| 1. |
- Efraimsson, Gunilla, et al.
(författare)
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Analysis of stretched grids as buffer zones in aero-acoustic simulations in two space dimensions
- 2015
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Ingår i: 22nd International Congress on Sound and Vibration, ICSV 2015. - : International Institute of Acoustics and Vibrations. - 9788888942483
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Konferensbidrag (refereegranskat)abstract
- A zone of increasingly stretched grid is a robust and easy-to-use way to avoid unwanted reflections at artificial boundaries in aero-acoustic simulations. There are two main damping mechanisms, dissipation and under-resolution of a traveling wave, respectively. In this paper the behavior of acoustic waves in two space dimensions are studied via analysis of solutions to a semi-discrete linear boundary value problem. The solutions of the linear problem is compared to solutions of the linearized Euler equations.
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| 2. |
- Hosseini, N., et al.
(författare)
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Transfer function calculations of segregated elements in a simplified slit burner with heat exchanger
- 2015
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Ingår i: 22nd International Congress on Sound and Vibration, ICSV 2015. - : International Institute of Acoustics and Vibrations. - 9788888942483
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Konferensbidrag (refereegranskat)abstract
- A simplified burner-heat exchanger system is numerically modelled in order to investigate the effects of different elements on the response of the whole system to velocity excitation. We model the system in a 2D CFD code, considering a linear array of multiple Bunsen-type flames with heat exchanger tubes downstream the flames. Thermoacoustic instability is one of the main issues in lean premixed combustion systems, especially domestic boilers. In compact condensing boilers the close distance between the burner surface and the heat exchanger has increased the importance of studying the interactions between the flames and the heat exchanger. The elements corresponding to the heat balance in the system are the flame as heat source and burner deck and heat exchanger as heat sinks. We use both transfer function and transfer matrix approaches to identify the response of these elements to a step function excitation of velocity at the inlet of the domain. Steady-state simulations show that the contribution of the burner deck to the heat balance of the whole system is negligible, leaving the flame and heat exchanger as main contributors to the response of the system. We separately investigate the behavior of these two elements by modeling cases with flame only and heat exchanger only. Then we calculate the behavior of the combined system and compare it to the results of modeling a case with flame and heat exchanger together. These results show that, assuming linear behavior of the elements, it is possible to predict the system behavior via its constructing elements. Further investigations of the effects of other parameters and the limits, within which the assumptions are valid, are currently in progress.
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| 3. |
- Källström, Elisabeth, et al.
(författare)
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Analysis of Automatic Transmission Vibration for Clutch Slippage Detection
- 2015
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Ingår i: 22nd International Congress on Sound and Vibration 2015 (ICSV 22). - : Curran Associates, Inc.. - 9781510809031
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Konferensbidrag (refereegranskat)abstract
- Heavy duty construction equipment is generally equipped with automatic transmission enablingto change gear ratio automatically. The clutches in an automatic transmission transfer torquefrom the engine to the gearbox and clutch failures may result in costly downtime of constructionequipment. To prevent costly downtime of construction equipment, condition monitoring in com-bination with condition based maintenance may be utilized. Different sensor data are collectedon a machine that enables condition monitoring. Vibration have been measured on an automatictransmission in a construction equipment machine during controlled driving sessions, with andwithout clutch slippage, on a test track. An initial investigation of the vibration measured on theautomatic transmission have been carried out with the purpose to find out if the vibration maycontain reliable information related to clutch slippage considered to be abnormal. Initial signalanalysis of the data have been carried out using Spectrogram and Spectral Kurtosis methods. Theresults indicate that information related to abnormal clutch slippage may be extracted from vibra-tion measured on an automatic transmission in a construction equipment machine.
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| 4. |
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| 5. |
- Lyu, Yezhe, et al.
