An Algebraic Model for Structural and Life Analysis of Regeneratively-Cooled Thrust Chambers

An algebraic model to evaluate the structural behavior and the cyclic life of regeneratively cooled thrust chambers is presented. The model is based on the evaluation of the stresses, displacements, and elastoplastic strains induced by the severe thermomechanical environment under which the regeneratively cooled thrust chambers operate. The evaluation of the strain range accumulated during an engine duty cycle is then used to estimate the cyclic life by considering the so-called doghouse effect: that is, the peculiar deformation of the chamber inner wall that accumulates cycle after cycle. The cyclic life model is taken and rearranged from an already existing model. Both low-cycle fatigue and tensile ductile ruptures are considered as possible failure mechanisms. A minimum number of inputs are required for the application of the model: the geometry of the investigated section; the hot-gas and coolant pressures; and the wall temperature in the inner and outer walls. Of course, material characterization (mainly in terms of the stress–strain behavior and low cycle fatigue) must also be provided. After the model description and setup, a wide database of experimentally tested thrust chambers (which is almost unique in the technical and scientific literature) is reproduced for the sake of model verification.