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While the deformation and damage behavior of aluminum cylinder heads under complex thermal mechanical loading has been the subject of numerous studies in the past, cast iron cylinder heads have been in the focus of thermomechanical fatigue (TMF) only to a minor extent. In this paper, a feasible procedure is presented to set up material models and estimate service life of cast iron cylinder heads under variable thermomechanical loading conditions by the use of computer-aided engineering tools. In addition, the influence of thermal load and mechanical constraints on TMF life span is shown. A specimen model is used for parameter identification in material model setup and a cylinder head model is used for correlation with cracking phenomena. Investigation of different thermomechanical load influences is conducted on the cylinder head model. The principal strain and energy based fatigue criteria are used in assessment of TMF lifetime for the cast iron family and material specific evaluation procedures are pointed out. The results highlight the importance of exact definitions of the boundary conditions and underline the sensitivity of TMF lifespan of cast iron cylinder heads with respect to the defined boundary conditions. Considering this sensitivity, an approach conforming to the engine development requirements is proposed. It is shown that both the crack location and fatigue lifetime are predicted with high accuracy.

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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.

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