A Semi-Analytical Investigation of Fatigue Stresses in a Bolted Headplate by Finite Elements and Classical Plate Theory

Abstract

A semi-analytical analysis involving finite elements in conjunction with classical plate theory is used to determine the stress state in a concentrated region of the headplate on an industrial ball mill. The study illustrates the practical benefits of combining analysis techniques. With this procedure, manufacturing errors in the mill design and construction are confirmed to be a facing cut and a series of nonstructural welds on a wrapper plate between the headplate and its bearing bell mounting. The early failure of the ball mill is shown to arise from the combined detrimental effects of the residual stresses formed in the welds and groupings of broken bolts in the headplate assembly. The result, confirmed by actual site examinations, is an emphatic positive verification of the merits of hybrid analysis methods, when applied in a rational manner.