Large Strain and Small-Scale Biaxial Testing of Sheet Metals

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• 作者：Y. Seymen ; B. Güler ; M. Efe
• 关键词：Biaxial tension ; In ; situ testing ; Cruciform ; Forming ; DIC ; Aluminum
• 刊名：Experimental Mechanics
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：56
• 期：9
• 页码：1519-1530
• 全文大小：2,537 KB
• 刊物类别：Engineering
• 刊物主题：Mechanical Engineering
  Theoretical and Applied Mechanics
  Characterization and Evaluation Materials
  Structural Mechanics
  Engineering Fluid Dynamics
  Engineering Design
  
• 出版者：Springer Boston
• ISSN：1741-2765
• 卷排序：56

文摘

Small-scale and multi-axial testing of sheet metals, particularly of lightweight alloys and advanced steels are becoming important as these materials exhibit forming behavior sensitive to their unique microstructural features and strain paths. As an alternative to large-scale standard tests, in this paper we introduce a novel biaxial tensile test apparatus utilizing miniature cruciform samples. The compact and portable apparatus includes a custom-built optical microscope and high-resolution digital image correlation (DIC) equipment for in-plane and in-situ strain measurements at the microstructure scale. The small strain and premature fracture problems common to the cruciform tests are solved by optimizing the sample design and by meticulously controlling the manufacturing steps and surface finish. Strain analyses reveal a key mechanism responsible for large strains and fracture at the center. This mechanism suppresses the local neck formation and allows uniform deformation under equibiaxial conditions until fracture. When normalized with the strain hardening exponent of the sample material (Al 6061-T6), the effective strain value before fracture, \( \overline{\varepsilon}/n \sim 3 \), surpass the reported values for similar materials tested by cruciform and standard methods.