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A novel method to synthesize high purity, nanostructured copper

Description: Nanostructured high purity (99.999%) copper foils, 10 cm in diameter and 22-25 microns thick were produced using nanoscale multilayer technology. The foils were produced using five different layer thicknesses ranging from 1.25 to 43.6 nm (18,000 to 520 layers). This process delivers the ability to produce multiple large-scale samples during a single deposition run with very small residual stresses. Tensile and indentation tests demonstrate that the material produced is a high strength copper ({sigma}{sub y} {approx} 540-690 MPa).
Date: August 30, 2005
Creator: Hodge, A M; Wang, Y M & Barbee, T W
Partner: UNT Libraries Government Documents Department

Accuracy evaluation of residual stress measurements

Description: The accuracy of residual stress measurement techniques is difficult to assess due to the lack of available reference standards. To satisfy the need for reference standards, two specimens were designed and developed to provide known stress magnitudes and distributions: one with a uniform stress distribution and one with a nonuniform linear stress distribution. A reusable, portable load fixture was developed for use with each of the two specimens. Extensive bench testing was performed to determine if the specimens provide desired known stress magnitudes and distributions and stability of the known stress with time. The testing indicated that the nonuniform linear specimen and load fixture provided the desired known stress magnitude and distribution but that modifications were required for the uniform stress specimen. A trial use of the specimens and load fixtures using hole drilling was successful.
Date: May 1, 1996
Creator: Yerman, J.A.; Kroenke, W.C. & Long, W.H.
Partner: UNT Libraries Government Documents Department

Experimental measurement and numerical simulation of residual stresses in a carburized layer of a 5120 steel

Description: A combined experimental and numerical study of residual stress and microstructure has been performed for a carburized steel 5120 specimen. Specimens were cut from 5120 steel bar stock, in the shape of hockey pucks and were subsequently carburized and quenched. X-ray diffraction was used to record stress profiles through the case for the martensite and retained austenite on the two flat surfaces oriented up and down during the quench. Layer removal was performed by electropolishing. Rietveld analysis was used to determine the lattice parameters of the phases at each depth varying with both carbon content and stress. The experimental measurements are compared with a numerical simulation of the phase transformation and the metallurgical changes following the carburization and quench. Results am discussed in the context of the microstructure and the role played by the retained austenite in interpretation. In addition the carbon profile obtained from the lattice parameters is compared with profiles measured using burnout.
Date: September 1, 1995
Creator: Rangaswamy, P.; Bourke, M.A.M.; Shipley, J.C. & Goldstone, J.A.
Partner: UNT Libraries Government Documents Department

X-ray diffraction characterization of suspended structures for MEMS applications

Description: Mechanical stress control is becoming one of the major challenges for the future of micro and nanotechnologies. Micro scanning X-ray diffraction is one of the promising techniques that allows stress characterization in such complex structures at sub micron scales. Two types of MEMS structure have been studied: a bilayer cantilever composed of a gold film deposited on poly-silicon and a boron doped silicon bridge. X-ray diffraction results are discussed in view of numerical simulation experiments.
Date: September 15, 2005
Creator: Goudeau, P.; Tamura, N.; Lavelle, B.; Rigo, S.; Masri, T.; Bosseboeuf, A. et al.
Partner: UNT Libraries Government Documents Department

