We proposed a local one-sided rubber bulging method of metal tubes to evaluate various strain paths at an aimed portion and measured the forming limit strains of metal tubes at the place of the occurrence of necking under biaxial deformation. Using this method, since rubber is used to give pressure from the inner side of the tube, no sealing mechanisms were necessary unlike during hydraulic pressure bulging. An opening was prepared in front of the die to locally bulge a tube at only the evaluation portion. To change the restriction conditions of the bulged region for biaxial deformation at the opening, a round or square cutout, or a slit was introduced. The test was conducted using a universal compression test machine and simple dies rather than a dedicated machine. Considering the experimental results, it was confirmed that the strain path was varied by changing the position and size of slits and cutouts. Using either a cutout or a slit, the strain path in the side of the metal tubes can be either equi-biaxial tension or simple tension, respectively. Additionally, by changing the size of the cuts or slits, the strain path can be varied.

中文翻译：

---

用于测量金属管各种应变路径的局部单侧橡胶鼓胀试验

我们提出了一种用于金属管的局部单侧橡胶鼓胀方法，以评估目标部位的各种应变路径，并在双轴变形下在颈缩发生的位置测量金属管的成形极限应变。使用这种方法，由于使用了橡胶来从管子的内侧施加压力，因此与液压鼓胀时不同，不需要密封机构。在模具的前面准备了一个开口，以便仅在评估部分使管子局部凸出。为了改变在开口处用于双轴变形的凸出区域的限制条件，引入了圆形或方形切口或狭缝。该测试是使用通用压缩测试机和简单模具而不是专用机器进行的。考虑到实验结果，可以确认，通过改变狭缝和切口的位置和大小来改变应变路径。使用切口或狭缝，金属管侧面的应变路径可以分别是等双轴拉力或简单拉力。另外，通过改变切口或狭缝的尺寸，可以改变应变路径。