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DEMEASS IV, March 26-30 2011<br />Urspelt (Luxemburg)<br />Progresses on the vibro-acoustic design of a class of aluminium...
Outline<br /><ul><li>Synopsis
References
DEMEASS III: A Review
ECOCELL Core
Investigated Configurations
Numerical Results
Experimental Tests
Conclusions and Future Work</li></ul>Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />...
Synopsis<br /><ul><li>Sandwich panels are widely used in engineering application because of the extremely high stiffness-t...
A new concept of sandwich plate (all aluminum based) was tested in order to get the typical results available with more co...
This work is the straight  continuation of the work presented in the last DEMEASS.
Activities herein presented will be continued and extended under the project SUPERPANELS (www.superpanels.unina.it).</li><...
References<br />Kurtze and Watters (1959) studied the application of sandwich panels to increase the sound insulation betw...
DEMEASS III: A Review <br />Sandwich panel with truss-core<br />18128 and 23664 rodsalong the X and Z axes, respectively<b...
DEMEASS III – A Review<br />@ 740 Hz<br />Optimized resin<br />Optimized+Randomized resin<br />Progresses on the vibro-aco...
ECOCELL Core: Concept<br />Stereolithography is a costly and complicated procedure.<br />Need for both simplified plates a...
ECOCELL Core: Concept – Basic Unit<br />Equivalent COreCELL: <br />an aluminium (plate-like) basic element able to reprodu...
ECOCELL Core: Global view<br />Truss-like core<br />16 stiffeners along x-axis<br />11 stiffeners along z-axis<br />Progre...
ECOCELL Core: Global view of the sandwich<br />Basic Sandwich Panel Configuration<br />Lx=0.640 m, Lz=0.420 m<br />FE mesh...
Vibro-acoustic Indicators<br />Continuos<br />Discrete<br />v(ω) is the velocity vector<br />R(ω) is the radiation resista...
Investigated Configurations<br />Coding: CODE_THmm<br />Progresses on the vibro-acoustic design of a class of aluminium sa...
Numerical Results (cont’d)<br />Influence of CoreConfiguration<br />106<br />Base_1mm<br />D_1mm<br />E_1mm<br />105<br />...
Numerical Results (cont’d)<br />Influence of CoreConfiguration<br />80<br />Base_1mm<br />D_1mm<br />E_1mm<br />70<br />C_...
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Demeass Iv D Alessandro

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  1. 1. DEMEASS IV, March 26-30 2011<br />Urspelt (Luxemburg)<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />Vincenzo D’Alessandro, Francesco Franco,<br />Sergio De Rosa, TizianoPolito<br />ælab‐Vibrations and AcousticsLaboratory<br />Departmentof AerospaceEngineering<br />Università degli Studi di Napoli “Federico II” <br />Via Claudio 21, 80125, Napoli, Italy<br />www.dias.unina.it<br />
  2. 2. Outline<br /><ul><li>Synopsis
  3. 3. References
  4. 4. DEMEASS III: A Review
  5. 5. ECOCELL Core
  6. 6. Investigated Configurations
  7. 7. Numerical Results
  8. 8. Experimental Tests
  9. 9. Conclusions and Future Work</li></ul>Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />2<br />
  10. 10. Synopsis<br /><ul><li>Sandwich panels are widely used in engineering application because of the extremely high stiffness-to-mass ratio. The design flexibility associated with such composite structures provides significant opportunities for tailoring the structure to the load and dynamic response requirements.
  11. 11. A new concept of sandwich plate (all aluminum based) was tested in order to get the typical results available with more complicated configurations.
  12. 12. This work is the straight continuation of the work presented in the last DEMEASS.
