|Title||Standardization for Large Deflection Rotating-bending Fatigue Testing Method|
|Author||Research Committee on Standardization for Nakamura-type Rotating-bending Fatigue Testing Method|
|Abstract|| Nakamura-type rotating-bending fatigue
test has been widely used in 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.
Considering these background, actual 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 committee 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 method 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.
(5)Most useful bush which has good wear resistance and low friction is made from ultra high molecule polyethylene.
|Key Words||Nakamura-type rotating-bending, Large deflection theory, Beam bending theory, Deflection-controlled method, Load-controlled method|