Molecular Dynamics Simulation and Parameter Optimization Research for Abrasive Flow Finishing of Additive Manufactured Nozzle Convergent and Divergent Sections

doi:10.3969/j.issn.1004-132X.2025.12.026

Abstract

Abstract:

Aiming at the current difficultes in surface finishing of additively manufactured complex internal flow channels， a multiscale simulation and experimental study of the abrasive flow finishing process was conducted.The abrasive flow velocity under typical pressures was determined through fluid simulation， and the micro-cutting processes were modeled using LAMMPS to establish the relationship between velocity and micro-cutting force. Results indicate that at 60~70 m/s， the cutting force stabilized with moderate magnitude， material removal remaines uniform， and the surface is free of burrs and scratches， defining an ideal finishing condition that provides a theoretical basis for process optimization. Orthogonal experiments with three factors and three levels were carried out on additively manufactured specimens featuring spiral flow channels. Post-finishing results demonstrate effective elimination of typical defects such as powder adhesion， stair-stepping， balling， and support residues， reducing surface roughness Ra from 7 μm to below 0.7 μm and Rp from 21 μm to below 1.25 μm.

Key words: nozzle convergent and divergent section, additive manufacturing, abrasive flow finishing, molecular dynamics, surface quality

摘要：

针对增材制造复杂内流道表面光整困难的现状，开展了磨粒流光整工艺的多尺度仿真与试验研究。首先通过流体仿真确定常用压力下的磨料流速范围，然后采用LAMMPS软件模拟磨粒微切削过程，建立速度-微切削力映射关系。结果表明，磨粒速度为60~70 m/s时切削力稳定适中，基材去除均匀，表面无毛刺与凹陷划痕，可视为理想光整条件，为优选工艺参数提供了理论依据。基于收扩段流道设计增材特征件并进行三因素三水平正交试验，对比光整前后表面形貌和粗糙度可知，磨粒流可显著去除粘粉、阶梯效应、大小球化及支撑残留等典型缺陷，使Ra由7 μm降至0.7 μm以下，Rp由21 μm降至1.25 μm以下。

关键词: 喷管收扩段, 增材制造, 磨粒流光整, 分子动力学, 表面质量

CLC Number:

TH162

Qian LYU, Weiwei LIU. Molecular Dynamics Simulation and Parameter Optimization Research for Abrasive Flow Finishing of Additive Manufactured Nozzle Convergent and Divergent Sections[J]. China Mechanical Engineering, 2025, 36(12): 3017-3022.

吕谦, 刘维伟. 增材喷管收扩段磨粒流光整分子动力学仿真与参数优化研究[J]. 中国机械工程, 2025, 36(12): 3017-3022.

Figures/Tables 11

Fig.1 Basic simulation process

Fig.2 Simulation model

Tab.1 abrasive velocity at various locations in the fluid domain under different pressures

推料总压/MPa

入口流速/

（m·s $- 1$ ）

出口流速/

（m·s $- 1$ ）

两侧最高流速/（m·s

- 1

Tab.1 abrasive velocity at various locations in the fluid domain under different pressures

推料总压/MPa

入口流速/

（m·s $- 1$ ）

出口流速/

（m·s $- 1$ ）

两侧最高流速/（m·s

- 1

）

63.80

64.45

76.27

73.74

74.48

88.15

90.42

91.33

108.08

Fig.3 Micro cutting force to matrix under different speeds of abrasive particles

Tab. 2 Surface roughness at different positions of the flow channel

粗糙度	入口	中段	出口
算数平均粗糙度Ra	7.02	7.42	7.60
最大粗糙度深度Rmax	47.29	55.17	47.23
平均轮廓波峰高度Rp	21.00	21.82	20.98
轮廓平均宽度Rsm	126.20	149.50	142.72

Fig.4 Three dimensional contour diagram of the internal flow channel of characteristic parts

Fig.5 Machining equipment and abrasives

Fig.6 Test parts after machining and wire cutting

Tab.3 Surface roughness measurement results

序号	磨料浓度n/%	加工压力 p/MPa	加工时间 t/s	Ra/μm	Rp/μm
1	30	6	120	0.71	1.25
2	30	8	240	0.37	0.77
3	30	10	360	0.21	0.54
4	45	6	240	0.29	0.45
5	45	8	360	0.19	0.38
6	45	10	120	0.34	0.67
7	60	6	360	0.13	0.33
8	60	8	120	0.44	0.88
9	60	10	240	0.32	0.45

Tab.4 Analysis of surface roughness range

分析指标	因素	水平	K	k	极差R
轮廓算术平均偏差（Ra）	磨料浓度/%	30	1.29	0.43	0.16
		45	0.82	0.27
		60	0.89	0.30
	加工压力/MPa	6	1.13	0.38	0.09
		8	1.00	0.33
		10	0.87	0.29
	加工时间/s	120	1.49	0.50	0.32
		240	0.98	0.33
		360	0.53	0.18
轮廓最大峰高（Rp）	磨料浓度/%	30	2.56	0.85	0.35
		45	1.50	0.50
		60	1.66	0.55
	加工压力/MPa	6	2.03	0.68	0.13
		8	2.03	0.68
		10	1.66	0.55
	加工时间/s	120	2.80	0.93	0.51
		240	1.67	0.56
		360	1.25	0.42

