Methods of Establishing Forming Limit Diagram of Tube Hydroforming

Forming severity is one of the significant indexes to assess formability of tube hydroforming. The state of strain can be accurately reflected when tube reaches forming limit, mechanical rules during forming processes can be revealed as well by using the forming limit diagram (FLD). By contrast with FLD of sheet metal, the FLD of tube hydroforming is seen as different. In this paper, the importance of FLD of tube hydroforming was discussed briefly; typical methods established to FLD of tube hydroforming were listed and classified; characteristics and insufficiencies of those methods were pointed out; advantages of forming limit stress diagram (FLSD) were introduced simply. Furthermore, the main problem and the trend of development in FLD of tube hydro-forming were summarized.

Present of Three-layered hydro-forming analysis of a new hybrid sandwich tubes using finite element method

Multi-layered tube hydro-forming is suitable to produce multi-layered joints to be used in special application in many industries. With using a middle layer of foam and making sandwich structures, tube bending strength increases when external loads are applied. Also because of the foam is high energy absorption, in the pipelines of major industries such as the nuclear, strength increases when natural disasters, especially earthquakes happen. In this paper for the first time, three-layered new sandwich tube (inner layer of copper, middle layer of aluminum foam and outer layer of annealed brass) hydroforming processes were numerically simulated using finite element method by ABAQUS/Explicit 6.10. As the result of three-layered sandwich tube hydro-forming not reported in the literature, the results of this paper are compared with the latest experimental result of bi-layered tube hydro-forming find in literature by approaching the thickness of middle layer to zero. Finite element analysis shows that numerical and experimental results have a good agreement

Development of Experimental Devices for Tube Hydro-Forming

The exploitation of Tube Hydro-forming (THF) experimental device plays an important role on the development of THF technology. In this paper, some representative experimental devices are introduced, including device with outside pressure source and device with internal pressure source. The working principle, technical characteristics, sealing mode and pressurization way are compared and analyzed. Meanwhile, the development trend in exploitation of the test device is envisioned.

Metal Flow Rule of Multi-Way Tube Hydro Forming for Air Handling Unit

Multi-way tube on air conditioning header is considered as the research objective .Finite element simulation method is utilized to simulate and analyze the deformation process of metal. Through analyzing the distribution law of velocity on work piece neutral plane and displacement law of typical nodes, common law in deformation process for metal flow was revealed. Results suggested that: metal which is on terminal supplementary zone conspicuously flows along horizontal. Metal which is on forming zone conspicuously flows along bulge, metal which is between bulges flows little, these laws provide a reference for the choice of forming technology.

Forming Rule Construction for Hourglass-Like Tube Hydroforming with Magnesium Alloy

The objective of this study is to construct the forming rule for hourglass-like tube with magnesium alloy during hydro-forming and offer the analysis results as a guideline for magnesium alloy forming in industry. AZ31 magnesium alloy circular tube is used as the billet material for hydro-forming with hydraulic pressure as the main forming power combined with the mechanical auxiliary force from the punch to fabricate the hourglass-like tubing products. A finite element based code is utilized to investigate the forming characteristics of hourglass-like tube forming, by changing process parameters such as punch velocity, hydraulic pressure gradient and tool-workpiece interface friction etc. to investigate the material flow of tube filling, wall thickness variations, and stress and strain distributions. And the abductive network is in turn applied to synthesize the data sets obtained from the numerical simulations. Consequently, a quantitative prediction model is developed for the relationships among the process variables, corner radius and minimum tube thickness in the process of hourglass-like tube hydro-forming with magnesium alloy. The results show that proper mechanical force can help material flow, prevent large strain deformation from falling into the area of negative strain hardening rate, enhance the magnesium alloy to become easy in forming and make tube fitting may to be formed successfully.