Autor: Nicolescu, M. - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Problème de lanalyticité par rapport à un opérateur linéaire
Autorzy:: Nicolescu, M.
Powiązania:: https://bibliotekanauki.pl/articles/1388064.pdf
Data publikacji:: 1958
Wydawca:: Polska Akademia Nauk. Instytut Matematyczny PAN
Źródło:: Studia Mathematica; 1957-1958, 16, 3; 353-363
0039-3223
Pojawia się w:: Studia Mathematica
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Dynamic parameter identification in nonlinear machining systems
Autorzy:: Nicolescu, M.
Archenti, A.
Powiązania:: https://bibliotekanauki.pl/articles/100167.pdf
Data publikacji:: 2013
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:: machining system
dynamic parameters
white noise excitation
self-excited vibration
Opis:: The demand for enhanced performance of production systems in terms of quality, cost and reliability is ever increasing while, at the same time, there is a demand for shorter design cycles, longer operating life, minimisation of inspection and maintenance needs. Experimental testing and system identification in operational conditions still represent an important technique for monitoring, control and optimization. The term identification refers in the present paper to the extraction of information from experimental data and is used to estimate operational dynamic parameters for machining systems. Such an approach opens up the possibility of monitoring the dynamics of machining systems during operational conditions, and can also be used for control and/or predictive purposes The machining system is considered nonlinear and excited by random loads. Parametric and nonparametric techniques are developed for the identification of the nonlinear machining system and their application is demonstrated both by numerical simulations and in actual machining operations. Discrimination between forced and self-excited vibrations is also presented. The ability of the developed methods to estimate operational dynamic parameters ODPs is presented in practical machining operations.
Źródło:: Journal of Machine Engineering; 2013, 13, 3; 91-116
1895-7595
2391-8071
Pojawia się w:: Journal of Machine Engineering
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Issues in machining of hollow core honeycomb sandwich structures by abrasive waterjet machining
Autorzy:: Devadula, S.
Nicolescu, M.
Powiązania:: https://bibliotekanauki.pl/articles/99450.pdf
Data publikacji:: 2013
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:: abrasive waterjet
machining
honeycomb sandwich material
Opis:: Machining of hollow core honeycomb sandwich materials is a challenging job as the mechanical properties of various layers (skin, core) are quite dissimilar, and the conventional solid cutting tool experiences a sudden change of conditions while machining that might lead to damage on the tool/part. Although, abrasive waterjets (AWJs) is highly efficient in the machining of advanced composite materials due to their unique characteristics, efficient machining of sandwich structures by AWJs needs many challenges to be addressed. This work presents various issues observed in AWJ machining of carbon- and glass- fiber skin based, aluminum sandwich structure composite materials, and the limitations of AWJs in processing these exotic materials. Finally, possible strategies for efficient machining of honeycomb structures were proposed for future investigation.
Źródło:: Journal of Machine Engineering; 2013, 13, 1; 117-124
1895-7595
2391-8071
Pojawia się w:: Journal of Machine Engineering
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: System dynamics as a decision support system for machine tool selection
Autorzy:: Adane, T. F.
Nicolescu, M.
Powiązania:: https://bibliotekanauki.pl/articles/99389.pdf
Data publikacji:: 2016
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:: machine selection
decision making
performance analysis
system dynamics modelling
Opis:: The worldwide competitive economy, the increase in sustainable issue and investment of new production line is demanding companies to choose the right machine from the available ones. An improper selection can negatively affect the overall performance of the manufacturing system like productivity, quality, cost and companys responsive manufacturing capabilities. Thus, selecting the right machine is desirable and substantial for the company to sustain competitive in the market. The ultimate objective of this paper is to formulate a framework for machining strategy and also provide methodology for selecting machine tool from two special purpose machine tools in consideration of interaction of attributes. A decision support system for the selection of machine tool is developed. It evaluates the performance of the machining process and enhances the manufacturer (decision maker) to select the machine with respect to the performance and the pre-chosen criteria. Case study was conducted in a manufacturing company. A system dynamics modelling and simulation techniques is demonstrated towards efficient selection of machine tool that satisfy the future requirement of engine-block production.
Źródło:: Journal of Machine Engineering; 2016, 16, 3; 102-125
1895-7595
2391-8071
Pojawia się w:: Journal of Machine Engineering
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Performance Evaluation of Machining Strategy for Engine-Block Manufacturing
Autorzy:: Tigist, A. F.
Bianchi, M. F.
