From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The calibration of 'Ess-strip' strain gages and the design of a dynamic calibrator.
| Identifier | ExFiles\Box 168b\1\ img169 | |
| Date | 17th February 1939 guessed | |
| gages of the "Ess-strip" type, gave calibration factors ranging from 40 per cent below to 35 per cent above the dynamic calibration factors. The effect of temperature variations and of time under load were found to be sufficient to render this type of strain gage very much inferior to accepted gages such as the Tuckerman optical strain gage or the Huggenberger extensometer in those cases where static strains on a large structure are to be measured. "The dynamic calibrations of "Ess-strips", which were made by attaching the gage to a propeller blade and then vibrating this blade in resonance, had indicated the need for a calibrator that would subject the strips to uniform sinusoidal strains of sufficient amplitude and of a frequency that could be varied over a wider range than the restricted number of resonance frequencies (30 to 100 cycles per second) that could be set up in the propeller blades. A device was accordingly designed for calibrating dynamic-strain gages up to 8 inches in length by subjecting them to uniform sinusoidal strains up to 0.001 at frequencies ranging from 10 to 200 cycles per second. This device is now being constructed." ----------------- | ||