| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 95 === This paper discuss the thin and circular tubes of five kinds of different materials by the way of experiments and theories, including SUS 304 is managed with 316L stainless steel, 7005- T53 aluminum tube and C2700 copper tube and titanium alloy tube ,which were researched the mechanical behavior of the elasticity and plasticity, and buckling failure of circular tubes subjected to cyclic bending. The experiment of circular tubes subjected to cyclic bending is in charge of the experiment with the “tube bending machine” and “curvature-ovalization measurement apparatus.” The theory part is to adopt the endochronic theory for the basic theory of the deformation of the elasticity and plasticity, cooperate with the principle of virtual work to derive the essential balance equation. We also use one group of Fourier series to approximate to in charge of every some displacement on the section while being round to spread, trying to get the relationship of the moment, curvature and ovalization from the each other corresponding parameter. Shown by the experiment and theory result: Circular tubes of different materials subjected to symmetrical and cyclic bending, we will get the situation of the strain hardening. After the cyclic bending, the moment and the curvature will get the steady states gradually.The diameter of tube will present the behavior of ovalization , the ovalization of the tube cross-section increases in a ratcheting manner with the number of cycles.Owing to the progressive accumulation of the ovalization of the tube cross-section during cyclic bending.In addition as controlled curvature getting bigger, the number of cycles of buckling failure is getting less. Conversely, the controlled curvature getting less, the number of cycles of buckling failure is getting bigger.Finally, the relationship of the controlled curvature from the experiment and the number of cycles of buckling failure, we will use the theory which advanced by Kyriakides and Shaw in 1987, try to get the corresponding parameters.
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