Modified manjoine WOL specimen for JIc and δi tests

A procedure is presented by which a modified WOL specimen can be designed to withstand the load required to achieve a $\text{δ}{}_{\mathrm{i}}$, or $\text{J}{}_{\mathrm{Ic}}$ test for a low yield strength, high toughness material, using information from the test of a standard WOL specimen that has suffered plastic collapse of its loading arms. The $\text{K-}\text{calibration}$ for the family of geometries used is obtained from published data fitted to a 2-dimensional half-power series, and the load point and guage point compliances are obtained through a connected beam model that is calibrated from existing compliance data to imitate a WOL specimen. Prom these calibrations the $\text{J-}\text{integral}$ tensile component correction factor is evaluated and found to be applicable for this type of specimen.     

A new method of determining JIc of steel by means of single specimen

A new method of determining $\text{J}{}_{\mathrm{Ic}}$ of medium to high strength steel by means of single TPB (three points bend) specimen is proposed and tested. Several kinds of steels with yield strength between 53 and 115 kg/mm² are tested. The calculations of each data set of a single specimen are carried out by computer. The results of single specimen method are in good agreement with those obtained by multi-specimen method.     

The prediction of KIc from tensile data

A theory of fracture toughness is developed which is based on the Dugdale crack model. Work hardening is considered. By using the stress-strain curves as input data, $\text{K}{}_{\mathrm{Ic}}$ values are predicted for a wide range of materials including uranium alloys, beryllium, aluminum, a nickel-cobalt alloy, and a titanium alloy. The calculated values agree exceptionally well with the experimental values. Plastic-zone size (including a qualitative estimate of shape) and stress and strain in the plastic zone are also predicted.     

Experimental determination of Jc data using different types of specimen

$\text{J}{}_{\mathrm{c}}$ values for two medium-strength steels have been experimentally determined from tests on different types of specimen. Evaluation of test records was performed utilizing a digital computer. Two independent electrical methods were employed to determine critical points. Results indicate independence of $\text{J}{}_{\mathrm{c}}$ on specimen configuration and hence support the suggestion that the $\text{J-}\text{integral}$ be a relevant parameter for onset of crack growth. Present results compare favourably with previously published data.     

Fatigue crack growth below Kiscc

The theory of fatigue crack growth in agressive environments is briefly described. The theoretical results are compared with the test data.     

Fracture of round bars loaded in mode III and a procedure for KIIIc determination

The available literature reports few studies on Mode $\text{III}$ fracture. In fact, even though the Mode $\text{III}$ fracture toughness, $\text{K}{}_{\mathrm{IIIc}}$ is an important factor in design and analysis of fractures under torsional loading, the procedure for the measurement of $\text{K}{}_{\mathrm{III}}$ is yet to be standardized.In this paper, the results of a simple analysis, which determines the displacement produced by the size dependent plasticity and the growth of crack in a circumferentially cracked round bar subjected to Mode $\text{III}$ loading, are presented. It is shown that plastic zone size decreases as bar diameter increases. This implies that whereas a small diameter bar can fail in a ductile manner, a large diameter bar may undergo a predominantly linear, elastic and brittle fracture even though the material is ductile.The analytical results are verified by experimental measurements on circumferentially cracked specimens loaded in Mode $\text{III}$. Based on this, one can determine the limiting value of the bar diameter, which must be tested to obtain a $\text{K}{}_{\mathrm{IIIc}}$ in a predominantly linear elastic condition. Further, a new and simple procedure for the determination of $\text{K}{}_{\mathrm{IIIc}}$ is proposed. This procedure enables one to determine the stress intensity factor at which a crack starts extension in the specimen under Mode $\text{III}$ loading.     

G̃c and R-curve fracture toughness values for aluminum alloys under plane stress conditions

The effect of specimen geometry and subcritical crack growth on the nonlinear energy fracture toughness, $\text{G}\text{?}{}_{\mathrm{c}}$, has been examined for thin, center-cracked sheets of 2024-T3 and 7075-T6 aluminum alloys. The procedure followed was to independently vary the specimen length, L, width, w, andd crack length-to-specimen width ratio and to determine the toughness both at the onset of subcritical crack growth and at the initiation of unstable fracture. Comparisons were also made with the R-curve toughness, G_R, evaluated at unstable fracture from which it was found that both $\text{G}\text{?}{}_{\mathrm{c}}$ and G_R displayed the same trend of change with geometrical variables, with $\text{G}\text{?}{}_{\mathrm{c}}$ consistently higher than G_R. When the nonlinear energy fracture toughness was evaluated at the onset of subcritical crack growth, it was found that the geometry dependence essentially disappeared.Scanning electron microscopic examination of some typical fracture surfaces showed that stable crack growth was accompanied by a gradual change of fracture mode from plane strain to plane stress. An analysis of possible errors in the experimental procedure showed that the scatter observed in $\text{G}\text{?}{}_{\mathrm{c}}$ values was not due to experimental errors, but apparently due to inhomogeneities in the materials. Several techniques were also introduced for the purpose of more directly incorporating crack growth into the $\text{G}\text{?}{}_{\mathrm{c}}$ determination, but it was found that they did not cause significant variation in the toughness values.     

