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Articles 61 - 90 of 110

Full-Text Articles in Mechanics of Materials

The Effect Of A Hard Coating On The Damping And Fatigue Life Of Titanium, Frank T. Ivancic Mar 2003

The Effect Of A Hard Coating On The Damping And Fatigue Life Of Titanium, Frank T. Ivancic

Theses and Dissertations

This project compares the damping and fatigue life of bare titanium plates to those coated with magnesium aluminate spinel (mag spinel). Two different coating thicknesses were tested: .005" per side and .010" per side (total thicknesses of .010" and .020"). Dynamic ping tests were conducted on all specimens to determine their resonance frequencies. Laser vibrometry was used to determine the mode at each resonance frequency. Damping ratios were determined through the use of sine sweeps. A vibration mode was selected at which to fatigue the specimens, and the stress pattern was analyzed utilizing the Stress Pattern Analysis by Thermal Emissions …

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Effects Of Shot-Peening On High Cycle Fretting Fatigue Behavior Of Ti-6al-4v, Halil I. Yuksel Mar 2002

Effects Of Shot-Peening On High Cycle Fretting Fatigue Behavior Of Ti-6al-4v, Halil I. Yuksel

Theses and Dissertations

Effects of Shot-peening on High Cycle Fretting Fatigue behavior of Ti-6Al-4V were investigated. Experiments were performed with 6.35 mm thick specimens which provided S/N curves. After the tests, it was observed that the specimens failed near the trailing edge of contact. Scanning Electron Microscopy showed that cracks initiated on the contact surface for 6.35 mm, and at the depth of specimen ranging from 200 to 300 microns for 3.81 mm thick specimens. Initial crack orientation was around 37 and 42 degrees respectively for 6.35 and 3.81 mm thicknesses. Finite Element Analysis (FEA) was conducted, and using FEA results, Smith-Watson-Topper, Findley, …

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Examination Of Contact Width On Fretting Fatigue, Russell S. Magaziner Mar 2002

Examination Of Contact Width On Fretting Fatigue, Russell S. Magaziner

Theses and Dissertations

The primary goal of this study was to find the effects on the fretting fatigue life when systematically holding the fretting fatigue variables, peak contact pressure, maximum/minimum nominal bulk stress, and the ratio of shear traction to pressure force constant while varying the contact semi-width through changes in pad radius and normal load. Experimental tests were performed on a test setup capable of independent pad displacement. Analytical and finite element simulations of the different experimental tests were performed. The local mechanistic parameters were inspected. Five different critical plane based fatigue predictive parameters lacked effectiveness in predicting changes in life with …

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Computational Investigation Of Aeromechanical Hcf Effects In A Compressor Rotor, Andrew L. White Mar 2001

Computational Investigation Of Aeromechanical Hcf Effects In A Compressor Rotor, Andrew L. White

Theses and Dissertations

High-Cycle Fatigue is a major problem facing the gas turbine industry today. It has been investigated by many researchers, using many different methods. Due to its highly complex nature, designers still do not have adequate tools to accurately predict the onset of high-cycle fatigue. A three-dimensional Navier-Stokes program was used to perform a study of the unsteady aerodynamics on a compressor rotor. The effect of aerodynamic detuning on the forced response of a rotor blade was compared to a baseline tuned rotor case. Detuning consisted of a ten percent decrease in circumferential spacing between alternate pairs of blades. The high-cycle …

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Fatigue Response Of Thin Stiffened Aluminum Cracked Panels Repaired With Bonded Composite Patches, Jason B. Avram Mar 2001

Fatigue Response Of Thin Stiffened Aluminum Cracked Panels Repaired With Bonded Composite Patches, Jason B. Avram

Theses and Dissertations

This research investigated the fatigue response of precracked and patched 2024-T3 Aluminum panels with stiffeners. Patches were single-sided, unidirectional three ply boron/epoxy. Stiffeners were 2024-T3 aluminum and were riveted and bonded on. Disbonds were introduced into the repair bondline by inserting teflon strips. Three disbond configurations were investigated rack tip disbond (CTD) located at the edge of the patch in the path of crack propagation, full-width disbond (FWD) covering the entire crack, and end disbond (ED) located at each end of the patch and covering the full width. Each repaired panel was subjected to tension/tension cyclic fatigue with a maximum …

