frictionless case. A general relationship between the crack tip driving force and the crack tip shear displacement is proven to exist, for the linear elastic material, with a non-frictional crack. Cyclic crack propagation experiments under cyclic torque plus alternating compression are described. An alternative experimental method to determine the crack propagation rate under nominal Mode III conditions is introduced. The experimentally observed reduction in the propagation rate are qualitatively explained. The morphology of the resulting fracture surface is described, as well as its influence on the propagation rate. A new technique aimed to find an effective crack face friction coefficient is presented. The complex behavior of a Mode III shear crack under compression is qualitatively described. Dissert. Abstr. N91-12110 Cornell Univ., Ithaca, NY. A DAMAGE INTEGRAL APPROACH FOR LOW-CYCLE A damage integral approach for low-cycle isothermal and thermal fatigue is examined. This approach involves the calculation of the stress, estimation of damage rates, and integration of the damage to determine the low-cycle fatigue life. The stress profile is dependent on the time profile of the applied displacement, the effective stiffness, and the inelastic deformation properties. The rate of damage accumulation is influenced by the stress state, the environment, and the temperature. A phenomenological approach based on a state variable concept was adequate in describing the stresses for a variety of test methods and loading profiles. The considerations involved in the application of a similar approach to damage rate modelling is considered. The ramifications of the environment and damage mechanisms on a phenomenological damage rate relation are examined. The application of a damage integral approach to low-cycle high-temperature fatigue is demonstrated using solder joint fatigue. Solder joints with eutectic compositions are emphasized. First, the application of published data is reviewed and it is shown that phenomenological constitutive relations may be used to accurately calculate the stresses in the solders and solder joints during isothermal mechanical displacement and thermal displacement cycling. The determination of the crack growth is used to describe the damage rate. The effects of temperature and applied loading frequency on the crack growth rate are discussed. Finally, the considerations involved in the integration of the crack growth rate formulation, and effects of the failure criterion on the apparent fatigue life are described. Dissert. Abstr. N91-12111 Purdue Univ., West Lafayette, IN. Lung-Siaen Chien 1989 154 P Avail: Univ. Microfilms Order No. DA9018804 A number of parallel computational methods are developed in the present study to solve structural mechanics problems. A parallel Gaussian elimination solution scheme is first introduced to solve a large system of linear algebraic equations. Then, parallelization of the non-linear finite element solution procedures is achieved by incorporating the above parallel Gaussian elimination technique. A two-dimensional large truss structure with both material and geometric nonlinearities is analyzed to demonstrate the speedup of a solution by two parallel stages, i.e., the repeated forming of the nonlinear global stiffness matrix and the solving of the global system of equations. Parallel algorithms are also developed by introducing orthogonal functions to solve two-dimensional boundary value problems. The problems governed by second order and by fourth order differential equations with regular geometrical domains are discussed. Finally, the inherent parallelism of the boundary element method is shown. The boundary element is simulated by assuming the linear variation of displacements and tractions within a straight line element. Moreover, MACSYMA symbolic program is employed to obtain the analytical results for influence coefficients. The linear speedups and high efficiencies are shown in each proposed parallel processing technique and parallel numerical AN ASSUMED STRAIN FINITE ELEMENT MODEL FOR Chan Hong Yeom 1989 179 p Avail: Univ. Microfilms Order No. DA9021607 A kinematically stable nine-node mixed finite element was developed for analyses of plates and shells. The present element is based on the Hellinger-Reissner principle with independent strain and uses the degenerated solid shell concept. A new method of assuming independent strain fields was examined for a nine-node degenerated solid shell element. The independent strain is assumed initially for the local orthogonal coordinate system determined at the origin of the parent coordinates. With the strain transformation rule, the assumed strain components are transformed into the local coordinate system defined at each integration point. Then the resulting stiffness matrix is invariant even for the nonsymmetric set of polynomial terms of assumed strain. Numerical results of simple stress state problems indicate that this element is not sensitive to element distortion in flat or curved geometries. This element performs well without showing any locking tendency and all kinematic modes are properly suppressed. The linear nine-node assumed strain element was extended to non-linear analyses of