This paper deals with possibility of cold and warm bending for cylindrical pipe of AZ61(Mg-6%Al-1%Zn) magnesium alloy. Work piece is a pipe of 22mm outer diameter D and 18mm inner diameter. The pipe of 330mm long with a support distance of 240mm for bending test was prepared. Three kinds of upper bending dies with average bend line radius R of 66, 55 and 44mm were used. Bending tests were performed at four kinds of test temperature (T=293, 393, 473 and 573K) and at a crosshead speed v of 100mm/min. On the bending test, loading was stopped when the bending angle became nearly an aimed angle of 90° or when some cracks occurred on the surface of pipe and the load was rapidly down. Tensile and compressive tests for test pieces cut and finished from the AZ61 alloy pipe were also performed at four kinds of test temperature. The discrepancy between tensile and compressive yield stresses is larger at 293K, but it becomes smaller with increasing the temperature and it nearly equals at 473K and 573K. At every test temperature, in case of R/D=3, the pipe was successfully bent up to the aimed angle of 90° without any damage. However, in case of R/D=2, the pipe had a crack on the inner compressive stress side at 293K and 393K, but it did not have any crack at 473K or over. It suggests that the experimental compressive fracture strain ε_fc is strongly related to the limit of bendability of AZ61 alloy pipe.

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On growth beyond a critical size coherent precipitates become semicoherent by the formation of an interfacial misfit edge dislocation loop. On further growth of the precipitate, the interface progressively loses its coherency by the formation of additional dislocation loops. The current investigation pertains to the energetic feasibility of two dislocation loops. Finite element simulations are performed to simulate the stress state of the semicoherent precipitate and to compute the radius of the precipitate at which two symmetrically positioned dislocation loops become energetically favourable. Aspects regarding the stability of the loops are also explored using the simulations. Cu-γFe system is used as a model system to illustrate the methodology and to capture the essential aspects of the process.

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Micro-patterning of nerve cells is important technical issue to clarify their function and/or apply cell-based biosensors. Self-assembled particles are candidate for simply micro-structured scaffold to enable cells to adhere selectively. In this present study, using silica (SiO₂) particles modified by specific protein, effects of particle-structure and protein-modification are investigated in a case of cultured rat pheochromocytoma (PC12) cells. SiO₂ particles are gradually covered with specific protein, fibronectin (FN), by using electrostatic force with pH of FN solution kept at 4.0-8.5. It is also confirmed that FN coverage is proportional to reaction time. Dip-coating to pre-patterned glass plates, on which straight lines of hydrophobic molecules are arranged, allows the FN-coated SiO₂ particles to be autonomously structured in a line-and-space pattern. The width and thickness of assembled particles are 35 µm and a few micrometers, respectively. It is also demonstrated FN is successfully supported to the surface of SiO₂ particles throughout the structuring process. PC12 cells are incubated on the glass plate at 100% humidity and 310 K. The structured particles work as a scaffold for PC12 cells. Most cells preferentially adhere to FN-coated SiO₂ particles. The adhered cells, which are located at the center of structure, are aligned at regular intervals. Meanwhile, in the case of flat glass region and structured bare particles, the number of adhere cells are remarkably small as compared to that of FN-coated SiO₂ particles. It is found that an increase of FN coverage raises the number of adhered cells on the particles. These experimental results demonstrate that the structure of protein-coated particles have a function to induce self-alignment of cells. This indicates subsequent differentiation enables a desired network of neuron on the structure.

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We propose a novel evaluation method to obtain precise stress-strain curves by spherical-tip nanoindentation with continuous multiple loading technique. The small-sized spherical-tip indenters have an imperfect shape and it causes miss-fitting with tensile test result. We adopted the variable radius method, where we defined the precise indenter radius as the function of contact depth to calculate the stress-strain response precisely. We calculated the representative stress and representative strain by combining Hollomon's law, Hill's model, proper strain model, and the variable radius and compared with the tensile test result. It is found that stress-strain curves obtained by using the variable radius method agree well with the tensile test result rather than using nominal radius. These results clearly indicate the effectiveness of our method to evaluate the stress-strain response by using the small-sized spherical-tip indenter.

