AN ASSESSMENT OF CRACK CLOSURE AND THE EXTENT OF THE SHORT CRACK REGIME IN Q1N (HY80) STEEL

Abstract— The paper addresses some aspects of the differences in fatigue crack growth rate behaviour and threshold values obtained for long through-cracks, short through-cracks and surface cracks. Attention is focused on plasticity induced closure in the wake behind the growing crack tip. For long cracks at high K _max, closure is found to depend in a linear manner on K _max, i.e. K _op, increases with the size of the monotonic plastic zone. Closure increases at low δ K and this is primarily a consequence of the load shedding procedure. If short through-cracks are prepared by machining specimens containing long cracks, a substantial part of the plastic wake is removed and this can produce marked effects on the closure contribution during subsequent growth. The length of crack "closed" in a long crack threshold test was found to be of the order of 1 mm. Cracks less than this length exhibited "short crack" behaviour: greater than this length, they behaved as "long cracks", with plastic wake effects apparently fully operative. Small surface cracks exhibit "long crack" behaviour at lengths as short as 0.2 mm and reasons for this are discussed.     

Integration framework for intelligent manufacturing processes

In this article, we describe a new approach to applying distributed artificial intelligence techniques to manufacturing processes. The construction of intelligent systems is one of the most important techniques among artificial intelligence research. Our goal is to develop an integrated intelligent system for real time manufacturing processes. An integrated intelligent system is a large knowledge integration environment that consists of several symbolic reasoning systems (expert systems) and numerical computation packages. These software programs are controlled by a meta-system which manages the selection, operation and communication of these programs. A meta-system can be implemented in different language environments and applied to many disciplines. This new architecture can serve as a universal configuration to develop high performance intelligent systems for many complicated industrial applications in real world domains.To whom all correspondence should be addressed.     

Effect of process distillation on mutagenicity and cell-transformation activity of solvent-refined,coal-derived liquids

Blended SRC-II process streams, representing a full boiling range distillate material, were fractionally distilled into non-overlapping 50 °F cuts with boiling points between 300 and 850 °F. Another set of 18 distillate cuts were obtained with boiling points ranging between 138 and 1055 °F. Distillate cuts were assayed for mutagenic activity using the histidine reversion assay with Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537, as well as for mammalian-cell transformation activity in the Syrian hamster embryo test, and DNA damage in the prophage induction assay. Samples were also separated into chemical class fractions by alumina column chromatography and analysed by high resolution gas chromatography so that the chemical composition of the cuts could be related to their relative activity in the different assays. In the mammalian cell transformation and microbial mutagenicity assays, significant activity was found almost exclusively in distillate cuts with components boiling > 700 °F, with the highest activity in the transformation assay observed for cuts > 800 °F. All of the distillate cuts showed increased levels of DNA damage as expressed by lambda prophage induction in Escherichia coli 8177. However, the greatest activity was associated with distillate cuts with boiling points in the 800 °F + range. Chemical analysis of the 50 °F distillate cuts showed a variety of polycyclic aromatic hydrocarbons (PAH) and amino-PAH compounds to be present in the distillate cuts boiling > 700 °F and essentially absent from cuts boiling < 700 °F. The sample set of non-overlapping (50 °F) cuts were reblended according to the proportions of each cut found in the original blend material. These reblended composites were then assayed to compare their activity with that predicted from the activities of the component distillate cuts. The reblending experiments indicated the microbial mutagenicity response was essentially additive. Mammalian cell transformation activities were non-additive, indicating a compositional effect on the expression of transforming agents in the complex mixture.     

Response to comments on upgrading of middle distillate fractions of a syncrude from Athabasca oil sands

In response to an interpretation made by Moore and Akgerman of data taken from a recent publication, previously unexplainable phenomena are accounted for, based on new experimental results. These relate to a thermodynamic equilibrium reaction involving saturation of aromatic hydrocarbons in synthetic crude middle distillates.     

Kinetics of hydantoin formation

The reaction of lignite in a slagging gasifier produces reactants which in turn form 5,5-dimethylhydantoin (DMH) as a major constituent in the condensate water. Variations in plant operating conditions made it impossible to accurately study the kinetics of formation of DMH in the actual gasifier water, and thus a model system was chosen. The reaction of acetone cyanohydrin in the presence of excess ammonium carbonate at concentrations approaching those obtained in the condensate water were studied at 50,70, and 90 °C. Secondorder kinetics were obeyed, and the pseudo second-order rate constants at the respective temperatures were 1.86, 3.6, and 4.62 dm³ mol^{? 1} h^{? 1}. Independent variation of the concentration of either acetone, cyanide, ammonia or carbonate gave results consistent with the interpretation that the formation of DMH is first order in all reactants: rate of formation of DMH = k[acetone][HCN][NH₃][CO₂]. The pseudo second-order rate constant is a complex rate constant including several rapid equilibria. A mechanism consistent with the kinetic data is presented.     

Effect of catalysts on the reaction between a cycloaliphatic diisocyanate (H-MDI) and n-butanol

Kinetics of the reaction between bis(4-isocyanatocyclohexyl)methane, H-MDI, and n-butanol was studied in toluene at 100°C. Effects of various catalysts, such as Hg(CH₃COO)₂, Zn(CH₃COO)₂ · 2H₂O, SnCl₄ · 5H₂O, and dibutyltindilaurate on the reaction rate and kinetics were also investigated. Reactions were followed by determining the unreacted isocyanate as a function of reaction time, using the standard dibutylamine back titration method. All catalysts seem to be very effective in increasing of the rate of the reaction compared to the uncatalyzed system. Depending on the initial stoichiometric ratio of (NCO) and (OH) and the concentration of the catalyst used, it seems possible to have preferential catalysis of the primary reaction between (NCO) and (OH) over the side reactions.     

A review of the methods of calculation of added resistance for ships in a seaway

Most recent studies of performance and assessment of auxillary wind powered ships have been based primarily upon the calm water resistance of the ships hull. This resistance is then used as a first estimate of the power required to drive the ship in a seaway. Some allowance has been made to this estimate for weather and seaway via a ‘weather margin’. For many years theoreticians have produced methods for the calculation of this weather margin of a ship in a random seaway due to the induced rigid body motions. This paper sets out to review the present day methods that are used to calculate ‘added resistance’ as it is often termed. This will allow, hopefully, designers and practitioners of wind powered vessels to discriminate between the different methods that are now available.     

Clinical psychologists reflect on the usefulness of various components of graduate training.

Graduates of clinical training programs were surveyed to determine the degree to which they have found various graduate school experiences useful in their professional work. Samples of academic clinical psychologists and practicing clinical psychologists reported time allocation and preference for various professional activities, perceived usefulness of various theoretical orientations, and the influence on their current professional work of 19 different graduate training topics. Results suggest that where differences exist, academic clinical psychologists are generally more satisfied with Boulder-model-inspired scientific training than are clinical practitioners. (PsycINFO Database Record (c) 2010 APA, all rights reserved)