isotropic and laminated composite shells undergoing large deflection with finite rotations. Displacement-dependent strain, independent strain and the determinant of Jacobian matrix are assumed to vary linearly through thickness. This allows analytical integration in the thickness direction regardless of the number of ply layups in composite structures. The present formulation also allows the reference plane to be located anywhere in the thickness direction. This feature provides a convenient means to model a shell with an internal delamination or a shell with stiffeners. The results of numerical tests indicate that the present formulation provides reliable solutions for geometrically nonlinear, isotropic, and composite plates and shells. Dissert. Abstr. N91-12113 Wisconsin Univ., Madison. Avail: Univ. Microfilms Order No. DA9020475 The recent development of viscous material models are summarized and a representative family of three dimensional viscoelastic-viscoplastic material models proposed which includes the widely used viscoplastic and viscoelastic models as special cases. The models also facilitate the inclusion of a variety of internal variables proposed recently by other researchers. A modified Euler algorithm is used to integrate the constitutive equations. An implicit-explicit predictor corrector scheme is used to solve the transient equations. Derivation of stability conditions for the viscoelastic part is illustrated using the central difference method. The development of the general purpose nonlinear program is discussed. The use of supercomputing also is discussed, although the material behavior of the models is the main focus. Numerical examples for one dimensional and plane strain models are presented with a variety of loadings. Dissert. Abstr. N91-12114*# National Aeronautics and Space Administration. Shantaram S. Pai Sep. 1990 11 p Presented at the 3rd Air A three-bay, space, cantilever truss is probabilistically evaluated using the computer code NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) to identify and quantify the uncertainties and respective sensitivities associated with corresponding uncertainties in the primitive variables (structural, material, and loads parameters) that defines the truss. The distribution of each of these primitive variables is described in terms of one of several available distributions such as the Weibull, exponential, normal, log-normal, etc. The cumulative distribution function (CDF's) for the response functions considered and sensitivities associated with the primitive variables for given response are investigated. These sensitivities help in determining the dominating primitive variables for that response. Author N91-12115*# National Aeronautics and Space Administration. Langley Research Center, Hampton, VA. THERMAL-STRUCTURAL FINITE ELEMENT ANALYSIS USING LINEAR FLUX FORMULATION Ajay K. Pandey (Planning Research Corp., Hampton, VA.), Pramote Dechaumphai, and Allan R. Wieting Oct. 1990 12 p Presented at the 30th Structures, Structural Dynamics and Materials Conference, Mobile, AL, 3-5 Apr. 1989 Previously announced in IAA as A89-30711 (NASA-TM-102746; NAS 1.15:102746) Avail: NTIS HC/MF A03 CSCL 20K A linear flux approach is developed for a finite element thermal-structural analysis of steady state thermal and structural problems. The element fluxes are assumed to vary linearly in the same form as the element unknown variables, and the finite element matrices are evaluated in closed form. Since numerical integration is avoided, significant computational time saving is achieved. Solution accuracy and computational speed improvements are demonstrated by solving several two and three dimensional thermal-structural examples. Author N91-12116*# National Aeronautics and Space Administration. Langley Research Center, Hampton, VA. K. N. Shivakumar (Analytical Services and Materials, Inc., Hampton, ZIP3D is an elastic and an elastic-plastic finite element program to analyze cracks in three dimensional solids. The program may also be used to analyze uncracked bodies or multi-body problems involving contacting surfaces. For crack problems, the program has several unique features including the calculation of mixed-mode strain energy release rates using the three dimensional virtual crack closure technique, the calculation of the J integral using the equivalent domain integral method, the capability to extend the crack front under monotonic or cyclic loading, and the capability to close or open the crack surfaces during cyclic loading. The theories behind the various aspects of the program are explained briefly. Line-by-line data preparation is presented. Input data and results for an elastic analysis of a surface crack in a plate and for an elastic-plastic analysis of a single-edge-crack-tension specimen are also presented. N91-12117*# California Univ., Santa Barbara. MATERIALS WITH PERIODIC INTERNAL STRUCTURE: COMPUTATION BASED ON HOMOGENIZATION AND COMPARISON WITH EXPERIMENT Final Report Author S. Jansson, F. A. Leckie, E. T. Onat, and M. P. Ranaweera Oct. 1990 70 p (Grant NAG3-894) (NASA-CR-185303; NAS 1.26:185303) Avail: NTIS HC/MF A04 CSCL 20K The combination of thermal and mechanical loading expected in practice means that constitutive equations