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A series of total ionizing dose (TID) measurements were performed on commercial hard drives to explore the possible uses of the devices for the high radiation mission, and to help the understanding of the reliability of current hard drive technology. Three different models from three major manufacturers were tested with the aid of a commercial hard drive test system.
The effect of various quenching media on the hardness and microstructure of 60 NITINOL (60 NiTi) were evaluated. Specimens of 60 NiTi were heat treated in air at 1000 degC for 30 min or 2 hr, then quench cooled by one of seven different methods. The microstructure and hardness of this material was examined post heat treatment. The results indicated that the quench method had little effect on the resulting hardness and microstructure of 60 NiTi.
The Vickers hardness and second phase precipitation of three ternary intermetallic Ni-Ti-Hf compounds containing either 1, 3 or 5 at.% Hf were compared to 60-Nitinol (55 at.% Ni - 45 at.% Ti). Heat treatment either at 700 C or with a subsequent aging step, hardened the 3 and 5 at.% Hf-containing ternaries to approximately 620 HV (56 HRC). Heat treatment increased the hardness of the 1 at.% Hf compound by more than 25 percent. Average hardness of the 3 and 5 at.% Hf ternaries, though higher than that of the binary Ni-Ti or the Ni-Ti-Hf compound containing 1 at.% Hf, appeared to be fairly insensitive to the different heat treatments. There was a drastic reduction of fatigue-enhancing second phase precipitates for the 5 at.% Hf ternaries compared to the other compounds. These results should guide materials selection for development of aerospace componentry.
The effect of feed rate on the hardness and microstructure of a 7.35-mm-thick section from a spin-formed Al 6061 cylinder is investigated via microhardness mapping and electron backscatter diffraction (EBSD) analysis. The through-thickness hardness and microtexture profiles, corresponding to a true thickness strain of ≈ 0.3, are utilized to evaluate microstructural variations that could influence mechanical anisotropy and spin formability. The microhardness data reveal distinct gradients from the outer to the inner mold line that vary with feed rate and may be a function of the level of forming strain in the material. The microtextural mapping data expose a minor influence from feed rate, but contain trends through the material cross-section that suggest variations in the location-dependent stress states. The results demonstrate for the first time that the relationship between spin forming deformation and hardness or texture variations can be exploited to optimize processing parameters and mechanical response.
Hardness measurements of tool steel materials in electric furnace at elevated temperatures and low oxygen environment are discussed. Development of equation to predict short term hardness as function of intial room temperature hardness of steel is reported. Types of steel involved in the process are identified.
The effects of alloy additions of zirconium, hafnium, molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, and iridium on the hardness of niobium was determined. Both binary and ternary alloys were investigated by means of hardness tests at 77 K and 300 K. Results showed that atomic size misfit plays a dominant role in controlling hardness of binary niobium alloys. Alloy softening, which occurred at dilute solute additions, is most likely due to an extrinsic mechanism involving interaction between solute elements and interstitial impurities.
An investigation was conducted to determine the effects of alloy additions of zirconium, hafnium, molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, and iridium on the hardness of niobium. Both binary and ternary alloys were investigated by means of hardness tests at 77 and 300 K. Results showed that atomic size misfit plays a dominant role in controlling the hardness of binary niobium alloys. Alloy softening, which occurred at dilute solute additions, is most likely due to an extrinsic mechanism involving interaction between solute elements and interstitial impurities.
The paper reviews the observations of solar X-rays in the range 1-100 keV made by the solar X-ray instrument on board the OSO-7 satellite and explores the relationship between the hard and soft X-ray components in order to glean some information on the physics of solar flares. Some of the results are as follows: The growth of the soft X-ray emission in a burst must be due to the addition of new hot material to the flare plasma. The anticorrelation between cooling time and maximum plasma temperature gives new evidence to support conduction as the principal cooling mechanism of the hot flare plasma. Observations of hard X-ray emission from bursts which occurred behind the limb indicate that hard X-ray emission comes at least in part from considerable heights in the corona.
Rockwell A hardness of cast nickel-chromium-aluminum (NiCrAl) alloys was examined from ambient to 1150 K and compared to cast NiAl and IN-100. Alloy constitution was either gamma, gamma prime + gamma or gamma + beta + alpha + gamma prime. Below 1000 K beta containing NiCrAl alloys have hardnesses comparable to IN-100; above 1000 K they soften faster than IN-100. At 1150 K the hardness of beta-containing NiCrAl alloys decreases with increasing beta-content. The beta-containing NiCrAl alloys were harder than beta-NiAl. The ultimate tensile strengths of the NiCrAl alloys were estimated. The effects of NiCrAl coatings on strength and fatigue life of cooled turbine components were deduced.
Results are reported for OSO 7 observations of 3U 0352+30 (X Per) over the energy range from 7 to 110 keV. It is found that this source has either a hard power-law spectrum or a thermal bremsstrahlung spectrum over the observed energy range, indicating that X Per may be the prototype of a new class of weak galactic hard X-ray sources. The data are shown to be consistent with spectra calculated for accretion onto a degenerate dwarf of at least 1 solar mass. Geometrical and dynamical constraints are considered for a model in which an accreting degenerate dwarf is in a close orbit about the primary of X Per, and it is concluded that such a model is not ruled out at present. It is suggested that X-ray sources associated with Be stars may make a significant contribution to the diffuse hard X-ray background in the galactic plane.
