Lecture_6_Feb9_2012

Lecture_6_Feb9_2012 - Particle size, particle size...

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1 Particle size, particle Particle size, particle size distributions, and size distributions, and particle geometry are particle geometry are very important to the very important to the properties of your final properties of your final product! product! 7 February 2012 7 February 2012
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2 Particle size distributions Particle size distributions Technique PS Range Quantities Vibratory Screening mm - ~37μm Tons/hour Vibratory Screening ~2μm Grams/hour Water Classification (cyclone) 50 – 0.5 μm Tons/hour Quality Control Methods: Sedimenta tion ~0.1μm Grams/hour Laser Light Scattering 10 nm Grams/hour
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3 Screen Size Opening (μm) Mass (M i ) Cummulative Mass (Σm i ) 20 840 0 0 100 125 M 1 M 1 200 74 M 2 M 1 + M 2 325 44 M 3 M 1 + M 2 +M 3 400 37 M 4 M 1 + M 2 +M 3 +M 4 Catch Pan 0 M p M 1 + M 2 +M 3 +M 4 +M p Particle size distributions using the sieving method method 20 100 200 325 400 Catch Pan 840μm 125μm 74μm 44μm 37μm 0μm
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4 Let’s finish up atomic particle packing with Let’s finish up atomic particle packing with some examples some examples coarse fine For a close-packed FCC structure, the green bulk density is
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5 ISSUES TO ADDRESS. .. Stress and strain : What are they and why are they used instead of load and deformation? Elastic behavior: When loads are small, how much deformation occurs? What materials deform least? Plastic behavior: At what point does permanent deformation occur? What materials are most resistant to permanent deformation? Toughness and ductility : What are they and how do we measure them?
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6 Elastic means reversible ! 2. Small load F δ bonds stretch 1. Initial 3. Unload return to initial F δ Linear- elastic Non-Linear- elastic
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7 Plastic Deformation (Metals) Plastic Deformation (Metals) Plastic means permanent ! F δ linear elastic linear elastic δ plastic 1. Initial 2. Small load 3. Unload planes still sheared F δ elastic + plastic bonds stretch & planes shear δ plastic
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8 Stress has units: N/m 2 or lb f /in 2 Shear stress, τ : Area, A o F t F t F s F F F s τ = F s A o Tensile stress, σ : original area before loading σ = F t A o 2 f 2 m N or in lb = Area, A o F t F t
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9 Simple tension: cable τ Note: τ = M / A c R here. o σ = F A o τ = F s A σ σ M M A o 2 R F s A c Torsion (a form of shear): drive shaft Ski lift (photo courtesy P.M. Anderson) A o = cross sectional area (when unloaded) F F
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10 (photo courtesy P.M. Anderson) Canyon Bridge, Los Alamos, NM o σ = F A Simple compression: Note: compressive structure member ( σ < 0 here).
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Lecture_6_Feb9_2012 - Particle size, particle size...

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