Investigation of stress distribution in the pre-fracture zone during the implementation of waste-free processes for the separation of sectional rolled products into workpieces
DOI:
https://doi.org/10.37142/2076-2151/2025-1(5)125Keywords:
bending fracture, brittleness, plasticity, damage accumulation, pre-fracture zone, crack, strength.Abstract
Karnaukh S. Investigation of stress distribution in the pre-fracture zone during the implementation of waste-free processes for the separation of sectional rolled products into workpieces
The objective of the work is to investigate the process of separating sectional and tubular rolled products using known models of stress distribution in the pre-fracture zone and theoretical modeling of the separation process using the finite element method. Based on the analysis of known models, a model has been identified that describes the stress distribution in the pre-fracture zone using a two-parameter nonlinear function consisting of two parts: a power-law part, which describes the strengthening of the material matrix, and an exponential part, which describes the peculiarities of damage accumulation in the material, taking into account the type of stress state and work hardening. The application of this model has made it possible to obtain correct results for stresses in the pre-fracture zone for materials in the plastic (Steel 20), elastic-plastic (Steel 45, Steel 40Kh), and brittle (Steel 60S2) states, which are confirmed by the results of modeling the separation processes using the three-point cold bending fracture scheme with the Deform software package. The discrepancy between the calculated stress values in the pre-fracture zone, obtained using the known model and the Deform software package, ranges up to (10...35)%. The significant discrepancy in the results is explained by the fact that the Bridgman criterion is poorly applicable to samples with sharp notches, which corresponds to an effective stress concentrator during the implementation of the three-point cold bending fracture, and the maximum errors in the main stress parameters under triaxial, biaxial, and uniaxial stress states can reach up to (60...70)%. The obtained results can be used for the automation of designing processes for separating sectional and tubular rolled products based on data accumulation and the creation of informational databases with calculation and methodological recommendations, as well as deformation schemes.
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