Study On Laser Paint Removal Technology For Aircraft Aluminum Alloy Skin

After using for a period of time,the surface of the aircraft is subjected to external forces,radiation and various complex airflow scouring,resulting in cracking,aging,peeling and shedding damage.It is necessary to regularly remove the original coating on the outer surface of the aircraft.Laser paint removal is an important branch of laser cleaning technology.Compared with traditional paint removal technology,laser paint removal has the advantages of pollution-free,high efficiency and low cost.It is a key research direction in the field of industrial cleaning and has a wide application prospect in the field of aerospace.In this paper,laser paint removal of 7075 aluminum alloy aircraft skin with industrial application needs is studied,and the regularity of laser paint removal effect under different process parameters is studied,and many undesirable phenomena are explained by theoretical basis and experimental research.Finally,the mechanism of laser paint removal process is analyzed from macro and micro perspectives,and the temperature is monitored online to ensure the feasibility.The main conclusions are as follows.The relationship between power density and paint removal thickness was studied quantitatively.The greater the power density under the cleaning threshold,the greater the paint removal thickness.The experimental study of different cleaning times under different laser power was carried out.The conclusion was drawn that the cleaning effect was saturated with the cleaning times.The cleaning times within the cleaning threshold range were beneficial to the cleaning effect.The influence of laser energy density increases first and then decreases.When the power density is too low,the cleaning times have little effect on the removal of paint thickness.When the laser energy density is too low,the first area where incomplete cleaning occurs is the area scanned by the central segment of the scanning line.The higher the pulse frequency is,the lower the energy density of the single pulse and the lower the cleaning degree.When the pulse frequency is low,the single pulse energy density will be high,which will lead to oxidation reaction on the surface of the sample.If the frequency is too low or too high,the roughness will increase.At the appropriate pulse frequency,the surface roughness is small and the difference is not significant.The faster the laser scanning speed is,the lower the spot overlap rate in the laser scanning direction,and the lower the heat accumulation of adjacent spot,which is not enough to make the paint peel off.At the same time,when the power density is within the cleaning threshold range,the slow and low scanning mode is easier to get good cleaning effect.Under the appropriate process parameters,multiple cleaning can enhance the effect of paint removal before the standard paint removal effect is reached;under the appropriate process parameters,multiple cleaning can also remove the surface oxides to achieve good paint removal effect when the secondary oxidation reaction is caused by excessive cleaning.The larger the absolute value of defocus,the larger the diameter of the spot,and the lower the power density and heat input of the laser.The defocusing amount at the lowest roughness is exactly the parameter value of the best cleaning effect of the paint layer.In the process of laser paint removal,ablation effect and thermal vibration effect coexist.Among them,the micro-mechanism is analyzed and studied in detail,and the origin of oxide morphology is innovatively put forward.The temperature of laser paint removal process was monitored,and the feasibility of laser paint removal was verified.In this paper,the laser parameters for removing the paint layer and retaining the undercoat are obtained as follows:power density 63.65 KW/cm2,pulse frequency 10000 Hz,defocus 0 mm and scanning speed 3 mm/s.The laser parameters of aluminum alloy surface can be obtained by completely removing the paint layer,and there are many combinations.In practical application,the parameters need to be debugged according to the actual site conditions.Therefore,this paper aims to systematically analyze and study the regularity of cleaning effect and the causes of adverse phenomena of each parameter,so as to counter the adverse effects in industrial application.The avoidance should provide reference.