| High Strain Rate Mechanical Properties of Glassy Polymers |
25 Jul 2012 |
11 pages |
| Authors:
Jennifer L Jordan; C R Siviour; B T Woodworth; AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
|
 | Since the early 1990s, a range of experimental data has been generated describing the response of glassy polymers to high strain rate loading in compression. More recently, research programs that study the combined effects of temperature and strain rate have made significant steps in providing better understanding of the physics behind the observed response, and also in modeling this response. However, limited data are available in tension, and even more ... |
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| Growth Stress in Si02 Formed by Oxidation of SiC (Preprint) |
Jul 2012 |
8 pages |
| Authors:
Randall S Hay; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
|
| Growth stresses in amorphous SiO2 scales formed during SiC fiber oxidation were calculated. A numerical method using Deal-Grove oxidation kinetics and shear-stress dependent SiO2 viscosity was used. Initial compressive stresses in SiO2 of 25 GPa from the 2.2? oxidation volume expansion rapidly relaxes. At 1200?, viscous flow of amorphous SiO2 further relaxes stress to negligible levels. At 700? - 900?C, axial and hoop stress at the GPa level persist in ... |
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| Clustering Theory and Applications |
Apr 2012 |
23 pages |
| Authors:
H T Kung; CREATIVE STEP LLC BELMONT MA
|
| The report describes the theory for recovering information from sparse signal representations in distributed sensing applications. This theory is useful in streamlining networking and decoding operations over bandwidth constrained wireless networks. Using these results, we can for example transport and store a single combined measurement set, rather than multiple sets from all sensors. We show that via source separation and joint decoding, it is possible to recover information about the ... |
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| Dynamic Compressibility, Shear Strength, and Fracture Behavior of Ceramic Microstructures Predicted from Mesoscale Models |
Apr 2012 |
12 pages |
| Authors:
John D Clayton; R B Leavy; Reuben H Kraft; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| Fundamental understanding of dynamic behavior of polycrystalline ceramics is advanced through constitutive theory development and computational modeling. At the mesoscale, microstructures of silicon carbide grains (hexagonal crystal structure) or aluminum oxynitride grains (cubic crystal structure) are subjected to compression or shear at high rates with varying confining pressure. Each grain is resolved by numerous three-dimensional finite elements, and behavior of each grain is modeled using nonlinear anisotropic elasticity. Cohesive fracture ... |
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| Sound Speed and Attenuation in Multiphase Media |
15 Mar 2012 |
14 pages |
| Authors:
William M Carey; BOSTON UNIV MA DEPT OF MECHANICAL ENGINEERING
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| This report discusses an investigation of the sound speed and attenuation in multiphase media, sandy and muddy sediments, that has shown that a simplified-Biot theory adequately predicts the sound speed and attenuation in sandy sediments with porosities of less than 65%. In addition for muddy sediments with porosities of greater than 70% mixture theory can describe the sound speed. This report discusses the experimental and theoretical basis for these conclusions ... |
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| Thermal Mechanical Fatigue Cracks Growth from Laser Drilled Holes in Single Crystal Material (Preprint) |
Mar 2012 |
24 pages |
| Authors:
R K Kersey; A Staroselsky; D C Dudzinski; M Genest; PRATT AND WHITNEY EAST HARTFORD CT
|
| The crack growth test results undergoing thermomechanical fatigue showed that the life of TMF specimens with notched laser drilled holes exhibit a debit by as much as 4 times that of smooth gage section specimens under the same loading conditions. Such a significant change in number of cycles to failure must be accounted in any damage tolerant design system. The detailed fractographic analysis demonstrated that the all cracks start crystallographically ... |
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| Structural Technology Evaluation Analysis Program (STEAP). Task Order 0029: Thermal Stability of Fatigue Life-Enhanced Structures |
Jan 2012 |
108 pages |
| Authors:
Vijay K Vasudevan; Dong Qian; S R Mannava; Gokul Ramakrishnan; Vibhor Chaswal; Amrinder Gill; Zhong Zhou; Sagar Bhamare; CINCINNATI UNIV OH