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Gels are kinds of soft and wet materials, having many unique characteristics such as low friction, material permeability, and biocompatibility. In the last decade, the mechanical weakness of the gels has been overcome by the advent of novel high-strength gels, which promises to expand the industrial and medical applications of the soft and wet materials. Here an optical 3D printer was developed to fabricate high-strength gels with free form. For fabricating the gel materials by the printer, one of the strongest gels, called Double-Network (DN) gel, was used. The DN gels were easily prepared by using the grained particle type of the1st gels. The DN gels prepared by this method were named the particle-DN gels. The particles of the 1st gels were mixed with the 2nd pre-gel solution, and the solution was gelled by the irradiated of UV light. In the printer, the laser beam of UV light was lead to the solution through an optical fiber and the scanning of the fiber in the solution was controlled by 3D-CAD. The printer was named Easy Realizer of Soft and Wet Industrial Materials (SWIM-ER). The mechanical properties of the DN gels printed by the SWIM-ER were evaluated.

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Tribological attributes of Mg-alloy (AZ91D) based composites reinforced with 5, 10, 15, 20 and 25 wt% of silicon carbide particle (SiC_p) synthesized by stir casting technique are being investigated. The composites show uniform distribution of SiC_p and possess refined grains in comparison with the monolithic alloy. The cleaner interface depicts splendid interfacial bonding. The dry sliding wear behavior of the composites has been characterized using a pin on disc wear testing machine at two different normal loads of 19.6 and 39.4N. The volumetric wear rate, wear resistance and coefficient of friction for the composites shows phenomenal variations with fluctuations in load and SiC_p content. Scanning electron micrographs of wear surface and wear debris provide excellent insight of the type of wear involved.

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Waveform simulation techniques are widely used for nondestructive inspections using elastic waves. They are also used for the acoustic emission (AE) technique. Source dynamics can be identified by AE waveform analysis. However, waveforms detected by AE sensors are deformed by the sensor response, and their characteristics depend on the frequency response and sensitivity; thus, accurate AE waveform simulation is difficult because of these problems. In this study, accurate AE waveform simulation involving a sensor response, using a finite-difference time-domain (FDTD) method was developed. The original waveform is calculated by the 2D FDTD method. The sensor response is determined by extraction of the input waves to the AE sensor by a pulse generator and detection by a laser interferometer. To include the sensor width and dispersion of the sensor response, some points of the sensor response on the sensor face are detected. These are convoluted, and the sensor responses of all points are added. After Lamb wave simulation, characteristics of the simulation waveforms were correlated to the artificial AE waveform produced by Hsu-Nielsen sources (pencil lead breaking). AE signals from mode I fracture were simulated next. The fracture was excited by exfoliation between a polyester plate and glass bar embedded in the plate. The characteristics of simulation waveform by developed technique corresponded to the waveform detected by the AE sensor.

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For this study, four kinds of DLC films were prepared using the ionized evaporation method. The substrate voltage was controlled, from 1 to 3 kV. Three kinds of films were prepared with benzene, and one with cyclohexane as the source gas. The DLC structure could be controlled using these parameters. This is related to hardness and optical properties. Various types of DLC films, which were used in round-robin testing for standardization were also analyzed in this study. These DLC films were deposited on Si substrates using the ionized evaporation method, the sputtering method, the arc method, and the plasma CVD method. The hardness of DLC films was determined using the nano-indentation technique. The refractive index and the extinction coefficient of DLC films were evaluated using a spectroscopic ellipsometer. The refractive index of tetrahedral amorphous carbon (ta-C) was found to be relatively high, from 2.50 to 2.74, whereas the extinction coefficient was low, from 0.04 to 0.50. For hydrogenated tetrahedral amorphous carbon (ta-C:H), the refractive index was lower than ta-C. Hydrogenated amorphous carbon (a-C:H) showed its own unique extinction coefficient and refractive index range, as did amorphous carbon (a-C). The refractive index was found to be proportional to the hardness of DLC films. The refractive index and the extinction coefficient were different depending on the kind of DLC, which were in turn related to the deposition method and DLC structure. Using optical properties, such as the refractive index and the extinction coefficient, we can distinguish the type of DLC film.

