The method of strain measurement after annealing is reviewed and found to be unsatisfactory for the materials available in this country. A new, general method is described for the photoelastic determination of the principal stresses at any point of a general body subjected to arbitrary loads. The method has been applied to a sphere subjected to diametral compressive loads. The results Show-possibilities of high accuracy.
Topics: DTIC Archive, ILLINOIS INST OF TECH CHICAGO, *STRESS ANALYSIS, *PHOTOELASTICITY, STRAIN(MECHANICS),...
Topics: DTIC Archive, *STRESS ANALYSIS, *STRAIN(MECHANICS), *BRITTLENESS, *LACQUERS, REPRINTS, TEMPERATURE,...
The effect of elastic strain rates ranging from 0.001 to 10/sec and temperatures ranging from 200K (-100F) to 590K (600F) on the yield strength of several steels is reported. The steels utilized are a 1018 mild steel, 4340 steel, H-11 tool steel and 300 grade maraging steel. The results are interpreted in terms of the Cottrel-Bilby yielding model based on release of dislocations from locking carbon atmospheres. The results for all of the materials except the maraging steel are consistent with...
Topics: DTIC Archive, Kendall, David P, WATERVLIET ARSENAL NY, *STEEL, DISLOCATIONS, STRAIN(MECHANICS),...
The calculation of the residual bore stresses in an autofrettaged cylinder is based upon a theory utilizing a perfectly plastic material. Nadai suggested a technique which would account for strain hardening of the material. The present report compares experimentally measured data for an autofrettaged cylinder, constructed of a strain hardening material, with this theory.
Topics: DTIC Archive, NAVAL ORDNANCE LAB WHITE OAK MD, *STRAIN(MECHANICS), DEFORMATION, EXPERIMENTAL DATA,...
This report describes an investigation into the effects of mechanical deformation on photoluminescence (PL) behavior for the neat conjugated polymers: poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and polythiophenes (P3HT, P3BT, P3EHT). This study used a unique bilayer stretching method where the thin conjugated polymer was drawn into local deformation zones at very high local mechanical strain (300%) on top of glassy polystyrene film. It was found that very large PL...
Topics: DTIC Archive, NATIONAL TSING HUA UNIV HSINCHU (TAIWAN), *PHOTOLUMINESCENCE, CONJUGATED POLYMERS,...
Samples of nylon 6 were subjected to drawing from a few percent to greater than a hundred percent and allowed to stress relax. This involved elongating the sample to a certain point and then keeping the length constant. When the sample is momentarily held at the peak of the original yield point and then pulled again, a higher-than-original yield peak develops. Subsequent interruptions followed by drawing resulted in the formation of additional yield peaks. In each of these latter cases, the new...
Topics: DTIC Archive, Rubin, Jerome, PICATINNY ARSENAL DOVER NJ, *NYLON, STRESSES, STRAIN(MECHANICS),...
A novel large strain sensor has been developed using a silicone/nickel nanostrand/nickel coated carbon fiber nanocomposite system. The effect of conductive filler volume fraction on the piezoresistive response of the nanocomposite sensor has been studied in order to determine the optimal composition for use in large strain/motion sensing applications. Electromechanical testing of various compositions revealed that optimum performance was achieved using 11 vol% nickel nanostrands with 2 vol%...
Topics: DTIC Archive, BRIGHAM YOUNG UNIV PROVO UT, *ELASTOMERS, *MATRIX MATERIALS, *STRAIN GAGES, CARBON...
A feasibility study has been completed on the use of a microprocessor as an aircraft in-flight fatigue monitoring device. Two prototypes have been assembled and successfully laboratory tested. The study has shown great promise in dollar savings by providing local strain data from which aircraft life predictions can be made more accurately.
Topics: DTIC Archive, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *MONITORS, *FATIGUE(MECHANICS), *AIRCRAFT,...