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| This work combines process parameter variations, finite element (FE) modeling and simulations, characterization, and mechanical testing in a study of the effects of laser shock peening (LSP) on residual stress and microstructure evolution, thermal stability thereof, and fatigue behavior of high-temperature aerospace structural alloys ( Ti-64, Ti-6242, IN718 SPF and IN718 Plus). The aim was to secure a quantified knowledge of the impact of process parameters and high-temperature exposures on ... |
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| Study of the Progressive Failure of Composites under Axial Loading with Varying Strain Rates |
Dec 2011 |
79 pages |
| Authors:
Yew K Boey; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| This study investigated the progressive damage/failure of composite panels with open circular holes under progressive axial loading. A series of experiments was carried out to determine the failure in laminated specimens with and without circular holes under tensile and compressive loads, respectively. Different strain rate loading was applied to observe the rate effect on the damage initiation and propagation. Both uniform and non-uniform strain rate loads were applied to the ... |
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| The Use of Natural Pozzolan in Concrete as an Additive or Substitute for Cement |
Dec 2011 |
101 pages |
| Authors:
Ghassan K Al-Chaar; Mouin Alkadi; David A Yaksic; Lisa A Kallemeyn; ENGINEER RESEARCH AND DEVELOPMENT CENTER CHAMPAIGN IL CONSTRUCTION ENGINEERING RESEARCH LAB
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| Chemical, physical, and mechanical tests were conducted to assess the feasibility of using naturally occurring pozzolan as a ce-ment mortar additive. One test series assessed the feasibility of substituting pozzolan for a portion of cement in concrete mortar mixtures. The chemical composition of five natural pozzolans was determined. Compressive testing was conducted on specimens with varying amounts and types of pozzolan. One pozzolan was found suitable for cement replacement in ... |
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| Laminated Composite Sandwich Plates with a Weak Compressible Core Impacted by Blast Loading |
03 Nov 2011 |
39 pages |
| Authors:
Terry Hause; Sudhakar Arepally; ARMY TANK AUTOMOTIVE RESEARCH DEVELOPMENT AND ENGINEERING CENTER WARREN MI
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| The governing theory of asymmetric sandwich plates with a first-order compressible core impacted by a Friedlander-type of blast has been presented and simplified for the case of symmetric cross-ply and single-layered orthotropic facings. In all cases, it was mentioned that all four edges are simply supported and freely movable. Results were then presented for this simplified case and validated against results found in the literature from R. S. Alwar et ... |
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| Mechanics of Granular Materials: Experimentation and Simulations for Determining the Compressive and Shear Behaviors of Sand at Granular and Meso Scales |
30 Sep 2011 |
83 pages |
| Authors:
Ranga Komanduri; Hongbing Lu; Vijay Subramanian; Huiyang Luo; Fang Wang; William L Cooper; OKLAHOMA STATE UNIV STILLWATER SCHOOL OF MECHANICAL AND AEROSPACE ENGINEERING
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| We present the results of experiments conducted to study the compressive and shear behavior of sand. Static and dynamic studies on the compression of sand grains were conducted. Nanoindentation was performed on single grains on sand of different sizes in order to determine the elastic and fracture properties of individual sand grains. Finite Element method (FEM) was used to solve the inverse problem so as to obtain the material properties ... |
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| Damage Development in Confined Borosilicate and Soda-Lime Glasses |
11 Jul 2011 |
35 pages |
| Authors:
Kathryn A Dannemann; Jr Anderson Charles E; Sidney Chocron; James F Spencer; SOUTHWEST RESEARCH INST SAN ANTONIO TX
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| Post-test microscopy evaluations were performed on borosilicate (Borofloat (registered trademark) 33) and soda-lime (Starphire (registered trademark)) glass specimens following confined compression tests. These included optical and electron microscopy investigations of select specimens tested at low strain rates with confinement pressures up to 1 GPa. Specimens were evaluated following removal of the confinement sleeve or holder. The objective of this work was to investigate the flow and failure behavior of both ... |
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| Establishment of Maximum Voluntary Compressive Neck Tolerance Levels |
Jul 2011 |
|
| Authors:
