6061-T6鋁合金惰性氣體鎢極電弧銲接件與真空硬銲件之疲勞裂縫成長性質研究

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Title:	6061-T6鋁合金惰性氣體鎢極電弧銲接件與真空硬銲件之疲勞裂縫成長性質研究
Authors:	郭峻瑋;Guo,Jun-wei
Contributors:	機械工程學系
Keywords:	6061-T6;氣體鎢極電弧銲;真空硬銲;疲勞裂縫成長速率;裂縫閉合;6061-T6;inert gas tungsten arc welding;vacuum brazing;crack growth rate;crack closure
Date:	2016-01-26
Issue Date:	2016-03-17 20:49:04 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究採用6061-T6熱處理型鋁合金，分別以惰性氣體鎢極電弧銲接(俗稱TIG銲)與真空硬銲進行對接銲接，探討兩種不同製程的鋁合金對接銲件的疲勞裂縫成長速率與裂縫閉合效應。　　研究結果顯示兩種銲接試片在銲道上的壽命皆較其它位置低。TIG銲件之銲道由於內部具有銲接缺陷，造成裂縫成長速率高於母材及熱影響區。若與母材相比，熱影響區在 ∆K<13 MPa√m 時有最低的裂縫成長速率；而當 ∆K>13 MPa√m 後，熱影響區的裂縫成長速率高於母材。真空硬銲銲道試片，在∆K<13 MPa√m時與母材有相似的裂縫成長速率，當 ∆K>13 MPa√m 後，裂縫成長速率急遽上升，至 ∆K≅15 MPa√m 破斷。觀察裂縫破斷面可知，真空硬銲銲件的銲道在裂縫成長前期是沿著鄰近銲道的母材區進行，但隨著∆K值增加，裂縫成長由母材區遷移到銲道區成長。裂縫閉合實驗結果，TIG銲的閉合應力並無顯著差別，真空硬銲的銲道會隨著裂縫長度的增長，而使裂縫閉合應力下降。 ;This study investigates the fatigue crack growth rate and crack closure of 6061 aluminum alloy butt joints welded by tungsten inert gas welding (TIG) and vacuum brazing (VB). 　　For TIG weldments, with the influence of weld defects, the crack growth rate of weld bead is higher than those of heat affected zone and base metal. The crack growth rate of heat affected zone is the lowest when ΔK is below 13 MPa√m. The crack growth rate of heat affected zone is higher than that of base metal when ΔK is above 13 MPa√m. In terms of VB, the crack growth rate of braze bead is nearly as same as that of base metal when ΔK is below 13 MPa√m. When ΔK exceeds 13 MPa√m, the crack growth rate of braze bead rises rapidly. The observation of SEM images showed that crack initiated at the base metal. When the applied load increased, the crack growth transfered from base metal to braze bead. The experimental results of crack closure test showed that there were no significant difference in crack closure stress for TIG welding. In braze bead, the crack closure stress decreased with increasing crack length.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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