Joining of Beryllium

Description: A handbook dealing with the many aspects of beryllium that would be important for the users of this metal is currently being prepared. With an introduction on the applications, advantages and limitations in the use of this metal the following topics will be discussed in this handbook: physical, thermal, and nuclear properties; extraction from the ores; purification and casting of ingots; production and types of beryllium powders; consolidation methods, grades, and properties; mechanical properties with emphasis on the various factors affecting these properties; forming and mechanical working; welding, brazing, bonding, and fastening; machining; powder deposition; corrosion; health aspects; and examples of production of components. This report consists of ''Section X--Joining'' from the handbook. The prefix X is maintained here for the figures, tables and references. In this section the different methods used for joining beryllium and the advantages, disadvantages and limitations of each are presented. The methods discussed are fusion welding, brazing, solid state bonding (diffusion bonding and deformation bonding), soldering, and mechanical fastening. Since beryllium has a high affinity for oxygen and nitrogen with the formation of oxides and nitrides, considerable care must be taken on heating the metal, to protect it from the ambient atmosphere. In addition, mating surfaces must be cleaned and joints must be designed to minimize residual stresses as well as locations for stress concentration (notch effects). In joining any two metals the danger exists of having galvanic corrosion if the part is subjected to moisture or to any type of corroding environment. This becomes a problem if the less noble (anodic) metal has a significantly smaller area than the more noble (cathodic) metal since the ions (positive charges) from the anodic (corroding) metal must correspond to the number of electrons (negative charges) involved at the cathode. Beryllium is anodic to almost all metals; thus, ...
Date: February 1, 2006
Creator: Goldberg, A
Partner: UNT Libraries Government Documents Department

An Improved Method of Mitigating Laser Induced Surface Damage Growth in Fused Silica Using a Rastered, Pulsed CO2 Laser

Description: A new method of mitigating (arresting) the growth of large (>200 m diameter and depth) laser induced surface damage on fused silica has been developed that successfully addresses several issues encountered with our previously-reported large site mitigation technique. As in the previous work, a tightly-focused 10.6 {micro}m CO{sub 2} laser spot is scanned over the damage site by galvanometer steering mirrors. In contrast to the previous work, the laser is pulsed instead of CW, with the pulse length and repetition frequency chosen to allow substantial cooling between pulses. This cooling has the important effect of reducing the heat-affected zone capable of supporting thermo-capillary flow from scale lengths on the order of the overall scan pattern to scale lengths on the order of the focused laser spot, thus preventing the formation of a raised rim around the final mitigation site and its consequent down-stream intensification. Other advantages of the new method include lower residual stresses, and improved damage threshold associated with reduced amounts of redeposited material. The raster patterns can be designed to produce specific shapes of the mitigation pit including cones and pyramids. Details of the new technique and its comparison with the previous technique will be presented.
Date: October 21, 2010
Creator: Bass, I L; Guss, G M; Nostrand, M J & Wegner, P L
Partner: UNT Libraries Government Documents Department

CONTAINER MATERIALS, FABRICATION AND ROBUSTNESS

Description: The multi-barrier 3013 container used to package plutonium-bearing materials is robust and thereby highly resistant to identified degradation modes that might cause failure. The only viable degradation mechanisms identified by a panel of technical experts were pressurization within and corrosion of the containers. Evaluations of the container materials and the fabrication processes and resulting residual stresses suggest that the multi-layered containers will mitigate the potential for degradation of the outer container and prevent the release of the container contents to the environment. Additionally, the ongoing surveillance programs and laboratory studies should detect any incipient degradation of containers in the 3013 storage inventory before an outer container is compromised.
Date: November 10, 2009
Creator: Dunn, K.; Louthan, M.; Rawls, G.; Sindelar, R.; Zapp, P. & Mcclard, J.
Partner: UNT Libraries Government Documents Department

Measuring multiple residual-stress components using the contour method and multiple cuts

Description: The conventional contour method determines one component of stress over the cross section of a part. The part is cut into two, the contour of the exposed surface is measured, and Bueckner's superposition principle is analytically applied to calculate stresses. In this paper, the contour method is extended to the measurement of multiple stress components by making multiple cuts with subsequent applications of superposition. The theory and limitations are described. The theory is experimentally tested on a 316L stainless steel disk with residual stresses induced by plastically indenting the central portion of the disk. The stress results are validated against independent measurements using neutron diffraction. The theory has implications beyond just multiple cuts. The contour method measurements and calculations for the first cut reveal how the residual stresses have changed throughout the part. Subsequent measurements of partially relaxed stresses by other techniques, such as laboratory x-rays, hole drilling, or neutron or synchrotron diffraction, can be superimposed back to the original state of the body.
Date: January 1, 2009
Creator: Prime, Michael B; Swenson, Hunter; Pagliaro, Pierluigi & Zuccarello, Bernardo
Partner: UNT Libraries Government Documents Department

INTERFACE RESIDUAL STRESSES IN DENTAL ZIRCONIA USING LAUE MICRO-DIFFRACTION

Description: Due to their aesthetic value and high compressive strength, dentists have recently employed ceramics for restoration materials. Among the ceramic materials, zirconia provides high toughness and crack resistant characteristics. Residual stresses develop in processing due to factors including grain anisotropy and thermal coefficient mismatch. In the present study, polychromatic X-ray (Laue) micro-diffraction provided grain orientation and residual stresses on a clinically relevant zirconia model ceramic disk. A 0.5 mm x 0.024 mm region on zirconia was examined on a 500 nm scale for residual stresses using a focused poly-chromatic synchrotron X-ray beam. Large stresses ranging from - to + 1GPa were observed at some grains. On average, the method suggests a relatively small compressive stress at the surface between 47 and 75 MPa depending on direction.
Date: January 1, 2009
Creator: Bale, H. A.; Tamura, N.; Coelho, P.G. & Hanan, J. C.
Partner: UNT Libraries Government Documents Department

RESIDUAL STRESSES IN 3013 CONTAINERS

Description: The DOE Complex is packaging plutonium-bearing materials for storage and eventual disposition or disposal. The materials are handled according to the DOE-STD-3013 which outlines general requirements for stabilization, packaging and long-term storage. The storage vessels for the plutonium-bearing materials are termed 3013 containers. Stress corrosion cracking has been identified as a potential container degradation mode and this work determined that the residual stresses in the containers are sufficient to support such cracking. Sections of the 3013 outer, inner, and convenience containers, in both the as-fabricated condition and the closure welded condition, were evaluated per ASTM standard G-36. The standard requires exposure to a boiling magnesium chloride solution, which is an aggressive testing solution. Tests in a less aggressive 40% calcium chloride solution were also conducted. These tests were used to reveal the relative stress corrosion cracking susceptibility of the as fabricated 3013 containers. Significant cracking was observed in all containers in areas near welds and transitions in the container diameter. Stress corrosion cracks developed in both the lid and the body of gas tungsten arc welded and laser closure welded containers. The development of stress corrosion cracks in the as-fabricated and in the closure welded container samples demonstrates that the residual stresses in the 3013 containers are sufficient to support stress corrosion cracking if the environmental conditions inside the containers do not preclude the cracking process.
Date: November 10, 2009
Creator: Mickalonis, J. & Dunn, K.
Partner: UNT Libraries Government Documents Department

Finite element prediction of elastic strains in beryllium compact tension specimens

Description: Three-dimensional finite element (FE) calculations using ABAQUS version 5.5.9 were compared to neutron diffraction measurements of a loaded, pre-cracked beryllium compact tension (CT) specimens. The objective was to validate the FE results with the experimental {open_quotes}elastic strain{close_quotes} measurements. Then the FE calculations could be used to study residual stress and other aspects of these problems in the unloaded state and the crack tip stress in the loaded state which is hard to measure experimentally. A graded FE mesh was focused on the regions containing high strain gradients, the smallest elements were approximately 0.5 mm x 0.5 mm x 0.4 mm. A standard 20-node brick element model was complemented by a model with 1/4-point elements at the crack tip. Since the neutron diffraction measurements provided a volume average of approximately a cube of edge 3.0 mm, various averaging (or integrating) techniques were used on the FE results. Several integration schemes showed good agreement with the experimental results.
Date: May 1, 1997
Creator: Guerra, F.; Varma, R. & Bourke, M.
Partner: UNT Libraries Government Documents Department

A technique for determining the Poisson`s ratio of thin films

Description: The theory and experimental approach for a new technique used to determine the Poisson`s ratio of thin films are presented. The method involves taking the ratio of curvatures of cantilever beams and plates micromachined out of the film of interest. Curvature is induced by a through-thickness variation in residual stress, or by depositing a thin film under residual stress onto the beams and plates. This approach is made practical by the fact that the two curvatures air, the only required experimental parameters, and small calibration errors cancel when the ratio is taken. To confirm the accuracy of the technique, it was tested on a 2.5 {mu}m thick film of single crystal silicon. Micromachined beams 1 mm long by 100 {mu} wide and plates 700 {mu}m by 700 {mu}m were coated with 35 nm of gold and the curvatures were measured with a scanning optical profilometer. For the orientation tested ([100] film normal, [011] beam axis, [0{bar 1}1] contraction direction) silicon`s Poisson`s ratio is 0.064, and the measured result was 0.066 {+-} 0.043. The uncertainty in this technique is due primarily to variation in the measured curvatures, and should range from {+-} 0.02 to 0.04 with proper measurement technique.
Date: April 18, 1996
Creator: Krulevitch, P.
Partner: UNT Libraries Government Documents Department

High-Throughput Laser Peening of Metals Using a High-Average-Power Nd: Glass Laser System

Description: Laser shot peening, a surface treatment for metals, is known to induce residual compressive stresses to depths of over 1 mm providing improved component resistance to various forms of failure. Recent information also suggests that thermal relaxation of the laser induced stress is significantly less than that experienced by other forms of surface stressing that involve significantly higher levels of cold work. We have developed a unique solid state laser technology employing Nd:glass amplifier slabs and SBS phase conjugation that enables this process to move into high throughput production processing.
Date: November 1, 1999
Creator: Dane, C.B.; Hackel, L.A.; Halpin, J.; Daly, J.; Harrisson, J. & Harris, J.
Partner: UNT Libraries Government Documents Department

MEMS Adaptive Optics Devices: LDRD No. 02-1385 Summary Report

Description: The primary goal of this portion of the LDRD is to develop a vertical programmable diffraction grating that can be fabricated with Sandia's Ultra-planar Multi-level MEMS Technology, the SUMMiT V{trademark} process. This grating is targeted for use in a chemical detection system dubbed the Polychromator. A secondary goal is to design diffraction grating structures with additional degrees of freedom (DOF). Gratings with 2.5 microns of vertical stroke have been realized. In addition, rotational DOF grating structures have been successfully actuated, and a structure has been developed that minimizes residual stress effects.
Date: December 1, 2002
Creator: DAGEL, DARYL J. & ALLEN, JAMES J.
Partner: UNT Libraries Government Documents Department

Residual stress distribution in an Al{sub 2}O{sub 3}-Ni joint bonded with a composite layer

Description: Neutron diffraction was used to study the residual stress distribution in an axisymmetric Al{sub 2}O{sub 3}-Ni joint bonded with a 40 vol% Al{sub 2}O{sub 3}-60 vol% Ni composite layer. A series of measurements was taken along the axis of symmetry through the Al{sub 2}O{sub 3} and composite layers. It is shown that after taking into account the finite neutron diffraction sampling volume, both the trends and peak values of the experimental strain distribution were in excellent agreement with calculations of a simple finite element model, where the rule-of-mixtures approach was used to describe the constitutive behavior of the composite interlayer. In particular, the predicted steep strain gradient near the interface was confirmed by the experimental data.
Date: July 1, 1996
Creator: Wang, X.L.; Watkins, T.R.; Rabin, B.H.; Williamson, R.L. & Bruck, H.A.
Partner: UNT Libraries Government Documents Department

Measurement and modeling of residual stress in net-shape plasma sprayed tubes

Description: Residual stresses in net-shaped plasma sprayed MoSi{sub 2} tubes were measured by x-ray microdiffraction as a function of radial position in the sample. A tensile to compressive hoop stress profile was measured, ranging 200 MPa in tension at the outer diameter, to -125 MPa at the inner. A force balance model was used to explain the evolution of stresses when incrementally adding layers to the pre-existent material.
Date: September 1, 1996
Creator: Bartlett, A. & Castro, R.G.
Partner: UNT Libraries Government Documents Department