Michael Cote; John Buhrman; Nathaniel Bridges; Casey Pirnstill; Chris Burneka; John Plaga; Grant Roush; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH HUMAN PERFORMANCE WING (711TH) BIOSCIENCES AND PERFORMANCE DIV/VULNERABILITY ANALYSIS BRANCH
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| The primary objective of this study was to establish maximum human voluntary static tolerance levels of neck compressive loading to ensure the safe operation of a proposed Joint Strike Fighter (JSF) Head/Neck Restraint System (HNRS). A laboratory helmet-load apparatus was designed and used to safely apply compressive forces to the head/neck of 46 subjects' (26 female; 20 male). Nearly all subjects were able to sustain maximum forces of at least ... |
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| Microstructure and Room Temperature Properties of a High-Entropy TaNbHfZrTi Alloy (Preprint) |
Jul 2011 |
19 pages |
| Authors:
O N Senkov; J M Scott; S V Senkova; D B Miracle; C F Woodward; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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| A refractory alloy, Ta20Nb20Hf20Zr20Ti20, was produced by vacuum arc-melting. The as-solidified alloy had a dendritic structure, which was not affected by hot isostatic pressing (HI Ping) conducted at T = 1200 deg C and p = 207 MPa for 3 hours. The alloy had a single-phase body-centered cubic (BCC) structure with the lattice parameter a= 340.44 pm. The alloy density and Vickers microhardness after HIPing were p = 9.94 g/cm3 ... |
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| The Duality of Fracture Behavior in a Ca-Based Bulk-Metallic Glass (Preprint) |
Jul 2011 |
15 pages |
| Authors:
Gongyao Wang; Peter K Liaw; Oleg N Senkov; Daniel B Miracle; TENNESSEE UNIV KNOXVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| Ca65Mg15Zn20 bulk-metallic glass (BMG) exhibited a typical brittle fracture behavior during compressive loading at room temperature. Samples exploded into many small pieces after elastic deformation, and no macroscopic plasticity was observed. The fracture surface demonstrated multiple fracture patterns, including typical metallic-glass vein patterns and glass mirror, mist, and hackle patterns. These observations show that Ca-based BMGs are subjected to multiple brittle fracture modes under compressive loading. Periodic nanoscale corrugations were ... |
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| Mechanical Properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 Refractory High-Entropy Alloys (Preprint) |
Jul 2011 |
24 pages |
| Authors:
D B Miracle; O N Senkov; J M Scott; G B Wilks; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIR METALS CERAMICS AND NONDESTRUCTIVE EVALUATION DIV/METALS BRANCH
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| Two refractory high entropy alloys with concentrations near Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20, were produced by vacuum arc-melting. Despite containing many constituents both alloys had a single-phase body-centered cubic (BCC) structure that remained stable after exposure to 1400 deg C. Compression properties of the alloys were determined in the temperature range of room temperature to 1600 deg C. Limited compressive plasticity and quasi-cleavage fracture at room temperature suggests that the ductile-to-brittle transition ... |
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| Analytical Solution for Flexural Response of Epoxy Resin Materials |
23 JUN 2011 |
36 pages |
| Authors:
Masoud Y. Fard; Yingtao Liu; Aditi Chattopadhyay; ARIZONA STATE UNIV TEMPE
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| A multilinear parametric uniaxial stress strain approach has been used to obtain the closed form nonlinear moment curvature response based on strain compatibility in bending for epoxy resin materials. The stress strain curves, consisting of a bilinear ascending curve followed by strain softening and constant plastic flow in tension and compression, are described by two main parameters in addition to five non-dimensional tensile and seven non-dimensional compressive parameters. The main ... |
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| Laser Peening for Mitigation of Stress Corrosion Cracking at Welds in Marine Aluminum |
JUN 2011 |
77 pages |
| Authors:
Heather R. Mattern; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| This work examines the use of laser peening (LP) for mitigation of stress corrosion cracking (SCC) in marine grade aluminum alloys (Al-Mg). These alloys can be sensitized during welding and will develop a tensile residual stress in the heat affected zone that may promote SCC in a salt water environment. Metal inert gas welded aluminum alloy 5083 (4.8wt% Mg) plate was laser peened using a variety of laser intensities to ... |
