A three‐dimensional strain concentration equation for countersunk holes

Abstract

Countersunk rivets are used to join components to achieve aerodynamic or hydrodynamic surfaces. At countersunk holes, three‐dimensional stress and strain concentrations occur. Previously, the present authors developed a three‐dimensional equation for the stress concentration factor K_t through a detailed finite element analysis. This paper extends the study to include an equation for three‐dimensional strain concentration factor K_tε using a similar approach. The resulting equation was verified by finite element analysis for a wide range of countersunk hole configurations and plate sizes. Results showed that the maximum strain concentration is at the countersunk edge. The developed equation is within 5 per cent of the finite element results for all practical cases. It was also found that the K_tε and K_t expressions are similar and K_tε≥K_t. The maximum difference between the two is 8 per cent (for = 0.3) or ² for straight‐shank holes and about ²/2 for countersunk holes. The proposed equation is a valuable tool for strain‐based design of structural elements.