The Japan Transport Safety Board (JTSB) investigates the cause of an accident and the degree of damage it causes with the aim of preventing the reoccurrence of similar accidents and mitigating damage deriving from these impacts. This paper highlights, a case in which a crack propagates outward from the center of an intermediate shaft flange mating surface, resulting in shaft breaks. After investigating the fracture surface in a detailed manner, we have discovered that the destruction was due to fluctuations in the thrust applied to the intermediate shaft causing bending stress in the shallow concave portion of the flange mating surface, and that this stress prompted the crack generated in the center to proceed outward.
The authors have been considering a lookout support system using cameras at a ship. In previous studies, a stereo imaging system was proposed to measure the locations of other ships. However, in the case of long-distance measurement, the previous results have often included a large margin of error due to slightly less accurate gaze detection for the target ship. This research paper describes our effort to improve the accuracy of long-distance position measurement by using a three-camera stereo vision system. Our experimental results show that errors can be reduced when using three cameras compared with the outcome obtained with two cameras. However, they also indicate that a systematic error can be observed even from the results of three camera measurement depending on methods of computation. The authors have analyzed the cause of this error through a numerical simulation.
In order to study the effect of sampling positions along an exhaust pipe on PM measurement, we measured PM emitted from a medium speed 4-stroke marine diesel engine. The marine diesel engine was operated at steady state using low sulfur marine diesel oil for PM measurement. Two partial flow dilution systems were used to measure PM emitted from the engine. First of all, in order to check the equivalence of the two partial flow dilution systems, they had the almost same sampling positions on the exhaust pipe of the engine. Since PM emission levels can change slightly even during steady state operation of the engine, it was necessary to perform simultaneous PM measurement in order to compare the results from the two partial flow dilution systems with high accuracy. It was confirmed through this statistical process that the two systems have equivalent performance. Then PM was measured simultaneously after the sampling position of one of the two systems was moved approximately 12 meters on the exhaust pipe. It was found that the emission levels from the downstream system were two to four percent lower than those from the upstream system, and that the results from the two systems were well-matched. We believe that when the engine operates steadily, it is possible to select sampling positions within the distance described in this report.