本文研究了在纯Al单晶样品的两个特殊面(包含动作Burgers矢量的S面和与Burgers矢量成最小夹角的T面)上由循环形变引起的裂纹启裂过程,疲劳试验结果表明,在循环形变过程中,S面上没有形成表面持续滑移带,但有很多微裂纹产生,裂纹较短,平均长度约为10μm,近似沿一个方向分布,与动作Burgers矢量垂直,而T面上裂纹的形貌大致与以前的工作相同。通过扫描超声显微镜观察,发现在S面上的疲劳损伤要比T面上的深得多,为此,作者提出了裂纹启裂的孔洞模型及持续滑移带形成模型。
An investigation was made of the crack initiation by cyclic deforma-tion on the two special surfaces of pure Al single crystal. One is the tOp-surfaeccontaining the active Burger's vector, and the other is the top-surface formingthe smallest angle with the active Burger's vector. The fatigue test were performedat the constant resolved shear stress amplitude (5 Pa), zero mean stress. Expe-rimentel results show that many microcracks are initiated on the side-surface onwhich no PSB surface topographies are formed during cyclic deformation. Cracks onthe side-surface are short with mean length of about 10 μm and distributed appro-ximately in a similar direction, perpendicular to the active Burger's vector, whereason the top-surface cracks are not as obvious as those on the side-surface. Observa-tions by scanning acoustic microscopy show that the fatigue damage on the side-surface is much deeper than that on the top-surface. A model of crack nucleationby voiding, and of PSB formation is suggested.
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