Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : October 07, 2017 - October 09, 2017
Stress distribution of brake disks during braking is complicated due to sliding contact and frictional heat. To investigate the effect of sliding contact on fatigue strength of low alloy steel, a new fatigue test method which enables to apply cyclic loading with sliding contact is developed. Two main results are obtained by this method. Firstly, the fatigue life with sliding contact is longer than that without sliding contact at finite life regime. Wear volume measurement results suggest that the condition with sliding contact has longer life because fatigue damaged layers are possibly worn away. Secondly, the fatigue limit with sliding contact is 36 % lower than that without sliding contact. Moreover, the fatigue tests without sliding contact have no fatigue failure at more than 106 cycles, whereas the tests with sliding contact have. To discuss the fatigue limit reduction caused by sliding contact, fatigue tests applying sliding contact prior to cyclic loading are conducted. The fatigue tests after sliding contact have no fatigue failure at more than 106 cycles similar to the tests without sliding contact. This result indicates that change of surface properties such as surface roughness during the fatigue tests due to sliding contact is one of the main causes of the fatigue limit reduction. Measured surface roughness actually increase with increasing of sliding time. Predicted fatigue limits by using √area parameter calculated from surface roughness correspond well to experimental fatigue limits. Therefore, it is concluded that surface roughness variation due to sliding contact much affects on fatigue strength of the tested low alloy steel.