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| Analyzing and Improving Image Quality in Reflective Ghost Imaging |
FEB 2011 |
95 pages |
| Authors:
Nicholas D. Hardy; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
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| Ghost imaging is a transverse imaging technique that relies on the correlation between a pair of light fields, one that has interacted with the object to be imaged and one that has not. Most ghost imaging experiments have been performed in transmission. and virtually all ghost imaging theory has addressed the transmissive case. Yet stand-off sensing applications require that the object be imaged in reflection. We use Gaussian-state analysis to ... |
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| Analytical Solutions for Predicting Underwater Explosion Gas Bubble Behaviour |
NOV 2010 |
46 pages |
| Authors:
Mark Riley; DEFENCE RESEARCH AND DEVELOPMENT ATLANTIC DARTMOUTH (CANADA)
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| This study describes different analytical models that have previously been developed for predicting the radial growth and collapse of underwater explosion (UNDEX) gas bubbles in a free-field environment. The report describes the implementation of nine analytical gas bubble models, in the form of nonlinear differential equations, and a fourth-order Runge-Kutta solution method. Gas bubble radius time histories calculated with these models are compared to empirical models derived from published experimental ... |
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| Statistical Compressive Sensing of Gaussian Mixture Models |
OCT 2010 |
6 pages |
| Authors:
Guoshen Yu; Guillermo Sapiro; MINNESOTA UNIV MINNEAPOLIS INST FOR MATHEMATICS AND ITS APPLICATIONS
|
| A new framework of compressive sensing (CS), namely statistical compressive sensing (SCS), that aims at efficiently sampling a collection of signals that follow a statistical distribution and achieving accurate reconstruction on average, is introduced. For signals following a Gaussian distribution with Gaussian or Bernoulli sensing matrices of O(k) measurements considerably smaller than the O(k log(N/k)) required by conventional CS where N is the signal dimension, and with an optimal decoder ... |
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| Influence of the Third Invariant in the Ballistic Impact of Silicon Carbide |
06 Aug 2010 |
42 pages |
| Authors:
Stephen Beissel; Timothy Holmquist; Gordon Johnson; SOUTHWEST RESEARCH INST MINNEAPOLIS MN
|
| This report examines the dependence of the ballistic performance of silicon carbide on the third invariant of the stress tensor by use of numerical simulations and test data. The JHB ceramic model is modified to account for the influence of the third invariant, and the modification includes a material parameter defined as the ratio of yield in tri-axial extension to yield in tri-axial compression. Simulations of high-velocity impact are performed ... |
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| Predicting Snap-through of a Thin-walled Panel due to Thermal and Acoustic Loads |
May 2010 |
16 pages |
| Authors:
R S Miskovish; Parthiv Shah; Stephen M Spottswood; ATA ENGINEERING INC SAN DIEGO CA
|
| Under contract from Wright-Patterson AFB (WPAFB), ATA Engineering, Inc., (ATA) has performed a study of snap-through buckling of a panel on a hypersonic vehicle under the influence of fluctuating pressures. Snap-through occurs when the elastic stiffness of the structure is cancelled by the effects of compressive stress within the structure. If this effect causes the structure to suddenly displace a large amount in a direction normal to the load direction ... |
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| Elastic Stress Analysis of Advanced Functionally Graded Plates Impacted by Blast Loading |
18 Jan 2010 |
38 pages |
| Authors:
Terry Hause; ARMY TANK AUTOMOTIVE RESEARCH DEVELOPMENT AND ENGINEERING CENTER WARREN MI
|
| The foundation of the theory of functionally graded plates with all four edges simply supported, under a Friedlander explosive spherical air-blast, is developed, within the classical plate theory (CPT). The constituent materials, ceramic and metal, vary across the wall thickness according to a prescribed power law. The theory incorporates the geometrical nonlinearities, the dynamic effects, compressive/tensile edge loadings, damping effects, and the structural symmetries (symmetric and asymmetric). The static and ... |
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| Feature Modeling in Underwater Environments Using Sparse Linear Combinations |
Jan 2010 |
9 pages |
| Authors:
Kenton Oliver; Weilin Hou; Song Wang; NAVAL RESEARCH LAB STENNIS DETACHMENT STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
|
