ORCID Profile
0000-0003-0168-9690
Current Organisations
University of New England
,
University of Queensland
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Publisher: Publicações do Cidehus
Date: 2008
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 2017
Publisher: Springer Science and Business Media LLC
Date: 14-03-2015
Publisher: Oxford University Press (OUP)
Date: 12-2022
DOI: 10.1093/JCDE/QWAC126
Abstract: Numerical analyses of the roller–raceway contact have been carried out in a spherical roller bearing using frictional contact models of different complexity. The models used in the study include an implementation of Kalker’s exact contact theory named CECT (Conformal Exact Contact Theory) and detailed Finite Element models. The adequacy of the more simplified contact solutions is assessed by contrasting them with the solutions obtained with the more comprehensive models. Additionally, the use of the exact contact theory, well known in the wheel–rail application, is demonstrated in contact mechanics analyses in rolling bearings, describing relevant details of its implementation for this application. Situations with different normal loads and friction levels have been analysed, and two distinct steady equilibrium configurations of the roller have been identified.
Publisher: Elsevier BV
Date: 2017
Publisher: Editorial CSIC
Date: 30-12-2014
Publisher: Elsevier BV
Date: 09-2004
Publisher: SAGE Publications
Date: 09-2013
Abstract: In order to validate prediction models of wheel squeal, a rolling contact test rig is used to investigate fundamental squeal behaviour. The vibration characteristics of the wheel are investigated using analytical and finite element methods, and by experimental impact hammer analysis, respectively. Accordingly, the lateral resonant frequencies and mode shapes of the wheel are determined. A dominant mode is identified based on this as the primary peak in the sound spectrum of squeal and is used as an indicator of the occurrence and magnitude of squeal. The lateral creep curves and litudes of wheel vibration at various rolling speeds are measured using a strain gauge technique and predicted. A simplified model including the interaction between lateral force and transverse vibration of the dominant mode is developed, and the experimental and simulated results show the sound pressure level and vibration velocity of the wheel increases substantially as the angle of attack reaches and exceeds the value around 8 mrad. The phenomenon of double peaks in the sound spectrum of wheel squeal is also investigated. It is found that the cause of double peaks is due to the wheel rotation and the frequency ergence of double peaks increases with rolling speed as predicted theoretically.
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 03-2019
Publisher: BRILL
Date: 27-08-2012
Publisher: Brill
Date: 23-01-2023
DOI: 10.1163/2208522X-02010182
Abstract: The History of Emotions has been establishing itself as a field of historical research since the 1980s, but, to date, almost no attempt has been made to approach the study of the Spanish and Portuguese inquisitions through the history of emotions. Focusing on the period 1560–1610, which followed the conclusion of the Council of Trent, this essay endeavours to offer a preliminary analysis of Iberian inquisitorial trials for the history of emotions. The first section examines the case study offered by the trial of the Spanish soldier Bartolomé Domínguez, who was prosecuted in Portugal for committing sacrilege in 1589. Having lost all his money gambling, Bartolomé drew his sword and slashed at a wayside cross. This public act of sacrilege led to Bartolomé’s arrest and an investigation by the Inquisition. The surviving inquisitorial trial dossier provides an interesting insight into the role played by emotions in inquisitorial justice and social disciplining in the early modern Iberian Peninsula. The second section examines a limited s le of trials that have been edited and seeks to find references to tears and weeping in such sources. It discusses what such references reveal about the attitudes of inquisitors towards tears within the legal context of inquisitorial trials, and whether tears were always seen as evidence of genuine contrition. The third and final section focuses on investigating how the context of post-Tridentine spirituality might have played a role in the increased attention that the inquisitors paid to other physical signs of contrition beyond tears.
Publisher: Elsevier BV
Date: 03-2015
Publisher: Trans Tech Publications, Ltd.
Date: 12-2016
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.725.586
Abstract: Two-point incremental sheet forming process (TPIF) is an emerging and promising manufacturing process for the production of complex geometries or customized functional sheet components. In this study, the single-pass TPIF process is investigated using experimental and numerical approaches to study the forming force evolution, fracture behavior and strain states with a varied wall angle hemisphere shape. It can be concluded that both the peak force and fracture depth increases with tool diameter and incremental depth in TPIF process. It seems the deformation mechanism or the failure mechanism is strongly dependent on particular forming conditions based on a failure parts morphology observation. FEM simulation results indicated that the major plastic strain is positive while the minor plastic strain is negative in the TPIF process on a hemiphere shape. it can be concluded that the strain increment and total equivalent plastic strain is affected by both tool diameter and incremental depth.