(författare)
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Development of a noise related track maintenance tool
- 2015
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Ingår i: 22nd International Congress on Sound and Vibration, ICSV 2015. - : International Institute of Acoustics and Vibrations. - 9788888942483
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Konferensbidrag (refereegranskat)abstract
- The purpose of this work-package within the Quiet-track, FP7, is to develop a noise related track maintenance tool, in the form of an on-board measurement system. As a first step, lab scale tests using a pin-on-disc tribometer were used in order to distinguish how noise changes when the wear mechanism in a sliding contact shifts from normal wear to severe and catastrophic wear. Once the potential for using sound as an indication of severe wear transitions was established, full scale tests were carried out with a rapid transit (metro) train, type C20. The train was equipped with microphones that continuously measured the sound pressure near the wheel rail contact. In order to provoke severe/catastrophic wear, the test train was run in a curve with small radius, and the rails and wheels were carefully cleaned before the tests. The same kind of transfer from mild to severe/catastrophic wear was identified on the full scale test as in the laboratory scale test, confirmed by studying the surface topography and the morphology of the wear particles. Moreover, the full scale test results showed that the sound pressure changed significantly when transferring from mild to severe wear in agreement with the pin-on-disc test results. By comparing noise from the inner wheel/rail contact to noise form the outer wheel/rail contact a wear indication value for the outer wheel/rail contact is suggested in this study. This value can be seen as an advanced parameter from which the probability of severe wear, in the wheel flange/rail gauge face contact of the outer contact, can be estimated. At present, a real time condition monitoring system is set up in Stockholm (Metro line 1) in order to validate the results.
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| 6. |
- Mohammadnejad, Mostafa, et al.
(författare)
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FINITE ELEMENT MODELING OF DYNAMIC PROPERTIES OF POWER SUPPLY FOR AN INDUSTRIAL APPLICATION
- 2015
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Ingår i: PROCEEDINGS OF THE 22ND INTERNATIONAL CONGRESS ON SOUND AND VIBRATION. - : INT INST ACOUSTICS & VIBRATION. - 9788888942483
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Konferensbidrag (refereegranskat)abstract
- In this study, the dynamic properties of the mechanic structure of Power Supply for an industrial application is considered. A finite element model of the Power Supply mechanic structure has been generated with the aid of the MSC Marc software. Based on the FE model; modal analysis has been carried out and the eigenfrequencies and eigenmodes for the FE model have been calculated in a suitable frequency range. Relevant frequency response functions for the FE model have been produced using dynamic harmonic analysis. To validate and update the FE model, experimental modal analysis has been carried out on a Power Supply. For the experimental modal analysis the MIMO method the polyreference least-squares complex exponential method has been used. Based on the updated FE model some modified Power Supply designs are suggested with improved dynamic properties in an adequate frequency range.
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| 7. |
- Peerlings, Luck, et al.
(författare)
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Estimating the uncertainty in stepped sine measurements performed under partially stochastic conditions
- 2015
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Ingår i: 22nd International Congress on Sound and Vibration, ICSV 2015. - : International Institute of Acoustics and Vibrations. - 9788888942483
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Konferensbidrag (refereegranskat)abstract
- Stepped sine measurements are often performed in environments where there is a large contribution of background noise to increase the signal to noise ratio and obtain more accurate measurements. Due to time constraints or to guarantee the stability of the investigated system a single long measurement is often taken and the statistical properties of the results are based on this single measurement. When the background noise is not completely stochastic in nature, for example there is a tonal component present, the obtained statistics can lead to the wrong results because the underlying assumptions to derive these statistics are violated. In this paper an expression is derived to estimate the uncertainty in a stepped sine measurements based on the background noise spectrum. In this way an accurate estimate of the uncertainty can be obtained even when it is not possible to perform enough statistically independent measurements. The results are based on synchronous demodulation using the Hilbert transform and the expressions are derived both in the continuous and discrete time domain so that they can be easily applied.
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| 8. |
- Premachandran, Rammohan, et al.
