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The Ductility of Brazed Stainless Steel Joints

Description: Abstract: "The ductility of Type 310 stainless steel T-joints brazed with GE-62 brazing alloy was measured at room temperatures 1200, 1650, and 1800 F. The measure of ductility was taken as the plastic axial strain required to crack braze fillets in T-section tensile specimens. At elevated temperatures, the ductility of as-brazed joints approximated that of the stainless steel, but at room temperature the brazed joints had only one-tenth the ductility of the base metal. Annealing for 16 hr at 1800 F in air was found to triple the room-temperature ductility of the brazed joint."
Date: July 8, 1953
Creator: Saller, Henry A.; Stacy, J. T. & Eddy, N. S.
Partner: UNT Libraries Government Documents Department

A Model for Radiation Damaged Ductile Metals

Description: Abstract: "A model is presented for radiation damage to ductile metals that accounts qualitatively for the effects of radiation on the electrical and mechanical properties. The model consists of an agglomeration of interstitially displaced atoms into stacking faults in the lattice."
Date: June 10, 1953
Creator: Holden, A. N. & Kunz, F. W.
Partner: UNT Libraries Government Documents Department

Elastic stability and the limit of strength

Description: The upper limit of strength (the ''theoretical strength'') has been an active subject of research and speculation for the better part of a century. The subject has recently become important, for two reasons. First, given recent advances in ab initio techniques and computing machines, the limits of strength can be calculated with considerable accuracy, making this one of the very few problems in mechanical behavior that can actually be solved. Second, given recent advances in materials engineering, the limits of strength are being approached in some systems, such as hardened or defect-free films, and their relevance is becoming recognized in others. The present paper discusses some interesting results from recent research on the limits of strength, with an intermixture of speculations based on those results. Topics include the inherent nature of {l_brace}100{r_brace} cleavage and ''pencil slip'' in bcc metals, the inherent ductility of fcc metals, the anomalous properties of Al, and the possibility of measuring ideal strength with nanoindentation.
Date: July 1, 2002
Creator: Morris Jr., J.W.; Krenn, C.R.; Roundy, D. & Cohen, Marvin L.
Partner: UNT Libraries Government Documents Department

Ductility Characterization of U-6Nb and Ta-W Alloys

Description: We have previously evaluated the ductility behaviors of U-6Nb and pure Ta. One important observation was that both alloys have very stable necking ductility independent of test conditions. In contrast, uniform ductility varied significantly depending upon strain rates and temperatures. In general, higher strain rate and lower temperature reduce the uniform ductility. Using literature data, we have developed two dynamic ductility models to predict the ductility behaviors of pure-Ta and water-quenched U-6Nb respectively under extreme conditions. In this study we further evaluate the aging effect on U-6Nb and the W-addition effect on Ta. For U-6Nb, the objective is to determine whether or not the ductility degradation by low-temperature aging mostly measured in quasi-static condition can still be observed under dynamic loading (high strain rate) condition. For Ta-W alloys, the focus is to identify the key control parameter so that the optimal condition of high-strength/high-ductility of Ta-10W can be achieved for certain defense-related applications.
Date: September 15, 2006
Creator: Sun, T & Cervantes, O
Partner: UNT Libraries Government Documents Department

CONSTRAINT EFFECT IN FRACTURE WHAT IS IT

Description: The meaning of the phrase 'constraint effect in fracture' has changed in the past two decades from 'contained plasticity' to a broader description of 'dependence of fracture toughness value on geometry of test specimen or structure'. This paper will first elucidate the fundamental mechanics reasons for the apparent 'constraint effects in fracture', followed by outlining a straightforward approach to overcoming this problem in both brittle (elastic) and ductile (elastic-plastic) fracture. It is concluded by discussing the major difference in constraint effect on fracture event in elastic and elastic-plastic materials.
Date: October 29, 2008
Creator: Lam, P & Prof. Yuh J. Chao, P
Partner: UNT Libraries Government Documents Department

Ductile damage model with void coalescence

Description: A general model for ductile damage in metals is presented. It includes damage induced by shear stress as well as damage caused by volumetric tension. Spallation is included as a special case. Strain induced damage is also treated. Void nucleation and growth are included and give rise to strain rate effects. Strain rate effects also arise in the model through elastic release wave propagation between damage centers. Underlying physics of the model is the nucleation, growth, and coalescence of voids in a plastically flowing solid. Implementation of the model in hydrocodes is discussed.
Date: March 1, 1995
Creator: Tonks, D.L.
Partner: UNT Libraries Government Documents Department