Interface characteristics of GaAsAlxGa1−x As superlattices grown by MOCVD

The structure and quality of the heterointerfaces of $\text{AlAs}\text{GaAs}$ semiconductor superlattices grown by the MOCVD technique have been examined on the atomic scale using high-resolution electron microscopy lattice imaging. The interface of either GaAs grown on AlAs (Al_xGa_1?xAs) or AlAs (Al_xGa_1?xAs) grown on GaAs is atomically smooth and without defects in both cases, and the interface quality is not degraded by increasing either the layer size or the Al composition.     

On the computation of mixed-mode K-factors for a dynamically propagating crack,using path-independent integrals J'k

The path-independent integral $\text{J'}{}_{\mathrm{k}}$, which has the meaning of energy release rate in elastodynamic crack-propagation, is used to numerically obtain the mixed-mode dynamic stressintensity factors for a crack propagating in a prescribed direction with a prescribed velocity. Moving isoparametric (non-singular) elements are used to model crack propagation. Even though J' is a vector integral and hence is coordinate invariant, the desirability of using specific coordinate systems to improve the accuracies of the numerical solutions for $\text{K-}\text{factors}$ is pointed out. Two procedures for extracting the mixed-mode $\text{K-}\text{factors}$ from the J' integral for a propagating crack are given. It is found that the component of J' along the crack-axis, i.e. $\text{J'}{}_1{}^0$, is always equal to or greater than the product of a crack-velocity-function and the component normal to the crack-axis, $\text{J'}{}_2{}^0$. Several examples of a slanted crack are presented to demonstrate the practical utility of the J' integral. A discussion is also presented concerning the velocity factors for dynamic $\text{K-}\text{factors}$, and energy release rate, in a finite body.     

On the constitutive relations for anisotropic materials—The crystal class D6h

We consider constitutive relations of the form W(B,…, C) where W is a scalar-valued polynomial function which is invariant under the group $\text{{D}{}_{\mathrm{6h}}\text{}}$ which defines the symmetry of the crystal class $\text{D}{}_{\mathrm{6h}}$. We make no restriction as to the number or kind of quantities appearing as arguments of $\text{W}$. We list the multilinear elements of an integrity basis for functions of quantities φ, φ',…, x, y,… where φ, φ',…, x,y,… form carrier spaces for the irreducible representations Γ₁,…, Γ'₆ of $\text{{D}{}_{\mathrm{6h}}\text{}}$. The elements of an integrity basis for functions of B,…, C are readily determined once these multilinear elements are given. We give examples and tables to facilitate the use of the results obtained here and in [1].     

A single test method for evaluation of the J integral as a fracture parameter

A semi-analytical method for the evaluation of the Rice fracture parameter $\text{J}$ is presented. The method is such that a value of $\text{J}$ may be determined from a single load-displacement test record, and procedures are set out, together with appropriate equations, for evaluating center cracked sheets, compact tension specimens and single edge notched beams. The method utilizes the elastic stress intensity relationships in conjunction with a modified form of the Irwin plastic zone size correction factor. Tests were carried out on center cracked sheets and compact tension specimens manufactured from a high strength aluminium alloy of a thickness (3.2 mm) for which conditions of plane stress prevailed. The $\text{J}$ values are shown to be dependent on specimen dimensions. The results are compared with those obtained by a graphical procedure. Some anomalies are noted and comparison of center cracked sheets with compact tension specimens discussed.     

Crystal growth and characterization of In23PSe3

Crystals of $\text{In}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{PSe}{}_3$ were grown by chemical vapor transport of the elements. The phase is structurally related to the hyposelenophosphates, M^IIPSe₃, but contains both indium atoms and vacancies on the metal ion sites. The compound shows a high electrical resistivity (>10⁸ ohm-cm) and has an optical absorption edge at 1.9 (1) e.V.     

