Relation of Compression Residual Stress on Pre-Tensioned Surface in Parabolic Leaf Spring Submitted to the Stress Shot Peening Process in Carbon Steel

This work deals with the effect of different blasting conditions under stress on the intensity and distribution of compressive residual stresses. The tests were performed on bars measuring 17 mm x 70 mm x 1700 mm in AISI 51CrV4 carbon steel. The samples are considered parabolic leaf spring, as there is a variation in thickness from the tip to the center, the thickness ay the center is higher than tip thickness. The samples were laminated to their thickness in double roller laminators, in order to obtain the desired thicknesses. The samples were quenched and tempered in industrial scale furnaces. The pre-tensions were calculated by the ANSYS^® software and validated by characterization with strain gauges, in a test condition of 1400 MPa of pre-tension. Tensile tests and microstructure analysis were applied to ensure the specification in terms of strength and microstructure. The stress shot peening process was performed on a sample with flexural load at two points with a support distance of 150 mm. The maximum bending pre-tension were 1450 MPa and 1750 MPa. Residual stresses were measured by X-ray diffraction at five positions. Measurements were made on samples with deflections and before detonation. Residual stress measurements on a sample after heat treatment showed tensile residual stress values. in the deflected samples, the residual compressive stresses increase from the tip to the center of the specimen, this was demonstrated proportionally with the validation of the extensometers, but it was not what was presented by the ANSYS software, establishing differences in the pre-tension of the values of the surface of the sample.