of metal matrix composites must be developed which deal with time-independent and time-dependent irreversible deformation. Also, the internal state of composites is extremely complicated which underlines the need to formulate macroscopic constitutive equations with a limited number of state variables which represent the internal state at the micro level. One available method for calculating the macro properties of composites in terms of the distribution and properties of the constituent materials is the method of homogenization whose formulation is based on the periodicity of the substructure of the composite. A homogenization procedure was developed which lends itself to the use of the finite element procedure. The efficiency of these procedures, to determine the macroscopic properties of a composite system from its constituent properties, was demonstrated utilizing an aluminum plate perforated by directionally oriented slits. The selection of this problem is based on the fact that, extensive experimental results exist, the macroscopic response is highly anisotropic, and that the slits provide very high stress gradients which severely test the effectiveness of the computational procedures. Furthermore, both elastic and plastic properties were investigated so that the application to practical systems with inelastic deformation should be able to proceed without difficulty. The effectiveness of the procedures was rigorously checked against experimental results and with the predictions of approximate calculations. Using the computational results it is illustrated how macroscopic constitutive equations can be expressed in forms of the elastic and limit load behavior. Author N91-12118 Lehigh Univ., Bethlehem, PA. Avail: Univ. Microfilms Order No. DA9016619 The influence of a thermal field on the stretching of a uniaxial cylindrical bar specimen made of 6061 aluminum is investigated. Prescribed is a displacement rate of 1.27 x 10(exp -4) cm per sec while the temperature sufficiently far away is maintained constant. A two-phase solid/fluid problem is solved by application of the isoenergy density theory such that the thermal/mechanical interphase conditions are determined rather than assumed as boundary of interface conditions in classical field theory. The change in local strain rates and strain rate history for each solid and fluid mass element are determined in accordance with the prescribed load or displacement rate. Thermal disturbances created by the slow stretched solid prevailed for a distance more than half the specimen length before they died out. The cooling/heating was very pronounced; temperature within the solid remained below ambient for more than 10 minutes. Thermal conductance coefficients varied with space and time, a characteristic of nonequilibrium. The classical handbook value of thermoconductivity for the 6061 aluminum corresponds closely to that obtained by averaging over all mass elements for a period of 12 minutes. They all increase slightly with rising ambient temperature. The same applied to the convective coefficient of heat transfer. Even at the very low displacement rate, the thermal/mechanical states in the described specimen were found to be highly nonequilibrium for a significant portion of the load history. The local stress, strain, temperature and energy density vary from one part of the system to another at each time instance. The conventional assumption that the state of affairs remains constant over a certain gage length cannot be justified. Nonequilibrium thermal/mechanical physical parameters can be averaged for all mass elements over a sufficiently long time to determine the constitutive coefficients for thermomechanical equilibrium field theories. Dissert. Abstr. N91-12119 Maryland Univ., College Park. A THREE-DIMENSIONAL ASSUMED STRESS HYBRID Avail: Univ. Microfilms Order No. DA9030878 A hybrid finite element formulation using both the assumed stress field and the assumed displacement field was developed for the analysis of three dimensional solids undergoing finite strain elastic-viscoplastic deformation. The eight-node three dimensional solid element is used in conjunction with a properly chosen assumed stress field. The stress field is defined in terms of local coordinates pertaining to each element and the assumed stress parameters are eliminated at the element level. In order to maintain element invariance, an iterative method is proposed that uniquely determines the local orthogonal coordinate system for a given arbitrary geometry of an element. The incremental constitutive relation for finite strain elastic viscoplastic deformation is derived for use in the finite element formulation. The von Mises yield function with an isotropic hardening rule is assumed to define the viscoplastic strain rate. The temperature rise due to mechanical work by viscoplastic deformation is considered. For description of the geometry and the kinematics of deformation, the updated Lagrangian formulation is adopted. For timewise integration, an implicit scheme is used. The resulting system of nonlinear equations is solved using the Newton-Raphson iteration scheme. According to the numerical results, the present formulation gives the kinematically stable solution for