Hydroxyapatite separated from fish scales by treating them with hot potassium hydroxide solution (n-HAp) were applied to the removal of Pb2+ and Cd2+ ions in aqueous solutions at several temperatures. The removal ratios of the ions in aqueous solutions were as well as those of synthetic hydroxyapatite. Hydroxyapatite powder separated from fish scales can be supplied at low price and of practical use for removal of such toxic heavy metal ions as Pb2+ and Cd2+ in industrial waste.
Elliptical ring subjected to arbitrary load has not been studied until now, although the solution for circular ring is easy to obtain. The analysis of elliptical ring enclosed by conforcal two elliptical boundaries is much complicated. In this paper, the general solutions of isotropic elliptical ring for stresses and displacements are obtained by the method of Laurent series expansion of complex stress functions and some numerical examples are shown. The accuracy and the rate of convergence of the present method are then discussed based on these solutions.
A rod type and a cylinder-rod type load supports are developed for superconducting magnets of magnetic levitation vehicles. The load supports act as thermal insulators and, at the same time, are required to sustain vibrating loads. The supports are made of Al2O3FRP and have joints contacting with metal sleeve. The material of rod is unidirectional Al2O3FRP, while that of cylinder is satin woven laminating Al2O3FRP. The results obtained in this study on the mechanical behavior of the load supports are as follows: (1) The unidirectional Al2O3FRP rod and the metal sleeve can be tightly joined by pulling them to the opposite directions, each of which has a matching taper face with solid lubricant before assembling. (2) The impregnation resin of Al2O3FRP should have a high glass transition temperature, i.e. 453K, for reverting a decrease in joint force due to stress relaxation of the resin at room temperature. By giving a sufficiently large circumferencial elastic strain to both the rod and the sleeve than the cooling thermal strain of Al2O3FRP, high joint force remains even at a cryogenic temperature and the joint can sustain high vibrating loads. (3) The replenishment resin, which forms a wedge shape at both ends of cylinder in the wedge shape groove of the metal sleeve, should have the glass transition temperature of 398K, so as to prevent the joint from stress relaxation at room temperature. By curing the replenishment resin in the cylinder-rod type load support, the stress relaxation in the rod is kept as low as 10% because of high enough glass transition temperature of rod resin.
Sheet Molding Compound (SMC) products such as one piece panel, have always stiffening ribs. In this product, some defects are observed. They are sink mark, weld lines, warpage and heat cracks. These defects are greatly influenced by the molding condition of SMC, especially material flow. In the design of the mold, the material flow is an important factor. But the material flow of SMC is complex and unsteady. So, CAD system of SMC is needed to design a molding die. Therefore, the present authors are constructing the data base to design the compression molding process of SMC. In this paper, the flow characteristics and forming defects of SMC products were investigated. In flow characteristics, attention was paid to the branch of material flow around the rib part. To obtain the relation between flow characteristics and defects, the molding processes for T-shaped products were carried out by varying the charge pattern and the shape of the rib. Then the warpage was measured and the heat crack was observed. On the other hand, the data of fibre orientation was taken in the cross section of molding products. Moreover, to construct CAD system of SMC, the thermal shrinkage in cooling down after the process was calculated by using the deformation model for the numerical analysis where SMC has the anisotropic homogeneity.
The effects of structural anisotropy on the deformation properties of granite under cyclic loading have not been clarified. In this paper, four types of granite specimens are prepared with an angle θ of the structural anisotropic plane to the loading axis of 0°, 30°, 60° and 90° respectively; and cyclic loading tests are performed under uniaxial compression. The stress amplitude levels used in this experiment are 0-30%, 20-50% and 40-70% of the uniaxial compressive strength of this granite. As the results, for the stress amplitude level of 0-30%, the elastic modulus under the cyclic loading is approximately constant. However, it is recognized that the increase of axial strain during the cyclic loading is largest for the specimen with θ of 30°, and its value under ten thousands cyclic numbers corresponds to 1.27 times as much as the axial strain given by 20% stress for the uniaxial compressive strength, and that its uniaxial compressive strength after cyclic loading is lowest for the all stress amplitude conditions. Further more, it is clarified that its volumetric strain indicates only a negative value under 50% and 70% stress levels under cyclic loading.
The present paper firstly deals with the analysis of the displacement of viscoelastic material confined in a cylindrical mold under repeated load whose frequency is far less than the natural frequency of the test body, with an assumption of no friction between the test body and the mold, by means of finite Fourier-Hankel transform. Distortional deformation is modeled by a Voigt model and volumetric deformation is modeled by an elastic or Voigt model. In so doing, two viscoelastic models are formulated. As for the test, the surface displacement was measured for dried standard sand, sandy soil, cohesive soil and undisturbed Kanto loam. Then viscoelastic properties of the test materials confined in the mold are evaluated by means of nonlinear least squares method. In the case of applying Voigt model to both distortional and volumetric deformations, the analytical results agree well with the experimental ones.
