Tadao Haraguchi

Wear and Friction Characteristics of AlN/Diamond-Like Carbon Hybrid Coatings on Aluminum Alloy

The use of diamond-like carbon (DLC) coatings has the potential to greatly improve the wear resistance and friction of aluminum alloys, but practical application has so far been limited by poor adhesion due to large difference in hardness and elasticity between the two materials. This study investigates the deposition of DLC onto an Al-alloy using an intermediate AlN layer with a graded hardness to create a hybrid coating. By controlling the hardness of the AlN film, it was found that the wear life of the DLC film could be improved 80-fold compared to a DLC film deposited directly onto Al-alloy. Furthermore, it was demonstrated through finite element simulation that creating a hardness gradient in the AlN intermediate layer reduces the distribution of stress in the DLC film, while also increasing the force of adhesion between the DLC and AlN layers. Given that both the DLC and AlN films were deposited using the same unbalanced magnetron sputtering method, this process is considered to represent a simple and effective means of improving the wear resistance of Al-alloy components commonly used within the aerospace and automotive industries.

Fuel Oxidization on Dimethyl-ether Fuel Cell Cathode

Cross leaked methanol in the cathode of a direct methanol fuel cell is completely oxidized, however, in the cathode of a dimethyl-ether (DME) fuel cell, the cross leaked DME is not oxidized and is exhausted from the cathode. The present paper reports that active DME oxidation such as methanol oxidation does not occur on the DME cathode until both the current density and cross leaked DME concentration exceed some upper limit. There is no cross leaked DME oxidation on a cathode under normal operating conditions, in which the current density is less than 0.2A/cm2, and the DME concentration is less than 1%. The cathode potential of the direct DME fuel cell does not decrease without active DME oxidation.

Influence of Loading Rate on Fatigue Crack Propagation Property of Recycled PA 66 Material at High-Temperature above Tg.

In this study, high temperature fatigue crack propagation test of the engineering plastic material was carried out in order to clarify the effect of loading rate on the fatigue crack propagation property at the high temperature environment above Tg. Then, failure mechanism and loading rate dependence were evaluated. (1) The resistance against the crack propagation at 30 Hz that was high loading rate was more excellent than that at 10 Hz and 3 Hz which was low-loading rate. And, the resistance against the crack propagation at 10 Hz was equivalent to that at 3 Hz. (2) The resistance against the crack propagation of R 1 material remarkably decreased in comparison with that of virgin material. However, the resistance against the crack propagation of R 3 material was almost equal to that of R 1 material. (3) From the fractography using SEM the fracture surface at high loading rate was a brritle form, and the effect by the fatigue was big. In the meantime, that at low loading rate was a ductile form, and it seemed to overlap fatigue and creep. The viscoelastic effect of the matrix seems to remarkably appear in the fracture surface at low loading rate. (4) It was proven that the process zone dimension and the reinforced fiber length influenced the difference between fatigue crack proagation mechanism at the high loading rate and that at the low loading rate.

Time Dependent-Fatigue Property of Recycled Fiber-Reinforced PEEK.

The time dependent-fatigue property of recycled fiber-reinforced PEEK was investigated. In particular, the influences of loading rate and recycling on this fatigue property of PEEK material were experimentally examined from a mesoscopic point of view. It was found that the fatigue propertiss of PEEK materials were dependent on loading rate and recycling. and the fracture mechanism showed creep behavior in the case of lower loading rate and recycled material. The fatigue fracture mechanisms of PEEK materials were divided into the following four types. Type I : Creep Thermal Fatigue Damage ; Type II : Creep-Mechanical Fatigue Damage ; Type III : Thermal Fatigue Damage ; Type IV : Mechanical Fatigue Damage.

Analysis of Fatigue Crack Propagation Property of Recycled PEEK Resin.

The influences of recycling process on fatigue crack propagation property have been studied for PEEK (poly-ether-ether-keton) resin materials and PA 66 (poly-amid 66) resin materials, and also the fracture mechanisms have been analyzed for their reliability. Main results were as follows : (1) The resistance against the crack propagation of recycled PEEK materials were equal to that of virgin material. On the other hand, the resistance of recycled PA 66 materials were lower than that of virgin material. (2) Examination of the fracture surface by scanning electron microscopy (SEM) revealed that the pattern of fracture surface of recycled PEEK materials were equal to that of virgin material, but that of recycled PA 66 materials were not equal to it. It revealed the existence of parabola pattern on the fracture surface. This parabola pattern was increased in its number and became small with increasing of the recycling number. (3) Examination by SEM revealed the existence of a void that diameter was about 3∼5μm in a parabola pattern. The starting point of these cracks were these voids and cracks initiated from these voids. (4) Recycled PA 66 materials were became brittle by recycling process. This is because that molecular weight of PA 66 material was decreased with increasing of recycling process number, besides, the moisture absorption rate of PA 66 material was increased during recycling process.