elastic-viscoplastic as well as elastic-plastic large strain problems without showing incompressibility locking. Even though numerical tests are concentrated on two dimensional problems, the present finite element formulation can handle three dimensional problems. Dissert. Abstr. N91-12120 Wichita State Univ., KS. STRUCTURAL DYNAMICS OF PLATES AND SHELLS SUBJECTED TO ELECTRO-IMPULSE DE-ICING FORCES Ph.D. Thesis Peter Hilton Gien 1989 153 p Avail: Univ. Microfilms Order No. DA9027479 The structural dynamics of a circular plate and a semicircular cylindrical shell with pinned boundary conditions subjected to electro-impulse deicing forces are investigated experimentally and analytically. A closed form modal synthesis method, a direct linear transient dynamics finite element method, and a non-linear direct transient dynamics finite element method are used to predict acceleration and displacement time histories on the circular plate and compared to experimental values obtained with accelerometers and optical displacement tracing devices. The presence of spurious bending waves induced by changes in finite element size was demonstrated. The comparison of experimental to predicted response revealed that geometric non-linearities accounted for large discrepancies between experimental data and linear analysis data. The effects and radial forces of transverse shear flexibility and air inertia effects were also studied. They were found to be of secondary importance. The sensitivity of the electro-impulse deicing pressure time history to electrical and geometric parameters was investigated and a least squares method of estimating circuit capacitance, lead cable inductance and resistance is presented. The computed impulse strengths were verified by a carefully controlled ballistic pendulum experiment with excellent results. A linear transient dynamic solution of the semicircular cylindrical shell compared favorably with the experimental data for large times and large distances from the applied forces. Computer animations of the acceleration and displacement time histories were prepared. Dissert. Abstr. N91-12121 Florida Atlantic Univ., Boca Raton. WEIGHT FUNCTION APPROACH FOR STRESS ANALYSIS OF Avail: Univ. Microfilms Order No. DA9029103 The effects of various nonuniform stress fields on the stress intensity factors for the semi-elliptic surface crack (three-dimensional problem) in a finite plate are determined using the weight function approach. The formulation satisfies the linear elastic fracture mechanics criteria and the principle of conservation of energy. Based on the knowledge of stress intensity solutions for the reference load/stress system, the expression for the crack opening displacement function for the surface crack is derived. Using the crack opening displacement function and the reference stress intensity factor, the three-dimensional weight functions and subsequently the stress intensity solutions for the surface crack subjected to nonuniform stress fields are derived. The formulation is then applied to determine the effects of linear, quadratic, cubic, and pure bending stress fields on the stress intensity factor for the surface crack in a finite plate. In the initial stage of the study a two-dimensional problem of an edge-crack emanating from the weld-toe in a T-joint is considered. The effect of parameters such as plate thickness, weld-toe radius, and weld-flank angle on the stress intensity factor for an edge-crack is studied. Finite element analyses of the welded T-joints are performed to study the effects of plate thickness, weld-toe radius, and the weld-flank angle on the local stress distribution. The ratio of plate thickness to weld-toe radius ranging from 13.09 to 153.93, and the weld-flank angles of 30, 45, and 60 degrees are considered in the analyses. Based on the results from finite element modeling (FEM) analyses, a parametric equation for the local stress concentration factor and a polynomial expression for the local stress distribution across the plate thickness are derived using the method of least squares and the polynomial curve-fitting technique. Dissert. Abstr. N91-12122 California Univ., Berkeley. THE INFLUENCE OF STRESS ON THE DYNAMIC RESPONSE Avail: Univ. Microfilms Order No. DA9028780 The influence of stress on straight-crested waves propagating in an elastic layer, either free, submerged in a fluid, or attached to a substrate is presented. The analytical solution derived from three-dimensional theory is numerically evaluated and then presented as either frequency spectra or dispersion curves. Both Lamb waves, in which the material particles move in the plane of propagation, and shear waves, in which the material particles move perpendicular to the plane of propagation, are considered to exist independently in the stressed layer. For Lamb waves the numerical data of wave propagation in a free aluminum layer, a water-loaded aluminum layer and an aluminum layer on either beryllium or fused silica are presented. For shear waves the numerical data of the aluminum layer on either beryllium or fused silica are shown as dispersion curves. At short wavelength limits of the dispersion curves the acoustoelasticities of shear and Rayleigh waves for the bulk aluminum are observed. The