Publisher: Informa UK Limited
Date: 09-2006
Publisher: ASA
Date: 2013
DOI: 10.1121/1.4793582
Publisher: Elsevier BV
Date: 03-2008
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 03-2011
Publisher: Elsevier BV
Date: 09-2022
Publisher: Springer Science and Business Media LLC
Date: 17-11-2016
Publisher: Trans Tech Publications, Ltd.
Date: 03-2009
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.410-411.643
Abstract: This paper presents a model for prediction of forming roll profile wear during the cold roll forming process. The method is based on contact pressure distribution, geometrical description of the initial forming roll profile and NURBS representation of the contact area.
Publisher: Springer Science and Business Media LLC
Date: 11-07-2015
Publisher: Elsevier BV
Date: 11-2023
Publisher: Informa UK Limited
Date: 17-04-2013
Publisher: Elsevier BV
Date: 2018
Publisher: Elsevier BV
Date: 03-2023
Publisher: Springer Science and Business Media LLC
Date: 09-03-2017
Publisher: Wiley
Date: 2018
Publisher: SAGE Publications
Date: 05-08-2016
Abstract: Locomotive traction control behaviour and its dynamic impacts on rails and vehicles have not been comprehensively investigated in respect to transient conditions. Such transient traction behaviour could be more significant than steady state behaviour in determining dynamic traction performance and track degradation (i.e. squat/corrugation formation, etc.). In order to study this effect, detailed numerical simulations are performed to investigate a locomotive’s dynamic response to a change in contact conditions. In particular, creep response, vibration of the locomotive, and dynamic normal and traction forces are determined using a developed full-scale dynamics model of a locomotive. The model includes a detailed representation of the AC motor dynamics, which has not been considered in previous works. The results show that the detailed model is capable of simulating the dynamic fluctuations in creep and traction forces that are not considered in simpler models. Such transient responses may cause damage to the track and vehicle components.
Publisher: Trans Tech Publications, Ltd.
Date: 09-2011
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.337.452
Abstract: Incremental Sheet Forming (ISF) is a promising sheet-metal-forming technology which is drawing more and more researchers’ attention due to its flexibility of manufacturing three-dimensional products at a relatively low cost for rapid prototyping and small-batch production. This paper is focused on the thickness distribution and the forming strategy analysis for two point incremental forming with a male die. The analyzed benchmark is half a torus which is generated by revolving a semi-circle. Such a part is hardly able to be formed by single point incremental forming because its slope varies from 0 degree to 90 degrees. In terms of the varying slope, the variant of sine’s law is derived to give an approximate prediction of the thickness distribution from an analytical perspective. In addition, a multi-stage forming strategy is proposed in order to form the part successfully. In particular, a keying operation is implemented carefully in order to avoid twist phenomenon and achieve good dimensional accuracy.
Publisher: Trans Tech Publications, Ltd.
Date: 12-2017
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.725.578
Abstract: Incremental Sheet Forming (ISF) is a promising rapid prototyping technology used to form complex three-dimensional shapes. For forming a part with severely sloped regions, design of multi-stage deformation passes (intermediate shapes or preforms) before the final part, is widely adopted as a desirable and practical way to control the material flow in order to obtain a more uniform thickness distribution and avoid forming failure. However, a problem sometimes encountered in multi-pass forming is wrinkling deformation between two adjacent deformation passes. This may lead to forming process instability and even fracture. The overall quality of the final part may also deteriorate even if the part is formed successfully. In this paper, the wrinkling phenomenon in multi-pass incremental sheet forming is investigated by means of finite element analysis (FEA) and experimental tests to analyse the wrinkling formation mechanism. This research gives an insight into the optimized design of deformation passes in order to eliminate the unwanted wrinkling deformation in multi-pass incremental forming process.
