| Nickel-based superalloy materials have been widely used in the aerospace,aviation and nuclear industries due to their good high-temperature mechanical properties and radiation resistance.and have placed higher requirements on their processing quality and processing efficiency.Abrasive water jet machining(AWJM)is used in finishing processes due to its stable removal function and adaptability to the shape of the workpiece.AWJM has defects such as low removal rate and poor adaptability to large-size surfaces,which limits its large-scale application.A new multi-nozzle abrasive water jet machining(M-AWJM)process based on AWJM to improve the processing efficiency of AWJM was proposes in this paper.The material removal characteristics and experiments of multi-nozzle abrasive water jet machining are discussed through the combination of simulation and experiment.The main research contents include the following:(1)For the research progress of AWJM,the domestic and foreign literatures were consulted.The advantages and disadvantages of several new ultra-precision polishing methods were compared.The defects and-future research directions of AWJM were pointed out.The research on AWJM simulation and experiment is summarized.The feasibility of using M-AWJM for ultra-precision manufacturing was pointed out.(2)The M-AWJM material removal model is established based on the single abrasive particle removal mechanism and the distribution characteristics of the abrasive particles in the flow field.The axial erosion wear of a single abrasive grain and the tangential shaping shear wear are the main reasons for the removal of the workpiece surface material.The greater the injection pressure,the higher the erosion rate of the material.The spatial distribution of abrasive grains,the diameter distribution and the velocity distribution of the workpiece wall surface determine the shape of the M-AWJM workpiece wall material removal.(3)Using Fluent to simulate single-nozzle abrasive water jet machining(S-AWJM),vertical multi-nozzle abrasive water jet machining(VM-AWJM)and inclined multi-nozzle abrasive water jet machining(IM-AWJM).By analyzing the composite flow field velocity cloud map,pressure cloud map and wall surface removal rate cloud map,the material removal shapes of S-AWJM,VM-AWJM and IM-AWJM were predicted respectively.The effects of different nozzle spacing,nozzle type,spray pressure and spray distance on the flow field distribution and material removal shape of M-AWJM were simulated and compared.(4)The M-AWJM experimental platform was designed and constructed.The experimental platform is composed of four parts: pressure supply device,injection system,abrasive liquid circulation supply system and auxiliary system.For the different nozzle types,the superconducting alloy Inconel 718 was tested with a fixed-point jet.Through the analysis of the experimental results of surface roughness and material removal rate,the material removal ability of the multi-nozzle abrasive water jet machining was verified.(5)For Inconel 718 superalloy,the relationship betw een different injection distance,machining time,injection pressure,abrasive particle concentration and workpiece surface quality and material removal rate was explored.The experiment shows that the vertical five-nozzle circular distributed abrasive water jet machining(V-5CDJM)is used to process Inconel 718 superalloy.The surface roughness can be as low as 35.744 nm after 10 minutes processing,and the material removal rate is higher than that of the single nozzle abrasive water jet machining.Ther efore,M-AWJM can be retained S-AWJM material removal ability at the same time to obtain higher workpiece surface quality,machining efficiency has been significantly improved. |
PDF Full Text Request