内圧疲労特性向上のための伸管拡管法の開発

概要

論文の詳細を見る
The fatigue property under internal pressure is the most important property for high-pressure cylinders. Generally, this property is nearly proportional to the tensile strength of the tube so far as the tube is free from material defects and welding defects. However, this property is affected by the residual stress. In the production for high-pressure cylinders, drawing is the most widely employed practice as it ensures high dimensional accuracy and permits the production of tubes of intermediate sizes. In this method, however, the fatigue property is decreased because of the generation of tensile residual stress. To eliminate this tensile residual stress, a method of pipe expansion with drawing by the use of two-stage plug has been developed. This method ensures the compressive residual stress on a stable basis and improves the fatigue limit under internal pressure. As a result, the fatigue limit improved 17% under the conditions of reducing the outside diameter by 10% and the wall thickness by 32.7%, respectively, with 0.5% pipe expansion.