Własności Materiałów przy Gięciu Walcowym
For a given material, these curves represent the relation between the ratio of the bending moment to the section index and the ratio of the half-thickness of the sheet metal to the curvature radius and the relation between the ratio of the area below this curve to the area of the rectangle with sides M/W and g/o, where M denotes the bending moment, w the section modulus, g the thickness, g radius of curvature and the ratio of the half-thickness to the curvature radius. Two test methods were used. In the first, the test-piece (of sheet metal) was loaded with the bending moment in a special device, in the second it was bent on about a form block. The bending curves obtained by the first and the second method coincide within the limits of the measurement error.
Z. MARCINIAK, O uwzględnieniu własności materiału przy gięciu blach, Obróbka Plastyczna Tom 1, Z. 2