Abstract: To accomplish the simulation of complex aircraft skin forming processes, four-node quadrilateral isoparametric element model for tool description is derived according to the stretch-forming feature of skin. In order to increase the efficiency of contact and search calculation, maximum gradient search path and precise point of intersection solving method based on imprecise intersected iterative initial value are established. Algorithm is introduced into the finite element simulation system-STRETCHFORM which has been developed for complex skin stretch-forming processes, and simulation for "S" shape skin stretch-forming processes is carried out, it demonstrates the good precision and stability in comparing with the results of MARC and PAM-STAMP by using exactly the same model. By analyzing the time consuming, it shows that contact and search algorithm based on maximum gradient search path owns higher computation efficiency than that of global search one.

Key words: aircraft skin stretch-forming, contact and search, finite element analysis, maximum gradient search method, four-node quadrilateral element