Cold spray is a relatively new coating technology with high productivity, environmental friendliness and low process temperature, in which the solid particle are accelerated and finally impact on to the surface of the substrate. Through the deformation and the combination of the materials, a coating layer was formed. In this study, optimization of substrate roughness by laser pre-treatment for enhancing the deposition efficiency in cold spray is performed. Materials used here is Cu particle and SUS304 substrate as an impact pair. Finite Element Analysis (FEA) and Smoothed Particle Hydrodynamic (SPH) model was employed to simulate the models in relation with constant powder size (20 μm), for estimating impact interface parameters. Experimentally, particles are deposited on the surface with different surface groove characteristics to compare the simulation results. Microstructures and deposition efficiency were obtained for the coatings. On the basis of the simulation and experiment, optimum substrate roughness for different impact pairs will be suggested for better coating.

The voltage measurements were conducted for a kW class cascade plasma torch with an external magnetic field. Pure argon was used as working gas at atmospheric pressure. To study the voltage-current characteristics of the plasma torch, the operating current and the anode-cathode distance were changed from 40 A to 100 A and 0 mm to 10 mm, respectively. The external magnetic field was applied by a permanent magnet with the maximum strength of about 0.39 T, generating about 0.27 T on the center axis of the plasma torch. The results show that applying the external magnetic field and separating the anode-cathode distance tend to increase the time-averaged voltage for each operating condition. With the external magnetic field, the amplitude of the voltage fluctuation is reduced under certain conditions where the power spectra of the arc voltage show a peak around 2 kHz. This peak is attributed to the arc rotational movement.

A finite element analysis code was developed to accurately predict stress and damage fields in thermal barrier coatings (TBCs) systems subjected to thermo-mechanical fatigue loadings (TMF loadings). A modified inelastic constitutive equation for the TBCs and a Chaboche-type viscoplastic constitutive equation for Ni-based super alloy (IN738LC) were installed to simulate high temperature creep and cyclic deformation. In addition, an alternative algorithm for simulating fatigue crack propagation based on a damage parameter was developed. In this report, analyses of the TBC/IN738LC system subjected to in-phase and out-of-phase TMF loadings which has been often used to investigate the damage mechanism of TBC were performed using the developed analysis code. The results confirmed that stress and damage distribution in the TBC/IN738LC system can be appropriately simulated. From the analysis results, it was found that crack initiates at the top coat surface and propagates for the top coat/bond coat interface in the in-phase loading analysis. On the other hand, crack initiates and propagates along the top coat/bond coat in the out-of-phase analysis.

Using a crystal plasticity finite element (CPFE) method, uniaxial tensile analysis of a polycrystalline α-Ti was numerically simulated with the several sets of critical resolved shear stress (CRSS), and the changes in the activity of slip systems were investigated. The geometrical model for the analysis was built from crystal orientation maps of a pure titanium with RD-split texture, which were obtained with electron back-scatter diffraction patterns (EBSD). The results showed that the activity of a slip system and strain decrease with increase of CRSS for the slip system in certain regions, and it results in increasing the activity of other slip systems and strain in the other regions; that is, the activity of slip systems and strains have the relationship of a trade-off among the regions depending on CRSS.

The forming-limit strains of perforated steel sheets with circular holes were theoretically and experimentally estimated for two types of hole arrangements: square and triangular patterns. The theoretical forming-limit curves were obtained by finite-element analyses on a unit module of the perforated sheets using two different approaches. Hill’s quadratic anisotropic yield function was used. To determine the forming limits, the effect of strain gradient on the stretch flange deformation limit was considered, which was investigated by hole expansion tests. The experimental forming-limit strains were also obtained through Nakazima stretching tests. The theoretical predictability of the forming-limit curves was assessed by comparing the theoretical and experimental results.

