Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The mechanical properties of oils are determined using test methods. There are standardized test methods for determining viscosity and density. The characterization of transmission oil based on its dynamic viscosity alone is not sufficient for the physical explanation of different levels of noise emissions in vehicle transmissions. For this reason, the test procedure for determining the coefficient of friction is used in the following to enable a further differentiation between the oils according to mechanical properties. In gear transmissions with involute gear teeth, rolling friction occurs in the gear pair meshing along the line of action due to the variation in the equivalent curvature radii throughout the meshing cycle. This is rolling friction on which a sliding friction component, so-called slip, is superimposed. Pure rolling friction only occurs in the pitch point. From the pitch point to the start and end of the meshing, there is a superimposed sliding friction component that increases with increasing distance from the pitch point. Slip values occur in the range of 5–50% depending on tooth geometry. These friction conditions during tooth flank lubrication can be assessed using the Stribeck curve. The Stribeck curve represents the coefficient of friction as a function of the speed. A mini traction machine from PCS Instruments with a ball/plate measurement setup was used to determine the coefficient of friction behavior of gear oils. This allows the coefficient of friction of an oil to be assessed at low speeds in the range from boundary and mixed friction to elastohydrodynamic fluid friction at high speeds. The investigations show that the coefficient of friction behavior of a gear oil depends on the oil viscosity and above all on the chemical composition. The lower the coefficient of friction, the less energy is required to shear the lubricating film and the lower the power transmission through the fluid. The coefficient of friction is a property that is dominated by the type of base oil and the type of VI improver in the area of mixed and fluid friction, especially with additional sliding in contact. It will be shown in the paper that the use of a gear oil that has been optimized with regard to the coefficient of friction curve can reduce the entry impacts of meshing gear pairs under vibration excitation and the gear transmission thus generates lower noise emissions. PubDate: 2022-06-22
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The helicoid of the planar enveloping toroidal worm has a complex geometry. This paper is devoted to revealing the geometric characteristics of the helicoid in depth. We strictly demonstrate the developability of the helicoid from the perspective of curvature characteristics, and further clarify that the helicoid is a tangent surface as a developable surface and its directrix is the curvature interference limit curve of the worm. We also derive a vector equation for the profile in section of the helicoid, which has a simple form with single-parameter and can reveal the precise geometry and characteristics of the profile. The profile in cross-section proves to be an involute, and the base circle radius rb* of involute profile at different cross-sections are the same, while the starting rotation angles θ0 are different. The curved profile in axial-section is generally approximate to a straight line in accordance with the curvature function derived from vector equation. From the engaging-in region to the engaging-out region, or as the inclination angle of the grinding wheel β and radius of main basic circle rb increase, the profile in axial-section becomes straighter. This work gives insight into essential attributes of the helicoid, and lays a theoretical foundation for the inspection and tolerance standard establishment of the worm and worm wheel hob. PubDate: 2022-06-10
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract In this paper, a nonlinear dynamics equation for a micro electromagnetic harmonic drive system is proposed considering nonlinearity caused by the molecule force applied to the flexible ring. Using the equations, the nonlinear resonant frequencies and the amplitude frequency characteristics of the drive system are investigated. Effects of the molecule force nonlinearity on the resonant frequencies and the amplitude-frequency characteristics and their changes along with system parameters are analyzed. Results show that the nonlinear effect of van der Waals forces on system vibration should be considered when the coil current and the radius of the flexible wheel are large, the thickness of the flexible wheel or the gap between the flexible wheel and the stator is small. The jump vibration zone of the flexible wheel reduces significantly with increasing the exciting current in the coil, the length of the flexible wheel, and the nonlinear parameter, or decreasing the thickness of the flexible wheel. PubDate: 2022-06-02
