大たわみ回転曲げ疲労試験方法標準化に関する研究

抄録

Nakamura-type rotating-bending fatigue test has been widely used order to evaluate the fatigue strength of wire, because of its simplicity and rapidity.
However it has been used for the relative comparison within results obtained by own institution, it was difficult to compare the results with data obtained by other institutions, because its standard testing method has not been established.
Consideing these background, actural problems of the conventional method were investigated, and load-controlled method and deflection-controlled method were tested in order to compare the scattering of static bending stress and dynamic fatigue life.
Furthermore, some factors which cause scattering were checked in detail.
On the basis of these investigations, this comittee proposed a new standard testing method.
In this study, the following facts were mainly clarified.
(1) Load-controlled method has been conventionally used in many institutions, and the bending stress is calculated by using the linear solution based on the beam bending theory.
(2) Bending stress should be calculated by using the equation based on the large deflection theory.
(3) Deflection-controlled metod is superior to load-controlled method comparing the amounts of scattering of data.
(4) By measuring the deflection, true stress can be estimated even in load-controlled method.
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