Comparative study of the mechanical properties of SAE 1045 and SAE 1020 steels obtained from unidirectional tensile and three-point bending tests

ABSTRACT

In engineering and industry applications, mechanical shafts are constantly subjected to bending stresses and, consequently, required by normal bending stresses. These stresses are calculated by the “flexure formula”, which associates the bending efforts with the geometric parameters of the requested element. However, the application of this equation implies some restrictions, which are hardly met in real situations. The present work evaluated and compared the yield strength in traction and the maximum bending stress at the limit of the elastic deformation of the material, obtained through the unidirectional tensile test and bending test in three points, respectively. To obtain the maximum flexion tension was used the “flexure formula” to compare a “real” situation with an “ideal” situation, and from the comparative analysis between the two situations, the differences between the results were observed. The mechanical tests were carried out on specimens in different metallurgical conditions of SAE 1020 and SAE 1045 steels, being these conditions: hot rolled, cold drawn, quenched and tempered, and normalized. At the end of the tests and the analysis of the results, it was possible to clearly observe the differences in the behavior of the materials when subjected to different heat treatments and manufacturing processes. However, the comparative analysis of the yield stress obtained by the unidirectional tensile test in relation to the maximum bending stress obtained in the three-point bending test indicated that, depending on the heat treatment or manufacturing process to which the material was subjected, there are significant differences between the stresses compared; that can lead to over-dimensioning of mechanical designs.

Keywords
Mechanical properties; SAE 1020 steel; SAE 1045 steel; Tensile test; Bending test