Stress Concentration Factors for Stiffener Run-Out Regions

Abstract

Stiffener and stringer run-out is a common design feature followed in aircraft structures such as fuselage, wings and empennage. The run-outs are necessary due to specific structural and interface requirements. These run-outs act as a stress raisers similar to any geometric discontinuity in these structures. The stress concentration factors (SCFs) are available only for stiffener with 90 º run-outs (also known as shoulder fillets) in the literature. In the absence of SCFs for other run-outs conservatively, the SCFs of shoulder fillets are used for all the configurations which results in over design of the structures. This paper aims at calculating the SCFs for various stiffener run-out configurations and arrive at the knock down factors (KDFs) using the finite element approach with respect to the 90 º run-out configurations. Best stiffener run-out configuration is also proposed for improving the static strength and fatigue life of structures by reducing the local stress concentrations. 

Keywords: Stress concentration factor (SCF), stiffener run-out, max principal stress, knock down factor (KDF)

Cite this Article

Prasanth Gopi Nair, Jayaprakash Dasari, Sundaresan Poovalingam. Stress Concentration Factors for Stiffener Run-out Regions. Journal of Aerospace Engineering and Technology. 2016; 6(1): 51–61p.