A Simple Constitutive Model for Prediction of Single-Peak Flow Curves Under Hot Working Conditions

The hot flow stress of a typical stainless steel was modeled by the Hollomon equation, a modified form of the Hollomon equation, and another modified form based on the Fields–Backofen equation. The coupled effect of the deformation temperature and strain rate was also taken into account in the proposed formulae by consideration of the Zener–Hollomon parameter or dependency of the constants on temperature. The modified Fields–Backofen equation was found to be appropriate for prediction of flow stress, in which the incorporation of peak strain and consideration of temperature dependencies of the strain rate sensitivity and the stress coefficient were found to be beneficial. Moreover, the simplicity of the proposed model justifies its applicability for expressing hot flow stress characterizing dynamic recrystallization (DRX).

Stress-Strain Compression of AA6082-T6 Aluminum Alloy at Room Temperature

Short cylindrical specimens made of AA6082-T6 aluminum alloy were studied experimentally (compression tests), analytically (normalized Cockcroft-Latham criteria—nCL), and numerically (finite element analysis—FEA). The mechanical properties were determined with the stress-strain curves by the Hollomon equation. The elastic modulus obtained experimentally differs from the real value, as expected, and it is also explained. Finite element (FE) analysis was carried out with satisfactory correlation to the experimental results, as it differs about 1,5% from the damage analysis by the nCL concerning the experimental data obtained by compression tests.

Metal drawing goodness degree to which the Hollomon equation applies

In order to establish the cold wire drawing production, the CuNi2Si alloy passes schedule were examined by the Duckfield and Ermanok methods in two wire drawing versions: with the diamond die with an angle of 9o and the tungsten carbide die with an angle of 7o . Experiments confirmed that the CuNi2Si alloy can be successfully transformed to the wire with the diameter of 0.2 mm with properties enabling its practical application. The experimental results and the control group showed that the theoretical methods of the upper and lower bound solution can determine the values of the relevant cold wire drawing factors for the CuNi2Si alloy to which Hollomon curve applies.

Prediction of Tensile Properties Based on Hardness Measurement

The contribution deals with prediction of tensile properties based on measurement of microhardness. First of all, the database of stress strain, s-e vs. hardness data was created. Tensile strength, yield strength, ductility and parameters of Ludwig-Hollomon equation σ = σ0+kεn; k, n were correlated with hardness. Various hardness values found in literature were recalculated to Brinell hardness. In tensile testing measured s-e curves were compared with that obtained from the correlation. The investigated materials were API 5 L grade steels X70 after different deformation exposition. The results give good agreement between compared data. The most difference between estimated and measured curve is in area of yield strength, because of Lüders deformation on investigated steel.