Strain Surveys of Fuel Flow Vent Hole Number 13 and Stiffener Runout Number 2 inthe F-111 Wing Pivot Fitting for a Range of Rework Shapes

摘要

The strain distributions and magnitudes at two locations in the D6AC steel wingpivot fitting (WPF) of the F-111 aircraft have been evaluated by full-scale test of a wing. These locations, known as fuel flow vent hole number 13 and stiffener runout number 2 have been sites of in-service fatigue cracking. The structural features at these two locations produce large stress concentrations and extensive yielding occurs around them under cold proof load testing (CPLT) of the wing (which was simulated in these tests). These locations are subject to in-service reworking to remove detected fatigue cracks, and a range of reworks was simulated in these tests. The interaction of residual stress/strain states (after cyclic plasticity from CPLT loading) and material removal (during reworking) made interpretation of the strain versus load behavior quite difficult. The difficulty was compounded by an overriding bi-linear elastic structural behavior of the WPF and complex structural behavior of the shear web in the WPF. A comprehensive strain versus load data base has been established for these locations to facilitate stress and fatigue analyses.