In this paper, we aim to clarify the effect of cutting direction on the cutting characteristics in the wedge indentation processing of polyethylene terephthalate (PET) film with mechanical anisotropic properties. In order to reveal the cutting characteristics due to difference in cutting direction, the cutting line force of a center bevel blade on the PET film was measured by setting the cutting direction to machine direction (MD) and cross direction (CD), and the cutting surface was observed. From the results, the cutting line force was shown that CD is higher than MD. There were three deformation modes of the cutting surface, and the occurrence frequency was different between CD and MD. In addition, a finite element method (FEM) analysis was carried out to compare the difference in cutting deformation and internal stress state due to cutting direction and lubrication state. It is clarified that the cutting deformation of the PET film is characterized by the tensile test based mechanical properties and the frictional coefficients with the wedge and underlay.

Utilization of scrap wood produced by thinning-out the Japanese larch forest is a serious problem to be solved. Since wood is comparatively easily strengthened by compressing it, compressed woods can be used as child toys. However, it has not been applied for construction timbers yet. On the other hand, the decay of wood damages the timber and it remarkably shortens the life of a wooden building.
In this study, the investigation was carried out to aim to apply compressed wood produced by compressive forming to wooden buildings. Concretely, bending strength, shear strength, bending creep property and bending fatigue property of the compressed wood were examined. The following conclusions were obtained. 1) There is an extremely strong correlation between the compression rate of compressed wood and the bending and shear strength. 2) The compressed wood has an advantage of lessen creep deformation. 3) The compressed wood is far superior to the uncompressed wood in terms of fatigue property. From the mentioned above, the effectiveness of the compressed wood is clarified to contribute to the improvement of resistance against earthquake.

The goal of this study is to locate sources of liquid-borne AE waves with multi-channel system being comprised of multi parabolic optical fiber sensors. At first, different frequency characteristics of each parabolic type sensor in water is provided by the shape of the sensor holder around which the optical fiber was wound. These parabolic type sensors have a high directivity with half width at half amplitude of less than 20 degrees. A multi-channel system was realized by setting these sensors on one optical fiber. A signal from the system is composed of the two waveforms detected by each sensor and can be allowed to separate those two waveforms with wavelet transform of the signal. The arrival time difference of those two waves agreed well with the theoretical prediction which can be calculated by the distance difference of the sensor to the source and velocity of the wave (1500 m/s). Now, we have been trying to detect liquid-borne AE from SCC in a sensitized SUS304 in polythionic acid solution.

Temperature dependence of ultrasonic properties such as velocity and attenuation has been evaluated quantitatively in the liquid and solid phases. A polygonal buffer rod that provides appropriate ultrasonic pulse-echo measurements with a high signal to noise ratio is employed. Polyimide is chosen as the rod material for measuring low-density polyethylene (LDPE) because such plastic material provides better acoustic impedance matching with LDPE. Ultrasonic pulse echo measurement with the buffer rod is performed for LDPE at temperatures up to 200 oC. Ultrasonic echoes reflected at the bottom of the LDPE are clearly observed even without any couplant between the rod end and LDPE. Temperature dependences of the ultrasonic velocity and attenuation of the LDPE are then obtained. Both the velocity and attenuation show a bending point at the solidification point of the LDPE.

The Sagnac interference type optical fiber sensor using a feedback control for polarization of incident light to improve stability of the system was developed and utilized for AE measurement under the high temperature environment. Ni plated on a commercial Cu-coated optical fiber was wound around a carbon steel pipe and measured AE caused by the fracture of the oxide film on the pipe in 700°C. The total number of AE with an optical fiber sensor was 8110 events and was as many as the AE event with PZT type sensors set on low temperature portion. The AE sources were located on an oxide film fracture area observed by eye-inspection. A coiled sensor with an optical fiber was also developed by a sandwiching with metal plates for measuring AE on a plate structure. The coiled sensor can also detect AE from oxide film fracture at high temperature.

In this paper, attenuation coefficients of the leaky T(0,1) mode guided wave propagating in piping buried in the petrolatum-type anticorrosion grease were measured as functions of pipe dimension and temperature. It was confirmed that the experimental results agreed well with the theoretically deduced attenuation coefficients. The theory of the leaky T(0,1) mode guided wave and experimental details were shown.

Resonant characteristics of the circumferential (C-) SH wave converted from the T(0,1) mode guided wave at an axial elongated notch defect was presented. First, it was shown that sorts of ringing signals were observed immediately after the defect signal in the RF time domain signals when the resonance occurred. Secondly, the standing wave of the converted C-SH wave was verified experimentally with the laser Doppler vibrometer and numerically with FEM simulation. It was confirmed that the resonances were occurred when the number of wavelengths took integer and half integer.