Thermoelectric power and annealing effects in NbAl2O3 cermet-type films

The effects of annealing on the structure and electrical conduction in $\text{Nb}\text{Al}{}_2\text{O}{}_3$ semiconducting films were investigated. Annealing increases the product of the density of states and the mobility near the Fermi level, and this suggests that the mobility increases because of structural changes in the alumina matrix.Thermopower measurements allowed us to evaluate the asymmetry about the Fermi level of the product Nμ.     

Crystal growth and characterization of In23PS3

Crystals of $\text{In}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{PS}{}_3$ were grown by chemical vapor transport of the elements from a charge zone maintained at 630°C. and a growth zone at 560°C. The crystals were characterized by chemical, x-ray, and densitometric techniques. $\text{In}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{PS}{}_3$ is structurally related to the M^IIPS₃ thiophosphides. The compound is an insulator and has an optical absorption edge of 3.1(1) e.V.     

X-ray study of the deficient perovskite La23TiO3

The A-site deficient perovskite $\text{La}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{TiO}{}_3$ was synthesized under the controlled atmosphere of CO₂H₂ mixed gas at 1350°C, and the structure was investigated by the powder X-ray diffraction method. The product is slightly oxygen deficient ($\text{La}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{TiO}{}_{\mathrm{3?\lambda }}$, where 0.007 ≦ λ ≦ 0.079), and the structure is dependent on λ: when λ is small, the perovskite cell is distorted to orthorhombic symmetry and the unit cell is doubled along the c′ (> b′, a′) axis, while a cubic perovskite structure is facilitated with the increase of λ. A structural model, which calls for an ordered arrangement of the A-site vacancies along the c′-axis, is proposed and its order parameter is calculated from the intensities of the superstructure lines.     

Photoelectrochemical study of the layered compound In23Pse3

The layered compound $\text{In}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{PSe}{}_3$ is studied by photoelectrochemical technique. Two modes of transition, indirect ～ 1.55 eV, and direct ～ 1.80 eV are evidenced. An estimation of the hole diffusion length is given through the use of Gärtner model ($\text{L}\text{? 4 μ}\text{m}$). The flat band positions of the junction $\text{In}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{PSe}{}_3\text{-}\text{electrolyte}$ at different pH values are determined in an electrochemical scale.     

121Sb nuclear magnetic resonance of a GraphiteSbCl5 intercalation compound

Graphite will react at room temperature with SbCl₅ to form a second stage, orthorhombic, intercalation compound of lattice parameters a₀ = 849 pm, b₀ = 738 pm, and c₀ = 1272 pm. ¹²¹Sb nuclear magnetic resonance (15 MHz, 23°C) in the dispersive mode reveals a signal of width 7100 Hz located at 384 ppm downfield from SbCl^?₆. Electron spin resonance (9.5 GHz, 23°C) shows an asymmetric, $\text{ca}$. 95 G wide line of Dysonian center at g = (2.0024±0.0014). These results are consistent with oxidative intercalation of graphite by SbCl₅ to form a compound containing both SbCl^?₆ and SbCl₅. Our findings are compared to work on the analogous intercalate C₁₀AsF₅ and on the “overoxidized” material formed by reaction of graphite with WF₆ and F₂.     

The discharge of a I12TaSe4 cathode for lithium battery

The discharge process was investigated on a lithium battery using $\text{I}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{TaSe}{}_4$ as cathode. The battery works as primary battery. The potential gradually decreased from 2.1V to 1.8V upto a discharging of $\text{Li}\text{I}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{TaSe}{}_4\text{≈0.5}$. Then it was almost constant at 1.8V until the discharging of about 2.0. Iodine is partially removed out of $\text{I}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{TaSe}{}_4$, keeping the host TaSe₄ chain structure as it was in the first step of discharge. The new product has tetragonal crystal lattice having lattice parameters of $\text{a}\text{=9.532}\text{A}\text{?}$ and $\text{c}\text{=25.31}\text{A}\text{?}$, which is twice of c-parameter of $\text{I}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{TaSe}{}_4$.     

Magnetic,electrical and thermal studies on the V1−xMox02

The monoclinic-to-tetragonal structure transition of oxides V_1?xMo_x0₂ with $\text{0≤}\text{x}\text{≤0.20}$ has been studied by means of DTA, X-ray diffraction, magnetic susceptibility (powder samples) and electrical conductivity (single crystals) measurements within the temperature region 80 K to 400 K. A linear decrease of the transition temperature of 11 K per atom % Mo was observed. The magnetic susceptibility of the low temperature phase was found to be temperature independent paramagnetic for all preparations. Electrical conductivity measurements on the same phase showed crystals with $\text{x}\text{? 0.04}$ to be semiconducting, while a metallic behavior was observed in the region $\text{0.10 ?}\text{x}\text{? 0.14}$.