Nature of relationship between simple and integrated indicators of stressed state, safety margin and effi ciency of wire forming

The combined criterion, which includes forming effectiveness indicator and the I.L. Perlin’s safety margin is proposed. Interdependencies for different criteria for the shape of the deformation zone are given. Suggested indicators for assessing of the shape of plastic deformation zone are simpler than delta criterion used in the foreing theory of drawing. For different hardening models, the results for the calculation of the axial stress, the absolute safety margin, the I.L. Perlin’s wire safety margin, V.L. Kolmogorov’s stress state indicator stress state indicator and the proposed criteria for assessing of the forming effectiveness when drawing round solid profile depending on the drawing coefficient, drawing angle and criteria for the shape of the plastic deformation zone. In the plastic deformation zone with equal average yield strength, the equality of the strain indicators of the wire is not ensured if hardening curves of material are different. In particular, when the drawing coefficient ensures equal yield strength for different hardening curves and is equal to the initial yield strength, the drawing stress is more at more convex shape of the hardening curve. At the optimum drawging angle, when the minimum axial stress, the maximum values of the safety margin indicators and the proposed criteria for the forming effectiveness and the minimum stress state indicator are observed. Equal minimum values of the drawing stress when varying the drawing angle, the length of the plastic deformation zone or other criteria. The nature of the relationship between the stress state indicators, the safety margin and the forming effectiveness is shown. With different hardening models of lines for the relationship of the I.L. Perlin’s safety margin and V.L. Kolmogorov’s stress state indicator are located along one curve, as are the lines for the relationship between the dimensionless axial stress and the stress state indicator. With the strain parameters, when the drawing stress under the action of back tension is less than this stress in the absence of back tension, the safety margin and the new combined forming effectiveness indicator are more under the action of back tension. This is possible with intensive hardening of the wire material in the draft of drawing, reduced drawing angles and increased values of drawing and friction coefficients. Different values of strain indicators of steel 12Kh18N10T wire after quenching and annealing are shown.