Download or read book Application of Acoustic Black Holes To Rotorcraft Structures for Vibration and Noise Control written by Robert Veltre and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, acoustic black holes have proven to be effective vibration damping and transmission loss mechanisms. By tapering the local thickness of the structure, the black holes are able to reduce the bending wave speed thereby focusing strain energy into localized viscoelastic damping. This improves the efficiency of the applied damping layers. Due to their promising potential to both reduce weight and enhance damping, acoustic black holes have a multitude of vehicle born applications. Interior noise reduction in rotorcraft is a prominent application due to the presence of gear meshing noise. In this work, the application of acoustic black hole treatments applied to plates and sandwich panel structures is evaluated computationally using the finite element method. These notional structures were evaluated over the frequency range of sound commonly transmitted by rotorcraft transmission systems. These results are then compared with results given by uniform plates and sandwich panels of similar dimensions. The results indicate that acoustic black holes reduce vibration in the aluminum sandwich panels by 10 dB compared to traditional damping approaches, while reducing weight.
Download or read book Optimization of Acoustic Black Holes for Vibration Reduction written by Cameron McCormick and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A problem that frequently arises in noise control engineering is the need for lightweight structures that are also quiet. In many practical instances of transportation and aerospace design, stiff, lightweight panels are used to reduce overall weight. However, these stiff, lightweight panels are also highly receptive to vibration and can become efficient radiators of sound. Although traditional methods of passive damping can effectively combat this behavior, they usually lead to an increase in overall weight. By modifying the plate thickness according to a specific power law profile, so-called `acoustic black holes' (ABHs) offer a compelling solution to the need for both broadband vibration reduction and reduced weight. ABH vibration absorbers have been shown to be effective at reducing structural vibration, often with a net reduction in overall weight. However, a comprehensive understanding of what constitutes optimal ABH design in finite structures has been historically lacking. This dissertation systematically investigates the many considerations of ABH design for vibration reduction. An optimization framework is developed that combines the modelling of structural dynamics with multi-objective evolutionary optimization, and this framework is used to determine the optimal designs for various ABH applications. By analyzing trends in the optimization results, the tradeoffs inherent in ABH design are illuminated in a more holistic manner than has been undertaken to date.
Download or read book Quiet Structure Design Using Acoustic Black Holes written by Philip Feurtado and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years Acoustic Black Holes (ABHs) have been developed and demonstrated as effective, passive, lightweight vibration absorbers of flexural bending waves in beam and plate like structures. ABHs employ a local power-law thickness profile into a beam or plate, typically resulting in a one dimensional wedge or a two dimensional indentation in the structure. By reducing the thickness of the structure the ABH effect decreases the bending wave speed and increases the transverse vibration amplitude. In the limit where the thickness goes to zero the wave speed goes to zero and the bending waves never reach the thin edge, thus they are `absorbed.' Real, machined ABHs necessarily have some finite truncation thickness. This results in local strain concentrations that effectively dissipate energy when coupled with a high loss material such as a traditional applied damping layer. While the effectiveness of ABHs has been established and demonstrated, there is still a need to develop new insights that can help designers tailor the performance of ABHs for practical, realizable, noise and vibration control applications. This research aimed to expand the existing understanding of ABHs in ways that will be useful and instructive for designing ABH systems for practical noise and vibration control problems. One of the ultimate goals of this branch of ABH research is to be able to prescribe a specific ABH design to suit a given noise and vibration control problem. The results and methods developed here represent a significant and useful step towards that goal. The first step involved investigating the limitations and implications of analytic ABH theory, the frequency dependent performance of ABH systems, and the structural acoustic coupling of embedded ABH systems with both response to distributed pressure excitations and radiation to the fluid surrounding the structure. Analytic ABH theory provides predictions for the vibration reduction from a one dimensional ABH wedge, but the predictions conflict with key underlying assumptions such that better vibration absorption is predicted from more significant violations of the fundamental theory assumptions. It was demonstrated that these effects can be significant for practical ABH designs and contribute to the effectiveness of ABHs, particularly at low frequencies. A new design parameter was developed based on the theoretical assumptions to aid the design, assessment, and optimization of ABHs.The low frequency performance, extension, and optimization of ABHs is also of particular interest because ABHs display a `cut on frequency' above which they become effective vibration absorbers. Experimental investigations were conducted on plates with embedded arrays of ABHs as well as an individual ABH at low, mid, and high frequency in order to gain insight into the frequency dependent behavior of ABHs. The results showed that the low frequency behavior of ABH systems is dictated by the activation of low order local ABH modes within the ABH taper. Analyzing the vibration of the ABH plates in the wavenumber domain also revealed that ABH plates significantly affect the wavenumber characteristics of the structure, reducing the speed of supersonic bending waves to subsonic speeds and reducing the coupling between the structure and the surrounding fluid. Additional transmission loss measurements and computational investigations demonstrated that the wavenumber sweep from the ABH effect also can significantly affect the power injection and response of embedded ABH plates to distributed pressure excitations. Simulation results illustrated conditions for both positive and negative effects for ABH system noise control effectiveness.
