SYMPOSIA PAPER Published: 08 September 2020

Investigation of Fatigue Behavior around Nonmetallic Inclusion Using a Newly Developed Rolling Contact Fatigue Test Method


In recent years, automobile electrification and wind power generation have been expanded worldwide, and the conditions of bearing use in these processes will become more severe. In order to develop a longer life product, it is necessary to clarify the mechanism of internal fracture from the viewpoint of crack initiation and propagation around the inclusion, which is the principle of fatigue behavior. In this research regarding inclusion-originated flaking, a new rolling contact fatigue (RCF) test method was proposed to visualize the crack behavior around inclusions that contributes to life improvement and establishment of quantitative life prediction technology. This method enables us to introduce the preselected inclusion artificially into the test pieces. Furthermore, it also makes it possible to control the interfacial state between an inclusion and its surrounding matrix. Based on the results, the RCF models for internal fracture are classified into two cases. One is the case of an inclusion with an artificially introduced gap. This model allows shallow-inclined crack initiation from both sides of the inclusion, followed by horizontal crack propagation until flaking. The cracking behavior is similar to the case of a cavity in steel; therefore, this type of defect is harmful for RCF life. The other case is that of an inclusion without a gap. The model allows that the crack initiates nearly 45° to the contact surface around the inclusion and then arrests. This type of defect is less harmful for RCF life.

Author Information

Fujimatsu, Takeshi
Material Research Group, Research and Development Center, Himeji, JP
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Pages: 103–130
DOI: 10.1520/STP162320190100
ISBN-EB: 978-0-8031-7693-5
ISBN-13: 978-0-8031-7692-8