Publisher: Elsevier BV
Date: 2020
Publisher: ASME International
Date: 26-03-2002
DOI: 10.1115/1.1456457
Abstract: Models for the occurrence of the vibrational instability during rolling known as third octave chatter are presented and discussed. An analysis of rolling mill chatter was performed for the purpose of identifying characteristics of the vibrations and to determine any dependency on the rolling schedule. In particular, a stability criterion for the critical rolling speed is used to predict the maximum rolling speed without chatter instability on schedules from a 5 stand tandem mill rolling thin steel product. The results correlate well with measurements of critical speed occurring on the mill using a vibration monitor. This research provides significant insights into the chatter phenomena and has been used to investigate control methods for suppression of the instability.
Publisher: Elsevier BV
Date: 07-2017
Publisher: Informa UK Limited
Date: 02-09-2021
Publisher: Springer Science and Business Media LLC
Date: 11-2021
Publisher: Elsevier BV
Date: 12-2019
Publisher: Elsevier BV
Date: 03-2020
Publisher: Springer Science and Business Media LLC
Date: 2002
Publisher: Elsevier BV
Date: 05-2020
Publisher: Routledge
Date: 06-2021
Publisher: Springer Science and Business Media LLC
Date: 11-01-2021
Publisher: Elsevier BV
Date: 03-2005
Publisher: Springer Science and Business Media LLC
Date: 02-2020
Publisher: Elsevier BV
Date: 05-2017
Publisher: Routledge
Date: 16-09-2020
Publisher: Springer International Publishing
Date: 2018
Publisher: Springer Science and Business Media LLC
Date: 19-02-2014
Publisher: Brill
Date: 04-06-2014
DOI: 10.1163/15700658-12342416
Abstract: In 1505, King Manuel I of Portugal (1495-1521) ordered the public printing of a letter officially addressed to Pope Julius II. In the letter, the Portuguese King defended his role as a ch ion of Christendom and scourge of Islam in the Indian Ocean. The most remarkable claim made by Manuel in this letter was that he was directly involved in persuading the Catholic monarchs of Spain Isabel of Castile and Fernando of Aragón to put an end to the toleration of Islam in Castile in 1501. This article focuses on this claim and whether or not it can merely be dismissed as the rhetoric of bombastic propaganda. It analyzes Luso-Spanish relations between 1495 and 1505 and highlights documentary evidence proving that Manuel did indeed put pressure on his Spanish neighbors to abolish the toleration of Islam during the tortuous negotiations surrounding his marriage to the Spanish princess Maria in 1501. Beyond assessing the historical significance of the letter, this article highlights the intricate connections between Portuguese imperial geopolitics and Iberian dynastic politics during this crucial period in the history of both the Spanish and Portuguese monarchies.
Publisher: Elsevier BV
Date: 11-2023
Publisher: Editorial CSIC
Date: 12-01-2029
Publisher: IEEE
Date: 08-2011
Publisher: Informa UK Limited
Date: 12-12-2016
Publisher: Elsevier BV
Date: 08-2009
Publisher: Springer Science and Business Media LLC
Date: 09-05-2014
Publisher: Elsevier BV
Date: 05-2006
Publisher: Elsevier BV
Date: 10-2020
Publisher: Elsevier BV
Date: 07-2015
Publisher: Elsevier BV
Date: 09-2019
Publisher: UNED - Universidad Nacional de Educacion a Distancia
Date: 2010
DOI: 10.5944/ETFIII.23.2010.1663
Abstract: Actualmente existen muy pocos estudios acerca de la esclavitud musulmana en Portugal. Cuando se trata el comercio de los esclavos en la historia portuguesa, generalmente los trabajos se refieren al comercio de los esclavos africanos que los navegantes portugueses comenzaron traer de vuelta a Europa desde el año 1441 en adelante, a pesar de que desde el siglo XI existía una pobulación de esclavos musulmanes —los llamados mouros cativos—. En este artículo propongo estudiar, de la forma la más detallada posible, las características y dinámicas del comercio de los esclavos musulmanes en el reino cristiano de Portugal durante la Edad Media, tratando de responder a preguntas relevantes, como las de cuál era el origen y el papel económico de los esclavos musulmanes en el Portugal medieval, qué sabemos del comercio de los esclavos en aquel reino, o a la cuestión de si Portugal fue un país exportador o importador de esclavos.Whilst the presence of Muslim slaves in medieval Spain has attracted considerable scholarly attention from historians both inside and outside of the Iberian Peninsula, the same cannot be said of the history of Muslim slaves in the medieval Christian kingdom of Portugal. Most studies of slavery in Portugal focus on captives from sub-Saharan Africa brought back by Portuguese slavers to Europe from 1441 onwards even though Muslim slaves were present in Portugal from the eleventh century at the very least. We know next-to-nothing about these Muslim slaves. This article proposes to examine in as much detail as possible the characteristics and dynamics of the commerce of Muslim slaves in medieval Portugal. It addresses problematic questions regarding the origins and economic role of Muslim slaves in premodern Portugal, the nature of slave trading and whether Portugal was an importer or exporter of slaves.
