Stress measurement with non-indentation Page: 1 of 8
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O RNL/C P-99248
STRESS MEASUREMENT WITH NANO-INDENTATION
LF l9c6?O -
MIE, University of Massachusetts, Amherst, MA, 01003, USA
Neal D. EVANS
Metals and Ceramics Div., Oak Ridge National Laboratory, Bldg. 5500, MS
6376, Oak Ridge, TN, 37831-6376, USA
Jack C. HAY
IBM Research, T. J. Watson Research Center, PO Box 218, Yorktown Heights,
NY, 10598, USA
The feasibility of using nano-indentation to measure residual stress in glasses
was studied. Indents were placed on the side of flexure specimens at four dif-
ferent distances from the neutral axis while the specimens were under load in
four-point-bending. Three different glasses (soda-lime, boro-silicate, and fused
silica) were indented with a cube-corner indenter using 2 to 30 mN indentation
loads. A high resolution scanning electron microscope was used to measure the
length of the cracks emanating from the corners of the indents while the speci-
men remained under load. The measured crack lengths were correlated to the
local stress using indentation theory. For the correlation, elastic beam theory
was used to calculate the magnitude of the local stress at the indentation sites.
Results derived from crack lengths were in good agreement with local stress
within experimental scatter. However, this scatter was found to be rather large
as a result of the stochastic nature of crack formation. It can be concluded from
this study that nano-indentation can be used to measure residual surface
stresses with high spatial resolution provided that a sufficient number of in-
dents are used to assure good statistical accuracy.
Indentation techniques to measure mechanical properties of brittle materials ;'
has gained wide spread acceptance in the ceramics community due to their relative.
simplicity and reasonable accuracy. These measurement techniques evolved from
the pioneering work of such investigators as B. R. Lawn, M. V. Swain, E. R. Full
A. G. Evans, and others whose contribution to the development of the indentation
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Jakus, K.; Evans, N.D. & Hay, J.C. Stress measurement with non-indentation, report, November 1998; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc702873/m1/1/: accessed April 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.