The effect of short range order on the thermal output and gage factor of Ni3FeCr strain gages

The ability of alloy 70Ni‐27.5Fe‐2.5Cr to form an ordered crystalline structure upon application of elevated temperature and the resulting effects on a variety of physical properties such as magnetism, strength, electrical resistance, and specific heat are well known. This paper demonstrates that strain gages made with 70Ni‐27.5Fe‐2.5Cr foil with an ordered crystalline structure have both high gage factors and high thermal outputs. The thermal output for strain gages made of 70Ni‐27.5Fe‐2.5Cr foil is demonstrated to be about 1,374 μΩ/Ω/K. The gage factor is nonlinear ranging in magnitude from about 5.0 to 3.6 for applied strains of 300 and 1,300 μE, respectively. The magnitude of gage factor and thermal output correspond with transformation of the crystalline structure from a state of disorder to a state of order. Comparisons to strain gages made with 36Ni‐57Fe‐7Cr foil are provided because of its use in the manufacturing of metal foil strain gages and their demonstrated high gage factors and high thermal outputs. Practical application for 70Ni‐27.5Fe‐2.5Cr strain gages is demonstrated by dead‐weight loading of shear‐beam load cells at low applied strain levels to minimise the effect of nonlinear gage factor; and Wheatstone bridge cancellation of high thermal output.