Abstract
Press-fitting is widely used for railroad axles, crank shafts, etc.. A lot of investigations on fatigue strength of press-fitted specimens have been so far carried out. However, many of them were done under constant stress amplitude conditions and only few investigations under varying stress amplitude have been reported.
In the present study, rotating bending stress tests were carried out on press-fitted specimens under varying stress amplitude conditions which were composed of two-level multiple-step stresses, ; one stress amplitude was higher than fatigue limit (the over stress) and the other was lower than that (the under stress). The specimens were made of medium carbon steel (S35C), and the diameters of the specimens were 10mm and 50mm. The 10mm diameter specimens were in the as received condition and the 50mm diameter specimens were in four heat treatment conditions; as received, tufftrided, induction hardened, and tufftrided after induction hardened.
The results obtained are summarized as follows;
(1) Under the varying stress amplitude, the under stress gave a fatigue damage to the specimens and the cumulative damage calculated by Miner's rule was very much less than unity.
(2) Haibach's modification of S-N diagram was more suitable than the modified Miner's rule for calculating the damage of the under stress in the range of these experiments.
