Strain gage evaluation with four-point bending at moderate temperatures

Abstract

This paper describes the application of the traditional four-point bending technique to conduct strain gage performance tests at moderate temperatures. The tests measure the apparent strain, linearity, drift, creep and hysteresis behavior to ascertain the reliability of strain gages to be used in the testing of experimental cylindrical vessels subjected to thermal loading. The four-point bending rig was designed to take advantage of the advances in personal computer datalogging and graphical processing software. The test rig is designed to provide a thermal barrier to minimize the heat losses and thermal isolation of the test beam while maintaining structural continuity. A low wattage and lightweight electric foil heater incorporating a precise temperature controller minimizes weight and enhances temperature stability. Gage performance data on five "candidate" strain gages at temperatures ranging from ambient to 215~ (419~ are presented, and the evaluation procedure is outlined. The strain gage with the most acceptable performance was identified within the validity limits from ambient to a temperature of 215~ and from zero to a maximum strain of 1000 tx~.

Horizontal vessels on fixed supports used for storing high-temperature liquid: An experimental validation of finite element modelling

“…On the basis of this work the foil gauge, series QF from Tokyo Sokki Kenkyujo Company Limited (TML) in Japan, were chosen, since they were found to have excellent characteristics and low drift up to 250 8C. The apparent strain characteristics measured in these tests on the vessel were very similar to those given in reference [13] for the QF series of gauges.…”

“…The early experimental work [5] and the strain gauge evaluation work by Ng and Wey [13] indicated that experimental work conducted at even moderately high temperatures was always going to be difficult. There was the hazardous and dangerous nature of the heating medium, in the present case hot oil at, say, 250 8C.…”

“…The strains recorded by the gauges on the plate were used for compensating strain drift due to the influence of temperature on the gauges on the vessel shell. One of the present authors and a co-worker [13] carried out an extensive series of measurements to examine the performance of a range of elevated temperature strain gauges. On the basis of this work the foil gauge, series QF from Tokyo Sokki Kenkyujo Company Limited (TML) in Japan, were chosen, since they were found to have excellent characteristics and low drift up to 250 8C.…”