a displacement in circumferential direction may occur and that the radius of the initial middle surface remains unchanged. Then, couples act on those ends, giving rise to pure bending conditions. For a material obeying Tresca’s yield criterion and the flow rule associated with it, elastic-plastic states occurring for a heated inner and/or outer surface are studied in detail. Moreover, the residual stresses after cooling are discussed.
      PubDate: 2014-05-01
  • Comparison of a vehicle equipped with Electronic Stability Control (ESC)
           to a vehicle with Four Wheel Steering (4WS)
    • Abstract: Abstract Electronic Stability Control (ESC) and Four Wheel Steering (4WS) have been used to control the yaw rate and sideslip angle of automobiles, in order to improve stability and prevent accidents. The scope of this paper is to compare the behaviour of a vehicle equipped with no control systems, to a vehicle equipped with ESC, a vehicle equipped with 4WS and a vehicle equipped with a combination of ESC and 4WS in a series of simulated tests, using an adequate vehicle and driver model. The operating parameters of the control systems and the driver model have been optimised by using an evolution strategy. According to the results, the vehicle equipped with 4WS performed better in open-loop tests, while the vehicle equipped with ESC performed better in closed-loop tests where the vehicle is controlled by the driver model. The vehicle equipped with a combination of ESC and 4WS has achieved consistently better results in all our tests and has shown that the use of 4WS systems can augment the operation of ESC system and achieve a better safety level for future vehicles.
      PubDate: 2014-05-01
  • Mathematical rotordynamic model for lateral vibration analysis of
           induction motors with dynamic eccentricities regarding start-up
    • Abstract: Abstract The paper shows a mathematical rotordynamic model for lateral vibration analysis of induction motors with dynamic eccentricities regarding start-up. With this mathematical model, different kinds of dynamic eccentricities—mass eccentricity, magnetic eccentricity and bent rotor deflection—can be analyzed. Beside the mechanical influences—e.g. the rotor mass, rotor shaft stiffness, oil film coefficients of the sleeve bearings, structural stiffness of the sleeve bearing housings and end shields—also electromagnetic influence—e.g. the electromagnetic field and magnetic eccentricity—can be analyzed for the start-up. The paper is based on the well-known theory of accelerated resonance passing and is an enhancement of the theory for induction motors, considering also electromagnetism during start-up. Based on this rotordynamic model, the absolute displacements of the shaft centre, the shaft journals and the sleeve bearing housings can be analyzed as well as the relative displacements between the shaft journals and the sleeve bearing housings. Additionally, also the vibration velocities at the sleeve bearing housings can be derived. The aim of the paper is not to replace a detailed finite-element-model by a simplified analytical model, but to show the mathematical coherences between rotordyamics and electromagnetics for a start-up of an induction motor, considering different dynamic eccentricities.
      PubDate: 2014-05-01
  • Using Turbocharger maps in gas exchange simulation and engine control
    • Abstract: Abstract Characterisation of turbocharger performance is important in gas exchange simulation and engine control unit calibration. Compressor and turbine performance maps are measured on a hot-gas test bed. As a result their performance maps have a large dependence on heat transfer. Gas exchange simulation software assumes adiabatic compressor and turbine maps. The direct use of measured maps leads to defective simulation results. The power balance of compressor and turbine in steady state operation leads to limited turbine performance maps. The acceleration of compressor and turbine are not covered in those maps. In gas exchange simulation the performance maps are extrapolated to cover the entire range of operation. Simulations using the extrapolated maps do not correlate with empirical results. This paper presents methods for reconciling results derived from maps with those observed in the real world over the same extrapolated operating range. The methods use existing maps without additional information to construct performance maps relevant for operation on internal combustion engines. A recipe approach for the application to measured maps is developed and applied to examples. Compared to mathematical extrapolation, the presented methods yield empirically sound extrapolations and improve the quality of gas exchange simulation results.
      PubDate: 2014-05-01
  • Kontaktwechselwirkung einer Rohrleitung mit der Reparaturbandage aus einem
    • Abstract: Zusammenfassung In der vorliegenden Arbeit wird die Kontaktaufgabe über die Wechselwirkung einer langen Zylinderschale mit einer koaxialen zylindrischen Bandage aus einem Verbundwerkstoff untersucht. Der Verbundwerkstoff wird als ein homogenes orthotropes Material mit bekannten effektiven elastischen Eigenschaften modelliert. Basierend auf der klassischen Schalentheorie werden die Grundgleichungen für die Kontaktaufgabe sowie allgemeine Lösungen für die Durchbiegungen und Schnittgrößen formuliert. Die unbekannten Integrationskonstanten sowie die Kontaktfläche werden numerisch mit Hilfe des Programmpakets Maple ermittelt. Drei charakteristische Längen der Bandage, bei denen der Übergang von einem Kontaktschema der Wechselwirkung zu einem anderen erfolgt, wurden ermittelt. Es wurde festgestellt, dass die Änderung des Innendrucks nicht zum Übergang von einem Kontaktschema zu einem anderen führt. Der Charakter der Kontaktwechselwirkung wird durch geometrische Parameter der Verbindung und elastische Materialeigenschaften der Schale und der Bandage bestimmt.