  13. 13. Activities herein presented will be continued and extended under the project SUPERPANELS (www.superpanels.unina.it).</li></ul>Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />3<br />
  14. 14. References<br />Kurtze and Watters (1959) studied the application of sandwich panels to increase the sound insulation between adjoining spaces. They investigated the relation between bending and shear waves and TL characteristics. <br />Lang and Dym(1975) optimized the design of a sandwich panel with the goal to exceed the TL values predicted by the mass law by at least 20 dB in a selected frequency range. <br />Barton and Grosveld(1981) considered an aeronautical application of honeycomb panels to improve sidewall attenuation in a light twin-engine. <br />Thamburaj and Sun (2002) demonstrated that an anisotropic core can lead to higher TL and that the proper design of face sheet thickness can further improve the performance. <br />NASA tests (2002) about the performance of sandwich structures with a core made of a lattice of truss elements are available.<br />Cunefare et al. (2003) gave additional indication that structural acoustic optimization has the potential to achieve significant gains to reduce interior noise levels in aerospace structures.<br />Franco et al. (2007) analyzed the optimization of the structural-acoustic characteristics of various and innovative sandwich configurations. They considered different core configurations, and those having a truss geometry have been very promising configurations, since it is possible control the stiffness along the two direction in-plane of the panel.<br />Franco, De Rosa and Polito(2010) demonstrated that the vibro-acoustic responses can improve if a random stiffness is imposed over an optimized configuration, highlighting that randomization represents a very cheap simulation step. <br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />4<br />
  15. 15. DEMEASS III: A Review <br />Sandwich panel with truss-core<br />18128 and 23664 rodsalong the X and Z axes, respectively<br />Effect of a randomization of the stiffness properties on the optimized configuration has been analyzed.<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />5<br />
  16. 16. DEMEASS III – A Review<br />@ 740 Hz<br />Optimized resin<br />Optimized+Randomized resin<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />6<br />
  17. 17. ECOCELL Core: Concept<br />Stereolithography is a costly and complicated procedure.<br />Need for both simplified plates and related models able to take into account the peculiarities of the configurations and results of the sandwich plate with resin core.<br />Thinking to <br /> the LEGO© elementary brick concept and <br /> classical carton filler for packaging . . . . <br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />7<br />
  18. 18. ECOCELL Core: Concept – Basic Unit<br />Equivalent COreCELL: <br />an aluminium (plate-like) basic element able to reproduce the complexity of the resin core cells.<br />Core modular element (dimensions in mm)<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />8<br />
  19. 19. ECOCELL Core: Global view<br />Truss-like core<br />16 stiffeners along x-axis<br />11 stiffeners along z-axis<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />9<br />
  20. 20. ECOCELL Core: Global view of the sandwich<br />Basic Sandwich Panel Configuration<br />Lx=0.640 m, Lz=0.420 m<br />FE mesh: 10965 grid points<br /> 10752 four-point plate element. <br />2 m<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />10<br />
  21. 21. Vibro-acoustic Indicators<br />Continuos<br />Discrete<br />v(ω) is the velocity vector<br />R(ω) is the radiation resistance matrix <br />Ais the nodal equivalent areas matrix<br />Thus, it is possible, on the base of the results achieved from a frequency response analysis of the finite element model of a generic plane structure, to calculate the radiated acoustic power.<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />11<br />
  22. 22. Investigated Configurations<br />Coding: CODE_THmm<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />12<br />
  23. 23. Numerical Results (cont’d)<br />Influence of CoreConfiguration<br />106<br />Base_1mm<br />D_1mm<br />E_1mm<br />105<br />C_1mm<br />104<br />V2MS [m2/s2]<br />103<br />102<br />101<br />01000 2000300040005000<br />Frequency [Hz]<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />13<br />
  24. 24. Numerical Results (cont’d)<br />Influence of CoreConfiguration<br />80<br />Base_1mm<br />D_1mm<br />E_1mm<br />70<br />C_1mm<br />dB<br />60<br />50<br />40<br />C_1mm configuration<br />30<br />01000 2000300040005000<br />Frequency [Hz]<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />14<br />
  25. 25. Numerical Results (cont’d)<br />Influence of Face-Sheet Thickness <br />80<br />Base_1mm<br />Base_2mm<br />Base_3mm<br />70<br />dB<br />60<br />50<br />40<br />30<br />01000 2000300040005000<br />Frequency [Hz]<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />15<br />
