Numerical investigation into the densification of ferrous powder in high velocity compaction

Abstract

The densification of ferrous powder in high velocity compaction (HVC) is numerically captured by using discrete element method. Macro property (porosity), micro properties (coordination number (CN), radial distribution function (RDF) and unbalanced force), and meso properties (force chains and their orientations) are characterized and analyzed. The effect of force chains on the densification mechanism is studied. The densification in HVC is reciprocating in accordance with the evolution of local porosity and CN. This phenomenon can be promoted by the peak of unbalanced force. The number of peaks in RDF changes from three to four during densification. In addition, force chains evolve from top to bottom and then move in reverse. The distribution of force chains is related to the CN evolution, and the degree of densification is affected by the force chain strength. Force chains can promote densification by pushing particles and squeezing adjacent particles.

Effect of the sliding-rolling ratio on the force chain properties of granular flow lubrication interfaces

“…Granular flow lubrication is an effective and green modification method to improve the tribological properties of the contact interfaces which has gained widely attention in tool cutting, metallurgy and abrasive polishing fields (Wang, et al , 2021; Zhang et al , 2020; Venu and Venkateswara, 2021). Granular flow generally referred to the aggregation of a large number of solid particles which the size is larger than one micron (Gennes, 1999).…”

“…It is found that the properties of the force chain are closely related to the flow state of the particle system which decided directly the lubrication performance of particle system. Zhang et al (2020) pointed out that the strong force chains is produced due to the particle contacting with high friction forces. Wei et al (2019) analyzed the effect of rolling resistance between particles on the force chain network structure.…”

Correlation mechanism between force chains and friction mechanism during powder compaction

“…To date, the discrete element method has been able to carry out not only the microscopic research, but also the macroscopic analysis on granule matter. [13] Furthermore, the concept of the force chain was proposed, and multi-scale mechanical coupling analysis was subsequently made. [14][15][16][17] The force chain is a quasi-linear transfer route of force in a particle system that carries larger forces than other particles, along its normal direction.…”

“…[18] The nonlinear sensitive response of granular material can be obtained by using the force chain which is on a mesoscopic scale in multi-scale mechanics. [13] Therefore, it is necessary to study the evolution of force chain in powder compaction process.…”

“…A variety of force chain retrieval and recogni-tion algorithms appeared, such as the principal stress criterion method [16,18] and the contact force criterion method. [13][14][15] In addition, some scholars have conducted experimental research on the evolution of force chains. Fang et al [19] studied the arching effect of the force chain through a photo elastic experiment.…”