1.The cut-off frequency of low-pass filtering for strain test data is 3kHz of sampling frequency of dynamic strain gauge.

2.As shown in the figure, if the strains at the measured point caused by axial tension, bending moment, torque and temperature are respectively represented by epsilon F, epsilon M, epsilon N and epsilon t, then the strains at the 45?Direction of the measured point caused by each strain gauge are respectively:

According to the circuit measuring principle, the total strain output by the resistance strain gauge is related to the strain of each bridge arm:

Torsional shear strain at 45 ° measured due to torque alone is:

From the material mechanics it can be obtained that the torsional shear stress caused by the torque of the drive shaft is:

Where G is the shear modulus of the material, G=E/2 (1+mu), E is the Young’s modulus and Mu is the Poisson ratio.