Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : December 05, 2022 - December 06, 2022
Hexagon nuts with flange are widely used as fastening components for their high loadability on the mating threads and on the bearing surface. However, the width across flats specified in the current JIS B 1190 is larger than that of the bolts mated. This leads both to decrease the efficiency in assembly operation and to increase the total weight. This study aims to develop the new light-weight hexagon nuts with flange with smaller width across flats. In the previous studies the hexagon nuts with flange of M8 with the small width across flats (s = 10 mm) were manufactured by a commercial process and equipment with or without quenching and tempering, and it has been confirmed that the nuts of property classes 8 and 10 can pass the proof load test specified in JIS B 1052. However, it was clarified that relatively large plastic deformation (reduction of the concavity of the bearing face) occurs during the proof load test. This plastic deformation should be minimized since it may lead to the preload loss in the first loading cycle.
In this report, the optimum design of the flange is considered to reduce this plastic deformation by using two-dimensional axisymmetric FE analysis. The results show that the reduction of the concavity φ of the flange has the greatest effect to decrease the plastic deformation and the concavity φ must be controlled between 0° and 0.5° to achieve the same amount of plastic deformation as the standard nut. and that the root radius of the flange decreases the plastic strain concentration both on the corner and on the thread root of the nut but the effect of the reduction of the plastic deformation is limited. Additionally, it is advised that the use of the coarse series clearance hole should not be allowed to avoid the risk of the macroscopic deformation on the bearing face.
