Penn State Center for Acoustics and Vibration (CAV)

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Beck Robert Campbell James Chatterley Stephen Conlon Carl Cotner Tyler Dare John

1 Penn State Center for Acoustics and Vibration () Structural Vibration and Acoustics Group Presented as part of the 2017 Spring workshop Stephen Hambric, Group Leader Ben Beck Robert Campbell James Chatterley Stephen Conlon Carl Cotner Tyler Dare John Fahnline Sabih Hayek Kevin Koudela Kyle Myers Dan Russell Micah Shepherd Alok Sinha Andrew Wixom

2 Today s topics Accelerated Composite Fatigue Testing Chet Kupchella, MS 2017, and Drs. Rob Campbell, Kevin Koudela, and Steve Hambric Transient Structural-Acoustics Dr. John Fahnline Hybrid Method for Predicting Heavy Fluid Loading of Structures Dr. Micah Shepherd Uncertainty in Structural Acoustic Systems Dr. Andrew Wixom Noise and Vibration Emerging Methods 2018 (NOVEM) 2/33

3 Other Student Projects Student posters: Bolted Joint Dynamics Trevor Jerome, PhD student, and Drs. Micah Shepherd and Steve Hambric, advisors Large Chiller Vibration and Sound Steve Wells, PhD student, and Drs. Steve Hambric and Tim Brungart, advisors Just starting out: Small Reciprocating Compressor Noise and Vibration John Cunsolo, MS student, and Drs. Tim Brungart and Steve Hambric Adaptive Acoustic Metamaterials Aaron Stearns, PhD, Dr. Ben Beck, advisor Acoustics of Golf Putter Ball Impact Arjun Shankar, MS, Dr. Dan Russell, advisor Optimization of Acoustic Black Hole Designs Cameron McCormick, PhD, Dr. Micah Shepherd, advisor 3/33

4 Other Student Projects Graduated!!! Axtell, Wesley, Acoustics, Force reconstruction using force gauges and modal analysis Kerrian, Peter, Acoustics, Acoustic and vibrational analysis of golf club drivers Feurtado, Phil, Acoustics, Quiet Structure Design using Acoustic Black Holes Ken Aycock, Biomedical Engineering, Fluid-Structure Interaction Modeling of Blood Clot Migration and Entrapment in the Inferior Vena Cava 4/33

5 Accelerated Composite High Cycle Fatigue Testing Principal Investigator: Chet Kupchella, MS Acoustics Dr. Rob Campbell, Kevin Koudela, and Steve Hambric, Advisors Sponsor: 5/33

6 Motivation Fatigue Failure of Fiber- Reinforced Polymer Composites Fibers Glass or carbon Matrix Polymer resin 6/33

7 Failure Mechanisms I. Matrix cracking until crack saturation (wear-in) II. Isolated fiber separation III. Delamination and fiber failure Naderi /33

8 High Cycle Fatigue Life Projection R = -1: Fully Reversed is most limiting Strauch /33

9 Accelerated Testing Traditional fatigue testing is performed on expensive (usually Instron) machines at low frequencies Takes a long time to accumulate 10M (or more) cycles Use resonant beam apparatus to test at higher frequencies Obtain S-N data more quickly Or, run to higher cycle counts Lower cost 9/33

10 Resonant Beam with Bonded Composite Sample Composite sample experiences fully-reversed cyclic loading End masses adjust apparatus resonance frequency 10/33

11 Shaker Testing tip accel Strain Gage and Thermocouple 11/33

12 Track Resonance Frequency Shifting Throughout Testing 55 Hz 110 Hz 22 Hz 30 Hz 12/33

13 Temperature Correction Specimens heat up at higher frequencies 13/33

14 Resonance Frequency Reductions over Time Initial Data Temperature Correction Applied More frequency reduction at lower frequencies =, + 14/33

15 Residual Strength vs. Residual Modulus 10M Cycles Infer residual elastic modulus from resonance frequency shifting Measure residual strength on Instron machine Good correlation However, in general less damage with higher frequency loading 15/33

16 Conclusions so far Higher frequency testing does not induce the same damage as lower frequency testing for the same number of cycles Open questions: Is there any benefit to higher frequency testing? Need more tests at equivalent wall clock times Example: 110 Hz for 5x more cycles than 22 Hz testing Do composites accumulate damage differently at higher frequencies? If so, fatigue testing may be necessary at different frequencies 16/33

17 Transient Structural-Acoustic Computations Principal Investigators: John Fahnline and Robert Campbell Sponsor: 17/33

Transient Equivalent Sources Background: Stable transient boundary element formulations have been developed using Burton-Miller formulations Objective: Develop a stable transient equivalent source

18 Transient Equivalent Sources Background: Stable transient boundary element formulations have been developed using Burton-Miller formulations Objective: Develop a stable transient equivalent source formulation Technical Approach: Tripole sources are used to create a hybrid source with cardioid directivity The sound radiates primarily in the outward direction z = 0, 0 1, 0 a r Piston in a Cylindrical Baffle Reflection from back wall Simple Sources z = a, r = 0 z = a, r = a / 2 z = a, r = a z = a, r = 2 a Tripole Sources 18/33

19 Transient FE/ES Computations Objective: Develop a time-stepping formulation for structural-acoustic problems Technical Approach: The transient ES solution gives an equation relating pressure and volume velocity This is converted to a sparse acoustic coupling matrix relating nodal pressures and velocities for the current time step Convolution summations account for sound radiated in the past and are computed in parallel Ribbed Cylinder Drive 19/33