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Modification Of Position And Attitude Determination Of A Test Article Through Photogrammetry To Account For Structural Deformation, Sean A. Krolikowski Mar 2001

Modification Of Position And Attitude Determination Of A Test Article Through Photogrammetry To Account For Structural Deformation, Sean A. Krolikowski

Theses and Dissertations

This study improved the current method of position and attitude determination to account for structural deformation of the wind tunnel test article due to aerodynamic loading. To account for deformation, parabolic bending and linear twisting coefficients were added into the Levenberg-Marquardt multi-parameter solver. By accounting for deformation, the accuracy of position and attitude determination was greatly improved. This study also takes a qualitative look at the optimum number of wind tunnel cameras and model targets. Optimal configuration was found to be around 50 targets and 2 cameras offset by 90 degrees.

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The Development Of A Finite Element Program To Model High Cycle Fatigue In Isotropic Plates, William C. Shipman Mar 2001

The Development Of A Finite Element Program To Model High Cycle Fatigue In Isotropic Plates, William C. Shipman

Theses and Dissertations

As part of a joint AFRL/DAGSI turbine blade research effort, a computer program has been developed that uses a von Karman large-deflection two-dimensional finite element approximation to determine stress levels and patterns in isotropic thin plates. The dynamic loading of various plates has been carried out in order to model a high cycle fatigue situation. The research considered the various effects of mode shapes, resident frequency, non-linear cyclic effect, endurance limits, and stress variations within a high cycle fatigue environment. Two main initiatives were taken. First, a transient analysis tool was developed that calculates stress and displacement patterns over a …

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Finite Element Analysis Of A Composite Cylindrical Shell With A Cutout Under A Fatigue Load, Joshua T. Boatwright Mar 2000

Finite Element Analysis Of A Composite Cylindrical Shell With A Cutout Under A Fatigue Load, Joshua T. Boatwright

Theses and Dissertations

A higher-order shell theory is used to analyze compressive and tensile loads on a graphite/epoxy laminated cylinder containing a square cutout. The Hashin failure criterion is used to determine failure in the fiber, matrix, or lamination. Once failure occurs, the appropriate stiffness terms are reduced. This failure causes a redistribution of stress, leading to further failure. In order to account for the loss of residual strength due to cyclic loading, the stiffness matrix is further reduced at each new increment of load or displacement. The objective is not to determine the S-N curve for the material, but rather to determine …

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Mechanics Of A Functionally-Graded Titanium Matrix Composite, G. Brandt Miller Mar 2000

Mechanics Of A Functionally-Graded Titanium Matrix Composite, G. Brandt Miller

Theses and Dissertations

Functionally-graded Titanium Matrix Composites, (F/G TMCs) combine the ideal properties of titanium matrix composites with the more practical machining qualities of monolithic (unreinforced) alloy. This material shows great promise in application to aerospace structural components - even in parts whose design requirements have defied the use of composite materials in the past. Successful implementation of such a material would lead to enhanced aircraft performance. However, the basic properties of a functionally-graded titanium matrix composite need to be investigated. The composite/alloy transition region, or joint area, may be less strong than its constituents and therefore determine the overall performance of the …

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Monotonic And Fatigue Behavior Of 2-D Woven Ceramic Matrix Composite At Room And Elevated Temperatures (Blackglas/Nextel 312), Musa Al-Hussein Sep 1998

Monotonic And Fatigue Behavior Of 2-D Woven Ceramic Matrix Composite At Room And Elevated Temperatures (Blackglas/Nextel 312), Musa Al-Hussein

Theses and Dissertations

This study investigated the monotonic tension and compression and the tension-tension and tension-compression fatigue loading of Blackglas/Nextel 312 woven CMC at room temperature and at 760 degrees centigrade. Young's Modulus and strain variation were evaluated. S-N curves were obtained for room and elevated temperatures. The ultimate tensile stress was lower at the elevated temperature and it was higher in the compression test. Failure-strain was higher at the elevated temperature in both tension and compression tests. There was no significant change in Young's Modulus at the elevated temperature. Also, there was no difference in the number of cycles to failure at …

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Fatigue Behavior Of A Quasi-Isotropic Graphite/Epoxy Laminate Embedded With A Piezoelectric Sensor, Jon M. Coleman Dec 1997