Archenti, A.
Nicolescu, M.
Powiązania:: https://bibliotekanauki.pl/articles/100037.pdf
Data publikacji:: 2015
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:: process modelling
machining strategies
engine-block manufacturing
dynamic modelling
Opis:: This paper will introduce a novel methodology for the performance evaluation of machining strategies of engine-block manufacturing. The manufacturing of engine components is vital to the automotive and vehicle manufacturing industries. Machining are a critical processes in the production of these parts. To survive and excel in the competitive manufacturing environment, companies need to improve as well as update their machining processes and evaluate the performance of their machining lines. Moreover, the lines and processes have to be robust in handling different sources of variation over time that include such examples as demand fluctuations, work-piece materials or even any changes in design specifications. A system dynamics modelling and simulation approach has been deployed to develop a methodology that captures how machining system parameters from the machining process are interacted with each other, how these connections drive performance and how new targets affect process and machine tool parameters through time. The developed model could provide an insight of how to select the crucial machining system parameters and to identify the effect of those parameters on the output of the system. In response to such an analysis, this paper provides (offers) a framework to examine machining strategies and has presented model that is useful as a decision support system for the evaluation and selection of machining strategies. Here a system dynamics methodology for modelling is applied to the milling operation and the model is based on an actual case study from the engine-block manufacturing industry.
Źródło:: Journal of Machine Engineering; 2015, 15, 4; 81-102
1895-7595
2391-8071
Pojawia się w:: Journal of Machine Engineering
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: New Paradigm in Control of Machining Systems Dynamics
Autorzy:: Nicolescu, M.
Frangoudis, C.
Semere, D.
Archenti, A.
Rashid, A.
Powiązania:: https://bibliotekanauki.pl/articles/99497.pdf
Data publikacji:: 2015
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:: machining system
parametric identification
operational dynamic parameters
joint interface module
Opis:: The increasing demands for precision and efficiency in machining call for effective control strategies based on the identification of static and dynamic characteristics under operational conditions. The capability of a machining system is significantly determined by its static and dynamic stiffness. The aim of this paper is to introduce novel concepts and methods regarding identification and control of a machining system’s dynamics. After discussing the limitations in current methods and technologies of machining systems’ identification and control, the paper introduces a new paradigm for controlling the machining system dynamics based on design of controllable structural Joint Interface Modules, JIMs, whose interface characteristics can be tuned using embedded actuators. Results from the laboratory and industrial implementation demonstrate the effectiveness of the control strategy with a high degree of repeatability.
Źródło:: Journal of Machine Engineering; 2015, 15, 3; 117-137
1895-7595
2391-8071
Pojawia się w:: Journal of Machine Engineering
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Design and dynamic characterization of composite material dampers for parting-off tools
Autorzy:: Daghini, L.
Archenti, A.
Nicolescu, C. M.
Powiązania:: https://bibliotekanauki.pl/articles/99974.pdf
Data publikacji:: 2010
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:: damping
parting-off
model-based identification
stability
operational damping ratio
operational frequencies
Opis:: This paper introduces a novel design for parting-off tools and the method to characterize their performance. The principle followed in the design phase was to enhance the damping capability minimizing the loss in static stiffness through implementation of composite material interfaces. The tool has been characterized by the dynamic characteristics criterion, i.e. frequency and damping ratio, of the machining system, as well as the roughness of the machined surface criterion. This paper demonstrates a new model-based method for characterizing the machining system dynamic properties, applied, in this sThe presented mathematical model of the machining system is based on the data recorded by a microphone during operational conditions. In this way, a step beyond the classical method of analyzing the dynamics of a machining system, which separately identifies the structural and process parameters is taken. The analyses together with the experimental results proved that the parting-off tool was able to machine over a wide range of cutting parameters. It was found that the limiting factor for increasing cutting parameters is not the damping capability of the tool but the tool clamping system stiffness and the workholding system dynamic properties. This implies that, in order to further optimize the machining performance, it is vital to take consideration not only the tool-clamp-turret system but the whole machining system.
Źródło:: Journal of Machine Engineering; 2010, 10, 2; 57-70
1895-7595
2391-8071
Pojawia się w:: Journal of Machine Engineering
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Improving machining performance against regenerative tool chatter through adaptive normal pressure at the tool clamping interface
Autorzy:: Fu, Q.
Rashid, A.
Nicolescu, C. M.
