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Journal of Materials Science

, Volume 18, Issue 9, pp 2785–2797 | Cite as

Kinetics of shear-activated indentation crack initiation in soda-lime glass

  • B. R. Lawn
  • T. P. Dabbs
  • Carolyn J. Fairbanks
Papers

Abstract

The initiation of radial cracks in Vickers indentation of soda-lime glass is found to be strongly rate dependent. For long contact durations the radial cracks pop in during the indentation event, at a reproducible stage of the unloading half-cycle; for short contacts the pop-in occurs after the event, with considerable scatter in delay time. The phenomenon is interpreted in terms of an incubation time to develop a critical nucleus for the ensuing fracture. Increasing either the water content of the environment or the peak contact load diminishes the incubation time. Scanning electron microscopy of the indentation patterns indicates that the sources of the crack nuclei are constrained shear faults within the deformation zone. A qualitative model is developed in terms of a two-step process, precursor faulting followed by crack growth to pop-in instability. Moisture may influence both these steps, in the first by interfacial decohesion and in the second by slow crack growth. No definitive conclusion is reached as to which of the steps is ratecontrolling, although it appears that it is the shear across the fault and not the tension across the crack which is vital in driving the initiation. The implications of these results in connection with the basic mechanical properties of brittle solids, particularly strength, are considered.

Keywords

Crack Initiation Deformation Zone Reproducible Stage Critical Nucleus Radial Crack 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Chapman and Hall Ltd. 1983

Authors and Affiliations

  • B. R. Lawn
    • 1
  • T. P. Dabbs
    • 1
  • Carolyn J. Fairbanks
    • 1
  1. 1.Center for Materials ScienceNational Bureau of StandardsWashington, DCUSA

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