INVESTIGATION OF EFFECT OF GRAIN SIZE ON THE MECHANICAL PROPERTIES OF AL ALLOY BY USING FRICTION STIR HOLE EXPANSION

The aim of the research work was to investigate on the effect of Friction stirring of a fastener hole affects the surface and mechanical properties of the hole. The surface that was friction stirred had the same roughness as that of the drilled hole. The surface and mechanical properties affect the number of cycles sustained under fatigue loading. A typical gradient of these stresses along thehole axis is observed. The residual hoop stress distribution introduced by means of the alternative FSHE method decreases along the distance from the center of the increases. An axial residual hoop stress gradient is also observed, but to a lesser degree than mandrel cold working stress result. A new conception for increasing fatigue life of large number of fastener holes in aircraft structures is developed. It is accomplished by a new method, called friction stir hole expansion (FSHE).