Use of Global and Local Finite Element Analyses to Investigate Peak Stress in Fastened Joints, Validate Structural Repairs, and Design Preventative Structural Modifications

Columbia Helicopters, Inc. (CHI) has created the Fuselage Fatigue Assessment Program as a tool to evaluate the stress distribution of an airframe, design structural modifications, and predict the life of a part. This program uses an airframe FEM to analyze and determine the stress distribution in the airframe. The results from the airframe FEA will reveal areas of peak stress in the airframe. Local FEMs of the areas showing peak stress are built and analyzed to detail the stress distributions to specific parts and/or fasteners and define an effective stress concentration factor which is used to predict the life of the part. A preventative structural modification can be designed to lessen the peak stress. Finally, the designed modification is validated back to the local and global FEMs to verify the stress has been appropriately distributed to the rest of the airframe.