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Application of Materials

Application of Materials. Part II, Engineering materials. Structural strength. Strenth of Materials. Stiffness. Reliability. Lifetime. Strength of materials. Properties determined at tensile/compression tests. Permanent elongation. Total elongation. Criteria for materials selection.

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Application of Materials

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  1. Application of Materials Part II, Engineering materials

  2. Structural strength Strenth of Materials Stiffness Reliability Lifetime

  3. Strength of materials Properties determined at tensile/compression tests Permanent elongation Total elongation

  4. Criteria for materials selection • plastic materials – yield strength (yield limit) – Re, Rp (Rec, Rpc) • brittle materials – strength limit – Rm (Rmc), Rm/ Classification of materials (Re, Rp0,2) • low strength < 250 N/mm2 • medium strength 250...750 N/mm2 • high strength 750...1500 N/mm2 • super high strength > 1500 N/mm2

  5. Stress concentration

  6. Stiffness Stiffness D = Ex K(geometric characteristic of cross-section) At tension K = S (cross-section area) At bending K = I (moment of inertia) I = bh3/3 Modulus of elasticity Normal Shear Volume

  7. Modulus of elasticity

  8. Reliability (1) Toughness – notch impact energy KU or KV, J – fracture toughness KC, N/mm2  m1/2 Ductile fracture % TDBT T’DBT TDBT T  KU, KV – cold brittleness TDBT – ductile-to-brittle transition

  9. Reliability (2) Influence of C, ordinary and alloying elements to KU TDBT TDBT TDBT el steel normal cold worked cold worked TDBTC TDBTC

  10. Reliability (3) Ductile-to-brittle transition T50, C % of alloying elements

  11. Reliability (4) Dependence of M toughness of A-grain size KU, J Dependence of KU/KV on temperature low strength KU, KV high strength Grain no. T

  12. Fine and coarse grain steels 1 – killed steel 2 – rimmed steel

  13. Influence of microalloying elements V Grain size of ferrite, m2 Ti Nb Alloying elements, %

  14. Plane strain fracture toughness K1c At tension K1c Coefficient of stress intensity [MPam1/2]

  15. Low-alloyed highly tempered steels Relationship between K1c and yield strength Superplastic steels Fracture toughness K1c, MPa  m1/2 Maraging steels Precipitation hardened stainless steels Yield strength, MPa

  16. Life time (1) R (R = min/max) -1 – symmetric loading Fatigue Impactors: - surface roughness - stress state - stress concentrations Steels N = 107 Nonferrous alloys N = 108

  17. Life time (2)

  18. Life time (3) Creep  = f(, T, t) • low temperature T/Tm < 0.5 • high temperature T/Tm > 0.5 Impactors • structure • alloying (super creep alloys) – • TMT

  19. Corrosion Modes of corrosion in dry gases in organic liquids Chemical in water containing environments in melt electrolytes Electrochemical Biochemical

  20. Types of corrosion Types of corrosion: a – uniform b – nonuniform c – selective d – spotted e – pitting f – dotted g – under surface h – intercrystal i - stress

  21. Chemical corrosion of metals (1) 2 Mg + O2 = 2 MgO 2 Fe + 3 O2 = Fe2O3 For protection Voxide > Vmetal Kui Voxide/Vmetal> 1 – Cd, Al, Ti, Zr, Zn, Ni, Cr, Fe At high Voks / Vmet (1,2…2,0)  cracking High temperature corrosion T  1000 C – oxide layer  electroconductive

  22. Chemical corrosion of metals (2) Corrosion influencing parameters • structure • surface treatment materials parameters • internal stresses • T • gas composition • velocity environmental parameters • heating parameters

  23. Chemical corrosion of metals (3) Protection • alloying ( ) • coatings • protective atmosphere (at heat treatment) (H2 + N2 + H2O; CO + CO2 + N2; etc.)

  24. Electrochemical corrosion of metals (1) Moisture + H2S, Co2, So2, NaCl  electrolyte metals  galvanic pair

  25. Electrochemical corrosion of metals (2) Microgalvanic pairs at steels Atmosphere Moisture film Metal

  26. Electrochemical corrosion of metals (3) Protection (1) • Selection of materials Table: Allowed contacts of metals

  27. Protection (2) • Protective coatings - metallic (less active metals (Cu, Ni, Sn, Ag) – up to coating must be undamage; active (Zn, Co) – protection up to end) - paints, lubricants • other - cathodic protection - protector protection - anodic protection - corrosion inhibitors (high molecular matters)

  28. Wear Modes of wear Mechanical Corrosive-mechanical Adhesive -abrasion -oxidizing wear -erosion -fretting corrosive wear -cavitation -fatigue wear

  29. Method for wear protection • hardening, thermo-chemical treatment • overwelding • surface alloying • coating (chemical, thermo-chemical, thermally sprayed, PVD, CVD, mechanical) • selection of pairs (by adhesion)

  30. Wear testing methods

  31. Material groups Metals Cermets MCM Ceramics CCM Glass-ceramics Composites GCCM PCM FRG Polymers Glass MCM Metal composite materials CCM Ceramic composite material PCM Polymeric composite material GCCM Glass-ceramic composite material FRG Fiber-reinforced glass

  32. Specific strength of materials (1)

  33. Specific strength of materials (2)

  34. Basic physical and mechanical properties of construction materials (1)

  35. Basic physical and mechanical properties of construction materials (2)

  36. Thank you for attention priit.kulu@ttu.ee

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