NanoscienceMechanicalProperties

Cliquez pour modifier le style du titre,Cliquez pour modifier les styles du texte du masque,Deuxime niveau,Troisime niveau,Quatrime niveau,Cinquime niveau,*,Nanoscience: Mechanical Properties,Olivier Nguon,CHEM *7530/750,Feb 21st 2006,1,Outline,I. Classic Mechanical Properties,II. Nanostructured Materials,III. Conclusions and Applications,2,Tensile test,Determination of mechanical properties,Stress:,= F/S,Strain:,=,l / l,0,3,Tensile Test curve,Max stress: tensile strength,Max elasticity: Yield strength,Stress,(Mpa),Necking,Strain, (%),Elastic deformation,Plastic deformation,Fracture,Typical Tensile Test curve or Strain Stress curve,4,Modulus = slope,Strain,Elastic Deformation,Hookes law:,= E,E = Young modulus (Pa),Stiffness of material,Non linear models exist (visco-elastic behaviour),Stress,5,Mechanical properties,Yield strength: maximum stress before permanent strain,Tensile strength: maximum stress,Ductility: measure of deformation (L,f, L,o,)/ L,o,Toughness: ability to absorbe energy: area under curve,6,Hardness,Resistance to plastic deformation,Measure of depth or size of indentation,7,II. Nanostructured materials,8,Nanoparticles,Conventional materials: Grain size micron to mm,Nanoparticles increase grain boundaries,Influence on mechanical properties: Increased hardness, yield strength, elastic modulus, toughness,9,Comparison tensile curves,Comparison:,Al Mg cryomilled (20 nm),Al Mg ultra fine grain (80 nm),Al Mg coarse (2 mm),Cryomilling: Milling in liquid N,2,Ultrafine grain: electrodeposition,B. Han,Red.Adv.Mater.Sci,;,9,(2005) 1-16,10,Mechanical properties of nanomaterials compared to coarse grain materials,Higher Young modulus and tensile strength (to 4 times higher),Lower plastic deformation,More brittle,11,Strength and Hardness with grain size,Strength and Hardness of nanostructured material increases with decreasing size,Grain boundaries deformation,12,Comparison of Young modulus,Material,Young modulus (GPa),Rubber,0.1,Al,70,Fe,200,SiC,440,Fe nanoparticles (100 nm),800,C nanotubes,1000,Diamond,1200,13,Elongation nanostructured materials,Elongation decreased,Lower density of mobile dislocations,Short distance of dislocation movement,14,III. Conclusions,15,Mechanical properties,Mechanical properties: Strength, toughness, hardness increased,Materials more brittle,Due to increased grain boundaries density and less dislocations density,16,Important factors on mechanical properties,History,of the material:,Temperature, strain,: influence on amount of dislocations, grain size,Impurities,: segregate at high temperature and affect mechanical properties,17,Applications,Biomedical: bones, implants, etc.,High strength, strong, long-lasting materials: automotives, electronics, aerospace, etc.,Composites materials,18,