No abstract

Material property studies frequently require the measurement of load and strain. Accurate measurement of both parameters is essential. Methods for accurate static calibration and verification of load transducers and extensometers are well established. More recently, standard practices have been developed for the dynamic calibration of load transducers. Still in its infancy is a standard method for dynamic verification of extensometers. Dynamic verification introduces a wide range of new issues. These encompass not only the transducer but also the conditioning electronics and actual test machine. Static calibration permits the “elimination” of nearly all dynamics, whereas dynamic verification must be done in the presence of these dynamic effects. This paper outlines the various concepts that need to be understood when performing the dynamic verification of an extensometer. Problems related to computer aided verification are emphasized, issues of aliasing and resolution in particular.

No abstract

No abstract

Verification and calibration of an extensometer requires operation at multiple points within the desired operating range. Whereas static calibrations observe changes in sensitivity at different levels within the transducer operating range, dynamic calibrations require duplicating that range of test levels for a range of operating frequencies. Additionally, although the static accuracy of an extensometer is relatively independent of the test machine, dynamic accuracy was believed to be quite dependent. Test results for dynamic verification of several extensometers are presented. The focus of the tests was to gain an understanding of the advantages and disadvantages of different methods of verification. Testing was generally in accordance with ASTM E 467, Practice for Verification of Constant Amplitude Dynamic Loads in An Axial Load Fatigue Testing Machine. Two excitation methods were used: discrete frequency and pseudo-random. Evaluation of a proposed revision to ASTM E 467 is included. Use of a computer to provide an efficient, high-accuracy method of verifying the calibration of an extensometer was explored. Further testing is recommended to determine if extensometer dynamic verification must be done on the actual test setup, and to what extent it is repeatable.