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A prototype for a resistive extensometer as a strain measuring standard
Author(s) -
Bergqvist B.,
Scherling G.
Publication year - 1987
Publication title -
strain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.477
H-Index - 47
eISSN - 1475-1305
pISSN - 0039-2103
DOI - 10.1111/j.1475-1305.1987.tb00641.x
Subject(s) - extensometer , strain gauge , resistive touchscreen , materials science , calibration , structural engineering , conical surface , beam (structure) , deflection (physics) , composite material , electrical engineering , optics , engineering , mathematics , physics , statistics
The design, handling and calibration of a prototype to a resistive extensometer with 10 mm measuring length is described. It stands on the test specimen via pins with conical tips. These end in hard metal spherical calottes with 16 micron nose radius. The manufacturing and maintenance of these tips was described earlier. The extensometer is calibrated on a bending beam to 1 mm/m strain, using the loading and deflection equipment developed at the FFA and described earlier. The total extensometer inaccuracy, i.e. the sum of estimated systematic errors and random errors, the latter expressed as the 2σ confidence interval about the mean, is about 400 × 10 ‐4 %, for 60 reproduced calibration tests. With the extensometer, it was shown that the beam, which was machined and hardened from an alloy with 1.4% Cr and 1.4% Ni and has a moderate hardness of H v 430, does not show any kind of inhomogeneity in Young's modulus, within the resolution of the indicator. Therefore, the extensometer is suitable for the determination of bonded resistance gauge factors, even if a total error of only ±0.1% is required. The prototype described can therefore be used as a strain measuring standard.