亀谷 恭子

This study describes remarkable characteristics of a novel path interval determination in filleted end milling with a tool inclination. CNC milling machine is one of the core technologies in practical manufacturing. Computer-aided technologies have contributed to the technological advancement. Tool path generation in computer-aided manufacturing is really important for CNC milling process. Although there are a lot of parameters treated in tool path generation, path interval is one of the influential factors in considering the balance between manufacturing efficiency and machined surface feature. A path interval determination in filleted end milling commonly entails the intersection problems with mathematical complexities in essence. The related studies have been reported so far, while there has scarcely been a procedure to cope effectively with the complexities. Hence, this study focused on a novel path interval determination proposed in our previous study. After the analytical discussions were made with the computational and experimental results, it was acquired from the explicit evidences that the novel procedure possessed remarkable characteristics contributable for a path interval determination in multi-axis filleted end milling.

The present paper has investigated the effects of parameters in the in-service inspections (ISIs) of time-based maintenance (TBM) or periodic maintenance on the rupture probability of a structural component subjected to creep. It is assumed that creep strain monitored in-service at regular time intervals to be a random variable following two-parameter Weibull distributions of the means and the standard deviations given by the modified θ method. The effects of such parameters as the allowable strain, the rupture strain and the shape parameters of the Weibull distributions on the rupture probability of the structural component is formulated based on Bayes theorem and is calculated considering the replacement of the component in a total operation hour of 10⁵ hr. The replacement model simulates TBM in which creep strain of a component is found to reach the allowable strain level and is replaced with a new one having zero creep strain. Variations of the rupture probability of the model with the parameters above were calculated and discussed.

The contact stiffness of joints has been evaluated experimentally and the method quantifying them has been proposed by authors. However it was found out that the range of application for this method was limited, since the method was based on the assumption that the relationship between force and real contact area of the joint is linear. Therefore, in this paper, we consider a widely applicable and more general identification method of the contact stiffness which can be applied to the joints in which the relationship between the force and the real contact area shows non-linear characteristics. As a consequence, following results are obtained. (1) The model of the joint interface with surface roughness can be made as a surface covered by springs with same length and spring constant along the profile of surface roughness. (2)The identification method of the contact stiffness of the joint based on the model can be applied to the joints, even if the relationship between the force and the real contact area of the joints is non-linear. (3) The contact stiffness per real contact area k shows constant regardless of the applied force in the joint where the relationship between the force and the real contact area is non-linear.

The joints in machine tools influence greatly the static, dynamic and thermal characteristics of the machines. Then the many researches on them have been carried out. Under these conditions, the authors have established the quantitative measurement method of contact stiffness of the joint with same material combination considering the real contact area, since the real contact area is far smaller than the nominal contact area. In this research, we propose the new measurement method of contact stiffness of the joint with different material combination expanding the former method we developed and its validity is considered. In consequence, the following results are obtained. 1) The measurement method applicable to the joint with various material combinations is established using inserted specimens. 2) The real contact area of the joint with different material combination can be accurately measured considering the reflected level of ultrasonic wave at the real contact area of the joint. 3) The contact stiffness of the joint with different material combination can be treated as the series coupling of the each contact stiffness constructing the joint. 4) The contact stiffness of the joint and each contact stiffness of the contact springs constructing the joint can be measured by the proposed method.