A modified equation for the stress concentration factor in countersunk holes

The present study introduces an accurate and modified equation for the stress concentration factor of a uniaxially loaded isotropic plate with a centered countersunk hole. ANSYS Parametric Design Language (APDL) was used to build a finite element (FE) model for the plate and to run the analysis. The FE modeling strategy was initially verified and then used to solve for the maximum stress concentration factor at the countersunk hole. The effect of the dimensions of the plate and the countersunk hole, which were represented by four governing dimensionless parameters, on the value of the stress concentration factor was examined by performing several runs of the FE code. Factorial and multi parameter fit analyses were conducted on the FE results to formulate a general parametric equation for the maximum stress concentration factor in terms of the four dimensionless geometric parameters. A comparison between the results of the present equation and an older equation has shown a higher accuracy in the maximum stress concentration factor of the present equation especially at high ratios of countersink depth to plate's thickness for very thick plates (thickness equal to or greater than twice the radius of hole).

► 3-D FE model was built to study the stress concentration around countersunk holes. ► Factorial analysis has determined the main geometric parameters of the SCF equation. ► A general equation of the SCF around countersunk holes was formulated and tested. ► The new equation reduced the error in the SCF of deep sinking holes of an older equation.