A new method for measuring liquid level using wedge wave was presented. This method is utilizing the difference of wedge wave velocity in the air and in the water. It is indicated that the liquid level is proportional to the elapsed time difference of the propagated wedge wave. Wedge wave velocities in the air were experimentally obtained as 1375 m/s for mode 1 and 2362 m/s for mode 2. It is considered that mode 1 is suitable for the measurement because of its slowness and clear signal. The liquid level sensing was carried out by laser ultrasonic method using aluminum 30° wedge in the water. The relationship between the liquid level and the elapsed time of the wedge wave showed high linearity. The standard deviation of data plots was 0.88 mm, the measurement resolution was 1.50 μm and the error rate was 1.04%. It is considered that this method has enough precision and high resolution for practical use.

There has been an increasing interest in wedge waves propagating along the tip of an ideal sharp elastic wedge because these waves are dispersionless, their propagation velocity is lower than the Rayleigh wave velocity and the acoustic energy is concentrated at the tip of the wedge. In this work, three dimensional finite element analysis method (FEM) has been applied to a sharp metal wedge to examine the generation and propagation of wedge waves. The material is aluminum and the wedge angle is thirty-degree. It has been shown in the numerical simulation that the velocity of the wedge wave estimated by the FEM almost agrees with the value determined from an empirical formula. It is also shown that two wedge waves in different modes are successfully reproduced in the simulation. Thus, it is demonstrated that the numerical simulation could be a useful tool to examine the generation and propagation of wedge waves.

The final goal of this study is to assess integrity of a corrugated fin type heat exchanger under pressure using acoustic emission (AE) technique. In this study, AE signals from the heat exchanger sample under pressurizing test to burst was monitored. As two type fractures, 1) inclusion fracture in an Al alloy and 2) fracture at fin and fillet of blazing part, are expected to occur in the sample, we tried to classify AE into the two fracture types with principal component analysis and convolutional neural network. The PCA was done with seven traditional AE features representing AE waveforms. The first and second components are mainly related to amplitude and frequency, receptivity. Two fracture types are roughly separated on first and second principal components. The Alex net which has pre-determined weights in the neural network was used in this study, a spectrogram of AE by short time Fourier transform was prepared as input data for CNN. A part of AE classified as inclusion fracture by PCA was assigned to a fin fracture with CNN. The reason of this different classification between two techniques is unclear.

The purpose of this study is to evaluate damages in a ball bearing with an acoustic emission technique. Many techniques for estimating bearing damages have been proposed ,and utilize vibration or acoustice emitting from a bearing in service. Acoustic emission technique methods is expected to detect the damage in early stage because the technique can detect high freqrency small vibration. However AE method can not identify the damage modes such as wear, flaking, and fatigue. In this studuy, identification of the damage mode on bearings in service with the AE waveform classfication was curried out with a self organization mapping (SOM) method which is one of neural networks. SOM migiht be classified the AE signals into three groups corresponding to each damage modes on the raceway obsereved with an optical microscope.

We developed a nondestructive measurement method of defect shapes (single crack or branched crack and inclination angle) existing on the surface of steel flat plate of uniform thickness by ultrasonic waves incident from the back surface. The change in reflection intensity (C scan image) due to the probe position was measured by the normal beam technique by single transducer operation with immersion testing. In this study, the defect shape is evaluated from the characteristics of interference fringes of reflected intensity. Asymmetrically branched defects and symmetrically branched defects are identified using the deviation from symmetry of interference fringes of reflection intensity and, the change rate of reflection intensity with probe position, indicating their effectiveness.

The transformation-induced stress relaxation (TISR) of TiNi shape memory alloy (SMA) tape under the stress-controlled or the strain-controlled subloop loading was investigated. The results obtained can be summarized as follows. The amount of TISR increases with increasing in the holding strain. The TISR finish stress level corresponds to the stress plateau obtained by the low constant strain rate. The amount of TISR increases in proportion to decreasing temperature during holding constant strain. Then the slope of liner line is 12.9 MPa/K.