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract One of the central goals during the design of helical gear systems is the achievement of a well-distributed contact load in the gear mesh. An equal load distribution is a key factor for a high load carrying capacity, the economic use of materials and a long lifetime. Mesh misalignment can be caused by tooth deflections, manufacturing deviations or elastic deformation of the shaft-bearing system and the gearbox housing. Those deformations have to be taken into account during the design process of adequate tooth-flank geometry. Elastic deformations of gearbox housings can be significant, especially in the case of automotive applications with aluminium cases. This paper presents an advanced method of including housing stiffness into the calculation of gear systems. A validation of the approach is carried out by comparing the calculated deformations with measurements of a static test rig of a hypoid gearbox. Many calculation programs offer the opportunity to analyse the deformation behaviour of the shaft-bearing-housing system. Most of the components in these programs are described by analytic approaches. However, components that are geometrically more complex, like the housing or planet carriers cannot be represented as easily as that by analytic expressions. There are several alternatives to take into account the elasticity of those objects. One way is to model the stiffness of the bores using imported stiffness matrices. These matrices contain the elasticity of the bores itself as well as crossover influences between the bearings. The reduced stiffness matrices may be the result of a static reduction of the geometry using the finite element method (FEM). As state of the art, the reduction is mostly carried out at the centre points of the bearing bores. The proposed advanced method uses the static reduction of geometries on several points at the bores, distributed over the circumference. This approach offers a more detailed modelling of the elastic behaviour of complex geometries within the analytic deformation calculation of gear systems. To validate the advanced approach, the calculation results of the elastic deflections of the shaft-bearing-housing system is compared with measurements of a static test rig. In the course of these comparisons, the influence of different modelling methods of gearbox housings on the accuracy of the calculation results is discussed. PubDate: 2022-05-19
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The excessively high temperature of gearbox oil in summer leads to power reduction of wind turbines (called high-temperature power reduction state), which does harm to the performance of the power generation performance of the wind turbine. The timely and accurate identification of high-temperature power reduction state will contribute to improving the operation efficiency of the unit. This study proposes a new method based on the vine copula model and algorithm of convolutional neural network cascading to the bidirectional long short term memory network with attention mechanism (CNN-BiLSTM-attention). Firstly, the vine copula model is used to analyze the correlation of the features in supervisory control and data acquisition (SCADA) system, and the features that can reflect the high-temperature power reduction state are extracted comprehensively. Secondly, CNN is used to mine the coupling relationship between features and extract deep spatial features. Finally, BiLSTM is used to extract the time-series information in the depth spatial feature further for high-temperature power reduction state identification, and the attention mechanism is introduced to sense and identify the relevant network weights adaptively to enhance the influence of important information. The experimental results show that the method has high identification accuracy in the identification of high-temperature power reduction state. Accurate and reliable identification results can provide reference for formulating the operation and maintenance scheme of wind turbine reasonably. PubDate: 2022-05-19
