Using a thin-walled tube torsion test to characterize a material’s shear response is a well-known technique; however, the thin walled specimen tends to buckle before reaching large shear deformation and failure. An alternative technique is the surface stress method (Nadai 1950; Wu et al. J Test Eval 20:396–402, 1992), which derives a shear stress-strain curve from the torque-angular displacement relationship of a solid cylindrical bar. The solid bar torsion test uniquely stabilizes the deformation which allows us to control and explore very large shear deformation up to failure. However, this method has rarely been considered in the literature, possibly due to the complexity of the analysis and experimental issues such as twist measurement and specimen uniformity. In this investigation, we develop a method to measure the large angular displacement in the solid bar torsion experiments to study the large shear deformation of two common engineering materials, Al6061-T6 and SS304L, which have distinctive hardening behaviors. Modern stereo-DIC methods were applied to make deformation measurements. The large angular displacement of the specimen posed challenges for the DIC analysis. An analysis method using multiple reference configurations and transformation of deformation gradient is developed to make the large shear deformation measurement successful. We successfully applied the solid bar torsion experiment and the new analysis method to measure the large shear deformation of Al6061-T6 and SS304L till specimen failure. The engineering shear strains at failure are on the order of 2–3 for Al6061-T6 and 3–4 for SS304L. Shear stress-strain curves of Al6061-T6 and SS304L are also obtained. Solid bar torsion experiments coupled with 3D-DIC technique and the new analysis method of deformation gradient transformation enable measurement of very large shear deformation up to specimen failure.

中文翻译：

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工程材料大剪切变形破坏的实心圆柱扭转

使用薄壁管扭转试验来表征材料的剪切响应是一项众所周知的技术；然而，薄壁试样在达到大的剪切变形和破坏之前往往会发生屈曲。另一种技术是表面应力法（Nadai 1950；Wu 等人 J Test Eval 20:396–402, 1992），它从实心圆柱杆的扭矩-角位移关系中导出剪切应力-应变曲线。实心杆扭转试验独特地稳定了变形，这使我们能够控制和探索非常大的剪切变形直至破坏。然而，这种方法在文献中很少被考虑，可能是由于分析和实验问题的复杂性，如扭曲测量和试样均匀性。在这次调查中，我们开发了一种测量实心杆扭转实验中大角位移的方法，以研究具有独特硬化行为的两种常见工程材料 Al6061-T6 和 SS304L 的大剪切变形。现代立体 DIC 方法被应用于进行变形测量。试样的大角位移对 DIC 分析提出了挑战。开发了一种使用多参考配置和变形梯度变换的分析方法，使大剪切变形测量成功。我们成功地应用实心杆扭转实验和新的分析方法测量了Al6061-T6和SS304L的大剪切变形直至试样破坏。破坏时的工程剪切应变对于 Al6061-T6 约为 2-3，对于 SS304L 约为 3-4。还获得了 Al6061-T6 和 SS304L 的剪切应力-应变曲线。实体杆扭转实验结合 3D-DIC 技术和新的变形梯度变换分析方法，可以测量非常大的剪切变形，直至试样失效。