PSI - Issue 18

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2019) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000–000 Available online at www.sciencedirect.com ScienceDirect

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Procedia Structural Integrity 18 (2019) 792–801

25th International Conference on Fracture and Structural Integrity Influence of remaining casting skin on the fatigue strength of cast iron components Kim Bergner* a , Christoph Bleicher b , Rainer Wagener b , a System Reliability, Adaptive Structures and Machine Acoustics SAM, Technische Universitöt Darmstadt, Germany b Fraunhofer Institute for Structural Durability and System Reliability LBF, Bartningstrasse 47, 64289 Darmstadt, Germany 25th International Conference on Fracture and Structural Integrity Influence of remaining casting skin on the fatigue strength of cast iron components Kim Bergner* a , Christoph Bleicher b , Rainer Wagener b , a System Reliability, Adaptive Structures and Machine Acoustics SAM, Tech ische Universitöt Darmstadt, Germany b Fraunhofer Institute for Structural Durability and System Reliability LBF, Bartningstrasse 47, 64289 Darmstadt, Germany The assessment of the fatigue strength of castings with remaining casting skin still constitutes a challenge. Until now, only the roughness of the casting skin has been considered, by a reduction factor, during the design process. This reduction factor, however, neglects the influence of discontinuities such as inhomogeneous microstructures, imperfections, pores etc. In this work, the casting skin represents the rim zone of the casting, consisting of surface roughness and a deviating microstructure. To assess the influence of the casting skin on the fatigue strength, stress- and strain-controlled fatigue tests on EN-GJS-400-15 and EN-GJS-700-2, specimens with deviating casting skins, were conducted. The cyclic behavior of the rim zone microstructure was determined via cyclic axial strain tests under alternating loading R ε = -1 on small flat specimens extracted from the rim zone. For the integration of the results from the axial fatigue tests with the influence of the surface roughness, as well as stress gradients present in cast components, on fatigue strength, cyclic bending tests under alternating R σ = -1, and pulsating loading R σ = 0, were performed. The conclusions gained from this work will be transferred in a fatigue assessment concept for the remaining casting skin on cast components. The assessment of the fatigue strength of castings with remaining casting skin still constitutes a challenge. Until now, only the roughness of the casting skin has been considered, by a reduction factor, during the design process. This reduction factor, however, neglects th influence of disc ntinuities such as inhom geneous microstructures, imperfections, pores etc. In this work, the casting skin represents the rim zone of the casting, consistin of surface roughness and a deviating microstructure. To assess the influ nce of the casting skin on the fatigue strength, stress- and strain- ontrolled fatigue tests EN-GJS-400-15 and EN-GJS-700-2, specimens with deviating casting skins, were conducted. The cyclic behavior of the rim zone microstructur was determined via cyclic axial strain tests under lternating loading R ε = -1 on small flat specimens extracted from the rim zone. For th integration of the r sults from th axial fatigue tests with the influence of the surface roughness, s well as stress gradients resent in cast components, on fatigue strength, cyclic bending tests under alternating R σ = -1, and pulsating loading R σ = 0, were performed. The conclusions gained from this work will be transferred in a fatigue assessment concept for the remaining casting skin on cast components. Abstract Abstract

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. Keywords: nodular cast iron; SGI; casting skin; graphite degeneration; fatigue strength. Keywords: nodular cast iron; SGI; casting skin; graphite degeneration; fatigue strength.

1. Introduction For years, lightweight design has been gaining more and more importance in reducing the weight of vehicles and industrial components to reduce CO 2 emissions during production and usage of the components. In order to save weight, alloys with a low density are often used, such as aluminum and magnesium alloys. However, these alloys are more expensive than cast iron components and show a lower strength. Another way to reduce weight and maintain the beneficial properties of cast iron is to scale down the component size. This is only possible if the safety and 1. Introduction For years, lightweight design has been gaining more and more importance in reducing the weight of vehicles and industrial components to reduce CO 2 emissions during production and usage of the components. In order to save weight, alloys with a low density are often used, such as aluminum and magnesium alloys. However, these alloys are more expensive than cast iron components and sho a lower strength. Another way to reduce weight and maintain the beneficial properties of cast iron is to scale down the component size. This is only possible if the safety and

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo.

2452-3216  2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Gruppo Italiano Frattura (IGF) ExCo. 10.1016/j.prostr.2019.08.228