On Construction of Environmentally Sound Design System on Complex Deterioration for Energy Machines Produced of Advanced Reinforced Plastic. Fatigue Reliability at Elevated Temperature of PEEK Resin Having a Excellent Recycle Property.

This study was done to clarify the influence of complex deterioration on fatigue reliability. Carbon fiber reinforced and glass fiber reimforced PEEK (poly-ether-ether-keton) that is thermal plastic was examined to construct the life cycle design intended to decrease environmental stresses. Specially, the influence of recycling process and high environmental temperature on the fatigue reliability of fiber-reinforced PEEK were experimentally examined. Main results were as follows ; (1) It was noted that the S-N curves of recycled PEEK/CF and PEEK/gf materials were as nearly equal to that of virgin material. (2) The macro crack has been initiated on specimen at fatigue limit (N=107 cycle) of recycled gf material, and its crack was not propagated. On the other side, it has been not initiated on CF materials whether Virgin or recycled material. (3) The influence of the declining of fiber length by recycling process on fatigue strength of PEEK materials was small. (4) The influence of recycling process on PEEK/CF and PEEK/gf material could not be found by the fractograhy using SEM and the measuring of temperature rise on surface of specimen. So it was understood that the fracture mechanism of recycled material is squal to that of virgin material. (5) The results of fatigue crack propagation test to make clear the non-propagation crack showed that the fatigue propagation property of recycled material is equal to that of virgin material.

A Basic Study on the Construction of Fatigue Design for Carbon-Fiber-Reinforced PEEK at Elevated Temperature. The Problem on Estimation of Fatigue Reliability by Miner's Law at Elevated Temperature above Glass Transition Temperature.

The complex deterioration of stress and heat on fatigue reliability was investigated on carbonfiber-reinforced PEEK and PA 66. In particular, this study was focused on the estimation of fatigue life by Miners law under two-step loading above glass transition temperature. The main results were as follows. (1) Under two-step loading, the damage of PEEK materials could not accumulate, that is, the estimation of fatigue life by Miners law was not applied to PEEK materials. On the other side, the damage of PA 66 materials could accumulate and the estimation of fatigue life by Miners law was applied to PA 66 materials. (2) From fractography using SEM (Scanning Electron Microscope) and temperature rising, it was recognized that PEEK materials were more remarkably influenced of stress history of first-stress than PA 66 materials. (3) The mesocrack on surface of specimen of PEEK materials was small compared with that of PA 66 materials. Therefore it could be understood that the estimation of fatigue life by Miners law was not applied to PEEK materials because of existence of stress relaxation by initiation of minute mesocrack during the fatigue process.

Influence of Environmental Temperature on Fatigue Reliability at Elevated Temperature for Carbon-Fiber-Reinforced PEEK. On the Growth Mechanism from Mesocracks to Macrocracks.

The influence of environmental temperature on fatigue reliability at elevated temperature for carbon-fiber reinforced PEEK was examined. Attention was focussed on the mechanism of growth from mesocracks to macrocracks at elevated temperature. The main results were as follows. (1) The fatigue strength of CF 15 and gf 30 materials decreased with increasing environmental temperature. (2) The influence of stress and environmental temperature on fatigue strength bellow the glass transition temperature was represented by the Nf 1/T diagram and S-T (C+log tr) diagram. Therefore it was suggested that high-cycle fatigue life was could be estimated from these parameters. (3) It was appeared that the temperature rise in the fatigue damage zone was closely related to the meso crack formation process. (4) It was thought that the difference of mesocrack formation between CF 15 material and gf 30 material was reflected in the difference of the activation energy.

Crack Forming Developed at Sharp Notch Bottom in Relation to Fatigue Reliability at Elevated Temperature for Advanced Carbon Fiber-Reinforced Thermal Plastics.

The estimation of fatigue reliability at elevated temperatured for advanced carbon fiber reinforced PA46 was examined. Especially meso crack forming stage developed on notch bottom and its effect on fatigue reliability at elevated temperature. The main results are as follows, (1) The fatigue strenght, life of crack initiation and life of crack propagation for V-notch specimens were almost the same at elevated temperature. (2) From fractography using SEM, it was recognized that the matrix was elongated and the cementing of the interface between fiber and matrix was poor. So it was thought that the crack propagation resistance at elevated temperature was not influence by the kinds of fiber. (3) It was considered that the difference of crack tip heat change accompanying fatigue damage and crack propagation was controlled under the linear fracture mechanics.