DETERMINATION OF THE POSSIBILITY OF OBTAINING THE MINIMUM BENDING RADIUS DURING PROFILING

Abstract

The increased demand for high-quality sections made of various grades of steel has set the problem of adjusting the estimates of the strength and plastic properties of the original materials for manufacturers of bent sections. The issue of material destruction during profiling (primarily the minimum permissible bending radii) was previously resolved based on their relative elongation δ₁₀. However, it was later proven that a more correct indicator of material plasticity for profiling should be considered the relative transverse contraction ψ_ш. Based on the assessment of plasticity by ψ_ш, methods for determining the minimum permissible bending radii were developed. However, since ψ_ш under uniaxial tension is not equal to ψ_ш under biaxial tension, which occurs on the outer surface of the bending point, it is necessary to introduce correction factors. The need to take into account the influence of the stress-strain state scheme led to the emergence of refined factors, the exact determination of which is often impossible. The critical radius of destruction r_к was obtained from a comparison of the specific deformation work during bending with the critical destruction work, which is 0.16 for bending for steel St. 3sp and 0.27 for steel 09G2. The paper found that the critical radius also increases with an increase in the bending angle. Technological bending radii should differ from the calculated values of the critical bending radius by a safety factor. For piece profiling, when there is work hardening and burrs at the ends of the strip, the relative minimum internal bending radius should be determined by the formula r_min=(2,8…3,5)r_К. In the paper, the specific deformation work of an elementary volume of a bending point during profiling was determined using the method of continuum mechanics and the field of displacement velocities. The critical destruction radius was obtained from a comparison of the specific deformation work during bending with the critical destruction work. The work established that the technological radii of bending points should differ from the calculated values of the critical bending radius by a safety factor.