Understanding the factors that determine friction between different materials is challenging due to the dependence of the friction coefficient on various surface and environmental conditions. This study investigates the correlation between the surface strain and friction force distributions on a microdevice driven by a comb actuator. The microdevice, designed to induce surface strain, was fabricated and mounted on the sample stage of an atomic force microscope (AFM). Friction force microscopy (FFM) measurements were performed within a 4.7 μm × 4.7 μm region where strain distribution was generated. A reduction in friction force was observed in regions corresponding to high surface strain in the friction direction, as indicated through finite element method (FEM)-based elastic analysis. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of an SiO₂ film on the microdevice surface, suggesting that changes in interatomic distances between SiO₂ surfaces with the same crystal structure influenced the variation in friction. Within the region where FEM analysis calculated a strain of 0.4-0.6%, a reduction in friction force ranging from 5% to 7% was observed.

The drilling characteristics of alumina ceramics during through-hole drilling with a diamond-coated carbide drill were investigated experimentally. The drilling characteristics were evaluated by cutting edge behavior, cutting force (thrust force and torque), and chipping state at the exit side of the drilled hole in relation to the number of drilled holes. Additionally, the effects of the diamond-coating thickness and drill feed rate were investigated. The drills had a typical twist shape and were made of tungsten carbide base material with diamond coatings at 10 μm and 20 μm thick. The drilling machine was a standard machining center with a simple unidirectional drill feed without vibration. In through-hole drilling, as in blind-hole drilling, the coating on the rake face flaked during the initial stage of drilling, resulting in a sharp cutting edge on the diamond-coating ridge remaining on the flank face. However, flaking of the diamond coating on the rake face was observed earlier during through-hole drilling than in blind-hole drilling. Although the chipping area increased with increasing drill feed rate, coating flaking on the rake face significantly suppressed it at all feed rates. There was a clear correlation between the chipping area and cutting force since the chipping area decreased with decreasing thrust force. Before the theoretical hole penetration, hat-shaped chipping was observed with two crack propagation directions, accompanied by a sharp decrease in thrust force. Moreover, even after observing a sharp decrease in thrust force, a gradual decrease in thrust force was observed in the case of a good chipping state. The chipping area was significantly improved by reducing the coating thickness, and the thrust force was reduced.

Various coordinate systems have been used in tooth profile analysis for cylindrical gears. An effective approach to tooth profile expression using normal polar coordinates is proposed. In this expression, the intersection between the normal at any point on the tooth profile and the operating pitch circle is determined. Then the tooth profile is represented using the length of the normal from the point on the tooth profile to the intersection, inclination angle between the normal and the straight line connecting the center of gear, and coordinate value of the intersection. Using this expression method, the path of contact is represented in polar coordinates by the length of the normal and its inclination angle. The tooth profile of the gear generated is the shape obtained by transforming the path of contact using the coordinates of the points of intersection. By applying the normal polar coordinates to a gear with an arbitrary tooth profile, the analysis to obtain the tooth profile by generation can be handled relatively easily. This method also works effectively for the analysis of the interference problem on tooth profiles. The application of this method to the analysis of a specific non-involute tooth profile adopted in this paper showed that a range of profile shift without interference could be determined, and that the interference could be prevented by modifying the tooth profile of rack. Furthermore, the interference occurring in the middle of the non-involute tooth profile was the same type of interference as undercutting in involute gears.

Water pipes have exceeded their service life, and the number of leakage and burst accidents is increasing. These accidents cause economic losses due to the interruption of operations and supply. However, replacing all the deteriorated pipes is difficult, as this would involve a huge cost and long time. Therefore, the condition of water pipes must be quantified, and an efficient maintenance management is required. Current sensors for detecting water leakage have many problems because their measurement principle is a passive system, and thus they are susceptible to external noise. In our previous study, we proposed an active vibration sensing-actuation device to improve the measurement reliability for a water pipe deterioration diagnosis. The principle of deterioration diagnosis was based on the detection of the frequency change of the in-plane bending mode. In that study, the thresholds of discrimination were determined by the amplitude of the response based on empirical knowledge, which did not allow for theoretical or systematic discrimination. In this study, we focused on a simplified discrimination method of deterioration of a water pipe and its implementation with an IoT sensor module. The following three methods were considered in terms of implementation cost: an absolute threshold method based on theoretical random vibration analysis (based on a physical model), a linear discrimination method, and a support vector machine (based on a machine learning model), and the most appropriate discrimination method was determined. Furthermore, we considered the discrimination accuracy of models based on physics and machine learning. The results show that the support vector machine has the best accuracy, followed by the absolute threshold method, which has good accuracy. However, when compared in terms of computational complexity, the absolute threshold method is superior from both perspectives in terms of implementation. However, the application of the absolute threshold method is limited to the case where the physical characteristics of the sensing target are well known. In the case of unknown physical characteristics of the target, the method based on machine learning can be applied.

The purpose of this study was to simplify the design of the tooth surface of face gear and to clarify the optimization method of the specification setting. Face gears have long been used in fishing spinning reels as a speed-increasing gear. Recently, face gears have also been adapted to geared motors for orthogonal reduction gears. However, the design method of the face gear is not supported by a standard theory, and its application is not common. This paper reports the study of face gear that meshes with involute helical gear with offset. The curved surfaces of the face gear tooth can be generated using the involute helical gear surface, which is mesh constant rotation speed. To clarify the meshing of the face gear, the author introduced the idea that the meshing contact progresses along a straight line of action. The meshing point between the involute helical and face gear proceeds at a constant speed along the straight line of action. The straight line of action is continuous and exists as a curved surface. In this method, the meshing contact is always made in the direction normal to the tooth surface of the involute pinion. This method is based on a simple theory and can be used to obtain the tooth surface coordinates of a face gear without complicated repetitive calculations. The tooth profile of the face gear calculated by the conventional generation method using a numerical analysis and calculated by the proposed meshing contact method were compared and, except for the interference area, they were the same. Using this method, design of the tooth surface of a face gear can be simplified.