Traditional methods of preparing a kind of steel called tamahagane used for the Japanese sword by tatara system and procedure of making the sword are briefly introduced with the discussions from the viewpoint of metallurgy and thermo-mechanical processing. Such traditional methods are also revealed to be consistent with the modern science and technology. The quenching process applied to the final stage of the procedure is focussed to explain how the pattern of blade, the deformation and residual stresses are induced by the computer simulation based on the theory of metallo-thermo-mechanics relevant to the coupled fields among temperature, microstructural change and stress/strain.
Viscosity of aqueous potassium chloride (KCl) solution was measured at temperatures of 283.2 and 323.2K and pressures up to 375MPa by means of a rolling-ball viscometer. The Jones-Dole B coefficient of KCl at both temperatures increased with increasing pressure and then decreased after passing over a maximum as well as previously observed one at 298.2K. The maximum became more pronounced at lower temperatures. In comparison with the dielectric friction theory, the observation of the maximum is ascribed to a balance between two contributions; pressure breaks any water structure (B increases) and reduces the dielectric friction between ion and solvent (B decreases). The temperature coefficient ∂B/∂T was observed to be positive at all pressures and decreases with increasing pressure. The fact suggests that the structure-breaking effect of KCl for water reduces with increasing pressure, and the reduction of the effect may be ascribed that the water structure which should be broken by addition of the electrolyte is already broken by pressure.
Gels were formed in the SiO2-TiO2-ZrO2 system. All of them were amorphous by XRD analysis, even though opaque gels were formed in the compositions range more than 80mol% TiO2 and 60mol% ZrO2, and transparent gels were formed in the rest compositions. Morphology of these particles were observed by SEM. It was found that the opaque gels consisted of spherical particles and the transparent gels consisted of bulk matrix. The opaque gels containing spherical particles were of different degree of agglomeration depending on the compositions. The compositional homogeneity of the particles was confirmed by EDX. It was found that sub micron spherical particles formed during gelation process were aggregated or packed together to form micro-sized spherical particles. Gels were heat treated at 200, 400 and 600°C for 1 hour to study the crystallization behavior.
When snow or ice sticks to radio communications antennas, it sometimes causes signal transmission problems. In many cases, the degree to which snow or ice sticks to antennas is based on the degree of adhesion. We have been developing water-repellent coatings to prevent such adhesive problems. In this paper, the snow adhesive property of these water repellent coatings is experimentally studied. We obtained following results. (1) Much more fallen snow adheres to FRP samples than water-repellent coatings. (2) Much more fallen snow adheres to samples at +1.5°C than at -5°C. (3) Snow naturally falls off of the surface when its weight reaches a certain value. (4) The estimated value of snow falling off consists with experimental value.
The heat treatment effect on transformation properties of a NiTi Shape Memory Alloy (SMA) film is discussed. TiNi SMA films were deposited by using sputter deposition techniques, and were then solution-treated and aging-treated. The phase transformation properties were investigated by means of a differential scanning calorimeter (DSC), X-ray diffractometer and a transmission electron microscope (TEM). As sputtered film had an amorphous structure with fluctuating density of titanium atoms. The films solution-treated at 600°C and aging-treated at 400°C had several kinds of phases. The rhombohedral phases, austenite phases and amorphous phases could be distinguished within the same film. The film solution-treated at 800°C and aging-treated at 400°C showed the largest enthalpy of the transformation and had the preferable crystalline structure. The samples solution-treated at 1000°C, in which NiTi were resolved partially into Ti2Ni and Ni4Ti3 were more brittle.
Establishment of nano-scale machining technologies is required in the field of ultra-precision fabrication where it is important to clarify cutting phenomena such as chip formation, cutting force, surface roughness and sub-surface damage. The present paper investigates the diamond machining of a copper single crystal with atomistic defects by means of molecular dynamics simulation. Postulating the Morse potential, the influence of initial vacancies and duplex cutting on the cutting mechanism is analysed when a (111) plane of the crystal is orthogonally machined in a  direction. Existing vacancies and edge dislocations in the copper result in further disorder of the lattice structure and an increase of cutting force owing to the interaction between the defects and the dislocations propagated from the tool tip. These phenomena can be observed at a vacancy density of 0.5%. In the case of the duplex cutting of the perfect crystal, displacement of the work atoms is limited to at or just below the finished surface, requiring a lower cutting force and producing more work atoms removed as a chip. These results suggest that a prerequisite for a damage-free machined surface is that the work material be as pure and perfect as possible.
The applicability of the FFT-based algorithm for evaluating the mechanical behaviors of composites is investigated from practical view points. After the iterative numerical algorithm is presented, the computational efficiency is compared with that for conventional FEM-based homogenization algorithm and then extended to nonlinear analyses such as elastoplastic problems. In addition to preferable features in microstructural analyses, there are several advantages over the conventional approach by the FEM-based homogenization method. While the method is for evaluating the micromechanical response to the macroscopic deformation, the solution method can also be utilized to estimate the homogenized material constants. In the numerical examples, the digital image processing technique is extensively utilized to define the geometry of microstructures so that the method would not suffer from modeling effort.
A creep life assessment method was proposed for base metal and HAZ of 2.25Cr-1Mo steel STPA24 used in high temperature steam piping of fossil power plants. Microstructural observations and hardness measurements were carried out for base metal and simulated HAZ after thermal aging and creep testing. Simulated HAZ material showed significant softening during thermal and creep exposure, but base metal showed less softening. Hardness equation was established based on the kinetics of carbide coarsening and recovery of dislocation substructure. Creep damage was evaluated by damage mechanics in combination with softening equation and creep constitutive equation. The proposed method can be applied to assess creep life of Cr-Mo steel HAZ in actual components.
Aqueous Corrosion/Deformation Interactions (ACDI) in uranium and uranium alloys actually exhibit complicated mechanical damage processes. In this context, the exploration of the dominant micromechanical mechanisms vis- a -vis experimental confirmations remain an unsettled issue. Various mechanisms might be involved in such environmental effects, starting from stress corrosion cracking (SCC) hydrogen embrittlement, up to brittle film fracture or film-induced cleavage, enhanced or inhibited by diffusion barriers. These on top of hydride formation which potentially affects the local mechanical/chemical driving field. Thus, beside the driving force modifications, the reduction of the fracture resistance requires appropriate evaluations. The main objective in the current phenomenological investigation was, to provide additional findings as related to damage evolution in specific ACDI systems. In fact, the present selected systems allowed further insights into a low symmetry, orthorhombic crystal structure case. Experimentally, sustained load, slow strain rate (SSR), monotonic and fatigue tests in fracture mechanics framework were performed, supplemented by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) observations. In addition, X-ray, Fourier Transform Infrared spectroscopy (FTIR) techniques and acoustic emission (AE) tracking were utilized. Experimental findings are analyzed and discussed with emphasis to fractographic observations and kinetics associated with the crack propagation stage. These beside developments in modeling aspects founded on a stepwise decohesion processes.
This paper deals with the experimental investigation on the effects of the corrosion of reinforcement due to the sodium chloride on the yield strength, the tensile strength and the elongation relating to the fundamental concept of the RC structure design. The main conclusions are as follows: (1) The long term corrosion rate over four cycles becomes a constant value of about 180mdd. (2) The corrosion degree of round bar is much larger than that of steel plate. Therefore, the covering of the RC members is very important. (3) The tensile strength of reinforcement depends on the “structure-sensitive” property concerning the pittings. (4) The special attention must be paid to the tensile strength, the elongation and the toughness of the reinforcement from the viewpoint of the earthquake-resistant RC structure.