Lec13p.MechanicsOfMaterialsII

Lec13p.MechanicsOfMaterialsII - EE 245: Introduction to...

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1 EE 245: Introduction to MEMS Lecture 13: Mechanics of Materials II CTN 10/6/09 Copyright © 2009 Regents of the University of California EE C245 : Introduction to MEMS Design LecM 7 C. Nguyen 9/28/07 21 MEMS Material Properties EE C245 : Introduction to MEMS Design LecM 7 C. Nguyen 9/28/07 22 Material Properties for MEMS [Mark Spearing, MIT] (E/ ρ ) is acoustic velocity EE C245 : Introduction to MEMS Design LecM 7 C. Nguyen 9/28/07 23 Young’s Modulus Versus Density [Ashby, Mechanics of Materials, Pergamon, 1992] Lines of constant acoustic velocity EE C245 : Introduction to MEMS Design LecM 7 C. Nguyen 9/28/07 24 Yield Strength Definition : the stress at which a material experiences significant plastic deformation (defined at 0.2% offset pt.) Below the yield point : material deforms elastically returns to its original shape when the applied stress is removed Beyond the yield point : some fraction of the deformation is permanent and non-reversible True Elastic Limit : lowest stress at which dislocations move Proportionality Limit : point at which curve goes nonlinear Elastic Limit : stress at which permanent deformation begins Yield Strength : defined at 0.2% offset pt.
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2 EE 245: Introduction to MEMS Lecture 13: Mechanics of Materials II CTN 10/6/09 Copyright © 2009 Regents of the University of California EE C245 : Introduction to MEMS Design LecM 7 C. Nguyen 9/28/07 25 Yield Strength (cont.) Below : typical stress vs. strain curves for brittle (e.g., Si) and ductile (e.g. steel) materials Stress Tensile Strength Fracture Ductile (Mild Steel) Brittle (Si) Proportional Limit Strain [Maluf] (Si @ T=30 o C) (or Si @ T>900 o C) EE C245 : Introduction to MEMS Design LecM 7 C. Nguyen 9/28/07 26 Young’s Modulus and Useful Strength EE C245 : Introduction to MEMS Design LecM 7 C. Nguyen 9/28/07 27 Young’s Modulus Versus Strength [Ashby, Mechanics of Materials, Pergamon, 1992] Lines of constant maximum strain EE C245 : Introduction to MEMS Design LecM 7 C. Nguyen 9/28/07 28 Quality Factor (or Q)
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3 EE 245: Introduction to MEMS Lecture 13: Mechanics of Materials II CTN 10/6/09 Copyright © 2009 Regents of the University of California EE C245 : Introduction to MEMS Design LecM 7 C. Nguyen
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This note was uploaded on 10/31/2010 for the course C 218 taught by Professor Clarknguyen during the Fall '09 term at University of California, Berkeley.

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Lec13p.MechanicsOfMaterialsII - EE 245: Introduction to...

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