Ring-Core Residual Stress Measurement: Analysis of Calibration Coefficients for Incremental Strain Method

Adam Civín, Miloš Vlk


Correctly determined and properly used
calibration coefficients for a residual stress measurement
by ring-core method (RCM) are essential. Knowledge of
their dependence on the disposition of residual state of
stress cross the depth of metallic material gives results
correspond of theirs appropriate application. In this
article, incremental strain method (ISM) is used for
determination of the calibration coefficients K1 and K2
under uniaxial and biaxial state of stress conditions. Finite
element method (FEM) has been used in order to calculate
relieved residual strains on the top of the core. Calculated
calibration coefficients are plotted on graphs in
dependence on the drilled depth and character of the
residual stress state. Appropriate polynomial functions
have been interposed by these points. We conclude that
values of calibration coefficients K1 and K2 determined by
the incremental strain method can be used only for
homogenous residual states of stress. Examination of
linearly varying state of stress indicates inaccurate results
increasing with the depth of drilled groove.


calibration coefficient; incremental strain method; residual stress; ring-core method; strain gauge

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ISSN 1801-1217 (Print)
ISSN 1805-9422 (Online)
Published by the Czech Technical University in Prague, Faculty of Mechanical Engineering