Publisher: Acoustical Society of America (ASA)
Date: 10-2022
DOI: 10.1121/10.0015749
Abstract: This research investigates a singularity in a published analytical solution of brake squeal due to mode coupling. Brake squeal is an annoying tonal noise that results from the slowing of a vehicle with friction brakes. Recent research has identified an efficient analytical prediction for occurrence, growth, limit cycle litude and mitigation of brake squeal noise. The analytical solution predicts squeal accurately, except at a singularity associated with large non-proportional d ing and repeated roots. Physically this occurs at the exact transition to stiffness mode coupling, ie. complex roots (Δ = 0). By taking the limit of the eigenvalue expressions at Δ = 0, it is found that the analytical eigenvalues approach infinity. The singularity occurs because modal mass matrix goes to zero at Δ = 0. The eigenvalues at Δ = 0 can be approximated by averaging the eigenvalues that are located on both sides of the critical friction coefficient (the average of eigenvalues at μcrit-Δμ and μcrit+Δμ). The approximations are closest to the numerical solution when Δμ is at the critical points of the Im(λavg) vs Δμ plot. In summary, the analytical solution under non-proportional d ing is undefined at Δ = 0 because of the zero modal mass matrix. Moreover, the eigenvalues at the point where singularity occurs can be approximated by taking the average of the eigenvalues located on both sides of the critical friction coefficient. It is shown that reasonable approximations can be obtained at the critical points of the Im(λavg) vs Δμ plot.
Publisher: Wiley
Date: 05-11-2010
DOI: 10.1002/RNC.1661
Publisher: Elsevier BV
Date: 11-2016
Publisher: Informa UK Limited
Date: 05-2013
Publisher: Trans Tech Publications, Ltd.
Date: 05-2014
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.939.245
Abstract: Incremental sheet forming (ISF) is a new promising technology due to its flexibility and low-cost tooling properties compared with conventional forming processes. However, a common technical problem encountered in ISF is non-uniform thickness variation of formed parts, particularly excessive thinning on severely sloped regions, which may lead to the part fracture and limit the process formability. Design of multistage deformation paths (intermediate shapes or preforms) before the final part is a desirable and practical way to control the material flow in order to obtain more uniform thickness distribution and avoid forming failure. Based on the shear deformation and the strain compensation idea, an analytical model for designing multistage deformation paths and predicting the thickness strain distribution is proposed. The feasibility of the proposed model is validated by the finite element analysis (FEA) and experimental tests in terms of the comparison of prediction, simulation and experimental results on the thickness strain distribution and the process formability.
Publisher: Elsevier BV
Date: 12-2023
Publisher: Wiley
Date: 04-2011
DOI: 10.1087/20110205
Publisher: Elsevier BV
Date: 11-2012
Publisher: Informa UK Limited
Date: 11-09-2014
DOI: 10.1080/00918369.2014.944044
Abstract: This article analyzes the inquisitorial trial of Maria Duran, a Catalan novice in the Dominican convent of Nossa Senhora do Paraíso in Portugal. Maria Duran was arrested by the Inquisition in 1741 and, after a lengthy trial, condemned in 1744 to a public lashing and exile. She was suspected of having made a pact with the Devil and was accused by many female witnesses of possessing a "secret penis" that she had allegedly used in her amorous relations with fellow nuns and novices. Her voluminous trial dossier offers a rare and fascinating documentary insight into the often extreme reactions that female homosexuality provoked from both men and women in early modern Portugal. Using the evidence offered by the 18th-century trial of Maria Duran, this article highlights female bewilderment when faced with female-on-female sexual violence and the difficulty that men (in this case, churchmen) had coming to terms with the existence of female homosexuality. It also discusses the case in light of the acts/identity debate among historians of the history of sexuality.