(författare)
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SIGNAL ANALYSIS FOR PERFORMANCE MONITORINGOF DRILLING WITH DOWN THE HOLE (DTH) ROCK DRILLS
- 2015
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Ingår i: PROCEEDINGS OF THE 22ND INTERNATIONAL CONGRESS ON SOUND AND VIBRATION: MAJOR CHALLENGES IN ACOUSTICS, NOISE AND VIBRATION RESEARCH, 2015. - : INT INST ACOUSTICS & VIBRATION. - 9788888942483
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Konferensbidrag (refereegranskat)abstract
- Today rock drilling operations mainly relies on the experience of the operators. Expe-rienced drillers observes the sound produced by the drilling machinery and in general, base their judgments on their intuition. An efficient drill monitoring system, providing reliable and robust in-formation on the performance of the drilling process, is likely to provide experienced drillers with additional information, to further improve the drilling process. Such a system is also likely to provide guidance to inexperienced drillers to improve their drilling performance concerning quality and efficiency. To enable monitoring of drilling performance in down the hole (DTH) rock drilling, simultaneous measurements of vibrations, with the aid of accelerometers mounted at specific locations on the drill rig, and other quantities such as different line pressures controlling different movements of the drill string are considered in combination with suit-able signal processing methods. A number of properties, e.g. spectral properties, of the vibration sig-nals and the pressure line signals under good drilling and bad drilling conditions are compared. Both the vibration and pressure signals display distinguishable properties between the case of "good" drill-ing and the case of "bad" drilling.
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| 9. |
- Zein, A., et al.
(författare)
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E-laboratories for sound and vibration education
- 2015
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Ingår i: 22nd International Congress on Sound and Vibration, ICSV 2015. - : International Institute of Acoustics and Vibrations. - 9788888942483
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Konferensbidrag (refereegranskat)abstract
- Several universities face the problem of overcrowded classes and laboratories; hence, there is a difficulty of delivering high quality education, which will affect the quality of graduating engineers. It is needed to introduce the missing experimental part in teaching of the courses without the burden of building new labs. This is done by making these experiments available virtually over the internet, available to the students 24 hours to repeat the experiment as many times as necessary to meet the learning objectives of the experiment. Several elearning programs exist nowadays with regards to courses and teaching material but there are very few e-laboratories available worldwide. Some of the e-laboratories are fully simulated and some are real hardware at the university lab and controlled over the internet. There are a number of technical challenges to realize these e-laboratories; the learning management system to handle this virtual campus, the communication between the client machines and the hardware experiments, and the transfer of data to the client machine for further postprocessing. This paper introduces some of the e-laboratories in Sound and Vibration Education, which were developed and implemented within a project funded by the European Commission through the Tempus Program.
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| 10. |
- Österlöf, Richard, et al.
(författare)
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A finite strain viscoplastic constitutive model for filled rubber
- 2015
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Ingår i: 22nd International Congress on Sound and Vibration, ICSV 2015. - : International Institute of Acoustics and Vibrations. - 9788888942483
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Konferensbidrag (refereegranskat)abstract
- A phenomenological material model for carbon black filled natural rubber based on the multiplicative split of the deformation gradient is implemented for finite strains in three dimensions. This is a generalising of the authors previous work, where the uniaxial rheological equivalent is a smooth friction element in series with a generalized Maxwell chain. The aim of the paper is to demonstrate the advantage of this viscoplastic modelling approach. With only 5 material parameters, the storage and loss modulus is calculated for strain amplitudes between 0.2-50% strain and 0.5-20 Hz, with very encouraging results. These are reasonable ranges of interest when designing the reliability of load bearing components, such as vibration isolators for drivelines in the automotive industry. The Fletcher-Gent effect is well captured, where the strain rate dependency on the storage modulus is higher at smaller strain amplitudes. In addition, the storage and loss modulus are similar to measurements in literature, both in value and shape over the entire range of amplitudes and frequencies. It should be emphasized that capturing both the storage and loss modulus of a material is essential for a material model's capability to describe more complex loading situations than sinusoidal loading. A future implication of the developed model is that it enables realistic simulation of vibration isolators early in the design process whereby extensive physical testing can be reduced, saving both time and money.
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