| 1. |
- Andersson, Patrik, 1974, et al.
(författare)
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Boundary Element Method for Intensity Potential Approach : Predicting the Radiated Sound Power from Partially Enclosed Noise Sources
- 2012
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Ingår i: Acta Acoustica united with Acustica. - : S. Hirzel Verlag. - 1610-1928 .- 1861-9959. ; 98:4, s. 588-599
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes the boundary element method for the intensity potential for prediction of high-frequency sound power flow through partial enclosures. The intensity potential approach is based on the local power balance in a lossless medium and the Helmholtz decomposition of the vector field of time-averaged sound intensity. The result is a Poisson equation for a scalar intensity potential. The intensity potential formulation and the boundary element method are both suitable for exterior problems. The governing equations of the intensity potential and the boundary element method for solving this problem are presented. Results from the proposed method are compared with experimental results, for the case of radiated sound power in one-third-octave bands from sources in a partial enclosure. The results show that the method is applicable for estimation of global radiated sound power in one-third-octave bands in the high-frequency range.
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| 2. |
- Lindberg, Eskil, 1979-, et al.
(författare)
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A vibro-acoustic reduced order model using undeformed coupling interface substructuring - Application to rubber bushing isolation in vehicle suspension systems
- 2014
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Ingår i: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 78, s. 43-50
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Tidskriftsartikel (refereegranskat)abstract
- A vibro-acoustic reduced order model (ROM) based on a substructuring method using undeformed coupling interfaces (UCI) is proposed. The method may be used to reduce the order of a global problem, this by subdividing the global system to substructures interacting through UCI's. The local dynamic stiffness of each substructure may then be modelled with a, for that particular problem, best suited description. The feasibility of the method is demonstrated by a sensitivity analysis of the vibro-acoustic power isolation in a vehicle suspension system, comprising of a link arm connected to a vehicle car body through two rubber bushings. The link arm ROM is a component mode synthesis (CMS)-UCI, the rubber bushing model is a UCI-ROM derived from a 2D axisymmetric model using a frequency dependent visco-elastic material model. Finally the car body model is a frequency dependent UCI-ROM from a full car body finite element model. It is shown that the UCI-ROM approach efficiently can be used for parametric studies on a substructure level. The results suggest that the performed reorientation of the rubber bushings can alter, with orders of magnitude, the energy flow into the car.
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| 3. |
- Lindberg, Eskil, 1979-
(författare)
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A Vibro-Acoustic Study of Vehicle Suspension Systems : Experimental and Mathematical Component Approaches
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objective of the present work is to study the vehicle suspension as a vibro-acoustic system of high complexity, consisting of many sub-systems with fundamentally different acoustical properties. In a parallel numerical and experimental modelling effort, important contributions to the understanding of its behaviour have been achieved. These findings are based on a balance between component investigations and global modelling of the complete system; they have been formulated for the transmission of both tyre-road excitation and friction-induced vibrations in the brake system.Initially an experimental study was conducted on a full vehicle test rig studying the broadband interior brake noise problem of, here named, roughness noise. The purpose of the study was twofold: first, to determine if the transmission from the source to the interior of the vehicle was structure-borne; second, to study the complexity of the suspension as a vibro-acoustic system. Parameters a_ecting the vibro-acoustic source were varied to gain understanding of the source mechanisms. This experimental study laid the foundation of the first part of this thesis (paper A) and provided the directions for the second part, the development of a mathematical modelling approach (paper B and C). In these two papers, methods for analysing the complex vibro-acoustic transfer of structure-borne sound in a vehicle suspension system were developed. The last part was then focussed on the wheel rim influence on the vibro-acoustic behaviour (paper D) of the suspension system. As a whole, the work clearly demonstrates that it is possible to conduct component studies of subsystems in the vehicle suspension system; and from these component studies it is possible draw conclusions that very well may avoid severe degradations in the interior noise of future vehicle generations.
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| 4. |
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| 5. |
- Lindberg, Eskil, et al.
(författare)
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An experimental study of interior vehicle roughness noise from disc brake systems
- 2013
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Ingår i: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 74:3, s. 396-406
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Tidskriftsartikel (refereegranskat)abstract
- An experimental study of the friction-induced noise generated by the disc brake system of a passenger car is presented. In particular, the brake noise usually referred to as wire brush or roughness noise is studied. This is, in terms of frequency spectral content a broadband phenomenon, resulting from the interaction of multiple asperities in the tribological contact. A new experimental method for measurements of disc brake roughness noise is proposed, and is used in a lab environment where the vehicle speed and the brake pressure are accurately controlled. The aim is to study the influence of vehicle speed and brake pressure on the roughness noise inside the vehicle. It is shown for the specific test case that the transmission from the source to the interior is a vibro-acoustic structure-borne phenomenon. Measurements show that there is a, as expected, strong correlation between increased interior noise and both increased vehicle speed and brake pressure.
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| 6. |
- Lindberg, Eskil, et al.