| Feature matching is a key, underlying component in many approaches to object detection, localization, and recognition In many cases, feature matching is accomplished by nearest neighbor methods on extracted feature descriptors This methodology works well for clean, out-of-water images, however, when imaging underwater, even an image of the same object can be drastically different due to varying water conditions. As a result, descriptors of the same point on an object ... |
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| Hybrid LES of Detonations in Reacting Multi-Phase Mixtures |
28-Feb-2009 |
166 pages |
| Authors:
Suresh Menon; Franklin Genin; GEORGIA INST OF TECH ATLANTA SCHOOL OF AEROSPACE ENGINEERING
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| A Large-Eddy Simulation (LES) methodology adapted to the resolution of high Reynolds number turbulent flows in supersonic conditions was proposed and developed. A novel numerical scheme was designed, that switches from a low-dissipation central scheme for turbulence resolution to a flux difference splitting scheme in regions of discontinuities. A state-of-the-art closure model was extended in order to take compressibility effects and the action of shock / turbulence interaction into account. ... |
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| Evaluation of the StressWave Cold Working (SWCW) Process on High-Strength Aluminum Alloys for Aerospace |
Feb-2009 |
61 pages |
| Authors:
Eric T Easterbrook; Michael A Landy; STRESSWAVE INC KENT WA
|
| This report was developed under a SBIR contract. A new and innovative cold working process called StressWave Cold Working (SWCW) was investigated and compared to the conventional split sleeve cold working method that is used to enhance the fatigue life of fastener holes in high strength aluminum alloys used on USAF aircraft structures. StressWave cold working was found to be superior in enhancing fatigue lives compared to split sleeve cold ... |
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| Dynamic Failure Processes Under Confining Stress in AlON, a Transparent Polycrystalline Ceramic |
Dec-2008 |
9 pages |
| Authors:
James W McCauley; B Paliwal; K T Ramesh; Mingwei Chen; SANDIA NATIONAL LABS ALBUQUERQUE NM
|
| An experimental technique is developed to impose a planar lateral confinement in a prismatic specimen (with rectangular cross-section); the setup enabled a controlled and homogeneous stress state with high lateral compressive stresses. A transparent polycrystalline aluminum oxynitride (AlON) specimen was used for the study. The statically pre-compressed specimen was then subjected to axial dynamic compressive loading using a modified compression Kolsky bar setup. Experimental design was performed using 3D computational ... |
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| Mechanical Response of an Al-PTFE Composite to Uniaxial Compression Over a Range of Strain Rates and Temperatures |
01-Sep-2008 |
28 pages |
| Authors:
Daniel T Casem; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| Compressive stress-strain curves were generated for a pressed and sintered mixture of polytetrafluoroethylene and aluminum powders. Experiments were performed at strain rates ranging from 0.001 to 8000/s using a servo-hydraulic load frame and a split Hopkinson pressure bar. High-rate experiments were also performed over a temperature range of 22-78 C. The data is fit to the Johnson-Cook and Modified Johnson-Cook constitutive equations and also to a Zerilli-Armstrong equation adapted for ... |
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| A Coupled Creep Plasticity Model for Residual Stress Relaxation of a Shot Peened Nickel-Base Superalloy (Postprint) |
Sep-2008 |
12 pages |
| Authors:
Reji John; Dennis J Buchanan; Robert A Brockman; Andrew H Rosenberger; DAYTON UNIV OH RESEARCH INST
|
| Shot peening is a commonly used surface treatment process that imparts compressive residual stresses into the surface of metal components. Compressive residual stresses retard initiation and growth of fatigue cracks. During the component loading history, loading, or during elevated temperature static loading, such as thermal exposure and creep. In these instances, taking full credit for compressive residual stresses would result in a methodical approach for characterizing and modeling residual stress ... |
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| Quasistatic and Dynamic Growth of Microscale Spherical Voids (Preprint) |
Jan-2008 |
42 pages |
| Authors:
T C Tszeng; BERKELEY MATERIALS RESEARCH PIEDMONT CA
|