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Zusammenfassung Das Arbeitsmittel in Wärmepumpen unterliegt einer Vielzahl von Anforderungen, welche für einen effizienten und sicheren Betrieb eingehalten werden müssen. Weiterhin steigt die Anzahl markterhältlicher Arbeitsmittel durch die Entwicklung neuer Gemische kontinuierlich an, wodurch deren Auswahl erschwert wird. Aus diesem Grund wird im Rahmen dieses Beitrags eine Marktanalyse alternativer Arbeitsmittel durchgeführt und die selektierten Arbeitsmittel hinsichtlich ihres Potentials für Wärmepumpen bewertet. Die Marktanalyse beinhaltet eine Einordnung der Arbeitsmittel durch politische Vorgaben (kein Ozonabbaupotential, geringes Treibhauspotential), sicherheitstechnischer Aspekte (Toxizität, Brennbarkeit) sowie technischer Anforderungen (unterkritischer Betrieb, maximale Prozesstemperaturen). Hierbei werden 32 Fluide identifiziert, welche die gestellten Anforderungen einhalten. Diese sind alle brennbar und größtenteils entweder Kohlenwasserstoffe (KW) oder Hydrofluorolefine (HFO). Anschließend wird die Effizienz im einfachen Kältekreislauf nach DIN EN 14825 bestimmt. Um die Fluidabhhängigkeit detailliert und realitätsnah abschätzen zu können, wird ein semi-physikalisches Verdichtermodell eingesetzt, welches fluid- und betriebspunktabhängige Verdichterwirkungsgrade liefert. Innerhalb der Kreislaufberechnung zeigen die Fluide RC270 und R161 die höchsten Effizienzen und führen zu einer Verbesserung der saisonalen Arbeitszahl im Vergleich zu R410A von bis zu 15 %. Diese führen aber zu hohen Temperaturen am Verdichteraustritt und sind daher ungeeignet. Weiterhin zeigen KW höhere Effizienzen als HFO. Bei der Wahl des Arbeitsmittels müssen allerdings weitere Aspekte, wie der Umwelteinfluss sowie Füllmengenbeschränkungen aufgrund der Brennbarkeit des Fluids betrachtet werden. Insgesamt weisen die Arbeitsmittel Propan und Propen das höchste Anwendungspotential auf. Für Anwendungen, in denen füllmengenbeschränkte Wärmepumpen erforderlich sind, bieten die HFO R454C, R457A und R516A effiziente Alternativen, deren Potenzial durch die Integration eines internen Wärmeübertragers in den Kältekreislauf gesteigert werden kann. PubDate: 2022-05-19
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Due to the rapidly increasing price of tungsten carbide and the significant health risks associated with the wear products of WC-Co (Co3O4 and Wo3), an alternative is required. Niobium carbide (NbC) is well suited as a cutting tool due to its high melting point and low solubility in iron. Compared to pure NbC, a complete substitution of WC to NbC-Co resulted in an increased toughness and strength. As alternative binders, nickel and iron-based binders were subsequently investigated. Although iron-based cermets would be an economical, low-cost alternative to NbC-Ni cermets, they showed a higher coefficient of friction and wear rate. So far, NbC-Ni cermets best met the requirements of high hardness and toughness. Various secondary carbides such as VC, Mo2C, TiC, but also WC were added to further improve the hardness. Elemental analyses of NbC-Ni-MeC cermets (Me = metal) showed that the binder is a face-centered cubic solid solution, while the NbC phase is a solid solution of the type (Nb, Me)C. PubDate: 2022-04-27
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The reduction of torsional vibrations of drivetrains of machines and plants is of considerable interest in various fields of engineering, as they can have a negative influence not only on the drivetrain itself, but also on the driven machinery. Hence, a variety of countermeasures were developed to minimize such vibrations. In the present contribution, the possibilities of reducing torsional vibrations of drivetrains by introducing impulsive torques are investigated. The impulsive strength is chosen in a way that fully elastic impacts of a point mass with a rigid wall are mimicked, i.e., energy is neither fed to nor extracted from the mechanical system by the impulses. It is shown that therewith a transfer of vibration energy to higher modes is possible, where it is dissipated more effectively utilizing the enhanced damping capabilities of higher modes. A modal damping amplification factor is introduced allowing to characterize the energy transfer based on a mapping of the state-vector from one instant of time where an impulse is applied, to the next. It is demonstrated with a numerical example that the damping amplification factor allows to analyze modal energy transfer effects in mechanical systems exhibited to impulsive torques in an efficient manner. PubDate: 2022-03-31 DOI: 10.1007/s10010-022-00582-2
