We estimate effects of ply thickness in mechanical properties and damage evolution of CFRP angle-ply laminates under various tensile loading. It should be noted that the laminate thickness is almost the same, but the ply thickness are quite different. Monotonic tensile tests , cyclic loading-unloading tensile tests and stress relaxation tensile tests are performed on [(±θ)₁₂]_s (t-0.05prepreg×48plies)，[(±θ)₄]_s (t-0.15prepreg×16plies) and [(+θ)₄/(-θ)₄]_s （t-0.15prepreg×16plies） T700SC/2500 carbon/epoxy laminates with various fiber directions (θ=30, 40, 45, 50 and 67.5°). Ply thickness is expressed as t-0.05, t-0.15 and t-0.6, respectively. Damage evolution can be determined by cyclic loading-unloading tests. We use mesoscale damage model to investigate damage evolution in CFRP laminates. We discuss effect of ply thickness on mechanical property of angle-ply laminates. Laminates have thin ply thickness showed high strength and fracture strain.

Tensile strength properties in the transverse direction of carbon fiber reinforced thermoplastic (CFRTP) laminates with in situ polymerizable phenoxy resin were evaluated. The unidirectional [90]14 laminates were formed using the prepreg, NS-TEPreg. By changing the conditions of fabricating CFRTP laminates, the void content in the laminates and the degree of polymerization of the matrix resin were varied. As the results of tensile tests and image analysis, it was revealed that when the void content inside the laminates is 0.5% or less, the influence of the void on tensile strength properties becomes limited. Also, as the results of measuring the average molecular weight of CFRTP laminates, it became clear that the transverse tensile strength σbT and transverse failure strain εbT increase as the average molecular weight of the matrix resin increases.

Various kinds of underwater exploration techniques have been developed. For instance, submersible research vehicles and autonomous underwater vehicle (AUV) have been used for observation of underwater conditions, in addition to the technique of fixed-point observation. However, such research vehicles and conventional AUV are difficult to control, are expensive, and are usually made with non-biodegradable materials such as metals. In contrast, jellyfish is the most efficient swimmers, traveling for long distance with saving energy by drifting in the ocean, its body can be decomposed after death, and safe for surrounding creatures. Therefore, we are developing the jellyfish-mimic AUV using a hydrogel. For designing a Jellyfish-mimic AUV robot, it is preferable to introduce a soft actuator driven by water pressure, as it requires low electric power and it is eco-friendly. In this study, we prototyped a Jellyfish-AUV robot using a soft material and a soft actuator. While it is ideal to make a robot body with hydrogel it is difficult to make the actuator with hydrogel.

The 3D gel printer Soft and Wet Industrial Materials・Easy Realizer (SWIM-ER) in our laboratory can only perform modeling with monochrome, so in this study we evaluated the physical properties of the color gel used in the full color 3D gel printer. In addition, it was possible to prepare color gels of various colors by mixing a plurality of color gel solutions using an automatic dispensing robot "Andrew". By this study, it was found that the addition of the surfactant dispersed the pigment and the fracture from the aggregated part was also improved. It was found that increasing the concentration of pigment decreased the brightness and increased the saturation. It was found that the concentration of pigment and the value of brightness are linear relationship, and also the concentration of pigment and the value of saturation are linear relationship, too. The neutral color gels got by mixing two pigments. In addition, although it was possible to prepare a color gel pallet using Andrew, it is necessary to study the stirring and removal method of microtubes after dispensing in the future. If we can obtain some sample data of color gel, we would like to construct 3D gel printer system. After that, we plan to develop the main body of the device. Particularly because nozzles etc. need to be devised, it seems necessary to devise a concept more carefully.

Since 2012, electric arc furnace steel sheet for automotive structure have been manufactured in factory scale. Practical use of the steel sheet is under consideration. In order to accelerate this action, three kinds of empirical formulae for spot-welded joint strengths for blast furnace steel were tried to their compatibility for the joint strengths for the electric arc furnace steel. The formulae were recommended by Oikawa et al. with their experimental results for many kinds of blast furnace steel sheets. In this study, quasi-static experimental strengths (Tensile Shear Strength and Cross Tension Strength) for 980 MPa and 1180 MPa grade electric arc furnace steel sheets are plotted in their TSS - tensile strength, CTS - C equivalent and CTS/TSS - C equivalent relationships. The plots fit very well with their experimental results.

In recent years, the application of high strength steel sheets has been expanding in the automotive field in order to increase the strength of the automobile body. Moreover, the tensile shear strength and the cross tension strength are defined by JIS as the strength method of the resistance spot-welded joint. Recently, L-type tension strength which is the strength in the peeling direction assuming the actual structure is receiving increased attention. However, it is known that L-type tension strength decreases with increasing steel sheet strength. In this study, the effect of softened nugget on joint strength was investigated for the purpose of improving joint strength of L-type joints. Thus, nickel was added to the nugget and the nugget microstructure was controlled to achieve a nugget softening. As a result, nugget microstructure changed and softened by adding nickel. Then, the L-type tension strength was improved under the condition where the nugget hardness was greatly decreased. In order to investigate the mechanism of improving the joint strength, the test was stopped at an arbitrary load during the test, and the crack growth measurement at the nugget end was performed. It can be confirmed that cracks did not progress in the nugget as the nugget softens. It is considered that crack growth in the nugget is suppressed as the deformability by softening was improved. Therefore, it is considered that the L-type tension strength is improved by improving the deformability of the nugget.

