Energy Absorption at Particle Contact, Compression, and Shear Flow of Dry Ultrafine Powder

ISSN： 0272-6351

Source： Particulate Science and Technology, Vol.27, Iss.4, 2009-07, pp. : 337-351

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Abstract

The mechanical behavior of dry, ultrafine cohesive powders (particle size d < 10 μm) is="" characterized="" by="" insufficient="" flowability="" and="" large="" compressibility.="" consequently,="" a="" comparatively="" large="" energy="" input="" is="" necessary="" to="" promote="" the="" non-rapid="" frictional="" shear="" flow="" in="" powder="" handling="" practice.="" a="" micro-mechanical="" approach="" is="" briefly="" explained="" first.="" when="" two="" adhesive="" particles="" come="" in="" contact,="" the="" constitutive="" models="" of="" four="" characteristic="" stressing="" modes,="" namely,="" normal="" compression="" and="" detachment="" (tension),="" tangential="" sliding,="" rolling="" moment,="" and="" spinning="" (torsion)="" are="" modeled.="" next,="" the="" consequences="" of="" elastic-dissipative,="" elastic-plastic,="" frictional="" unloading="" and="" reloading="" paths="" of="" normal="" and="" tangential="" contact="" forces,="" rolling,="" and="" torsional="" contact="" moments="" are="" discussed="" with="" respect="" to="" energy="" absorption.="" the="" total="" microscopic="" energy="" absorption="" comprises="" contributions="" by="" elastic-dissipative="" hysteresis="" due="" to="" microslip="" within="" the="" contact="" plane="" and="" by="" fully="" developed="" friction="" work="" when="" the="" friction="" limits="" of="" displacements="" are="" exceeded="" during="" contact="" sliding,="" particle="" rolling,="" or="" rotation.="" with="" increasing="" contact="" flattening="" by="" normal="" load,="" these="" friction="" limits,="" hysteresis,="" and="" friction="" work="" increase.="" these="" microscopic="" data="" are="" in="" agreement="" with="" the="" macroscopic="" specific="" compression="" and="" shear="" work="" of="" limestone="" powder="" obtained="" by="" shear="" tests.="" thus,="" understanding="" of="" the="" micro-mechanics="" of="" particle="" adhesion="" is="" essential="" to="" assess="" macroscopic="" powder="" product="" quality="" and="" to="" improve="" process="" performance="" in="" particle="" technology.="">