| 1. |
- Abata, E., et al.
(författare)
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Study of energy response and resolution of the ATLAS barrel calorimeter to hadrons of energies from 20 to 350 GeV
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 621:1-3, s. 134-150
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Tidskriftsartikel (refereegranskat)abstract
- A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20-350 GeV and beam impact points and angles corresponding to pseudo-rapidity values in the range 0.2-0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit. (C) 2010 Published by Elsevier B.V.
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| 2. |
- Meyer, E., et al.
(författare)
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The state of the art in beyond 5G distributed massive multiple-input multiple-output communication system solutions
- 2022
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Ingår i: Open Research Europe. - : F1000 Research Ltd. - 2732-5121. ; 2
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Forskningsöversikt (refereegranskat)abstract
- Beyond fifth generation (5G) communication systems aim towards data rates in the tera bits per second range, with improved and flexible coverage options, introducing many new technological challenges in the fields of network architecture, signal pro- cessing, and radio frequency front-ends. One option is to move towards cell-free, or distributed massive Multiple-Input Multiple-Output (MIMO) network architectures and highly integrated front-end solutions. This paper presents an outlook on be- yond 5G distributed massive MIMO communication systems, the signal processing, characterisation and simulation challenges, and an overview of the state of the art in millimetre wave antennas and electronics.
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| 3. |
- Smirnova, Tatiana, et al.
(författare)
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Accurate FE-modeling of a Boring Bar Correlated with Experimental Modal Analysis
- 2007
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Konferensbidrag (refereegranskat)abstract
- In metal cutting the vibration problem of boring bars remains to be one of the most problematic and productivity degrading. A boring bar is very flexible and easily subjected to vibrations due to its large length to diameter ratio, which generally is required to perform internal turning. The boring bar vibrations appear at its first eigenfrequncies, which correspond to the boring bar’s first bending modes that are affected by boring bar’s boundary conditions applied by the clamping and workpiece in the lathe. Therefore the investigation of spatial dynamic properties of boring bars is of great importance for the understanding of the mechanism and nature of boring bars vibrations. This paper addresses the problem of building an accurate 3-D finite element model of a boring bar with ”free-free” boundary conditions. The questions of appropriate meshing and its influence on the boring bar’s spatial dynamic properties estimates as well as modeling the affect of mass loading are discussed. The results from simulations of 3-D finite element model of the boring bar, i.e. its first eigenmodes and eigenfrequencies, are correlated with the results obtained both from experimental modal analysis and analytical calculations using an Euler-Bernoulli model.
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| 4. |
- Smirnova, Tatiana, et al.
(författare)
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Estimation of an active boring bar´s control path FRF:s by means of its 3-D FE-model with Coulomb friction
- 2008
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Konferensbidrag (refereegranskat)abstract
- In metal cutting boring bar vibrations may be attenuated using an active boring bar with an embedded piezoceramic actuator, attached error sensor and a suitable controller. In the design of active boring bars accurate modelling of control path frequency response functions (FRF), i.e. FRF between the actuator voltage and the boring bars response signal (which is commonly acceleration), are of importance, e.g. for the decision concerning the favorable position of the actuator inside the active boring bar to maximize vibration suppression. This paper addresses the influence of the Coulomb friction force on the transfer function estimates between the actuator voltage and the boring bar acceleration calculated based on the ”3-D” FE model of an active boring bar. Two types of approximations of the Coulomb friction force, the arctangent and the bilinear models, are evaluated concerning modelling the contact between the surface of the boring bar and the clamping house. Results of incorporation of the two different Coulomb friction force models into the active boring bar’s SDOF model as well as ”3-D” FE-model enabling variable contact between the boring bar, the clamping screws and the clamping house are presented in terms of control path FRF:s.
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| 5. |
- Smirnova, Tatiana, et al.
(författare)
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Identification of Spatial Dynamic Properties of the Boring Bar by Means of Finite Element Model : Comparison with Experimental Modal Analysis and Euler-Bernoulli Model
- 2006
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Konferensbidrag (refereegranskat)abstract
- In metal cutting the boring operation is known to be one of the most troublesome regarding vibration. Boring bars are frequently subjected to vibrations originated from the load applied by the workpiece material deformation process. These vibrations are easily excited due to the boring bars general geometric dimensions, i.e. large length to diameter ratio. Large overhang is usually required to perform internal boring operation and is a consequence the vibration may frequently reach extremely high levels, which result in a poor surface finish, reduced tool life and annoying noise level in the working environment. The vibration problem is directly related to the first bending modes of a boring bar. Therefore investigations of the boring bar’s spatial dynamic properties are of a great importance. The results from experimental modal analysis show that a conventional analytical approach - calculation of boring bar eigenfrequencies using an Euler-Bernoulli model - results in rough estimates. This can be explained by existing nonlinearities introduced e.g. in the areas of contact between the boring bar and the clamping bolts as well as the clamping house, which is not considered in the analytical model where the boring bar instead is assumed to be rigidly clamped. Therefore the estimation of the eigenfrequencies and eigenmodes of a boring bar based on a 3-D finite element model of the clamped boring bar incorporating contact between the bar and the bolts respective the clamping house is a more beneficial strategy. This paper addresses the estimation of the boring bar’s first eigenfrequencies and corresponding eigenmodes based on the 3-D finite element model. The results are compared with results obtained both from experimental modal analysis and an analytical Euler-Bernoulli model.
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| 6. |
- Smirnova, Tatiana, et al.
