| 1. |
- Andersson, Patrik, 1974, et al.
(författare)
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Framtidsbilder för samhällsbyggnad
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Framtidsbilder för samhällsbyggnad 2020De kommande 15 åren står institutionen för Bygg- och miljöteknik inför stora förändringar. Därför har institutionen initierat projektet Framtidsbilder 2020 där man engagerat en framtidspanel bestående av elva yngre disputerade forskare. Arbetet inleddes med ett breddgruppsmöte där 110 personer representerande institutionens personal och studenter deltog. Vid mötet identifierades ett antal trender och osäkra utvecklingar som påverkar framtiden inom samhällsbyggnadsområdet. Deltagarna bidrog också med idéer till en önskvärd utveckling, vilket har sammanställts och utgör grunden till en gemensam önskvärd framtid/vision för institutionen. Materialet från breddgruppsmötet har bearbetats av Framtidspanelen och resulterat i fyra scenarier som beskriver hur samhällsbyggnadsområdet kan se ut år 2020. Syftet med framtidsbilderna är att de ska vara vägledande för institutionens beslut och förhållningssätt under de kommande åren.Fyra scenarierTurning TorsoSamhället präglas av en ekonomi som är på uppgång, och av ett nytänkande och öppet samhälle. Materiell status och individualism är viktigt. Detta leder till en hög arbetsbelastning samt krav på exklusiva varor av hög kvali-tet. Det finns en stor medvetenhet om miljöpåverkan och klimatförändringar och lösningarna för att klara energiförsörjningen är innovativa.Eco-metropolenDet sveper en grön våg genom dagens samhälle. Under de senaste 15 åren har vi insett att jorden skall vara en bebolig plats även åt dem som kommer efter oss. Vi söker ständigt efter nya, mer förfinade metoder att tillvarata de resurser vi har. Samhället och individen är i balans. Ekonomin är god och vi är miljömedvetna, trygga och integrerade. Nytänkande premieras och icke- materialistiska värderingar står högt i kurs. Vi tänker individuellt, men agerar mer än gärna för kollektivets bästa. Utbildning är gratis TrädgårdsstadenEtt samhälle där vi lärt oss hantera stress, men känner oss otrygga och helst umgås i slutna sociala sammanhang. Vi bor enkelt inne i stan, eller gärna på landsbygden nära storstäderna. Minskade behov av högutbildade i samhället gör att vi har svårt att rekrytera studenter till teknikutbildningar. Det traditionella tankesättet leder till kulturkrockar med företag och personer från andra länder.Gated communitiesFörsämrad ekonomi och ökad egoism har lett fram till ett stressat, otryggt och segregerat samhälle. Accelererande klimatförändringar och ökad miljö-påverkan skrämmer oss, men trots det åtgärdar vi inte problemen, utan koncentrerar oss på konsekvenserna. Arbetslöshet i samhällsbyggnadssek-torn leder till sänkt status för samhällsbyggaren. Vi har därför svårt att rekrytera studenter, och även forskningen har låg status.
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| 2. |
- Ahrens, Jens, 1978, et al.
(författare)
-
Tutorial on scaling of the discrete fourier transform and the implied physical units of the spectra of time-discrete signals
- 2020
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Ingår i: 148th Audio Engineering Society International Convention.
-
Konferensbidrag (refereegranskat)abstract
- The combination of the time-discrete property of digital signals together with the commonly employed definition of the discrete Fourier transform (DFT) can cause ambiguity when interpreting magnitude spectra with respect to the physical unit of the signal under consideration. Standardized scaling of spectra increases the comparability of frequency-domain data that are published in scientific articles or data sheets of commercial products. We present and discuss in this tutorial a collection of the most relevant scaling options for DFT spectra to yield amplitude spectra, power spectra, and power density spectra, and we illustrate how an implied physical unit of the underlying signal is reflected by the magnitude of the spectrum. The tutorial is accompanied by Matlab/Octave scripts that demonstrate the different cases.
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| 3. |
- Almefelt, Lars, 1968, et al.
(författare)
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Exploring Requirements Management in the Automotive Industry
- 2003
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Ingår i: 14th International Conference on Engineering Design Research for Practice - innovative products, processes and organisations.