Powiązania:: https://bibliotekanauki.pl/articles/99845.pdf
Data publikacji:: 2013
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:: chatter
tool
internal turning
vibration
clamping
damping
interface
Opis:: Chatter in machining process is one of the common failures of a production line. For a cantilever tool, such as a boring bar, the rule of thumb requires the overhang length of the tool to be less than 4 times the diameter. The reason is because longer overhang will induce severe tool vibration in the form of chatter during machining. When a longer overhang than 4 times diameter is necessary for performing special machining operations, damping methods are needed to suppress tool chatter. One of the methods is the constrained layer damping method. Materials, such viscoelastic material, are applied in the vibration node regions of the structure to absorb the concentrated vibration strain energy and transform the mechanical energy to heat. With a cantilever tool clamped in a tool holder, the clamping interface is usually the vibration node region. The friction in the joint interface with low normal pressure became another source of damping and can be used for tool chatter suppression in mechanical structures. Joint interfaces are well known to possess normal pressure dependent stiffness and damping. The normal pressure's effect on the structures frequency response function had been observed by H. Akesson [1] et al, and L.Mi [2] et al. However, the direct effect of the joint interface normal pressure on machining process stability hasn't been investigated. In this paper, a cantilever tool with 6,5 overhang length to diameter ratio is investigated. The direct effect of the tool clamping interface's normal pressure on the machining process stability is studied. Three different levels of clamping normal pressure are tested with an internal turning process. The machining results indicate another adaptable solution on shop floor for suppressing tool chatter.
Źródło:: Journal of Machine Engineering; 2013, 13, 1; 93-105
1895-7595
2391-8071
Pojawia się w:: Journal of Machine Engineering
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Experimental analysis of a machining system with adaptive dynamic stiffness
Autorzy:: Frangoudis, C.
Nicolescu, C. M.
Rashid, A.
Powiązania:: https://bibliotekanauki.pl/articles/100189.pdf
Data publikacji:: 2013
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:: vibrations
milling
damping
stiffness
adaptive structure
Opis:: A main consideration in the operation of machine tools is vibrations occurring during the cutting process. Whether they are forced vibrations or self-excited ones, they have pronounced effects on surface quality, tool life and material removal rate. This work is an experimental study of interactions between natural characteristics, control parameters and process parameters of a machining system designed with adaptive dynamic stiffness. In order to comprehend these interactions, the effect of changes in dynamic stiffness on the system's response is examined. The system under study consists of an end-milling tool, a steel workpiece and a work holding device with controllable stiffness. Natural dynamic characteristics of the system components are determined through modal impact testing. Then the behaviour of the whole machining system is examined under both high and low cutting speed conditions by analysing vibration levels using acceleration signals acquired through a tri-axial sensor mounted on the workpiece. Cutting is performed in both directions of the horizontal plane of a CNC milling machine. In both cases the results are presented for two extremes of stiffness and damping in the work holding device. The effect of control parameters on the system's natural characteristics could be identified together with a relation between these parameters and the system's response in high and low cutting speed conditions. The high-damping configuration reduces the vibration amplitudes significantly, while the increase of pre-stress has a different effect depending on the cutting conditions.
Źródło:: Journal of Machine Engineering; 2013, 13, 1; 49-63
1895-7595
2391-8071
Pojawia się w:: Journal of Machine Engineering
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Evaluation and representation of machine tool deformations
Autorzy:: Archenti, A.
Osterlind, T.
Nicolescu, C. M.
Powiązania:: https://bibliotekanauki.pl/articles/99452.pdf
Data publikacji:: 2011
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:: machine tool
testing
deformation
static stiffness
circular test
loaded double ball bar
Opis:: This paper presents a novel test concept for the evaluation of the accuracy of NC machine tools. The evaluation of machine tools deformations is performed by help of a device similar to the double ball bar (DBB) with the difference that an adjustable load generated by the devic can be applied between spindle nose and machine tool table. This load eliminates the play existing in machine tool joints, thus reproducing the testing conditions that exist during machining. Collected data are used to plot diagrams displaying characteristic aspects of machine tool performance and a number of key figures such as static stiffness may be determined. The data can also be used for trend analysis; to predict any accuracy deviations, and further to conduct preventive maintenance instead of emergency calls. The determined static behaviour could also be used to improve digital models for process simulations and compensation of errors that are caused by deflection.
Źródło:: Journal of Machine Engineering; 2011, 11, 4; 105-117
1895-7595
2391-8071
Pojawia się w:: Journal of Machine Engineering
Dostawca treści:: Biblioteka Nauki

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