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MATSE 259

MATSE 259. Lecture 4: Plastic Deformation Christopher L. Muhlstein, Ph.D. Department of Materials Science and Engineering The Pennsylvania State University University Park, PA. Last Lecture. Elastic behavior of materials Trends in elastic properties Elastic deformation calculations.

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MATSE 259

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  1. MATSE 259 Lecture 4: Plastic Deformation Christopher L. Muhlstein, Ph.D. Department of Materials Science and Engineering The Pennsylvania State University University Park, PA

  2. Last Lecture • Elastic behavior of materials • Trends in elastic properties • Elastic deformation calculations

  3. Lecture 4: Key Concepts and References • Plastic deformation • Yielding • Tensile strength • Ductility • elongation • reduction in area • Resilience • Toughness • True stress and strain • Reference: Chapter 6 of Callister

  4. Tensile Deformation • Proportional limit (onset of plastic deformation) • Yield strength, sy • 0.2% offset Callister, Materials Science and Engineering: An Introduction (2003)

  5. Anatomy of an Engineering Stress-Strain Curve • Elastic modulus • Yielding behavior • Ultimate strength • Fracture/failure strain Stress-strain diagram for a ductile steel. (after Balan et al., J. Eng. Struct., No. 3 March 1998, Vol. 124). Popov, Engineering Mechanics of Solids (1991)

  6. True Stress and Strain • True stress, st • True strain, et • Plastic deformation • Constant volume (isochoric) • Constitutive law

  7. Tensile Deformation • Ultimate tensile stress/strength (sUTS or TS) • Necking Fracture stress/strength (sF) Callister, Materials Science and Engineering: An Introduction (2003)

  8. Tensile Behavior of Steels • Features • Elastic response • Yielding behavior • Ultimate strength • Failure • Influence of alloy chemistry Popov, Engineering Mechanics of Solids (1991)

  9. Resilience and Toughness • Resilience, Ur • Ductility • Percent elongation, %EL • Percent reduction in area, %RA • “Toughness”

  10. Example Problem • Cylindrical specimen • 10 mm diameter • 101.6 mm long • Tensile force 10,000 N • E = 93.8 GPa • n = 0.35 • Specimen elongation? • Reduction in diameter? • Elastic or plastic deformation? Tensile behavior of brass. Callister, Materials Science and Engineering: An Introduction (2003)

  11. Example Problem • Cylindrical metal specimen pulled in tension to failure • d0 = 12.8 mm • l0 = 50.8 mm • df = 6.6 mm • lf = 72.14 mm • What are %EL, %RA, and true strain to failure?

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