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Zusammenfassung Zur Übertragung von Drehmoment und Drehzahl in beliebiger Achsanordnung eignen sich bei kleinem Achswinkel bis 30° Beveloidverzahnungen. Besonders die windschiefe Achslage bietet dabei Potenzial, Bauraum und Gewicht aufgrund eines möglichst direkten Leistungsfluss zu realisieren. Beveloidradpaarungen in nicht paralleler Achslage haben jedoch den Nachteil, dass aufgrund der geneigten Grundzylinder nur ein punktförmiger Kontakt vorliegt. Der auftretende Ease-Off kann ausschließlich durch komplexe Zahnflankenmodifikationen kompensiert werden, um so das Übertragungsverhalten zu verbessern. Zum Überprüfen der Wirksamkeit solcher Modifikation sind simulative Zahnkontaktanalysen unumgänglich. Zusätzlich sind Abwälzversuche erforderlich, um die simulativen Ergebnisse abzusichern. Durch Beveloidverzahnungen mit lokal angepassten Verzahnungsdaten entlang der Zahnbreite kann ein konjugierter Eingriff angenähert werden, was ein voll ausgebildetes Tragbild mit geringem Drehfehler in Kontaktsimulationen zeigt. In diesem Bericht sollen die vielversprechenden Ergebnisse der Kontaktsimulationen in Abwälzversuchen validiert werden. Zunächst wird mithilfe des Versuchskonzepts das Vorgehen definiert, um die Prüfstandsversuche durchzuführen und die erzielten Ergebnisse am Prüfstand mit den Simulationsergebnissen abzugleichen. Die exemplarisch ausgelegte Prüfverzahnung wird mittels Fünf-Achs-Fräsen gefertigt und kann mit drei Mikrogeometrien am Umfang verteilt ausgeführt werden. Zwei Ansätze zur Definition der Mikrogeometrien werden vorgestellt, mit denen ausgehend vom konjugierten Eingriff eine gezielte Positionierung und Skalierung des Tragbilds möglich ist. Die tatsächliche Zahnflankengeometrie wird topografisch vermessen und kann in Kontaktsimulationen untersucht werden. Der Vergleich zwischen diesen Simulationsergebnissen und den am Prüfstand ermittelten Ergebnissen zeigt beim Tragbild und lastfreien Drehfehlerverlauf eine hohe Übereinstimmung. Der Vergleich zwischen den Prüfstands- und Simulationsergebnissen validiert die analytische Berechnungsmethode zur Auslegung und Optimierung von Beveloidverzahnungen mit lokal angepassten Verzahnungsdaten entlang der Zahnbreite. PubDate: 2022-03-16 DOI: 10.1007/s10010-022-00581-3
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Zusammenfassung Mit Hilfe der erweiterten Hillschen Gleichungen für Ellipsenbahnen mit kleiner Exzentrizität wird eine Methode zur Bahnkorrektur von Satelliten angegeben. Zu einem vorgegebenen Parameter, der Transferzeit, werden die erforderlichen beiden Geschwindigkeitskorrekturen für ein Zwei-Impuls-Manöver ermittelt. Außerdem werden die Einschränkungen für mögliche Transferzeiten angegeben. Es wird ferner gezeigt wie der optimale Parameter für einen minimalen Geschwindigkeitsbedarf zur Treibstoffoptimierung bestimmt werden kann. Die Zielfunktion dieser Optimierung hängt dabei nur von einer Variablen, nämlich der Transferzeit ab. Daher kann das Minimum mit einem Optimierungsverfahren oder noch einfacher mit dem Newton-Verfahren numerisch leicht bestimmt werden. Die angegebene Methode lässt sich auch auf verwandte Probleme der Bahnmechanik anwenden. PubDate: 2022-03-03 DOI: 10.1007/s10010-022-00578-y
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract User-centered design focuses on the individual needs of the product users. The aim is to adjust the design of the product according to the requirements of the user and application. Existing methods for evaluation of the perceived usability are often limited to one specific aspect, and it requires a high effort to transfer the respective method to other aspects. A generic process for the evaluation of the perceived usability is missing. This paper presents the generic Usability Study Evaluation Process (USE-Process) that helps product designers to identify and evaluate usability aspects relevant to the suitability of the usage of a product. The process is divided into three sections: 1. A structured field study to identify the relevant usability aspects; 2. A generic study design for the subjective evaluation of usability aspects under objective and reproducible conditions; 3. The use of measurement tools that help to quantify the results of the subjective evaluation. The generic applicability of the process is shown by the example of the evaluation of cordless screwdrivers; several usability aspects were identified, clustered, and evaluated by using subjective evaluation methods and measurement techniques. PubDate: 2022-03-01 DOI: 10.1007/s10010-021-00546-y
