Speed ​​compaction Of The Constitutive Equation Of The Metal Powder

High velocity compaction (HVC) technology became a hot research topic because of its efficient, high-performance and low-cost. In order to get closed mathematical equations in studying the deformation characteristics of the metal powder, constitutive equation was essential. Based on HVC theories, the classical suppress equation and damage mechanics were introduced.At first, according to the relevant principles of HVC, the compaction process was divided into two stages: softening and hardening. The Heckel model was used for stimulation in the first stage because of its pressure and density e was a nearly linear relation. And the constitutive equation was deduced by using Huang's double logarithmic strain formula. The ZWT model was adopted in the second stage so as to reveal the nonlinearity. The item of low strain rate was eliminated, but the viscoplastic item was added. Thus the constitutive equation was established for the hot softening viscoelastic-plastic of HVC. It was proved reasonable to deduce the constitutive equation apart by the numerical simulation.Secondly, the principles of damage mechanics were applied to analyze the damage phenomena in HVC process. According to the complex characteristics of the deformation of the metal powder, the metal powder is considered as a compound of two categories of materials. The flexibility matrix of one category of material (E material) is only relevant to the modulus of elasticity of the metal powder, while the flexibility matrix of the other category of material (G material) is only relevant to the shear modulus of the metal powder. In light of the second law of thermodynamics, the constitutive relation, the corresponding effective flexibility matrix and the damage energy release rate of the damage model of anisotropic elasticity of the metal powder were established.Ultimately, according to the characteristics of the volume deformation of the powder, an appropriate dissipation potential function was selected to construct a constitutive equation of the Elastoplastic anisotropic damage of HYC powder.