Metamodel-based optimization of the bolted connection of a wing spar considering fatigue resistance

In this paper, the optimization considering the constraint of fatigue life was conducted on a bolted connection of a wing spar, after which a series of fatigue tests were carried out to verify the optimized result. The object of the optimization was to minimize the weight of the bolted connection. Meanwhile, a constraint of fatigue life was taken into account. Considering the nonlinear relationship between the fatigue life and the design parameters, experimental design and Kriging model were applied in the optimization. In order to reduce the calculation cost of the finite element analysis and the fatigue life prediction, a so-called coupled bolt model was applied and stress severity factor approach was applied to assess the fatigue life of the connection. After the optimization, the weight of the optimized result was only 85.9% of the initial design and the fatigue life of the structure satisfied the constraint condition. In order to evaluate the reasonability of the optimized result, six specimens were machined based on the optimized result. Using these specimens, a series of fatigue tests were carried out. The test results demonstrated that the optimized result could be regarded as the best solution.