The frame (truss) layout based on the hybrid metal‐composite rod elements is proposed for weight saving of the primary aircraft structures. It is proposed to provide the durability of rod elements by protection system against impacts and environment. The algorithm of designing the structure with frame layout has been developed on the basis of 2‐level approach. Fast strength analysis methods based on automated numerical models have been developed. The results of comparative weight estimations of frame and conventional wing box structure of prospective civil aircraft are presented.
Experimental method for a characterization of high-cycle fatigue evolution of residual stress near cold-expanded hole is developed and implemented. The technique is based on simultaneous measurements of deformation response to narrow notch, inserted in residual stress field, on opposite specimen’s faces by electronic speckle-pattern interferometry (ESPI). Two-side measurements of notch opening displacements are performed when a single notch, emanating from cold-expanded hole edge, is inserted. The transition from in-plane displacement component to residual stress intensity factor (SIF) values follows from the relationships of modified version of the crack compliance method. The approach provides a difference in residual stress values referred to mandrel entrance and exit surface. Notches are inserted at different stages of low-cycle fatigue without applying external load. The results obtained describe fine nuances of residual stress evolution, which cannot be considered as monotonic relaxation.
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