Comparison of Flaw Growth Characteristics Under Cryogenic Proof and Ambient Test Conditions for Apollo Titanium Pressure Vessels

Comparison of flaw growth characteristics under cryogenic proof and ambient test conditions for Apollo titanium pressure vessel

Fracture characteristics of 6 AL-4V titanium alloy forgings containing alpha stringer microstructure Final report, 10 Sep. 1968 - 24 Jan. 1969

Fracture characteristics of 6Al-4V titanium alloy forgings containing alpha stringer microstructur

Deep flaws in weldments of aluminum and titanium

Surface flawed specimens of 2219-T87 and 6Al-4V STA titanium weldments were tested to determine static failure modes, failure strength, and fatigue flaw growth characteristics. Thicknesses selected for this study were purposely set at values where, for most test conditions, abrupt instability of the flaw at fracture would not be expected. Static tests for the aluminum weldments were performed at room, LN2 and LH2 temperatures. Titanium static tests for tests were performed at room and LH2 temperatures. Results of the static tests were used to plot curves relating initial flaw size to leakage- or failure-stresses (i.e. "failure" locus curves). Cyclic tests, for both materials, were then performed at room temperature, using initial flaws only slightly below the previously established failure locus for typical proof stress levels. Cyclic testing was performed on pairs of specimens, one with and one without a simulated proof test cycle. Comparisons were made then to determine the value and effect of proof testing as affected by the various variables of proof and operating stress, flaw shape, material thickness, and alloy

Fracture characteristics of structural aerospace alloys containing deep surface flaws

Conditions controlling the growth and fracture of deep surface flaws in aerospace alloys were investigated. Static fracture tests were performed on 7075-T651 and 2219-T87 aluminum, and 6Ai-4V STA titanium . Cyclic flaw growth tests were performed on the two latter alloys, and sustain load tests were performed on the titanium alloy. Both the cyclic and the sustain load tests were performed with and without a prior proof overload cycle to investigate possible growth retardation effects. Variables included in all test series were thickness, flaw depth-to-thickness ratio, and flaw shape. Results were analyzed and compared with previously developed data to determine the limits of applicability of available modified linear elastic fracture solutions

Investigation of crack growth threshold of Inconel 718 exposed to high pressure oxygen Final report 24 Apr. - 25 May 1970

Crack growth threshold investigation of Inconel 718 exposed to high pressure oxyge

Effects of hypnotic drugs on performance before and after sleep

The effects of various hypnotics on sleep stage parameters and on the parameters of effectiveness were evaluated along with the effects of several commonly used yet distinctly different hypnotics on daytime performance. The effects on daytime performance of two nonhypnotics commonly used in the space program were also examined

A narrow-band speckle-free light source via random Raman lasing

Currently, no light source exists which is both narrow-band and speckle-free with sufficient brightness for full-field imaging applications. Light emitting diodes (LEDs) are excellent spatially incoherent sources, but are tens of nanometers broad. Lasers on the other hand can produce very narrow-band light, but suffer from high spatial coherence which leads to speckle patterns which distort the image. Here we propose the use of random Raman laser emission as a new kind of light source capable of providing short-pulsed narrow-band speckle-free illumination for imaging applications

Single and Composite Hot Subdwarf Stars in the Light of 2MASS Photometry

Utilizing the Two Micron All Sky Survey (2MASS) Second Incremental Data Release Catalog, we have retrieved near-IR magnitudes for several hundred hot subdwarfs (sdO and sdB stars) drawn from the "Catalogue of Spectroscopically Identified Hot Subdwarfs" (Kilkenny, Heber, & Drilling 1988, 1992). This sample size greatly exceeds that of previous studies of hot subdwarfs. Examining 2MASS photometry alone or in combination with visual photometry (Johnson BV or Stromgren uvby) available in the literature, we show that it is possible to identify hot subdwarf stars that exhibit atypically red IR colors that can be attributed to the presence of an unresolved late type companion. Utilizing this large sample, we attempt for the first time to define an approximately volume limited sample of hot subdwarfs. We discuss the considerations, biases, and difficulties in defining such a sample. We find that, of the hot subdwarfs in Kilkenny et al., about 40% in a magnitude limited sample have colors that are consistent with the presence of an unresolved late type companion. Binary stars are over-represented in a magnitude limited sample. In an approximately volume limited sample the fraction of composite-color binaries is about 30%.Comment: to appear in Sept 2003 AJ, 41 pages total, 12 figures, 2 tables are truncated (full tables to appear in electronic journal or available by request

Classification, Visualization, and Analysis of the Islamic State’s Narrative

The Islamic State (IS) declared the establishment of a Caliphate on June 29, 2014 in Mosul, Iraq. Since that declaration, IS has communicated a four-part narrative to the global community through Dabiq magazine, its e-publication. Each of the ten editions of Dabiq has provided insight into IS’s aspirations and reinforced its message of rejecting post-colonial structures. Critical to realizing its objective is establishing a foothold for the Caliphate through jihad (holy war), establishing legitimacy through jamaah (governance), achieving tawhid (unity), and expanding through hijrah (immigration). Each publication contains these narrative elements to document IS’s progress. Classifying, visualizing, and mapping will provide the analytical insight necessary to quantify the prioritization of IS narrative elements and identify the organization’s motivation