Unformatted text preview: ENGRI 111 ENGRI Mechanical Response Si: Covalent bonds Metal: Metallic bonds Polymer: Covalent and van der Waals bonds Plastic deformation: material “yields” to applied stress Elastic stretching: recoverable Young’s Modulus (Modulus of Elasticity), E = σ/ε Different Behaviors Different Metallic Bonds: Metal Ions in Sea of Electrons Metallic ATOMIC SCALE: BONDS ACT LIKE ELASTIC SPRINGS www.matsceng.ohio-state.edu Plastic Deformation Plastic www.matsceng.ohio-state.edu Knee Dislocation Knee Atoms and Planes Atoms Close Packed Planes Close (Edge) Dislocation (Edge) (Edge) Dislocation (Edge) www.msm.cam.ac.uk Dislocations & Caterpillars Dislocations Slip: deformation of material by movement of dislocations through special planes Grains and Grain Boundaries Grains Dislocation Pile-up Dislocation Additional stress needs to be applied to make dislocations move through the grain boundary Yield strength ≡ 1/√d Is There a Limit? Is Is Nano Better?
When grains become too small mechanism changes from intragrain slip to grain boundary sliding Melting of Metal Nanoparticles Low Cost Disposable Electronics RFID Tags Flexible Displays www.nanomas.com Sintering (fusing) of nanoparticles at lower T ...
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- Fall '07
- Plasticity, Knee dislocation, Dislocation (Edge)