Synthesis, characterization and mechanical properties of nanocrystalline NiAl

Description: Nanocrystalline NiAl was produced from pre-cast alloys using an electron beam inert gas condensation system. In-situ compaction was carried out at 100-300 C under vacuum conditions. Energy dispersive spectroscopy was used to determine chemical composition and homogeneity. Average grain sizes in the range 4-10 nm were found from TEM dark field analyses. A compression-cage fixture was designed to perform disk bend tests. These tests revealed substantial room temperature ductility in nanocrystalline NiAl, while coarse grained NiAl showed no measurable room temperature ductility.
Date: November 1, 1996
Creator: Choudry, M.; Eastman, J.A.; DiMelfi, R.J. & Dollar, M.
Partner: UNT Libraries Government Documents Department

Importance of Deviatoric Stress in Modeling Void Growth in Ductile Fracture

Description: In this paper, the authors extend an upper bound result of Cocks [1989] to obtain a formula for porosity growth in ductile metals. Pressure and deviatoric stress are included. The matrix plasticity model involves the plastic strain rate as a power of the deviatoric stress, with a yield stress. The results show that the deviatoric stress cannot be neglected in calculating the porosity growth, even for high triaxialities.
Date: January 1, 1999
Creator: Tonks, D.L.; Zurek, A.K.; Thissell, W.R.; Rivera, J.M. & Hixson, R.S.
Partner: UNT Libraries Government Documents Department

Nb3Sn accelerator magnet development around the world

Description: During the past 30 years superconducting magnet systems have enabled accelerators to achieve energies and luminosities that would have been impractical if not impossible with resistive magnets. By far, NbTi has been the preferred conductor for this application because of its ductility and insensitivity of Jc to mechanical strain. This is despite the fact that Nb{sub 3}Sn has a more favorable Jc vs. B dependence and can operate at much higher temperatures. Unfortunately, NbTi conductor is reaching the limit of it usefulness for high field applications. Despite incremental increases in Jc and operation at superfluid temperatures, magnets are limited to approximately a 10 T field. Improvements in conductor performance combined with future requirements for accelerator magnets to have bore fields greater than 10 T or operate in areas of large beam-induced heat loads now make Nb{sub 3}Sn look attractive. Thus, laboratories in several countries are actively engaged in programs to develop Nb{sub 3}Sn accelerator magnets for future accelerator applications. A summary of this important research activity is presented along with a brief history of Nb{sub 3}Sn accelerator magnet development and a discussion of requirements for future accelerator magnets.
Date: June 23, 2003
Creator: Lamm, Michael J.
Partner: UNT Libraries Government Documents Department

In-situ Fracture Studies and Modeling of the Toughening Mechanism Present in Wrought LCAC, TZM, and ODS Molybdenum Flat Products

Description: In-situ testing, ultrasonic C-scans, and metallography were used to show that a crack-divider delamination form of thin-sheet toughening occurs in wrought Low Carbon Arc Cast (LCAC) unalloyed molybdenum, Oxide Dispersion Strengthened (ODS) molybdenum, and TZM molybdenum at temperatures {ge} the Ductile to Brittle Transition Temperature (DBTT). Cracking along boundaries relieves mechanical constraint to free ligaments that may plastically stretch to produce toughening. Anisotropy in fracture toughness with lower values in the short-transverse direction is shown to produce the crack divider delaminations at the crack tip in the LT and TL orientations. The delamination zone increases with increasing stress-intensity to sizes significantly larger than the plastic zone, which leads to large increases in fracture toughness by the thin sheet toughening mechanism. Fracture in ODS Mo-alloys proceeds mainly along grain boundaries to produce small ligaments that exhibit ductility for both LT and TL orientations resulting in a lower DBTT and higher toughness values at lower temperatures than observed in LCAC and TZM. A combination of grain boundary fracture and cleavage is prevalent in LCAC molybdenum and TZM. The predominance for microcracking along grain boundaries to leave fine, ductile ligaments in ODS molybdenum can be attributed to a fine-grained microstructure with {approx} 1-2 {micro}m thickness of sheet-like grains. The presence of mixed grain boundary fracture and cleavage in LCAC and TZM can be attributed to a microstructure with a larger thickness of sheet-like grains (4-15 {micro}m).
Date: July 1, 2007
Creator: Cockerman, B. V. and Chan, K. S.
Partner: UNT Libraries Government Documents Department

