FEM analysis of tube pre-bending and hydroforming

Lin, Gao; Strano, Matteo

doi:10.1016/j.jmatprotec.2004.04.076

Cited by 24 publications

(6 citation statements)

References 7 publications

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“…The hydraulic expansion method was studied by Hwang and Altan 3 in the case of a circular tube expanded to a rectangular cross-section. The hydroforming process of aluminium tubes was investigated by Abrantes et al, 4 whereas the expansion of stainless-steel tubes using the hydroforming process was studied by Gao and Strano, 5 and this process optimised the pre-bending phase using numerical simulations. In the same field, a control algorithm in combination with FE models was developed by Ray and MacDonald 6 to optimise the hydroforming process of the tubes.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the mechanical expansion process of thin-walled tubes for air heat-exchanger production

Scattina

Avalle

2022

Proceedings of the Institution of Mechanical Engineers, Part B:

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Finned tube air heat-exchangers are built by joining the tubes to the fins by various techniques. A technique mostly used for large heat-exchangers consists of fitting the tubes into the holes of the fins by expanding the tubes using a mechanical process. The expansion is achieved by inserting an ogive of a larger diameter into the tube. The intimate contact of tubes and fins due to the press fitting ensures the proper thermal connection. This work tries to describe an experimental-numerical procedure useful to study and predict the mechanical process and the process parameters. The procedure, based on material properties obtained from tensile tests and the use of the inverse method to identify the material parameters, is based on bi-dimensional finite element (FE) models used to simulate the expansion process. The FE model is then used for process optimisation regarding such parameters as the ogive shape and ogive sizes, friction coefficient and speed of insertion of the ogive into the tube. Indeed, size and shape uncertainties strongly influence the process parameters and the process quality, as well as the heat-exchanger efficiency. The use of numerical models was proven highly effective in predicting and optimising the process by quickly analysing the influencing factors and optimising the production.

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Section: Introductionmentioning

confidence: 99%

Analysis of the mechanical expansion process of thin-walled tubes for air heat-exchanger production

Scattina

Avalle

2022

Proceedings of the Institution of Mechanical Engineers, Part B:

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“…Prabhu [5] pointed out that the process parameter of pre-bending has an important effect on HPTH, and found that the formability could be improved with the increase of bending radius. Gao [6] proposed that the reduction of friction coefficient can help lighten the degree of thickness thinning during pre-bending, which is also beneficial to alleviate the cracking defect after HPTH. Han [4] proposed a method to adjust the contact sequence of tube and die surface to solve the inhomogeneous deformation problem in hydroforming of a bending tube, effectively controlling the cracking defect.…”

Section: Introductionmentioning

confidence: 99%

An Investigation Into the Effect of Pre-bending on the Tube Hydro-forging Technology

Lin

Chu

Sun

2021

Preprint

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Tube hydro-forging (THFG) combining with the pre-bending is an advanced method to manufacture the complex cross-sectional tubular component with curved axis. However, the effect of pre-bending on the subsequent THFG, especially on the critical internal pressure required to inhibit wrinkling, has not been clarified yet. Therefore, this paper makes a detailed study on it. At first, based on the energy method, the change rule between the critical internal pressure and the hoop strain was established when pre-bending was considered. Subsequently, the mechanics condition difference between single and double curvature differential segment during THFG was analyzed. Via the plastic theory, the distribution of hoop strain could be obtained. Mainly due to the uneven distribution of thickness and cold work-hardening caused by pre-bending, the maximum hoop strain at the outer straight-wall was greater than that at the inner straight-wall during THFG. Substituting the maximum hoop strain at the outer/inner straight-wall into the change rule, then their mathematical model of the critical internal pressure to restrain the wrinkling could be solved respectively. Finally, the critical internal pressure considering pre-bending was determined by that of outer straight-wall, and its value was always greater than the critical internal pressure without considering pre-bending under the same punch stroke. With the increase of bending radius, the critical internal pressure difference between considering and not considering pre-bending also increases. When the bending radius was 250 mm, the critical internal pressure difference was 33%, while it increased to 74% as the bending radius reduced to 100 mm, all of which were verified by experiment. The effect of friction coefficient on the critical internal pressure was also studied. In conclusion, this work provided a new and more accurate prediction model of critical internal pressure to guide practical production for when existing the pre-bending.

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“…Therefore, in order to improve the section quality, frictions between mandrel, wiper and tube should be decreased, but the frictions between the pressure die, bending die and tube should increase. Gaoa and Strano (2004) made a research on the effect of friction on the quality of tube pre-bending and hydroforming. In that paper, process variables such as the friction coefficient, tube material and pre-bent tube radius were analyzed.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical investigation of friction coefficient effects on defects in horizontal tube bending process

Kahnamouei

Fattahi

2015

jtam

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The aim of this paper is to investigate defects in a thin-walled tube bending process (without using mandrel and booster) and effects of friction between the dies and tube on wrinkles. In the tube bending process, there are several effective parameters such as wall thickness, outer diameter-to-wall thickness ratio, centerline bending radius-to-outer diameter ratio and friction coefficient. Any mismatch in the selection of the process parameters would cause defects inducing undesirable variations in wall thickness and cross-section distortion. In this work, firstly, tubes with several wall thickness values are bent, and the final depths of wrinkling and wall thickness change are reviewed. Then, to study the process numerically, numerical simulations are carried out. Then, a series of experimental tests are carried out to verify the simulation results. A comparison between numerical and experimental results shows a reasonable agreement. Finally, in order to obtain a suitable friction condition, the effects of friction coefficients on defects are studied. For this purpose, a series of simulations has been carried out. It shows that at a certain friction coefficient, a minimum wrinkling depth can be observed and variations in the friction coefficient between the dies and tube has no effective influence on wall thinning and thickening.

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FEM analysis of tube pre-bending and hydroforming

Cited by 24 publications

References 7 publications

Analysis of the mechanical expansion process of thin-walled tubes for air heat-exchanger production

Analysis of the mechanical expansion process of thin-walled tubes for air heat-exchanger production

An Investigation Into the Effect of Pre-bending on the Tube Hydro-forging Technology

Experimental and numerical investigation of friction coefficient effects on defects in horizontal tube bending process

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