Abstract: The ends of large deformation free pushing diameter-reducing tube blanks were warped, that is, the outer diameters of the ends were larger than that of the sizing areas. For the end warpage areas, based on the deformation analysis and mechanics equilibrium conditions, the formula of circumferential residual stress was deduced from the warpage deformations and shear stress. It is revealed that the circumferential residual stress is characterized as tensile stress from the inner to outer surface. The double-sided large deformation diameter-reducing of 219 mm × 7.5 mm seamless steel pipes were carried out on the three-dimentional hydraulic press. With the diameter-reducing sample intercepted, the measuring points were selected in the inner and outer surfaces of the end warpage areas and sizing areas, and the residual stress was measured by X-ray diffraction method. The trend of end warpage area measurements were consistent with the theoretical analysis. For the diameter-reducing processes, the finite element simulation was carried out with ABAQUS software, the results of the deformation and force are in good agreement with the diameter-reducing experiments, and the results of residual stress in the inner and outer surfaces are consistent with the X-ray measurement. Furthermore, the distribution laws of residual stress along the wall thickness direction and the axial direction from the sizing areas to the end are revealed respectively.

Key words: tube blank, large deformation free pushing diameter-reducing, end warpage, residual stress, X-ray diffraction method

摘要： 管坯大变形自由推压缩径时端部存在翘曲，即端部外径大于定径区外径。针对端部翘曲区进行变形分析，并基于平衡条件推导了周向残余应力与翘曲变形和剪应力的关系表达式，揭示了由内表面层到外表面层整体存在周向残余拉应力的事实。在三向液压机上进行219 mm×7.5 mm无缝钢管的双侧大变形缩径，在缩径管件上截取包含端部翘曲区和定径区的试样，在其内外表面不同区域选取测量点，并采用X射线衍射法测量残余应力，端部翘曲区测量结果与理论分析结果趋势一致。针对缩径管件变形过程，采用ABAQUS软件进行有限元模拟，缩径变形及缩径力的模拟结果与缩径试验结果吻合，内外表面层残余应力的模拟结果与X射线衍射法测量结果趋势一致。给出了自定径区至端部沿壁厚方向及沿轴向方向的残余应力分布规律。

关键词: 管坯, 大变形自由推压缩径, 端部翘曲, 残余应力, X射线衍射法