In this study, we propose a cylindrical absorber with protrusion (CAP) and its sequential partial bulging plastic forming method. In order to improve the mechanical properties of the cylindrical crash absorber, we proposed a forming method by providing multiple partial protrusions on the side wall of the crash absorber, the initial pick load was reduced and the crash energy absorption performance was improved. In order to form the CAP easily, we put the columnar rubber in the cylindrical tube, and apply pressure to the rubber from both ends of the tube, the CAP can be formed by the swelling force of the rubber. We developed sequential partial bulging forming experimental settings using the rubber, and the forming characteristics and crash energy absorption performance are verified by experiment and numerical analysis.
In order to achieve unmanned construction with a pneumatic caisson method, the present study develops an autonomous operation system using caisson shovels. The shovel mounted on the ceiling slab of the working chamber moves on a rail track and excavates underground based on the trajectory of a skilled human operator. The excavated soil is removed to the aboveground space through the material shaft using earth buckets. Since the rail track constrains the moving range and the shovel cannot always approach the earth bucket, groups of several shovels are organized to perform cooperative work based on a bucket relay system. In the present paper, we proposed a job scheduling algorithm based on terrain recognition, soil mountain selection, excavation trajectory control, and collision avoidance for an autonomous operation. Here, we used a 1/10-scale caisson platform reproducing a practical construction site and performed three cases of cooperative experiments by (a) a group of two shovels, (b) two groups of two shovels, and (c) three groups of two shovels. The results showed that, in case (a), the loading ratio always remained over 100% and the average was 130%. The cooperation of two shovels was achieved. In case (b), sharing an initial soil mountain between two groups, although the loading ratio decreased by 18%, cooperative work between groups as well as that between shovels was achieved without collisions. In case (c), sharing two initial soil mountains among three groups, the loading ratios were 126%, 107%, and 96% for the three groups. The proposed excavation planning showed the feasibility of massive construction using numerous autonomous shovels.
Nowadays, there is a particular need to develop sustainable and reproducible natural materials to address environmental issues. In this research, we devised a method to extract high-quality and high-precision bamboo fiber using a machining center. Using hot pressing, we produced bevel bamboo gears, which are mechanical elements with complex shapes. This paper describes the characteristics of bamboo fiber gears investigated by experiments. In this study, as a result of investigating the effect of changing cutting and molding conditions for fiber extraction on the parameter and strength of black color, it can be quantified by the black parameter P, fiber length Z, heating temperature T, heating time th. In addition, when the fiber length by the finite element method is about a half module as in the case of spur gears, it was found that the maximum bending strength of the teeth was exhibited by the compatibility of the fiber reinforcement effect and forming.