LECTURE 29 3 11 MECHANICS OF MATERIALS F03 INSTRUCTOR Professor Christine Ortiz OFFICE 13 4022 PHONE 452 3084 WWW http web mit edu cortiz www PLASTICITY IN POLYMERS I SUMMARY LAST LECTURE II Deformation Energies Mechanical or Deformational Energy U d 0 Modulus of Resilience or Elastic Strain Energy U MOR Y 0 E d Y Y 2 2 2 f Modulus of Toughness U MOT d 0 Plastic Work of Fracture U PLASTIC Elastic Energy Released on Fracture U ELASTIC Y failure failure failure UMOT U plastic U elastic UMOR 0 002 Y f II Molecular Origins of Plasticity in Metals edge and screw dislocations 2 D and 3 D movement of dislocations slip systems planes directions critical resolved shear stress polycrystalline plastic deformation p residual 2 PLASTIC DEFORMATION IN SINGLE CRYSTALS F slip planes slip direction edge dislocations F Polycrystalline Plastic Deformation http www jwave vt edu crcd farkas lectures dislocations tsld022 htm Stress versus Strain Curve For Various Types of Polymers I II III IV Structure of Semicrystalline Polymers lamellae Structure of Semicrystalline Polymers II http web utk edu kit 201 Transmitted polarized light micrograph of polypropylene spherulites 167 X Stress versus Strain Curve For Semicrystalline Polymers VIII max Y II VII III IV V VI I Lo f Stress versus Strain Curve For Semicrystalline Polymers Plastic Deformation of Semicrystalline Polymers Plastic Deformation of Amorphous Glassy Polymers T Tg Crazing in Amorphous Glassy Polymers T Tg Crazing in Amorphous Glassy Polymers T Tg craze bulk bulk CRAZE craze bulk interface NANO STRUCTURE main fibril cross tie fibril fibril oriented polymer chains entanglement Crazing in Amorphous Glassy Polymers T Tg Shear DZ s in Amorphous Glassy Polymers T Tg Macroscopic sample necking Microscopic structure CRAZING OR SHEAR DZ s
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