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For high-sensitive micro bio-analysis, fabrication of micro/nano structure by synthesis of vertically aligned carbon nanotubes (VACNTs) and self-organization, and improvement of surface activation of the CNTs by Ar plasma irradiation were performed in this study. The influence of structure dimensions and plasma irradiation on the bio-analysis was investigated. CNTs structures with various feature size and with various treatment conditions was fabricated, and protein adsorption characteristics on the CNTs structures were evaluated by fluorometry. The results revealed that the adsorbability of proteins depends on structure and surface treatment condition significantly. Finer structures with proper treatment tend to adsorb more proteins. The adsorbability for the CNTs reaction fields with finest structure and with best treatment condition was improved more than 30 times.

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Influence of a nano- (ns) and a pico-second (ps) laser pulse in annealing and texturing of amorphous-silicon (a-Si) films on crystalline silicon substrates by pulsed Nd³⁺:YAG lasers is investigated. In theoretical studies, the thermal model was considered for the ns-laser annealing and the plasma model with an appropriate energy relaxation time was used for the ps-laser annealing, as both the processes are different on a time-scale. Crystallization depth was estimated at different wavelengths, and interface temperature between a-Si films and c-Si substrates was compared. Modeling results shows that with a ns-laser annealing at longer wavelength (1064 nm) has a weak absorption and therefore higher laser fluence is required to raise the film temperature to a required level and it was in agreement with the experimental results. Also the estimated heat diffusion region at the a-Si/substrate interface was significant due to the ns-order pulse-width. Whereas, in the case of a ps-laser (1064 nm), it was possible to anneal the a-Si film with a lower laser fluence. In addition, the estimated heat diffusion length at the a-Si film/substrate interface was lower than the ns-laser assisted treatment.

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One of the authors developed a new micro piercing process by combining press indenting and chemical etching. By using conical and V-shaped indenters, circular and rectangular holes having tens of micrometers in size were successfully produced for 0.1mm thick copper alloy sheets, respectively. In this paper, multiple holes were pierced by this method and the influential factors on the accuracy of holes were investigated. The hole was distorted when the indenting pitch was below a specific threshold. The threshold pitch for rectangular holes was considerably larger than that for circular holes, which was explained by metal flow during indenting. As far as an adjacent hole was not distorted by subsequent indenting, dimensional accuracy of holes was affected by the tip angle of indenters, but little affected by the shape of holes.

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Gels have unique properties such as low frictional properties, permeability and biocompatibility due to their high water content. When the gels are developed as industrial materials, we need to establish a method of quantitative analysis derived from the internal structure and mechanical properties of these gels. In this study, the internal structure of the dry-synthesis gels were precisely examined experimentally by the scattering microscopic light scattering and theoretically by the tensile test. By comparing the two quantities, the dense network structure makes the mechanical properties of gels smaller than theoretical estimation. Based on our findings, the strength of the gels can be controlled and expected.

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The frictional behavior of the two kinds of high-strength gels, which were double network (DN) gels and shape memory gels (SMG), was studied. By using a commercial measuring instrument with an empirical fitting function, the coefficient of dynamical friction for the DN gels and the SMG was determined. The velocity dependence of the coefficient looked roughly similar for both the DN gels and the SMG, however the details of the dependence were different. The coefficient of the DN gels was smaller than that of the SMGs. The coefficient decreased as the normal force increased. This normal force dependence was observed for the DN gels previously, however for the first time for the SMGs. The differences of both the velocity and normal-force dependences between the DN gels and SMG were discussed in relation to their mechanical properties determined in the previous studies. It implied that the difference of the dependences was possibly related to the different softness of the gels.