Corrosion behavior of Fe-Si alloys was examined in boiling environments of 95wt% and 50wt% sulfuric acid. The critical content of Si for the passivation was found to lie in the range of 9-10wt% Si and 12-15wt% Si in 95wt% and 50wt% sulfuric acid, respectively. The oxide film formed on the surface of the passivated alloys was examined by X-ray diffraction method and scanning Auger microscopy. The passivation film was composed of amorphous oxide with Si/O atomic ratio of about 0.5. The film contained a trace amount of sulfur when formed in oxidative 95wt% sulfuric acid, whereas it did not when formed in reducing 50wt% sulfuric acid. The film growth rate depended largely on the alloy composition and on the concentration of sulfuric acid as well.
Hydrogen embrittlement and intergranular corrosion of sensitized SUS316 steel and Inconel 600 were studied. Intergranular corrosion susceptibility with the strauss test for SUS316 steel increased with sensitized time and reached a maximum at 973K, 86.4ks, then decreased. Intergranular corrosion susceptibility in boiling 40% HNO3 test for Inconel 600 increased with sensitized time and reached a maximum at 973K, 8.64ks, then decreased. Hydrogen embrittlement susceptibility with the tensile test under catholic charging on SUS316 steel increased with formation of Cr depleted zones. On the other hand, hydrogen embrittlement susceptibility with the tensile test under cathodic charging on Inconel 600 increased with formation of Cr carbides.
Fatigue tests were conducted on the free cutting stainless steel SUS303/SUS303 friction welded joints under pulsating zero-tension load to study the effect of microstructure produced by friction welding process. The specimens with circumferential notch which was machined near the welding interface were used in the fatigue tests. Fatigue crack initiation and propagation were examined by using DC potential drop method. The fatigue limit of the friction welded joints was almost the same as that of the base metal. But the difference in fatigue strength between the base metal and the joints increased with increasing stress level. The crack initiation strength of the joints was lower than that of the base metal and the non-propagating cracks were found in the specimens of the joints which did not fracture above 107 stress cycles. The fatigue crack growth rate of the joints decreased and reached the minimum value near crack length of 0.2mm. The crack growth rate of the joints was smaller than that of the base metal in the low stress intensity factor range, while it increased and gained upon that of the base metal. The degradation of fatigue strength of the joints, especially for the fatigue crack initiation strength, was mainly caused by the shape, size, direction and distribution of non-metallic inclusions which differed from those of the base metal.
High velocity oxygen-fuel (HVOF) system in air has been established for producing the coatings that are extremely clean and dense. It is thought that the HVOF sprayed MCrAlY (M is Ni, Co or Fe) coatings can be applied to prevent oxidation and corrosion in the hot section of gas turbines. Also, it is well known that thicker coatings can be sprayed for improving the residual stress in comparison with any other thermal spraying system. However, the thermal and mechanical properties of HVOF coatings have not always been clarified. In this paper, the thermal and mechanical properties of MCrAlY coatings were measured in both cases of as sprayed and heat treated coatings. From the results, it is confirmed that the thermal and mechanical properties of HVOF MCrAlY coatings could be improved by a diffusion heat treatment up to the level of vacuum plasma sprayed MCrAlY coatings. On the other hand, the experimental results suggest that the residual stress of HVOF coatings is decreased by the shot-peening effect in comparison with the vacuum plasma sprayed coatings.
In the high frequency electrodes composed of a metal substrate and a dielectric coating layer, it is important to develope a thicker glass coating technique for producing a dielectric coating layer for electric discharge parts. In this study, a borosilicate glass coating and a 18Cr stainless steel substrate were selected for the experiments to develope the muti-layered thick glass coating technique. The mechanical properties, such as Young's modulus, Poisson's ratio and cracking strain, of the coating with various glass thickness were measured at room temperature using a newly developed strain gage method. The experimental results suggested that the cracking strength decreased with increasing glass coating thickness due to an increase in residual stress at the glass coating surface.
In order to investigate the effect of notch on the fatigue strength of carbon steel coated with TiN thin hard film, cantilever-type rotating-bending fatigue tests were carried out in air and in 3% saline solution by using U-shaped notch round-bar specimens of 0.35% carbon steel coated with TiN by physical vapor deposition (PVD) method. From the experimental results of the fatigue tests in air, an increase in fatigue strength was observed for the TiN-coating specimens, as compared with those without coating. Improvement in fatigue strength depends on the stress concentration factor, and the maximum improvement of 50% was observed on the sharp notched specimen. The endurance limit was defined as the crack initiation limit for the notched specimen with coating, while it was defined as crack growth limit for the notched specimen without coating. It was clear from an elasto-plastic analysis by FEM and the experimental results that a strain at the notch root for crack initiation limit was increased by the existence of hard thin film. From the corrosion fatigue test results, TiN-coating film effectively protects the substrate from the corrosive environment, and then the improvement of corrosion fatigue strength was about 87% for the dull notched specimen, which was the same as that in the smooth specimen.
