Influence of Micro Surface Structures of Nodular Cast Iron Crankshafts on Plain Bearing Wear 880097

Passenger car engines have been equipped with cast crankshafts since 1950. However, their use as opposed to the steel counterparts does increase the wear rate of plain bearings. If the surface finishing operation carried out on nodular cast iron leaves an unsuitable surface texture, the bearing is likely to suffer extensive wear.

Previous research examined the effect of different machining methods on the wear behaviour of three-layer high-strength bearings. Unfortunately, it did not prove possible to complete a thorough, systematic investigation of the effects of all the individual factors, even using sophisticated diesel engine tests, since the parameters concerned are too closely interrelated to be isolated.

It was aimed at developing a straightforward and financially feasible test procedure to determine the wear mechanism operating in the semi-fluid friction region. The principles underlying the observed increase in wear on bearings could be traced back quite clearly to the specific surface machining method employed in the manufacture of the crankshaft. The cutting quality during the final machining stage by micro-finishing of pins proved to be of importance. A process was devised which guarantees a considerable reduction in wear compared with that encountered currently in normal OEM. Since completion of the test bench work, engine tests have confirmed the findings and every reason is seen to believe that the method, once suitably modified, will be adopted by engine manufacturers for volume manufactoring.