Research On The Roller Shape Curve And The Straightening Precision Of The Six-roller Straightener For Ф5～Ф10mm Titanium Alloy Tubes

Titanium alloy tubes are widely used in medical equipment, the structure components of aircraft engine compressor, rockets, missiles and high-speed aircraft. With the improvement of the accuracy requirement of the machine, the demanding of varieties precision index is becoming more and more harsh in all areas of titanium alloy tubes, thus the importance of the straightening is gradually improving, there still have many problems to be solved in the straightening of titanium alloy tubes. On one hand, Titanium alloy tubes easily swing in the straightening process which lead to the surface indentation. On the other hand, there are empty straightening zone in the straightening process of multiple oblique roller and it takes more for the guides when we use the two-roller straightening. These directly affect the quality and efficiency of straightening. Improved the intermediate two-roller of the six-roller straightening, it makes up for the defects of the two-roller straightening which makes too large straightening force, meanwhile, it makes up for deficiencies of the ordinary six-roller straightening which can’t straighten the head and tail of the titanium alloy tubes. Therefore, the research on the six-roller straightening has important theoretical value and practical significance.Based on the principle of six-roller straightening, a more precise tube bending elastoplastic model is established under the circumstance of titanium strengthened in this paper. Firstly, the relationship among stress, strain and curvature in the bending deformation is analyzed and the moment formula during the straightening is derived. Secondly, through the analysis and calculation, a more accurate inversed bending curvature ratio is obtained which makes the roller design is more precise. At the same time, a variety of design methods to the different roller shape are analyzed. Finally, based on MATLAB, the parameter of hyperbolic roller, unidirectional inversed bending roller and bidirectional inversed bending roller are calculated respectively. Meanwhile, the double roller in the traditional six-roller straightener adopted unidirectional inversed bending and bidirectional inversed bending respectively and the straightening roller is selected as small diameter titanium alloy tubes.Using ABAQUS, the finite element model of tube straightener is established. The dynamic simulation of straightening process to tube was researched by different roller type and different process parameters. Then, the straightening effect was analyzed after observing the degree of roundness, straightness and residual stress of tube straightening.Through the comparison of straightening effect to different roller types and optimization of the roller shape, the residual stress of the pipe is reduced, and the straightening quality is improved. Compared with the previous parameters, the optimal parameters we obtained through the analysis of parameters in the straightening process and finite element simulation is more prominent. The straightening quality of the tube is improved, which provides a favorable reference for the actual production.