(författare)
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Component mode synthesis using undeformed interface coupling modes to connect soft and stiff substructures
- 2013
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Ingår i: Shock and Vibration. - 1070-9622 .- 1875-9203. ; 20:1, s. 157-170
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Tidskriftsartikel (refereegranskat)abstract
- Classical component mode synthesis methods for reduction are usually limited by the size and compatibility of the coupling interfaces. A component mode synthesis approach with constrained coupling interfaces is presented for vibro-acoustic modelling. The coupling interfaces are constrained to six displacement degrees of freedom. These degrees of freedom represent rigid interface translations and rotations respectively, retaining an undeformed interface shape. This formulation is proposed for structures with coupling between softer and stiffer substructures in which the displacement is chiefly governed by the stiffer substructure. Such may be the case for the rubber-bushing/linking arm assembly in a vehicle suspension system. The presented approach has the potential to significantly reduce the modelling size of such structures, compared with classical component mode synthesis which would be limited by the modelling size of the interfaces. The approach also eliminates problems of nonconforming meshes in the interfaces since only translation directions, rotation axes and the rotation point need to be common for the coupled substructures. Simulation results show that the approach can be used for modelling of systems that resemble a vehicle suspension. It is shown for a test case that adequate engineering accuracy can be achieved when the stiffness properties of the connecting parts are within the expected range of rubber connected to steel.
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| 7. |
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| 8. |
- Lindberg, Eskil, 1979, et al.
(författare)
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Experimental Investigation of Sound Power Radiation From Partly Open Enclosure With Numerous Interior Objects
- 2007
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Ingår i: 19th International Congress on Acoustics, Madrid, 2007.
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Konferensbidrag (refereegranskat)abstract
- The radiated sound power from an engine of a passenger car is highly dependent on the acoustical properties of the engine bay. The engine bay is a densely packed and partly open enclose where standard room acoustics models do not directly apply. It has a complex geometry of numerous accessory parts, cables, pipes, screens, and absorbers that all together affect the wave field and the radiated sound power. Radiated sound power from a simplified hardware model has been measured for various configurations of interior objects. The measurements have been preformed in an anechoic environment using a reciprocal technique where source and receiver positions are interchanged. The results show a clear tendency with higher reduction of the radiated sound power at higher frequencies as the number of objects isincreased. There is a reduction of about 10 dB at higher frequencies when 10% of the empty volume is filled with objects. Screens partly covering openings are needed in the modal range to get a significant reduction. Differences in sound radiation between specific source positions show clear variations. Models combining deterministic and statistical approaches are needed to cover the local behaviour in a wide frequency range.
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| 9. |
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| 10. |
- Lindberg, Eskil, 1979-
(författare)
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Vehicle Disc Brake Roughness Noise : Experimental Study of the Interior Noise andVibro-Acoustic Modelling of Suspension Systems
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Prediction of vehicle disc brake roughness noise is a non-trivial challenge. In fact, neither the source mechanisms, nor the transfer paths are so far well understood. Traditionally, disc brake noise problems are studied as part of the friction-induced noise field, where the source is considered to be a more or less local phenomenon related to the brake disc and brake pad. However, for the roughness noise of interest here this viewpoint is not adequate when attempting to solve the interior noise problem since the transfer of vibro-energy from the brake into the vehicle body is a crucial aspect and plays an important role in the understanding and solution to the problem. The vibroacoustic energy transfer associated with the brake roughness noise is a problem where geometrical complexity and material combinations, including rubber bushings, pose an intricate modelling problem. Additionally, system altering effects from moving parts and loadings are important, e.g. due to the steering or brake systems. In addition, the source mechanisms themselves must also be understood to be able to solve the problem. The current work constitutes a combined experimental and theoretical investigation, aiming at an increased understanding of the source, the transfer paths and how they are a affected by change in the operational state. The experimental study of the vehicle disc brake roughness noise, is based on measurements conducted in a laboratory using a complete passenger car. It is found that the interior noise is a structural-borne broadband noise event well correlated to vehicle speed and brake pressure. The results suggest that the friction source may be divided into vibrations created in the sliding direction and vibrations created normal to the contact plane, where the sliding direction levels appear to be proportional to brake pressure according to Coulomb’s friction law; the vibration level in the normal direction of the contact plane on the other hand has behaviour proportional to Hertz contact theory. The measurements also indicate that the brake force created carried by the suspension system when braking will also alter the vibro-acoustic response of the system. To facilitate the theoretical simulations, an approach for modelling of the suspension system is developed. The vibro-acoustic transfer path model developed is using a modal based on the Craig-Bampton method where a restriction on the coupling modes is suggested. The approach suggested uses undeformed coupling interfaces, to couple structures of fundamentally different stiffness such as may be the case in a vehicle suspension system where for instance rubber bushings are combined with steel linking arms. The approach show great potential inreducing computational cost compared to the classical Craig-Bampton method.
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