抄録
In the previous paper, the authors reported a method for rapid estimation of rotating bending fatigue limit by temperature measurement of a specimen under gradually increasing sequence of load, using a new thermometer for rotator.
In this report, the same attempt was made to estimate axial and plane bending fatigue limits of various types of specimens, by temperature measurement of the specimens by means of copper-constantan thermocouples. The diagram of stress amplitude-temperature shows in this case the same rising trend as in the case of the rotating bending test except for the sharp notched specimen investigeted. In other words the diagram can be divided into three parts, the gradually increasing region, the linearly increasing region and the rapidly increasing region. The fatigue limit is very close to the stress amplitude, at which the temperature begins to deviate from the linear portion to the rapidly increasing portion. Furthermore, it is found that the temperature rise of the specimen has close relation to the plastic strain reversed during the fatigue test. Thus, the fatigue limit can also be estimated from she amplitude diagram of stress and of strain. For the V-notched specimen investigated, these behaviors are not noticeable because the plastic deformation is considered to be localized at the notch root.
The stress gradient of the specimen may influence the stress amplitude-rising temperature rise diagram.
