A contribution to the understanding of thermomechanical fatigue sensitivities in combustion engine cylinder heads

Abstract

Combustion engine cylinder heads are subject to frequent failure during prototype testing owing to thermomechanical fatigue (TMF). The complex interaction effects of the thermal and mechanical loads as well as the geometry and material on the cylinder head TMF behaviour have not been elaborated in detail. This paper serves to fill this gap by the utilization of finite element analysis and design-of-experiments methods on a passenger car engine model. The unique contributions of the temperature gradients, thermophysical material properties, and geometric dimensions such as the valve bridge width and thickness to the valve bridge TMF are pointed out with a certain abstraction level in modelling. The results indicate the vertical temperature difference on the flame deck valve bridge region as the dominant factor. While the valve bridge width and thickness are the geometric dominant influences, the thermal conductivity is the governing parameter among the material properties.