Effect of strain rate on shear properties and fracture characteristics of DP600 and AA5182-O sheet metal alloys

Abstract

Abstract. Shear tests were performed at strain rates ranging from quasi-static (.01 s −1 ) to 600 s −1 for DP600 steel and AA5182-O sheet metal alloys at room temperature. A miniature sized shear specimen was modified and validated in this work to perform high strain rate shear testing. Digital image correlation (DIC) techniques were employed to measure the strains in the experiments, and a criterion to detect the onset of fracture based on the hardening rate of the materials is proposed. At equivalent strains greater than 20%, the DP600 and AA5182 alloys demonstrated a reduced work hardening rate at elevated strain rates. At lower strains, the DP600 shows positive rate sensitivity while the AA5182 was not sensitive to strain rate. For both alloys, the equivalent fracture strain and elongation to failure decreased with strain rate. A conversion of the shear stress to an equivalent stress using the von Mises yield criterion provided excellent agreement with the results from tensile tests at elevated strain rates. Unlike the tensile test, the shear test is not limited by the onset of necking so the equivalent stress can be determined over a larger range of strain.

Fracture Characterization of Rolled Sheet Alloys in Shear Loading: Studies of Specimen Geometry, Anisotropy, and Rate Sensitivity

“…It was shown by Rahmaan et al [30] that the results of the reduced size mini-shear specimen are in excellent agreement with that of a full-size mini-shear sample for both an aluminium-magnesium alloy, AA5182-O, and a dual-phase steel, DP600. Therefore, in the present study, efforts to further validate the full-size versus scaled-down mini-shear specimens…”

“…The reported DIC strains were averaged using a circle with 0.5 mm diameter located at the center of the butterfly and full-size mini-shear specimens, while a circle diameter of 0.25 mm was used for the scaled-down mini-shear specimen. More information regarding the method of extracting the average local strains in the mini-shear specimen can be found in Rahmaan et al [30].…”

“…As mentioned earlier, the strains reported in the present paper are the average values over a circle in the gauge area of the specimens. Rahmaan et al [30] studied the influence of the method of averaging the DIC shear strain by using points, squares, and circles with different sizes in the mini-shear specimen. However, in order to investigate the influence of the method of averaging strains, two different circle sizes, one smaller (R 1 =0.25mm), and one larger (R 3 =0.75mm) than the reference circle size of R 2 =0.5mm along with a point at the center of circles ( Figure 16) were used to obtain the fracture strains of DP780 mini-shear and butterfly experiments and the results are presented in Table 5.…”

“…The advantage of this test geometry is that it has a relatively simple design and does not require through-thickness machining that may introduce surface defects. Recent works by Abedini et al [29] and Rahmaan et al [30] have demonstrated the advantages of the Peirs et al [27] geometry.…”

A Generalized Stress State and Temperature Dependent Damage Indicator Framework for Ductile Failure Prediction in Heat-Assisted Forming Operations

“…In addition, an experimental value for the equivalent plastic fracture strain at in-plane shear at 25 C of C] = 1.0 was adapted from Rahmaan et al [ 39 ] to take failure at low strain ratios/triaxialities into account. Furthermore, by setting C] = 3.0, it is assumed that no failure occurs under compression.…”