On the Significance of the Supports when Calibrating Strain Gauge Installations for Measuring Loads on Aircraft

摘要

When calibrating strain gauge installations for measuring flight loads in the way suggested by Skopinski and others, the strain distribution and hence the gauge responses resulting from the application of a load to part of the structure will be affected by the position of the supports on which the aircraft rests. It is, however, shown that if the aircraft is supported so that the reactions are statically determinate, the response of any strain gauge to a particular loading system is the integral of the products of the elemental loads imposed by that system and the gauge responses obtained from the ground test. In consequence, the theoretical linear combination of strain gauges which measures exactly the load sustained by the structure and which is based on data obtained from the ground test is invariant with changes in the positions of the supports and thus may be used to measure loads applied in flight or in any other condition. In practice, the positions of the supports should be chosen with due regard for the strength and stability characteristics of the structure and for the idiosyncracies of the strain gauge responses. (Author)