Parametric optimisation of stress relief groove shape in flat ends of boilers

Flat ends of boilers with stress relief grooves have been used for many years. The existing standards set the value for the endplate thickness and admissible range of values for radius of the groove and the minimum thickness of the endplate under the relief groove. However, the codes do not specify the optimal parameters values for the endplate with stress relief groove. In this paper, the authors study the optimal choice of parameters for circular groove, and then propose its shape modification to elliptical, which considerably decreases stress concentration appearing in the zone of the groove. In the next step, the elliptical shape is replaced by the groove modelled by two spline functions, which results in further reduction of stress concentration. Finally, the groove with shape including several spline functions is proposed as an optimal one. In the performed study, the finite element modelling and the simple search method in optimisation procedures are used.