Download or read book Controlling Flexural Waves Using Subwavelength Perfect Absorbers written by Julien Leng and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vibration control adapted to light structures is a scientific and technological challenge due toincreasingly stringent economic and ecological standards. Meanwhile, recent studies in audible acoustics havefocused on broadband wave absorption at low frequencies by means of subwavelength perfect absorbers. Suchmetamaterials can totally absorb the energy of an incident wave. The generalisation of this method for applicationsin elastodynamics could be of great interest for the vibration control of light structures.This thesis aims at adapting the perfect absorption problem for flexural waves in 1D and 2D systems with localresonators using the critical coupling condition. A study of 1D systems with simple geometries is first proposed. Thisprovides methods to design simple resonators for an effective absorption of flexural waves. The 1D systems thenbecome more complex by studying the critical coupling of 1D Acoustic Black Holes (ABH). The ABH effect is theninterpreted using the concept of critical coupling, and key features for future optimisation procedures of ABHs arepresented. The critical coupling condition is then extended to 2D systems. The perfect absorption by the firstaxisymmetric mode of a circular resonator inserted in a thin plate is analysed. Multiple scattering by an array ofcircular resonators inserted in an infinite or semi-infinite 2D thin plate, called metaplate, is also considered to getclose to practical applications. Through this thesis, analytical models, numerical simulations and experiments areshown to validate the physical behaviour of the systems presented.
Download or read book Proceedings of the 6th China Aeronautical Science and Technology Conference written by Chinese Aeronautical Society and published by Springer Nature. This book was released on 2024-01-07 with total page 711 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the original peer-reviewed research papers presented at the 6th China Aeronautical Science and Technology Conference held in Wuzhen, Zhejiang Province, China, in September 2023. Topics covered include but are not limited to Navigation/Guidance and Control Technology, Aircraft Design and Overall Optimisation of Key Technologies, Aviation Testing Technology, Airborne Systems/Electromechanical Technology, Structural Design, Aerodynamics and Flight Mechanics, Advanced Aviation Materials and Manufacturing Technology, Advanced Aviation Propulsion Technology, and Civil Aviation Transportation. The papers presented here share the latest findings in aviation science and technology, making the book a valuable resource for researchers, engineers and students in related fields.
Download or read book Proceedings of the 2nd International Conference on Mechanical System Dynamics written by Xiaoting Rui and published by Springer Nature. This book was released on with total page 4383 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sensors Instrumentation and Aircraft Aerospace Testing Techniques Volume 8 written by Chad Walber and published by Springer Nature. This book was released on 2023-12-23 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sensors & Instrumentation and Aircraft/Aerospace Testing Techniques, Volume 8: Proceedings of the 41st IMAC, A Conference and Exposition on Structural Dynamics, 2023, the eighth volume of ten from the Conference brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on fundamental and applied aspects of Shock & Vibration, Aircraft/Aerospace Testing Techniques including papers on: Alternative Sensing & Acquisition Active Controls Instrumentation
Download or read book Development of Rotorcraft Interior Noise Control Concepts Phase 1 Definition Study written by and published by . This book was released on 1983 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Thesaurus written by and published by . This book was released on 1994 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 974 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental and Computational Instrumentation for Rotorcraft Noise and Vibration Control Research at the Penn State Rotorcraft Center written by and published by . This book was released on 2001 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: A team of faculty at the Penn State Rotorcraft Center of Excellence has integrated five new facilities into a broad range of research and educational programs focused on rotorcraft noise and vibration control. The new facilities are: (1) Airframe Driveshaft Active Control Testbed, (2) Real-Time Visualization and Computation Facility, (3) High Frequency Elastomeric Material and Component Characterization Test Facility, (4) Scanning Laser Vibrometer for Rotorcraft Noise and Vibration Control, and (5) Scale Model Helicopter Fuselage Vibration test Facility. These new facilities have significantly improved the ability of Penn State graduate students and faculty to contribute to DoD sponsored research programs in the field of Rotorcraft Engineering. Each item is linked directly to existing multi-year programs at Penn State including the ARO sponsored MURI on Active Control of Rotorcraft Noise and Vibration, the NRTC Rotorcraft Center of Excellence, ARO Young Investigator Awards, ARO, ONR, and NASA Core Program Grants, and numerous coordinated contracts with Industry. This experimental equipment has allowed for new data and measurements in the areas of rotorcraft vibration and noise control, low vibration dynamic systems, enhanced safety and reliability, and advanced composite materials. In addition, new specialized computational facilities will be focused on an array of numerically intensive rotorcraft optimization projects, aeroacoustic prediction methods, and aeroelastic simulations. This equipment has had a major positive impact on the educational infrastructure and resources at the recently established Penn State Rotorcraft Center of Excellence.
Download or read book Calm Smooth and Smart written by Peter Eberhard and published by Springer Nature. This book was released on 2023-09-19 with total page 353 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains and summarizes research carried out within the DFG Priority Programme 1897: "Calm, Smooth and Smart - Novel Approaches for Influencing Vibrations by Means of Deliberately Introduced Dissipation". The contributions help reduce unwanted vibrations by developing novel approaches for influencing them and lead to a “calm, smooth and smart” behaviour of technical units. “Calm” represents the demand to avoid or at least to severely reduce unwanted noise generated by technical installations. “Smooth” ensures a still comfortable and jerk-free operation of them. Finally, “smart” means that the introduced damping devices not only help to achieve the desired vibrational behaviour of the overall technical systems, but also that they take over additional functional tasks. The results presented in this volume summarize the state-of-the-art and provide motivation for future research. The book is intended for experienced researchers as well as for doctoral and post-doctoral students in engineering, mathematics and physics, as well as industrial researchers interested in the field.
Download or read book NASA SP written by and published by . This book was released on 1992 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structural Acoustic Prediction and Interior Noise Control Technology written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-09-21 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1967 with total page 686 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book 1980 NASA authorization written by United States. Congress. House. Committee on Science and Technology. Subcommittee on Space Science and Applications and published by . This book was released on 1978 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:
