Design Formula to Predict Retained Steel Bolt Stretch when Joining A380 Aluminum Components at High Temperatures

A380 die-cast aluminum engine components are usually joined with steel bolts. Aluminum creep at higher temperatures causes a loss of bolt preload, measured as bolt stretch. A design formula predicting retained bolt stretch is developed based on aluminum creep. This formula correlates well with experimental results for one head gasket and one connecting rod assembly. The formula predicts the effect of joint changes in washers, spacers, bolt size, etc.