Application of energy hardness to determine the true stress diagram of the material
The article points to the inconsistency of the approach to constructing a stress-strain diagram, based on the determination of the true tensile stress as a result of dividing the average pressure on the contact patch during indentation by the constraint factor Ψ . New properties of the kinetic indentation diagram are given, in particular, the relation between the exponent of the discharge curve and the contact depth and radius of the contact area has been established. A step-by-step procedure is presented for the proposed method for calculating the stress-strain curve. To find the parameters of the elastoplastic body of Hollomon, the published results of the finite element analysis are used. The procedure allows to iteratively refine the desired parameters. The key point should be the identification of the relationship of the deformation under tension with the value of the relative implementation of the indenter using the energy approach. The method is based on the equality of the energy expended per unit volume of the displaced material beyond the boundary of the initial position within the limits of uniform deformation under uniaxial tension and indentation of the sphere. To determine the true stress, it is necessary to multiply the energy hardness by a constant for a given material coefficient. A good match with the reference data of the mechanical properties of 12Х18Н10Т stainless steel found by the proposed method is shown. The results obtained in accordance with the standard significantly exceed the curve of Hollomon's law. This is due to poor-quality determination of the relationship of deformation under tension with the relative introduction of a spherical indenter.