The mechanical property of shape memory polymer (SMP) modeled by fused deposition modeling (FDM) 3D printer was experimentally investigated. A tensile test was conducted with a specimen modeled by a FDM 3D printer with ABS and SMP. A repeated tensile test was conducted in the high-temperature (T_g + 20 K) furnace. The experimental results are summarized as follows. The maximum stress depends on the modeling direction in tensile test. The maximum stress is high when the modeling direction is 0 degrees with respect to the tensile direction, and the maximum stress is low when the modeling direction is 90 degrees with respect to the tensile direction. The young's modulus of ABS specimens modeled by FDM 3D printer is higher than SMP. When the repeated stress is applied at a higher temperature than T_g, the residual strain increases with increase in number of cycle.

Magnetic Barkhausen noise (BHN) is compositional pulses generated due to the dynamic behavior of the magnetization process dependent on the microstructures in ferromagnetic material. Therefore, it is expected as non-destructive inspection system to evaluate stress variations and minute deformation of the structure in real time. The purpose of this research is to clarify the mechanism and the behavior of BHN generation utilizing iron based magnetostrictive alloy wire as fundamental study for application to Barkhausen noise stress sensor. Frequency characteristic evaluation by Fast Fourier transform (FFT) and Wavelet transform (WT) analysis of the obtained BHN waveform and its stress dependence were measured. As a result, it was revealed that BHN signals caused by the rotational magnetization of the magnetostriction occured in the saturation magnetization region and has mainly low frequency properties. Moreover, since BHN power at the range of frequency (300-10 kHz) has a good first order linearity (R² = 0.988) against the stress, it can be expected to be applied to a stress sensor with higher sensitivity and higher reliability than conventional magnetic methods.

Ferromagnetic materials that can exhibit large Joule magnetostriction in low magnetic fields are of interest for use as sensors and actuators. Among them, the magnetostrictive alloys can be utilized as stress sensor as well as vibration energy harvesting device under cyclic loading. This paper describes first about new magnetostrictive alloys development of polycrystalline FeGa and Co-rich FeCo alloys by novel processing techniques as well as their materials properties. Next, their applications for electromagnetic smart stress sensor and wireless IoT (internet of things) device with micro-energy harvesting function are discussed. In consequence, we have successfully developed a simple-structured inverse magnetostrictive ring-type torque sensor model in handle part of an electric vehicle (EV) system as well as robot motion control for automatic operation system. Next, the development of vibration micro-energy harvesting device which utilizes the “inverse magnetostrictive phenomenon under alternative vibration where small leakage of a flux associated with the magnetic domain movement is introduced. Beside, the technical problems for developing smart stress-sensor and micro-energy harvesting devices are discussed.

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 changes the direction of movement of train. When the fault caused to the machine, it may cause long time closure of traffic. Therefore, the automatic early detection or identification system is important for early recovery. Then in this research, probabilistic fault identification method using Bayesian estimation is proposed. To the proposed method, torque value of electric point machine is used for diagnosis. Torque value of operation varies with the temperature. This change of torque value causes misdiagnosis. In this study, evaluation of the effect of the temperature to the diagnostic accuracy is conducted and the method to decrease the effect of the temperature is proposed.

In the present study, a sensing layer using built-in Rayleigh scattering-based distributed fiber-optic sensor has been developed for structural health monitoring. The sensor was embedded into a non-crimp fabric (NCF). Two types of FRP specimens, which were made of only NCF layers or NCF/plain-woven fabrics, were manufactured. Tensile tests were conducted while strain distribution being measured. From the test results, it was found that the sensing layer of NCF/Plain structure could measure local strain distribution generated by the /plain-woven structure. Next, strain concentration around holes was measured by the attached sensor. From the resulats, it appeared that the sensor could detect holes whose diameters were from 1mm to 1cm. Additionaly, it was found that the multiple holes with 2mm intervals could be identified by our method.

In this paper, distributed fiber-optic sensors with fiber Bragg gratings (FBGs) have been used to measure strain and temperature distributions of an aluminum plate. In order to reconstruct the strain field of 18 quadrilateral elements on the plate, a new way of sensor layout is proposed based on the principle of strain rosette and the flexibility of optical fibers. Afterwards a stress-free optic fiber sensor has been installed in a silicone tube on the plate aiming to achieve temperature compensation. In this study, the plate is simply supported and subjected to loads perpendicular to the plate surface while temperature loads are applied with aid of belt heaters. Results show this method is of high accuracy for strain reconstruction. As for temperature measurement, the results are analyzed and discussed.

This research is about the life prediction method of the caneileder structure by the acceleration measurement. Occurrence of the fatigue failure can be evaluated from local stress by cumulative damage rule. Strain gage is generally used for measure the stress, but the distributed measurement is difficult and the life of the gage is limited because of the weatherability. Therefore, in this research, we propose to predict local stress of cantilever structure for acceleration measurement. And verification of the validity of the method and a limit is performed. Furthermore, the error of fatigue life of prediction is examined.

