The equilibrium phase diagram for the CdTe-Ge system has been determined by means of differential thermal analysis, X-ray diffraction and microscopic examination. This system can be considered as a pseudobinary system from the result of X-ray experiment. There is no intermediate phase except CdTe and Ge phases in any composition. Mutual solid solubility of CdTe and Ge could not be detected by X-ray analysis. The monotectic temperature lies at 1342 K and the region of the liquid immissibility at this temperature is given as the composition of 6.5∼93 mol% Ge. The eutectic point lies at 97.5 mol% Ge and 1199 K.
The initial development of anti-plane strain yielding from a crack in an infinite elastic body was represented by a continuous distribution of screw dislocations on two planes inclined at angles ±βπ to the crack plane. The relevant stress function of the system was obtained in a closed form by the complex variable method. The slip line length and the crack tip opening displacement were obtained as functions of the applied stress and β. A comparison with the corresponding plane strain model gave similar results for βπ≈70°. The stress field near the crack tip was also discussed. When βπ<90°, the shearing stress acting ahead of the crack tip was bounded. In particular, for βπ≈70°, τyz was about 3τ0, where τ0 is the yield stress in shear, in agreement with the result from continuum plasticity.
Axial tensile yield behaviors of tungsten fiber-copper composites have been studied in terms of thermally induced residual stresses. The composites with 50 vol pct and 400μm diam tungsten wires were fabricated by a liquid infiltration technique followed by hot rolling. In the temperature range of 288K-673K, X-ray diffraction technique was employed to measure the matrix stress parallel to the fibers due to thermal expansion mismatch. Tensile tests were performed at room temperature by the use of the Instron Model 1122. Two series of specimens were prepared, which were as follows. 1) Annealed at 873K and slowly cooled to room temperature (designated as A). 2) Immersed in the boilling liquid nitrogen after the A treatment and slowly heated to room temperature (designated as N). The experimental results of the present study are summarized as follows: (1) The composites heated up to 673K indicated a fine X-ray diffraction profile. So it is possible by the X-ray analysis to measure the thermal stress at such a high temperature. (2) The copper matrix deformed elastically to accommodate thermal expansion mismatch when the temperature change was small. For the large temperature change, however, the matrix subsequently deformed plastically. Thus, the resulting thermal stress depends upon the thermal history of the composites. (3) The tensile yield behavior was significantly influenced by the thermal history of the composites. The A treated specimens indicated poor transition from stage I (both phases elastic) to stage II (fiber-elastic, matrix-plastic), while the N treated specimens indicated clear transition. These phenomena observed are well explained by the thermally induced residual elastic strains in the copper matrix obtained by the X-ray analysis.
An attempt was made to produce microduplex structures for Fe-Cr-Ni alloys with two different volume fractions of γ that is, 28%Cr-9%Ni and 32%Cr-8%Ni steels. The influences of grain size, ageing at 475°C and volume fraction of γ on their tensile properties and fracture were studied. The main results obtained are as follows; (1) A better combination of strength and ductility was obtained for 28%Cr-9%Ni steel (volume fraction of γ; 70%) than that for 32%Cr-8%Ni steel (volume fraction of γ; 30%). This results from the finer microstructures produced by the thermomechanical treatments in the former. (2) The relation between σ0.2 and d-1/2 showed Petch's type equation for the aged specimens with high volume fraction of γ and all unaged specimens. On the other hand, d-1/2 dependence of σ0.2 for the large grained specimens differed from that of the fine ones when the volume fraction of γ was low. This may be caused by the difference in the deformation mode within the α matrix that is, twin or slip deformations. (3) The influence of d on the ductility for the unaged specimens differed from that of the aged ones. The ductility decreased with the decrease in d in the former, whereas it increased in the latter.