  26. 26. Numerical Results (cont’d)<br />Randomness of the Core Stiffness (1/4) <br />It was investigated the effect of the addition of a random distribution of the core stiffness. The random distributions were based on two (uncoupled) Gaussian functions.<br />106<br />Base_1mm<br />sr = 40%<br />sr = 60%<br />105<br />sr = 70%<br />104<br />V2MS [m2/s2]<br />103<br />102<br />sr = 70%<br />101<br />01000 2000300040005000<br />Frequency [Hz]<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />16<br />
  27. 27. Numerical Results (cont’d)<br />Randomness of the Core Stiffness (2/4) <br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />17<br />
  28. 28. Numerical Results (cont’d)<br />Randomness of the Core Stiffness (3/4) <br />106<br />C_1mm<br />C7_1mm<br />C1_1mm<br />C2_1mm<br />105<br />C3_1mm<br />C4_1mm<br />C5_1mm<br />C6_1mm<br />104<br />C7_1mm<br />V2MS [m2/s2]<br />103<br />102<br />101<br />01000 2000300040005000<br />Frequency [Hz]<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />18<br />
  29. 29. Numerical Results (cont’d)<br />Randomness of the Core Stiffness (4/4) <br />106<br />80<br />C_1mm<br />C1_1mm<br />C2_1mm<br />70<br />C3_1mm<br />C4_1mm<br />C5_1mm<br />60<br />C6_1mm<br />dB<br />C7_1mm<br />50<br />40<br />30<br />20<br />01000 2000300040005000<br />Frequency [Hz]<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />19<br />
  30. 30. Numerical Results (cont’d)<br />Optimization of the ECOCELL Core (1/2)<br /><ul><li>NX NASTRAN optimizer (SOL 200) - Modified Method of Feasible Directions
  31. 31. Twenty-seven design variables: thickness of the stiffeners
  32. 32. Constraint: weight of the core, i.e. the thickness of the stiffeners are explicitly linked because is imposed a constraint on their variations so as to keep the core weight less or equal to the value of the initial configuration
  33. 33. Objective Functions: the simplest objective function is the average of the square structural velocity on the radiating face sheet and over the chosen frequency range
  34. 34. NG = number of discrete sample points on the face of the panel
  35. 35. NF = number of frequency sample points</li></ul>Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />20<br />
  36. 36. Numerical Results (cont’d)<br />Optimization of the ECOCELL Core (2/2)<br />104<br />C7_1mm<br />Optimizerconfiguration<br />103<br />V2MS [m2/s2]<br />102<br />101<br />1800 200022002400<br />Frequency [Hz]<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />21<br />
  37. 37. Experimental Tests – The 1st prototype<br />Manufacturing Problems<br />ECOCELL core in steel instead of aluminum alloy<br />Face sheet 3 mm thick and grooved in correspondence of the stiffeners positions to facilitate their installation<br />Pods filled with epoxy glue<br />There is contact in the intersection of stiffeners!<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />22<br />
  38. 38. Experimental Tests – The 1st prototype<br />Modal analysis – Impact testing by using LMS TESTLab<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />23<br />
  39. 39. Conclusions and Future Work<br /><ul><li>Concept of ECOCELL core has been introduced
  40. 40. Vibro-acoustic response of several articles with common structure and difference in skin and core have been analyzed in terms of mean square velocity and radiated acoustic power, evaluating the influence of core configurations.
  41. 41. Confirm that randomization approach allows an improvement of vibro-acoustic behavior.
  42. 42. First experimental test has been introduced, without significant results due manufacturing problems.</li></ul>Future Work <br /><ul><li>Numerical developing: identifying an optimization method that lead an optimal configuration (multicriteria genetic algorithm)
  43. 43. Find the right technology to manufacture the sandwich panel, in order to compare numerical and experimental tests.</li></ul>Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />24<br />
  44. 44. Thanks foryourattention<br />Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />25<br />
  45. 45. General Remarks about Numerical Models<br /><ul><li>All the numerical models herein presented consist of two face sheets and one core domain, both made in aluminum.
  46. 46. The imposed boundary condition has both the face-sheet simply supported on their four edges.
  47. 47. In all models the in-plane dimensions of the panel are kept constant.
  48. 48. Sandwich panels with the same total mass are compared since the mass variation is a critical design parameter due to the characteristics of panel TL vs. mass.
  49. 49. The dynamic load was a pressure distribution according to a monopole acoustic source located 2 m. from the plate.
  50. 50. The structural-acoustic response is characterized in terms of mean square velocity - averaged over the spatial domain – and radiated acoustic power, calculated by using a finite element approach.
  51. 51. Numerical Optimization: MSC/NASTRAN optimizer (SOL 200) - Modified Method of Feasible Directions.;
  52. 52. Randomization: effect of the addition of a random distribution of the core stiffness. The random distributions were based on two (uncoupled) Gaussian functions.</li></ul>Progresses on the vibro-acoustic design of a class of aluminium sandwich plates<br />26<br />
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