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Abstract:The stress concentration of lock-claws, which are one of the important parts for pneumatic fitting for a flexible tube connection, was investigated by finite element simulation. In this study, the generation of the local plastic deformation was predicted when the tube was hooked up to a pneumatic fitting in order to disperse the stress concentration, and design optimization was carried out using the Taguchi method. For the optimization, the outer width, bending angle, and inner radius of the lock-claws are used as main variables. As a result, their respective contribution ratios are revealed as 81.3%, 10.9%, and 1.5%. The ratio of the total stress distribution was improved by 4% compared with the initial design of the lock-claws. † Corresponding Author, suhch@dmi.re.kr

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Drawing and normalizing are efficient means for controlling strength, fatigue and machinability of free machining steel. Normally strength and machinability are conflicting properties which need to be optimized. In this study, the effects of normalizing temperature and reduction of area on strength, fatigue and machinability were investigated. Fine grains were generated at lower normalizing temperature and fatigue life was increased with decreasing grain size. Matrix was work hardened and elongated with increasing reduction of area. Inclusions also were elongated and cross-sectional area of inclusions along drawing axis was decreased. The effects of work hardening and grain size on fatigue life were significant, but only work hardening affected machinability. Shape and distribution of inclusions after drawing had little effect on fatigue life and machinability.

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