In this paper, recent results of ongoing studies into the effectiveness and predictability of particle damping are discussed. Efforts have concentrated on characterizing and predicting the behavior of a wide range of potential particle materials, shapes, and sizes in the laboratory environment, as well as at elevated temperature. Methodologies used to generate data and extract the characteristics of the nonlinear damping phenomena are illustrated with interesting test results. Experimental results are compared to predictions from analytical simulations performed with an explicit code, based on the particle dynamics method, that has been developed in support of this work.

No abstract

In this paper, recent results of ongoing studies into the effectiveness and predictability of particle damping are discussed. Efforts have concentrated on characterizing and predicting the behavior of a wide range of potential particle materials, shapes, and sizes in the laboratory environment, as well as at elevated temperature. Methodologies used to generate data and extract the characteristics of the nonlinear damping phenomena are illustrated with interesting test results. Experimental results are compared to predictions from analytical simulations performed with an explicit code, based on the particle dynamics method, that has been developed in support ofthis work.

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING AGENCY ACRONYM(S)AFRL DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTESReport contains color. ABSTRACTThe present theory and implementation methodology for the smoothing, interpolation, and modeling of complex modulus data for viscoelastic damping materials has achieved a substantial level of maturity, accuracy, and efficiency; moreover, interconversion among any of the dynamic mechanical properties, the display of relaxation and retardation spectra, and estimated relative molecular weight distribution are greatly facilitated. One key aspect of the approach is to use a ratio (where the order of the numerator and denominator are equal) of polynomials of first order factors to model the complex modulus; this guarantees intrinsically that the required properties of linear systems are satisfied, while also providing an ease of numerical convergence and of interconversion. A second key aspect is the use of the Wicket Plot to 1) edit and perform a quality check on the data, 2) smooth and interpolate the data, 3) map its arc length onto reduced radian frequency, thereby intrinsically defining the complex valued modulus as a function of the reduced radian frequency, and 4) determine the value of the temperature shift function for each experimental data point, an entirely new procedure.15.

Polymers constitute a large class of nearly incompressible solid materials (i.e., Poisson's Ratio near 0.5). These materials are often used as passive vibration isolators. Accurately modeling vibration isolators made of nearly incompressible materials has been extremely difficult with standard finite element analysis. This paper provides an alternative to the specialized finite element formulations currently used to model incompressible materials.The finite volume methodology of computational fluid dynamics is employed in this paper to solve the Hooke's Law equations in solid mechanics. Test cases have been performed to evaluate the performance of finite volume method applied to solid mechanics problems. The formulation has been coded in Matlab for practical use. Based on the preliminary test case results, the finite volume formulation compares favorably to finite element method.