Study on the effect of the crack length on the JIC value

The ductile fracture tests are carried out using compact type (CT) specimen, three point bend specimen and center cracked tension (CCT) specimens made of A533B steel and aluminum alloy with different crack lengths. The effect of the crack tip constraint on the microscopic fracture behavior is studied by the scanning electron microscope (SEM). It is shown that the apparent J_IC value increases due to the decrease of the crack tip constraint. It is pointed out that the increase of the apparent J_IC value is partly due to the error of the conventional equation to estimate the J value. Based on the FEM analyses, these apparent J_IC values are corrected and are compared with the valid J_IC values. The good co-relation between apparent J_IC value and the Q factor, proposed by O'Dowd and Shih, is shown for all the specimens. The FEM analyses based on the Gurson's constitutive equation is also carried out. The effect of the constraint on the crack tip field is discussed.     

Tri-phasic zirconia electrolyte for the in-situ determinations of silicon activities in hot metal

Tri-phasic zirconia electrolyte, which consists of cubic ZrO₂–MgO solid solution, monoclinic ZrO₂ and 2MgO · SiO₂, was applied to solid state electrochemical sensor for rapid determinations of silicon activities in hot metal. The performance of the cell: Mo + MoO₂ / tri-phasic zirconia electrolyte / Fe + Si + C was tested with molten iron at 1723 K. The cell potentials showed good sensitivity to the variation of silicon content in the melt.     

A microsomal membrane component associated with iron reduction in NADPH-supported lipid peroxidation

This study was conducted to determine whether a factor responsible for reduced nicotinamide adenine dinucleotide phosphate (NADPH)-supported lipid peroxidation in rat liver microsomes is involved in iron reduction by cooperation with NADPH-cytochrome P450 reductase. Under anaerobic conditions, NADPH-dependent reduction of ferric pyrophosphate in microsomes was not dependent on cytochrome P450 levels and was not inhibited by carbon monoxide (CO). All of the iron complexes with chelators such as adenosine 5′-diphosphate, pyrophosphate, nitrilotriacetate, oxalate or citrate were reduced in microsomes, although in the reconstituted system containing purified NADPH-cytochrome P450 reductase little or no iron reduction was found. A cytochrome P450-free fraction from a cholate-solubilized preparation of microsomes after passage through a laurate sepharose column was required for reduction of iron pyrophosphate in the reconstituted system leading to lipid peroxidation. The iron reduction was not inhibited by CO and was destroyed by heat treatment or trypsin digestion of the fraction. All iron complexes were reduced in the presence of the fraction, using a reducing equivalent of NADPHvia NADPH-cytochrome P450 reductase. The results indicate that a heat-labile component, which is probably a protein distinct from cytochrome P450, is associated with iron reduction responsible for lipid peroxidation in microsomes.     

Ductile crack growth behavior of welded plate

Crack growth behaviour in welded plate is studied from the viewpoint of the constraint effect. Three cases are studied. One is the crack growth perpendicular to the weld line. By the generation phase analyses, the effect of the weld line on the crack tip fields is studied. In the second case, the crack transversing the weld line grows perpendicular to it in a compact tension (CT) specimen, and in the third case, the surface crack growth problem is studied. In the second and the third cases, the three dimensional numerical analyses are conducted and the crack tip fields are studied. It is shown that the Q factor proposed by O'Dowd and Shih has large effect on crack growth behavior in the weld plate, especially on the local behavior near the weld line.Presented at the Far East Fracture Group (FEFG) International Symposium on Fracture and Strength of Solids, 4–7 July 1994 in Xi'an, China.     

The transfer of silicon from the gas phase to molten iron in the blast furnace

The mechanism of silicon transfer in a blast furnace has been studied. It is concluded that the contribution of slag-metal reaction to silicon increase in the metal will not be very important because of the slow rate of the reaction and high oxygen potential of slag in a blast furnace. By making use of kinetic and thermodynamic data, it is shown that the reaction of SiO containing gas with liquid iron of high carbon content takes an important role in the silicon transfer in a blast furnace.     

Continuous Processing of Monodispersed Titania Powders

A new continuous precipitation process for monodispersed ceramic powders using a static mixer was developed. Monodispersed TiO₂ powders were prepared continuously with high reproducibility and reliability by controlled hydrolysis of titanium ethoxide. Important steps were uniform and rapid mixing and aging using hydroxypropylcellulose as a dispersant. The concentrations of titanium ethoxide and water suitable to production of monodispersed TiO₂ powders lay within a limited range. A minimum aging period of 10 min was required to obtain monodispersed powders.     

Analysis of 7 Models for the 2-Dissimilar-Unit, Warm Standby, Redundant System

The paper is in 2 parts. In all models the failure rates are constant, but repair rates need not be constant. The method of supplementary variables is used for solving the models. Part I considers the effect of priorities on reliability and availability for 4 basic models; 1) priority in both repair and operation; 2) priority in repair; 3) priority in operation; 4) no priority. Models 1 and 2 treat 2 repair disciplines: a) preemptive-repeat, b) preemptive-resume. We obtain 1) Laplace transforms of availability and reliability and 2) explicit expressions for steady state availability and for mean time to system failure. The effect of priority assignment to maximize steady state availability is discussed. Part II considers the effect of having different repair rates, depending on whether the failure was from standby or from operation. We obtain 1) Laplace transforms of availability and reliability and 2) explicit expressions for mean time to system failure.     

Impact ionisation ratio in In0.73Ga0.27As0.57P0.43

A window structure InGaAsP avalanche photodiode (a.p.d.) has been fabricated by using liquid-phase epitaxy on (111B) InP. Multiplication characteristics show that the impact ionisation rate for electrons is larger than that for holes (?>?). The ionisation ratio ?/? was estimated to be 3?4. A low-noise a.p.d. will be realised by a structure with electron-initiated multiplication.