부산대학교 도서관

Background: Evaluation of material properties under biaxial loading is a cumbersome process. Biaxial mechanical properties using the planar biaxial testing technique is a very accurate method compared to other out-of-plane biaxial testing techniques. Though the planar biaxial tests predict the deformation behavior of the material precisely, their applicability is limited to the design of the cruciform specimens. Improper cruciform specimen design induces inhomogeneous strain distribution, which leads to failure at a very low strain level or out of the gauge region. Objective: The present study aims to design a novel cruciform specimen to achieve homogenous and maximum strain distribution at the gauge region. Methods: Initially, an optimized cruciform biaxial specimen was designed using a commercial finite element method. 1050 Aluminum alloy sheet with 2.5 mm thickness was used for the experimental validation. Strain evolution during planar biaxial testing was captured with the help of the Digital Image Correlation method. Results: It was found that a cruciform sample with 60% thickness reduction at the gauge region is capable of achieving 87.5% of the fracture strain achieved during uniaxial tensile testing before breaking. It was observed that the optimized cruciform specimen was deformed uniformly with a fracture at the gauge region. Conclusions: The optimized design was used for the measurement of yield locus up to higher plastic strain values. The experimental yield loci were compared to the yield criteria of von Mises, Hill'48, Hill'93, and Barlat. The Barlat yield criteria is the most accurate for AA1050 yield loci evaluation. [ABSTRACT FROM AUTHOR]