| This study examines the quasistatic and dynamic growth of microscale spherical voids. A general dynamic model of void growth is first developed by considering conservation of local energy, including external work, surface energy, kinetic energy, elastic strain energy, and plastic dissipation associated with growing void driven by hydrostatic tensile stress. It properly accounts for material compressibility and limited size of elastic deformation in dynamic growth of spherical voids. A closed ... |
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| Influence of Residual Stresses on Fretting Fatigue Life Prediction in Ti-6Al-4V |
Jan-2008 |
28 pages |
| Authors:
Patrick J Golden; Dennis Buchanan; Sam Naboulsi; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
|
| The objective of this work was to evaluate life prediction methodologies involving fretting fatigue of turbine engine materials with advanced surface treatments. Fretting fatigue tests were performed on Ti-6Al-4V dovetail specimens with and without advanced surface treatments. These tests were representative of the conditions found in a turbine engine blade to disk attachment. Laser shock processing and low plasticity burnishing have been shown to produce deep compressive residual stresses with ... |
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| Influence of Residual Stresses on Fretting Fatigue Life Prediction in Ti-6Al-4V (POSTPRINT) |
Jan-2008 |
14 pages |
| Authors:
Patrick J Golden; Dennis Buchanan; Sam Naboulsi; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
|
| The objective of this work was to evaluate life prediction methodologies involving fretting fatigue of turbine engine materials with advanced surface treatments. Fretting fatigue tests were performed on Ti-6Al-4V dovetail specimens with and without advanced surface treatments. These tests were representative of the conditions found in a turbine engine blade to disk attachment. Laser shock processing and low plasticity burnishing have been shown to produce deep compressive residual stresses with ... |
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| Continuum Modeling of Interface Failure |
DEC 2007 |
55 pages |
| Authors:
Robert P. Griffiths; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Two-dimensional continuum modeling and simulations were conducted to predict how the size, quantity, and stiffness of reinforcing particles such as carbon nanotubes (CNTs) affect failure mechanisms at the interface of composite structures. First, the strength model used the finite element method (FEM) on a slender composite beam with step-joint containing reinforcing particles to predict its critical stress-strain behavior at the joint interface under compressive axial load. Next, the fracture mechanics ... |
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| An Experimental Investigation Into The Effect Of Plasma On The Flow Features Of An Axisymmetric Jet |
OCT 2007 |
387 pages |
| Authors:
Richard E. Huffman; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
|
| The main goal of the research presented was to determine the differences between a plasma field and neutral field flow structure (both mean and turbulent effects) for varying Mach number. The overall objective was to describe the effect of radio frequency capacitively coupled plasma on the flow features of compressible axisymmetric jets in Nitrogen. Three flows were investigated: perfectly expanded jets, highly underexpanded jets, and jets created by a constant-diameter ... |
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| Extracting Stress-Strain and Compressive Yield Stress Information from Spherical Indentation |
SEP 2007 |
24 pages |
| Authors:
Thomas F. Juliano; Mark R. VanLandingham; Tusit Weerasooriya; Paul Moy; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| In recent years, instrumented indentation has become increasingly used to measure mechanical properties such as elastic modulus and fracture toughness at the micrometer scale. In this work, an experimental method is developed to estimate stressstrain behavior using indentation load-displacement and continuous stiffness measurement data. An attempt is made to subtract plastic behavior out of the loading curve to generate stress-strain data from which elastic modulus and yield stress can be ... |
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| Mechanical Properties of G-10 Glass-Epoxy Composite |
08 AUG 2007 |
12 pages |
| Authors:
K. Ravi-Chandar; S. Satapathy; TEXAS UNIV AT AUSTIN INST FOR ADVANCED TECHNOLOGY
|
| The mechanical properties of G10 glass-epoxy composites were determined in compression and tension tests. |
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| Compressive Properties of Extruded Polytetrafluoroethylene |
JUL 2007 |
14 pages |
| Authors:
Jennifer L. Jordan; Jason R. Foley; Clive R. Siviour; Eric N. Brown; AIR FORCE RESEARCH LAB EGLIN AFB FL MUNITIONS DIRECTORATE
|