Fatigue Behavior Of A Quasi-Isotropic Graphite/Epoxy Laminate Embedded With A Piezoelectric Sensor, Jon M. Coleman

Theses and Dissertations

This study primarily investigated the mechanical effects of embedding piezoelectric sensors on the tensile and fatigue strength of a quasi-isotropic, carbon-epoxy laminate. A secondary focus was the investigation of the sensor degradation under tensile loading. A [0 | ±45 | 90]s laminate was fabricated from Hercules AS4/3501-6 pre-preg tape. Specimens were first tested monotonically to obtain an average ultimate tensile strength and to detail the progression of damage. The fatigue tests were tension-tension, R=0.1, 10 Hz, constant amplitude. Results indicated that the embedded piezoelectric sensors did not have a significant effect on the tensile strength of the laminate. Specimens …

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Fiber Volume Fraction Effects On Fatigue Response Of A Scs-6/Ti-15-3 Metal Matrix Composite At Elevated Temperature, Sean C. Coghlan Sep 1997

Fiber Volume Fraction Effects On Fatigue Response Of A Scs-6/Ti-15-3 Metal Matrix Composite At Elevated Temperature, Sean C. Coghlan

Theses and Dissertations

The purpose of this study was to determine the effects of fiber volume fraction on the fatigue behavior of Silicon Carbide fiber-reinforced Titanium alloy, SCS-6/Ti-15-3. Three fiber volume fractions were investigated; 15%, 25%, and 42%. The tests were performed under fully-reversed, strain-controlled conditions at 427 °C. The primary objectives of this study were to develop a fatigue life diagram and to document the damage and failure mechanisms. Compressive loads on the slender specimens were kept from buckling the specimens through the use of a buckling guide. This device allows unrestricted axial movement of the composite, while preventing any out-of-plane motion. …

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Thickness Effects On A Cracked Aluminum Plate With Composite Patch Repair, Joel J. Schubbe Jun 1997

Thickness Effects On A Cracked Aluminum Plate With Composite Patch Repair, Joel J. Schubbe

Theses and Dissertations

Post-repair fatigue crack growth was investigated in 3.175, 4.826, and 6.35 mm thick aluminum panels asymmetrically repaired with boron/epoxy composite patches bonded to the plates with FM73 sheet adhesive. Patches were uniaxial with patch to panel stiffness ratios ranging from 0.46 to 1.3. Experimental fatigue tests were carried out at 120 MPa, R=0.1, and 10 Hz (sinusoidal) to measure patched and unpatched face crack lengths, center crack opening displacements, and selected strains. Crack growth data was acquired using optical, eddy current, and post-test analysis methods. Crack growth rates were calculated using the incremental polynomial method. A three-layer Mindlin plate finite …

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Residual Strength After Fatigue Of Unidirectional And Cross-Ply Metal Matrix Composites At Elevated Temperature, Sen-Tzer Chiou Jun 1996

Residual Strength After Fatigue Of Unidirectional And Cross-Ply Metal Matrix Composites At Elevated Temperature, Sen-Tzer Chiou

Theses and Dissertations

This study investigated the residual strength of the unidirectional and cross-ply laminates of SCS-6 / Ti-15-3, metal matrix composite at elevated temperature 427°C (800°F) after under tension-tension load controlled mode. For this purpose, several specimens were fatigued to various fractions of the fatigue life and then loaded monotonically to failure. The purpose of this study was to determine the effects of different levels of fatigue damage on the composite's strength. The unidirectional specimens were cycled at a 900 MPa maximum stress at a frequency of 10 Hz, while, the cross-ply specimens were tested at both 300 MPa and 450 MPa …

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Modeling Of Progressive Damage In Fiber-Reinforced Ceramic Matrix Composites, James P. Solti Mar 1996

Modeling Of Progressive Damage In Fiber-Reinforced Ceramic Matrix Composites, James P. Solti

Theses and Dissertations

An analytic methodology is developed to model the response of fiber-reinforced ceramic matrix composites (CMOs) when subjected to monotonic and fatigue loadings. The analysis requires the formulation of (1) a micromechanics model which defines the laminate's geometry and constitutive relationship; (2) failure criteria which estimate the extent of microstructural damage, and, finally, (3) a means of analyzing frictional slip, fiber pull-out, interfacial wear and laminate failure. For the present study, the behavior of unidirectional and crossply CMOs is investigated using modified shear-lag theory in conjunction with a set of failure criteria with a minimum reliance on empirical data. The damage …

