Abstract
Local breaking or sectional rupture of a steel construction during actual use, is caused by, in most cases, the fatigue introduced by some complicated and repeatedly applied force, moreover, it is well known fact that in case there are some notches, sharp curves or turnings in a steel body, the fatigue is accelerated.
Considering that those complicated forces are the resultant of various simple forces, the writer made a simple repeated fatigue test using specimens having various shapes of notch or sharply curved sections, and the results are compared.
According to those results, in case of tough construction special steels, it has been revealed that the influence notch angle, radious of the sharp corner of the specimen is quite remarkable, and this tendency is also shown by a simple impact test. Hence, the material and the shape of the construction in actual use have an intimate relation, therefore, selection of material and its heat treatment should be carefully considered.
In general specification for steels, there has been set Charpy or Izo dimpact value, but the shape and demensions of the test piece are fixed, so that the ordinary impact test value is not dependable specification for the selection of a material.
A specified test piece having an inferior impact value exhibits a superior impact value, if the shape and position of application being properly designed, hence, in actual application of a given material, the above mentioned facts should be bone in mind.