The paper is based on data for the largest earthquakes (magnitude 7 or above) in the interval 1897-1964. Strain energy release and numbers of earthquakes are studied both in relation to their time and space distribution. The circum-Pacific belt exhibits two pronounced concentrations of strain energy release, in its NW and SE part. There is a general decrease of seismic activity over the period investigated. The whole material used is presented in a table, probably the most complete list of...
Topics: DTIC Archive, UPPSALA UNIV (SWEDEN), *EARTHQUAKES, *LITHOSPHERE, *SEISMOLOGY, ENERGY, GEOLOGY,...
The research has developed a powerful crystal plasticity based computational modeling tool for predicting mechanical response and localization, eventually leading to failure in polycrystalline titanium alloys, e.g. Ti-6Al-4V and Ti-7AL under extreme loading conditions. Ti alloys possess complex heterogeneous microstructures due to non-uniform grain size distribution and strong anisotropy arising from dislocation glide on different slip systems. The computational model aims at enhancing the...
Topics: DTIC Archive, Johns Hopkins University Baltimore United States, COMPUTATIONAL MODELING,...
The effect of loading rates, ranging from 10 to 100,000 ksi square root of (in/sec), and temperatures, ranging from room temperature to -100F, on the plane strain fracture toughness of several high strength alloy steels has been determined. Materials investigated are a commercial 4340 steel, a modified 4330 steel from a gun tube forging having three different heat treatments and two different heats of 250 grade maraging steel. Test specimens utilized are essentially ASTM 'compact tension' type...
Topics: DTIC Archive, Kendall, David P, WATERVLIET ARSENAL NY, *STEEL, FRACTURE(MECHANICS), LOADS(FORCES),...
A two-part investigation was performed to study the relationship between defects formation and deformation characteristics in plane-strain side- pressing and axisymmetric plastic indentation. In the first part, the investigation was undertaken to examine the detailed deformation characteristics involved in axisymmetric plastic indentation. Circular punches with flat and hemispherical ends were indented into specimens prepared from SAE 1215 steels under as-received and annealed conditions. In...
Topics: DTIC Archive, Kobayashi, Shiro, CALIFORNIA UNIV BERKELEY, *STEEL, *FORGING, DEFORMATION,...
Topics: DTIC Archive, MICHIGAN UNIV ANN ARBOR, *BENDING, *SHAPE MEMORY ALLOYS, COMPRESSION, HONEYCOMB...
Recent theoretical proposals suggest that strain can be used to engineer graphene electronic states through the creation of a pseudo magnetic field. This effect is unique to graphene because of its massless Dirac fermion-like band structure and particular lattice symmetry (C[sub 3v]). Here, we present experimental spectroscopic measurements by scanning tunneling microscopy of highly strained nanobubbles that form when graphene is grown on a platinum (111) surface. The nanobubbles exhibit Landau...
Topics: DTIC Archive, CALIFORNIA UNIV BERKELEY DEPT OF PHYSICS, *MAGNETIC FIELDS, *STRAIN(MECHANICS),...
The discussion is addressed towards establishing a connection between two alternative constitutive equations that have been used in the past to describe the temperature (and strain rate) dependence of the yield stress of iron.
Topics: DTIC Archive, BROWN UNIV PROVIDENCE RI DIV OF ENGINEERING, *STRESSES, *IRON, STRAIN(MECHANICS),...
Laboratory evidence indicates that when strains exceed 10 to the -6 in media under low confining pressure, certain nonlinear processes begin to occur. They are manifested by a reduction in apparent Q. Since direct measurement of near field strain are rare, it has been difficult to evaluate whether or not this phenomenon is significant near to realistic seismic sources. A high frequency theory for computing stresses and strains using generalized ray theory has been developed. It can be shown...
Topics: DTIC Archive, Burdick,L J, WOODWARD-CLYDE CONSULTANTS PASADENA CA, *EXPLOSIONS, *EARTHQUAKES,...
The highest loads on bottoms of fast craft are due to slamming, or hydrodynamic impact. A 9 meter long steel/composite hybrid slamming load test facility has been employed for the purpose of furthering understanding of the slamming phenomenon. This craft is heavily instrumented with strain gages, accelerometers, cameras, an inertial navigation system and more. It has been subjected to tests in a lab environment, in calm seas, and in rough seas. Slamming tests were performed in the Atlantic...
