Evaluation of the level of hardening of aluminum alloy chips intended for subsequent pressure treatment

OBRABOTKAMETALLOV Vol. 23 No. 1 2021 TECHNOLOGY processes with high normal stresses on the contact surface; it is also implemented in this formulation. The coef fi cient of friction is assumed to be equal to 0.1. The RAPID 2D software package allows operating with dimensional values at the millimeter level and above, which is not always typical for chip removal. Therefore, we used the following technique: the dimensional values were increased by an order of magnitude, bearing in mind the subsequent transition after the implementation of calculations to dimensionless values. The dimensionless representation of information makes it more versatile for use. A layer of metal with a thickness of 25 mm is considered. The thickness of the metal removal is assigned at 1 mm. The dimensions are chosen conditionally, it is the ratio between them that is important. The fi nite element grid at the places of the assumed increased strain gradients is made with a smaller step. The deformation hardening of a metal is estimated by invariant values: either by the degree of defor- mation  (equivalent deformation) or by the degree of shear deformation  with the correlation between them, Λ = 1,732 ε . Areas of equal level (Fig. 3) show that the degree of shear deformation in the chip can reach values higher than 2; this value is higher on the convex part of the coil. This can be explained by the fact that the convex part of the chip undergoes a greater elongation relative to the concave surface. Plastic deformation during chip removal ends at the place where it is separated from the tool. The scheme presented in Fig. 3 allows estimating the transition from the non-strengthened state  to the hardened one, but the gradient of the deformation degree in the chip itself cannot be adequately displayed. Therefore, in Fig. 4, the range of displaying the degree of shear deformation is shifted to 2...2.8. Fig. 3. Solution of the problem of separation of chips at an angle of  = 10 ° and a nominal removal depth of 1 mm: 1 – workpiece from AlMg1 alloy; 2 – cutter; 3 – chips; on the right is a color key for the of shear strain  The maximum value of the shear deformation degree is  = 2.69. This value can be correlated with the value of the reduction of the cross-sectional area  for example, when drawing a rod, using the formula       0 1 0 0 1.732 ln 1.732 ln 1.732 ln 1 1 100 F F F F F                    , (1) where F 0 , F 1 ,  F are the initial and fi nal cross-sectional areas, as well as their change, respectively. From here   100 1 exp 1.732         . (2) At  = 2.69, the value  = 79%.