This paper proposes an efficient method for identifying the parameters of materials exhibiting the strength differential (SD) effect. Ti-6Al-4V is widely used due to its high specific strength and excellent corrosion resistance. However, this material exhibits the SD effect, where the yield stress differs between tension and compression. Traditionally, identifying these material parameters requires multiple material tests, resulting in increased cost and time. To address this issue, we performed a single four-point bending test to induce both tensile and compressive states in the specimen and measured the strain distribution using the digital image correlation (DIC) method. Using the four-dimensional ensemble variational method, a type of non-sequential data assimilation, we calibrated an anisotropic material model. This approach enables the identification of parameters related to both tension and compression from the data obtained in a single test. As a result, the relative errors in yield stress were 0.43% in tension and 2.24% in compression.
OUCHI et al. (Wed,) studied this question.