Study of Residual Stresses on Cold-Forming Metals Using Stress Corrosion

Residual stresses are frequently evaluated using two types of tests: destructive and non-destructive. The most common type of non-destructive test examines the relationship between physical parameters measured by X-ray diffraction. This technique requires a small sample size and a planar surface. In metal forming, the geometry of different pieces is complex, and most of the surfaces are curved. This work utilizes an indirect method to evaluate the residual stresses present in the cold forming of non-flat metal surfaces using a corrosion test in the deformation region. Samples from AISI 1045 steel were cold bent to angles of 150 degrees, 120 degrees, 90 degrees, and 45 degrees. The samples were then subjected to a corrosion test to evaluate the potential difference (PD) and the results were compared to those of an unbent sample. The bending process was simulated by finite element method that revealed the intensity and nature of residual stresses in the samples. The results were statistically treated and demonstrate that the PD depends on the bending angle and exposition time to the corrosive medium but is independent of the corrosive medium. We conclude that it is possible to evaluate the residual stresses on cold-forming metal parts with complex geometries using a corrosion test.