自激脉冲特性磨料水射流浸没式抛光数值分析与有效性实验验证

Numerical Analysis and Experimental Verification on Self-excited Pulse Characteristics Abrasive Water Jet Submersion Polishing

目的提高磨料水射流在浸没环境中的加工能力,研究流体自激脉冲特性对磨料水射流抛光的影响。方法提出一种基于流体自激脉冲特性的磨料水射流浸没式抛光方法,简称浸没式自激振荡磨料水射抛光(Submerged Self-excited Oscillation Abrasive Water Jet Polishing,SSEO-AWJP),利用腔室特定边界条件,使磨料水射流获得自激脉冲特性,使其在水中获得更好的加工性能。首先利用数值模拟分析自激脉冲射流在浸没环境下的流体状态;之后研究喷嘴与工件的轴向距离和入射角度对加工表面受力的影响;最后搭建SSEO-AWJP加工实验平台,进行氮化硅抛光对比实验,以验证流体自激脉冲特性对提高浸没环境中磨料水射抛光能力的有效性。结果SSEO-AWJP射流束在液体中以脉冲的形式存在,并具有更好的保持性。当射流束冲击工件时,其脉冲特性破坏了工件表面停滞层的稳定性,使得峰值壁面剪切力Pfm在工件表面往复移动并增大,以实现材料的高效去除。氮化硅表面抛光实验表明,相同条件下,定点加工25 min,浸没式磨料水射流抛光加工区域的最大去除深度为6.86μm,SSEO-AWJP加工区域的最大深度为17.30μm。浸没式磨料水射流加工14次后,粗糙度Ra稳定在35.7 nm;SSEO-AWJP加工5次后,Ra稳定在48.8 nm。使用SSEO-AWJP加工的工件,其表面粗糙度的下降速度始终大于磨料水射流,但是受磨粒动能影响,相同条件下,SSEO-AWJP的表面粗糙度会更高,而使用更细的磨料,可以令两种方法加工后的表面质量更加接近。结论通过数值模拟与实验分析验证了SSEO-AWJP的有效性,利用自激脉冲特性可以实现磨料水射流在浸没环境下达到高效加工的目的。

To improve its processing ability in a submerged environment,the influence of fluid self-excited pulse characteristics on abrasive water jet polishing is studied.In this paper,a Submerged Self-excited Oscillation Water Jet Polishing(SSEO-AWJP)was proposed,which made use of a specific boundary condition of the chamber to obtain self-excited pulsation characteristics of abrasive water jet,so that it could obtain better machining performance in water.First,numerical simulation was used to analyze the fluid state of the self-excited pulsed jet in a submerged environment.After that,the influence of the axial distance and incident angle between the nozzle and the workpiece on the force of the surface was studied.Finally,a processing experimental platform of SSEO-AWJP was built to conduct a comparison experiment of silicon nitride polishing to verify the effectiveness of the fluid self-excited pulse characteristics in improving the polishing ability of abrasive water jets in a submerged environment.The simulation results showed that the jet beam of SSEO-AWJP existed in the form of pulses in the liquid and had better retention.When the jet beam impacted the workpiece,its pulse characteristics made it destroy the stability of the stagnant layer on the surface of the workpiece,resulted in the Pfm moves back and forth on the surface of the workpiece,and obtained a higher peak wall shear force to achieve efficient material removal.And the surface polishing experiments of silicon nitride showed that under the same conditions,fixed-point processing for 25 min,the maximum removal depth of the processing area of submerged abrasive water jet was 6.86μm,and the maximum depth of the processing area of SSEO-AWJP was 17.30μm;the surface roughness Ra of the workpiece reached 35.7 nm after 14 times of processing by submerged abrasive water jet polishing,and that Ra of the workpiece reached 48.8 nm after 5 times of processing by SSEO-AWJP.The surface roughness decreased rate of workpiece processed by SSEO-AWJP was always greater than S-AWJP.However,influenced by the kinetic energy of abrasive particles,the surface roughness of SSEO-AWJP would be higher under the same conditions.The used of finer abrasives could make the surface quality after the two methods more similar.The effectiveness of SSEO-AWJP is verified by numerical simulation and experimental analysis,and the abrasive water jet can achieve the purpose of efficient machining in the submerged environment by using the self-excited pulse characteristic.