Strain hardening of a powder body in pressing

Koval'chenko, M. S.

doi:10.1007/s11106-009-9118-7

Cited by 19 publications

(10 citation statements)

References 18 publications

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“…The periodic solutions of dynamic system (8) corresponding to complex roots of Eq. (9) at initial impact velocity 0 < x & and constant control parameters α 2 and α 3 over narrow time ranges Δt = t -t 0 (t 0 is the initial time) become:…”

Section: Dynamic Model Of Impulse Hot Pressingmentioning

confidence: 99%

“…In general, the experimental data are rather scattered. Hence, for their polynomial fitting (smoothing) using least-squares criterion [8], values at 873 and 1223 K with the most reliable curves were chosen. The solid lines show curves obtained by subsequent computer simulation.…”

Section: Model Applicationmentioning

confidence: 99%

“…A dynamic approach to simulating the process that occurs in a mechanical system with one degree of freedom consisting of an impact machine and a deformable powder body enabled an adequate description of impulse hot pressing of WC-Co hardmetals [6] and an analysis of the hot compaction dynamics of porous copper and iron blanks [7]. This paper presents results of computer simulation and analyzes experimental data on the compaction of porous blanks from a Cu + 2 wt.% Al 2 O 3 powder mixture during impulse hot pressing [8] at the South-Russian Technical University (Novocherkassk, Rostov Region, Russia).…”

Section: Introductionmentioning

confidence: 99%

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Simulation of the compaction dynamics of Cu + Al2O3 powder mixture under impulse hot pressing

Koval'chenko

Hrebenok

Ochkas

2011

Powder Metall Met Ceram

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The compaction dynamics of Cu + Al 2 O 3 powder mixture under impulse hot pressing is simulated using a third-order dynamic system. The computer simulation has established the time dependence of the force induced by mechanical interaction between the impact machine and a heated porous blank, time variation in density, and root-mean-square strain rates and stresses in the matrix that forms the porous body. The phase trajectory of dynamic system from the beginning of compaction to the elastic recoil of the hammer block characterizes impact dynamics. The mechanical-thermal effect induced by bulk viscous flow and manifested itself as an increase in temperature of the porous body is determined. It is established that the shear viscosity of the porous body matrix shows a stronger dependence upon the initial impact velocity in comparison with the heating temperature. The activation energy of the matrix viscous flow is equal to 0.266 eV.

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Section: Dynamic Model Of Impulse Hot Pressingmentioning

confidence: 99%

Section: Model Applicationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simulation of the compaction dynamics of Cu + Al2O3 powder mixture under impulse hot pressing

Koval'chenko

Hrebenok

Ochkas

2011

Powder Metall Met Ceram

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“…E 0 and ν 0 are the Young's modulus and Poisson's ratio of the matrix forming the porous material [14];…”

Section: Rheology and Deformation Dynamics Of A Porous Body Under Appmentioning

confidence: 99%

Pressure sintering of powder materials

Koval'chenko

2011

Powder Metall Met Ceram

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Rheological models for pressure sintering of powder materials are described. The rheological models of deformable bodies and the associated dynamic deformation theory for porous bodies based on the energy conservation law enable a quantitative description of their densification under impulse and static hot pressing as well as hot forging using crank presses. The simulation of compaction of porous metals shows that the viscosity of the matrix, that forms the porous body, and the activation energy of viscous deformation dramatically decrease with increasing initial impact velocity. This promotes the compaction of the material to practically nonporous state and improves its mechanical properties.

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“…So the deviatoric stress and the hydrostatic pressure both have effects on the yield of the materials. Micromechanical models or discrete models [5][6][7] can be used for powder or the porous materials. But the formulae of these models are complicated and need excessive parameters of materials, and there are difficulties in describing the geometry of the grains by the finite element method because the dimensions of powder grains are so small (about the order of 10 −5 m).…”

Section: Introductionmentioning

confidence: 99%

Finite Element Simulation of Cold Isostatic Pressing of the Selective Laser-Sintered Components

Shi

Wei

2010

Materials and Manufacturing Processes

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The article discusses the simulation of forming process of cold isostatic pressing of the selective laser-sintered components. A cylindrical specimen and a turbine component made of stainless steel powder were fabricated by this forming route. In order to achieve the purpose of the near net shape, the simulations of cold isostatic pressure were carried out. The simulations were based on the Drucker-Prager-Cap constitutive model. The properties of the metallic powder were measured by the experiments. The effect of a rubber bag on cold isostatic pressing is discussed. The results show that a rubber bag has little influence on both shape and size of the specimen. The results of the simulations show good agreement between the experimental results and the calculated results. The simulations can give a useful direction to the design of dimensions of the combined forming process of selective laser sintering and cold isostatic pressing. IntroductionSelective laser sintering (SLS) is a technology with the most potential among rapid prototyping (RP) technology that could manufacture complex parts of any type rapidly [1] and need not use tools and dies. Therefore, SLS has the advantages of short manufacturing cycle, low cost, and high efficiency, which are major advantages over traditional manufacturing technologies for metal parts. The polymer materials of low melting point such as polystyrene (PS) and polyamide (PA) are the main materials for SLS and the high level of porosity exists in the as-processed components. So the SLSed parts usually are infiltrated by low melting point metal or alloy, such as Cu, bronze, and brass, to fill the pores and improve the intensity. The forming of metallic powder materials by PR technology is becoming an important research field due to the enlarged application domain and high value of metal parts. Although metal parts of some alloy materials could be formed via selective laser melting (SLM), the laser power that SLM uses (that is, 100-200 W) is 10-20 times larger than that of SLS. And the laser scan rate of SLM is lower than 200 mm/s (usually the laser scan rate of SLS is 1,500-2,500 mm/s). These factors have led to high costs of SLM. And SLM is limited to the manufacture of small size and thin-walled workpieces. Forming material is also limited to Ti6Al4V, tool steel, ferroalloy, stainless steel, and TiC [2]. Cold isostatic pressing (CIP) can densify powder or porous parts. But when CIP is used alone, it cannot manufacture the complex parts because of the difficulties in manufacturing the bags.

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Strain hardening of a powder body in pressing

Cited by 19 publications

References 18 publications

Simulation of the compaction dynamics of Cu + Al2O3 powder mixture under impulse hot pressing

Simulation of the compaction dynamics of Cu + Al2O3 powder mixture under impulse hot pressing

Pressure sintering of powder materials

Finite Element Simulation of Cold Isostatic Pressing of the Selective Laser-Sintered Components

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