Internal High Pressure Forming Research Articles

Heat treatment and granule medium internal high-pressure forming of AA6061 tube

The new forming process of AA6061 alloy tube, including solution treatment, granule medium internal high-pressure forming and aging treatment, was developed. The AA6061 alloy tube via heat treatment satisfied the forming requirement, and the granule medium internal high pressure forming method for AA6061 alloy tube was also realized by using convenient implementation with low requirement of equipment and flexible design of product. At a solution temperature of 560°C and time of 120 min, the elongation of the AA6061 extruded tube increases by 300% and the strength and the hardness dramatically decrease too. Therefore, the AA6061 alloy tube meets the requirement of internal high-pressure forming because of the improvement of formability. The experiments shows that the strength and hardness of AA6061 alloy workpiece recover to that of the as-received alloy at an aging temperature of 180°C and time of 360 min, and the strength of AA6061 alloy workpiece is equal to the base alloy. The typical parts of convex ring tube, stepped shaft tube and hexagonal tube were successfully produced in lab by using the present forming method. The forming tests show that the maximum expansion ratio (MER) of the AA6061 extruded tube increases by 25.5% and the material properties of formed AA6061 alloy tube reached the performance of as-received alloy.

Research on AA6061 tubular components prepared by combined technology of heat treatment and internal high pressure forming

The high strength aluminum alloy tube can not be formed into complex parts for its high strength and poor plasticity at room temperature. However, its elongation increases with temperature elevating. Therefore, warm forming technology is becoming the research hotspot in aluminum alloy tube forming. However, the control requirement of exact forming temperature and the demand of accessories with high temperature resistance make process control difficult and processing cost high. Based on this point, this study puts forward a new technological process: solution treatment+granules medium internal high pressure forming+artificial aging. During this process, the tested alloy via solution treatment satisfied the process requirements and the granules medium internal high pressure forming method for high strength aluminum alloy tube was also realized by using convenient implementation with low requirement of equipment and flexible design of product. In this paper, the AA6061 extruded tube is investigated to research the effect of heat treatment on mechanical properties. At a solution temperature of 560°C and time of 120min, the elongation of the AA6061 extruded tube increases by 258%, the strength and the hardness dramatically decrease too. Therefore, the AA6061 tube meets the requirement of internal high pressure forming because of the improvement of formability. At an aging temperature of 180°C and time of 360min, the strength and hardness of AA6061 recover to the as-received alloy. The typical part of stepped shaft tube was successfully trial-produced in lab by using the present forming method. The maximum expansion ratio (MER) of the AA6061 extruded tube increases by 25%. The theoretical forming limit diagram (FLD) is also applied to analyze and predict the fracture trend of forming tube.

Study on Three-Way Pipe’s Internal High Pressure Forming Simulation

Internal high pressure forming is a kind of the modern plastic processing technology. Using liquid as the pressure transmitting medium, explore the effect of internal high pressure parameter on the three passing pipe technique, internal high pressure forming technique is applied on the three-dimensional shape parts deformation. In this study, we simulate the three-way pipe process by finite element software, analyze the forming force influence to the tube forming quality and get the changeable regulation of the pipe wall thickness with conclusion of the wall thickness variation, which provides the reference data and guidance for the actual production of the three-way pipe.

Analysis and Calculation of the Art of Internal High Pressure Forming

nternal high pressure forming is a new technology producing hollow light components. Due to the process of internal high pressure forming is very complicated with many factors, the dissertation will focus on the use of plastic-elastic force theory to acquire the hydraulic pressure needed and the tubes wall thickness in the final forming fillet. Based on the assumption of volume's incompressibility condition, we analyze and calculate the stress and strain of the tubes wall. Finally we estimate the formula of the hydraulic pressure needed in the forming process. The whole work can offer a concise formula to engineer in the infancy of designing. And it also is the great theoretical support to the development of the internal high pressure forming.