20 Advantages/Disadvantages Advantages: The computations are efficient because a wide frequency band can be analyzed with a single transient analysis For large practical problems, the time step size can be chosen so that the matrix solution times for the uncoupled and coupled problems are the same (the acoustic analysis is free ) The coupled FE/ES formulation can be adapted to nonlinear vibration problems Disadvantages: The time-stepping procedure adds a small amount of algorithmic damping due to the finite difference approximations Time-domain modeling of material damping is more difficult than in the frequency domain Refs: J. B. Fahnline, Solving transient acoustic boundary value problems with equivalent sources using a lumped parameter approach, The Journal of the Acoustical Society of America, 140(6), (2016). J. B. Fahnline and M. R. Shepherd, Transient finite element / equivalent sources using direct coupling and treating the acoustic coupling matrix as sparse, Submitted to The Journal of the Acoustical Society of America, March /33

21 Hybrid Method for Predicting Heavy Fluid Loading of Structures Principal Investigators: Dr. Micah Shepherd, Dr. John Fahnline, Dr. Tyler Dare, Dr. Rob Campbell, Dr. Steve Hambric Shepherd, et. al., A hybrid approach for simulating fluid loading effects on structures using experimental modal analysis and the boundary element method, J. Acoust. Soc. Am., 138 (5), , Nov /33

Hybrid Method for Inferring Fluid Loading Measuring the natural frequencies and damping loss factors of structures in heavy fluids can be difficult and expensive ω L = 1 ω 1+ m m v f s (1)

22 Hybrid Method for Inferring Fluid Loading Measuring the natural frequencies and damping loss factors of structures in heavy fluids can be difficult and expensive ω L = 1 ω 1+ m m v f s (1) Estimate the in-vacuo natural frequencies and mode shapes using in air experimental modal analysis (EMA) (2) Apply fluid loading numerically using boundary element (BE) method based on EMA grid 22/33

Φ μ M μ 6L = λ = c f 2 2 2 T 1 [ ] = ω + i A ξ ω η ω

23 Overview of Procedure H H ( ω ) = U ( ω ) S ( ω ) V ( ) ω0 f Φ Mμ = d i α αμ α ωμ ω + ημωμ 2 Φ μ M μ 6L = λ = c f T 1 [ ] = ω + i A ξ ω η ω +Φ Φ φ μ μ μ μ f u = ξφ T Π= ξ Φ Φ Re{ A } ξ T 23/33

air and in water Hit points connected to form boundary elements which

24 Ni-Al-Brz (NAB) Plate Experiment 1 7/8 thick NAB plate, 13x31 grid of excitation points (1 spacing) Suspended with 100 lb test fishing line in air and in water Hit points connected to form boundary elements which behave as dipoles with equivalent source amplitude determined by the nodal velocities 24/33

25 Comparison of Mode shapes, Velocity and OTO Loss Factors Coincidence estimate: 6.2 khz Measured in water Measured in air BE-based radiation loss factors can be removed from total loss factors to estimate in-vacuo structural damping Estimated material loss factor 25/33

26 Uncertainty in Structural Acoustic Systems Application of Generalized Polynomial Chaos Presenter: Andrew Wixom Collaborators: Micah Shepherd, Sheri Martinelli, Robert Campbell, Stephen Hambric Sponsor: ARL/Penn State 26/33

27 An example problem 0.3 L 0.6 L L Applied Force Spring, with uncertain spring constant. The distribution (PDF) of the spring constant is assumed to be known. Pinned beam with an uncertain spring How does the uncertainty affect the response of the beam? Natural frequencies? Mode shapes? Modal response? Full system response? 27/33

28 Generalized Polynomial Chaos Building on the work of K. Sepahvand et al., and text by D. Xiu Expansion by orthonormal polynomials = ( ) ( ) = Stochastic Collocation to evaluate coefficients Black box calculation: sample at quadrature points to evaluate integrals = = 28/33

29 Spring PDF Natural Frequency PDFs Compared to Monte Carlo Simulation Normal PDFs of First Three Natural Frequencies Blue Bars are approximate PDFs from Monte Carlo simulation Orange Curves are PDFs calculated by gpc expansion Uniform Log-Normal /33

30 Mode Shape, Modal Response, and System Response Uniform Spring Distribution, Mode /33

31 Mode Shape, Modal Response, and System Response Uniform Spring Distribution, Mode This mode may have a node at forcing location! 31/33

32 Summary Generalized Polynomial Chaos can be used to characterize the propagation of uncertainty throughout a structural-acoustic system Possible quantities of interest include: natural frequencies, mode shapes, and various responses Moving forward Uncertainty in boundary conditions Stochastic forcing functions (e.g. turbulent boundary layer) Alternatives to stochastic collocation for modal quantities Want more? Come see our ASA talk in Boston! 32/33

Noise and Vibration Emerging Methods (NOVEM) 2018 Co-organized by International Liaisons and other friends A. Berry, Sherbrooke L. Cheng, HK Poly S. De Rosa, University Federico O. Guasch, La Salle S.

33 Noise and Vibration Emerging Methods (NOVEM) 2018 Co-organized by International Liaisons and other friends A. Berry, Sherbrooke L. Cheng, HK Poly S. De Rosa, University Federico O. Guasch, La Salle S. Hambric, PSU J-G Ih, KAIST B. Mace, Auckland (formerly ISVR) G. Pavic, INSA Topics: Structural Vibration Vibro-Acoustics Flow-Induced Noise and Vibration Noise and Vibration Control Abstracts due 15 Oct /33

Penn State Center for Acoustics and Vibration (CAV)

Penn State Center for Acoustics and Vibration (CAV) Structural Vibration and Acoustics Group Presented as part of the 2015 CAV Spring workshop Stephen Hambric, Group Leader May 2015 Robert Campbell James