Detector array design

Description: Neutron scattering facility at Oak-Ridge National is used to measure residual stresses in many different materials. Neutron beam from the reactor can be used to penetrate the inner atomic distances of metals which then can be diffracted to a detector to measure the strain. The strain data later can be converted to stresses. The facility currently uses only one detector to carry the measurement. By designing an array of detectors data can be obtained at a much faster rate and or having a much better and improved resolution. The purpose of this report is to show design of such array of detectors and their movements (rotation) for possible maximum data collection at a faster rate.
Date: February 1, 1996
Creator: Lari, S.
Partner: UNT Libraries Government Documents Department

Residual stress measurement by successive extension of a slot: A literature review

Description: This report reviews the technical literature on techniques that employ successive extension of a slot and the resulting deformations to measure residual stress. Such techniques are known variously in the literature as the compliance or crack compliance method, the successive cracking method, the slotting method, and a fracture mechanics based approach. The report introduces the field and describes the basic aspects of these methods. The report then reviews all literature on the theoretical developments of the method. The theory portion first considers forward method solutions including fracture mechanics, finite element, analytical, and body force methods. Then it examines inverse solutions, including incremental inverses and series expansions. Next, the report reviews all experimental applications of slotting methods. Aspects reviewed include the specimen geometry and material, the details of making the slot, the method used to measure deformation, and the theoretical solutions used to solve for stress. Finally, the report makes a brief qualitative comparison between slotting methods and other residual stress measurement methods.
Date: May 1, 1997
Creator: Prime, M.B.
Partner: UNT Libraries Government Documents Department

Determination of residual stresses by local annealing to laser speckle pattern interferometry

Description: One of the most common methods of experimentally determining residual stresses is Blind Hole Drilling (BHD). A new method which is a thermo-optical analog to BHD is being developed. This method uses local heating to anneal a tiny spot and uses laser speckle interferometry to measure the strain that results. This strain is used to determine the state of stress prior to heating. The peak temperatures are on the order of 200 Celsius so that for most metals, there will be no changes in phase or other material properties except for a slight reduction in yield stress. Preliminary experiments with type 304 stainless steel were performed using resistance heating. The experimental results were in excellent agreement with finite element model predictions of the process. Subsequently, the resistance heating was replaced with laser heating. The heat input (22.5 Watt peak) from a small sealed radio frequency excited Carbon Dioxide laser was used. In order to both control the heating temperature and efficiently couple the infrared photons from the laser into the test specimen, a substance known as Liquid Temperature Indicating Paint was used. Without this substance the laser power would be so large as to make this approach impractical. Furthermore the measurement and control for the heat input would be very complicated. Using this laser heating approach was successful in obtaining similar results to those obtained in other work. Since this laser based technique is a thermo-optical analog to blind hole drilling a simple stress model is required to interpret the measured results. This simple stress model is presented. As in BHD, the simple model must be modified by empirical coefficients to be useful. These empirical coefficients are determined by experimentation and/or numerical analysis
Date: May 1, 1997
Creator: Pechersky, M. & Vikram, C.S.
Partner: UNT Libraries Government Documents Department

Evaluation of interfacial properties of fiber-reinforced ceramic composites

Description: The mechanical behavior of fiber-reinforced ceramic composites is closely related to their interfacial properties. The application of a single-fiber push-out test to evaluate these interfacial properties is addressed, and the stress-displacement relation during the push-out process is analyzed. The interfacial bonding, Coulomb friction at the debonded interface, Poisson`s effect of the loaded fiber, residual stresses, and the interfacial roughness effect are included in the analysis. Closed-form analytical solutions are obtained. Based on these analytical solutions, a methodology is established to extract the interfacial properties from the experimental fiber push-out curve.
Date: October 1, 1996
Creator: Hsueh, Chun-Hway
Partner: UNT Libraries Government Documents Department