Topics: DTIC Archive, LEHIGH UNIV BETHLEHEM PA, *BOATS, *IMPACT LOADS, BOTTOM, HULLS(MARINE),...
The present invention relates to measuring strain and bending stresses in a well conductor, and more particularly to a plurality of Bragg gratings written onto an optical fiber that is integrated into an armored cable wrapped around the well conductor.
Topics: DTIC Archive, DEPARTMENT OF THE NAVY WASHINGTON DC, *BENDING STRESS, *SHIP STRUCTURAL COMPONENTS,...
Glazing in storefront and curtain wall configurations is increasingly used in areas subjected to blast load. Current design approaches typically use single-degree-of-freedom (SDOF) methods to analyze the performance of both the glazing and mullions. The flexural resistance and mass of each component must be identified to solve the SDOF. The resistance is calculated based on span, support conditions, cross sectional stiffness and an assumed deformed shape. Dynamic verification of deformed shape...
Topics: DTIC Archive, PROTECTION ENGINEERING CONSULTANTS LLC AUSTIN TX, *BLAST, *GLASS, DEFORMATION, FINITE...
A surface martensite was observed in a 304L stainless steel. The morphological details as influenced by polishing techniques and thermal quenching are discussed. The quantity of martensite was found to be greatly amplified by the strain energy produced by mechanical polishing.
Topics: DTIC Archive, Odegard, B C, SANDIA LABS LIVERMORE CA MATERIALS DEVELOPMENT DIV, *MARTENSITE,...
An experimental study was made of influence of strain magnitude and strain duration on dynamic fracture in uniaxial tension of low-strength gypsum plaster, high-strength gypsum plaster, high early strength portland cement mortar, and ordinary portland cement mortar. Dynamic test specimens were circular cylindrical bars with diameters ranging from 0.9 to 1.2 inches and lengths ranging from 18 to 58 inches. Static test specimens 2 inches long were cut from the long bars. A special loading device,...
Topics: DTIC Archive, MELPAR FALLS CHURCH VA, *CEMENTS, *GYPSUM, BRITTLENESS, EXPERIMENTAL DATA,...
The state of a linear system is independent of how hard it is driven. Not so, a nonlinear system. As you sweep a nonlinear system through resonance you change the state of the system. If you want to study a system in a particular state it is advantageous to maintain it in that state. The antagonism between conventional experimental practice, sweeping through a resonance, and the desire to maintain the system in a particular state is mitigated by constant strain analysis. The analysis of a...
Topics: DTIC Archive, Guyer, Ropbert A., LOS ALAMOS NATIONAL LAB NM, *STRAIN(MECHANICS), ELASTIC...
Improvised Explosive Devices (IEDs) have evolved over the years to become one of the main causes of casualties and fatalities in recent conflicts. One area of research focuses on the improvement of blast attenuation using Shear Thickening Fluid (STF). The STF is a dilatant material, which displays non-Newtonian characteristics in its unique ability to transit from a low viscosity fluid to a high viscosity fluid. Although empirical research and computational models using the non-Newtonian flow...
Topics: DTIC Archive, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *IMPROVISED EXPLOSIVE DEVICES, BLAST,...
Two one-meter infrared optical masers were operated in a manner such that horizontal strains would be detected. The first results have been encouraging and suggest that optical maser strain qauges will be able to compete with the much longer conventional strain gauges. An optical maser transducer for a seismograph has been built. A special short-period seismograph to be used with this transducer was constructed. (Author)
Topics: DTIC Archive, Alsop, Leonard E, LAMONT GEOLOGICAL OBSERVATORY PALISADES NY, *LASERS, *SEISMOGRAPHS,...
Compression creep and compression constant strain-rate tests were performed on thick wall cylindrical specimens of aluminum alloy 2024-0 at 500F (533K). Using the assumption that the equation of state of the material is a function only of stress, strain, and strain rate, the creep curves were analyzed to yield constant strain-rate, stress strain data. Comparisons between the creep-derived and the directly measured constant strain-rate data show that the data are not exactly equivalent but the...
Topics: DTIC Archive, ALLIED RESEARCH ASSOCIATES INC CONCORD MA, *ALUMINUM ALLOYS, STABILITY,...
Briefing charts only.
Topics: DTIC Archive, Dominauskas, A, DELAWARE UNIV NEWARK CENTER FOR COMPOSITE MATERIALS, *REFLECTOMETERS,...
A finite element muscle model to study the principles of intermuscular myofascial force transmission is developed. The results obtained explain force differences at the distal and proximal tendons of muscles that have mechanical interaction. This is in agreement with experimental findings in other recent studies, The strain distributions found along the fiber direction indicate intermuscular myofascial force transmission. A consequence is that active force generated within one muscle may be...
Topics: DTIC Archive, Yucesoy, Can A, TWENTE UNIV ENSCHEDE (NETHERLANDS), *FINITE ELEMENT ANALYSIS,...
The Neuber rule is evaluated using an appropriate analytic representation of the stress-strain curve of AISI 4340 steel and predictions of maximum notch strain versus nominal net section stress are developed. The theoretical results, when compared with test data from flat notched specimens of the same material with a range of initial elastic concentration factors, show agreement within 5%. It is shown that the limitations of the strain gages in measuring the notch root strains can account for a...
Topics: DTIC Archive, Papirno, Ralph, ARMY MATERIALS AND MECHANICS RESEARCH CENTER WATERTOWN MA, *STEEL,...
The objective of this program is the study of the autofrettage principle as applied to high strength thick-wall steel cylinders of intermediate diameter ratio and the development of the design criteria and procedures for the application of autofrettage to light weight gun tube design and fabrication.
Topics: DTIC Archive, Davidson, T E, WATERVLIET ARSENAL NY, *GUN BARRELS, *COLD WORKING, STRESSES,...
Soil strain gage instrumentation was developed for the measurement of static and dynamic strains when embedded in soil. The gage is suitable for both laboratory and field application. The strain sensor consists of two mechanically uncoupled flat-coil disks which are embedded in the soil in near parallel and concentric orientation. The remainder of the gage comprises an identical set of coils positioned external to the soil as a standard reference, specially designed electronic driving,...
Topics: DTIC Archive, IIT RESEARCH INST CHICAGO IL, *SOIL MECHANICS, *STRAIN GAGES, CIRCUITS, COILS,...
The specific goals of the proposed research have been threefold: (1) to establish a fundamental, mechanistic understanding of the degradation processes that occur in superalloy components with coatings during thermo-mechanical cycling; and (2) to use the experimental information to critically evaluate and further develop models for thermochemical and thermomechanical degradation of the multilayered systems and (3) to more quantitatively define the design space and guide the development of...
Topics: DTIC Archive, CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS, *AIRFOILS, *COATINGS, *SUBSTRATES,...
Topics: DTIC Archive, Shur, Michael, VIRGINIA UNIV CHARLOTTESVILLE DIV OF ELECTRICAL ENGINEERING, *NAVAL...
Compressed sensing, also known as compressive sensing, is a technique for finding sparse solutions to underdetermined linear systems. In signal processing, compressed sensing is the process of acquiring and reconstructing a signal that is known to be sparse or compressible. The theory asserts that certain signals or images can be recovered from what was previously thought to be highly incomplete measurements. This report reviews this rapidly growing field and its application in structural...
Topics: DTIC Archive, ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD VEHICLE TECHNOLOGY DIRECTORATE,...
The equations governing the consolidation, and the stress and strains states for soil structures are reviewed and their historical development is discussed. Numerical analysis concepts are used to express these equations in incremental form. A variational statement of these incremental equations is formulated and used in the development of a comprehensive finite element analysis. The concepts used in developing the variational statement are somewhat different from those used by most other...
Topics: DTIC Archive, Herrmann,L R, CALIFORNIA UNIV DAVIS, *Soil mechanics, Soils, Stresses,...
This report presents mathematical and finite element (FE) models that were used to predict the deformation and strain levels of a circuit board under a variety of four-point monotonic bend test configurations. The derivations of the mathematical models for deformation and strain are examined, and an equation modeling the strain rate of the board as it is bending is presented. The two and three-dimensional (2-D and 3-D) FE models are discussed and validated and the differences in deformation and...
Topics: DTIC Archive, GEORGE WASHINGTON UNIV WASHINGTON DC DEPT OF ENGINEERING, *BENDING, *CIRCUIT BOARDS,...
The report presents three-dimensional, large deformation, coupled finite element analysis (FEA) of dynamic loading on soft biological tissues treated as biphasic (solid-fluid) porous media. An overview is presented of the biphasic solid-fluid mixture theory at finite strain, including inertia terms. The solid skeleton is modeled as an isotropic, compressible, hyperelastic material. FEA simulations include: (1) compressive uniaxial strain loading on a column of lung parenchyma with either pore...
Topics: DTIC Archive, COLORADO UNIV AT BOULDER, *DEFORMATION, *FINITE ELEMENT ANALYSIS, *SOFT TISSUES,...
The object of this report was to study the shear strength of a structural adhesive used in Army helicopters as a function of strain rate and failure time at several temperatures. Shear strengths of adhesive AF126 bonds to two thicknesses of aluminum were measured at constant rate of crosshead separation. Primarily cohesive failure was observed in all cases. By using relations proposed by Cherry and Holmes, the shear strength could be quantitatively related to temperature and strain rate or...
Topics: DTIC Archive, McAbee, Elise, PICATINNY ARSENAL DOVER NJ, *ADHESIVES, *BONDED JOINTS, ALUMINUM...
A research program directed toward gaining an understanding of the molecular mechanisms of large strain deformation in glassy and crystalline polymers has been carried out. The investigation encompassed two types of experimental procedures: deformation experiments on bulk polymers to determine the thermal activation parameters of the rate limiting step of the deformation process, and microscopic examination of deformed samples to determine what types of molecular motions had taken place....
Topics: DTIC Archive, Turner, Arthur P, MASSACHUSETTS INST OF TECH CAMBRIDGE, *POLYMERS, *DEFORMATION,...
InxGa1-xSb is an attractive candidate for high performance III-V p-metal-oxide-semiconductor field effect transistors (pMOSFETs) due to its high bulk hole mobility that can be further enhanced with the use of strain. We fabricate and study InxGa1-xSb-channel pMOSFETs with atomic layer deposition Al2O3 dielectric and self-aligned source/drain formed by ion implantation. The effects of strain and heterostructure design for enhancing transistor performance are studied systematically. Different...
Topics: DTIC Archive, NAVAL RESEARCH LAB WASHINGTON DC ELECTRONICS SCIENCE AND TECHNOLOGY DIV, *MOSFET...
With current involvements of the U.S. Military in various peace-keeping and combat operations throughout the world, there is an increase in the deployment of armored military vehicles. Traditional armoring techniques have performed well against particular threats, but, in the recent combat operations, a new threat of improvised explosive devices, the vulnerability of the undercarriage, is being exposed. While thick, steel-structural members have been used in the past, an effort to make them...
Topics: DTIC Archive, OAK RIDGE INST FOR SCIENCE AND EDUCATION TN, *ALUMINUM ALLOYS, FRICTION WELDING,...
Topics: DTIC Archive, ARA INC WEST COVINA CA, *HIGH ENERGY, *ENERGY ABSORBERS, IMPACT TESTS,...
The Eshelby-type problem of an arbitrary-shape polyhedral inclusion embedded in an infinite homogeneous isotropic elastic material is analytically solved using a simplified strain gradient elasticity theory (SSGET) that contains a material length scale parameter. The Eshelby tensor for a polyhedral inclusion of arbitrary shape is obtained in a general analytical form in terms of three potential functions, two of which are the same as the ones involved in the counterpart Eshelby tensor based on...
