Papers by Keyword: Tube Hydro Forming

Abstract: Forming limit curve (FLC) is an important tool for assessing formability of steel metal. It is commonly obtained from experiment, theoretical calculation and finite element method (FEM) simulation. In this study, the FLC of a seamed tube hydroforming is established by combining the failure criterion of strain increment ratio and FEM simulation. The numerical method is verified by tube bulge tests. Then the sensitivity studies are carried out to evaluate the effect of the geometrical features of seamed tube on its formability by numerical approach. Results show that the changes of the formability with the geometrical features of a seamed tube.

Abstract: Multi-way tube on air conditioning header is considered as the research objective .Finite element simulation method is utilized to simulate and analyze the influence of process parameters on branch height such as branch diameter、branches distance、branch numbers、tube thickness and die fillet radius. The result shows that with the increase of branch diameter, die fillet radius and tube thickness, the branch height increases. It also shows that with the increase of branch numbers and branches distance, the branch height decreases generally.

Abstract: In recent years, tube hydroforming has been considered by automobile and airplane industries, because it decreases weight and increases solidity of parts. For this reason, technical knowledge for manufacturing with better quality and accuracy has been developing. However, there are some probable defects in forming by hydroforming technique, which are bursting and wrinkling caused by improper loading paths. Therefore, it is very important to apply a proper path pressure proportional to axial feeding. In this research, firstly, tube hydroforming in a box-shaped die has been simulated by means of 3-D FEM in explicit dynamic software ABAQUSE 6.9-1. For prediction of these occurrences, different paths of pressure have been analyzed and then by comparison with obtained results from the simulation performed such as thickness distribution and final form of the tube, the range of pressure and axial feeding have been predicted. Accordingly, optimal range and loading path for hydroforming of box-shaped part without failure is determined. Considering the working conditions related to the same experimental tests and comparing these conditions with simulated results, efficiency and accuracy of the proposed method have been also investigated.

Abstract: Tube hydroforming with radial crushing (THFRC) process is particularly applicable to the tube which is difficult to shape due to lack of axial feeding. In this paper, the formability of the circular tube expanded into a triangle cross-section under the simple loading paths is explored by using the numerical simulation. The effect of the forming mode and the loading paths on bulged profile, wall-thickness distribution and the potential fracture location of the bulged tube are analyzed. The results showed that constraint conditions at tube ends have small influence on the bulged profile and wall-thickness distribution. Moreover, the larger the peak value of the internal pressure is, the better material filling ability and higher accurate the tube bulged profile are. Furthermore, the higher forming accuracy, the better material filling ability and wall-thickness distribution are gained in THFRC than those in free hydro-bulging (FHB) process, and they can be obtained under constant than linear pressure loading paths. Finally, the potential fracture location of the bulged tube in THFRC process is quite different from that in FHB process.

Abstract: Hollow parts with variable cross-section are widely used in the area of automotive and aerospace industries due to their excellent properties. Wrinkling is one of the most common forms of instability in the process of manufacturing the parts. The minimum curvature of the cross-section profile of bugled workpieces is proposed in this paper to as a wrinkling indicator to characterize the form and extent of the wrinkle. The wrinkle distribution of 1Cr13Mn9Ni1N stainless steel tube in hydroforming with radial crushing under linear and constant hydraulic pressures is analyzed and the influence of the bulging methods on the wrinkling is investigated via finite element simulation. The results indicate that wrinkling under constant hydraulic pressure is more obvious than that under linear one, wrinkling in hydroforming with radial crushing is more serious than that in free hydro-bugling, wrinkling on the cross-section away from the middle cross-section is more distinct and the wrinkling on the side edge is obvious than that on the bottom of the bugled workpiece.

Abstract: Hydroforming is an advanced process in automotive and aerospace industries to form metal tubes into desired shapes by high pressure fluid. The formation of a two layered tubes has been investigated both numerically and experimentally by a pressurized fluid fed into the internal tube through a nonlinear path with no axial feeding. The experimental setup including two units of die clamping system and pressure intensification system has been designed and built in Tarbiat Modares University. The internal and external layers of hydroformed tubes are used aluminum and copper alloys respectively. Effects of different friction conditions on tubes formability have been investigated. Finite element simulation is performed with LS-Dyna FE explicit code using ETA/Dynaform as the preprocessor. The simulation results show that the part can be formed successfully with the internal pressure of 61 MPa. The finite element results are in agreement with experimental results. It is also shown that imposing high friction condition for external tube and low friction condition for internal tube both will fail more likely.

Abstract: Considering the necessity of using light weight, high strength and corrosion resistant materials, automotive and aerospace industries need to use advanced production technologies. Hydroforming has been regarded as one of the new technologies in forming of aluminium and magnesium alloys. These alloys have very low formability at room temperature which will be improved at elevated temperatures. In this paper, AA1050 aluminium alloy tube is numerically and experimentally investigated at different temperatures. Thickness distribution in forming zone is studied under different thermal conditions. Numerical results have been verified by experiments and there is a good agreement.

Abstract: Tubular products have very important applications in various areas especially in the transportation industries. For instance, in the structure of cars there are various tubular products like roof headers, engine cradles, roof rails and frame rails with complex geometries which most of them need multiple steps like tube drawing, tube bending and hydroforming for their production. Based on the recent studies by this group, it was proven that in most of the structural tubular parts in the cars it was not necessary to have constant thickness along the axial direction of tube and it will be considered as overdesign and the overall weight of structures can be reduced considerably by using variable thickness tubes. In this paper, the variable thickness tube drawing and its applications in the tube bending and hydroforming applications were studied. The results showed that this process can have important role in reduction of defective parts in the production of complex tubes by the tube hydroforming method. However especial considerations should be taken into account in the design of thickness distribution along axial direction of these kinds of tubes to avoid problems in the drawing step and as well in the bending and hydroforming steps.

Abstract: In the last years many researchers were concentrating to develop and design new unconventional metal forming processes. Among such new technologies, tube hydroforming was proved as one of the most promising. Geometry of the tube and die were found to have significant effects on the hydroformed part. In this work, Response surface method was used based on data provided by Finite element modeling to construct a model for the bulge height as a function of geometrical factors for T-type bi-layered tube hydroforming. Interaction effects were analyzed and discussed.

Abstract: Tube hydroforming process is one of the metal forming processes which uses internal pressure and axial feeding simultaneously to form a tube into the die cavity shape. This process has some advantages such as weight reduction, more strength and better integration of produced parts. In this study, T-shape tube hydroforming was analyzed by experimental and finite element methods. In Experimental method the pulsating pressure technique without counterpunch was used; so that the internal pressure was increased up to a maximum, the axial feeding was then stopped. Consequently, the pressure decreased to a minimum. The sequence was repeated until the part formed to its final shape. The finite element model was also established to compare the experimental results with the FE model. It is shown that the pulsating pressure improves the process in terms of maximum protrusion height obtained. Counterpunch was eliminated as being unnecessary. The results of simulation including thickness distribution and protrusion height were compared to the part produced experimentally. The result of modeling is in good agreement with the experiment. The paper describes the methodology and gives the results of both experiment and modeling.