ANALYSIS OF TEST STRAIN IN A FOUR-POINT BENDING CALIBRATION SETUP FOR STRAIN GAGES

Strain analysis is of particular importance in experimental mechanics. For the measurement of very small strains, strain gages are often used due to their outstanding precision and accuracy. Thus, the calibration of strain gages (gage factor determination) is to be done considering high requirements. Therefore, a four-point bending setup is suitable due to the clear defined strain distribution in the analyzing section, where the strain gages are applied. The determination of the test strain is of particular importance here. In this contribution, two different measurement methods – using displacement transducers and 3D digital image correlation (DIC) – are applied for the determination of the test strain and compared. The DIC strain evaluation used here deviates from the method based on spline approximation of the displacements or coordinates.