Rp Reed

Tensile strength and ductility of indium

Abstract The tensile properties of indium were measured at temperatures ranging from 4 to 295 K. Indium recrystallizes during deformation at room temperature and twins during deformation at low temperatures. Strain-hardening characteristics were assessed, using true stress-strain curves, and were found to be similar to soft f.c.c. metals. The logarithm of the flow strength was dependent on temperature. Photomicrographs depicting deformation twinning and slip of indium at 76 and 295 K are discussed.

Compression and shear tests of vacuum-impregnated composites at cryogenic temperatures

To evaluate filament-reinforced, vacuum-impregnated, epoxy-resin systems at cryogenic temperatures, new compression-shear tests have been developed for stainless-composite-stainless sandwiches. Results at 76 K are reported and analyzed for a series of weaves and surface finishes.

Effects of Nb3Sn Heat Treatment on the Strength and Toughness of 316LN Alloys with Different Carbon Contents

A series of six 316LN-type alloys with different carbon contents were evaluated for suitability as conduit-sheath materials for the Nb3Sn superconductors that will be used in high-field magnets. Impact energies (at 76 to 295 K) and tensile strengths (at 4, 76, and 295 K) of annealed and “sensitized” alloys were compared. Embrittlement by aging at 700°C for 100 h (the Nb3Sn reaction conditions) was determined to be a function of carbon content; alloys with very low carbon content retained adequate toughness.

Recommended Changes in ASTM Test Methods D2512-82 and G86-84 for Oxygen-Compatibility Mechanical Impact Tests on Metals

A cooperative test program to assess the oxygen compatibility of aluminum-lithium alloys with NASA White Sands Test Facility (WSTF), NASA Marshall Space Flight Center (MSFC), and the National Institute of Standards and Technology (NIST) led to the assessment of the mechanical impact test by NIST. There were substantially different variations in test parameters between the test laboratories; some of these led to significant variability in the actual energy absorbed by the specimens. Therefore, test results varied widely. To reduce the large disparities in interlaboratory test results, a number of changes are recommended in the current ASTM test standards.

Tensile and fracture behavior of a nitrogen-strengthened, chromium-nickel-manganese stainless steel at cryogenic temperatures

J-integral fracture and conventional tensile properties are reported for an electroslag remelted Fe-21Cr-6Ni-9Mn austenitic stainless steel that contains 0.28 percent nitrogen as an interstitial strengthening element. Results at room (295 K), liquid-nitrogen (76 K), and liquid-helium (4 K) temperatures demonstrated that the yield strength and fracture toughness of this alloy are inversely related and strongly temperature dependent. Over the investigated temperature range, the yield strength tripled to 1.24 GPa (180 ksi) at 4 K. The fracture toughness, as measured using 3.8-cm-thick (1.5 in.) compact specimens, decreased considerably between 295 and 4 K. During plastic deformation at 295 K the alloy undergoes slight martensitic transformation, but at 76 and 4 K it transforms extensively to martensites. The amount of body-centered cubic (bcc) martensite formed during tension tests was measured as a function of elongation.

Creep of copper: 4–300 K

Abstract Creep measurements at 300, 76 and 4 K were conducted on C10400 copper. The specimens were held under a constant tensile load to give ratios of applied stress to yield strength in the range 0.8–2.0. The strain was measured using strain gages (sensitivities of 10 −6 ). Creep data were fitted by a non-linear least-squares procedure to a series of expressions that have been widely used to describe primary, transient, and steady-state conditions. No steady-state creep was observed, even at 300 K. Instead, at all temperatures, the time dependence of creep strain is best described as logarithmic. Activation volumes obtained from logarithmic creep analyses, from tensile strain-rate-change and stress relaxation measurements were compared. It was found that the constant α in the logarithmic creep expression is linearly dependent on the tensile strain-hardening rate at constant stress.

Low Temperature Fracture Behavior of Iron-Nickel Alloy Steels

Fracture toughness tests over the interval 298 to 4/sup 0/K and fatigue crack growth rate tests at 298, 111, and 76/sup 0/K are reported on selected iron--nickel (Fe--Ni) alloys which are commercially available for potential use in storage or transportation of liquefied natural gas (LNG). These alloys include Fe--6Ni and Fe--5Ni in newly developed three-step heat treatments and Fe--/sup 9/Ni in the quenched and tempered condition. Linear elastic fracture mechanics parameters (K/sub Q/, K/sub Ic/) and J-integral (J/sub Ic/) test data are presented for 1.25-in.-thick compact specimens. Discussion includes comparisons of fatigue crack growth rate and fracture data between alloys.

Incorrect representation of Barrier Canyon rock art site's history and other factors invalidate reported dates.

Recently, Pederson et al. reported on optically stimulated luminescence (OSL) and radiocarbon (RC) dating of a fallen rock in Horseshoe Canyon, Utah, that contains a pictograph (1). Unfortunately, the authors inexplicably imply that this site is pristine.

Strength/Toughness Relationship for Interstitially Strengthened AISI 304 Stainless Steels at 4 K Temperature

A study was conducted to determine the effects of carbon and nitrogen on the 4 K fracture properties of an Fe-18Cr-10Ni austenitic stainless steel having a base composition corresponding to AISI 304. J-integral fracture toughness tests using 24.5-mm-thick compact specimens (TL orientation) were performed in a liquid helium environment on nine steel heats having carbon plus nitrogen (C+N) contents between 0.067 and 0.325 weight percent. The fracture toughness decreased with increasing C+N content. The K I c estimates obtained at 4 K ranged from 337 to 123 MPa.m 1 / 2 , exhibiting an inverse dependence on tensile yield stress. A computer-aided J-integral test facility was implemented to conduct this study. This new facility improves measurement accuracy, conserves material specimens and testing time, and systematizes test procedures.

Deformation and Fracture of Al-Li Alloys in Mechanical-Impact Tests

Mechanical-impact tests in liquid and gaseous oxygen atmospheres aid in the assessment of Al-Li alloys for their use in cryogenic tankage for Advanced Launch Systems. In these tests, a falling plummet-striker pin assembly impacts a small disc specimen. Compressive, radial shear, and tensile (hoop) stresses are imparted to the disc specimens. The combination of these stresses and the high strain rate results in unique deformation and fracture characteristics. These characteristics include adiabatic shear bands, micro-cracking, specimen splitting, specimen heating (local melting), radial deformation in preferred orientations, and shear lips at the specimen-striker pin interface. These deformation and fracture modes are described and compared for various tempers of Al-Li alloys 8090, 2090, 2095, and alloy 2219. Distinctions between the Al-Li alloys and alloy 2219 are discussed.