不同內外直徑SUS 304 不銹鋼管在循環彎曲負載下力學行為及挫曲損壞之實驗分析

Experimental Analysis of the Mechanical Behavior and Buckling Failure of SUS304 Stainless Steel Tubes with Different Outside and Inside Diameters under Cyclic Bending

本文主要為實驗探討不同內、外直徑對於SUS 304不銹鋼管在循環彎曲負載下的力學行為與挫曲損壞的影響。實驗所使用的材料為三種不同內、外直徑的SUS 304不銹鋼管，並根據尺寸大小分別命名為大管、中管及小管。為摒除外直徑／壁厚比（D（下標 o）／t比）的影響，三種不同尺寸鋼管外圍表面皆予以適度的車削以達到一固定的D（下標 o）／t比（本文採用D（下標 o）／t=40）。本文運用「彎管試驗機」及「曲度─橢圓化量測器」來進行不同的曲度控制循環彎曲負載至挫曲損壞的實驗。實驗結果顯示，SUS 304不銹鋼管在承受對稱曲度控制循環彎曲負載作用下，彎矩─曲度關係會呈現循環硬化的現象，最後彎矩─曲度曲線會形成一穩定的對稱迴圈。而橢圓化─曲度關係則呈現對稱棘齒狀的變化，而且橢圓化量會隨著循環圈數的增加而增加。此外，雖然實驗測試三種不同內、外直徑的鋼管至挫曲損壞，本文發現在對數座標中控制曲度和循環彎曲至挫曲圈數關係上卻呈現三條相互平行的直線。

This paper presents an experimental investigation of the influence of different inside and outside diameters relative to the response and collapse of SUS 304 stainless steel tubes subjected to cyclic bending. In this study, three different inside and outside diameters of SUS 304 stainless steel tubes were used. Based on the sizes of the tubes, the tubes were named large, middle and small tubes, respectively. To remove the influence of the out-side-diameter/wall-thickness ratio (D(subscript o)/t ratio), the outside surfaces of the three different tubes were machined to obtain the desired Do/t ratio (D(subscript o)/t =40 is used in this paper). The ”bending testing machine” and the ”curvature-ovalization measurement apparatus” were used to test the tubes' behavior under the loading of cyclic bending to collapse. It can be observed that the SUS 304 stainless steel tube demonstrates a cyclic hardening phenomenon from the moment and curvature relationship, but a steady-state loop of the moment-curvature curve is found after a few loading cycles. It can also be observed that the relationship between the ovalization and curvature demonstrates a symmetric ratcheting, and the ovalization increases when the number of cycles increases. In addition, although three different inside and outside diameters of the SUS 304 stainless steel tubes were tested, three parallel straight lines (corresponding to three different sizes of the steel tubes) of relationship between the controlled curvature and number of cycles to produce buckling were found on a log-log scale.