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Konferensbidrag (refereegranskat)abstract
- This paper presents an empirical study carried out in the automotive industry, with the aim to bring forward new experiences and knowledge on management of requirements in practice. Adopting a qualitative systems approach, and using multiple information sources, the requirements management process during the development of a passenger car cockpit has been mapped out. The logical reconstruction of the requirements management process is complemented with descriptions of associated phenomena, such as important events and attitudes. Findings are presented, analysed and discussed considering also factors underlying observed phenomena.
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| 4. |
- Andersson, Fredrik, 1974, et al.
(författare)
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Computer Based Requirements and Concept Modelling - Information Gathering and Classification
- 2000
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Ingår i: 12th International Conference on Design Theory and Methodology. 2000 ASME International Design Engineering Technical Conferences.
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a requirement and concept model based on a functional decomposition of mechanical systems. It is an object-oriented approach to integrate the representation of the design artefact and the design activity, through the decisions made during the design evolution. The requirements co-evolve simultaneously with the formation of the conceptual layout, through the opportunity to alter between function and physical/abstract solutions. This approach structures the design requirements and concepts in such a way that it supports the ability to document their sources, to allow for validation and verifications of both requirements and design solutions. First, the proposed model is presented from a theoretical viewpoint. Secondly, a methodology for modelling requirements and concepts in an object-oriented fashion is discussed. Finally, the model is implemented in METIS software and tested in a case study of an electric window winder on a truck door.
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| 5. |
- Andersson, Martin, 1974, et al.
(författare)
-
Vesicle and bilayer formation of diphytanoylphosphatidylcholine (DPhPC) and diphytanoylphosphatidylethanolamine (DPhPE) mixtures and their bilayers' electrical stability
- 2011
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Ingår i: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 82:2, s. 550-561
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Tidskriftsartikel (refereegranskat)abstract
- Lipid bilayers are of interest in applications where a cell membrane mimicking environment is desired. The performance of the lipid bilayer is largely dependent on the physical and chemical properties of the component lipids. Lipid bilayers consisting of phytanoyl lipids have proven to be appropriate choices since they exhibit high mechanical and chemical stability. In addition, such bilayers have high electrical resistances. Two different phytanoyl lipids, 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) and 1,2-diphytanoyl-sn-glycero-3-phosphoethanolamine(DPhPE), and various combinations of the two have been investigated with respect to their behavior in aqueous solutions, their interactions with solid surfaces, and their electrical stability. Dynamic light scattering, nuclear magnetic resonance diffusion, and cryogenic transmission electron microscopy measurements showed that pure DPhPC as well as mixtures of DPhPC and DPhPE consisting of greater than 50% (mol%) DPhPC formed unilamellar vesicles. If the total lipid concentration was greater than 0.15 g/l, then the vesicles formed solid-supported bilayers on plasma-treated gold and silica surfaces by the process of spontaneous vesicle adsorption and rupture, as determined by quartz crystal microbalance with dissipation monitoring and atomic force microscopy. The solid-supported bilayers exhibited a high degree of viscoelasticity, probably an effect of relatively high amounts of imbibed water or incomplete vesicle fusion. Lipid compositions consisting of greater than 50% DPhPE formed small flower-like vesicular structures along with discrete liquid crystalline structures, as evidenced by cryogenic transmission electron microscopy. Furthermore, electrophysiology measurements were performed on bilayers using the tip-dip methodology and the bilayers' capacity to retain its electrical resistance towards an applied potential across the bilayer was evaluated as a function of lipid composition. It was shown that the lipid ratio significantly affected the bilayer's electrical stability, with pure DPhPE having the highest stability followed by 3DPhPC:7DPhPE and 7DPhPC:3DPhPE in decreasing order. The bilayer consisting of 5DPhPC:5DPhPE had the lowest stability towards the applied electrical potential.
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| 6. |
- Andersson, Patrik, 1974
(författare)
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A contact model for predicting adherence force and noise generation in the tyre / road contact
- 2005
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Ingår i: Proceedings of NOVEM (Noise and Vibration: Emerging Methods), Saint-Raphaël, France.
-
Konferensbidrag (refereegranskat)abstract
- Adhesion forces influence the automotive tyre / road surface contact for certain tyre / road combinations, leading to enhanced rolling resistance, tyre vibrations, and noise excitation. A model was developed to predict the contact force and noise generation for hastily separation of two macroscopic objects. The model is formulated in the time domain for two elastic bodies in non-linear dynamic contact. The contact area is spatially discretised in contact points and the dynamic response is calculated convolving the contact forces with pre-calculated impulse responses of the interacting objects. The adhesion forces are included allowing negative forces through the contacts, which break at a given condition; at a critical force in its simplest form. Parameters on a micro-scale influencing this condition are discussed. Time records of contact forces and sound pressures as samples of tyre tread are hastily separated from road surfaces samples were acquired. A qualitative comparison between calculated and measured data demonstrates the feasibility of the model.
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| 7. |
- Andersson, Patrik, 1974, et al.
(författare)
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A Method for Experimental Collection of Global Material Data for Tyres
- 2001
-
Ingår i: Nordic Vibration Research 2001, Stockholm, Sweden (The Scandianvian Vibration Society, www.svib.se).
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- For the modelling of the dynamic behaviour of tyres material data are required. Depending on the character of the model these will have different quality. Modelling with global structures such as beams or plates, representative data for the global bending stiffness, global mass etc. are needed. These data do not represent the details of the tyre structure but the combined properties of the structure. Therefore it is not possible to cut out samples of the tyre and determine the global material properties by measurements on these samples. Consequently it is necessary to estimate the material parameter by measurements carried out on the complete tyre. Results from such measurements will be related to the model used for the tyre (e.g. ring model, orthotropic plate, etc.). The material data obtained in such way are consequently a function of both the tyre structure and the model, which is used to update the data. A method for experimental collection of global material data for tyres has been developed. This method is based on the experimental characterisation of tyres by driving point and transfer mobilities and the use of the orthotropic plate tyre model for updating the material data.
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| 8. |
- Andersson, Patrik, 1974, et al.
(författare)
-
A study of forces and noise generation in a contact including adhesive bonds
- 2004
-
Ingår i: Nordic Vibration Research 2004, June 3-4, (The Scandinavian Vibration Society, www.svib.se).
-
Konferensbidrag (refereegranskat)abstract
- Paper to be published.Adhesive forces are present in the contact between a road surface and a rolling tyre. Theses forces may add up to substantial adherence forces, causing stick-snap excitation of tread blocks, high frequency noise generation, and increased rolling resistance. An experimental setup was designed to study the process when a tyre tread block sample was pressed onto a road surface sample, and hastily removed. Time variation of contact forces and sound pressure were measured. The same situation was modelled using a time domain model of two elastic bodies in non-linear dynamic contact. The contact area is spatially discretised in contact points and the contact problem is solved using an elastic half-space. The response of the block is calculated by convoluting the forces with pre-calculated impulse responses of the same block, which is modelled as a mass-spring system. The adhesive bounds are included by allowing negative contact forces; the contact at a point breaks when the calculated contact force reaches a specified negative value. Typical results from the experimental setup and the model are presented. It is concluded that the experimental setup is suitable for investigating the detachment process of the tread block and that the model is able to qualitatively capture the contact force and noise generation.
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| 9. |
- Andersson, Patrik, 1974
(författare)
-
Boundary element formulation using modified Green's functions for media with random distribution of scattering objects
- 2009
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Ingår i: Proceedings of NOVEM 2009 Noise and Vibration: Emerging Methods, Oxford, UK.
-
Konferensbidrag (refereegranskat)abstract
- The engine bay of an automotive vehicle is a partly open enclosure that is densely filled with numerous objects such as accessory parts, pipes, tubes, and cables. These objects cause scattering of the sound waves inside the engine bay, which leads to an increased absorption of sound power compared to an enclosure without objects. However, it is time-consuming to include all the details of the geometry and acoustical properties of the objects in numerical simulations, predicting the sound power radiated to the exterior. This paper presents how a deterministic boundary element model and a statistical intensity/power model can be combined to give an approximate description of the sound field for cases with randomly distributed scatterers. The boundary element formulation describes the coherent part of the wave field by using modified Green's functions that include the average effect of the scattering objects. The waves scattered at the objects are assumed to result in an incoherent field that is described by an intensity model. The modelling approach is evaluated by calculating the power radiated from a partly open enclosure in a two-dimensional geometry. The results are convincing and it is concluded that the approach is suitable.
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| 10. |
- Andersson, Patrik, 1974, et al.
(författare)
-
Boundary Element Method for Intensity Potential Approach : Predicting the Radiated Sound Power from Partially Enclosed Noise Sources
- 2012
-
Ingår i: Acta Acoustica united with Acustica. - : S. Hirzel Verlag. - 1610-1928 .- 1861-9959. ; 98:4, s. 588-599
-
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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| 11. |
- Andersson, Patrik, 1974
(författare)
-
Contact forces and noise generation during hastily separation of tyre tread blocks from road surfaces
- 2005
-
Ingår i: Constitutive Models for Rubber IV — Austrell and Kari (eds). - 0415383463 ; , s. 571-577
-
Konferensbidrag (refereegranskat)abstract
- Adhesive bonds in the passenger car tyre/road surface contact have a large influence on the contact dynamics for certain tyre/road combinations. The effect is most pronounced for road surfaces with low roughness, so-called smooth surfaces. An experimental setup was designed to study time records of contact forces and sound pressures as tyre tread samples are hastily separated from road surfaces samples. The general character of the separation process on a macroscopic length scale is described, interpreted, and related to theories on smaller scales. A single value (dynamic) adherence force is determined out of the records and it is related to the initial conditions; magnitude of preload, preload duration, and unloading rate. It was found that the exact contact geometry, on larger scales, yields the details in the contact force record and distribution of sound pressure levels in 1/3-octave bands. A model aiming at describing the observed behaviour must consider a wide range of length scales; a dynamic contact model is proposed that considers the exact contact geometry on larger scales via discretisation and uses statistical properties of the surfaces at lower scales to determine contact criteria at contact points.
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| 12. |
- Andersson, Patrik, 1974, et al.
(författare)
-
Experimental Study of High Frequency Response of Tyres
- 2003
-
Ingår i: EuroNoise2003, May 19-21 2003, Naples, Italy.
-
Konferensbidrag (refereegranskat)abstract
- Most traditional tyre models concern the low and middle frequency ranges. It is necessary to include higher frequencies for improved accuracy in tyre/road interaction models. Often only the radial direction is included, although the tangential direction may be important, especially studying stick slip motion in the contact between tyre and road surface. Designing models requires insight into the behaviour of the tyre structure at higher frequencies. To add insight of high frequency behaviour, experimental studies were done on four different tyres with the same internal design but with different tread patterns. The results of this study underline the importance of the local deformation when forces act with small excitation areas on the tread. Adequate consideration of the tread properties in the tyre/road interaction models is thus of importance to obtain the correct local contact force distribution. This is most important for the tangential driving point mobility. Tread patterns are shown mainly to modify the flexural stiffness and mass in comparison to smooth tyres, while block resonances are not expected to be located in the frequency range in which tyre/road noise is important.
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| 13. |
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| 14. |
- Andersson, Patrik, 1974, et al.
(författare)
-
High Frequency Dynamic Behaviour of Smooth and Patterned Passenger Car Tyres
- 2004
-
Ingår i: Acta Acustica united with Acustica. - 1610-1928 .- 1861-9959. ; 90:3, s. 445-456
-
Tidskriftsartikel (refereegranskat)abstract
- Most traditional tyre models concern the low and middle frequency ranges. For improved accuracy in tyre/roadinteraction models it is necessary to include higher frequencies. Often only the radial direction is included, althoughthe tangential direction may be important, especially studying stick slip motion in the contact between tyreand road surface. Designing accurate and efifcient models requires insight into the behaviour of the tyre structureat higher frequencies to make the models as complete as necessary without creating tools that are computationallytoo costly. To add insight to this area, experimental studies were done on four different tyres with the sameinternal design but with different tread patterns. Point mobilities were measured and compared with two differenttyre models, a two-layer plate model based on the elastic field equations and an orthotropic plate model. Theresults of this study underline the importance of the local deformation when there are forces that act with smallexcitation areas on the tread. Adequate consideration of the tread properties in the tyre/road interaction modelsis thus of extreme importance to obtain the correct local contact force distribution. This is most important for thetangential driving point mobility. Tread patterns are shown mainly to modify the flexural stiffness in comparisonto smooth tyres, while block resonances are not expected to be located in the frequency range in which tyre/roadnoise is important.
