Al/LY12爆炸焊接界面疲劳裂纹的扩展行为

Fatigue crack propagation along explosive bonded Al/LY12 interface

采用纯铝 /硬铝 (Al/LY12 )爆炸复合板通过电子束焊接制得界面裂纹四点弯曲试样。由于强度错配 ,Al/LY12界面裂纹顶端局部的变形是锐化与钝化的复合型 ,但在疲劳载荷下其整体裂端应力应变场仍然可由纯I型应力强度因子主导 ,可以采用和单材料试样相同的方式进行界面裂纹的疲劳扩展行为研究。界面裂纹可在较低的外载水平下启始扩展 ,但爆炸焊接界面存在的波纹使得界面裂纹的扩展速率出现波动 ,并且阻碍裂纹的扩展 。

Bimetallic specimens were produced from explos ion clad Al/LY12 and el ectron beam welding of bulk Al and bulk LY12 to the respective surface. Cracks w ere introduced at the interface in the specimens by milling and spark erosion. F i nite element computation was undertaken to evaluate the J integral of the i nterf acial crack of specimens.It is indicated that the standard ASTM E83 for single m aterial can also be applied to the measurement of fatigue crack propagation alon g the interface of the bimaterial specimens. The interfacial fatigue crack growt h behaviors were investigated under four points bending condition. The results s how that the crack growth velocity at the interface is some slower than that of bulk LY12 under the same loading condition, although the interfacial crack start s to grow at low load level comparing to that of bulk alloy. The wavy interface caus e d the undulation in the rate of interfacial fatigue crack growth and particularl y retarded the crack growth velocity of interface cracks.