It is experimentally established that the endurance parameters of constructional steels (endurance limit, base number of cycles) depend upon the flow of transit energy passing through the specimen (part). It is shown that these relationships are individual characteristics of each type of steel.

In evaluation of the strength of a material by energy methods in the mechanics of a deformable solid the reserve of elastic energy of deformation in a unit of volume a is normally taken into consideration [1]. Actually in real machine parts such as shafts there frequently is a flow of transit energy with a density of b, the action which on part life is not taken into consideration. Based on the most general physical considerations this flow must influence part life, especially under periodic action. Actually in motion of crystalline lattice defects leading to appearance of damage of the material the area of elastic deformation corresponding to each defect of the crystalline lattice also moves. In other words, movement of the crystalline lattice defects forms a flow of elastic deformation energy. It is completely probable that the flow of transit energy in a solid influences the formation and especially the movement of crystalline lattice defects and in the final analysis its life. For the purpose of checking this assumption a series of experiments using the following method was set up. Specimens with a gauge Iength ten times the diameter were used for the fatigue tests in tension. The loading was by a starting-from-zero cycle using two variations. In the first variation (Fig. la) the elastic element 1 was located between the test machine active clamp 4 and the specimen 2 while in the second variation (Fig. lb) the elastic element 1 was located between the passive clamp 3 and the specimen 2. From the energy point of view these variations differ basically. In the first case only the energy caused by deformation of the specimen itself circulates in the specimen, that is, the flow of energy is internal, while in the second case the additional energy necessary for deformation of the elastic element flows through the specimen, that is. a flow of transit energy exists in the specimen, Loading using the method shown in Fig. la has been sufficiently studied [2, 3] and is normally treated as the influence of test machine rigidity on the experimental results. Tests using the plan shown in Fig. lb with a quantitative evaluation of the results in relation to the flow of transit energy are not known to the authors. Therefore detailed tests were made using this method (Fig. lb), that is, with the presence of a certain flow of transit energy. The tests were made on an MUP-30 pulsator, which may provide the same loading frequency with different elastic element lengflas. The reserve of energy in the elastic element changes and for a more correct comparison of the measurement data the understanding of the energy ratio has been introduced: