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Mechanical Properties of Glass

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Mechanical Properties of Glass

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    1. Mechanical Properties of Glass Elastic Modulus and Microhardness [Chapter 8 – The “Good Book”*] Strength and Toughness [Chapter 18] Fracture mechanics tests Fractography Stress Corrosion Fracture Statistics *A. Varshneya, “Fundamentals of Inorganic Glasses”, Society of Glass Technology (2006) jmech@mse.ufl.edu 1 Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13

    2. Early investigators observed the time dependence of the strength of glass jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 2

    3. Early History Grenet (1899) – First experiments to show that glass failed after time under load. Early studies 1920’s +(up to the development of fracture mechanics) (Preston, Milligan, Holland and Turner, Mould and Southwick, etc., etc.) depended on measurements of strength, and were therefore unable to separate effects of flaw severity from flaw extension. I felt that I must acknowledge those who came before and contributed significantly to the field. Shelley Wiederhorn, jack and I are completing a comprehensive historical perspective.I felt that I must acknowledge those who came before and contributed significantly to the field. Shelley Wiederhorn, jack and I are completing a comprehensive historical perspective.

    4. Progress Orowan (1944) - Recognized that the fracture energy of glass should be dependent on the environment in which it was measured. Gurney (1947) – Proposed that the strain at a crack tip made the material more chemically active. Gibbs and Cutler (1951); Stuart and Anderson (1953) – Use of chemical rate theory to explain environmentally enhanced crack growth. We start to see the beginning of understanding of the role of environment.We start to see the beginning of understanding of the role of environment.

    5. In 1947 Gurney presented thermodynamic concepts to explain moisture enhanced crack growth jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 5

    6. Abrasion decreases the strength of glass. Time under load decreases strength of glass. jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 6

    7. Mould and Southwick showed that cracks grow in time with applied stress jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 7

    8. Greater stressing rates increase strength jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 8

    9. In order to understand crack growth with time, you need to measure crack growth directly. jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 9

    10. First Use of Fracture Mechanics (Wiederhorn, J.Am.Cer.Soc., 50 407 (1967)) Double-cantilever-beam tests Soda-lime glass tested in N2 gas of different relative humidity Observed 3 crack growth regimes, each controlled by a different mechanism Glass microscope slides. Inexpensive, easy to machine to shape.Glass microscope slides. Inexpensive, easy to machine to shape.

    11. The constant moment DCB is often used. jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 11

    12. Water and stress enhance crack growth in glass jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 12

    13. Some glasses show “static” fatigue limits jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 13

    14. Slow crack growth is a thermally activated process jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Charge Conduction in Glass - Lecture 13 14

    15. Crack Tip pH is Important (Wiederhorn and Johnson, J.Am.Ceram.Soc. 56 192 (1973)

    16. Composition affects crack growth rate jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 16

    17. Crack sharpness is limited by the molecular structure of the glass jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 17

    19. Water and stress enhance crack growth in glass jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 19

    20. There is a theory on how stress corrosion occurs in glass. jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 20

    21. There is a change in (fracture) surface energy with the presence of some environments jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 12 21

    22. Stress Corrosion Susceptibility depends on composition and structure jmech@mse.ufl.edu Virtual Course on Glass - The Properties of Glass: Mechanical Properties of Glass - Lecture 13 22

    24. Many alcohols do not affect crack growth – it is the water content in the alcohol! 24

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