(författare)
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INITIAL EXPERIMENTS WITH A FINITE ELEMENT MODEL OF AN ACTIVE BORING BAR
- 2007
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Konferensbidrag (refereegranskat)abstract
- One of the most troublesome sources of vibration in metal cutting is the vibration caused by internal turning operations. A boring bar is a tool holder which is used to machine deep precise cavities inside a workpiece material. In order to perform this internal turning the boring bar usually has a large length-to-diameter ratio, and thus the boring bar vibrations are easily excited by the material deformation process during metal cutting. The vibrations are related to the lower order fundamental bending modes of the boring bar. To overcome the vibration problem an active control technique can be used. In particular, by utilizing an active boring bar with an embedded piezoceramic actuator and a suitable controller, the primary boring bar vibrations originating from the material deformation process may be suppressed with secondary "anti-" vibrations. In order to produce an active boring bar several decisions should be done, i.e. the characteristics of the actuator, the position of the actuator in the boring bar, etc. This usually implies that several prototypes of an active boring bar should be produced and tested, thus the design of an active boring bar is a tedious and costly procedure. Therefore a mathematical model which would incorporate the piezo-electric effect in order to predict the dynamic properties and the response of the active boring bar are of great importance. This paper addresses the development of a "3-D" finite element model of the system "boring bar-actuator-clamping house". The spatial dynamic properties of the active boring bar, i.e. its natural frequencies and mode shapes, as well as the transfer function between the voltage applied to the actuator and acceleration of boring bar are calculated based on the "3-D" FE model and compared to experimentally obtained estimates.
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| 7. |
- Smirnova, Tatiana, et al.
(författare)
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Investigation Concerning Actuator Position in an Active Boring Bar Regarding it´s Performance by Means of "3-D" Finite Element Models
- 2008
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Konferensbidrag (refereegranskat)abstract
- Active boring bars may be used for active vibration suppression during internal turning operation in metal cutting. This technique is based on a feedback control scheme of the boring bar vibrations measured by an attached sensor (usually accelerometer) where secondary "anti"- vibrations are applied by means of an embedded piezoelectric actuator. In order to design an active boring bar, several issues have to be addressed, i.e. selecting the characteristics of the actuator, the actuator size, the position of the actuator in the boring bar, etc. A mathematical model of the active boring bar incorporating the piezoelectric effect, e.g. a "3-D" finite element, may simplify designing process. In this paper several "3-D" finite element models of the system "boring bar - actuator - clamping house" are developed for a set of actuator positions. The favorable actuator position is basically selected as the one resulting in the greatest "stiffness" of the active boring bar at the frequency corresponding to the first boring bar fundamental bending mode.
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| 8. |
- Smirnova, Tatiana, et al.
(författare)
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Investigation Concerning Dynamic Properties of an Active Boring Bar Regarding its Perfomance by Means of ”1-D” Finite Element Models
- 2009
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Konferensbidrag (refereegranskat)abstract
- Active boring bars may be used for active vibration suppression during internal turning operations in metal cutting. This technique is typically based on a feedback control scheme of the boring bar vibrations measured by an attached sensor (usually accelerometer) where secondary ”anti”-vibrations are induced by means of an piezoelectric actuator embedded into a cavity located in the boring bar’s longitudinal direction below its central line. Design procedure of an active boring bar requires the selection of the characteristics of the actuator, the actuator size, the position of the actuator in the boring bar, etc. A ”3-D” finite element model of the active boring bar incorporating the piezoelectric effect was proposed previously to simplify the design process. The set of actuator positions used to decide the favorable actuator position was limited due to time-consuming transient response calculations of the ”3-D” finite element model of an active boring bar. In the present paper a larger set of ”1-D” finite element models of a boring bar (which model the position of the cavity for the actuator but do not incorporate piezoelectric effect) was used to predict dynamic properties of the active boring bar. Based on these results a small set of favorable actuator positions is selected for implementation in ”3-D” finite element models of active boring bars.
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| 9. |
- Smirnova, Tatiana, et al.
(författare)
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Investigation of Boring Bar Mode Shape Rotation by Experimental Modal Analysis in Correlation with Finite Element Modeling
- 2006
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Konferensbidrag (refereegranskat)abstract
- Productivity degrading vibration problems are traditional in metal cutting, in particular in internal turning, when the boring bar is long and slender. The high levels of vibrations arise at the boring bar’s natural frequencies corresponding to its fundamental bending modes. The vibrations are dominating at the boring bar’s eigenfrequency in the cutting speed direction, since the cutting force has the largest component in this direction. The negative effects of vibrations, e.g. poor surface finish, reduced tool life, high sound pressure levels in the working environment etc., can be eliminated for instance by using passive tuned damper or active control. The level of success implementing any of these methods is dependent on the knowledge of the dynamic properties of tooling structure - the interface between the cutting tool or insert and the machine tool - involved. Results from experimental modal analysis on the boring bar clamped in a lathe reveal a rotation of the mode shapes with respect to the cutting speed and cutting depth direction. The paper addresses boring bar mode shape rotation phenomenon and discusses its possible sources based on results obtained from experimental modal analysis of two systems: boring bar with original boundary conditions and boring bar with linearized boundary conditions in correlation with results obtained from corresponding 3-D finite element models.
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| 10. |
- Smirnova, Tatiana, et al.
(författare)
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Modeling a Clamped Boring Bar using Euler-Bernoulli Beam Models with Various Boundary Conditions
- 2009
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Konferensbidrag (refereegranskat)abstract
- This paper addresses modeling of a clamped boring bar using Euler-Bernoulli beam theory. Euler-Bernoulli beams with a number of different boundary conditions were used to model a clamped boring bar. Estimates of the boring bar's natural frequencies and mode shapes were produced with each of the boring bar models. The estimates produced by the distributed-parameter system models are compared with eigenfrequencies and mode shapes estimated based on experimental modal analysis of the actual boring bar clamped in a lathe.
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