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Open AccessFeature PaperArticle

Thermomechanical Fatigue of Lost Foam Cast Al–Si Cylinder Heads—Assessment of Crack Origin Based on the Evaluation of Pore Distribution

1
Method Development & Fatigue Strength, IABG mbH, 85521 Ottobrunn, Germany
2
Simulation Structural Mechanics Powertrain, BMW AG, 80788 München, Germany
3
Institut für Werkstofftechnik, Universität Siegen, 57076 Siegen, Germany
*
Author to whom correspondence should be addressed.
Metals 2019, 9(8), 821; https://doi.org/10.3390/met9080821
Received: 30 June 2019 / Revised: 22 July 2019 / Accepted: 23 July 2019 / Published: 26 July 2019
(This article belongs to the Special Issue Metal Plasticity and Fatigue at High Temperature)
In automotive cylinder heads, thermomechanical fatigue (TMF) leads to crack initiation within the critical loaded sections. This effect becomes even more relevant in lost foam cast cylinder heads since its system-dependent porosity shows a significant influence on the lifetime under TMF loading. This work covers the identification of a criterion for crack initiation in order to provide the basis for an effective quality control with improved statistical safety by nondestructive testing. Specimens extracted from lost foam cylinder heads were investigated by uniaxial TMF tests, X-ray micro computer tomography (μCT), and scanning electron microscopy (SEM). Due to pore analyses on a global and local scale, it is concluded that pore networks are crucial for crack initiation. Thus, a tool for computation of pore accumulations from μCT data containing interaction criteria by Murakami was developed in order to assess the crack origin. The consideration of pore accumulations significantly improves the predictive accuracy compared to the consideration of single pores. View Full-Text
Keywords: aluminum-silicon cylinder head; lost foam; pore accumulation; pore distribution; thermomechanical fatigue; X-ray micro computer tomography aluminum-silicon cylinder head; lost foam; pore accumulation; pore distribution; thermomechanical fatigue; X-ray micro computer tomography
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MDPI and ACS Style

Wagner, M.; Mösenbacher, A.; Eiber, M.; Hoyer, M.; Riva, M.; Christ, H.-J. Thermomechanical Fatigue of Lost Foam Cast Al–Si Cylinder Heads—Assessment of Crack Origin Based on the Evaluation of Pore Distribution. Metals 2019, 9, 821.

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