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| 15. |
- Andersson, Patrik, 1974
(författare)
-
High Frequency Tyre Vibrations
- 2002
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High frequency (above 1 kHz) noise generation from the tyre/road interaction is still not fully understood and accurately modelled.Two noise generation mechanisms previously suggested in the literature are reviewed: air pumping and noise generation cased by adhesive effects between the tyre tread and road surface. These mechanisms are located in and near the tyre/road contact zone, and a deterministic description of these mechanisms requires a tyre model that is able to describe the high frequency behaviour of the tyre, including local deformation in both the radial and tangential directions. A three-dimensional two-layer plate tyre model based on the elastic field equations is suggested as a model that would fulfil these requirements. This model was developed earlier [1], and is now extended to allow for comparison to mobility measurements on real tyres. The overall agreement between the model and measurements is surprisingly good in view of the simplicity of the model. However, some limitations of the model are also presented.The tyre model is used in two investigations focusing on the dynamic behaviour of tyres in both the radial and tangential directions in the frequency range from 50 Hz to 4 kHz; (i) investigation of the dynamic behaviour of smooth and patterned tyres at high frequencies for both radial and tangential directions, and (ii) a parameter study investigating the relation between internal tyre parameters and the response at the outermost surface. It was found that the radial point mobility is greatly influenced by properties of the local deformation at high frequencies and/or small excitation areas. The tangential point mobility is affected by local deformation in almost the whole frequency range. Hence, it is mainly the properties of the tread cap and the pattern that determine the response at high frequencies and in the tangential direction. The radial response is determined by the combined properties of the belt and the tread cap at medium frequencies, while it is the dimension and the pre-tension in the plies that determines the low frequency response.
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| 16. |
- Andersson, Patrik, 1974, et al.
(författare)
-
Investigation of Driving Point and Transfer Mobilities of Simple Tread Blocks on a Tyre
- 2001
-
Ingår i: 17th International Congress on Acoustics, Rome, Italy, 2001.
-
Konferensbidrag (refereegranskat)abstract
- An important issue when modeling noise generation from rolling tyres using the orthotropic plate tyre model [1] is to find accurate Green’s functions for the responses of the tyre. These Green’s functions are used to solve the tyre/road contact problem of the rolling tyre in the time domain. For tyres with tread blocks, it is important to consider the influence of the tread blocks on the response. It has previous been suggested that the tread blocks could be modeled as mass-spring systems [2]. Measurements of mobilies on a tyre with simple and regular tread blocks shows that this approach is unnecessary when modelling the response in radial direction of the tyre in the frequency range between 0 and 2500 Hz. Instead the tyre may be modeled, using a plate tyre model, as a soft plate with slightly higher local deformation. The tread pattern may be modeled in the tyre/road contact model as a macro roughness, where points at the blocks may be in contact with the road while forces at points in the groves are set to zero.
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| 17. |
- Andersson, Patrik, 1974
(författare)
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Modelling Effects due to Small-Scale Roughness in Tyre/Road Contact
- 2006
-
Ingår i: Proceedings of EuroNoise 2006, 30 May - 1 June, 2006.
-
Konferensbidrag (refereegranskat)abstract
- The interaction process between a rolling automotive vehicle tyre and a road is influenced by the geometry of the interacting bodies on a wide range of length scales down to the micrometer length-scale. The smaller length-scales determines the details of pressure and strain distributions in the contact, that in turn affects rolling resistance, noise generation, wear, and grip. These small scales also determine, via the area of real contact, the non-linear contact stiffness and the adherence forces between the two surfaces. These two effects have been included in a tread block / road surface contact model, which is based on spatial discretisation of the contact geometry. The model is formulated in the time domain and the dynamic response is calculated convolving contact forces with pre-calculated impulse responses of the interacting objects. The effects due to roughness on length scales smaller than the dimensions of contact elements are included by non-linear relations between force and separation distance for each pair of contact elements. Comparison with results from a standard Lagrange contact formulation reveals the importance of including also the smaller length-scales.