| Polymers are becoming increasingly used in aerospace structural applications, where they experience complex, non-static loads. Correspondingly, the mechanical properties at high strain rates are of increasing importance in these applications. This paper presents an investigation of the properties of Dupont 9B polytetrafluoroethylene (PTFE) across strain rates from 10-3 to 10 5 s-1 (see paper). The samples were tested using an Instron mechanical testing machine for static loading, traditional split Hopkinson ... |
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| Mixing and Evaporation of Multiple Size Group JP-7 Fuel Droplets Injected into a Supersonic Air Stream - Efficiency of Cylindrical versus Rectangular Combustion Chamber |
03 May 2007 |
43 pages |
| Authors:
Fadl H Moukalled; AMERICAN UNIV BEIRUT (LEBANON)
|
| This report deals with the formulation, implementation, and testing of three numerical techniques based on (i) a full multiphase approach, (ii) a MUlti-SIze Group (MUSIG) approach, and (iii) a Heterogeneous MUSIG (H-MUSIG) approach for the prediction of mixing and evaporation of liquid droplets injected into a stream of air flowing inside a combustion chamber. The numerical procedures are formulated following a Eulerian approach, within a pressure-based fully conservative Finite Volume ... |
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| Deployable Air Beam Fender System (DAFS): Energy Absorption Performance Analysis |
30 MAR 2007 |
48 pages |
| Authors:
Paul V. Cavallaro; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
|
| Performance curves detailing the energy absorption parameters of selectively sized deployable air beam fender systems (DAFSs) were established to enable future efficiencies in fender design. Numerical solutions were generated using the ABAQUS/Explicit Finite Element Analysis (FEA) Program for two mooring configurations: ship-to-ship and ship-to-causeway (non-ballasted). The governing energy balance was presented and the contributions of strain energy and air compressibility were assessed for various inflation pressures and DAFS sizes. The ... |
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| Investigation of the Effect of Fuselage Dents on Compressive Failure Load |
MAR 2007 |
73 pages |
| Authors:
Nann C. Lang; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The main motivation for this thesis study is that significant workload for aging transport aircrafts is related to dent removal from fuselages. This thesis is a preliminary investigation of aircraft fuselage dents using the Finite Element Method (FEM) via FEA ABAQUS software. We investigated single impact dent on fuselage panel at various locations and impact speeds. The material used for our finite element models is Aluminum Alloy 2024-T3, a typical ... |
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| Estimating Runflat Stiffness |
FEB 2007 |
9 pages |
| Authors:
Wesley Bylsma; Dave Gunter; TACOM RESEARCH DEVELOPMENT AND ENGINEERING CENTER WARREN MI
|
| This report documents a method to estimate runflat stiffness using the bulk modulus of the runflat material. For the example dimensions and material properties given, the runflat stiffness is estimated to be approximately 6,000 pounds per inch and will be contacted after 4.53 inches of tire deflection. The report describes example runflat technology and dimensions, discusses bulk modulus and appropriate values for it, details the calculation for determining compression of ... |
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| Bending Behavior of Plain-Woven Fabric Air Beams: Fluid-Structure Interaction Approach |
01 SEP 2006 |
29 pages |
| Authors:
Paul V. Cavallaro; Ali M. Sadegh; Claudia J. Quigley; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
|
| A swatch of plain-woven fabric was subjected to biaxial tests to determine its material characteristics. The stress-strain relationships of the fabric were determined and used directly in finite element models of an air beam that was assumed to be constructed of the same fabric and subjected to inflation and bending events. The structural responses to these events were obtained using the ABAQUS/Explicit finite element solver for a range of pressures, ... |
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| The Effect of Slug Material on the Behavior of Small-Caliber Ammunition |
SEP 2006 |
22 pages |
| Authors:
Joseph South; Aristedes Yiournas; Michael Minnicino; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| The drive to produce environmentally friendly "green" ammunition has shifted focus to alternate materials for the lead cores in small-arms ammunition. Candidate materials such as tungsten-nylon and tungsten-tin have been evaluated as possible replacements. This research is aimed at evaluating the response of the candidate materials as well as the current M855 "lead" round. Experiments were conducted on sheathed and unsheathed slug samples to determine their compressive response. It was ... |
