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Variation of the yield strength and strain-rate sensitivity exponent of type 21-6-9 stainless steel over a wide temperature range

Description: The yield strength of solution-annealed 21-6-9 austenitic stainless steel was determined over a wider temperature range (-195 to 1100/sup 0/C) than has been previously reported. The most noteworthy characteristic of the variation of yield stress with temperature was the dramatic decrease in yield strength from -195/sup 0/C to 300/sup 0/C. The strain-rate sensitivity exponent, N, was determined using strain-rate change tests. A plot of N vs temperature showed that n dramatically increased at about 850/sup 0/C and that N is approximately independent of strain (structure). 3 figures.
Date: November 15, 1982
Creator: Kassner, M.E.
Partner: UNT Libraries Government Documents Department

Yield stress of type 21-6-9 stainless steel over a wide range of strain rate (10/sup -5/ to 10/sup -4/ s/sup -1/) and temperature

Description: This document reports the effects of high strain rate (10/sup 2/ to 10/sup 4/ s/sup -1/) on the yield strength of 21-6-9 austenitic stainless steel. The reported yield stresses are appropriate to the temperature range from ambient to 750/sup 0/C. The high strain-rate stresses were determined from Hopkinson split-bar tests. The high strain-rate data are compared to the strength of 21-6-9 of identical structure and composition at lower rates (e.g., 10/sup -4/ s/sup -1/). Such comparison provides insight into the rate dependence, at various temperatures to 750/sup 0/C, of plastic flow over a wide range (eight orders of magnitude) of strain rate.
Date: July 1, 1983
Creator: Kassner, M.E. & Breithaupt, R.D.
Partner: UNT Libraries Government Documents Department

Yield stress of Type 21-6-9 stainless steel over a wide range of strain rate (10/sup -5/ to 10/sup 4/ s/sup -1/) and temperature

Description: Hopkinson split-bar tests were performed on Type 21-6-9 austenitic stainless steel from ambient temperature to 1023 K. These high-strain-rate tests (10/sup 2/ to 10/sup 4/ s/sup -1/) were compared with lower-strain-rate tests (10/sup -4/ s/sup -1/). The results indicate that over this temperature range, the strain-rate sensitivity of 21-6-9 is not strongly dependent on the strain rate. This suggests that the mechanism(s) of plastic flow at the higher rates is similar to that at the lower rates. This contention was corroborated by transmission electron microscopy.
Date: September 23, 1983
Creator: Kassner, M.E. & Breithaupt, R.D.
Partner: UNT Libraries Government Documents Department

Fatigue expectations in a molybdenum/silicon multilayer under pulsed soft X-ray radiation

Description: The temperature rise in a Mo/a-Si multilayer x-ray reflective film due to radiation absorption is modeled for the first condenser mirror in a projection lithography system such as the one designed by the Advanced Microtechnology Program at LLNL. The radiation load is pulsed at 1000 Hz with a time average intensity of 500mW/cm{sup 2}. This intensity is the expected maximum on the first condenser mirror. The temperature rise is calculated using the integral transform technique. The film is assumed to have the thermal properties of its poorly conducting substrate, yielding a more conservative (higher) temperature estimate. The surface temperature rise is found to range between 35.6{degrees}C and 76.3{degrees}C. The stress due to this rise is greatest in the molybdenum film and ranges between 73MPa and 166MPa compressive. This fluctuating stress level, however, is believed to be insufficient, by a factor of five or so, to cause fatigue failure of the film.
Date: January 19, 1995
Creator: Weber, F.J.; Kassner, M.E. & Stearns, D.G.
Partner: UNT Libraries Government Documents Department

Elastic incompatibility stresses across planar and nonplanar grain boundaries in silver, aluminum, and zirconium applied to ductile fracture criteria under high triaxial stress

Description: Grain boundaries in a polycrystal imply elastic incompatibilities that can lead to stress states in the vicinity of the interface that are different from the macroscopic or applied stresses because the single crystal elastic properties are not all isotropic. This phenomenon is important as mechanical processes may operate at the microscopic level that would not be predicted based on the macroscopic stress state. This phenomenon has not been widely examined. One of the few studies that examined the level of stress- state modification on copper determined that slip or plasticity in cyclically deformed copper occurred in areas with high elastic incompatibility stresses. The focus of the present study is the unstable growth of cavities as a result of high local triaxial stress. Grain boundaries in silver, aluminum, and zirconium are examined.
Date: July 1, 1996
Creator: Roehnelt, R.; Kassner, M.E.; Kennedy, T.C. & Rosen, R.S.
Partner: UNT Libraries Government Documents Department

