The Research On Roller Shape Curve And The Numercial Simulation Analysis On The Composite Roll Shape Straightener Foe Titanium Alloy Tubes

With the titanium alloy tube widely used in aviation aerospace and ship fileds, its demand and quality requirements became higher. Straightening is the important process in titanium tube production and its qulity directly determined the qulity of productions. So exploring the new straightening technology is the problem to be solved. For titanium tube straightening, if we use hyperbolic multi-roll straightener the tube ends can not be straightened. If we us one-way reverse bending two-roll straighter, the titanium alloy’s smller elastic modulus will increase the radius difference between the waist and end of the roller which cause the concentration of stress and large inclined angle when the biting process. If we us two-way reverse bending two-roll straighter, the straightening force which goes against straightening will increase. Considering above problems, the composite roll shape straightener was designed which can straighten the titanium alloy tube six hyperbolic roller at first and then straighten it in total lenghth by by two-roll shape roller, more importantly the two-roll shape was designed from whole perspectives of the straightener.In different depth of plastic defomation, the hardening tube bending monment formula was deduced which is different from some known formulas. Based on the deduced formular, the process of reverse bending and springback was studied. For decrease the diameter difference between the waist and end of the roller, the two-roll shape was designed in short length to make it gentle. Comparing with the residual curvature ratio, the reverse bending curvature ratio was determined via Matlab programing which can reach the highest straightening precision to make up the influence of the straightening precision in short two-roll length. The straightener roll shape was calculated and the Matlab GUI was designed after determineding the roll structure parameters.Using the finite element software Marc, the FEM(finite element model) of composite roll shape straightener was built. The whole tube shtraightening process is analyzed by analyzing the strain, stress and the residual stress of the tube. Comparing with the residual stress and straightness under the different intermesh and flattening amount, the optimal parameters were determined in the simulation. The straightening quality in one-way two-roll shape and two-way two-roll shape was compared. By the way, the optimal two-roll shape was determined and modified which can decrease the residual stress and improve the straightness and roundness. The problem of titanium alloy tube ends was solved and the straightening precision of the whole length was improved by comparing the straightening quality between composite roll shape straightener and six-roll straightener.