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Published byNehemiah Burdsall Modified about 1 year ago

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Grain Boundaries Ni-Base Superalloy Waspalloy 50µm high-angle grain boundary ( >15°) low-angle grain boundary

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Properties of Materials Mechanical Properties Elastic Plastic Viscoelastic Creep Testing methods

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The Tensile Test stress =F/A strain =l-l 0 /l 0

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The Tensile Test

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Elastic Deformation distance r r0r0 Force=dE/dr

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Elastic constants (isotropic case) Stress – strain / shear stress – shear strain Young’s modulus Shear modulus Poisson ratio In order to completely describe the elastic behavior of a solid 2 of these constants need to be known!

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Yield Strength Y strain offset yield-point phenomenon (C steels, dislocations are pinned by C) YY YY

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The Stress-Strain Curve stress strain necking engineering stress true stress

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Materials Selection Charts Strength [MPa] Density [1000kg/m³]

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Plastic Deformation – Dislocation Glide shear stress

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Plastic Deformation – Dislocation Glide =>macroscopic deformation

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Plastic Deformation – Dislocation Glide dislocation motion

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Plastic Deformation shear stress

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Some concluding words on dislocations Strengthening mechanisms Grain size reduction (Hall-Petch equation) Solid solution strengthening Strain hardening

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Mechanical testing Hardness Vickers Rockwell … Nanoindentation Ductility Toughness Creep Fatigue

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Vickers Microhardness Testing length of the diagonals d 1 and d 2

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Rockwell Hardness Testing (HRC) scale indenter (120° diamond pyramid) specimen

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Ductility stress strain %EL, percent elongation %RA, percent reduction in area brittle ductile

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Charpy Impact Testing hammer impact energy A v =mg(h-h´) specific a k =A v /A 0 (DIN 50115)

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T-Dependence of Av BDTT

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Cleavage Fracture at Low Temperatures

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Deformation at Elevated Temperatures: Creep

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Creep Testing d dt

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Fatigue Loading during Service

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Fatigue Testing

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push-pull rotating-bending counter load servohydraulic actuator

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Fatigue-Testing: The S/N Diagram stress amplitude [MPa] cycles to failure N fatigue limit total life design

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Fracture Mechanics K Ic represents resistance to brittle fracture [MPam 0.5 ]

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Determination of K Ic using Compact Tension (CT specimens) extensometer force displacement

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