3,995 research outputs found
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 deep flaws in thin walled tanks
Growth of deep surface flaws in thin wall tanks of aluminum and titanium base metal
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
Screening properties of Gaussian electrolyte models, with application to dissipative particle dynamics
We investigate the screening properties of Gaussian charge models of
electrolyte solutions by analysing the asymptotic behaviour of the pair
distribution functions. We use a combination of Monte-Carlo simulations with
the hyper-netted chain integral equation closure, and the random phase
approximation, to establish the conditions under which a screening length is
well defined and the extent to which it matches the expected Debye length. For
practical applications, for example in dissipative particle dynamics, we are
able to summarise our results in succinct rules-of-thumb which can be used for
mesoscale modeling of electrolyte solutions. We thereby establish a solid
foundation for future work, such as the systematic incorporation of specific
ion effects.Comment: 9 pages, 9 figures, 1 table, RevTeX4-
Magneto-Transport in the Two-Dimensional Lorentz Gas
We consider the two-dimensional Lorentz gas with Poisson distributed hard
disk scatterers and a constant magnetic field perpendicular to the plane of
motion. The velocity autocorrelation is computed numerically over the full
range of densities and magnetic fields with particular attention to the
percolation threshold between hopping transport and pure edge currents. The
Ohmic and Hall conductance are compared with mode-coupling theory and a recent
generalized kinetic equation valid for low densities and small fields. We argue
that the long time tail as persists for non-zero magnetic field.Comment: 7 pages, 14 figures. Uses RevTeX and epsfig.sty. Submitted to
Physical Review
Conscious monitoring and control (reinvestment) in surgical performance under pressure.
Research on intraoperative stressors has focused on external factors without considering individual differences in the ability to cope with stress. One individual difference that is implicated in adverse effects of stress on performance is "reinvestment," the propensity for conscious monitoring and control of movements. The aim of this study was to examine the impact of reinvestment on laparoscopic performance under time pressure
Penis size: Survey of female perceptions of sexual satisfaction
BACKGROUND: Does the size of the male penis, in terms of length or width, make a difference in female sexual satisfaction? METHOD: To study the effect of penis width vs. length on female sexual satisfaction, 50 sexually active female undergraduate students were asked which felt better, i. e., was penis width or length more important for their sexual satisfaction. RESULTS: None reported they did not know, or that width and length were equally satisfying. A large majority, 45 of 50, reported width was more important (p < .001). CONCLUSION: Implications are discussed, including the fact that the data seem to contradict Masters and Johnson about penis size having no physiological effect on female sexual satisfaction
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