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Volume 116
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Numerical and experimental study of shear dilation and force chain evolution of solid lubricant particles in die-wall lubrication
Wei Zhang a b *, Weichang Wu a b, Chenkang Lin a b, Kewen Cheng a b, Rongxin Chen a b, Guofu Lian a b
a School of Mechanical and Automotive Engineering, Fujian University of Technology, Fuzhou, 350118, China
b Fujian Key Laboratory of Intelligent Machining Technology and Equipment, Fujian University of Technology, Fuzhou, 350118, China
10.1016/j.partic.2026.06.015
Volume 116, September 2026, Pages 100-118
Received 19 April 2026, Revised 5 June 2026, Accepted 15 June 2026, Available online 19 June 2026, Version of Record 26 June 2026.
E-mail: zw1256@fjut.edu.cn
Highlights

• A new method for classifying multilevel force chains by their strength is proposed.

• Shear dilation behavior of lubricating particles under various conditions.

• The die-wall lubricant particles in metal powder compaction have been identified as a quasi-static flow.

• Correlation between lubricant shear dilation and force chains.

• Distribution of multilevel force chains of die-wall lubricant particles in metal powder compaction is observed.


Abstract

Based on an integrated discrete element (DEM) and experimental approach, this study elucidates the effect of die-wall lubrication on green compact surface quality in metal powder compaction. A novel mesoscopic method for multi-level force chain extraction was developed to bridge macroscopic lubrication behavior with force chain evolution. Key findings reveal that shear dilation exhibits non-monotonic dependence on shear pressure and increases with shear velocity, influenced more significantly by larger lubricant particles than by interparticle friction. Fine lubricant particles (1–10 μm) promote stable lubrication, whereas coarser particles induce surface damage during the positive dilatancy phase, exacerbated at higher velocities. With an inertial number ≤10−2 confirming quasi-static flow, fine particles form denser force chains with broader distribution, higher transmission index, and concentrated orientation in [50°, 80°], enhancing load-bearing capacity and lubrication performance. Increased shear dilation correlates with decreased force chain numbers, accompanied by rises in inertial coefficient and force chain fluctuations. Experimentally, lower shear velocity and finer particles produce compacts with superior hardness and density. This study investigates shear dilation and mesoscopic multi-level force chains during the die wall lubrication stage of metal powder compaction, thereby establishing a critical theoretical basis for optimized processing and improved green part quality.

Graphical abstract
Keywords
Powder compaction; Die-wall lubrication; Particulate materials; Shear dilation; Multi-level force chains
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