High temperature properties of alloys being considered for design of a concentric canister launcher

Description: This report describes a study to determine the high temperature mechanical properties of several titanium alloys and to compare them with properties of AISI 316L stainless steel and ASTM A 387 structural steel. The steel materials are less costly to procure but exhibit good resistance to corrosion in seawater environments. Six titanium alloys were evaluated as candidate materials for use in a c Concentric Canister Launcher (CCL). Each titanium alloy was tested at three temperatures (68°, 2000°F, and 2400°F). Strain-rate changes tests were used to determine the strain rate sensitivity of the alloys at each test temperature. Optical metallography was performed on two of the alloys to determine the relationship between test temperature and microstructure (presence of second phase precipitates, grain size). Complete test results are includes, a long with figures and tables of test data.
Date: June 1, 1998
Creator: Kassner, M E; Lowry, R W & Rosen, R S
Partner: UNT Libraries Government Documents Department

Critical Analysis of Dry Storage Temperature Limits for Zircaloy-Clad Spent Nuclear Fuel Based on Diffusion Controlled Cavity Growth

Description: Interim dry storage of spent nuclear fuel (SNF) rods is of critical concern because a shortage of existing SNF wet storage capacity combined with delays in the availability of a permanent disposal repository has led to an increasing number of SNF rods being placed into interim dry storage. Safe interim dry storage must be maintained for a minimum of twenty years according to the Standard Review Plan for Dry Cask Storage Systems [1] and the Code of Federal Regulations, 10 CFR Part 72 [2]. Interim dry storage licensees must meet certain safety conditions when storing SNF rods to ensure that there is a ''very low probability (e.g. 0.5%) of cladding breach during long-term storage'' [1]. Commercial SNF typically consists of uranium oxide pellets surrounded by a thin cladding. The cladding is usually an {alpha}-zirconium based alloy know as ''Zircaloy''. In dry storage, the SNF rods are confined in one of several types of cask systems approved by the Nuclear Regulatory Commission (NRC). ''The cask system must be designed to prevent degradation of fuel cladding that results in a type of cladding breach, such as axial-splits or ductile fracture, where irradiated UO{sub 2} particles may be released. In addition, the fuel cladding should not degrade to the point where more than one percent of the fuel rods suffer pinhole or hairline crack type failure under normal storage conditions [1].'' The NRC has approved two models [3,4] for use by proposed dry storage licensees to determine the maximum initial temperature limit for nuclear fuel rods in dry storage that supposedly meet the above criteria and yield consistent temperature limits. Though these two models are based on the same fundamental failure theory, different assumptions have been made including the choice of values for material constants in the failure equation. This report will examine ...
Date: December 1, 1999
Creator: Hayes, T.A.; Rosen, R.S. & Kassner, M.E.
Partner: UNT Libraries Government Documents Department

Thermal stability of Mo/Si multilayers

Description: The thermal stability of Mo/Si multilayers for x-ray mirror applications was investigated by annealing studies at relatively low temperatures for various times. The as-deposited and annealed multilayers were examined using conventional small and large angle x-ray diffraction, normal incidence x-ray reflectance measurements using a synchrotron source, selected area electron diffraction, and high-resolution electron microscopy. The as-deposited structure consists of pure layers of crystalline Mo and amorphous Si separated by thin regions of amorphous Mo-Si. At temperatures between 200--400{degrees}C, the amorphous Mo-Si interlayers grow and hexagonal MoSi{sub 2} forms by a thermally activated process(es), and the bilayer spacing and x-ray reflectivity decrease. A determination of the effective activation energy of the process(es) suggests long-term stability at the mirror operating temperature, although additional low temperature testing is warranted. 11 refs., 5 figs., 2 tabs.
Date: July 1, 1991
Creator: Rosen, R.S.; Stearns, D.G. (Lawrence Livermore National Lab., CA (United States)); Viliardos, M.A.; Kassner, M.E. (Oregon State Univ., Corvallis, OR (United States). Dept. of Mechanical Engineering) & Vernon, S.P. (Vernon Applied Physics, Torrance, CA (United States))
Partner: UNT Libraries Government Documents Department