For constitutive identification, e.g., calibration of a yield function or a hardening law, several types of material testing machines and specimen shapes are employed to determine flow stresses corresponding to different stress states. Among them, using a biaxial tensile testing machine with a cruciform specimen makes it easy to realize various stress states by controlling the force ratio. In this work, a novel shape of a cruciform-like specimen that allows combined tension and shear is suggested, to measure flow stresses for stress states in 3D space (σ<sub>11</sub>, σ<sub>22</sub>, σ<sub>12</sub>). The dimensions of gage-section and notch shape are then optimized for the minimum variation of both stress fields for tension and shear in the gage-sections, so that the experimentally measured forces can be directly used for the stress calculation. The flow behavior for combined tension and shear are evaluated from multiaxial tests with the optimized specimen and different force ratios.