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Temperature, Hardness and Toughness

Temperature, Hardness and Toughness. Temperature Effects on Material Properties. Temperature changes and extremes affect the value of many engineering properties yield, modulus, toughness, corrosion resistance, creep, relaxation, viscosity, shrinkage, solubility….

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Temperature, Hardness and Toughness

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  1. Temperature, Hardness and Toughness

  2. Temperature Effects on Material Properties • Temperature changes and extremes affect the value of many engineering properties • yield, modulus, toughness, corrosion resistance, creep, relaxation, viscosity, shrinkage, solubility…..

  3. Temp Effect on Tensile Strength

  4. Temp Effect on Other Properties

  5. Thermal Expansion • Elevated Temperatures excite the electrons at the atomic level of any material • The excited atoms can more easily move to a lower energy state and change orientation of atomic planes • This leads to dimensional changes in most materials

  6. Temperature vs. Expansion • t is the coefficient of thermal expansion.

  7. Surface Properties • Hardness • Scratch hardness • Surface Hardness • Impact Energy

  8. 1 - Talc 2 - Gypsum 3 - Calcite (CaCO3) 4 - Flourite 5 - Apatite 6 - Orthoclase (Feldspar) 7 - Quartz 8 - Topaz 9 - Corundum (or sapphire) 10 - Diamond Hardness - Moh’s Scale • Moh scale is a surface scratch resistant scale based on minerals

  9. Surface Hardness • Surface hardness is quantified by determining the energy necessary to cause localized plastic deformation. • A specific energy is imparted on a surface of a material and the amount of plastic deformation is quantified in most hardness procedures. • Based on theory of plasticity.

  10. D d 120° Types of hardness tests • Brinell - 1900 - balloriginal hardness test • Rockwell - 1919, rounded cone most common, (ASTM E18)

  11. Use of hardness • Surface hardness of heat treated metals • Quality control of heat treatment process • Correlated with other properties • Yield strength • “Brittleness”

  12. Impact tests Charpy V-notch - Measure energy required to rupture specimen Izod V-notch - Same as Charpy but different specimen

  13. Ductile Impact Energy, Joules Brittle Temperature Use of impact resistance • Quantify resistance to dynamic impacts and crack sensitivity • Quantify the “transition temperature” of an alloy (ductile – brittle behavior)

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