      PubDate: 2014-05-01
  • Key features of flexure hinges used as rotational joints
    • Abstract: Abstract This article is supposed to serve as a guide for the design of flexure hinges that act as rotational joints. Firstly, flexure hinges with concentrated and distributed compliance are reviewed. They can be modeled by linear beam theories or by the theory of Elastica, respectively. Secondly, the transition between these limit cases is investigated by finite element methods (FEM). A planar symmetric flexure hinge with a circular notch serves as an exemplary geometry. By extending the notch the compliance is distributed. The deflection curves and the kinetics of desired and parasitic motions are chosen as key features to be studied. The corresponding results are compressed into a pseudo-rigid-body model (PRBM) approximation for a range of geometries. It turned out that the concentrated compliance matches best with an ideal rotational joint, but even for small displacements large stresses occur so that its range of operation is small. Distributing the compliance increases the range of operation, however stiffness within the task space decreases dramatically so that the design of a flexure hinge becomes a tradeoff between the two concurring goals large stiffness and large range of operation.
      PubDate: 2013-10-23
  • Bildung von geordneten Konstruktionsfamilien unter Anwendung von
    • Abstract: Zusammenfassung Die Theorie der Konstruktionsähnlichkeit basiert auf der Theorie der physikalischen Ähnlichkeit. Das primäre Ziel dieser Arbeit ist eine derartige Auswahl von Konstruktionsmerkmalen in den einzelnen Typengrößen der Typenreihen, um identische: physikalische, stereomechanische aber auch einfache Zustände, wie in der Grundkonstruktion, zu erhalten. Die Grundaufzeichnungsform einer Konstruktion einer Typenreihe ist die programmierbare, grafische und relationale Parametrisierung.
      PubDate: 2013-10-18
  • On the determination of natural frequencies of a cantilever beam in free
           bending vibration: a rigid multibody approach
    • Abstract: Abstract A new approximate method for the determination of natural frequencies of a cantilever beam in free bending vibration by a rigid multibody system is proposed. Uniform Euler-Bernoulli cantilever beams with and without a lumped mass at the tips are considered. The modelling method consists of two steps. In the first step, the cantilever beam is replaced by lumped masses interconnected by massless flexible beams. In the second step, the massless flexible beams are replaced by massless rigid beams connected through revolute and prismatic joints with corresponding springs in them. Elastic properties of the massless flexible beams are modelled by the springs introduced. The method proposed is compared with similar ones in the literature.
      PubDate: 2013-10-08
  • Aufbau und Validierung eines Prozesskraftmodells für das
           kontinuierliche Wälzschleifen von Stirnradverzahnungen
    • Abstract: Zusammenfassung Zur Verbesserung der Tragfähigkeit und der Laufruhe von Verzahnungen ist es Stand der Technik, einsatzgehärtete Verzahnungen nach der Wärmebehandlung abschließend hartfein zu bearbeiten. Eine Möglichkeit für die Hartfeinbearbeitung ist das kontinuierliche Wälzschleifen, das aufgrund der hohen Produktivität ein industriell etablierter Prozess ist. Trotz des weitreichenden industriellen Einsatzes liegen bisher nur begrenzt wissenschaftliche Kenntnisse über das kontinuierliche Wälzschleifen von Verzahnungen vor. Ein Grund dafür sind die komplexen Kontaktbedingungen zwischen Schleifschnecke und Werkstück beim Wälzschleifen. Während der Bearbeitung befinden sich immer mehrere Zahnflanken gleichzeitig im Eingriff mit der Schleifschnecke. Dies erschwert unter anderem eine Übertragung vorhandener Erkenntnisse aus anderen, besser erforschten Schleifprozessen (z. B. dem diskontinuierlichen Profilschleifen). Die veränderlichen Kontaktbedingungen führen zu einer ausgeprägten Dynamik im Prozess, die eine Herausforderung sowohl für die Maschinenentwicklung, die Regelungstechnik als auch für die Prozessauslegung darstellt. Die Kenntnis der zu erwartenden Bearbeitungskräfte und ihres zeitlichen Verlaufs ist daher notwendig, um die Dynamik des Prozesses einerseits beschreiben und andererseits optimieren zu können. Hierzu müssen sowohl der Betrag als auch die Richtung der lokal auftretenden Zerspanungskräfte bekannt sein. Allerdings ist die Bestimmung der auftretenden Zerspanungskräfte im Wälzschleifprozess nur mit großem Aufwand möglich. Bisher existieren keine systematischen Untersuchungen zum Einfluss der Maschineneinstellparameter auf die Zerspanungskräfte im Wälzschleifprozess.
