The effect of short time post-weld heat treatment on the fatigue crack growth of 2205 duplex stainless steel welds

The influence of γ content and its morphology on the impact and fatigue crack growth behavior of 2205 duplex stainless steel (DSS) welds were studied in this work. Short time post-heating was able to effectively raise the γ content and the impact toughness of the weld. The variation in microstructures showed less influence on the fatigue crack growth rate (FCGR) of the steel plate and weld except in the low ΔK regime. In contrast, residual welding stresses played a more significant affection on the FCGR of the DSS weld than microstructural factors did. Plastic deformation induced martensitic transformation within a definitely thin layer was responsible for the difference in crack growth behavior between specimens in the low ΔK range. Coarse columnar structure was more likely to have tortuous crack path in comparison with the steel plate.     

Efferent enhancement of a methylcholanthrene-induced sarcoma transplantable in strain 13 guinea pigs

The immunobiology of an antigenic methylcholanthrene-induced sarcoma (MC-D) of inbred strain 13 guinea pigs has been investigated. The induction of concomitant immunity by growing MC-D tumors was indicated by the suppression of small tumor inocula in the presence of a large tumor cell dose and by the regression of intradermal tumor nodules. Furthermore, it was demonstrated that this tumor was coated with antibody in vivo. Previous studies showed that MC-D tumors were infiltrated with killer T cells which were capable of complete tumor destruction in vitro, but could never induce spontaneous regression in vivo. On the basis of all these facts, antibody-mediated efferent enhancement is proposed to be the major escape mechanism of this tumor.     

Hydrogen-assisted fatigue crack growth of AISI 316L stainless steel weld

The fatigue crack growth behaviors of AISI 316L stainless steel (SS) welds in air and gaseous hydrogen were evaluated, and further compared with the base plate. In air, the fatigue crack growth rate (FCGR) of the weld after heat-treatment at 1050 ^oC/1 h was similar to that of the base metal. Furthermore, all specimens became susceptible to hydrogen-accelerated crack growth. Mainly quasi-cleavage fracture related with the strain-induced martensite accounted for the accelerated crack growth in hydrogen. A smaller amount of martensite in the weld was responsible for the decreased susceptibility to hydrogen-enhanced fatigue crack growth relative to the base metal.     

Structures and magnetic properties of Co and CoFe films prepared by magnetron sputtering

Structures and magnetic properties of Co and CoFe films on Si(100) have been investigated by employing scanning tunneling microscopy, atomic force microscopy, and magneto-optic Kerr effect techniques. As the film thickness increases, Co or CoFe clusters with different sizes are observed. As the film thickness increases below 20 nm, the size of the metal clusters decreases. For thicker films, the surface roughness increases monotonously by increasing the thickness. The easy axis of magnetization for both Co/Si(100) and CoFe/Si(100) prefers to be in the surface plane. By deposition of the Co or CoFe overlayers, the evolution of the longitudinal coercive force shows similar trend to the surface roughness. Minimum coercive force coincides with the smallest roughness of the film. For a film with greater roughness, the observation of larger coercive force could be explained by the impediment of the propagation of domain wall motion by defects of the films. At a higher deposition rate, Co islands in triangle shapes with an edge length around 100 nm are observed. This nanostructure shows an hcp-Co with the c axis parallel to the surface plane and is observed to be able to stabilize the coercive force for Co/Si(100) films.     

Laminar convection to rotating disks in non-Newtonian power-law fluids

A theoretical result has been obtained for heat transfer to a rotating disk in a non-Newtonian fluid which includes the convective transport in the radial direction. The transient heat transfer problem with step change in disk temperature is studied by instant-local similarity method and the approximate solution is very accurate for small time.     