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Inspection activities in automotive manufacturing play a crucial role in diagnosing and preventing unexpected failures by adopting the well-planned intervals. However, finding the optimal inspection intervals has been a major concern within manufacturing systems due to the failure dependency issue caused by the design complexity and integrated operations. Hence, this paper proposes a new framework for inspection interval optimization under failure dependency in three steps; firstly identifying all failure modes and potential dependent failures through Failure Mode and Effect Analysis (FMEA) method, secondly, adapting the statistical based approach for reliability and availability evaluation, as well as using the Bayesian theory for availability and total expected cost based inspection modeling under failure dependency and finally, performing some well-known Multi-Criteria Decision-Making (MCDM) techniques for finding the optimal trade-off between main criteria e.g. total expected cost and reliability indices. The results of the proposed framework revealed that the failure dependency has a meaningful impact on inspection intervals. Besides, the cost-based model suggests shorter inspection intervals with that of the availability-based model in all dependent failure cases. As a consequence, the results could be useful for implementing the reliable maintenance programs to improve the operational performance of complex equipment in automotive manufacturing. PubDate: 2022-03-01 DOI: 10.1007/s10010-021-00568-6
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Zusammenfassung Anschmierungen innerhalb von Wälzlagern zählen zu den Verschleißarten, die bis heute nicht vollständig verstanden wurden. Bekannt ist, dass mangelhafte oder ungünstige Schmierung sowie hoher Schlupf zum Schmierfilmzusammenbruch und zu anschließender Zerstörung der schützenden Grenzschichten führen. Hierbei entstehen plastische Deformationen, Materialübertragungen sowie thermische Gefügeänderungen. Hohe Massenträgheiten der Wälzkörper begünstigen Anschmierungen. Daüber hinaus besitzen der Schmierstoff, die Kontaktzeit, welche ein Punkt der Oberfläche benötigt um den Kontakt zu durchlaufen, sowie Schiefstellungen der Wälzkörper wesentlichen Einfluss. Es werden die vorhandenen Anschmierkriterien vorgestellt, welche allerdings nur für spezielle Betriebsbedingungen gelten und darüber hinaus für jede Werkstoff-Schmierstoff-Paarung neu zu ermitteln sind. Als Abhilfemaßnahmen in sonst nicht veränderbaren Systemen zeigen Beschichtungen, Verringerung des Betriebsspiels sowie ein Einlauf hohes Potential zur Verhinderung von Anschmierungen. Anhand der Fresstragfähigkeit von Zahnrädern, welche über einen Abgleich experimentell mit simulativ ermittelten Kontakttemperaturen erfolgt, wird gezeigt, wie eine mögliche Auslegungsrichtlinie für Anschmierungen aussehen könnte. Erhebliches Potential für die Zukunft wird darüber hinaus bei gezielten Untersuchungen von Schiefstellungen in Modellprüfständen und der Betrachtung des Kinematikverhaltens kombiniert belasteter Zylinderrollenlager gesehen. PubDate: 2022-03-01 DOI: 10.1007/s10010-021-00490-x
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Zusammenfassung Eine der zentralen Problemstellungen beim bedingt- und hochautomatisierten Fahren liegt in der Gestaltung einer sicheren und komfortablen Aufgabenübertragung zwischen dem automatisierten System und dem menschlichen Fahrer und vice versa. Dieser Beitrag stellt ein holistisches Modell zur Übergabe und Übernahme von Fahraufgaben vor, welches über eine umfassende Fahrerbeobachtung anhand von verschiedenen Sensoren und Referenzsensoren eine an den Fahrerzustand angepasste Übernahme ermöglichen soll. Konfliktsituationen zwischen Fahrer und automatisiertem System sollen unter Berücksichtigung des Fahrer- und Systemzustands über einen technisch implementierten Koordinator detektiert und gelöst werden. In einem Wizard-of-Oz Fahrversuch wird die Veränderung des sensorischen, motorischen und emotionalen Fahrerzustands, welche zentrale Komponenten des Übergabemodells bilden, anhand von zwei Fahrszenarien in Übernahmesituationen detailliert analysiert. Beobachtet werden konnten dabei leicht langsamere Reaktionen der Probanden nach Nebentätigkeiten und eine deutlich steigendes Stresslevel nach Übernahmen. PubDate: 2022-03-01 DOI: 10.1007/s10010-021-00547-x
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Zusammenfassung Es werden Ergebnisse aus einer Kontaktsimulation vorgestellt, welche die Oberflächenveränderung eines Axiallagers infolge von unerwünschtem elektrischem Stromdurchgang bei Mischreibung zeigen. Das hierzu entwickelte Modell berücksichtigt neben den Oberflächenrauheiten auch das nichtlineare Materialverhalten des Wälzlagerwerkstoffes. Im Gegensatz zu bekannten Modellierungsmethoden für ähnliche Problemstellungen, wird hier ein neuartiger Ansatz auf Basis einer gekoppelten Euler- Lagrange- Finite Element Simulation entwickelt. Das Modell liefert, mit experimentell geschädigten Oberflächen als Eingangsgröße, Erkenntnisse zum Traganteilsverhalten und weiterer mechanischer Kenngrößen infolge kombinierter mechanischer und elektrischer Belastungen. PubDate: 2022-02-25 DOI: 10.1007/s10010-022-00579-x
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Thrust collars relieve the gearbox housing of the axial force and tilting moments generated by helical gears. The different transfer path also reduces the vibration excitation of the housing due to meshing, which could lead to improved acoustics. This paper presents measurements of noise level reduction of an experimental gearbox. A gearbox dynamics simulation model is used to investigate the effects resulting from the inclusion of thrust collars. PubDate: 2022-02-18 DOI: 10.1007/s10010-022-00580-4
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract In automated vehicles, the collaboration of human drivers and automated systems plays a decisive role in road safety, driver comfort, and acceptance of automated vehicles. A successful interaction requires a precise interpretation and investigation of all influencing factors such as driver state, system state, and surroundings (e.g., traffic, weather). This contribution discusses the detailed structure of the driver-vehicle interaction, which takes into account the driving situation and the driver state to improve driver performance. The interaction rules are derived from a controller that is fed by the driver state within a loop. The regulation of the driver state continues until the target state is reached or the criticality of the situation is resolved. In addition, a driver model is proposed that represents the driver’s decision-making process during the interaction between driver and vehicle and during the transition of driving tasks. The model includes the sensory perception process, decision-making, and motor response. The decision-making process during the interaction deals with the cognitive and emotional states of the driver. Based on the proposed driver-vehicle interaction loop and the driver model, an experiment with 38 participants is performed in a driving simulator to investigate (1) if both emotional and cognitive states become active during the decision-making process and (2) what the temporal sequence of the processes is. Finally, the evidence gathered from the experiment is analyzed. The results are consistent with the suggested driver model in terms of the cognitive and emotional state of the driver during the mode change from automated system to the human driver. PubDate: 2022-01-24 DOI: 10.1007/s10010-021-00576-6
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract High contact ratio gears are used to minimize the stresses generated on the tooth surface. This research article represents an idea to enrich the contact strength of gear drive using novel high contact ratio (NHCR) spur gear. The increase in contact stress leads to contact fatigue failure, reducing the power transmission capacity of the gear drive. To reduce contact fatigue failure, contact stress needs to be reduced. A high contact ratio spur gear is developed using the novel hob cutter with variable tooth thickness to minimize the contact stress. For a novel hob cutter, the tooth thickness coefficient is greater than 0.5, while the thickness factor of a conventional hob cutter is 0.5. The maximum contact stress is determined through finite element analysis. In addition, a parametric study is executed for the gear parameter such as gear ratio, gear teeth, pressure angle, addendum factor and addendum correction factor to determine optimum contact stress. PubDate: 2022-01-22 DOI: 10.1007/s10010-022-00577-z