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Accurate determination of friction at the die/billet interface in hydrostatic extrusion is a complex issue due to involvement of various operating parameters viz. billet velocity, die geometry, contact pressure, material parameter and the regime of lubrications prevailing at die/billet interface. Therefore, the objective of this paper is to investigate friction and friction stress at die/billet interface in hydrostatic extrusion process of aluminium based alloys. The friction stress at die/billet interface is numerically computed for three lubricants whose rheology is represented by Roelands' viscosity model. Investigations have been carried out for friction stress variations along the work zone for a wide range of extrusion ratios (A = 2 to 10), semi-die angles (θ = 10⁰ to 20⁰) and material parameters (G = 0.67 to 1.86). Moreover, the validation of the proposed model has been done with the published work available in the literature.

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Hydrogels have low frictional properties, permeability and biocompatibility thanks to their high water content. However the problem of common gels is their brittleness as industrial materials. In the last decade, several high-strength gels have been developed, promising for applications of gels as new smart industrial materials. Here we study the smartness of novel ultrahigh ductile gels having Inter-Crosslinking Network (ICN), focusing on mechanical properties and structure. Three types of mesh densities of the ICN gels were experimentally determined from the size of internal structure, water content and Young's modulus of tensile test. By comparing the three mesh densities, the relation between the network structure and mechanical properties of the gels is possibly discussed. The new way to evaluate the ductility of the ICN gels was also introduced on the analogy of the small-world network model. The effect of the degree of polymerization on the ductility was discussed.

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The present study aims to clarify the scale dependency of progressive adhesion behavior of work material on micro tools under the dry friction in microforming. Scaled progressive deep drawing test up to 300 times is conducted under dry condition in micro- and milli- scale. The process dimensions of 0.97mm and 5.82mm in drawn cup diameter are produced with the stainless steel foils of 0.05mm and 0.3mm in thickness, respectively. The experimental results show that the transition of maximum punch force has different tendencies in each scale. These tendencies are well corresponded to the transition in surface state of tools and drawn cups. While, the strong adhesive wear is observed for the milli-scale, there is a slight change in the surface state of the tools for micro-scale. To investigate this difference in the adhesion behavior of the work material in each scale, a finite element analysis considering surface asperities is conducted. The distribution of the adhesion volume on the die corner radius is evaluated with a semi-empirical wear model in which is calculated with a function of normal pressure and relative velocity between blank and die. The results show the low adhesion volume in micro-scale, due to the short sliding distance during the process. The progressive adhesion behavior of work material and the advantage of tool life in micro-scale metal forming are demonstrated.

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For the austenitic stainless steel of SUS316L and SUS304L, the braze pressure welding (BPW) was applied with variation in the total heating time 60s-660s, and with the cleaning temperature of 1280°C and 1180°C. To evaluate the corrosion resistance of the BPW joint interface, the reactivation rate, R, of sensitization was measured using the EPR test. For SUS316L, the reactivation value increased proportionally with the total heating time. For each total heating time, its reactivation value was comparable with that of SUS304L. For enough total heating time longer than 360s, R value stayed constant. The R value was suppressed with lowering cleaning temperature. The proportional increase in the reactivation rate indicates the sensitization of the austenitic stainless steel with the total heating time. SUS316L's R value was comparable with SUS304L. Therefore, the sensitization of the BPW joint might occur by other than the precipitation of the chromium carbides. The corrosion degradation of BPW joint could considered to be due to the delta ferrite formation at higher temperature than 1200°C followed by the decomposition into the sigma phase. The results of this research suggest the sensitization of BPW joint could be suppressed by shortening the total heating time.

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This article reports the effect of individual additions of Pb and Y on the precipitation sequence and mechanical properties of AZ91 magnesium alloy. Discontinuous phase is greatly suppressed with Pb addition, since Pb in solid solution effectively reduces the diffusion of Al and Mg atoms, which is significant for the formation and growth of discontinuous phases. Suppression of the discontinuous phase is also obtained with Y addition but in lesser extent. Besides, addition of Y introduces Al₂Y phase which significantly refines the grain size by acting as potential nucleants for Mg grains. Pb addition moderately reduces the strength properties whereas improved mechanical properties are obtained with Y addition due to the formation of hard intermetallic Al₂Y phase and refine grain size.

