Magnesium alloy tubes have good formability at elevated temperatures. In this paper, firstly, uniaxial tensile tests are conducted to evaluate the flow stress of AZ61 magnesium alloy at different temperatures and strain rates. Secondly, a hydraulic warm forming machine with axial feeding, counter punch and internal pressure is designed and manufactured. Using this testing machine with the FEM results, experiments of hydraulic forming of AZ61 magnesium alloy tubes at different temperatures are carried out. The effect of loading paths on the product shape and formability at different temperature are discussed.

ABSTRACT The objective of this study is to obtain the friction coefficient of lubricants in tube hydroforming of guiding zone. Lubricants, universal testing machine, and friction test machine in tube hydroforming of guiding zone are used to carry out the experiments of aluminum alloy tubes. Lubricants are categorized according to their performance as follows: (1) oils, (2) emulsions, and (3) slide lacquer. Different lubricants tests, it is known that the best lubrication is derived from slide lacquer, while oils showed the poorest behavior. Different internal pressure tests, it is known that greater internal pressure causes the coefficient of friction decreasing. Different sliding velocity, it is known that sliding velocity does not affect the coefficient of friction at 100mm/min. And using CCD which is an optical instrument obtains the surface of tubes after experiments.

Because magnesium alloy tube has good formability at elevated temperature, uniaxial tensile tests were employed to evaluate the warm properties of AZ31 magnesium alloy. After that, this paper has designed and manufactured a hydraulic bulge warm forming machine which can be used to experiment with fixed tube length. Using this testing machine, the experiments of hydraulic bulge forming of AZ31 magnesium alloy and 6061 aluminum alloy tube at elevated temperatures were carried out. According to experimental results, the hydraulic bulge forming properties of tubes at different temperatures are discussed.

The tube hydro-forming (THF) is an innovative manufacturing process which is used to manufacture many industrial components widely. The success of THF is largely dependent on the selection of the loading paths: internal pressure versus time, axial feeding versus time and counter punch (CP) versus time. The finite element analysis is used to simulate the forming result of different loading paths and reduce the cost of die-testing. This paper presents the forming of T-branches and T-branches components with CP. These paper has developed an adaptive simulation algorithm by combining FEM code LS-DYNA 3D with controller subroutine to get ideal bulging height and uniform thickness of the formed tube with multi-stages. Discuss influence under different parameters of process. The results are compared with experimental results to validate accuracy by this adaptive control methods.

ABSTRACT The objective of this study is to establish the Forming Limit Diagram (FLD) of tubes. An experimental system of tube hydroforming, the electrical chemical etching method and the image process system are used to carry out the sheet metal forming test and the hydraulic bulge-forming test of annealed aluminum alloy tubes. Furthermore, Hill¡¦s new yield criterion is also used to predict the Forming Limit Curves of sheets. The predicted forming limit diagrams are compared with experimental data. The forming limit diagrams of tubes are coincident with those of sheets. Also, the predicted forming limit curves by Hill¡¦s new yield criterion agree quite well with those by experiments. Therefore, Hill¡¦s new yield criterion can be used to establish the forming limit curves of sheets or tubes.

Magnesium alloy tubes have good formability at elevated temperatures. In this study, a finite element code DEFORM 3D is used to simulate the result of T-shape hydroforming at working temperatures 150¢J and 250¢J with magnesium alloy AZ61 tubes and then conducts the hydroforming experiments. By modifying the loading paths, products with uniform thickness and branch height are obtained 49mm. The results of simulation are compared with the experimental results to verify the validity of this modeling. On the other hand, the effects of the die fillet radius on tube formability during y-shape hydroforming are discussed. With the right die fillet radius r1¡×10mm and the left die fillet radius r2¡×30mm, a better formability of the tube is obtained.