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Zusammenfassung Um die Unfallzahlen weiter zu senken, schreibt die Europäische Union ab 2030 eine höhere Fahrerüberwachung für neue Fahrzeuge vor. Bislang liegt der Fokus in einem manuell gefahrenen Fahrzeug auf einer Müdigkeitserkennung als Komfortsystem. Jedoch ändern sich die Anforderungen an den Fahrer und dessen Aufgaben bei steigender Automatisierung der Fahraufgabe, sodass auch die Fahrerbeobachtung/-überwachung weiter entwickelt werden sollte. Die vorliegende Arbeit beschäftigt sich mit der Auslegung von Aufmerksamkeitsaufgaben in Simulator-Fahrversuchen und einem ersten Versuch die aufgenommenen Daten von wenigen Probanden automatisch auszuwerten, um die Machbarkeit zu zeigen. Durch die partielle Automatisierung (nach SAE Level 2) der Fahraufgabe bleiben dem Fahrer bei der hier vorgestellten längeren Aufmerksamkeitsaufgabe nur noch schwache und seltene Reize, sodass von einer Vigilanzaufgabe gesprochen werden kann. Zur Messung des Fahrerzustands wird in dieser Machbarkeitsstudie eine Kombination aus verschieden Körperfunktionen durch unterschiedliche Sensoren erfasst, mit einem künstlichen neuronalen Netzwerk fusioniert und verarbeitet. Es werden verschiedene Kombinationen von Sensoren getestet, um herauszufinden, welche Signale für eine Klassifikation des Fahrerzustands ausreichend oder notwendig sind. Dabei wird darauf geachtet, ob diese Signale in Zukunft durch neue Sensortechnologien auch kontaktlos erfasst werden könnten, um eine Entwicklung dieser zu motivieren. Am Ende wird eine Klassifizierung vorgenommen, die zwischen den hier so genannten Zuständen Vigilant (aufmerksam) und Hypovigilant (nicht mehr aufmerksam) unterscheiden kann, sodass eine anschließende Regelung ein solches Signal verwenden kann, um den Fahrer in einen besseren Zustand zu bringen. Zudem kann der Fahrer gewarnt werden, wenn die Aufmerksamkeit nicht zu den Aufgaben passt, die er in der Automatisierungsstufe zu erledigen hat beziehungsweise für die er verantwortlich ist. Dazu könnten Aufgaben zwischen dem Fahrzeug und dem Fahrer dynamisch verteilt werden, also beispielsweise die Führung in Längs- oder Querrichtung wieder als Fahraufgabe dem Fahrer übergeben werden, um ihn aufmerksam zu halten. Durch eine kontaktlose Erfassung der Aufmerksamkeit gibt es zudem einen Komfortgewinn, da zum Beispiel die Hände nicht mehr das Lenkrad festhalten müssen, um dem Fahrzeug seine Aufmerksamkeit zu bestätigen, wie es heute in einigen Fahrzeugen üblich ist. PubDate: 2021-12-20 DOI: 10.1007/s10010-021-00572-w
Please help us test our new pre-print finding feature by giving the pre-print link a rating. A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The drivetrain as an important part of wind turbines needs to be improved in order to deal with today’s high development and cost pressure. One important step towards enhanced drivetrains is to identify the most suitable concept for a targeted onshore application in an early design stage. With this purpose, a holistic lifecycle system evaluation approach relying on minimum input information is presented. In order to identify a dominant solution, an additive target system is defined taking cost, ecological sustainability, and supplied energy into account. This multi-criteria decision is aggregated by defining a macrosocial evaluation criterion: “drivetrain specific energy supply effort”. A physics- and empirically-based model is developed to quantify the targets for different onshore drivetrain concepts. The validity of the model results is shown by a comparison to meta-analysis findings. Being utilized on a drivetrain concept comparison between geared and direct drive the approach’s value is showcased. Both concepts score on a comparable level slightly differing in weak and strong wind regimes. An exemplary trade-off between investment- and operational effort shows, that for both concepts the investment effort is higher than the operational. The comparison furthermore shows how robust decision support can be provided by parameter variation and finally it stresses, that the decision maker’s preferences need to be incorporated in the decision. Concluding, this analysis shows that physics- and empirically-based model approaches enable holistic wind turbine drivetrain concept comparisons in an early design stage. PubDate: 2021-12-07 DOI: 10.1007/s10010-021-00564-w
Hybrid journal (It can contain Open Access articles)
[2469 journals]
