Study the densification behavior and cold compaction mechanisms of solid particles-based powder and spongy particles-based powder using a multi-particle finite element method

Abstract

Powders could be based on solid particles or spongy particles depending on the powder manufacturing procedures. In this article, the numerical study of the cold compaction process for copper solid particles-based powder (i.e. Cu solid powder) and spongy particles-based powder (i.e. Cu sponge powder) has been carried out by using a two-dimensional multi-particle finite element method (2D-MPFEM) based on single action die compaction. The effects of internal pores content, external pressure, initial packing structure on the packing densification were systematically presented. Relative density, stress distribution, internal pore deformations, and force chain movements, particle rearrangement, and interfacial behavior within spongy particles were characterized and analyzed. The results reveal that the densification behavior of the sponge powder depends basically on the internal pore's content. Moreover, at low and medium relative density (ρ <0.95), the densification behavior of the sponge powder is faster than solid particles-based powder. However, at higher relative density near unity, the force required to cause further compaction is significantly larger in the sponge powder. In addition, from the microscopic analysis, the deformation behavior of the particles and the internal pores and the force chain development rely mostly on the structure configuration, internal pore content and its position.Recently, powder metallurgy (PM) becomes an appealing process technology for both advanced and traditional materials [1]. The PM technique is competitive with conventional metallurgical manufacturing methods such as casting, forging, and machining. Moreover, it has distinctive merits such as high production rate and near-netshape forming for complex geometrical shapes, special metals, alloys with high melting points, and porous structures. In addition, it can be considered cost-effective, materials saving, easy operation, and environmentfriendly mechanism [2]. Thus, PM techniques have a lot of applications that can be used in the areas of materials, marine industries, aeronautics, astronautics, and automotive parts [3]. Powder cold compaction is one of the major stages of PM production processes that plays a key role. Through the compaction, loose powders are compressed into a cohesive and dense state using tools such as compression punches and dies [4]. The powder compact structure resulting from the powder cold compaction affects the sintering process and the properties of the final product. Therefore, any optimization of the powder compaction process requires a deep understanding of the relations between the influential factors and the densification behaviors during the powder compaction process. Consequently, a large variety of physical and numerical studies have been carried out in this regard.It is very complicated for physical experiments to characterize parameters and properties of the green compacts such as the evolution of stress distribution and local relative density and plasticity and elasticity phenomena [5]. ...

Investigating the Microscopic Mechanism of Ultrasonic-Vibration-Assisted-Pressing of WC-Co Powder by Simulation

“…The continuum theory and the discrete element method are commonly used in the numerical simulation of powder materials [ 15 ]. The continuum theory has contributed to many achievements in the research on powder impact forming, which mainly regards powder as a continuum to study the dynamic mechanical response of powder in the loading process [ 16 ].…”

“…When the pressure is withdrawn, the powder particles will slowly return to their original state, and the compact will rebound and expand along the direction of the pressing force during and after demolding, and the compact size will increase. In order to characterize the size change after demolding, Chuxuan Chen [27] expressed as a percentage the increase in the size of the compact after demolding, as shown in Equation (15).…”

Microscopic Mechanism of Ultrosonic Vibration Assisted Pressing WC-Co Powder by Simulation

“…The continuum theory and the discrete element method are commonly used in the numerical simulation of powder materials [13]. The continuum theory has made a lot of achievements in the research of powder impact forming, which mainly regards powder as a continuum to study the dynamic mechanical response of powder in the loading process [14].…”

Mesoscale Models for Describing the Formation of Anisotropic Porosity and Strain-Stress Distributions during the Pressing Step in Electroceramics

“…The pressing step consists of an irreversible deformation transforming the material from a spare powder into a compact one (green ceramic). This process is characterized by a strong nonlinear relation between stress and strain which has been modelled in the literature by using three main approaches: (i) discrete element methods, which consider each powder particle as a rigid body without any plastic deformation [ 7 , 8 ], (ii) multi-particle finite element methods, taking into consideration the behavior and interaction of individual particles [ 9 , 10 , 11 ] or (iii) continuum finite element methods, where the powder is regarded as a mechanical continuum [ 12 , 13 , 14 ]. The density distribution, the shape of the green body and the crack formation during the pressing have been simulated by finite element methods [ 15 , 16 ] or by Drucker-Prager Cap constitutive models [ 17 , 18 ] whose reliability was validated by experimental procedures, as in ref.…”