The purpose of this study is to investigate the mechanical properties, cracks behaviors and the effect of matrix cracking on the mechanical properties of angle-ply FRP laminates. Three types of materials were tested for this purpose: 1. CFRP (T700SC/2592, Torayca), 2. CFRP (T700SC/2500, Torayca), 3. GFRP (GE352G135SB). FRP laminates with laminated structures of [θm⁽²⁾/θn⁽¹⁾]s are monotonically loaded to obtain its mechanical properties. In order to obtain more cracks on specimen, notches were made at the edges of some specimens to create artificial cracks before tested by tensile test machine. Cyclic loading tensile test were also done at certain stress points after inlinearity started to form. As the laminates are loaded and unloaded back to 0 MPa, strain became non-zero due to the existence of residual strain, where laminates are plastically deformed. Cracks observation for CFRP laminates was done by using X-ray machine while for GFRP laminates, due to its semi-transparent properties, cracks formation can be viewed in real time by using DSLR camera. The experimental results of stiffness reduction and crack density relationship agreed well to analytical results. Understanding the damage behavior in cross-ply and angle-ply laminates is important so that damage behavior and its effects in laminates with more complex configuration such as quasi-isotropic laminates can be predicted.

In this study, interfacial shear strength (IFSS) of carbon fiber reinforced thermoplastic (CFRTP), which is composed of carbon fiber and thermoplastic polymer alloy of polypropylene (PP) and polyamide (PA), is investigated by fragmentation test. The IFSS between PP/PA polymer alloy and surface modified carbon fiber with different surface oxygen concentrations is influenced by PP/PA content rate in PP/PA polymer alloy matrix. We conclude that surface modification of carbon fiber with hydrophilic groups can increase IFSS of carbon fiber and polymer alloy with higher PA content due to hydrogen bonding. On the other hand, we recognize that there is the optimum surface condition on carbon fiber in terms of IFSS according to the PA content of PP/PA polymer alloy when the surface of carbon fiber is not oxidized so much. It is suggested that moderate surface modification is effective to improve the IFSS between carbon fiber and PP/PA polymer alloy.

The corrosion-resistant light-weight faster was developed using carbon fiber reinforced thermoplastic (CFRTP) and glass fiber reinforced thermoplastic (GFRTP). Two commingled yarns were made using carbon fiber and PA66 fiber (CF/PA66 yarn), and glass fiber and PA66 fiber (GF/PA66 yarn), respectively. A braided yarn was made using the commingled yarns, in which GF/PA66 yarns were wrapped on the central CF/PA66 yarns. Then, the braided yarn was consolidated by pultrusion method to form rivet after cutting into appropriate length. Quasi-isotropic carbon fiber reinforced thermoset plastic (CFRP) laminates were joined by the rivet by hot press molding method. Tensile tests of the joined CFRP laminate were performed. The joint strength increased with increase of fiber volume fraction of the rivet. The experimental results showed that replacement of metal faster by the rivet could reduce weight of joint.

The influence of long-term seawater immersion on the mechanical properties of plain woven CFRP laminates was evaluated by static tensile and tension fatigue tests. These tests were carried out on the CFRP immersed different time under seawater: 2566 hours and 4967 hours. The mechanical properties of the specimen for 2566 hours immersion decreased drastically; the tensile strength, the elastic modules and the fatigue strength at 10⁶ cycles reduced by 21.3%, 12.3% and 30.7% compared with those of no immersion specimen, respectively. On the other hand, after 4967 hours immersion, it was found that the mechanical properties decreased slightly. From observation of the Scanning Electron Microscopy (SEM), it was clear that morphology of the fiber/matrix interface varied with the immersion time. However, there was a small difference on the interface fracture surface between 2566 hours and 4967 hours. These results indicated that degradation of the fiber/matrix interface progressed dramatically by 2566 hours, and after that, interface degradation gradually converged. Damage growth behavior under fatigue loadings was investigated by non-destructive inspections using soft X-ray photography and ultrasonic inspection. At first, matrix cracks occurred along 90° and ±45° fiber directions. After that, delamination occurred originating from the matrix crack. Then, these damages expanded as the number of cycles increased, and finally, the specimen broke as the longitudinal fiber in the 0°/90° layers damaged.

