STRUCTURAL MEMBER, STRUCTURAL ASSEMBLY, AND METHOD OF SELECTIVELY IMPROVING STRENGTH, TOUGHNESS, FATIGUE RESISTANCE OF STRUCTURAL MEMBER IN AREA HAVING HIGH OPERATING STRESS

摘要

PROBLEM TO BE SOLVED: To provide an improved structural assembly and a method to improve strength, toughness and fatigue resistance of a structural member in a region having high operating stress. SOLUTION: At least one of plural structural members specifies a first region having a comparatively high operating stress as a feature and a second region having a locally refined crystal grain structure, and the second region is positioned so as to partially include the first region in order to heighten the strength, toughness and fatigue resistance of the structural member in the first region. The region of a structural member having comparatively high operating stress is distinguished, and the structural member is fixed. The strength, toughness, and fatigue resistance of the structural member in the region is improved by mixing the region of the structural member having the comparatively high operating stress by a rolling friction agitation welding probe and by locally refining the crystal grain structure of the structural member in the region having the high operating stress. The structural member is fixed to the other structural member in order to form the machine casing of an airframe.