Studies on the method of bending tests for aluminum alloys

Abstract

The process of plastic deformation during bending and the method of bending tests specified by JIS were discussed with experiments of simple bending tests (Fig. 1), performed for aluminum alloy sheets, 7NO1-T6 with thickness of 10mm and 5083-0 with thickness of 16mm. The principal results obtained were as follows:(1) The relation between the maximum bending strain and the bending angle were not affected bythe variation of supporting distance.(2) The bending strain at the middle point of a test piece reached the maximum value at a bend angle near 100 degrees and kept its value over 100 degrees. Therefore, it seems that cracks would develop at a bend angle less than 100 degrees if they should occur.(3) Test pieces did not always conform to the radius of the mandrel and the internal radius of test pieces were much less than that of the mandrel. Therefore, even if the ratio of the mandrel radius to the test piece thickness. R/T, and the bending angle were kept constant, the maximum bending strain depended on the tested materials.(4) However, for an identical material, almost the same relation between the maximum bending strain and the bending angle was observed when R/T was kept constant.(5) When the spcification required a bend angle of 180degrees, the test was started by the simple bending method (Fig. 1) and followed by a procedure ofpressing the arms ofatest piece to get 180degree bending, as shown in Fig. 2. With this method, the amount of the increase of the maximum bending strain depended on the amount of the bend angle produced by the first stage bending and the variation of the relative position of the test piece and the distance piece at the second stage bending.