The purpose of this research is the estimation of the measurement uncertainties obtained with strain gauges. A numerical method is proposed and allows the estimation of a strain range in which experimental measures should statistically take place, taking in account measurement errors and uncertainties caused by the technological characteristics of the gauge and its location. To this end, the proposed method is based on displacement fields obtained by Finite Element (FE) analyses of the studied part. Then, this method is validated by experimental measurements performed on specimens loaded in tensile-compression. The correlation between the measured strains and the strains estimated by our method permits its validation. Finally, the method is applied to a complex structure: a Francis hydraulic turbine runner, on which in situ measurements were made. Strains obtained by the proposed method are compared with the experimental measures and the strains estimated by FE analyzes. The method can be used to validate – or not – the FE models.
Measurement uncertainties depend mainly on the dimensions of the gauge and on the displacement fields in its neighborhood; the evaluation of the errors and uncertainties in positioning is also pertinent. Strain gauge measurements have a large number of uncertainty ources and only the most influential are studied here. The others are considered as controlled or negligible.
The proposed method can be applied to any type of mechanical structure. However, it uses the results from FE analyses and it is essential to realize that they also have their own uncertainties. For further researches, it could be interesting to study the uncertainties of the FE method in order to take them into account in the proposed method. Also, it could be possible to study and integrate other measurement uncertainty sources (high pressure, curved surface, etc.) in the proposed method. Finally the method could be adapted to other experimental sensors.
| Date | 7 Dec 2012 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Antoine Tahan (Supervisor) & André Coutu (Co-supervisor) |
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Arpin-Pont, J. (Author),
Tahan (Supervisor) & Coutu (Co-supervisor),
7 Dec 2012Student thesis: Master's thesis › Master in Engineering: Mechanical Engineering