Data from the University of California at San Diego (UCSD) hard X-ray instrument on OSO-7 have been used to search the regions containing 3C 390.3, M87, 3C 273, 3C 111, and 3C 129. We have a weak detection of 3C 390.3 and a possible detection of 3C 111. Sensitive upper limits on hard X-rays have been obtained for the other objects. The available observational data indicate a correlation between hard X-ray emission, self-absorbed gigahertz radio emission, and strong optical emission lines in extragalactic sources. Self-Compton X-ray models have been calculated for the sources observed in this paper, and the angular sizes, lifetimes, and B fields in these sources have been estimated. These model calculations agree with existing VLBI and time variability data.
The hard X-ray emission from 28 large solar events has been analyzed in order to search for pulsations in intensity profiles. Periodicity occurred in 26 events, usually soon after the onset, with periods in the range 10-100 s. Pulsations occurring at common frequencies in different energy bands are observed to be closely in phase. Periodic behavior in hard X-ray emission is related to that at microwave and decametric wavelengths. The observations are briefly discussed in terms of two models: that of McClean et al. (1971), applied to X-ray emission, and that of Brown and Hoyng (1975). As periodicity is normal in extended hard X-ray bursts and occurs through a broad energy band, it is probably directly related to a principal flare-acceleration mechanism. These observations constrain possible mechanisms of flare acceleration and physical properties of the acceleration region.
Hard X-ray emission from a 15 min by 1.5 deg area containing SS Cygni had previously been reported and identified with SS Cygni. This paper reports a 0.4 sq arc min measurement of the position of the X-ray source with the HEAO 1 modulation collimator experiment which leads to an unequivocal identification of SS Cygni as an X-ray emitter in the 2-10 keV energy range. The historical light curve in hard X-rays was also investigated by analyzing relevant Uhuru data, and two instances of possible source detection in the 2-6 keV band were noted. From Ariel 5 observations it is calculated that the X-ray luminosity of SS Cygni in the 2-10 keV energy range is of the order of 10 to the 33rd erg/sec in the optical low state and probably at least an order of magnitude less in the high state. By contrast, the soft X-ray luminosity increases by an order of magnitude between the optical low and high states. A coronal model or accretion onto the white dwarf can account for the inverse correlation of the soft and hard X-rays.
The impulsive solar hard X-ray spectrum provides a direct diagnostic on the impulsive energy release of the flare. The data from the hard X-ray (14-342 keV) spectrometer on OSO 7 have been examined for events covering a wide energy range to determine the photon spectrum more precisely. This resulted in a sample of 38 events. The data have been fitted with either single- or double-power laws, and with an exponential spectrum, as from thermal bremsstrahlung. The chi-squared statistic between two-parameter fits strongly favors the exponential fit, particularly at peak intensity when the widest energy range is sampled. This result supports a single-temperature thermal source of the impulsive solar hard X-rays with temperatures in the range 4.7-31 keV and emission measures in the range from 8.4 x 10 to the 43rd to 6.0 x 10 to the 46th per cu cm. The temperature reaches a single maximum and then rapidly decays, but the emission measure usually increases throughout, even after temperature maximum, for data with 10-s resolution.
The height structure of hard X-ray bremsstrahlung emission in solar flares is computed for two different models of bremsstrahlung production: emission from a descending beam of nonthermal electrons, and thermal emission from a coronally confined hot plasma. It is shown how these models give rise to hard X-ray spatial distributions which are distinguishable by current instrumentation, and that, therefore, the models may be distinguished by such spatially resolved hard X-ray measurements.
Coded aperture X-ray detectors were applied to obtain large increases in sensitivity as well as angular resolution. A hard X-ray coded aperture detector concept is described which enables very high sensitivity studies persistent hard X-ray sources and gamma ray bursts. Coded aperture imaging is employed so that approx. 2 min source locations can be derived within a 3 deg field of view. Gamma bursts were located initially to within approx. 2 deg and X-ray/hard X-ray spectra and timing, as well as precise locations, derived for possible burst afterglow emission. It is suggested that hard X-ray imaging should be conducted from an Explorer mission where long exposure times are possible.
Isolated and grouped type III bursts have been observed in temporal association with impulsive hard X-ray bursts in the 26-154 keV range, down to frequencies as low as 30 MHz and out to a distance of 3.1 solar radii from the disk center. The bursts occurred in regions whose electron density may have been as much as 20 times higher than that of the Newkirk-Saito model. The present observations indicate that electron acceleration/injection occurs over a region covering a wide range of magnetic field lines. It is noted that, of the two gradual hard X-ray bursts observed in association with type IV bursts, one was accompanied by a type II event, while the other was not, although both exhibited the same characteristics. It is suggested that the gradual burst associated with a type IV only involved electrons which are trapped in the plasmoid which produces the meter-decameter emission, while another fraction of the population is trapped in the low-lying loops which produce the hard X-ray and centimeter radiation.
The results of a search for fast spikes in 2830 hard X-ray solar flares as observed with the hard X-ray burst spectrometer on the Solar Maximum Mission (SMM) are presented. Hundreds of fast spikes with durations of less than 1 sec have been detected at time resolutions of 128 msec and 10 msec. Fast spikes have been detected with rise and decay times as short as 20 msec and with widths as short as 45 msec. They are the fastest hard X-ray variations yet seen from the sun. The observations of such fast variations place new constraints on the physical nature of the source, and these observations and constraints are discussed in terms of nonthermal and thermal models of flares.