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| 18. |
- Andersson, Patrik, 1974
(författare)
-
Modelling Interfacial Details in Tyre/Road Contact — Adhesion Forces and Non-Linear Contact Stiffness
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Rolling resistance, noise generation, and wear are all determined by the interaction process between the rolling automotive vehicle tyre and the road. A deep understandingof the interaction process is needed for optimisation aiming at reducing these effects. Details in the tyre/road contact interface are considered in the presented work; non-linear contact stiffness and adherence forces at the interface areinvestigated and modelled. A description of the tyre structure and especially its tread layer is required for contact modelling. The dynamic responses of smooth and patterned passenger-car tyres are experimentally investigated. Experimental results are used to validate a high-frequency tyre model based on the elastic field equations, which includes the local deformation of the tread. The separation process when tyre tread blocks are rapidly separated from road surfaces is investigated in an experiment. This process is described with the aid ofthe total contact force and noise generation. Based on the experimental results, a model for the adherence force as a function of load, load duration, and unloading rate is proposed.Optimisation of the tyre/road interaction including interfacial details requires time-domain contact models including a wide range of length-scales. The strategyis to divide the contact problem into different ranges of length-scales. A model based on statistical description of the contact geometry is used on the smallest length-scales. A tread block in contact with the road surface is modelled on intermediate length-scales, and on the largest length-scales is a contact model of the complete tyre structure rolling over the road surface. The two latter models use a numerical time-domain contact formulation with a discretised contact geometry. These three models are connected via constitutive relations between contact pressure and relative displacements, incorporated as non-linear springs between the contact elements. The modelling approach is still under development but preliminary results are presented.
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| 19. |
- Andersson, Patrik, 1974
(författare)
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Modelling Non-Linear Contact Stiffness in Tyre/Road Contact
- 2007
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Ingår i: 19th International Congress on Acoustics, Madrid, 2007.
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Konferensbidrag (refereegranskat)abstract
- Noise generation, rolling resistance, wear, and grip are determined by the tyre/road interaction. The small-scale surface geometry gives an area of real contact that increases with load over the interface leading to a non-linear relation between load and indentation depth for the interacting objects. The small length-scales of the contact geometry have traditionally been neglected in numerical tyre/road interaction models. This paper presents a step towards refinement of an existing tyre/road noise model by considering the small-scale geometry via a thin interfacial layer. A model for calculating the interfacial stiffness from road surface geometry and tread stiffness data is proposed. The interfacial stiffness is incorporated as non-linear springs in a numerical contact model based on a spatial discretisation of the contact geometry. Results of load-indentation relations and contact stiffness are presented for a single tread block in contact with a road surface. The results show that the contact stiffness of a tread block is substantially lower than the stiffness given by the bulk modulus of the objects. The contact stiffness varies substantially for typical variations in load and indentation depths that appear in the tyre/road contact.
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| 20. |
- Andersson, Patrik, 1974, et al.
(författare)
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Numerical Modelling of Tyre/Road Interaction
- 2012
-
Ingår i: Scientific Bulletin, Automotive Series. - 1453-1100. ; 22
-
Tidskriftsartikel (refereegranskat)abstract
- From November 2012 all passenger car tyres, light truck tyres and heavy duty vehicle tyres sold on the aftermarket in the European Union must have a label classifying the external rolling noise, the fuel efficiency, and the wet grip. This regulation puts a focus on optimisation of the tyre design with respect to all these parameters at once. Up to today these three parameters have been treated rather independently. There is little to no detailed information available on the relationship between rolling noise generation, rolling resistance, and grip of car tyres besides empirical data based on measurements. Today, simulation models that can simulate all these effects at once have just started to emerge. This paper gives a brief presentation of the past and the most resent development of numerical tyre/road interaction models with focus on external noise, rolling resistance, and grip. Today, the simulation models can be used to gain fundamental knowledge about the tyre/road interaction process and the resulting noise, rolling resistance, and grip. Models for combined optimisation of rolling resistance and noise emissions exists, and are just about to be used in preliminary investigations. Models that in addition give results for grip are still under development.
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| 21. |
- Andersson, Patrik, 1974, et al.
(författare)
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Numerical Modelling of Tyre/Road Interaction
- 2011
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Ingår i: Exploratory Workshop: Modern Methods of Vibro-Acoustic Studies With Automotive Applications, University of Pitesti, Romania, November 24-25, 2011.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- From November 2012 all passenger car tyres, light truck tyres and heavy duty vehicle tyres sold on the aftermarket in the European Union must have a label classifying the external rolling noise, the fuel efficiency, and the wet grip. This regulation puts a focus on optimisation of the tyre de- sign with respect to all these parameters at once. Up to today these three parameters have been treated rather independently. There is little to no detailed information available on the relationship between rolling noise generation, rolling resistance, and grip of car tyres besides empirical data based on measurements. Today, simulation models that can simulate all these effects at once have just started to emerge. This paper gives a brief presentation of the past and the most resent develop- ment of numerical tyre/road interaction models with focus on external noise, rolling resistance, and grip. Today, the simulation models can be used to gain fundamental knowledge about the tyre/road interaction process and the resulting noise, rolling resistance, and grip. Models for combined opti- misation of rolling resistance and noise emissions exists, and are just about to be used in preliminary investigations. Models that in addition give results for grip are still under development.
