As a hollow part with triangular arc-type cross-section is investigated by a strain grid experiment,the distributions of the strain along the generatrix or in the circumferential and the thickness directions and the equivalent strain are obtained. The results show that( 1) the strain of the side wall and the opening area of spun part is tension along the generatrix direction and compression in the other two directions,and the strains along the generatrix
and thickness directions are the major ones but the strain in the circumferential direction is the minor one; ( 2) the deformation modes of the side wall and the opening area during forming are respectively the shear spinning and a complex deformation major in shear spinning but minor in conventional spinning; ( 3) on the sides of both big and small conical walls,the strain along the generatrix and thickness directions first increases and then decreases from the corner to the opening area,which are the same as the equivalent strain,but the zone with large strain on the side of the small conical wall is larger than that of the big conical wall; and ( 4) the strain distribution is mainly affected by the deformation extent and velocity: the difference in the former results in the strain distribution difference between the big conical wall and the small one; and the variation in the latter causes the strain distribution to vary along the cross-section profile.