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Investigation Of Residual Strength And Fatigue Life Of Unstiffened Aluminum Panels With Multiple Site Damage, Mark C. Cherry Dec 1995

Investigation Of Residual Strength And Fatigue Life Of Unstiffened Aluminum Panels With Multiple Site Damage, Mark C. Cherry

Theses and Dissertations

Multiple Site Damage MSD is the occurrence of small fatigue cracks at several sites within aircraft structures. This is important since it may lower the residual strength and fatigue life of the structure beyond what can be predicted using the damage tolerance technique based on a single crack, currently in use to design aircraft structures. This study investigated the effects of MSD on unstiffined panels. MSD usually occurs at rivet holes, or other stress concentration locations within an aircraft structure. This study simulated rivet holes with MSD, by using holes of constant diameter with small cracks, evenly spaced across the …

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Thermo-Mechanical Fatigue Behavior Of Cross-Ply Ceramic Matrix Composite Under Tension-Tension Loading, Dana G. Allen Dec 1995

Thermo-Mechanical Fatigue Behavior Of Cross-Ply Ceramic Matrix Composite Under Tension-Tension Loading, Dana G. Allen

Theses and Dissertations

The purpose of this study was to investigate the combined effect of cyclic temperature and loading on the fatigue life of a ceramic matrix composite with a cross ply lay-up. The material used in this study was a potassium borosilicate glass (BSG) doped magnesium aluminosilicate (MAS) cordierite matrix reinforced with Nicalon (silicon carbide, SiC) fibers in a [0/90]4s lay-up. Thermomechanical fatigue (TMF) tests were performed with a period of 180 seconds/cycle, or 0.00556 Hz, and a triangular wave-form. The temperature was cycled between 566°C and l093°C, and the stress levels varied between 60 MPa and 145 MPa. All tests …

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Thermal Stresses In End-Heated Layered Media, Jerry R. Couick Dec 1995

Thermal Stresses In End-Heated Layered Media, Jerry R. Couick

Theses and Dissertations

Thermal stresses in semi-infinite layered beams heated on the end are calculated using an extension to simple bimetallic thermostat theory. Recently, researchers have used the concept of interfacial compliance to determine interlaminar stresses in a simple thermostat of finite length subjected to a uniform temperature increase. In the present work, the thermostat theory is extended to apply to the beams of interest. A closed-form solution to the problem is obtained. It is not applicable within about one beam thickness (St Venant boundary region) of the end. Various classes of layered materials are analyzed to determine if significant stresses exist outside …

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Fatigue Response Of Cracked Aluminum Panel With Partially Bonded Composite Patch, Jason J. Denney Dec 1995

Fatigue Response Of Cracked Aluminum Panel With Partially Bonded Composite Patch, Jason J. Denney

Theses and Dissertations

More and more aircraft, both commercial and military, are being called upon to fly well beyond their economic and structural service lives. Budget cuts and dwindling new aircraft development has forced the United States Air Force (USAF) to look toward more reliable structural repairs. One of these repair techniques, which was the subject of this study, is the repair of metallic aircraft structures using high strength composite materials. This study investigated the fatigue response of a precracked, 508x1 52x1 mm, 2024-T3 aluminum panel repaired with a partially bonded, unidirectional, three-ply boron/epoxy composite reinforcement with ply lengths of 68, 56 and …

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Nonlinear Geometric And Material Behavior Of Composite Shells With Large Strains, Scott A. Schimmels Aug 1995

Nonlinear Geometric And Material Behavior Of Composite Shells With Large Strains, Scott A. Schimmels

Theses and Dissertations

A two-dimensional, geometrically and materially nonlinear shell theory applicable to arbitrary geometries described by orthogonal curvilinear coordinates and encompassing large displacements, moderate rotations for large strain situations has been developed. Additionally, the theory includes Jacobian transformation matrices, based upon displacement parameters, for the Cauchy - 2nd Piola-Kirchhoff stress-state and the Cauchy (Almansi) - Green strain-state transformations, and a layered material approach is included for the elastoplastic analysis to allow for variation of plasticity through-the-thickness. Doubly curved 20, 28, and 36 degree-of-freedom finite elements are defined based on specialization of the theory to spherical coordinates. The computer program includes algorithms for …