CREEP AND CORROSION PROPERTIES OF ZIRCALOY-2 IN STEAM AT 750 F

Description: Test equipment to determine the creep properties of Zircaloy-2 in a 750 deg F 500-psi steam atmosphere was designed and constructed. Duplicate tests were performed at stresses to produce failure in approximately 1, 10, 100, and 1000 hr. A comparison between these data and data obtained in vacuum-test equipment showed that a corrosive test atmosphere does not alter ductility or failure times appreciably. (auth)
Date: August 1, 1960
Creator: Jablonowski, E.J. & Shober, F.R.
Partner: UNT Libraries Government Documents Department

Influence of temperature and strain rate on the compressive behavior of PMMA and polycarbonate polymers

Description: Compression stress-strain measurements have been made on commercial polymethylmethacrylate (PMMA) and polycarbonate (PC) polymers as a function of tcmperature (-197 C to 220 C) and strain rate. A split-Hopkinson-pressure bar (SJIPU) was used to achieve strain rates of about 2500 s-' and a servohydraulic tester was used for lower strain rate testing (0.001 to 5 s-'). The mechanical response of these transparent polymers is quite different. The strength of PC is weakly dependent on strain rate, only moderately dependent on temperature, and remains ductile to -197OC. In contrast, the strength of PMMA is linearly dependent on temperature and strongly dependent on strain rate. Significantly, PMMA develops cracking and fails in compression with little ductility ( 7 4 % total strain) at either low strain rates and very low temperatures (-197OC) or at high strain rates and temperatures very near ambient.
Date: January 1, 2001
Creator: Cady, C. M. (Carl McElhinney); Lopez, M. F. (Mike F.); Gray, G. T. (George T.), III; Idar, D. J. (Deanne J.) & Blumenthal, W. R. (William R.)
Partner: UNT Libraries Government Documents Department

TRITIUM RESERVOIR STRUCTURAL PERFORMANCE PREDICTION

Description: The burst test is used to assess the material performance of tritium reservoirs in the surveillance program in which reservoirs have been in service for extended periods of time. A materials system model and finite element procedure were developed under a Savannah River Site Plant-Directed Research and Development (PDRD) program to predict the structural response under a full range of loading and aged material conditions of the reservoir. The results show that the predicted burst pressure and volume ductility are in good agreement with the actual burst test results for the unexposed units. The material tensile properties used in the calculations were obtained from a curved tensile specimen harvested from a companion reservoir by Electric Discharge Machining (EDM). In the absence of exposed and aged material tensile data, literature data were used for demonstrating the methodology in terms of the helium-3 concentration in the metal and the depth of penetration in the reservoir sidewall. It can be shown that the volume ductility decreases significantly with the presence of tritium and its decay product, helium-3, in the metal, as was observed in the laboratory-controlled burst tests. The model and analytical procedure provides a predictive tool for reservoir structural integrity under aging conditions. It is recommended that benchmark tests and analysis for aged materials be performed. The methodology can be augmented to predict performance for reservoir with flaws.
Date: November 10, 2005
Creator: Lam, P.S. & Morgan, M.J
Partner: UNT Libraries Government Documents Department

Evolution, Interaction, and Intrinsic Properties of Dislocations in Intermetallics: Anisotropic 3D Dislocation Dynamics Approach

Description: The generation, motion, and interaction of dislocations play key roles during the plastic deformation process of crystalline solids. 3D Dislocation Dynamics has been employed as a mesoscale simulation algorithm to investigate the collective and cooperative behavior of dislocations. Most current research on 3D Dislocation Dynamics is based on the solutions available in the framework of classical isotropic elasticity. However, due to some degree of elastic anisotropy in almost all crystalline solids, it is very necessary to extend 3D Dislocation Dynamics into anisotropic elasticity. In this study, first, the details of efficient and accurate incorporation of the fully anisotropic elasticity into 3D discrete Dislocation Dynamics by numerically evaluating the derivatives of Green's functions are described. Then the intrinsic properties of perfect dislocations, including their stability, their core properties and disassociation characteristics, in newly discovered rare earth-based intermetallics and in conventional intermetallics are investigated, within the framework of fully anisotropic elasticity supplemented with the atomistic information obtained from the ab initio calculations. Moreover, the evolution and interaction of dislocations in these intermetallics as well as the role of solute segregation are presented by utilizing fully anisotropic 3D dislocation dynamics. The results from this work clearly indicate the role and the importance of elastic anisotropy on the evolution of dislocation microstructures, the overall ductility and the hardening behavior in these systems.
Date: August 18, 2008
Creator: Chen, Qian
Partner: UNT Libraries Government Documents Department

Roles of nanoclusters in shear banding and plastic deformation of bulk metallic glasses