A composite material containing nano-sized cellulose (or cellulose nanofiber: CNF) which is ecologically friendly and derived from abundant plants attracts much attention in material engineering. However, it is necessary to elucidate mechanical properties in the basic structure of cellulose, that is, CMF (cellulose micro-fibril) unit. Since actual fibrils of CNF take the form of aggregate comprising many elements and they are intertwined complicatedly, it is crucial to clarify transmission mechanism of force and deformation between fibrils. Therefore, in this study, we create a hierarchical structure model of multiplied CNF structures and simulate it using molecular dynamics method, especially as for torsional deformation. First, a hierarchical structure of CNF is generated by colliding two 5-layered crystalline CMFs. Next, in applying torsional deformation to one component of CMF, we observe how the local deformation transforms to the other. According to the stress-strain diagram obtained during torsional simulation, almost complete stress transmission is confirmed for very small strain, but, as the deformation increases, the hydrogen bonding between these CMFs is generally weakened and no stress transmission is done. The shape of CMF without torsional load spontaneously returns to its original one, which is already recognized as the behavior of superelasticity peculiar to CMF. It is also found that, between two CMFs, a torsional moment transforms into a bending moment.

Wiredrawing is one of plastic working methods, and it has been used in a wide range of engineering fields. Nowadays, the wiredrawing technique is reducing wire diameter down to nanometer scale and will be providing with high mechanical function. So, understanding microscopic phenomenon of metallic materials and the mechanism inside the wire becomes more important. The main purpose of this research is to evaluate behavior of dislocation density when nano-sized wiredrawing of single crystal is performed with the change of crystal orientation and temperature. The authors use molecular dynamics (MD) which reproduces atomic structure and observe the dislocation behavior inside wire during drawing process. Wiredrawing condition is applied to iron single crystal (α-Fe) with many-body (FS) potential. In actual processing, the wire material is exposed to high temperatures due to severe friction and such temperature rise will have large influence on the dislocation behavior. From simulated results, we found that, as the temperature is increased, the dislocation density of drawing in <100> or <110> direction shows a linear increase with increase of system temperature. In drawing in <111> directions, one long dislocation line occurs from the surface. But each dislocation does not collide inside. Therefore, dislocation density does not increase because one long dislocation disappears on the wire surface. As a conclusion of this study, nanowire models clarify the temperature dependence of dislocation density in the wire.

In this report, macroscopic elastic deformation properties of the four kinds of porous Thermal Barrier Coating (TBC) is investigated experimentally and analytically. First, the indentation tests were performed to obtain the loading and unloading-depth curves in various load levels, and secondarily Young's moduli were explored by using the unloading-depth curves, Hertz-contact theory and FEM analysis at several loading levels. It became clear that the obtained Young's moduli increase with increasing indentation load, which means that the obtained Young's modulus is an apparent modulus of the coating having some structural failure caused by indentation test. As the results, the real Young's moduli were determined at the very small load level with no structural failure for the four kinds of porous thermal barrier coatings.

This study proposes a new processing method by using the count rate of the acoustic emission (AE) signal. To analyze the AE count, deep learning which is a multilayered neural network is employed for a deep drawing process. In a press processing, a quality inspection is often carried out for each lot in a later process. When a failure once occurs in the process, a large number of defective products may occur due to the fast processing speed. In order to prevent this, it is important to immediately stop the processing just after the defect occurs. The AE signal data has been often used for monitoring the condition of process. However, it is easily affected by noise and lacks repeatability. Also it is difficult to handle the number of AE data due to its high frequencies of target signals. Therefore, the improvement of the data processing method and recognition rate is required and the deep learning approach is applied in this study.

For accurate evaluation of the reliability of electronic package, FEM analyses considering the creep deformation of solder joint in-situ should be conducted. It is well known that the indentation creep test has an advantage to evaluate the creep deformation in microscopic region although there are the problems. In case of the lead free solders generally used for the solder joint, the transient creep deformation should be measured by the indentation test. The transient creep strain occurs in the indentation process. Therefore, it needs to separate the strain into the elastic-plastic strain and the creep strain. In this paper, the method to obtain the stress-strain relation using the indentation test is proposed by using the numerical test. The stress-strain curve estimated by proposed method well coincides with the stress-strain curve of the nodal solution.

This paper shows a numerical solutions for infinite anisotropic medium containing two elliptical holes. Anisotropic body is uniformly subjected to in-plane or out-of-plane shear loadings at infinity, and is allowed coupling effect between in-plane problem and out-of-plane shear problem. Collocation method is used to derive the solution for the analytical model, and as the special case, stress intensity factor at the crack tip is also obtained by complex stress functions. Several numerical examples are given diagrammatically, and some of these examples are compared with existing result, which is assumed that the medium is behaved as isotropic or orthotropic material.

