Research On Micro-hole Processing Technology Of Fuel Injector Based On Femtosecond Laser

Compared with the traditional drilling technology,femtosecond laser drilling has become a key technology and development direction in the field of micro-hole processing.It shows an irreplaceable role and unique advantages,such as high precision,better quality,wide drilling angle,economical and environmentally friendly,no material selection.However,there are still problems of unstable processing quality,the lack of model guidance for the selection of processing parameters,and the problem of excessive investment in preliminary research.These defects restrict the development of laser drilling technology.In this paper,theoretical and experimental research on femtosecond laser drilling technology are carried out for injector microholes that meet the latest national emission standards.The numerical model of the femtosecond laser action process and a mapping relationship model between the main parameters and micro hole diameter are established.Then,through the experimental research on femtosecond laser ablation and annular drilling of 06Cr19Ni10 stainless steel,analyzed the formation and evolution of micro hole and optimized processing parameters.These research results provide theory and guidance for using femtosecond laser to process high-quality injector micro-holes.The main research contents of this paper are as follows :(1)This paper introduces the characteristics of femtosecond laser drilling technology and injector micro hole,as well as the research status at home and abroad and the current problems and deficiencies.According to the beam characteristics of femtosecond laser and its ablation mechanism to metal materials,the process of femtosecond laser drilling and the influence of processing parameters on micro-holes are analyzed.And the coupling model of energy transfer and temperature in the process of femtosecond laser processing 06Cr19Ni10 stainless steel was established.(2)Based on femtosecond laser micro-nano processing system,experimental research on the ablation threshold and thermal damage of 06Cr19Ni10 stainless steel processed are carried out.By analyzing experimental results,the law of material ablation threshold change is obtained,and a mathematical model of the depth of femtosecond laser ablation of 06Cr19Ni10 stainless steel is established.Finally,Analyzed the influence of different parameters on the ablation profile,such as laser power,pulse width,repetition frequency and scanning speed and the cause of thermal damage.(3)By experimental on femtosecond laser annular drilling of injector micro-hole,the effects of laser parameters on the aperture,roundness error and taper are analyzed,include laser power,repetition frequency,defocusing amount,scanning speed and scanning times.Designed orthogonal experiments with 5 factor and 5 level based on L25(55)orthogonal table,we analyze the significance level of the influence of laser parameters on micro-hole processing by range and variance analysis.The optimized process parameter level combination is as follows: laser power is 1.0W,repetition frequency is 9.0k Hz,defocus distance is 200?m,scanning speed 1.0mm/s,scanning times 40 times.In addition,based on BP neural network,we set up a mapping model with the above five parameters as input and micropore entrance and exit aperture as output.