Description: During the course of this research we published 33 papers in various physics/material journals. We select four representing papers in this report and their results are summarized as follows. I. To study shear banding process, it is pertinent to know the intrinsic shear strain rate within a propagating shear band. To this aim, we used nanoindentation technique to probe the mechanical response of a Au49Ag5.5Pd2.3Cu26.9Si16.3 bulk metallic glass in locality and found notable pop-in events associated with shear band emission. Using a free volume model and under the situation when temperature and stress/hardness are fixed result in an equation, which predicts that hardness serration caused by pop-in decreases exponentially with the strain rate. Our data are in good agreement with the prediction. The result also predicts that, when strain rate is higher than a critical strain rate of 1700 s^-1, there will be no hardness serration, thereby no pop-in. In other words, multiple shear bandings will take place and material will flow homogeneously. The critical strain rate of 1700 s^-1 can be treated as the intrinsic strain rate within a shear band. We subsequently carried out a simulation study and showed that, if the imposed strain rate was over , the shear band spacing would become so small that the entire sample would virtually behave like one major shear band. Using the datum strain rate =1700 s^-1 and based on a shear band nucleation model proposed by us, the size of a shear-band nucleus in Au-BMG was estimated to be 3 × 10^6 atoms, or a sphere of ~30 nm in diameter. II. Inspired by the peculiar result published in a Science article “Super Plastic Bulk Metallic Glasses at Room Temperature”, we synthesized the Zr-based bulk metallic glass with a composition identical to that in the paper (Zr64.13Cu15.75Ni10.12Al10) and, subsequently, ...
Date: July 31, 2012
Creator: Nieh, T.G.
Partner: UNT Libraries Government Documents Department

TRANSIENT LOADING OF THIN-WALLED CYLINDERS. Interim Technical Report

Description: The effect of internal static loading and internal transient loading on the deformation of thin-walled tube specimens was studied for both the elastic and plastic regions. The specimens employed were six inch sections of type 304, seamless, stainless steel tubing having a nominal O.D. and wall thickness of 3/4 inch and 0.020 inch, respectively. The transient forces were obtained from detonations of stoichiometric hydrogen-oxygen mixtures contained in a shocktype detonation tube. Each specimen was postfixed to the detonation tube and then acted as an extension of the tube. The detonation wave travelled through the system and exerted on the specimen walls a strain from either a single incident wave pressure or from an incident plus reflected wave pressure combination, depending upon the apparatus used to cap the downstream end of the specimen. Strains in the elastic region were measured with bonded electric resistance strain gages, while strains in the post-yield region were measured with a micrometer. The static loading forces were obtained from high pressure oil fed from a hydraulic pump into the specimen. The Young's Modulus of Elasticity for transient loading was 1.22 times greater than for static loading. Similarly, the 0.2 percent offset yield strength for the incident detonation wave transient loading case and for the incident plus refiected detonation wave transient loading case were 1.41 and 1.50, respectively, times the static yield strength. The results of this investigation indicated that as the time of force application decreased, the ability of type 304 stainless steel to resist deformation increased. In other words, the specimen exhibited a much higher value of toughness, elastic resilience and hyper-elastic resilience when loaded by a transient force than when loaded statically. (auth)
Date: August 1, 1957
Creator: Mosier, S.A.
Partner: UNT Libraries Government Documents Department

THE PRESENT STATE OF DEVELOPMENT OF IRON-ALUMINUM-BASE ALLOYS

Description: The purpose of this memorandum is to summarize the present state of development of iron-- aluminum-base alloys. The binary iron--aluminum alloys offer favorable tensile strength but possess very poor ductility. The iron-- aluminum -- molybdenum alloy, thermenol (Fe -16A1--3 Mo), is corrosion resistant, offers excellent tensile strength, and is ductile. (A.C.)
Date: November 18, 1957
Creator: Lepkowski, W.J. & Holladay, J.W.
Partner: UNT Libraries Government Documents Department

LOW CROSS-SECTION IRON-BASE ALLOYS

Description: Data are presented on the mechanical properties of iron-silicon and iron- aluminum alloys in the range 0 to 14% Si and about 8% aluminum. The effect of third elements on ductility is discussed, and data are prcsented which indicate that it is not possible to obtain a disordered structure in Fe--Si a1loys from 8 to 14% Si. It is concluded that alloys of iron with 6 to 8% aluminum offer a promising base composition for development of low neutron cross section alloys for use in nuclear reactors. (auth)
Date: July 1, 1957
Creator: Lillie, D.W.
Partner: UNT Libraries Government Documents Department