Inverse Eigenstrain Determination For Geometry Prediction Of Integral Panel By Laser Peen Forming

Stiffener integral panel is one of the most important parts for aerospace industry.Thanks to its high strain rate effect and precise and controllable action area,laser peen forming(LPF)technology has been applied in the forming and manufacturing of stiffener integral panel.Oriented to technical parameters optimization and forming shape control,this paper discussed the acquisition of the eigenstrain and forming shape prediction by the eigenstrain model,both on the methods of FEM and experiments.Moreover,the numerical simulation of LPF based on the eigenstrain was proposed and the process design of LPF of stiffener integral panel was studied.The key contents of this thesis are as follow:Non-boundary-effect clamping for LPF of square sheet.The effect of different clamping force magnitudes,clamping positions and clamping types on the LPF results was discussed.It was proposed that there was superposition between the plane tension stresses from clamping and pressure stresses from laser shock peen,and which could weaken the eigenstrain.Then the non-boundary-effect clamping setup for small-size square sheet was designed,which was proved to be valid according to the experiment and FEM results.LPF eigenstrain acquisition method based on geometric parameters.The laser pressure distribution in time and space was calibrated according to the surface indentation and the process of continuous laser shock peening was simulated by dynamic explicit model,by which the eigenstrain distribution along the depth direction was obtained.The static elastic strain-loading model was built,of which the eigenstrain were calibrated according to the experiment results of square sheets.It was proved that the forming results of LPF could be precisely predicted by calibrated FEM model.LPF modeling of stiffener integral panel based on eigenstrain method.The modeling of square sheet based on eigenstrain method was applied in the modeling of stiffener integral panel and different kinds of element types and constraint types of FEM modeling were discussed in detail,by which FEM simulation could be efficient and the characteristics of stiffener integral panel was considered.Both orthogonal stiffener integral panel and unidirectional stiffener integral panel ware studied,and according to the experiment and FEM results,the effect of stiffener on the total forming shape was discussed.Technical parameters optimization for strip LPF of stiffener integral panel.The strip LPF forming characteristics of stiffener integral panel were studied;peening strip layout was optimized by the use of genetic algorithm: aiming at forming unidirectional stiffener integral panel to cylindrical surface,access to forming results from eigenstrain model,the optimal peening strip width and interval width were conducted.In conclusion,the peening strip was helpful to suppress bending along strip direction,and the genetic algorithm was adaptable to the feature of peening strip layout problem.In summary,according to the clamping effect,non-boundary-effect clamping setup for LPF of square sheet was proposed.The eigenstrain calculated and calibrated method was established based on the measurement of geometric parameters.Eigenstrain model for strip LPF of stiffener integral panel was built,upon which the peening strip layout was optimized,thanks to this,guidance on precise control for stiffener integral panel LPF was carried out.