Variation of tensile and bending rigidities of a duplex embossed steel sheet by small uniaxial tensile deformation

摘要

Materials which have periodic macroscopic structure have some potential for becoming an advanced method to enhance the mechanical properties of sheet metal which will be applied to automotive parts and architecture. This structure, achieved here by embossing sheet metal, could improve mechanical features, especially bending rigidity. In addition to the microscopic aggregate structure, periodic configurations given by embossing bring about new quasi-uniform "apparent" macroscopic properties. When an embossed sheet is subjected to plastic deformation, the new shape would include these apparent mechanical properties. In this study, uniaxial tensile tests and bending tests of duplex embossed sheets, which have periodic convexities and concavities, were conducted experimentally and analytically respectively. And tensile rigidity and bending rigidity were evaluated by changing the embossing height and direction. The variation of these rigidities with different preliminary small uniaxial tensile deformations (pre-strains) was also investigated. The results confirmed that the tensile rigidity of embossed sheets with larger embossing height was lower than that of sheets with smaller embossing height. However, when preliminary tensile deformation was added, the tensile and bending rigidity increased. On the other hand, the bending rigidity of embossed sheets with larger embossing height was considerably higher than that of sheets with smaller embossing height. The degree of these tendencies varied depending on the embossing direction. Furthermore, from analytical results, the evaluation method which was used apparent geometry in this study, it is suitable to evaluate duplex embossed sheets due to it includes local rotating and bending deformation are accompanied with the plastic deformation. Also, it is considered that the apparent bending rigidity is a comprehensive value which can express more realistic macroscopic deflection behavior of embossed sheet.