1 / 18

Nanoscience: Mechanical Properties

Nanoscience: Mechanical Properties. Olivier Nguon CHEM *7530/750 Feb 21st 2006. Outline. I. Classic Mechanical Properties II. Nanostructured Materials III. Conclusions and Applications. Tensile test. Determination of mechanical properties Stress: σ = F/S Strain: ε = Δ l / l 0.

orlando
Download Presentation

Nanoscience: Mechanical Properties

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Nanoscience: Mechanical Properties Olivier Nguon CHEM *7530/750 Feb 21st 2006

  2. Outline • I. Classic Mechanical Properties • II. Nanostructured Materials • III. Conclusions and Applications

  3. Tensile test • Determination of mechanical properties • Stress: σ = F/S • Strain: ε = Δl / l0

  4. Stress, σ (Mpa) Max stress : tensile strength Necking Max elasticity: Yield strength Fracture Strain, ε (%) Elastic deformation Plastic deformation Tensile Test curve Typical Tensile Test curve or Strain Stress curve

  5. Modulus = slope Strain Elastic Deformation • Hooke’s law: σ = E ε • E = Young modulus (Pa) • Stiffness of material • Non linear models exist (visco-elastic behaviour) Stress, σ

  6. Mechanical properties • Yield strength: maximum stress before permanent strain • Tensile strength: maximum stress • Ductility: measure of deformation (Lf – Lo)/ Lo • Toughness: ability to absorbe energy: area under curve

  7. Hardness • Resistance to plastic deformation • Measure of depth or size of indentation

  8. II. Nanostructured materials

  9. Nanoparticles • Conventional materials: Grain size micron to mm • Nanoparticles increase grain boundaries • Influence on mechanical properties: Increased hardness, yield strength, elastic modulus, toughness

  10. 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 N2 • Ultrafine grain: electrodeposition B. Han, Red.Adv.Mater.Sci; 9 (2005) 1-16

  11. Mechanical properties of nanomaterials compared to coarse grain materials • Higher Young modulus and tensile strength (to 4 times higher) • Lower plastic deformation • More brittle

  12. Strength and Hardness with grain size • Strength and Hardness of nanostructured material increases with decreasing size • Grain boundaries deformation

  13. Comparison of Young modulus

  14. Elongation nanostructured materials • Elongation decreased • Lower density of mobile dislocations • Short distance of dislocation movement

  15. III. Conclusions

  16. Mechanical properties • Mechanical properties: Strength, toughness, hardness increased • Materials more brittle • Due to increased grain boundaries density and less dislocations density

  17. 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

  18. Applications • Biomedical: bones, implants, etc. • High strength, strong, long-lasting materials: automotives, electronics, aerospace, etc. • Composites materials

More Related