超声辅助微细电解加工间隙空化微射流对材料蚀除的影响

doi:10.12382/bgxb.2022.0318

摘要/Abstract

摘要：

为探究超声辅助微细电解加工(UAEMM)间隙电解液内产生的空化微射流对材料蚀除的影响,建立微射流冲击工件表面流固耦合模型,通过数值仿真研究高速微射流冲击下工件表面微观塑性形变规律以及微变形对电场分布的影响规律,并进行了超声空化实验验证。研究结果表明:微射流冲击工件表面产生若干深度约0.12μm、凸起约0.04μm的空蚀坑;在外加电场下,空蚀坑凸起处的电流密度和蚀除深度较原始工件表面处提高1.2倍;进一步的凹坑成形加工实验结果表明,在超声振幅10μm、加工时间5s、加工间隙50μm工况下,与微细电解加工相比,UAEMM凹坑蚀除深度从20μm提高到100μm,同时成形凹坑底部粗糙度R_a从290nm降低到40nm;超声能场下间隙大量空化微射流促进了微细电解加工效率、加工后工件表面质量。

关键词: 超声辅助, 微细电解加工, 空化微射流, 空蚀坑, 材料蚀除

Abstract:

A fluid-structure coupling model of themicro-jet impactingthe workpiece surface is established to investigate the effect of cavitation micro-jet generated in the interelectrode gap in ultrasonic assisted electrochemical micromachining (UAEMM) on material erosion. The micro-plastic deformation of theworkpiece surface impacted by the high-speed micro-jet and the influence of micro-deformation on electric field distribution are studied through numerical simulations, and verified by ultrasonic cavitation experiments. The results show that several corrosion pits with adepth of about 0.12μm and a bulge of about 0.04μm are generated on the workpiece surface after the micro-jetimpact. Under the influence of an external electric field, the current density and erosion depth of the bulge of the corrosion pit are 1.2 times higher than that of the original workpiece surface. Furthermore,compared with electrochemical micromachining (EMM), the experimental results of pit forming processing in UAEMM reveal that the removal depth of the pit is increased from 20μm to 100μm and that the surface roughness of the pit bottom is reduced from R_a 290nm to R_a 40nm at the conditions of 10μm ultrasonic amplitude, 5s processing time and 50μm interelectrode gap. A large number of cavitation micro-jets inthe gap under ultrasonic energy can improve the machining efficiency and surface quality in EMM.

Key words: ultrasonic assistance, electrochemical micromachining, cavitation micro-jet, corrosion pit, material erosion

中图分类号:

TG662

王明环, 吕明, 何凯磊, 郑劲松, 许雪峰. 超声辅助微细电解加工间隙空化微射流对材料蚀除的影响[J]. 兵工学报, 2023, 44(8): 2368-2380.

WANG Minghuan, LÜ Ming, HE Kailei, ZHENG Jinsong, XU Xuefeng. Effect of Cavitation Micro-jet in Interelectrode Gap on Material Erosion in Ultrasonic Assisted Electrochemical Micromachining[J]. Acta Armamentarii, 2023, 44(8): 2368-2380.

图/表 26

图1 UAEMM原理图

Fig.1 Schematic diagram of UAEMM

表1 间隙空化微射流参数值

Table 1 Parameters of cavitation micro-jet

加工参数	数值
电解液中声速/(m·s^-1)	1450
电解液的密度/(kg·m^-3)	1067
泡内蒸气压强/Pa	2330
声压幅值/MPa	0.9
电解液压强/MPa	0.1

表2 材料特性参数

Table 2 Material characteristic parameters

材料	伸长率/%	泊松比	杨氏模量/MPa	黏度/ (MPa·s)	声速/ (m·s^-1)	密度/ (kg·m^-3)
6061 铝合金	20	0.33	74500		6320	2750
电解液				1×10^-9	1450	1067

表3 6061铝合金的Johnson-Cook本构参数[27]

Table 3 Johnson-Cookconstitutive parameters of Al 6061[27]

σ_s/MPa	γ/MPa	n	S	m	T₀/K	T_m/K
104.08	83.53	0.36	0.041	2.387	293	925

图2 微射流冲击几何模型

Fig.2 Geometric model of micro-jet

图3 网格划分

Fig.3 Mesh generation

图4 不同时刻微射流冲击图

Fig.4 Impact of micro-jet at different moments

图5 不同时刻工件表面等效应力分布云图

Fig.5 Equivalent stress distributions of workpiece surface at different moments

图6 不同时刻下工件表面形变云图

Fig.6 Deformation of workpiece surface at different moments

图7 不同时刻下凹坑的截面曲线

Fig.7 Cross-section curves of pits at different moments

图8 不同微射流直径冲击下工件壁面云图

Fig.8 Deformation of workpiece surface at different micro-jet diameters

图9 不同微射流直径下的凹坑截面曲线

Fig.9 Cross-section curves of pits at differentmicro-jet diameters

图10 UAEMM实验装置示意图

Fig.10 Experimental setup for UAEMM

表4 超声电解加工实验参数

Table 4 Experimental parameters for UAEMM

工艺参数	数值
电解液配比(NaNO₃∶H₂O)	1∶9
加工电压/V	10
加工间隙/μm	40,50,60,70
超声频率/kHz	28
超声振幅/μm	1,4,7,10
加工时间/s	5

图11 超声作用0.1s前后工件表面形貌

Fig.11 Morphology of workpiece surface before and after 0.1s ultrasonic treatment

图12 实验凹坑与仿真凹坑轮廓对比

Fig.12 Profile comparison between simulated and experimental results

图13 几何模型示意图

Fig.13 Geometric model

图14 工件表面电流密度分布

Fig.14 Current densityofworkpiece surface

图15 工件表面材料蚀除深度

Fig.15 Erosion depthof workpiece surface

图16 超声电解加工凹坑及其底部形貌

Fig.16 Pit of UAEMMand its bottom morphology

图17 电解加工凹坑及其底部形貌

Fig.17 Pit of EMM and its bottom morphology

图18 电解与超声电解加工凹坑轮廓曲线

Fig.18 Pit profile curves of EMM and UAEMM

图19 不同超声振幅下凹坑轮廓曲线

Fig.19 Pit profile curves under different ultrasonic amplitudes

图20 超声振幅对凹坑去除量和表面粗糙度的影响

Fig.20 Effect of ultrasonic amplitude on pit removal amount and surface roughness

图21 不同加工间隙下凹坑轮廓曲线

Fig.21 Pit profile curves under different interelectrode gaps

图22 加工间隙对凹坑去除量和表面粗糙度的影响

Fig.22 Effect of interelectrode gap on pit removal amount and surface roughness

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