Fatigue crack growth experiments were carried out on a 304 L stainless steel compact-tension(CT) specimen under load control mode. Neutron diffraction was employed to quantitatively measure the residual strains/stresses and the evolution of stress fields in the vicinity of a propagating fatigue-crack tip. Three principal stress components (i.e. crack growth, crack opening, and through-thickness direction stresses) were examined in-situ under loading as a function of distance from the crack tip along the crack-propagation path. The stress/strain fields, measured both at the mid-thickness and near the surface of the CT specimen, were compared. The results show that much higher compressive residual stress fields developed in front of the crack tip near the surface than developed at the mid-thickness area. The change of the stresses ahead of the crack tip under loading is more significant at the mid-thickness area than it is near the surface.

1. Introduction
2. Experimental Procedures
3. Results and Discussion
4. Conclusions
Acknowledgement
References

• Gyudong Choi(Department of Materials Science and Engineering, Chungnam National University)
• Min-Ho Lee(Department of Materials Science and Engineering, Chungnam National University)
• E-Wen Huang(Department of Materials Science and Engineering, National Chiao Tung University)
• Wanchuck Woo(Neutron Science Division, Korea Atomic Energy Research Institute)
• Soo Yeol Lee(Department of Materials Science and Engineering, Chungnam National University) Corresponding author