Study of High-Performance Chloroprene Sponge in Diving Suit Application
A diving-suit-used foam neoprene with high performance has been developed and its aging behaviors in QUV accelerated aging tank and temperature cyclic chamber were investigated. The results show that the tensile strength and tear strength of the material are decreased after 9d QUV accelerated aging due to the obvious cracks in the foaming cell. In temperature cycling the mechanical properties increased arising from cross linking reaction in the aging process. Besides, the chloride ion penetration resistance of the material was tested by dielectric flux intelligent tester, and the result shows that the material is of excellent chloride ion penetration resistance capability. The infiltration coefficient is 8.1×10-11cm2/s.
Changes of core temperature of diver in low temperature water
Object:To study the changes of core temperature when a diver didn't wear the cold- proofing and heating clothing in the low temperature water.Methods:The subject in dry diving suit dived in the water of the average 13.6℃temperature.His core body temperature was observed on the real time and recorded once every 5 min.Results:The total diving time was 155 min and the core temperature dropped from 37.25℃to 35.80℃.The temperature curve rose slowly in the initial stage and then dropped quick- ly.The phenomenon of afterdrop also could be observed in this study.Conculsion:Under the condition of no cold-proofing and heating,a diver can dive only for a short time.The study of medical protection for divers exposed in the low temperature surroundings for a long time should be strengthened.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME