The X-ray diffraction method was applied to measure the change of the lattice strain and domain switching in tetragonal lead zirconate titanate (PZT) due to poling and applied strains. The lattice strain was determined from the linear relation between the diffraction angle and sin2Ψ. The lattice strain measured by X-rays is less than 50% of the macrostrain determined from the dimensional change due to poling. The applied strain induced the increase of the lattice strain, and the amount of increase was about 50% of the applied strain. The amount of domain switching was evaluated by the change of the intensity ratio of 002 diffraction to 200 diffraction. The intensity ratio was decreased with the applied strain. The broadening of X-ray diffraction profiles obtained from the diffraction plane perpendicular to the poling direction was the maximum, indicating the largest microstrain in the poling direction.
Residual stress generating in each component phase is formed due to the disturbance strain by interaction between the composition phases as for Fe-Cr steel/TiN system composite prepared by powder metallurgy (P/M). We can obtain macro- and microstresses by using X-ray stress measurement method. And X-ray fractography technique was advanced in the field of the fracture analysis. In this study, we tried to fracture toughness test by using three points bending test pieces which have a different notch radius. Effects of notch radius on stress intensity factor when the crack arisen were discussed. Distributions of residual stress and plastic zone depths near fracture surface were evaluated. Experiment results obtained were approved to the equation of the fracture mechanics.
A dual phase stainless steel consists of almost the same amount of both ferritic and austenitic phases, and possesses good corrosion proof as well as high strength characters, so that this material is used for ocean structures etc. Commonly, dual phase stainless steals are processed for industrial use by rolling, cutting, grinding, etc. Residual stress generated during these processes plays important role in practical use. Thus, measurement of residual stress in the dual phase stainless steal is very important. However, as this material is one of the composite materials in which different constituents with different physical properties such as an expansion coefficient and a mechanical property are involved, each constituents will posses a different residual stress and plastic strain due to the heat-treatment and/or other mechanical processes during manufacturing. Such microscopic complex state may affect the macroscopic properties of the material. In this study, these problems were investigated using the method of the X-ray stress measurement by which the residual stress in each constituent of composite materials can be obtained. In addition, effects of changes in grinding depth of cut on the residual stress in dual phase stainless steel were also discussed.
Surface roughness, hardness and residual stress of TiN films deposited on stainless steel substrates by an arc ion plating method were examined by changing arc current and nitrogen gas pressure, respectively. The TiN films have an average roughness of about 0.1 to 0.3μm, while the surface roughness decreases with increasing nitrogen gas pressure. Vickers micro hardness tests revealed high hardness (HV 1650-2500) whose value depended on nitrogen gas pressure and arc current, respectively. X-ray photoelectron spectroscopy analysis showed the ratio of nitrogen to titanium (N/Ti) of from 0.85 to 0.92 in the as-deposited TiN film. The X-ray diffraction pattern showed the crystal orientation of the TiN film depends on the nitrogen gas pressure. By using a two-exposure method, residual stresses in the TiN films were measured as a function of nitrogen gas pressure and arc current, respectively. The TiN films showed very high compressive residual stresses of about-8.0 to -7.0 GPa.
The commonly used X-ray stress measurement, so-called sin2Ψ method, is valid for the stress determination from the X-ray diffraction data. However, the method fails if the samples are anisotropic because the method is constructed from some assumptions, one of which is that the samples are regarded as isotropic and homogeneous polycrystalline materials. Therefore, in order to be applicable the polycrystalline materials with ‹HKL› preferred orientation, the method was improved by the introduction of the rotation symmetry about the normal axis to the X-ray diffraction plane in this paper. The basic equation in the X-ray stress measurement i.e. the X-ray stress - lattice strain relation was derived for ‹HKL› preferred orientation in result. Then, the method applied to a centrifugal casting part, and was discussed in comparison with the sin2Ψ method.
The purpose of this investigation is to detect a damage from actual stress distribution in the surface of specimen by using X-ray diffraction technique during fatigue test. An apparatus to measure actual stress distribution along circumference of specimen was fabricated by use of a cantilever type rotary bending fatigue machine and a stress analyzer based on single exposure technique with two position sensitive proportional counters. We proposed a method to collect separately the diffraction profile at each position along circumference of specimen. Actual stress distributions at the maximum tensile applied stress were measured during fatigue test. As results, the shape of actual stress distribution was keeping stable with increasing number of cycles until crack initiation. After crack initiation, the actual stress at the position of crack initiation was decreased suddenly near 0MPa, and the distribution was shaped “V” type. The “V” type distribution was appeared when crack length reached greater in size than a width of irradiation area. These results show that the method proposed in this study is available to detect a position and period of crack initiation.
Recently, the position sensitive proportional counter (PSPC) is becoming popular as the detector for the X-ray stress measurement. However, the author considers that the characteristics of the X-ray stress measurement using PSPC are not yet studied enough. In this paper, the influence of specimen missetting to the X-ray stress measurement is discussed based on the results investigated as one of the factors affecting the influence of computer simulation and experimental studies for the case of side inclination method. The size of collimator is also. As the results, it was found that the error in stress measurement is proportional to the ratio L/R0 (L; offset of missetting, R0; goniometer radius). About 25MPa of the error occurs at L/R0=0.0025 in the case of the measurement of ferrite sample using Cr target. The size of collimator has little effect to the relation between the error and L/R0.
Coupled metallo-thermo-mechanical analysis by use of heat treatment simulation code “HEARTS” is carried out for a ring-shaped model of Cr-Mo steel under carburized quenching: Diffusion of carbon carrier gas is calculated followed by oil-quenching from 850°C to estimate the distortion as well as structure distribution. To compensate the discrepancy between experimental data and calculated distortion, a special attention is paid on the effect of transformation plasticity. Several trials of simulation depending on the intensity of the effect shows that the transformation plastic strain plays an important role on the mode of distortion during carburized quenching process while a little effect is seen for normal quenching.
Thermal barrier coatings (TBCs) had been already applied to hot section parts of gas turbines, such as a bucket and a combustor. It is thought that TBCs are in dispensable for the gas turbines in company with cooling technologies. Nowadays, it is desired the higher durability to TBCs with increasing the combustion temperature. The object of this study is to clearify the sintering behavior under the condition of gradient temperature for the plasma sprayed zirconia TBC in air atmosphere. On the assumption based on experimental results that the linear shrinkage of zirconia coating followed a 2/5 power time law and an Arrhenius type temperature dependence of sintering rate constants, thermal stress behavior due to sintering under the gradient temperature was made clear by the simulation analysis. There was a tendency that the tension stress at zirconia coating layer increased with increasing the combustion temperature and heating time. The cracking conditions of zirconia coating was estimated by paying attention to the shrinkage stress and residual stress due to the difference of thermal expansion.
The corrosion behaviors of ceramics (Si-SiC, SiC, Si3N4, Al2O3, ZrO2) were examined in boiliing 95 wt% sulfuric acid by measuring weight change, concentration of dissolved ions in the sulfuric acid, 4-point bending strength and apparent hardness calculated from Load-Depth curve obtained by Micro- Indentation technique. The corroded surface and the fracture surface of the specimens were analyzed by SEM and EPMA. The corrosion behaviors of these ceramics were divided into 3 types; (1) Si-SiC and SiC showed excellent corrosion resistance because of protective oxide films which developed during immersion, (2) the bending strength, apparent hardness of Si3N4 and Al2O3 decreased with increasing immersion time because of corroded layers produced during immersion, and (3) the bending strength of ZrO2 decreased with remarkable weight loss. The thickness (T) of oxide films and corroded layer produced on Si-SiC, SiC, Si3N4 and Al2O3 was evaluated from the depth (d) which was determined by the slope change on Depth-Load/Depth curve. The relationship between T and d was described as T≈10d. The bending strengths of Si3N4 and Al2O3 were evaluated from thickness (T) of corroded layer and KIc obtained before immersion. As a result, the bending strengths of Si3N4 and Al2O3 could be determined with both the KIc and the equivalent crack length (ae) to 20d.
Effects of fretting on fatigue strength of mechanically fastened GFRP joint were examined experimentally under the tensile cyclic load. The laminated composite used in experiment was the glass fiber reinforced epoxy resin. The composite was bolted with two steel plates by SUS304 austenititic steel bolt as a lug joint. As the results, the following conclusions were obtained: 1) The higher fastening-up pressure of the bolt of the mechanical joint, moreover the lower stress amplitude, it was easy for fretting to develop, and also the fretting fatigue failure occurred from the crack which was initiated in the fretting region between specimen and washer. 2) In case of the mechanical joint failed at the circular hole, the lower contact pressure increased the deformation of the circular hole, and the fatigue strength of the mechanical joint, which failed due to the stress concentration, decreased with the lower contact pressure. 3) The fatigue strength of the mechanical joint tended to increase with the increase of bolt fastening-up pressure. 4) The fatigue strength of the mechanical joint tended to decrease in the higher cyclic frequency, and it was thought that the influence of temperature rise caused by the heat which GFRP material itself generated and by the friction which was caused by fretting.
Fracture strength and fracture behavior of sintered two-phase tungsten alloy specimens with various notch root radii were investigated. Cracks mainly initiated by interface decohesion between tungsten particles at the notch root. Cleavage fracture of tungsten particle was observed for the material with higher volume fraction of ductile matrix phase. No significant variation of crack initiation strength was found for notch root radii larger than 5mm. However, crack initiation strength significantly decreased with reducing notch root radii for the radii smaller than 5mm. The non-linear notch mechanics proposed by Nisitani et al has been successfully applied to the present materials.
