• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.12
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• pp.1004-1011
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• 2018

Recently, pyrotechnic separation nut has attracted a considerable attention because of its shock reduction effect among various pyrotechnic mechanical devices. However, its bolt loosening behavior under transverse vibration has not been studied sufficiently, since segmented nuts are utilized instead of conventional nut in pyrotechnic separation nut. With the background, bolt loosening analyses are carried out referring to Junker vibration test. The analysis procedure consists of two steps. The first step is the bolt fastening step, screwing the bolt by fastening torque. The second step is the bolt loosening step under transverse vibration. Through the procedure, bolt loosening behaviors are obtained, and the effect of clearance on loosening behavior is closely investigated for reliable design of pyrotechnic separation nut.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.28-34
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• 2020

In this study, hole-boss locking washers were developed to prevent vibrational loosening, and a benchmark test was conducted to compare these washers with existing wedge locking washers, which are imported and high-priced. The developed washers consist of an upper washer with bosses and a lower washer with holes, and the bosses are caught in the holes so that the bolt is not loosened. Additionally, the top side of the upper washer and the underside of the lower washer have small wedges perpendicular to the direction of the bolt loosening, suppressing slips. A test by the Korea Test Laboratory indicated that the ratio of the loosening torque to the joining torque is greater than 70%, confirming that the developed washers have a sufficiently high anti-loosening performance. A Junker test apparatus was manufactured for the testing of vibrational loosening and a test comparison between the proposed washers and the existing wedge locking washers shows that the proposed washers have a slower reduction in the clamping force and a higher loosening-resistance in a vibrational circumstance compared with the wedge locking washers. These results indicate that the developed washers demonstrate a high performance and boast price competitiveness.