Additively Manufactured Lightweight Automobile Cylinder Head—A New Process for Structural Optimization from Concept to Validated Hardware

Abstract

<div>Reducing vehicle weight is a key task for automotive engineers to meet future emission, fuel consumption, and performance requirements. Weight reduction of cylinder head and crankcase can make a decisive contribution to achieving these objectives, as they are among the heaviest components of a passenger car powertrain.</div> <div>Modern passenger car cylinder heads and crankcases have greatly been optimized in terms of cost and weight in all-aluminum design using the latest conventional production techniques. However, it is becoming apparent that further significant weight reduction cannot be expected, as processes such as casting have reached their limits for further lightweighting due to manufacturing restrictions. Here, recent developments in the additive manufacturing (AM) of metallic structures is offering a new degree of freedom.</div> <div>As part of the government-funded research project LeiMot [Lightweight Engine (Eng.)] borderline lightweight design potential of a passenger car cylinder head with the use of automated structural optimization is investigated. A four-cylinder 2.0 L series production Diesel engine cylinder head is taken as basis in terms of bolting and gas flow channels.</div> <div>With the newly gained design freedom by AM, it is demonstrated that a cylinder head with up to 30% weight reduction in comparison to the reference cylinder head can be realized through a novel stiffness concept, while fulfilling the mechanical requirements. The optimized design is initially validated by CAE methods for the hot operational conditions and worst-case circumstances. Required material properties are determined through manufactured specimens. A prototype cylinder head is manufactured using the LPBF (laser powder bed fusion) process, and hardware durability is validated on a hydro-pulse test bench under the maximum cylinder pressure of the reference Diesel engine. Subsequently, a material analysis is performed, and optimization potentials at the component geometry and printing parameters are investigated to further improve material properties and hence fatigue performance.</div>