•Determination of flow curves for three different steels (DP600, DP1000, CP1000) up to strains of 1.159 with grooved torsion test.•Determination of fracture strains up to 1.159 for an AHSS with ultimate strength > 1150 MPa.•Analysis of preparation strategy of specimen on flow curves and fracture strain.•Milling with fine surface roughness recommended for determination of fracture strain.•Electrical discharge machining recommended for determination of flow curves. In-plane torsion tests offer advantages such as a proportional loading path and a homogeneous stress and strain distribution when characterizing the material behavior in the state of in-plane shear. The use of a grooved specimen is mandatory for the characterization of the damage behavior. The manufacturing of the groove by turning, milling, and electrical discharge machining for a DP600, DP1000, and CP1000 showed a strong influence on the experimentally measurable strain values at failure. Fine machining by milling displayed good results for all tested materials. The notch-effect in turned grooves led to an early fracture initiation. A straightforward parameter identification scheme for the Hosford–Coulomb fracture criterion as proposed by 16 was used to show the sensitivity of fracture curves on the experimental database. Display omitted