| Silicon carbide particle-reinforced aluminum matrix composites(SiCp/Al)are widely used in military and civil fields due to their high strength,light weight,and high temperature resistance,including engine fuel injection holes,microcrystalline circuit boards and aircraft turbine blades A large number of small holes with a diameter of 1-3mm need to be machined for other key components,but the characteristics of the material itself make traditional drilling and turning processing will cause serious tool wear,potential tool breakage and other issues can easily lead to safety accidents.As a non-contact processing method,laser processing will not produce tool wear and material waste,but there are defects such as taper,heat-affected zone and recast layer,which will affect the resistance and fatigue strength of the material.Therefore,this paper has carried out research work on the prediction model of laser ablation characteristics of SiCp/Al composites,the analysis of thermal damage of laser hole making,and the optimization of low damage hole making.The main contents are as follows:(1)A prediction model for picosecond laser ablation characteristics of SiCp/Al composites based on the Firefly Algorithm(FA)and Adaptive Fuzzy Neural Network Inference System(ANFIS)was established,which achieved a high-volume ratio SiCp/Al composite skin Accurate prediction of ablation characteristics of second laser hole making.Fuzzy-C mean(FCM)clustering algorithm is used to extract fuzzy rules from input data,and FA algorithm is used to optimize the function width and function center point of Gaussian function.In order to verify the accuracy of the prediction model,laser hole making experiments with different processing parameters were carried out,and data were extracted and analyzed for the four ablation characteristics of recast layer thickness,exit diameter,taper and entrance oxidation zone area.The analysis results show that the prediction accuracy of the four ablation features are 95.6%,97.3%,97.6%,and 96.5%,respectively.In order to explore the accuracy of the model in this paper,compared with the model results after genetic algorithm and artificial bee colony algorithm,it is found that the ablation characteristic value predicted by the FAANFIS model in this paper is more accurate.(2)The hole characteristics and ablation morphology of picosecond laser holes in SiCp/Al composites were studied.The results show that under different processing parameters,the roundness at the entrance of the hole is better,but there is an oxidation zone;while the roundness at the exit is poor,showing a sawtooth appearance,and there is incomplete ablation,and the exit diameter is smaller than the entrance.The diameter makes the through hole have a certain taper,which is an unavoidable defect of laser processing technology.The ablation characteristics of the hole wall were studied,and it was found that there are mainly gullies,micro-cracks,recast layer faults and bubble holes in the hole wall,which are caused by the high-temperature melt in the hole during the cooling process;at the same time,particle fracture and particle surface modification are also found(Corrugations,needle-like protrusions),particle micro-nano cracks and other particle damage.(3)An optimization method based on genetic algorithm-Pareto optimization is proposed to realize low-damage hole making for SiCp/Al composite laser hole making.The significant relationship between the processing factors of picosecond laser experiment and the thickness of the recast layer and the taper of the hole was obtained through analysis of variance(ANOVA)and response surface.The genetic algorithm is used to traverse the points in the given data range,and the Pareto optimization is used to determine the optimal solution that meets the processing goal.The optimized holeforming recast layer has a thickness of 4.17μm and a taper of 6.65°,both of which are significantly improved. |
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