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We'll analyze this bolted joint by building a non-linear finite element model in ANSYS. Our main objective is to assess the margin of safety of the flange bolts. We'd also like to determine the separation gaps that develop between the jointed parts when the assembly is loaded. 

The pressure due to the exhaust gas in the nozzle is calculated using 1D gas dynamics. It is assumed to vary linearly along the nozzle axis. The regeneration channels are omitted in the model. In exchange, a free body diagram is used to deduce the equivalent forces on the mid nozzle and lower nozzle (the upper nozzle is not modeled here).  This force pair is modeled as two separate forces. The gas temperature is 700 F which causes thermal strain. The bolt is pre-loaded to 50% of its breaking strength.

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