In this paper, the functions expressing both crack opening displacement and sectional forces for an infinite plate with a straight crack subjected to out-of-plane uniform loads acting on its edge have been obtained. The phenomenon that the obtained equivalent shear forces through a numerical example turn from plus figures to minus figures in assumed fracture process zones is observed. Finite element method (FEM) is utilized to verify the phenomenon. Providing spring supports with different constant values at nodes in the process zones, FEM analysis provides almost same displacements and the similar shape of equivalent shear forces as those of the numerical example. In the case of out-of-plane problem, it is found that a concentrated load at the center of a crack provides the larger effect in the maximum sectional force than uniform load acting along full width of the crack, when the total magnitudes of the both loads are equal. On the other hand in the case of in-plane problem, the larger width of applied loads provides the larger effect on the maximum stress.
In this study, we deal with an axisymmetrical mixed boundary value problem for a nonhomogeneous medium with a crack. It is assumed that the nonhomogeneous material properties of shear modulus of elasticity G varies with the axial coordinate z according to the power product form, i.e., G(ζ)=G0ζm. As an analytical model, a nonhomogeneous half-space with a penny-shaped crack subject to uniformly distributed loading such as internal pressure on the crack surfaces is considered. Making use of a fundamental equation system for such a nonhomogeneous medium, which is already derived in our previous paper, this axisymmetrical elastic problem with a singular stress field is developed theoretically. Then the simultaneous dual integral equation of Fredholm's second kind derived from the discontinuous boundary conditions on the crack surface and its extended surface is solved numerically. Numerical calculations for the elastic field and singular stress field are carried out, and the numerical results for displacements, stresses and the stress intensity factor at a crack tip are shown graphically, Finally, the influences of the nonhomogeneous material property and the distance from the boundary surface to the crack surface affected on the elastic behavior such as displacements, stresses and the stress intensity factor are examined precisely.
Tantalum-oxide films were deposited on SUS304 by PLD under O2 gas and 5 mass% O3 gas at room temperature. Effects of atomic ratio of O/Ta and Ta-O binding state on corrosion resistance of tantalum-oxide films were investigated systematically. Corrosion resistance of the films was examined by the measurement of anodic polarization curve in 3.5 mass% NaCl solution. The penetrated potential of the films deposited under O2 gas as well as 5 mass% O3 became higher with the atomic ratio of O/Ta increased. The film deposited under 5 mass% O3 gas at 10Pa had excellent corrosion resistance equal to Ta plate. Moreover, in order to evaluate of corrosion process, anodic polarization test was examined up to 200mV. The pits depth of the films deposited under 5 mass% O3 gas was shallower than that under O2 gas because of its stable Ta-O combination.
Conventional epoxy-modified mortars and concretes have an inferior balance between applicability and cost performance due to the necessity of two-component mixing of epoxy resin and hardener and high polymer-cement ratio of 50% or higher. In addition, the pot life of the mixture of the epoxy resin and hardener is limited after mixing them. In this study, the latent-curing epoxy resin containing microcapsuled curing agent which does not react with the epoxy resin at normal temperature and starts a chain reaction at 80°C or more is used as a one-component epoxy resin for cement modifier. Epoxy-modified mortars using the one-component epoxy resins and conventional two-component epoxy resins are prepared with polymer-cement rations of 5 to 20%, and subjected to flexural, compression, water absorption, drying shrinkage tests at the curing periods of 28 days. In the preparation of the polymer-modified mortars using the latent-curing epoxy resin, the specimens of the mortars are heat cured under 80°C for polymerization at 2 days after casting. From the test results, the one-component latent-curing epoxy-modified mortars have good workability, high flexural and compressive strengths, ductility and resistance to water absorption compared to those of the conventional two-component epoxy-modified and unmodified mortars. The one-component latent curing epoxy-modified mortar can successfully be used for preparing thin precast products because of such superior properties and smaller drying shrinkage after heat cure.
In the present study, methods in which the debonding is detected in the adhesively bonded joint constructed with aluminum and pultruded GFRP (PULGFRP) plates using an optical fiber have been investigated. The proposed detecting methods for the debonding in the bonded joints utilize the breakage of the embedded optical fiber caused by the damage such as cracks. In the present study, two detecting methods for the debonding in which the situations of the embedded optical fiber in the bonded joint were different were adopted, and their ability of detecting the debonding were examined. Further, the effects of embedding the optical fibers in the bonded joints on the strength of the joints were investigated, and the ability of the detection of the debonding in the joints whose adhesives were in undercure was also studied. From these results, the applicability of these detecting methods to the health-monitoring system were investigated. As the conclusions it was obtained that one of the two methods could be applied to the health-monitoring system as the detecting method for the debonding in the Al-PULGFRP adhesively bonded joints.