Rotating bending fatigue tests in the high cycle region were performed on unnotched specimens of low-carbon steel. The initiation and the early propagation stage of micro-cracks were observed and the statistical property of crack depth distribution was investigated. (1) At the fracture surface of stage I cracks, parallel straight lines as the shear mode pattern were observed and the distribution of their initiated angle showed the maximum at the angle division of 40°∼50°. The average aspect ratio b/2a of stage I cracks was about 0.30 and this value was independent of the stress amplitude σa and the number of cycles N. (2) From the observation of the longitudinal section of specimens, the places of initiated region of micro-cracks were mostly in ferrite grains, and the ratio of cycles at the initiation was about 20%. The average depth of the initiation cracks (which included the stage I crack and the transient region) was 40∼50μm, being about equal to two grains. (3) The distribution of crack depth showed the composite Weibull distribution which was approximated to two straight lines separated by a separation parameter δ. Shape parameters m1 in the distribution (that of the shallower cracks under 40∼50μm) and m2 (that of the deeper ones) were about 0.5 and 1.0, respectively, and their values were independent of σa and N. The value of δ was about 50μm as similar to that of the initiation crack depth, and it increased with decreasing σa and with increasing average grain size.
Fatigue crack growth tests of low-carbon steels were conducted under various experimental conditions including elastic, elastic-plastic and general yielding. The crack growth rate under the general yield condition was correlated to several mechanical parameters proposed previously, and it found that the J integral range ΔJ was the best parameter among them in expressing the growth rate. As far as plastic deformation of the specimen is reversible, the relation between the rate da/ dN and ΔJ was expressed as a unique power function for various experimental conditions. When ratcheting deformation took place, the rate became higher than that predicted from the relation. The limitation of the applicability of ΔJ under load controlled conditions due to ratcheting deformation was predictable from the limit load analysis and its limitation due to specimen size was also clarified.
With a stochastic model based on damage accumulation, the author has investigated high cycle fatigue in which plastic deformation can be neglected. In elasto-plastic fatigue, plastic deformation must be considered and damage accumulation process cannot be assumed to be generated by a Poisson process because of frequent occurrence of damage accumulation. In this paper, the model was improved in these respects in oder that elasto-plastic fatigue phenomena can be treated. With this improved model, fatigue life up to crack initiation was calculated and the results were compared with experiments. Furthermore J(N) (fatigue J-integral) proposed in a previous paper was obtained with the use of this model and it was shown that the growth rate of small crack was proportional to J(N). With the above crack initiation model and the above propagation law of small fatigue crack, total fatigue life was evaluated.
Evaluation of the fatigue strength of weldments is important, particularly in nuclear components, but no proper evaluation method has been established because of several complicated factors including its geometric and metallographic discontinuities. In this paper, two fundamental evaluation methods of low cycle fatigue strength at elevated temperatures for weldments were proposed and were applied to the life prediction for SUS 316 stainless steel welded joints and 21/4Cr-1Mo steel welded joints. As a result, the life prediction was found possible within the factor of two on life for SUS 316 stainless steel welded joints. But in the case of 21/4Cr-1Mo steel welded joints, post weld heat treatment (PWHT) was found to affect the accuracy of life prediction. Life prediction was impossible within a factor of two on life for 21/4Cr-1Mo steel welded joints without PWHT. This may be caused by the difference in deformation resistance between base metal and weld metal. This study is being continued to establish a simplified fatigue design rule by modification of the presently proposed methods.
The SCC susceptibility of Type 316 stainless steel in 3% NaCl solution was studied by the potentiostatic CERT method in relation to the polarization behavior of the specimen. The effect of the crosshead speed on the tensile strength and the reduction of the sectional area was inspected with the crosshead speed over the range of 1.67×10-5m/s to 1.6×10-7m/s, and the fracture surface was observed by a scanning electron microscope. In 3% NaCl solution, Type 316 stainless steel was very susceptible to SCC at the pitting potential (0.39V vs. NHE), but immune to SCC at both the steady passive potential (-0.06V vs. NHE) and the unsteady one (0.19V vs. NHE). The mechanical properties such as the tensile strength and the reduction of sectional area of the specimen at the pitting potential decreased remarkably at the crosshead speeds below 1.67×10-6m/s, and this phenomenon was ascribable to the SCC caused from the pitting corrosion.