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Investigation Into The Behavior Of Geometrically Nonlinear Composite Arches, John C. Bailey Dec 1994

Investigation Into The Behavior Of Geometrically Nonlinear Composite Arches, John C. Bailey

Theses and Dissertations

This research modifies the existing finite element formulation of a potential energy based large deformation and moderate rotation theory. Hermitian shape functions replace the existing linear bending angle interpolations. Negligible differences between the two formulations indicate the underlying kinematics limit the accuracy, not the finite element interpolations. Using the new program, numerous nonlinear arch geometries are modeled to investigate the effects of arc length and thickness variations. Local and global snapping phenomena are captured as well as through the thickness shear driven nonlinearities.

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Viscoplastic Characterization And Fatigue Modeling Of Titanium Based Metal Matrix Composites, Mark A. Foringer Dec 1994

Viscoplastic Characterization And Fatigue Modeling Of Titanium Based Metal Matrix Composites, Mark A. Foringer

Theses and Dissertations

Viscoplastic characterization and fatigue modeling of titanium-based metal matrix composites was accomplished by combining a unified viscoplastic theory, a nonlinear micromechanics model, and a linear damage accumulation model. First. Ti 15-3 was characterized using the Bodner-Partom viscoplastic theory. A micromechanics model was then employed in a linear damage accumulation fatigue model to predict the fatigue behavior of titanium based composites. The viscoplastic behavior predictions of the micromechanics model were used to eliminate separately defined time dependent terms in the fatigue model. Also, a new linear damage accumulation model was developed from the fatigue behavior of the composite constituents. Finally, it …

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Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite At Elevated Temperature Under Tension-Tension Loading, Craig D. Steiner Dec 1994

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite At Elevated Temperature Under Tension-Tension Loading, Craig D. Steiner

Theses and Dissertations

This study investigated the fatigue behavior and damage mechanisms of a [0-90]4s SiC-MAS ceramic matrix composite under tension-tension loading at two elevated temperatures and two frequencies. Stress and strain hystereses, maximum and minimum strain, and modulus of elasticity were evaluated to characterize the material behavior. Microscopy and fractography were used to evaluate damage progression and mechanisms. Fatigue life was independent of frequency at both temperatures.

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Investigation Of Tension-Compression Fatigue Behavior Of A Unidirectional Metal Matrix Composite At Elevated Temperature, Darren L. Kraabel Dec 1994

Investigation Of Tension-Compression Fatigue Behavior Of A Unidirectional Metal Matrix Composite At Elevated Temperature, Darren L. Kraabel

Theses and Dissertations

This study investigated the fatigue behavior in a unidirectional metal matrix composite under tension-compression loading conditions. Stress-strain responses, modulus and strain trends were monitored to characterize damage. Fractography and microscopy were used to characterize failure modes. Fatigue life curves were plotted base on different parameters such as stress and strain. Tension-compression fatigue life was shorter than the obtained under tension-tension fatigue cycling. Creep, observed in tension-tension. fatigue cycling, and the effects of the compressive load on the plastic zone around the crack tip explain shorter life under tension-compression fatigue loading.

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Fatigue Behavior Of A Cross-Ply Metal Matrix Composite At Elevated Temperature Under Strain Controlled Mode, Leon B. Dennis Dec 1994

Fatigue Behavior Of A Cross-Ply Metal Matrix Composite At Elevated Temperature Under Strain Controlled Mode, Leon B. Dennis

Theses and Dissertations

This research extends the existing knowledge of cross-ply metal matrix composites (MMC) to include fatigue behavior under strain-controlled fully reversed loading. This study investigated fatigue life, failure modes and damage mechanisms of the SCS-6-Ti-15-3, [O-9O]2s, MMC. The laminate was subjected to fully reversed fatigue at elevated temperature (427° C) at various strain levels. Stress, strain and modulus data were analyzed to characterize the macro-mechanical behavior of the composite. Microscopy and fractography were accomplished to identify and characterize the damage mechanisms at the microscopic level. Failure modes varied according to the maximum applied strain level showing either mixed mode …