In order to investigate the effect of load variation on the cyclic fatigue crack growth behavior of gas-pressure-sintered silicon nitride, fatigue crack growth tests under constant amplitude loading, multiple peak overloading, Lo-Hi and Hi-Lo two-step loadings were carried out using compact type (CT) specimens. Crack length and macroscopic crack closure were measured using the unloading elastic compliance method. Grain interlocking was observed around crack wake in all fatigue test specimens by SEM. Fatigue crack growth rate, da/dn, under constant amplitude loading was controlled by not only maximum stress intensity factor, Kmax, but also load amplitude. Crack opening stress intensity factor, Kop, decreased as load amplitude increased, as was concerned with breaking of grain interlocking. Overload caused the acceleration of fatigue crack growth rate, which was in contrast to the retardation observed in metallic materials. The acceleration was due to the breaking of grain interlocking by overload. The crack growth rate recovered as crack grew in a relatively short distance after overload, because grain interlocking in crack wake was reconstructed during crack growth.
This paper describes the creep-fatigue damage evaluation of SUS 304 stainless steel in wide ranges of multiaxial stress and strain states. Low cycle fatigue and creep-fatigue tests were carried out using a cruciform specimen in a full range of strain biaxiality including equi-biaxial tension/compression at 823K and 873K. Mises' equivalent strain, maximum principal strain, the equivalent strain based on crack opening displacement (COD) and Γ*-parameter were applied to the experimental low cycle fatigue data. The latter two strain parameters gave a better correlation than the former two strain parameters. The discussion on the correlation of the biaxial creep rupture data was briefly made and the equivalent stress based on COD was the most suitable stress parameter correlating the biaxial creep rupture data. Creep-fatigue damage was evaluated based on the equivalent strain and stress based on COD. The creep-fatigue damage evaluated fell around a line of unity in value, which indicates that the linear damage rule holds in the biaxial creep-fatigue.
In-situ observation of microscopic fracture process around an open hole in short glass fiber reinforced thermoplastic GFRTP composites is conducted. The specimens with four different fiber surface treatments are used. In all the material systems, the first damage observed is fiber/matrix interfacial debonding at the fiber ends. It is observed that there is a difference in fracture process between the materials with higher and lower interfacial strength. In a material system with lower interfacial strength, debonding propagates along the fiber to the fiber center and fiber break is not observed. In a material system with higher interfacial strength, extensive debonding propagation is not observed and fiber break is observed. The micro-grid method is applied to measure the fiber displacement distribution. The shear-lag prediction is compared with the experimental results. The fiber displacement distribution obtained by the micro-grid method is found to agree well with the shear-lag prediction until extensive interfacial debonding occurs.
In order to investigate the effect of short glass fiber on crack growth, DCB samples were machined from injection-molded PMMA plates with a very little content of short glass fibers and the crack tip in the sample was observed by means of optical Interferometry. It was shown that (1) the interference fringes were distorted around the fiber crossing the crack planes over the region 2-3 times larger than the fiber diameter and (2) the fiber depressed the crack opening due to bridging between the crack planes, lessened the craze region in front of the crack and reduced the crack growth rate leaving the arrest line on the fracture surface.
With the increasing level of integration in semiconductor devices, new types of silicon wafers are developed to respond to the needs arising in electric design. The new types of wafers contain different concentrations of oxygen atoms then the former silicon wafers. Therefore, the oxygen concentration dependence of dislocation generation in silicon substrates is investigated. The specimens were silicon substrates with (on the surface) stressed thin-film bands, at whose edges stress singularity fields were formed. The Dislocation-generation strength was measured by changing the bandwidth and detecting limit bandwidth for dislocation generation. Since the limit bandwidth did not depend on the oxygen concentration, it was shown that the oxygen atoms do not affect the generation of dislocations. On the other hand, the dislocation density depended strongly on the oxygen concentration. Since the density is related to the mobility of dislocations, it can be said that the effect of oxygen atoms is only the mobility of dislocation.
The fracture surface topography analysis (FRASTA) technique which reconstructs the fracture process from the three-dimensional topographs of conjugate fracture surfaces has been used to characterize fracture mechanisms and obtain detailed information about microprocesses. In this study, the FRASTA technique was applied to four types of fracture surfaces: (1) brittle fracture of ceramics, Si3N4, (2) stress corrosion cracking (SCC) fracture of 12CrMo stainless steel, (3) fatigue fracture of cast iron, FC250, and (4) fatigue fracture of low alloy steel, SFVQ2A. The FRASTA results of these fracture surfaces were compared at each test condition after analysis to evaluate the FRASTA capability and its limitations. From the results, it was found that FRASTA had capability to reconstruct the detailed fracture process and to detect condition changes such as stress or environment, but there were some difficulties in the estimation of crack growth rate or applied stress.