Publisher: ASME International
Date: 19-02-2014
DOI: 10.1115/1.4026326
Abstract: Longwall mining is an underground coal mining method that is widely used. A shearer traverses the coal panel to cut coal that falls to a conveyor. Operation of the longwall can benefit from knowledge of the cutting forces at the coal/shearer interface, particularly in detecting pick failures and to determine when the shearer may be cutting outside of the coal seam. It is not possible to reliably measure the cutting forces directly. This paper develops a method to estimate the cutting forces from indirect measurements that are practical to make. The structure of the estimator is an extended Kalman filter with augmented states whose associated dynamics encode the character of the cutting forces. The methodology is demonstrated using a simulation of a longwall shearer and the results suggest this is a viable approach for estimating the cutting forces. The contributions of the paper are a formulation of the problem that includes: the development of a dynamic model of the longwall shearer that is suitable for forcing input estimation, the identification of practicable measurements that could be made for implementation and, by numerical simulation, verification of the efficacy of the approach. Inter alia, the paper illustrates the importance of considering the internal model principle of control theory when designing an augmented-state Kalman filter for input estimation.
Publisher: Elsevier BV
Date: 05-2011
Publisher: UNED - Universidad Nacional de Educacion a Distancia
Date: 2010
Publisher: Informa UK Limited
Date: 09-2008
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 05-2011
Publisher: Informa UK Limited
Date: 18-03-2015
Publisher: Informa UK Limited
Date: 05-2020
Publisher: Springer Science and Business Media LLC
Date: 28-01-2022
DOI: 10.1007/S11249-021-01557-0
Abstract: Four commercial greases with various thickeners and base oils were experimentally examined to compare their false brinelling wear resistance in a test rig simulating roller bearings during rail/sea transportation for the first time. Greases containing zinc dialkyl dithiophosphates (ZDDP) showed superior false brinelling reduction, evidenced by no visible wear mark in the raceways. The mechanism for false brinelling mitigation was shown to be from a ZDDP-induced tribofilm which decreases the friction and wear coefficient in the contact area. Surface chemical analysis showed that for grease lubricated fretting contacts, ZDDP-derived tribofilms can be generated in the presence of micro-sliding motions and energy dissipation at the contact interface at low frequency (i.e., 4–8 Hz), due to the mechanochemical reactions. For greases without ZDDP, false brinelling wear was reduced by 97% when using grease with a more abundant and less viscous oil, which bleeds readily from an open structured thickener. The results highlight the ability of ZDDP as an additive in grease to better protect roller bearings against false brinelling during rail/sea transportation.
Publisher: Elsevier BV
Date: 02-2014
Publisher: American Society of Civil Engineers
Date: 08-02-2022
Publisher: Elsevier BV
Date: 05-2012
Publisher: Elsevier BV
Date: 12-2022
Publisher: Trans Tech Publications, Ltd.
Date: 11-2014
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.773-774.137
Abstract: ncremental sheet forming (ISF) is a new promising technology due to its flexibility and low-cost tooling properties compared with conventional forming processes. However, it is only suitable for small-batch production because of its incremental feature inducing relative long forming time. Presently, widespread usage of the process is restricted by a lack of predictive understanding of the process due to its complexity. In this paper, the aspect of forming time is studied by investigating the effects of four distinctive process parameters (step over, feed rate, sheet thickness and tool diameter). An effective analysis tool, Taguchi method together with design of experiment (DOE) and analysis of variance (ANVOA) is utilized to study the effects of the four process parameters on forming time and further to optimize parameter combinations in order to minimize forming time. Using these techniques, experimental results show that the step over of spiral tool path is the most important process parameter affecting forming time followed by feed rate. Sheet thickness and tool diameter have little effect on forming time. The comparison between the prediction of optimized parameter combination and the confirmation test result has further demonstrated the effectiveness of the proposed method. It is worth noting that the results of this study will indicate a further direction on how to optimize process parameters to find a balance between forming efficiency (forming time) and forming quality (forming accuracy and surface roughness).
