抄録
The high grade cast iron has generally been used in the structure which needs the strength according to the improvement of the cast iron, which was used comparatively widely for the high tension cast iron and in the easy manufacturing process, has been studied considerably well as to the mechanical and the physical property and so on. But it seems that the data on the fatigue strength of the high tension cast iron is not yet searched fully enough and that cast iron seems to have been used increasingly under repeated stress. So, we make experiments of the fatigue test under repeated torsion for the pearlite cast iron, and propose in this paper some considerations on the endurance limit.
Generally, the fatigue test is pursued under the basis of the stress like the experiment under a constant torsional moment, and it seems that this method is suitable to ascertain the strength of material as it is clear the weak material tends to be abused. But in fact there are many occasions on which the oscillation is under a constant torsional angle, and in this case the endurance limit does not always agree with the limit found by measuring it under a constant torsional moment and it some cases a weak material has a good endurance limit than a strong one. So the fatigue test based upon the torsional angle has some significance. We pursue the experiment with above mentioned point of view.
The Shenk type repeated torsion and bending tester is used. The results are summarized as foolows:
(1) The endurance limit under completely reversed torsion is about 15' as for the shearing angle and about 11kg/mm2 as for the torsional stress.
(2) There is a close connection between the endurance limit curve and the damping capacity curve in the pearlite cast iron, and the endurance limit may be discussed by measuring the damping capacity.
(3) And it seems that the endurance limit is intimately associated with the magnetic hysteresis loss.
