Research On The Composite Colloid Coating For Laser Shot Peening On The Damaged Aircraft Parts Based On Online Repairing

There are a large number of corrosion damage components in the airplanes because of the bad aircraft service environment and the long service time,which has a significant safety risk.At present,the surface strengthening technologies are always used to repair the damaged aircraft components,while the strengthening effect of the traditional surface strengthening technology is not significant and it is usually used in offline repairing which works with low efficiency.The strengthening effect of laser shot peening is remarkable,and it is not only easy to realize online repairing,but also can effectively improve the quality and efficiency of maintenance.The coating technology is the key to realize the laser shot peening online repairing technology,but there are few reports on the coating technology of laser shot peening at home and abroad.In this paper,a new type of composite colloid coating is developed,which can be used for the online repairing of laser shot peening,which has important theoretical and practical significance to improve the effect of laser shot peening.The 7075-T6 Aluminum Alloy aircraft damaged components were taken as the research object,and the composite colloid coating was studied based on the combination of theoretical and experimental research.A manufacture way of composite colloid coating for the online laser peening repair is presented.The effect of the surface hardness based on the surface geometry and the parameters of composite colloid coating were explored.The parameters of the composite colloid coating were optimized by combining neural network with genetic algorithm,and the accuracy of the model was verified by tests.The requirements of constrained layer which is available to laser peening during online repair was deternmined firstly;through the experiment of laser peening of most used constrained layer materials to analyze the advantages and disadvantages of solid and liquid constraint layer;and decide the colloidal constrained layer material is epoxy resin,according to the different surface geometry,to decide different curing process of colloidal constrained layer,;the requirements of absorbent layer which is available to laser peening during online repair was deternmined,analyzed the advantages and disadvantages of the commonly used absorption layer material to decide the new absorbent layer materials;a new kind of composite colloid coatings based on colloid confinement layer and absorbent layer was developed for online laser peening to lay the foundation for online laser peening repair damaged aircraft.Completed the laser peening experiments of composite coating and commonly used costrained layers,the resulted showed the composite coating has better strengthening effect,Single-point single-pass impact was conducted provided with parameters as follows: laser energy of 1.6 J,pulse width 10 ns and wavelength 1064 nm.Under this circumstance,surface strengthening effect of the self-developed flexible restraint layer was best,surface hardness value of the laser peened specimens increased by 11.62%.Analyzed the influences of thickness of absorption layer,constrained layer thickness and composition on hardness.The sample was simplifed to convex arc surface,concave arc surface and inclined surface.A orthogonal experiment was designed to study the composite coating parameters effect on the convex and concave arc surface hardness enhancement,the test results showed that under the same conditions,the influence rules of the surface hardness on convex and concave arc surface are the same,but laser peening on surface hardness of concave arc strengthening effect is more significant,the surface hardness is increased by 20.43%,to lay the foundation for the online laser peening surface area to repair damaged aircraft parts.Lastly,BP neural network is established with the composite coating parameters as input variables,the increment of convex and concave arc surface hardness as the output variable,the BP neural network prediction model of high fitting degree was established with the strong predictive performance.The prediction model of genetic algorithm and BP neural network was established to potimize the parameters of the composite colloid coating,the laser shot peening on convex and concave arc surface hardness increment percentage were respectively 19.24% and 20.75%,which provides a theoretical basis for the parameter optimization of the composite colloid coating.This paper studied the tensile mechanical properties of 7075 Aluminum Alloy after laser peening,when the laser energy,shock times and overlap rate were increased,the yield strength and tensile strength of the material were increased.