      PubDate: 2013-09-25
  • Näherungsverfahren zur Berechnung von Kerbspannungen und -dehnungen
           bei Plastizität und Kriechen
    • Abstract: Zusammenfassung Diese Arbeit stellt vier Näherungsverfahren zur Abschätzung der Spannungskonzentration an Kerben vor. Es handelt sich um die Neuber-Regel, die Glinka-Methode, die Interpolationsmethode und eine neu entwickelte, numerische Neuber-Regel. Dabei werden Kriechen und Plastizität bei proportionaler Belastung und konstanter Temperatur berücksichtigt. Außerdem wird ein Verfahren zur Berechnung der Hauptspannungen und -dehnungen im Kerbgrund beschrieben. Um diese Verfahren zu verifizieren, werden FEM-Berechnungen an einer gelochten Scheibe und einer Kerbprobe als Beispiele unter Zugbelastung durchgeführt. Zusätzlich werden die durchschnittlichen Abweichungen der Näherungsverfahren von den FEM-Werten ermittelt. Es wird damit gezeigt, dass alle vier Methoden die FEM-Werte mit hoher Genauigkeit approximieren.
      PubDate: 2013-09-24
  • Development of new models of performance correction factors of centrifugal
           pumps as a function of Reynolds number and specific speed
    • Abstract: Abstract The performance characteristics of a small centrifugal pump having a specific speed of 20 min−1 are measured when pumping two industrial Newtonian oils of viscosities 75 and 646 cSt, at value of Reynolds number near 103. The diminishing of the performance in the case of these oils compared to water is about 50 to 80 %. It decreases with the reduction of Reynolds number. The correction factors of head, of flow rate and efficiency, are determined depending on Reynolds number, and they are compared with those obtained using the European KSB empirical method, the American method ANSI/HI and the semi-empirical method based on the analysis of power losses. For centrifugal pumps of a specific speed below 50 min−1, the fall in performance increases with the decrease of Reynolds number and specific speed. The fall in efficiency is more important than the fall of the other performance parameters. A good agreement is obtained between experimental results and predicted results using the three above mentioned methods, with the exception of the efficiency correction factor obtained by the method of power losses analysis, in the range of Reynolds numbers between 103 and 105. The expression of correction performance factors based on the Reynolds number is universal. It allows to distinguish the ranges of correction factors falls, and to know the economic limitations of the use of centrifugal pumps. A fall of head and flow rate correction factors of over 10 % occurs at values of Reynolds number below 104. But, the fall of efficiency correction factor of over 10 % occurs at values of Reynolds number below 105. To facilitate to the professionals the calculation of the performance correction factors of centrifugal pumps, new models are proposed in this study according to Reynolds number and specific speed.
      PubDate: 2013-08-23
  • Analysis of coupled dissipative dynamic systems of engineering using
           extended Hamiltonian        id-i-eq1">        format-t-e-x">$\mathcal{H}$ for
           classical and nonconservative Hamiltonian        class="a-plus-plus">H        class="a-plus-plus">∗       class="a-plus-plus">n for higher
           order Lagrangian systems
    • Abstract: Abstract Lagrange and Hamilton formalisms derived from variational calculus can be applied nearly in all engineering sciences. In this study, the reader is introduced using tensorial variables in covariant and contravariant forms, to the extended Lagrangian $\mathcal{L}$ and herewith to the modified momentum ${p}_{{k}}^{*}$ . Through both, the extended Hamiltonian $\mathcal{H}$ of a dissipative engineering system is derived to analyze the engineering system in an analytical way. In addition, a nonconservative Hamiltonian H ∗n for systems with elements of higher order is introduced in a similar manner. Moreover, different forms of extended Hamiltonian are represented. How these forms are achieved and how to derive the equations of generalized motion in different forms is also explained. As an example, a coupled electromechanical system in different formulations is given on behalf of the reader. The example is even extended to a case including some elements of higher order.
      PubDate: 2013-01-01
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