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Usually, development of automobile brake hose and power steering hose has been realized through investigating several actual prototype hoses experimentally. Recently, high durability for brake hose has been required because periodic renewing the brake hose has not been requested anymore. In this study, three-dimensional FEM analysis has been applied to the crimped portion of hydraulic brake hose in order to investigate the effects of manufacturing errors upon the sealing performance. In order to evaluate the sealing performance, the normal stress σ_r appearing between the inner rubber and nipple is mainly considered. Then, the sealing performance is investigated when the manufacturing error is included for the crimped portion of hydraulic brake hose. It is found that maximum stress between the nipple and inner rubber decreases by less than 30% when the manufacturing errors are smaller than the upper limit of tolerance. It may be concluded that the error may causes deterioration of sealing performance of hydraulic brake hose.

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A layered material consisting of porous poly(ε-caplolactone) (PCL) as the top layer and porous poly(L-lactide) (PLLA)/ hydroxyapatite (HAp) composite with cylindrical PLLA reinforcement as the bottom layer was newly developed for osteochondral tissue engineering application. Deformation behavior of the layered material was then examined by compression test, and the compressive moduli were compared with those of porcine articular tissues. It was found that the compressive stress-strain behavior was characterized by a two-step elastic behavior in which the first and the second elastic deformations were mainly controlled by the softer PCL layer and the harder composite layer, respectively. The first and the second moduli were found to be in the same order with the moduli of cartilage and subcondylar bone of porcine joint tissues, respectively.

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In the present study, the enriched finite element method (enriched FEM) is used to analyze the intensity of singularity in 2D-dissimilar material joints. Using the enriched FEM, the intensity of singularities can be directly evaluated and very refined mesh around the singular point is not necessary. An eigenvalue and eigenvector analysis by FEM is used to calculate the order of singularity and the asymptotic displacement fields on the enriched elements. The singular stress fields in three-material joints described by 2-real singularities are analyzed. In order to investigate the influence of material properties and boundary conditions on the singular stress field, models with various material combinations and loading styles (tensile and shear loadings) are considered. The relationships between the order of singularity, the intensity of singularity and the maximum stresses are discussed. Finally, the circumferential stresses, σ_θθ, and individual singular stress terms for the order of stress singularities, λ₁ and λ₂, are plotted, and the relationship between each singular term and asymptotic stresses is discussed.

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Green composites, such as natural fiber reinforced naturally-derived plastics attract much attention because of reducing CO₂ emission. Many studies about green composites have enabled the materials substitutes as glass fiber reinforced composites. However, lack of investigations about fatigue properties restricts the actual usage of the composites. In the present study, we investigate fatigue properties of green composites. A hemp fiber yarn reinforced poly(lactic acid) composite was selected as a green composite. Unidirectional (UD) and textile (Textile) composites were fabricated using micro-braiding technique. Fatigue tests results indicated that fatigue damages in UD composites was splitting which occurred just before the final fracture, while matrix crack and debonding between matrix and fiber yarn occurred and accumulated stably in Textile composites. These results were consistent with modulus reduction and acoustic emission measurement during fatigue tests.

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A structural health monitoring system using multiple fiber Bragg grating sensors (FBG sensors) was developed. The system was designed to measure a large and fast strain change and to measure acoustic emissions (AE) simultaneously. The strain up to 1% and up to 100 kHz was considered. A multiple fiber ring laser was adopted as a light source, consisted of a multiple erbium-doped fiber amplifier (EDFA), an optical circulator, optical couplers, and FBG sensors. Its lasing wavelengths depended on strains loaded to FBG sensors. A CFRP beam-bending test was conducted to confirm the possibility of simultaneous measurement of both strain and AE signals from a single FBG sensor. In the test, signals from a conventional electric resistive strain gage and a piezoelectric AE sensor were revealed to be equivalent to those from the FBG sensor, respectively. The system will be applied to the development of composite structures in the aerospace field, such as Epsilon Launch Vehicle.

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