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| 2. |
- Cameron, Christopher John, 1980-, et al.
(författare)
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Material Property Steered Structural and Acoustic Optimization of a Multifunctional Vehcile Body Panel
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Conventional vehicle passenger compartments often achieve functional requirements using a complex assembly of components. As each component is optimized for a single task, the assembly as a whole is often suboptimal in achieving the system performance requirements. In this paper, a novel iterative design approach based on using a multi-layered load bearing sandwich panel with integrated acoustic capabilitiesis developed focusing on material properties and their effecton the systems behavior. The proposed panel is meant to fulfilmultiple system functionalities simultaneously, thus simplifying the assembly and reducing mass. Open cell acoustic foams are used to achieve acoustic performance, and the effect of altering the stacking sequence as well as introducing an air gap within the acoustic treatment is studied in detail to determine effects on the acoustic and structural performance of the panel as a whole.
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| 3. |
- Cameron, Christopher J., et al.
(författare)
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On the balancing of structural and acoustic performance of a sandwich panel based on topology, property, and size optimization
- 2014
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 333:13, s. 2677-2698
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Tidskriftsartikel (refereegranskat)abstract
- Balancing structural and acoustic performance of a multi-layered sandwich panel is a formidable undertaking. Frequently the gains achieved in terms of reduced weight, still meeting the structural design requirements, are lost by the changes necessary to regain acceptable acoustic performance. To alleviate this, a design method for a multifunctional load bearing vehicle body panel is proposed which attempts to achieve a balance between structural and acoustic performance. The approach is based on numerical modelling of the structural and acoustic behaviour in a combined topology, size, and property optimization in order to achieve a three dimensional optimal distribution of structural and acoustic foam materials within the bounding surfaces of a sandwich panel. In particular the effects of the coupling between one of the bounding surface face sheets and acoustic foam are examined for its impact on both the structural and acoustic overall performance of the panel. The results suggest a potential in introducing an air gap between the acoustic foam parts and one of the face sheets, provided that the structural design constraints are met without prejudicing the layout of the different foam types.
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| 4. |
- Göransson, Peter, 1959-, et al.
(författare)
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Vibro-acoustic energy propagation in anisotropic, anelastic porous materials
- 2014
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Ingår i: Proceedings of the 9th International Conference on Structural Dynamics, EURODYN 2014. - 9789727521654 ; , s. 83-90
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Konferensbidrag (refereegranskat)abstract
- Historically, the modelling of the acoustics of poro-elastic materials (APEMs) has assumed the materials to be isotropic in both their elastic as well as their acoustic properties including the dissipative mechanisms related to viscous, inertialand thermal interactions. While this is a reasonable approximation when the absorption of sound is of interest, it fails to provide meaningful results for most foamed materials in general and for certain sets of boundary conditions involving elastic contact with solids or other APEMs in particular. A general modelling of fully anisotropic APEMs will be reviewed and taken as a starting point for a series of numerical experiments focussing on aspects of propagation of vibro-acoustic energy, in a homogeneous layer as well as in multiple layer arrangements. From previous works it is known that the influence of anisotropy may be quite significant, in particular for structure-borne vibro-acoustic energy. In addition, it is known that the alignment of principal directions may have substantial influence on the transmission of vibro-acoustic energy. These findings will be recalled in order to prepare for a discussion on the aspects of the directional dependence of the anelastic moduli which will be the core of the presentation at the conference. Real material tensors may be constructed from a superposition of these anisotropic contributions, in the most general case, not necessarily sharing the same principal directions. Starting from these fully anisotropic constitutive tensors with general symmetry properties, studies of optimal alignment between conservative and dissipative tensors, as well as between different materials in various configurations of interest, will be illustrated in the lecture.
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| 5. |
- Lind Nordgren, Eleonora, 1978-
(författare)
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A study of tailoring acoustic porous material properties when designing lightweight multilayered vehicle panels
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present work explores the possibilities of adapting poro-elastic lightweight acoustic materials to specific applications. More explicitly, a design approach is presented where finite element based numerical simulations are combined with optimization techniques to improve the dynamic and acoustic properties of lightweight multilayered panels containing poro-elastic acoustic materials.The numerical models are based on Biot theory which uses equivalent fluid/solid models with macroscopic space averaged material properties to describe the physical behaviour of poro-elastic materials. To systematically identify and compare specific beneficial or unfavourable material properties, the numerical model is connected to a gradient based optimizer. As the macroscopic material parameters used in Biot theory are interrelated, they are not suitable to be used as independent design variables. Instead scaling laws are applied to connect macroscopic material properties to the underlying microscopic geometrical properties that may be altered independently.The design approach is also combined with a structural sandwich panel mass optimization, to examine possible ways to handle the, sometimes contradicting, structural and acoustic demands. By carefully balancing structural and acoustic components, synergetic rather than contradictive effects could be achieved, resulting in multifunctional panels; hopefully making additional acoustic treatment, which may otherwise undo major parts of the weight reduction, redundant.The results indicate a significant potential to improve the dynamic and acoustic properties of multilayered panels with a minimum of added weight and volume. The developed modelling techniques could also be implemented in future computer based design tools for lightweight vehicle panels. This would possibly enable efficient mass reduction while limiting or, perhaps, totally avoiding the negative impact on sound and vibration properties that is, otherwise, a common side effect of reducing weight, thus helping to achieve lighter and more energy efficient vehicles in the future.
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| 6. |
- Lind-Nordgren, Eleonora, et al.
(författare)
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Optimising open porous foam for acoustical and vibrational performance
- 2010
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 329:7, s. 753-767
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Tidskriftsartikel (refereegranskat)abstract
- A computational method for designing optimal arrangements of multilayer noise and vibration treatments in general and porous open cell foam in particular is discussed. The method uses finite element solutions to Biot's equations for poroelastic materials and provides data to evaluate cost functions and gradients. The porous material is parameterised using scaling laws linking the microscopic properties to the classical parameters, i.e. averaged elasticity, flow resistivity and characteristic viscous and thermal lengths. The cost function is either in terms of weight or in terms of the pressure response in a finite cavity, complemented with constraints on the other. However, care must be taken when choosing the cost function, as this will greatly affect the outcome of the optimisation. Observations made during the optimisation process indicate a limited number of minima within the parameter range of interest as well as beneficial continuity around these minima, thus enabling a meaningful optimisation. The results suggest that if alterations of the microscopic properties of the foam are made, the foam may be adapted to specific environmental conditions and thereby achieve improved acoustic behaviour as well as reduced weight.
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| 7. |
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| 8. |
- Lind Nordgren, Eleonora, et al.
(författare)
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Vibroacoustic response sensitivity due to relative alignment of two anisotropic poro-elastic layers
- 2013
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 133:5, s. EL426-EL430
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Tidskriftsartikel (refereegranskat)abstract
- The effects of relative alignment of two different types of anisotropic open cell porous materials are investigated in terms of the acoustic response of a multi-layered configuration. Numerical experiments, where gradient based optimization techniques were used, are conducted to find possible extremal values. It is shown that, depending on the degree of anisotropy of the porous material properties, their angular orientations have a significant and frequency dependent influence on the measured response. The results highlight the importance of further advancing the knowledge of anisotropic porous material behavior.
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