Stress Field Intensity Approach For Fatigue Life Analysis Of Cold Extruded Holes

Fatigue failure in fastener holes is one of the main forms of aircraft structural failure, improving the fatigue strength of fastener holes’ inner surface has become an important task for aviation manufacturing industry. Residual compress stress induced by cold extrusion technology would reduce the tensile stress greatly when the structural were subjected to cycle loading. Thus, cold extrusion technology has been widely used in engineering practice as a kind of fatigue resistance technology.This paper calculated the residual stress around the cold extrusion hole by using the theory of elastic-plastic mechanics under some ideal assumptions and the expression of residual stress distribution were established. And we found that the theoretical computation results were roughly in line with the trend of measurements. Two-dimensional finite model was set up in ABAQUS, And the results of the distribution of residual stress showed a good agreement with theoretical computation results. Moreover, A Three-dimensional finite model was developed for the numerical simulation of the real processing of cold extrusion to analysis and study the distribution of residual stress along the thickness direction.This paper estimated the fatigue life of cold extruded hole by the theory of stress field intensity. And a new simplified method was put forward based on the approach of stress field intensity. After comparison between the result of the experiment data and calculated value, we found the new method has a good calculation accuracy. Besides, the stress concentration factor of joints with cold extruded hole was modified, and finally the stress serious factor was proposed based on the method of SSF.