Abstract

Single overload tests performed to examine the crack retardation behavior for the specimen thickness and overload ratios. Delayed crack length was tend to increase in small thickness and big overload ratio but was difference between delayed crack length and plastic zone size that expected in specimen thickness. So retardation behavior that estimated in plastic zone size, was not sufficient. Crack tip branching and striation distribution, secondary mechanisms that effected in retardation behavior, was examined by experiment and finite element analysis. Crack tip branching was affected by micro structure, and appeared the more complicatedly according to increasing damage by overload and decreasing crack driving force in base line stress level. And crack tip branching the branching angle decreased crack driving force in the crack tip. And a characteristic of the fractography on retardation zone was that striation distribution did not appear due to decreased crack driving force.

Keywords

• Crack Retardation;
• Specimen Thickness;
• Overload Ratio;
• Plastic Zone Size;
• Compressive Residual Stress;
• Crack Tip Branching;
• Crack Tip Branching Angle;
• Finite Element Analysis;
• Striation

• 균열지연;
• 시험편두께;
• 과대하중비;
• 소성역크기;
• 압축잔류응력;
• 균열가지;
• 균열가지각;
• 유한요소해석;
• 스트라이에이션;