Bending property of a woven carbon fiber reinforced polyamide composite was studied. From the three point bending test at elevated temperature, it was shown that the flexural modulus started to decrease at 60 °C. The glass transition temperature of the polyamide was found to be 64 °C by differential scanning calorimetry, which was almost corresponded to the reduction of bending modulus. Then, bending creep test was performed at various elevated temperatures to obtain creep compliance curves. The smooth creep compliance master curve could be obtained by shifting each creep compliance curve. It was shown that Arrhenius type time-temperature superposition principle was effective for the woven carbon fiber reinforced polyamide composite. Long-term bending creep deformation could be predicted by accelerated tests at elevated temperature.

This study aims to develop the resistance welding method for continuous fiber reinforced thermoplastic (cFRTP) composites using Woven-CF 0/90° as resistance heating element. The material for the experiment was woven CF/PPS laminates. The effects of processing conditions such as applied current, time and pressure, and also material conditions such as thickness of the inserted PPS films on the fusion behavior of cFRTP composites were investigated to get the optimum condition for electro-fusion joining. The contents for evaluation were surface condition of joint section peeled off after applying current and welding area obtained from those images. The experimental results revealed that electro-fusion behavior was influenced significantly by thickness of PPS films and electric resistivity of cFRTP laminates. From the result of the single lap shear strength (LSS) test, it was revealed that the LSS value of using Woven-CF 0/90° heating element was achieved over 24MPa.

Poly(lactic acid) (PLA) attracts much attention as a material of bone fixation device which is used for fracture treatment, because it degrades to nontoxic lactic acid through non-enzymatic hydrolytic degradation. However, the material has drawbacks, such as lower elastic modulus and no osteoconductivity. Therefore, a composite material of poly(lactic acid) (PLA) and bioactive ceramics powder which has higher stiffness and osteoconductivity has been investigated. Composite bone fixation device with hydroxyapatite (HA) which is a main inorganic constituent of bone has been developed. However, degradation rate of HA/PLA composite is too low. It was reported that this composite remained for 5 years in vivo. In addition, the strength in composite material of polymers and ceramics decreased by stress concentration around ceramic particles. In this study, PLA was compounded to β-tricalcium phosphate (β-TCP) and β-TCP/PLA composite was drawn to improve the strength. Past studies about self-reinforcing by drawing has been conducted to polymer. In the present study, effect of ceramic particles on mechanical properties and higher order structure of β-TCP/PLA composite was investigated. Screw was focused as the most general bone fixation device and formed from drawn β-TCP/PLA composites. The shear strength and orientation function were measured as mechanical properties and higher order structure, respectively.

Induction Heating (IH) is one of the heating methods for materials and molds. Induction heating has advantages such as higher thermal efficiency than other heating methods. Therefore, it is desirable that it is also utilized for FRTP forming. Though household IH cookers are inexpensive, they have the possibility of applying to the FRTP forming. In this study, to examine the heating characteristics of the IH cooker, heating experiments were conducted using a steel plate. It was confirmed that the steel plate can be heated up to 250 °C. Furthermore, fabrication of FRTP pipe using the co-woven braid composed of polyamide and carbon fiber by the internal pressure molding method was carried out. From the experimental results, it is confirmed that fabrication of FRTP pipes using the household IH cooker is available.

This study aimed to predict the optimum processing condition for thermoplastic tape laying such as flat laminates and pipe molding. The material used for the experiment was unidirectional carbon fiber reinforced polyamide 6 prepreg tape. The effects of processing conditions such as lamination number, tension of prepreg tape, feed speed of prepreg tape and pressure of compaction roller on the laying behavior of prepreg tape were investigated. The thickness of the molding parts was measured by micrometer. The cross-section images was obtained by microscopic observation. It was revealed that the tension of prepreg tape affected the quality of the molding part remarkably.

Preparation of carbon fiber reinforced in situ thermoplastic epoxy resin laminate (CF/T-Ep) by wet compression molding and investigated the mechanical properties by using three-point bending tests for various kinds of molding conditions. The bending strength and bending modulus of CF/T-Ep at 7.2 MPa was the highest within all the specimens tested.

This study focuses on thermoplastic resin impregnation behavior in carbon fiber reinforced thermoplastic polyimide (CFRTP). The objective of the present study is to clarify the relationship between molding conditions and resin impregnation to fiber bundle and the effect of resin impregnation on the mechanical properties of the composites. Specimens were prepared using micro-braiding, film stacking and powder methods. The analytical prediction for resin impregnation showed a good agreement with the impregnation ratio experimentally-obtained. In addition, the void content inside the fiber bundle could be drastically reduced by pressurized cooling.