摘要
本文針對雷射圓管成形之皺曲現象進行研究，以實驗及數值計算兩方面相輔進行，研究中採用CO2雷射，以高斯分佈之移動熱源於不銹鋼SUS304管件表面進行加熱，使圓管加熱區產生皺曲成形，並針對製程之溫度場、圓管軸向變位、徑向隆起變形及皺曲機制之成形力進行量測。此成形機制為一複雜之非線性熱機耦合問題，故於數值計算中以有限元素法採熱機非耦合的方式來進行解析，並以數值軟體ABAQUS作為分析工具，針對雷射圓管成形皺曲現象之製程溫度場、暫態與殘留之應力及應變場與管件皺曲及偏擺角度來進行論述，並進行不同功率、光徑、管壁厚薄及預力條件的參數討論，以期對雷射圓管成形皺曲現象做詳盡的分析，並與實驗結果進行比較。
分析結果顯示，雷射圓管成形之皺曲現象與所輸入的能量條件、機械力學條件及試件幾何等製程參數有關，在入熱能量對加熱區管壁均質加熱及未使製程溫度達到材料熔點的前提之下，提升圓管加熱區單位體積所吸收之能量與加強其局部熱膨脹體積之剛性拘束的製程參數皆能增強雷射圓管成形之皺曲現象形成。

Abstract

The object of this thesis is to analyze the buckling mechanism of laser assisted tube forming with numerical and experimental approaches. A CO2 laser with Gaussian beam mode was used as a moving heat source on a 304 stainless steel tube in laser forming. The buckling mechanism will be obtained at specific conditions and generated by thermal stresses to deform the tube specimen with bulge profiles. With/without the preload at the end of tube, the stress and strain distributions will significantly affect the bulge profiles. Furthermore the bending angle, elongation, temperature and the loading force of the tube specimen were simulated by the finite element method software, ABAQUS, and they were measured by appropriate sensors at operation conditions with various laser power, specimen size and pre-loads.

It can be found that both the numerical and experimental results are in a fairly good agreement. It can be concluded that the buckling mechanism in laser tube forming was dominated by the laser power and pre-load conditions. If the temperature of the specimen is below the melting point and the distribution is nearly uniform, the buckling phenomenon is enhanced by increasing the laser power and pre-loads for a fixed specimen geometry.

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