Strain rate and aging effect on the mechanical properties of sheet steels

This study was primarily involved with the experimental determination of the dynamic mechanical properties of five different sheet steels. The nominal yield strengths of these five types of sheet steels ranged from 172 to 690 MPa (25–100 ksi) and the range of strain rates varied from 10−4 to 1.0 mm/mm/s. All these five materials were studied in both longitudinal and transverse directions under various strain rates, and some materials were also tested under different strain rates and different amounts of prior cold stretching. In addition, two types of steels were tested to estimate the aging effect on the mechanical properties of sheet steels. The test results showed that the proportional limit, yield strength, and ultimate tensile strength increase with increasing strain rate. In general, the amount of increase was found to be dependent on the static yield stress of sheet steel, the amounts of prior cold stretching, and the strain rates used in the tests, and independent on the test directions (longitudinal or transverse), test types (tension or compression), and material aging conditions (aged or nonaged). General equations were also derived to predict the tensile and compressive yield stresses for strain rates ranging from 10−4 to 102 mm/mm/s.