Highly Accelerated Limit Test (HALT) gives a product a severe loading which combines fast thermal change with mechanical vibration until the product fails, to identify its weak point in a short time. Since it takes a long time to evaluate the strength reliability of the solder joint in electronic equipment experimentally, HALT is expected to be employed for the evaluation. To achieve such an evaluation, the deformation and the fatigue behaviors of solder joints during HALT must be clarified by conducting some simplified test reflecting the essence of HALT. Then, the authors have conducted HALT simulation tests using a copper-solder joint specimen, in which the specimen is subjected to cyclic torsion with a superimposed tensile stress. The biaxial ratchetting strain was generated at the solder joint of the specimen in the test, and the ratchetting strain rate had a high correlation with the fatigue life of the solder joint. This means that the ratchetting strain rate will become an effective parameter for predicting the fatigue lives of solder joints in the HALT simulation tests. However, in the test, the solder joint is subjected to cyclic torsion at the same time, and therefore a parameter concerned with the cyclic loading is also needed for predicting the fatigue lives consistently. Then, we proposed a prediction method based on Miner's law, which considered the effect of both the ratchetting strain and the cyclic loading on the fatigue life of the solder joint. The validity of the proposed method was discussed using the fatigue test results.

Urethane rubber has high hardness and is often used when it is subjected to compressive load. However, rubber exhibits complex mechanical behavior and it is difficult to treat with the rubber property when rubber products are analyzed. Therefore, in this study, a compression test of urethane rubber was performed with different stroke rates. The experimental method was carried out according to JIS K 6254. The diameter of specimen was 29 mm, and the height was 12.5 mm. The specimen was compressed at a constant stroke rate until the stroke is 3.75 mm. Then it began to return the stroke to 0 mm at the same stroke rate. This procedure was repeated 4 times. And in consideration of hyperelasticity, viscoelasticity, Mullins effect, friction, appropriate material parameters were searched by using Nelder-Mead method. As a result of the analysis, there was a tendency that as the particular material parameter increased as the stroke rate increased, but the associated material parameter decreased. And as for the viscoelasticity parameter, as the stroke rate increased, the delay time changed significantly.

Acrylic sheet material has superior properties such as high transparency, low specific density, shattered resistance. However, it is limited to predict its deformation and cracking behavior due to the randomly broken of fragile material. There are almost not any research works which clarified a cracking behavior of a fragile worksheet subjected to a shearing-tool indentation. In this work, cracking behavior of AC in Iosipescu shear test will be numerical and experimental.

This research was aiming to compare shearing characteristics of Polystyrene (PS) square bars that subjected to indentation of a symmetry (42°) blade and mounted on Al5051 plate underlay with bars that subjected to indentation of a symmetry (42°) and mounted on Al5051 anvil. In order to compare load resistant from cutting process, stroke of breakage and deformation of Polystyrene bar, the cutting velocity was varied ranging from 5 to 65 mm/min. The result revealed that the maximum load resistant for cutting in case of use Al5051 anvil is lower than use Al counter plate and both was found that increase related to cutting velocity. While, both process have the same indentation displacement for bars breakage. Moreover, the deformation of PS bars when using anvil in cutting process depend on cutting velocity remarkably.

In recent years, by a technological advance and a downsizing of the mobile device, increase of the heat value becomes the problem. Therefore, as one of the cooling methods, a method using the latent heat of phase change material (PCM) attracts attention. The composite between polyethylene having workability and PCM having heat storage property is manufactured. However, clarification of the mechanical properties of the composite is not enough. Therefore, in this study, the mechanical properties, in particular heat storage property, tensile strength and hardness are evaluated experimentally. Results are obtained as follows; The composites have heat storage properties in the melting point of the PCM. It is found that tensile strength, micro Vickers hardness and strain amount decrease with increasing MPCM weight content of the composite regardless of the type of MPCM. It is suggested that tensile strength and micro Vickers hardness are correlated with MPCMs, and tensile strength can be predicted from hardness. Compared with the polyethylene matrix, it becomes clear that the composite material is a brittle material.

Flake graphite cast iron has been widely applied to structural members of automobiles because it is possible to produce members with complicated shape by low cost. It has been reported that the cooling rate varies in locally depending on the shape and thickness of the casting member, therefore result in that shape, size and distribution of graphite, moreover microstructure of the matrix changes and affects the mechanical properties. However, it has not been studied yet influence of each factor on fatigue strength characteristics. In this study, fatigue strength test was carried out in flake graphite cast irons produced with different cooling rate to investigate influence of cooling rate on fatigue strength characteristics. Fatigue strength tests were also conducted in flake graphite cast iron having the same size and distribution of graphite but having different matrix to study influence of the matrix on the fatigue strength characteristics.

