Materials Science Forum Vols. 561-565

Abstract: In this study, the possibility of electrical discharge pulse sound for new inspection technologies instead of hammering test was investigated. Electrical discharge pulse sound was applied for hammering sound and sensor by using sound detection was applied for the optical fiber vibration sensor. Elastic wave was detected by optical fiber vibration sensor during electrical discharge. The plate thickness was changed from 0.5mm to 10mm. On the assumption that generation factor of elastic wave was only depending on a force, numerical analysis by using the finite element method (FEM) was adapted. The numerical analysis result using the FEM and the experimental result along with the electrical discharge were compared. The plate thickness was estimated by comparing with experimental signal and simulation one. It was found that plate thickness was able to estimate from comparing with experimental signal and simulation one. Moreover, a quasi-defect was created the plate by comparing with experimental results and simulation one. It was found that the defect shape was able to estimate by comparing with experimental results and simulation one.

Abstract: Product lifecycle management is one of the main developmental aspects of advanced manufacturing technology. Anti-fatigue design is the key content in product lifecycle management. For designing the fatigue life of shaft exactly and determining the assessment method, the influencing factors must be realized roundly. The mechanical model of shaft is set up at first, and then the main factors that affect the fatigue life of shaft is discussed, the interrelations of the main factors and the framework are founded. The assessment equation of fatigue life for shaft is put forward and the influencing coefficient of multi-axial stress to fatigue life is analyzed. The results of this paper will establish the base of anti-fatigue and assessment life of shaft.

Abstract: It is legally demanded that the wastes containing asbestos should be change to harmless substances completely due to the harmful effects of asbestos fiber on health. The purpose of present research was to construct a safe, reliable and facile technique by using mechano-chemical reaction, which is a non-combustion process and operated in a closed system. It was confirmed that the needle crystal of chrysotile asbestos was changed perfectly to amorphous state after grinding by using a planetary ball mill. Furthermore, these products could be remade to useful materials by addition of soil which consists of inorganic materials based on CaO and so one. After the obtained fine powders were mixed with water, pressed and held under the humid condition, the stable hydrates were found in these products after XRD analysis. These inorganic compounds were much useful as a new raw material for cement-like.

Abstract: Laser shock peening (LSP) is an innovative surface treatment technique for metal alloys, with the great improvement of their fatigue, corrosion and wear resistance performance. Finite element method has been widely applied to simulate the LSP to provide the theoretically predictive assessment and optimally parametric design. In the current work, 3-D numerical modelling approaches, combining the explicit dynamic analysis, static equilibrium analysis algorithms and different plasticity models for the high strain rate exceeding 106s-1, are further developed. To verify the proposed methods, 3-D static and dynamic FEA of AA7075-T7351 rods subject to two-sided laser shock peening are performed using the FEA package–ABAQUS. The dynamic and residual stress fields, shock wave propagation and surface deformation of the treated metal from different material modelling approaches have a good agreement.

Abstract: Surface preparation is potentially important to the mechanical and biomedical properties of NiTi shape memory alloys. In this paper, the effect of surface preparation on fatigue life of a Ti-55.2wt%Ni alloy has been studied. Surface of the NiTi wires is prepared by five methods of chemical etching, electropolishing, oxidizing, mechanical polishing A and mechanical polishing B, and then examined by the self-developed fatigue evaluation device. Under scanning electron microscopy (SEM) the fractures of all specimens show dimple morphology. It is found that compared with the samples after chemical treatment, mechanical polishings and thermal oxidation, electropolished sample has longer fatigue life for its lower surface roughness despite a lack of face-hardened layer.

Abstract: The microstructure simulation of spinodal decomposition was carried out in the isothermally-aged Cu-Ni-Fe alloys using the phase field method. The numerical simulation was based on a solution of the Cahn-Hilliard partial differential equation by the finite difference method. The calculated results were compared to those determined by atom-probe field ion microscope analyses of the solution treated and aged alloys. Both the numerically simulated and experimental results showed a good agreement for the concentration profiles and microstructure evolution in the aged Cu-Ni-Fe alloys. The aging process caused the change of initial morphology, iregular and interconected, to an equiaxial shape of the decomposed Ni-rich phase aligned in the elasticallysoftest crystallographic direction <100> of Cu-rich matrix.

Abstract: Three types of austenitic stainless steels JK2, JJ1 and JN1 were isothermally aged at temperatures from 873 to 1173 K for 10 to 1000 minutes in order to study the microstructural evolution. In general, the kinetics of precipitation for JN1 steel was faster than that of JJ1 steel, because of its higher interstitial solute content. The TTP diagrams showed that the intergranular precipitation of M23C6 and M2N preceded to the intragranular precipitation of M2N and M2N and η phase in JN1 and JJ1 steels, respectively.

Abstract: Recently, gram quantities of monodisperse gold or silver nanoparticles were reported to be produced through a digestive ripening process, in which colloidal particles of size 2 to 40 nm are transformed to nearly monodisperse particles of 4 ~ 5 nm diameter. Digestive ripening, an example for an inverse Ostwald ripening process, is a puzzling phenomenon since it appears to go against the usual capillary effect, i.e., reduction of interfacial free energy. A theoretical model is presented, which accounts for the monodisperse state of such nanoparticles by considering the effect of charges on the particles and thus electrostatic energy during particle size evolution.

Abstract: For steel with combination of high strength (~2000MPa) and toughness, along with low cost, the designed structure should be low-temperature tempered, fine lath martensite with high density of dislocation, coated by film of austenite with considerable thickness and distributed with fine ε (η) or (and) complex carbide. Correspondently, the steel should contain less than 0.5 (wt%) of carbon, certain amount of alloying elements for lowering Ms, such as Ni, Mo and (or) Mn, carbide forming element, e.g. Nb, as well as Si or (and) Al, the element depressing the formation of cementite, the brittle phase in high strength steel. The heat treatment process is suggested as: austenitizing at a temperature slightly above Ac3, followed by quenching at Ms-Mf, partitioning either at quenching temperature or at slightly above Ms for a few minutes, cooling down to room temperature and tempering at low temperature about half an hour.

Abstract: Although the γ"(D022) phase has been known as a strengthen phase for the turbine disk of wrought Ni-base superalloys, the computer simulation of the γ"(D022) precipitation is hardly performed. In this study, it is demonstrated that the phase-field modeling of the complex microstructure developments including γ"(D022) precipitation in Ni-V-X (X=Co,Nb,Fe) alloys. The simulation results obtained are as follows: (1) The complex morphologies of the γ(A1)+γ"(D022) two-phase microstructure, such as the maze-microstructure, the chessboard-microstructure, and the chessboard-like microstructure, in Ni-V-X (X=Co,Nb,Fe) alloys are simulated reasonably by using phase-field method. (2) The morphology of the microstructure is mainly controlled by the elastic strain energy induced from the lattice mismatch. In particular, the tetragonal distortion is a key parameter to control and understand the complex microstructure changes.