Xue Ke-min

Spinning Deformation Criteria of Thin-walled Tubular Part with Longitudinal Inner Ribs

As a successive and local plastic deformation process, backward ball spinning was applied for the purpose of producing thin-walled tubular parts with longitudinal inner ribs. According to the local plastic deformation theory, the application of yield criterion to the spinning process and the influence of the radial spinning force component on the formability of inner ribs were analyzed. Based on yield criterion and plastic mechanics, the stable flow rule of metal material and forming criteria of the inner ribs were obtained and conformed to the experimental results so as to contribute greatly to improving the ball spinning process and optimizing the process variables, such as the diameter of ball, the reduction in a pass and the wall thickness of tubular blank, which have a significant influence on the formability of the inner ribs. The knowledge of the influence of the process variables such as the diameter of ball, the reduction in a pass and the wall thickness of tubular blank on the spinning process is essential to preventing the quality defects of the spun parts and obtaining the desired spun parts.

Observations on the Ductility and Thermostability of Tungsten Processed from Micropowder by Improved High-pressure Torsion

Abstract Tungsten was subjected to severe plastic deformation at 440 °C using high pressure torsion (HPT) with an improved die-set. Microhardness measurements suggest an appreciable ductility level in tungsten after HPT with Vickers microhardness HV as high as ∼11 500 MPa. Differential scanning calorimetry (DSC) analyses show that samples with less strain have a higher recrystallisation temperature (greater than 1450 °C) than samples with more strain (∼800 °C). X-ray diffraction analyses indicate increases in lattice strain up to 0.35%, lattice parameter up to 0.3177 nm and dislocation density up to 2.4 × 10 15 m −2 . The current study introduces the improved HPT process as an effective route for the production of ultrahigh strength W with significant ductility and specified thermostability