Properties of cryogenically worked metals

A program was conducted to determine whether the mechanical properties of cryogenically worked 17-7PH stainless steel are suitable for service from ambient to cryogenic temperatures. It was determined that the stress corrosion resistance of the cryo-worked material is quite adequate for structural service. The tensile properties and fracture toughness at room temperature were comparable to titanium alloy 6Al-4V. However, at cryogenic temperatures, the properties were not sufficient to recommend consideration for structural service

Crogenic alloy screening Interim report

Evaluation of mechanical properties and fracture strength of aluminum alloys and stainless stee

Determination of low-temperature fatigue properties of structural metal alloys Final report, Jul. 1964 - Aug. 1965

Fatigue testing and determination of low temperature properties of structural metal alloys - aluminum alloy, stainless steel, and nickel alloy

Experimental study of pop-in behavior of surface flaw-type cracks Final report

Growth behavior of surface-flaw type cracks in titanium alloy

Cryogenic alloy screening Final report

Mechanical properties of cryogenically stretched type 301 stainless steel and aluminum alloys 2021-T81 and X7007-T

Definition of mutually optimum NDI and proof test criteria for 2219 aluminum pressure vessels. Volume 3: Applications to rail defect evaluation

The technique for inspection of railroad rails containing transverse fissure defects was discussed. Both pulse-echo and pitch-catch inspection techniques were used. The pulse-echo technique results suggest that a multiple-scan approach using varying angles of inclination, three-surface scanning, and dual-direction traversing may offer promise of characterization of transverse defects. Because each scan is likely to produce a reflection indicating only a portion of the defect, summing of the individual reflections must be used to obtain a reasonably complete characterization of the defect. The ability of the collimated pitch-catch technique to detect relatively small amounts of flaw growth was shown. The method has a problem in characterizing the portions of the defect near the top surface or web intersection. The work performed was a preliminary evaluation of the prospects for automated mapping of rail flaws

Do Aphid Colonies Amplify their Emission of Alarm Pheromone?

When aphids are attacked by natural enemies, they emit alarm pheromone to alert conspecifics. For most aphids tested, (E)-β-farnesene (EBF) is the main, or only, constituent of the alarm pheromone. In response to alarm pheromone, alerted aphids drop off the plant, walk away, or attempt to elude predators. However, under natural conditions, EBF concentration might be low due to the low amounts emitted, to rapid air movement, or to oxidative degradation. To ensure that conspecifics are warned, aphids might conceivably amplify the alarm signal by emitting EBF in response to EBF emitted by other aphids. To examine whether such amplification occurs, we synthesized deuterated EBF (DEBF), which allowed us to differentiate between applied and aphid-derived chemical. Colonies of Acyrthosiphon pisum were treated with DEBF, and headspace volatiles were collected and analyzed for evidence of aphid-derived EBF. No aphid-derived EBF was detected, suggesting that amplification of the alarm signal does not occur. We discuss the disadvantages of alarm signal reinforcement

Thermal Diffusion and Quench Propagation in YBCO Pancake Coils Wound with ZnO-and Mylar Insulations

The thermal diffusion properties of several different kinds of YBCO insulations and the quench properties of pancake coils made using these insulations were studied. Insulations investigated include Nomex, Kapton, and Mylar, as well as insulations based on ZnO, Zn2GeO4, and ZnO-Cu. Initially, short stacks of YBCO conductors with interlayer insulation, epoxy, and a central heater strip were made and later measured for thermal conductivity in liquid nitrogen. Subsequently, three different pancake coils were made. The first two were smaller, each using one meter total of YBCO tape present as four turns around a G-10 former. One of these smaller coils used Mylar insulation co-wound with the YBCO tape, the other used YBCO tape onto which ZnO based insulation had been deposited. One larger coil was made which used 12 total meters of ZnO-insulated tape and had 45 turns. The results for all short sample and coil thermal conductivities were ~1-3 Wm-1K-1. Finally, quench propagation velocity measurements were performed on the coils (77 K, self field) by applying a DC current and then using a heater pulse to initiate a quench. Normal zone propagation velocity (NZP) values were obtained for the coils both in the radial direction and in the azimuthal direction. Radial NZP values (0.05-0.7 mm/s) were two orders of magnitude lower than axial values (~14-17 mm/s). Nevertheless, the quenches were generally seen to propagate radially within the coils, in the sense that any given layer in the coil is driven normal by the layer underneath it.Comment: 58 pages, 5 tables, 16 fig

Real-Time Analysis of Alarm Pheromone Emission by the Pea Aphid (Acyrthosiphon Pisum) Under Predation

Upon attack by predators or parasitoids, aphids emit volatile chemical alarm signals that warn other aphids of a potential risk of predation. Release rate of the major constituent of the alarm pheromone in pea aphids (Acyrthosiphon pisum), (E)-ß-farnesene (EBF), was measured for all nymphal and the adult stage as aphids were attacked individually by lacewing (Chrysoperla carnae) larvae. Volatilization of EBF from aphids under attack was quantified continuously for 60 min at 2-min intervals with a rapid gas chromatography technique (zNose™) to monitor headspace emissions. After an initial burst, EBF volatilization declined exponentially, and detectable amounts were still present after 30 min in most cases. Total emission of EBF averaged 16.33 ± 1.54 ng and ranged from 1.18 to 48.85 ng. Emission was higher in nymphs as compared to adults. No differences between pea aphid life stages were detected for their speed of alarm signal emission in response to lacewing larvae attack. This is the first time that alarm pheromone emission from single aphids has been reported