Diamond-particle-dispersed-copper (Cu) matrix composites were fabricated by spark plasma sintering (SPS) process from the mixture of diamond particles, pure-Cu and chromium (Cr) powders. The microstructures and the thermal conductivities of the composites fabricated were examined. These composites were all well consolidated at a temperature of 1173K for 600s by SPS process. No reaction at the interface between the diamond particle and the Cu matrix was observed by scanning electron microscopy and X-ray diffraction analysis for the composites fabricated under the sintering conditions employed in the present study. The relative packing density of the diamond particle dispersed Cu matrix composites with Cr addition was 4.4~5.9% higher than that without Cr addition. The thermal conductivity of the Cu/diamond composite drastically increased with Cr addition. The thermal conductivity of (Cu-Cr)-50 vol% diamond composites was 518~584 W/mK in a volume fraction range of Cr between 2.5 and 8.6 vol% in Cu matrix. Numerous transgranular fractures of diamond particles were observed on the bending fracture surface of diamond particle dispersed Cu matrix composites with Cr addition, indicating strong bonding between the diamond particle and the Cu matrix in the composite.

In this study, a repetitive unidirectional friction experiment was conducted on uniaxially compressed sample of metal powder in order to clarify the behavior of solid-state bonding on metal powder particles by simultaneous application of compressive and shearing force. Pure Cu powder was compressed under the normal stress of 1000 MPa to get uniaxially compressed sample with the target size of 20×20×0.25 mm³. The relationship between a normal load, a number of sliding cycles, and microstructural changes of samples after the unidirectional friction experiment was investigated by observing sample structures of fracture surfaces and cross-sections. As the results, it was found that the applied stress is more dominant in the particle bonding than the strain. In addition, it was suggested that the bonding of powder particles is proceeded as this order: (1) plastic deformation of particles; (2) grain refinement to a size of several micro-meter; (3) bonding of particles; (4) additional grain refinement to submicron size.

Ti-Ni shape memory alloy (SMA) system is well known as a functional material which shows the shape memory effect and superelasticity. It is reported that the tape-shaped Ti-Ni SMA shows the negative stiffness during post-buckling deformation, the tape-shaped Ti-Ni SMA is expected to be an effective vibration isolator for small devices. On the oyher hands, the tape-shaped Ti-Ni SMA does not show the negative stiffness during post-buckling deformation depending on \ the variation of heat-treatment and a environmental temperature condition. Then, in this study, the effect of heat-treatment temperature on the post-buckling behavior of the tape-shaped Ti-Ni shape memory alloy is investigated. The chemical composition of alloy used in this study is Ti-50.2at%Ni. The specimen is a liner tape-shaped 0.45mm in thickness, 7.0mm in width and 30mm in length. The sample is memorized to have a liner shape by heat-treatment. The heat-treatment temperature is varied from 573K to 723K for 3.6ks. The mechanical properties and buckling characteristic of heat-treated specimens are measured by the tensile-test and buckling-test at a constant temperature varide from 303K to 323K. Results of the experiments, it is clear that the tape-shaped Ti-Ni specimen shows negative stiffness during post-buckling deformation at the temperature around the Af temperature.

An actuator using the shape memory polymer (SMP) formed by fused deposition modeling (FDM) 3D printer was devised. The behavior of this SMP actuator was experimentally estimated in heating and cooling process. The results obtained can be summarized as follows. (1) The thicker the SMP actuator, the larger the force is. The thicker the SMP actuator, the larger the radius of curvature is. (2) The bidirectional SMP actuator shows repetitive behavior except the 1st cycle. (3) The SMP actuator can be expected as a bidirectional actuator made by FDM 3D printer.

