Cold-Rolling of Fillets

Author:  Love, R. J.
Source:  Engineering, v 174 Aug 8, 1952 p.164
Doc ID:  1952010
Year of Publication:  1952
Abstract:  
In a series of tests conducted by the Motor Industry Research Association, a process was devised for strengthening fillets by cold-rolling with steel balls. The process was used on cast crankshaft specimens made of flake-graphite iron, and the results of fatigue tests show that cold rolling the fillets increased the limiting stress of the crankshafts by 60% for reversed bending and by 80% for "one way" loading. The method of rolling was to use three balls equally spaced around the fillet and held in place by a loading ring. The ring was assembled on the crankpin and the loads were applied through four coil springs that were compressed by means of a screw attachment. The load chosen was such as would produce a small but detectable deformation in the fillets, approximately .003". The small ridge of metal formed by this operation at the junction of the fillet and journal was removed by a simple polishing operation. The author maintains that the cold-rolled fillets are clearly superior to those produced by conventional means, since, apart from the beneficial cold-working effect, they are very smooth, truly circular, and of closely controlled radius. The author also states that similar, or even better results can be expected on steel parts since steel is known to react favorably to cold-rolling.