Publisher: Elsevier BV
Date: 10-2008
Publisher: Springer Science and Business Media LLC
Date: 11-2013
Publisher: Springer Science and Business Media LLC
Date: 23-04-2016
Publisher: Informa UK Limited
Date: 03-07-2014
Publisher: Springer Science and Business Media LLC
Date: 28-09-2023
Publisher: Elsevier BV
Date: 03-2006
Publisher: Elsevier BV
Date: 03-2006
Publisher: Informa UK Limited
Date: 15-12-2015
Publisher: Indiana University Press
Date: 2021
Publisher: Elsevier BV
Date: 06-2014
Publisher: Editorial CSIC
Date: 30-12-2007
Publisher: Elsevier BV
Date: 09-2011
Publisher: Routledge
Date: 07-06-2021
Publisher: Informa UK Limited
Date: 03-06-2019
Publisher: Springer Science and Business Media LLC
Date: 02-05-2019
Publisher: BRILL
Date: 15-10-2007
Publisher: WIT Press
Date: 24-06-2014
DOI: 10.2495/CR140741
Publisher: Informa UK Limited
Date: 03-2013
Publisher: Informa UK Limited
Date: 02-01-2023
Publisher: Springer Science and Business Media LLC
Date: 15-08-2006
Publisher: Wiley
Date: 19-05-2015
Publisher: Springer Science and Business Media LLC
Date: 1997
Publisher: Inderscience Publishers
Date: 2014
Publisher: Elsevier BV
Date: 05-2011
Publisher: Palgrave Macmillan UK
Date: 2017
Publisher: Elsevier BV
Date: 03-2020
Publisher: Springer Science and Business Media LLC
Date: 13-02-2020
Publisher: Elsevier BV
Date: 11-2023
Publisher: Elsevier BV
Date: 06-2014
Publisher: Wiley
Date: 24-06-2015
Publisher: Elsevier BV
Date: 12-2019
Publisher: Informa UK Limited
Date: 09-2008
Publisher: Elsevier BV
Date: 03-2017
Publisher: Elsevier BV
Date: 04-2019
Publisher: Informa UK Limited
Date: 02-2014
Publisher: ASME International
Date: 04-2021
DOI: 10.1115/1.4050180
Abstract: With the increasing application of the advanced high strength steel material in the automobile industry, the thickness reduction of the bending area has attracted more and more attention since the product strength is highly influenced by the quality of the bending region. In this paper, three major factors, the thickness reduction, the variation of the local bending radius within the bending zone, and the tooling mark on the product’s surface, are investigated through three different loading patterns for a free U-bending profile numerically and experimentally. The results demonstrate a thinning pattern consists of three peaks over the bending region for large bending ratio (R/t = 2.14) and only one peak for small bending ratio (R/t = 0.5). Corresponding valleys for the local radius are found to match the thinning pattern. Further, the use of finite element simulation can successfully predict the location and the severity of the wear on the product. From the experiment results, even if the metal blank only experienced one stroke, the tooling mark contains both adhesive and abrasive wear. A better understanding of the characteristics of the bending zone is achieved, and the findings can help in improving the design process for forming strategies.
