Fatigue Consideration in the Boeing Design of the PHM Foils Yarnall 9 Sep 74 (0131)
Grumman asked for clarification of a statement that due to fatigue considerations in their PHM design, Boeing "did limit the maximum calculated foil mean Load (stress) to 35,000 psi." It was Boeing's intention to keep the calculated bonding stresses for one factor load below 35,000 psi to assure adequate fatigue life. To determine the influence of this fatigue criterion on the foil design, Boeing's calculations (Cecil, A.W., et al, "PHM Foil System Structural Analysis," Boeing Doc D312-80143-1, Oct 31, 1972) were reviewed, and stress checks were made of the most highly stressed locations in the forward and aft foils. Calculations are shown herein.