The strength of Japanese paper is known to be strongly dependent upon the structure of its constituent fibers. The present study has been conducted to evaluate theoretically the fracture strength of Japanese paper. The paper was postulated to be made with the three dimensional net structure of fibers. The fracture strength of the paper was discussed on the basis of investigations related to the crack propagation mode of paper. The crack growth rate of paper was measured experimentally. Its rupture speed was calculated from the cut rate of strips coated on the paper with an electro-conductive paint. The theoretical analyses showed that crack growth rate was dependent upon the cut direction of specimen sheet, the fiber geometry and its elastic modulus. This theoretical predictions were found to be consistent fairly with the experimental results.
Carbon black was mixed or co-grafted in solution with acrylic or methacrylic copolymers containing double bonds which were introduced by copolymerization of 2, 3-dimethy 1-1, 3-butadiene (DMB). Then, a variety of resistors with different degrees of crosslinking were made by coating the mixed pastes on porcelain plates and curing them with dicumyl peroxide for a given time at a given temperature. Their degree of crosslinking was estimated by the measurement of gel fraction, and its value for the most crosslinked resistor was more than 90%. For the resistors containing n-butyl acrylate (BA), acrylic acid, or DMB as a polymer component, the volume resistivities of the mixing type (the weight ratio of polymer/carbon black: 1/1) and the grafting type (the weight ratio of polymer/carbon black: 0.62-0.85/1) were in the range of 1.5-2.3Ω·cm and in the range of 2.8-3.9Ω·cm, respectively. Apparently, the volume resistivity of the mixed type was smaller than that of the grafting type. The resistance change with temperature was slightly positive for the samples except the highly crosslinked grafting type, and the reproducibility on the temperature cycle was improved with increasing crosslinking. On the other hand, the volume resistivity of the resistors containing lauryl methacrylate instead of BA was in the range of 3.8-5.4Ω·cm which was larger than that of BA type resistors. Especially, the mixing type resistors crosslinked with DCP showed a positive temperature coefficient against temperature cycle (40-140°C), and the resistance change at 140°C became more than 200%.
In order to investigate the influence of applied tensile stress within an elastic limit on the microhardness of an annealed structural rolled steel, hardness tests were made by changing two parameters, hardness test load and final polish. The results obtained were analyzed by means of the analysis of variance. The main results obtained were as follows: (1) Without applied tensile stress, the hardness measurement were possible for the conditions of 500gf·#120, 1000gf·#120, 500gf·#800 and 1000gf·#800. The dispersion of hardness number was minimum for the measuring condition of 1000gf·#800, and the hardness number varied depending upon the hardness test load and the final polish. (2) The hardness number was influenced by the tensile stress for the measuring conditions of 500gf·#120, 1000gf·#120, 500gf·#800 and 1000gf·#800. (3) A linaer relationship existed between the applied tensile stress and the hardness number for the above conditions. The regression coefficients were equal to each other, but the confidence interval decreased with increasing hardness test load and higher grade of final polish. (4) The measuring condition of 1000gf·#800 was best fitted for the case of applied tensile stress because the confidence interval became minimum among all of them.
The X-ray technique allows a nondestructive and rapid measurement of residual stresses in metallic materials. The centroid method has an advantage over other X-ray methods in that it can determine the angular position of a diffraction line, from which the stress is calculated, even with an asymmetrical line profile. An equation for the standard deviation of the angular position of a diffraction line, σp, caused by statistical fluctuation was derived, which is a fundamental source of scatter in X-ray stress measurements. This equation shows that an increase of X-ray counts by a factor of k results in a decrease of σp by a factor of 1/√k. It also shows that σp increases rapidly as the angular range used in calculating the centroid increases. It is therefore important to calculate the centroid using the narrow angular range between the two ends of the diffraction line where it starts to deviate from the straight background line. By using quenched structural steels JIS S35C and S45C, the residual stresses and their standard deviations were calculated by the centroid, parabola, Gaussian curve, and half-width methods, and the results were compared. The centroid of a diffraction line was affected greatly by the background line used. The standard deviation of the stress measured by the centroid method was found to be the largest among the four methods.