Abstract
The double notch in this test consists of primary and secondary notches. The secondary notch is situated at the root of the primary notch. Fatigue tests were made on specimens having such double notches. From the results of experiments, the following conclusions are obtained.
The notch factor of a double notch βK1, 2 is equal to the product of βK1 and βK2, where βK1 and βK2 are the notch factors corresponding to the primary and secondary notches respectively. But when the sharpness of the two notches becomes close to each other, βK1, 2 becomes less than the product of βK1 and βK2. Thus designers should pay attention to the fact that the fatigue strength of the materials with double notches becomes essentially lower than that which would be expected from each notch.