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| 22. |
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| 23. |
- Andersson, Patrik, 1974
(författare)
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Predicting sound power radiated from engine bays using decomposition of the vector field of sound intensity
- 2011
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Ingår i: Svenska Mekanikdagar, 13-15 Juni 2011, Chalmers tekniska högskola, Göteborg.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Encapsulation of fans, engines and machinery is a standard noise-control treatment. The encapsulations have generally large apertures to allow for airflow cooling. They form partial enclosures with coupling between the complex interior wave field and exterior radiation in an unbounded domain. A typical encapsulation is an engine bay where geometry, position and acoustical properties of screens and absorbers are used to control the radiated noise. The mid- and high-frequency range is often of interest, i.e.~frequencies for which the wavelength is on the order of or smaller than geometrical details. A method suitable for this kind of problem is the intensity potential appraoch. The intensity potential approach is based on the Helmholtz decomposition of the vector field of time-averaged sound intensity into its irrotational and rotational components. The local power balance in a lossless medium is expressed in terms of the irrotational component only, and results in the Poisson equation for a scalar intensity potential of this component only. It captures the power flow from sources to the surroundings by considering the part of the intensity field that is related to flow of energy. A strength of the method is that no additional assumptions have to be made apart from what is behind the local power balance; it follows directly from the Helmholtz decomposition of the active intensity. Further, it does not violate the geometrical divergence of energy in free-field as the classical equation of acoustical diffusion. It is therefore suitable for cases where a partial enclosed volume has strong coupling to an exterior unbounded domain.The physical and theoretical background of the method is presented together with evaluations by comparison to experimental data. The comparison to experimental data shows that the method is useful in practical applications. The approach provides a robust prediction tool that has its strength at high frequencies for cases with complex geometry and multiple broadband sources.
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| 24. |
- Andersson, Patrik, 1974, et al.
(författare)
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Rapid tyre/road separation: An experimental study of adherence forces and noise generation
- 2009
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 266:1-2, s. 129-138
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Tidskriftsartikel (refereegranskat)abstract
- Adhesion forces in the tyre/road contact interface significantly influence the contact dynamics and resulting noise generation for certain tyre/road combinations. Hence, an experimental setup was built where tyre tread samples are loaded and rapidly unloaded in the direction normal to a wearing course sample from an ISO10844-road. Time records of contact forces and sound pressures are acquired during the separation. The separation process in terms of the contact forces and noise generation is described and interpreted. There is good repeatability in the general character of the time signals for a given geometry, but variations occur requiring statistical analysis, as the initial conditions (on smaller length scales) are only approximately repeated. The measured adherence force depends strongly on load, load duration, and unloading rate, in a way supported by theories for contact of rough surfaces. The total sound pressure level of the noise generated during separation is directly related to the level of the adherence force, but the distribution of energy in 1/3-octave bands cannot be estimated from the adherence force record alone, as they also depend on the exact contact geometry. The details of the contact geometry are also very decisive for the magnitude of the adherence force.
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| 25. |
- Andersson, Patrik, 1974
(författare)
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Solving the intensity potential problem by using the boundary element method
- 2010
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Ingår i: Proceedings of InterNoise2010, 13-16 June 2010, Lisbon, Portugal.
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Konferensbidrag (refereegranskat)abstract
- Robust tools for prediction of radiated sound power in the high-frequency range from encapsulated sources are of interest in machinery and vehicle noise control. These encapsulations form partial enclosures yielding exterior problems that may be solve by using the intensity potential approach. The intensity potential approach is briefly presented and the boundary element method to solve the resulting Poisson equation with appropriate boundary conditions is discussed in detail. The boundary element method is a suitable solution strategy since only surfaces of objects has to be discretised and the boundary condition at infinity is exactly fulfilled. Results in 1/3-octave bands show that the method is very applicable for estimation of the global radiated sound power in one-third-octave bands in the high-frequency range, but that the directivity of the radiation pattern is underestimated.
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