Abstract
This paper is to present an important issue of fatigue failure in the design of multi-fasteners jointed structure. To avoid failure in the connection area, Sines criterion is utilized. Fatigue constraints are handled in the context of stress based topology optimization. To eliminate the high stresses caused by the finite element modeling, the control volume is defined to evaluate the stress states around the fasteners. The standard topology optimization is extended to minimize the structural compliance with fatigue failure constraints. To address singularity problems related to stress constraints, q-p relaxation is used. P-norm is used as the constraints aggregation scheme. Basing on the above, the design sensitivity of fatigue constraints is derived and calculated. The proposed method is verified by a numerical example of an assembled I-beam. The comparisons of the numerical results have shown the effect of the fatigue constraint.
Highlights
The main idea of topology optimization is that the layouts and topology configurations of structures are considered as deign variables and optimized numerically to satisfy different design requirements
Past experience shows that 85% of fatigue failure in aircraft structures occurred around fasteners
The standard topology optimization problem is extended with the fatigue constraints, which can be formulated as: find : r 1⁄4 ðr1; r2; . . . ; ri; . . . rnÞ; min : Cd uT Ku; s:t: : f 1⁄4 Ku; ð6Þ
Summary
The main idea of topology optimization is that the layouts and topology configurations of structures are considered as deign variables and optimized numerically to satisfy different design requirements. In an assembled aircraft structure, fasteners as bolts, rivets and the like, are widely used to joint the member components and distribute loads. When strength is considered in topology optimization, stress and fatigue are usually the primary concerns. Earlier studies were focused on developing analytical and numerical methods for stress and failure predictions of multi-fastener joints. The objective function to be minimized was the maximum radial stress, which was assumed to be correlated with the fatigue life. Rui et al [5] used an optimization algorithm to minimize the stress intensity factor of spot-welds, which was assumed to be a control parameter for the fatigue life of the structure. Topology optimization is extended to the design of the assembled structure with fatigue constraints. The fatigue optimization of an assembled structure is presented
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