Fig.7 Typical morphology of characteristic parts flow channels under different pressures

References 15

[1]	王东方，刘超锋，陈少斌，等.推力室收扩段钎焊工艺优化分析试验［J］.机械研究与应用，2021，34（3）：124-130.
	WANG Dongfang， LIU Chaofeng， CHEN Shaobin，et al.Optimization Analysis Test of Brazing Process in Thrust Chamber Convergent-divergent Section［J］.Mechanical Research & Application，2021，34（3）：124-130.
[2]	YUN Yixin， WU Shujing， WANG Dazhong， et al. Impact of Multiple Abrasive Particles on Surface Properties of SiC： a Molecular Dynamics Simulation Study［J］. Vacuum， 2024， 230： 113624.
[3]	CHEN Ruling， ZHOU Pengju， LI Hui. Effect of Rotation of Abrasives on Material Removal in Chemical Mechanical Polishing Using a Proposed Three-body Model： Molecular Dynamics Simulation［J］. Tribology International， 2024， 196： 109716.
[4]	LI Junye， SONG Chao， DU Xin， et al. Effects of Machining Parameters on Abrasive Flow Machining of Single Crystal Γ-TiAl Alloy Based on Molecular Dynamics［J］. Micromachines， 2025， 16（1）： 84.
[5]	ZHANG Cheng， WU Shujing， WANG Dazhong， et al. Wear Mechanism in Nano Polishing of SiCp/Al Composite Materials Using Molecular Dynamics［J］. The International Journal of Advanced Manufacturing Technology， 2024， 131（5）： 3057-3069.
[6]	LI Jun， ZHAO Hongyan， GAO Xiujuan， et al. Material Removal Characteristic of Single Abrasive Scratching 4H-SiC Crystal with Different Crystal Surface［J］. Materials Science in Semiconductor Processing， 2024， 177： 108382.
[7]	LAVRINENKO V I. Recent Advances in Diamond-abrasive Machining of Hard and Brittle Materials （Review）［J］. Journal of Superhard Materials， 2025， 47（3）： 214-221.
[8]	GAO Tinghong， LI Qi， DONG Kejun， et al. Molecular Simulation Study of the Subsurface Damage Mechanism of Silicon Carbide/Aluminum Composites during Laser-assisted Grinding［J］. Physica B： Condensed Matter， 2025， 713： 417394.
[9]	LI Xiaopeng， WANG Fazhan， LI Guangyuan， et al. Molecular Dynamics Simulation Study of the Friction and Wear Behavior of Mono-crystalline Iron Containing Bismuth at Different Roughnesses［J］. Physica Scripta， 2025， 100（8）： 085914.
[10]	AHUIR-TORRES J I， CHEN Xun， AKAR Y， et al. Influence of the Grain Chemical Composition on the Fused Silica Polishing at Atomic Scale Using Molecular Dynamic Simulations［J］. Ceramics International， 2025， 51（7）： 9278-9291.
[11]	ZHANG Wanxue， SONG Zhuang， PU Yu， et al. A Molecular Dynamics Study on Amorphization and Material Removal Mechanisms in CMP of Polycrystalline Diamond［J］. Surfaces and Interfaces， 2025， 72： 107205.
[12]	ZHOU P， LI X， CHEUNG C F， et al. Dependence of Deformation and Damage Behaviors on Nano Scratch Defects of Monocrystalline 3C-SiC in Fixed Abrasive Processes［J］. Surfaces and Interfaces， 2025， 59： 105931.
[13]	LI Xue， ZHAO Dongdong， LIU Ning， et al. Effects of Abrasive Scratching Depth on Chemical Reaction of SiC Substrate［J］. Computational Materials Science， 2025， 253： 113864.
[14]	刘维伟，吕谦，雷力明，等.增材制造预旋喷嘴表面高质量光整技术研究［J］.西北工业大学学报，2021，39（2）：109-115.
	LIU Weiwei， Qian LYU， LEI Liming，et al.Study on High Quality Surface Finishing Technology of Pre-spinning Nozzle in Additive Manufacturing［J］.Journal of Northwestern Polytechnical University，2021，39（2）：109-115.
[15]	吕谦. 收扩段增材制造特征件磨粒流光整机理研究［D］.西安：西北工业大学，2021.
	LYU Qian， Research on the Mechanism of Abrasive Flow Finishing for the Convergent and Divergent Section Feature Parts in Additive Manufacturing［D］.Xi'an：Northwestern Polytechnical University，2021.