A presentation by Dr. Thomas Stoughton, General Motors Company, at the 2021 Great Designs in Steel. Using the example of a DP 980 steel, this presentation addresses three questions:
This presentation reviews how digital image correlation (DIC) technology has set the metal forming industry up for a game changing revolution in the amount and nature of information that can be gleaned from material testing. The presentation will focus on the benefits of using DIC for the measurement and analysis of the common uniaxial tension test under monotonic loading conditions, providing literally orders of magnitude more information, including new information that not available without DIC.
The expanded and new types of information that DIC enables includes 1) measurement of the stress strain relation and evolution of R Value to strains far beyond maximum load, 2) detection of the onset of localized necking, 3) measurement of the degree of material homogeneity of all of its properties, 4) measurement of the degradation of the elastic modulus with strain, 5) ability to decouple strain and strain-rate effects on the stress-strain behavior, from a single monotonically loaded specimen, without employing jump tests, and 6) the determination of a realistic lower bound for the fracture limit strain and its dependence on strain path.
The unprecedented amount and new information that DIC enables is there for the taking from each and every specimen loaded in uniaxial tension under monotonic loading conditions. Examples of these benefits will be demonstrated for uniaxial tension tests on DP 980 and a DP 1180 steels that were selected for use in the Numisheet 2021 Benchmark Study.