SYMPOSIA PAPER Published: 22 September 2020
STP163120190134

Fretting Fatigue Characterization in Press-Fit Joints of AM Parts by X-Ray Tomography and Digital Image Correlation

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Complex structures made by additive manufacturing (AM) have to be integrated into larger components. In these cases, contact conditions at the press fit joint can induce crack initiation and accelerate damage accumulation when the system is subjected to cyclic loading. Surface-finishing techniques can improve the surface quality of AM structures. However, surface finishing can be a challenge when the geometry is extremely complex. Moreover, electropolishing, which is often applied to AM parts, is unable to reduce the waviness associated with the AM process, at least when reasonable polishing times are considered. Furthermore, the surface finishing of AM parts can lead to the opening of subsurface pores, which are associated with the AM process and are among the main causes of fatigue failure in AM parts. Cracks initiate from the micronotches related to the rough surface. However, at the same time, roughness tips can lead to superior form fit and additional adhesive forces, especially if the AM part has a higher hardness than the conventionally manufactured part. Consequently, new testing procedures have to be developed for press-fit joints involving AM parts subjected to vibrational loading as the classical fretting test cannot address the benefit of an additional form fit. In this study, the internal defect characteristics of AM specimens such as pores and lack of fusions, as well as the three-dimensional surface morphology, were characterized by high-resolution microcomputed tomography. The basic idea of the AM specific testing procedure presented in the present work is to use a classical flat dog-bone fatigue specimen with a press-fit joint in the center. This specimen is then subjected to fatigue loading in order to monitor the deformation field in the region of the joint by digital image correlation. This procedure enables the early detection of the onset of damage.

Author Information

Bacaicoa, Inigo
Institute for Materials Engineering, University of Kassel, Kassel, DE
Horn, Sascha
Institute for Materials Engineering, University of Kassel, Kassel, DE
Brueckner-Foit, Angelika
Institute for Materials Engineering, University of Kassel, Kassel, DE
Richter, Julia
Institute for Materials Engineering, University of Kassel, Kassel, DE
Niendorf, Thomas
Institute for Materials Engineering, University of Kassel, Kassel, DE
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Details
Pages: 257–270
DOI: 10.1520/STP163120190134
ISBN-EB: 978-0-8031-7709-3
ISBN-13: 978-0-8031-7708-6