Topics: DTIC Archive, TEXAS A AND M UNIV COLLEGE STATION DEPT OF MECHANICAL ENGINEERING, *ELASTIC...
The effect of rate of strain on shear strength of cohesive soils of marine sediments were studied. Vane shear (apparatus) tests were performed on an ocean sediment at varying permeabilities with various rates of shear. A variation in shear strength as high as 46.4% have been found over the range of rotation rates used in this experiment. Suggestions for further experimentation in this area are included.
Topics: DTIC Archive, Halwachs, James E, NAVAL ACADEMY ANNAPOLIS MD, *OCEAN BOTTOM, DEFORMATION,...
The conformal gear was studied as a means of improving helicopter final reduction drives. By eliminating certain inherent limitations of the involute gear, the developed conformal tooth form has the potential of bettering current power-to-weight ratios. An analytical and experimental effort was conducted on carburized and ground conformal gears.
Topics: DTIC Archive, BOEING CO MORTON PA VERTOL DIV, *HELICOPTERS, *REDUCTION GEARS, *TRANSMISSION GEARS,...
A simple method is presented for estimating the combined influence of strain-hardening and strain-rate sensitivity on the permanent deformation of rigid-plastic structures loaded dynamically. A study is made of the particular case of a beam supported at the ends by immovable frictionless pins and loaded with a uniform impulse. The results of this work indicates that considering strain-hardening alone when appropriate or strain-rate sensitivity alone gives permanent deformations which are...
Topics: DTIC Archive, Jones, Norman, BROWN UNIV PROVIDENCE RI DIV OF ENGINEERING, *BEAMS(STRUCTURAL),...
Biaxial stress tests were performed on thin wall tubes of polycrystalline 2024-T81 Aluminum at temperatures of 150 and 250c. The nominal metallurgical stabilization temperature for this alloy is 190c. Transient and steady state creep strain rates exhibited a considerable depenence on load path history. For a prescribed history it is possible to determine unique surfaces of constant creep strain rate. For the zero history, involving a single loading from the origin to a prescribed point in...
Topics: DTIC Archive, Brown, G M, BROWN UNIV PROVIDENCE RI DIV OF ENGINEERING, *ALUMINUM ALLOYS, CREEP,...
Previous 2D AutoDyn mesh sensitivity analyses of cylinder impact on ceramic determined the 0.20-mm mesh size provides a fracture pattern that may be considered acceptable. Previous mesh sensitivity analyses used a constant erosion strain value of 1.0 for the projectile and 2.0 for the target. Using the accepted 0.20-mm mesh size, analysis has been conducted to determine the effect of erosion strain on target fracture patterns and projectile kinetic energies. Erosion strain sensitivity analysis...
Topics: DTIC Archive, DELAWARE UNIV NEWARK, *ARMOR, *MESH, *STRAIN(MECHANICS), EROSION, GEOMETRY, IMPACT,...
The ability to accurately determine the amount of structural life that has been consumed in military aircraft can be compromised by the inability to be consistent in the manufacture and installation of strain sensors and general aircraft-to-aircraft variations in the structures themselves. The variations must be accounted for in order to be able to make correct decisions - regarding the ability to safely operate the aircraft as well as reducing the need to purchase new aircraft (resulting from...
Topics: DTIC Archive, NAVAL AIR SYSTEMS COMMAND PATUXENT RIVER MD, *CALIBRATION, *FATIGUE LIFE, *MILITARY...
The document describes methods and procedures that deal with the reduction, presentation, and analysis of environmental data which have specific application to structural evaluations and fall under the following categories: Vibration; Shock; Acoustics; and Strain.
Topics: DTIC Archive, ARMY TEST AND EVALUATION COMMAND ABERDEEN PROVING GROUND MD, *STRUCTURAL PROPERTIES,...
Topics: DTIC Archive, Geil, G W, NATIONAL BUREAU OF STANDARDS GAITHERSBURG MD, *STEEL, *PLASTIC PROPERTIES,...