results of membrane theory are also obtained from the current theory in the long wavelength limit. The third-order elastic constants of the layer material are found to play an important role in the influence of stress on the wave propagation for most modes. The influence on the attenuation (corresponding to the imaginary part of wavenumber) of waves propagating in the fluid-coupled layer is also examined. The analytical results show that the solution of the fluid-coupled layer, given by the vanishing of the determinant of a 3 x 3 matrix and the solution of the layer on a substrate given by the vanishing of the determinant of a 6 x 6 matrix are much more complex than that of the free layer. However, the similarities of the influence of stress are found to exist among all of the cases. Dissert. Abstr. N91-12123# Los Alamos National Lab., NM. P. J. Maudlin, R. F. Davidson, and R. J. Henninger Sep. 1990 62 p (Contract W-7405-eng-36) (DE90-017855; LA-11895-MS) Avail: NTIS HC/MF A04 A flow stress constitutive model based on dislocation mechanics was implemented in the EPIC2 and PINON continuum mechanics modes. This model provides a better understanding of the plastic deformation process for ductile materials by using an internal state variable called the mechanical threshold stress. This kinematic quantity tracks the evolution of the material's microstructure along some arbitrary strain, strain rate, and temperature dependent path using a differential form that balances dislocation generation and recovery processes. Given a value for the mechanical threshold stress, the flow stress is determined using either a thermal activation controlled or a drag-controlled kinetics relationship. The performance was evaluated of the Mechanical Threshold Stress (MTS) model in terms of accuracy UNCONVENTIONAL STRUCTURES BY SONIC BOOMS Final Report, Nov. 1988- Jan. 1990 Louis C. Sutherland, Ron Brown, and Dawn Goerner May 1990 274 P (Contract F08635-89-C-0044; AF Proj. 3037) (AD-A225029; WR-89-14; HSD-TR-90-021) Avail: NTIS HC/MF A12 CSCL 01/2 Supersonic operations of U.S. Air Force aircraft cause sonic booms which may be the source of damage to unconventional structures. This problem is addressed in this report by (1) a literature survey of damage prediction and damage assessment techniques for such structures; (2) development of a statistical model for sonic boom overpressures with emphasis on supersonic operating areas (SOAs) employed for air combat maneuver training; (3) development of an analytical model to predict the probability of damage; (4) execution of a limited experimental program at White Sands Missile Range to evaluate response and potential damage of two unconventional structures in support of the prediction model; and finally (5) definition of algorithms for use in the Air Force ASAN computer program for evaluation of the probability of damage to unconventional structures from sonic booms. GRA The obvious benefits of the design of aerospace structures using lighter materials with high specific strengths and stiffnesses had led to the development of numerous reinforced composite metallic and intermetallic materials, which have become serious commercial competitors to traditional monolithic metallic alloys. While significant advances in processing technology have made the fabrication of such hybrid materials more of an economic reality, their widespread use in airframes or other structures has been limited by serious deficiencies in mechanical properties, particularly ductility, toughness and fatigue. This problem is compounded by the lack of fundamental studies which provide a rational basis for (Contract N00014-85-K-0471) (AD-A225056) Avail: NTIS HC/MF A02 CSCL 20/11 The follow topics are discussed: (1) One dimensional response of periodically layered composites in contact with an acoustic fluid; (2) Applicability of Floquet theory to bounded periodic domains; (3) Two dimensional waves in anisotropic layered composites; (4) The surface impedance tensor (Rayleigh waves in anisotropic layered composites); (5) Rayleigh-Lamb waves in anisotropic layered composites; (6) Scholte-Gogoladze type waves at the interface between a fluid and an anisotropic layered composite; and (7) An algorithm for the computation of the surface impedance tensor of anisotropic layered media. GRA N91-12128# Northwestern Univ., Evanston, IL. Dept. of Materials RESIDUAL STRESS AND DIFFRACTION ELASTIC R. A. Winholtz and J. B. Cohen Jul. 1990 69 p (AD-A225145; TR-27) Avail: NTIS HC/MF A04 CSCL 14/2 Software is described for the measurement of residual stresses and x ray elastic constants on a diffractometer under computer control. The computer and interfaces to the hardware are relatively inexpensive and may be set up with only moderate electronic and programming expertise. Both biaxial and triaxial stress measurements may be made to an operator specified error. Measurements of the x ray elastic constants may also be made to a pre-specified error. Additionally, programs for use in data collection are described which allow the data to be processed separately at a later time. GRA N91-12129# Oak Ridge National Lab., TN. 16 p B. R. Bass 1 Oct. 1990 Avail: NTIS HC/MF A03 Discussions were held with Japanese researchers concerning (1) the Elastic-Plastic Fracture Mechanics in Inhomogeneous Materials and Structures (EPI) Program, and (2) ongoing large-scale pressurized- thermal-shock (PTS) experiments in Japan. In the EPI Program, major activities in the current fiscal year include round-robin analyses of measured data from inhomogeneous base metal/weld metal compact-tension (CT) specimens fabricated from welded plates of A533 grade B class 1 steel. The round-robin task involves participants from nine research organizations in Japan and is scheduled for completion by the end of 1990. Additional experiments will be performed on crack growth in inhomogeneous CT specimens and three-point bend (3PB) specimens 10 mm thick. The data will be compared with that generated previously from 19-mm-thick-specimens. A new type of inhomogeneous surface-cracked specimen will be tested this year, with ratio of crack depth to surface length (a/c) satisfying 0.2 is less than or equal to (a/c) is less than or equal to 0.8 and using a 3PB type of applied load. Plans are under way to fabricate a new welded plate of A533 grade B class 1 steel (from a different heat than that currently being tested) in order to provide an expanded fracture-toughness data base. Other topics concerning fracture-prevention issues in reactor pressure vessels were discussed with each of the host organizations, including an overview of ongoing work in the Heavy-Section Steel Technology (HSST) Program. DOE Wave profiles in Armco iron were obtained with conventional planar impact technique. The free surface velocity was measured using a VISAR interferometric system. Maximum strain rates were determined from the plastic part of the wave profiles. The stress range covered the region between Hugoniot elastic limit and phase transition. From the data an improved U(sub s) - u(sub p) relation was obtained. Transient behavior was observed in the lower strain rate regime. A viscosity model was implemented in a finite element code and satisfactorily reproduced the wave profiles measures in the experiment. N91-12131# ESA Technische Univ., Berlin (Germany, F.R.). Inst. fuer Luft- und Raumfahrt. Joachim Hildebrand Apr. 1990 105 p In GERMAN Compared calculation of displacement and forces on plates are carried out, using numerical and analytical computing processes. The numerical calculation, is concerned with a mixed finite process and a finite element program, on the basis of the deformation value process. The linear treatment of the analytical calculation and the nonlinear treatment were carried out. The numerical treatment of the Levy analytical solution is the central point of the task. The comparison of the used calculation process concerning preparation, calculation time, and results gives a criterion for the choice of a possible solution in the treatment of plate problems. ESA A SEM PROCEDURE FOR QUANTIFYING TRANSGRANULAR FRACTURE IN BRITTLE MATERIAL Wein-Joe Yang, Chang Te Yu, and Albert S. Kobayashi Jul. 1990 20 p (AD-A225211; UWA/DME/TR-90/3) Avail: NTIS HC/MF A03 CSCL 11/2 A Scanning Electron Microscopy (SEM) procedure for quantifying the percentage area of transgranular fracture was developed for studying the fracture morphologies of stable and rapid crack growths in ceramics and ceramic matrix composites. The procedure utilizes SEM line scanning profiles which are scanned and then interpreted as percentage area of transgranular fracture and surface roughness through a special software. This procedure was used to quantify the percentage area of transgranular fracture and surface roughness which were correlated with the visual observations and profilometer measurements respectively, of Al2O3 and SiC(w)/Al2O3 fracture specimens. Dynamic fracture of quasi-brittle metals and polymers are characterized by crack velocity versus stress intensity factor (SIF) relations which represent a gamma curve with distinct crack arrest SIF's. GRA The U.S. Navy continues to investigate and develop better methods for ship noise and vibration reduction. One such method is the introduction of waveguide absorbers. This research is a continuation with the use of viscoelastic waveguide absorbers as a means of reducing the vibrational energy developed within a plate like structure, such as a ship's hull between frames and longitudinals. The effects of temperature and size of circular viscoelastic waveguide absorbers, on the driving point impedance were studied and the test results were compared with a previously developed computer prediction model with very favorable agreement. A study for the development of the scheme for the selection of waveguide absorbers and for the decision of the attachment locations for the maximum vibration reduction based on the waveguide absorber loss factor equation was also performed. One, two, and three waveguide absorbers were attached to a vibrating plate velocity, to confirm the use of the loss factor equation. Experimental results showed significant reduction of vibration at resonant frequencies. GRA N91-12133# Naval Postgraduate School, Monterey, CA. EXPERIMENTAL STUDIES OF CIRCULAR VISCOELASTIC WAVEGUIDE ABSORBERS FOR PASSIVE STRUCTURAL DAMPING M.S. Thesis Stephen J. Watson Dec. 1989 72 p (AD-A225409) Avail: NTIS HC/MF A04 CSCL 20/11 No abstracts in this category. |