Recently, high-strength steel sheets have been used to automotive structural components to reduce the body weight and improve the passive safety. Resistance spot welding is used as method in jointing steel sheets. However, there is a problem that cross tension strength which is an index of the joint strength decreases with improving the base metal strength. Therefore, to solve the problem, it is effort to make the weld characteristics control and improve the joint strength. However, there are few researches of shape factors considered. In this study, focusing on the weld shape, the effects of weld shape on the joint strength of resistance spot welded high-strength steel sheets were investigated by experiment and numerical analysis. First, to investigate whether the weld shape effects the joint strength, cross tension test was carried out on joint which changed weld shape. As the result, the strength was improved by changing the weld shape. Base on this experimental result, the effects of the weld shape on the stress and strain distribution was investigated by numerical analysis. As the result, the stress of thickness direction at the vicinity of the edge of nugget and the stress intensity factor decreased by changing weld shape. It is considered that these decreases are caused by changing the weld shape and increasing the amount of deformation of weld joint. From the above, it became clear that by changing the weld shape of the resistance spot welded joint, the deformability increases, and the joint strength improves.

In this study, welded plates of carbon fiber reinforced thermoplastics (CFRTP) and metals with surface treatments were evaluated to jointing characteristics. We tested single-lap shear strength of joining and studied the influence of pressing temperature and surface treatments on joining strength. In addition, to clarify failure mechanism, the fracture surface observed by scanning electronic microscopy (SEM) and the molecular weight of matrix near the joining interface measured by gel permeation chromatography (GPC).

Clamp force losses of bolted joints in service often cause serious accidents. Therefore it is very important to check the clamp force at maintenance. In our previous study, a method to easily detect the clamp force was developed. The method can detect the clamp force within error of ±10%. In this study, we have achieved FE analysis for the bolted joint which clamp force is being detected in order to reduce the detection error. As the result of FE analysis, it was seen that the detection accuracy can be improved by means of reviewing the detectional condition.

Thin structures such as frameworks of automobiles are composed of thin plates and have bolted joints in which their members are joined by bolts and nuts. The clamping force of the bolted joints can be estimated from the elongation of the bolt axis measured by the strain gauge or the ultrasonic. However, the bolt axis in the thin structures is often too short to be measured, and that makes the estimation accuracy low. The previous studies have reported that the stiffness reduction of the interfaces of the bolted joints is induced by the clamping force of the bolts and nuts, and the natural frequency of the structures is varied by the clamping force. This study has investigated the natural frequency against the clamping force of the bolted joints in the thin structures and proposed the method to improve the sensitivity of the natural frequency for the identification of the clamping force by using the finite element method with the interfacial elements. From the calculation results, the interfaces of the joined members mainly affected the natural frequency. The thinner members made the lower variation of the natural frequency against the clamping force. The variation of the natural frequency could be increased by supporting the part of the joined members. It was effective for the identification of the clamping force to apply the supporting points when the interfaces of the joined members strongly affect the natural frequency.

In general, in order to improve the performance of a thermoelectric device, it is to use a material having high thermoelectromotive force, low thermal conductivity and low internal resistance.However, since the accordion type thermoelectric power generation module using nickel and aluminum material developed has low thermoelectromotive force (Seebeck effect) and high thermal conductivity, it is disadvantageous as a thermoelectric power generation module.Since the structure itself of the accordion structure has a high heat radiation effect, it is possible to create a large temperature difference without using a cooling device.

It is very important to measure the deformation of the structural parts of the large constructions for the health monitoring or damage evaluation of the public constructions. The Moiré methods are measurement methods of the deformation using moiré phenomena which can be observed when two grids were overlapped. In this study, a new moiré method to measure the crack width of the concrete structural materials has been developed.The crack width of concrete specimens with model grid during splitting tensile test was measured by this method.

Plastic deformation behavior of ring-shaped aluminum workpiece is investigated in axial compression with one-way torsional moment at room temperature. One-way rotation with a maximum angular speed of 0.5 rpm around a compression axis is simultaneously applied with an axial compression speed of 0.1 mm/s. The ring workpiece is plastically deformed in the outer diameter direction especially at the end surfaces of the ring workpiece by applying one-way torsional moment. As the result, the barreling of the ring workpiece is reduced. According to experimental and finite element simulation results, it is confirmed that the superposition of the torsion moment has potential to control the plastic deformation of the workpiece.