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Characterization Of Fatigue Behavior Of 2-D Woven Fabric Reinforced Ceramic Matrix Composite At Elevated Temperature, Daniel J. Groner Dec 1994

Characterization Of Fatigue Behavior Of 2-D Woven Fabric Reinforced Ceramic Matrix Composite At Elevated Temperature, Daniel J. Groner

Theses and Dissertations

This study investigated the fatigue behavior and associated damage mechanisms in notched and unnotched enhanced Sic-SiC ceramic matrix composite specimens at 1100°C. Stiffness degradation, strain variation, and hysteresis were evaluated to characterize material behavior. Microscopic examination was performed to characterize damage mechanisms. During high cycle-low stress fatigue tests, far less fiber-matrix interface debond was evident than in low cycle-high stress fatigue tests. Notched specimens exhibited minimal stress concentration during monotonic tensile testing and minimal notch sensitivity during fatigue testing. Damage mechanisms were also similar to unnotched.

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Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Subjected To Tension-Tension Cycling With Hold Time, Scott A. Grant Dec 1994

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Subjected To Tension-Tension Cycling With Hold Time, Scott A. Grant

Theses and Dissertations

This study was carried out to investigate the elevated temperature behavior of the SiC-MAS5 cross- ply [0-90]4S ceramic matrix composite manufactured by Corning Inc. to fatigue with loading waveforms that combine the characteristics of stress rupture and high cycle fatigue. The test results were compiled in the form of S-N (cycles to failure), S-T (exposure time versus cycles to failure), S-S (energy exposure versus cycles to failure), normalized modulus degradation, strain progression, and hysteresis loop progression. From the mechanical behavior demonstrated by these curves, relationships between the effect of the environment and loading waveform were developed. In addition, a …

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Investigation Of Tension-Compression Fatigue Behavior Of A Notched Cross-Ply Metal Matrix Composite At Elevated Temperature, Matthew W. Yocum Dec 1994

Investigation Of Tension-Compression Fatigue Behavior Of A Notched Cross-Ply Metal Matrix Composite At Elevated Temperature, Matthew W. Yocum

Theses and Dissertations

This research extends the existing knowledge of MMC fatigue damage mechanisms by studying the tension-compression fatigue behavior of a notched cross-ply laminate MMC at elevated temperature. A [0-90]2S SCS-6-Ti-15-3 laminate with a center hole was subjected to tension-compression fatigue at 427 °C (800 °F). Stress and strain data was taken to evaluate macro-mechanic behavior of the material. Microscopy and fractography were performed to characterize the damage on a micro-mechanical level. Crack initiation and progression was monitored using acetate face replicas. Four cracks were found to develop around the periphery of the hole, two of which became dominant and proceeded …

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Design And Analysis Of Constrained Layer Damping Treatments For Bending And Torsion, Kimberly J. Balkema Sep 1994

Design And Analysis Of Constrained Layer Damping Treatments For Bending And Torsion, Kimberly J. Balkema

Theses and Dissertations

In this dissertation, different aspects of constrained layer damping treatments on beams of various geometries are studied. First, the optimal length of a constrained layer damping treatment mounted on a surface in linear strain is identified as a function of the relative stiffnesses of the damping layers and the non-uniformity of the surface stain. The analysis extends previous work that considered the case of uniform surface strain. Sixth order sandwich beam theory is then modified for use with a rectangular beam covered with a segmented constrained layer damping treatment. Non-dimensional variables are used to simplify the form of the problem. …

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Simultaneous Design Of Active Vibration Control And Passive Damping, Michele Lynn Devereaux Gaudreault Dec 1993

Simultaneous Design Of Active Vibration Control And Passive Damping, Michele Lynn Devereaux Gaudreault

Theses and Dissertations

A modified form of the standard linear quadratic regulator LQR cost functional is used to optimally blend active vibration control and passive structural damping, whether viscous or viscoelastic. Viscoelastic damping is first modelled by a standard linear model, and then by a fractional derivative model. For the viscous damping case and the classically modelled viscoelastic damping case, a sub-optimal closed form solution is derived that is independent of the initial conditions. An iterative technique that minimizes the average value of the cost functional and one that minimizes the maximum value are developed. Both techniques are applicable to viscous and viscoelastic …

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