Fig. 1. Measurement principle. (a) Schematic of dual-reflector imaging; (b) selection of corresponding points in left and right images

Fig. 2. Tensile specimens

Fig. 3. Experimental setup

Fig. 4. DIC calculation regions. (a) Specimen 1; (b) specimen 2

Fig. 5. Displacement fields under load of 7.0 kN. (a) U; (b) V

Fig. 6. Strain fields under load of 7.0 kN. (a) ε_x; (b) ε_y

Fig. 7. Strain results of specimen 1. (a) Biaxial strains; (b) measurement errors of 3D-DIC method and proposed 2D-DIC method compared with strain gauges

Fig. 8. Displacement fields of specimen 2. (a) U; (b) V

Fig. 9. Strain fields of specimen 2. (a) ε_x; (b) ε_y

Fig. 10. Strain fields of specimen 2 obtained using proposed 2D-DIC. (a) ε_x; (b) ε_y

Fig. 11. Strain fields obtained using FEM. (a) ε_x; (b) ε_y

Fig. 12. Strain fields obtained using 3D-DIC method. (a) ε_x; (b) ε_y

Fig. 13. ε_x along line AB obtained using three methods