Journal co-citation analysis of semiconductor literature

The purpose of this study is to map semiconductor literature using journal co-citation analysis. The journal sample was gathered from the INSPEC database from 1978 to 1997. In the co-citation analysis, the data compiled were counts of the number of times two journal titles were jointly cited in later publications. It is assumed that the more two journals are cited together, the closer the relationship between them. The journal set used was the 30 most productive journals in the field of semiconductors. Counts of co-citations to the set of semiconductor journals were retrieved from SciSearch database, accessed through Dialog. Cluster analysis and multi-dimensional scaling were employed to create two-dimensional maps of journal relationships in the cross-citation networks. The following results were obtained through this co-citation study: The 30 journals fall fairly clearly into three clusters. The major cluster of journals, containing 17 titles, is in the subject of physics. The second cluster, consisting of 9 journals, includes journals primarily on material science. The remaining cluster represents research areas in the discipline of electrical and electronic engineering. All co-cited journals share similar co-citation profiles, reflected in high positive Pearson correlation. Two hundred and ninety-six pairs (68%) correlate at greater than 0.70. This shows that there is strong relationship between semiconductor journals. Five individual journals in five paired sets with co-citation frequency over 100,000 times include Physical Review B, Condensed Matter; Physical Review Letters; Applied Physics Letters; Journal of Applied Physics; and Solid State Communications. This revised version was published online in August 2006 with corrections to the Cover Date.     

On the parallel-decomposability of geometric problems

There is a large and growing body of literature concerning the solutions of geometric problems on mesh-connected arrays of processors. Most of these algorithms are optimal (i.e., run in timeO(n ^1/d ) on ad-dimensionaln-processor array), and they all assume that the parallel machine is trying to solve a problem of sizen on ann-processor array. Here we investigate the situation where we have a mesh of sizep and we are interested in using it to solve a problem of sizen >p. The goal we seek is to achieve, when solving a problem of sizen >p, the same speed up as when solving a problem of sizep. We show that for many geometric problems, the same speedup can be achieved when solving a problem of sizen >p as when solving a problem of sizep.The research of M. J. Atallah was supported by the Office of Naval Research under Contracts N00014-84-K-0502 and N00014-86-K-0689, the Air Force Office of Scientific Research under Grant AFOSR-90-0107, the National Science Foundation under Grant DCR-8451393, and the National Library of Medicine under Grant R01-LM05118. Jyh-Jong Tsay's research was partially supported by the Office of Naval Research under Contract N00014-84-K-0502, the Air Force Office of Scientific Research under Grant AFOSR-90-0107, and the National Science Foundation under Grant DCR-8451393.     

ASSISTED CRACK GROWTH IN MARAGING STEEL WELDS BY GASEOUS HYDROGEN

Abstract— The effects of environmental hydrogen content on fatigue crack growth rates (FCGRs) in T-250 maraging steel plates and laser welds were investigated. The influence of ageing treatments on fatigue characteristics of the alloy was also studied. Experimental results revealed that the accelerated FCGRs in the presence of hydrogen were always associated with changes in fracture modes that appear in compact-tension specimens. Even for overaged specimens with excellent resistance to gaseous hydrogen embrittlement, such an acceleration of crack growth in hydrogen could not be avoided. The crack path of underaged specimens in hydrogen was found mainly along prior austenite boundaries for steel plates and along coarse columnar boundaries for welds. In gaseous hydrogen, peak-aged welds exhibited intergranular and quasi-cleavage mixed fracture modes, compared to mainly quasi-clevage for similar aged steel plates. Hence, the enhancement of crack growth in hydrogen was more pronounced for the welds. Overaged welds showed higher FCGRs than the same aged steel plates only in hydrogen and for Δ K values greater than 20MPa√m.     

Optimization of the hydrogen evolution activity on zinc-nickel deposits using experimental strategies

The experimental strategies including the fractional factorial design (FFD), path of the steepest ascent study, and the central composite design (CCD) coupled with the response surface methodology (RSM) was adopted to optimize the hydrogen evolution activity of Zn-Ni deposits. The key deposition variables, pH, the Zn/Ni ionic ratio and the TEPA concentration in the plating solutions, influencing the hydrogen evolution activity of Zn-Ni cathodes were found in the FFD investigation. These variables were subjected to the steepest ascent study to approach the vicinity of the optimal deposition conditions for plating the Zn-Ni deposits with the highest hydrogen evolution activity. In the CCD investigation, the optimal deposition settings, where the temperature of 50 °C, the current density of 2500 A m⁻², pH of 13.0, the Zn/Ni ionic ratio of 0.89 and the TEPA concentration of 0.58 M, were obtained by means of a regression model. This highest activity of the Zn-Ni deposits mainly consisting of the γ phase structure for hydrogen evolution is due to a combination of their good electrocatalytic activity and relatively high surface area. The electrocatalytic activity of these cathodes mainly composed of the γ phase Zn-Ni alloy was damaged by the selective dissolution of Zn from the deposits in 5 M KOH.