Formability determination of AZ31B tube for IHPF process at elevated temperature

Ring hoop tension test and tube bulging test were carried out at elevated temperatures up to 480 °C to evaluate the formability of AZ31B extruded tube for internal high pressure forming (IHPF) process. The total elongation along hoop direction and the maximum expansion ratio (MER) of the tube were obtained. The fracture surface after bursting was also analyzed. The results show that the total elongation along hoop direction and the MER value have a similar changing tendency as the testing temperature increases, which is quite different from the total elongation along axial direction. Both the total elongation along hoop direction and the MER value increase to a peak value at about 160 °C. After that, they begin to decrease quickly until a certain rebounding temperature is reached. From the rebounding temperature, they begin to increase rapidly again. Burnt structure appears on the fracture surface when tested at temperatures higher than 420 °C. Therefore, the forming temperature of the tested tube should be lower than 420 °C, even though bigger formability can be achieved at higher temperature.

Study on the Formability and Deformation Behavior of AZ31B Tube at Elevated Temperature by Tube Bulging Test

Internal high pressure forming of tube is widely used to form complex tubular part with different cross sections and curved axis. The ability of tube to undergo expansion deformation is crucial for the forming process. To evaluate the formability of AZ31B extruded tube, bulging test was carried out at different temperatures from RT up to 480 °C. Bursting pressure and maximum expansion ratio (MER) of the tube were obtained. The fracture surface after bursting was analyzed and compared with that obtained by tensile test along axial direction. Hardness changes in different positions along axial direction were also measured. Results show that the MER value remain almost unchanged from RT to 100 °C. In the temperature interval between 100 and 480 °C, an oblique N model can be used to describe the variation of MER value. The first peak and the bottom MER value occurred at 160 and 330 °C, respectively, and about 30.3% expansion ratio was reached at 480 °C. The bursting pressure decreased almost linearly as testing temperature increased. The fracture mode also changed from intercrystalline fracture to gliding fracture. However, burnt structure happened when the forming temperature was about 480 °C. The hardness value of the tube decreased significantly after the bulging test.

STRESS ANALYSIS ON CORNER OF RECTANGULAR SECTION IN TUBE HYDROFORMING

The stress distribution and deformation pattern of the comer are analyzed by mechanical analysis and numerical simulation, and then the mechanism of thinning and cracking at the transition region is disclosed. It is presented that the material at the transition region is the easiest region to satisfy plastic yielding conditions and produce thickness compressive strain. Therefore severe thinning deformation is easy to occur at the transition region and when the ratio of wall thickness to corner radius is bigger than 0.5, the difference of yielding conditions between straight side and corner is more significant so that the deformation nonuniformity is increased, and is easier to induce the excessive thinning and cracking. The result is useful for lightweight part design and process design of tube hydroform-ing (internal high pressure forming) to improve product quality.

Experimental and numerical investigation into useful wrinkling during aluminium alloy internal high-pressure forming

Internal high-pressure forming is a process for manufacturing lightweight components, especially automotive parts, with advantages of lower cost and weight reduction, better structural integrity and increased strength and stiffness over the conventional stamping process. One of the typical failure modes, including wrinkling, buckling and splitting, will occur through an unreasonable combination of the control parameters: the internal pressure and the axial punch feeding. In most previous papers, wrinkling is considered to be a failure mode. However, not all wrinkles are defects. The collection of materials in an expanding area by the formation of wrinkles is an alternative method for obtaining a preformed shape in the hydroforming die. In this case, the key point is to obtain ‘useful’ wrinkles instead of ‘bad’ wrinkles. In this paper, an investigation will be conducted on how to control the shape of the wrinkle waves and its effect on the thickness distribution after hydroforming by using finite element simulation. LS-DYNA finite element software is used in this paper. An experiment has been carried out and the results obtained from experiment and simulation are in good agreement.

Design of load-curves for hydroforming applications

Hydroforming or internal high pressure (IHP) forming is a manufacturing process which involves the use of internal pressure and axial loads to reshape components in a specially designed die piece. The internal pressure and axial force are defined as a function of time, and usually referred to as load-curves. This paper describes the principles involved in the design of load-curves for the simulation and production of a component part using IHP.

Liquid-bulge-forming as a flexible production method

This paper represents the structure of a flexible tool system for internal high-pressure metal forming, together with the forming possibilities that it opens up and looks into the results of studies that shows the applicability of the system.