Theoretical design of calibration beams for strain gauge factor measuring apparatus

By starting with theoretical analysis and combining with the needs of practical applications, this article carries out a preliminary theoretical investigation of optimum design of the cross sectional shape and dimensions of calibration beams for strain gauge factor measuring apparatus. A new formula is derived in this paper that shows the quantitative relationship among strains on the beam surfaces, the strain non-uniformity within a certain range of the beam and beam thickness, which provides a theoretical basis for the accuracy improvement of the measuring apparatus and for correct application of the calibration beams, and also for drawing up and improving items concerning with calibration beams in strain gauge standards internationally. It is proven through experiments that the neutral axis of the bent calibration beam of rectangular cross section under pure bending moments is actually not circular but parabolic.