Publisher: Elsevier BV
Date: 10-2021
Publisher: Informa UK Limited
Date: 2008
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 03-2002
DOI: 10.2514/2.4899
Publisher: Elsevier BV
Date: 04-2009
Publisher: Elsevier BV
Date: 09-2013
Publisher: BRILL
Date: 2015
Publisher: Springer Science and Business Media LLC
Date: 07-10-2017
Publisher: Elsevier BV
Date: 2022
Publisher: Springer Science and Business Media LLC
Date: 20-07-2021
Publisher: Elsevier BV
Date: 02-2019
Publisher: Palgrave Macmillan UK
Date: 2017
Publisher: Informa UK Limited
Date: 02-01-2015
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2017
Publisher: Elsevier BV
Date: 03-2014
Publisher: World Scientific Pub Co Pte Lt
Date: 2006
DOI: 10.1142/S021812740601454X
Abstract: Melnikov's method is used to analytically predict the onset of chaotic instability in a rotating body with internal energy dissipation. The model has been found to exhibit chaotic instability when a harmonic disturbance torque is applied to the system for a range of forcing litude and frequency. Such a model may be considered to be representative of the dynamical behavior of a number of physical systems such as a spinning spacecraft. In spacecraft, disturbance torques may arise under malfunction of the control system, from an unbalanced rotor, from vibrations in appendages or from orbital variations. Chaotic instabilities arising from such disturbances could introduce uncertainties and irregularities into the motion of the multibody system and consequently could have disastrous effects on its intended operation. A comprehensive stability analysis is performed and regions of nonlinear behavior are identified. Subsequently, the closed form analytical solution for the unperturbed system is obtained in order to identify homoclinic orbits. Melnikov's method is then applied on the system once transformed into Hamiltonian form. The resulting analytical criterion for the onset of chaotic instability is obtained in terms of critical system parameters. The sufficient criterion is shown to be a useful predictor of the phenomenon via comparisons with numerical results. Finally, for the purposes of providing a complete, self-contained investigation of this fundamental system, the control of chaotic instability is demonstated using Lyapunov's method.
Publisher: BRILL
Date: 06-03-2014
Publisher: Elsevier BV
Date: 06-2016
Publisher: Elsevier BV
Date: 06-2000
Publisher: American Society of Mechanical Engineers
Date: 17-11-1996
Publisher: Elsevier BV
Date: 05-2010
Publisher: Elsevier BV
Date: 10-2008
Publisher: Elsevier BV
Date: 07-2008
Publisher: Routledge
Date: 16-09-2019
Publisher: Brepols Publishers
Date: 2017
Publisher: Informa UK Limited
Date: 19-04-2011
Publisher: American Physical Society (APS)
Date: 10-02-2014
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 05-2021
Publisher: Springer International Publishing
Date: 2017
Publisher: Elsevier BV
Date: 11-2019
Publisher: Trans Tech Publications, Ltd.
Date: 05-2014
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.939.274
Abstract: Incremental Sheet Forming (ISF) is a new-emerging sheet forming process well suited for small batch production or prototyping because it does not need any dedicated dies or punches. In this forming process, sheet metal parts are formed by a smooth-end tool in a stepwise way, during which plastic deformation is highly localized around the tool end. The part geometric accuracy obtained in the current ISF process, however, has not met the industry specification for precise part fabrication. This paper deals with a study on step depth, a critical parameter in ISF, for improving the geometric accuracy, surface quality and formability. Two sets of experiments were conducted to investigate the influence of step depth on part quality. Dimensional accuracy, surface morphology and material fracture of deformed parts were compared and analysed. An optimum value of step depth was suggested for forming a truncated cone. The present work provided significant fundamental information for the development of an advanced ISF control system on tool path control and optimization.
Publisher: Springer Science and Business Media LLC
Date: 1998
Publisher: Research Square Platform LLC
Date: 22-03-2023
Publisher: Springer Science and Business Media LLC
Date: 08-02-2023
Publisher: Trans Tech Publications, Ltd.
Date: 05-2014
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.939.313
Abstract: Incremental sheet forming (ISF) is a promising forming process in which complex 3D shapes are formed from a sheet of metal using a simple moving tool. The efficient prediction of contact forces in ISF is desirable to monitor the forming process, prevent failure, and implement on-line control and process optimization. However, traditional Finite Element (FE) simulation used for force prediction is significantly time-consuming for complex products. The purpose of this study is to investigate the ISF force prediction and characteristics under different forming conditions and build a potential efficient model. In the present work, forces during the cone forming process with different wall angles and step down sizes were recorded and compared. Different force trends were identified and discussed with reference to bending and strain hardening mechanics. Influences of different parameters on designated formability were also qualified which should benefit the product design process. An efficient predictive model based on upper-bound approach was applied for force prediction in this case. Predicted tangential forces were then compared with the experimental results showing relatively good agreement. The limits of the proposed model were also identified and the potential of future improvements were suggested.
Publisher: Springer Science and Business Media LLC
Date: 09-03-2017
Publisher: Springer Science and Business Media LLC
Date: 23-07-2014
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 07-2002
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Paul Meehan.