The purpose of this study is to identify the fault from the sensor outputs of electric point machine using Bayesian estimation. The electric point machine is equipment which changes the direction of the movement of train. When the fault caused to the machine, it may cause long time closure of traffic and it is costly in recovery work . Therefore, it needs that the automatic early detection and identification system for early recovery. Then in this research, probabilistic fault identification method using Bayesian estimation is proposed. Strain of a certain rod at the time of switching is measured and the deviation rate of the strain from normal condition is used as diagnostic parameter. In this study, diagnostic accuracy of the method is clarified and method for improvement is considered. As a result, diagnosis by the proposed method is possible. Further, by diagnosing the time zone in which the amount of deviation is large, the detection accuracy for a minimum fault is improved.

In the present study, feasibility studies of process and health monitoring of FRP by Rayleigh-scattering based distribution optical fiber sensors were conducted. In the process monitoring, flow front of resin impregnation and process-induced strain were measured. Comparing to visual observation results, it appeared that the minimum peak of the strain curves shows arrival of flow front of resin. From the strain curves after start of heating process, the sensor could measure thermal strain., curing shrinkage and thermal shrinkage. In the health monitoring, damage identification of cross-ply GFRP laminates with delamination by the attached distribution optical fiber sensors was carried on. Figure 3 illustrates GFRP laminates with delamination for three points bending tests. The number of layers was 11 and the stacking sequence was [0/90/0/…/0]. Three types of specimens, no delamination, delamination between 5 and 6 layers and delamination between 10 and 11 layers were prepared. The distribution sensor was attached on the bottom surface. Therefore, it can be concluded that the Rayleigh-scattering based sensors could monitor impregnation and distribution of process-induced strain during molding process and development of delamination in operation.

This study demonstrates the applicability of tilted-Fiber Bragg Grating (TFBG) optical fiber sensor on structural health monitoring (SHM) of CFRP structures. The simultaneous measurement of axial strain and curvature were attempted utilizing transmission spectra of a TFBG sensor. The response of a TFBG transmission spectrum to axial strain and curvature was investigated independently by a tensile test and winding the sensor around a cylinder. As a result, strain caused wavelength shift and curvature decreased the amplitude of the cladding mode resonance in the transmission spectrum. Three-point bending test was conducted to apply both axial strain and curvature to a TFBG sensor simultaneously. The result shows axial strain can be measured using wavelength shift. On the other hand, the power of the cladding mode resonance was increased with curvature increasing, which was a tendency different from the result when applying only curvature. The result indicated that a TFBG transmission spectrum shows different response under small curvature (< 3 m^-1).

Based on the high performance of newly developed magnetostrictive FeCo71at% alloy (2011), we have developed two types of smart stress sensor devices, i.e. 1) stress/strain sensor for the machinery and infrastructure by measuring Barkhausen noise using FeCo fine wire, and 2) torque-sensor by measuring the leakage magnetic flux from the edge of magnetostrictive FeCo ring attached on the rotational shaft. The developed torque-sensor unit was applied to electric motor assisted system of spin-bike. These sensor application technologies will be enhanced by combining IoT wireless sensor net-work for Industry 4.0 or Society 5.0 in the near future.

Recently, various joining materials have been developed for a power semiconductor device structure. However, there are many materials which have difficulty in evaluation of fatigue property by conventional experimental methods. As a result, it is difficult to select an appropriate joining material in a design process of a semiconductor structure. In this report, we developed a new experimental method that can evaluate the fatigue properties of any joining materials. In developed method, firstly, two jointed members were connected by the joining material. Secondly, each jointed member was fixed to each jig to expand the dimensions. Thirdly, the specimen was subjected to two-sided four-point bending load. This method could examine a fatigue life of a thin joining layer which did not exist as a bulk material. Furthermore, it could examine the materials whose creep or ratchet deformation were remarkable. The high-speed examination was also possible to obtain high-cycle fatigue strengths. We examined the fatigue life of the joining layer made by Sn7Cu solder. As a result, the fatigue life measured by the proposed method followed the Coffin-Manson’s low with high accuracy.

The tailor welded blanks between aluminum (Al) alloy, A6061-T6, and stainless steel, SUS304, had been fabricated by a friction stir welding (FSW) technique. The FSW tool was offset to the Al side and the probe was inserted only into Al plate. Hardness and tensile tests of Al similar and Al/Steel dissimilar welds had been conducted. Hardness of softened area increased by post heat treatment. Tensile strength of the post-heat-treated dissimilar blank was about 8.5% higher than that of the blank without post heat treatment. The residual stresses were measured based on cos α method, revealing that the tensile stress was generated in the σ_xr and compressive stress was generated in the σ_yr.