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| Advanced Stimulated Scattering Measurements in Supercritical Fluids |
SEP 2006 |
47 pages |
| Authors:
Gregory W. Faris; SRI INTERNATIONAL MENLO PARK CA MOLECULAR PHYSICS LAB
|
| Work was performed on development of stimulated Brillouin and Rayleigh scattering for measurements in supercritical fluids. Improvements were made to our instrumentation to fully resolve the stimulated Rayleigh scattering peak in the supercritical regime, a capability that is important for measurement of the thermal properties of supercritical fuels. To provide narrower linewidths, the injection-seeded laser has been modified to operate as a pulse-amplified system. A new electronic modulation technique has ... |
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| Modeling Dynamic Plasticity and Spall Fracture in High Density Polycrystalline Alloys |
SEP 2006 |
34 pages |
| Authors:
J. D. Clayton; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
|
| The dynamic thermomechanical response of a tungsten heavy alloy is investigated via modeling and numerical simulation. The material of study consists of relatively stiff pure tungsten grains embedded within a more ductile matrix alloy comprised of tungsten, nickel, and iron. Constitutive models implemented for each phase account for finite deformation, heat conduction, plastic anisotropy, strain-rate dependence of flow stress, thermal softening, and thermoelastic coupling. The potentially nonlinear volumetric response in ... |
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| Multiscale Mechanical Characterization of Biomimetic Physically Associating Gels |
SEP 2006 |
16 pages |
| Authors:
Thomas F. Juliano; Aaron M. Forster; Peter L. Drzal; Tusit Weerasooriya; Paul Moy; Mark R. VanLandingham; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| The mechanical response of living tissue is important to understanding the injury-risk associated with impact events. Often, ballistic gelatin or synthetic materials are developed to serve as tissue surrogates in mechanical testing. Unfortunately, current materials are not optimal and present several experimental challenges. Bulk measurement techniques, such as compression and shear testing geometries, do not fully represent the stress states and rate of loading experienced in an actual impact event. ... |
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| Stress and Moisture Effects on Thin Film Buckling Delamination |
25 JUL 2006 |
8 pages |
| Authors:
P. Waters; A. A. Volinsky; UNIVERSITY OF SOUTH FLORIDA TAMPA DEPT OF MECHANICAL ENGINEERING
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| Deposition processes control the properties of thin films; they can also introduce high residual stresses. which can be relieved by delamination and fracture. Tungsten films with high 1-2 GPa compressive residual stresses were sputter deposited on top of thin (below 100 nm) copper and diamond-like carbon (DLC) films. Highly stressed films store large amounts of strain energy. When the strain energy release rate exceeds the films interfacial toughness, delamination occurs. ... |
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| Ion Exchanged, Glass Laminates that Exhibit a Threshold Strength |
10 JUL 2006 |
20 pages |
| Authors:
Scott P. Fillery; Frederick F. Lange; CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS
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| Glass laminates, fabricated to contain periodic thin layers containing biaxial compressive stresses, exhibit a threshold strength, i.e., a stress below which failure will not occur. Ion exchange treatments in KNO3 at 350 to 450 deg C for periods of 3 to 72 hrs were used to create residual compressive stresses at the surface of soda lime silicate glass sheets. Wafer direct bonding of the ion exchanged glass sheets resulted in ... |
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| Ceramics that Exhibit a Threshold Strength |
10 JUL 2006 |
12 pages |
| Authors:
Frederick F. Lange; CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS
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| The strength of a brittle material is not a singular value, but a distributed set of values that reflect the large variety of flaws (types and sizes) that are incorporated during processing. The distribution of strength values obtained during testing of ceramic specimens, all made at one time, are generally characterized by statistical parameters that vary with the processing method and processing period, That is, most manufactures cannot control the ... |
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Reports by Keyword(s)
COMPRESSIVE PROPERTIES
