Mechanism on increased sheet formability induced by tangential adhesive stress in sheet flexible forming process employing viscoplastic pressure-carrying medium

Xiang, Nan; Wang, Zhongjin; Cai, Shupeng

doi:10.1016/j.ijmachtools.2018.04.008

Cited by 26 publications

(5 citation statements)

References 25 publications

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“…In VPF, the flowable semisolid polymer with high viscosity is applied as the pressure-carrying medium. The viscous medium transmits the non-uniform pressure onto the sheet, causing it to deform [48,49].…”

Section: Control Of the Uniformitymentioning

confidence: 99%

Effect of the non-uniform pressure on the deformation and instability of the sheet in flexible-die bulge forming

Wang,

Wang

2024

Preprint

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In recent years, the application of non-uniform pressure in flexible-die forming, such as viscous pressure forming and magnetorheological pressure forming, has been utilized in manufacturing many thin-walled components. However, the non-uniform pressure is mainly applied to change the shape of the sheet. The effects of the non-uniform pressure on thickness reduction and fracture are still intricate. In this study, the mechanism of the non-uniform pressure to decrease thickness reduction and delay fracture instability in the bulge test is revealed. The non-uniform pressure changes the principal stresses, causing distinct deformation behaviors. There are two opposite effects on thickness reduction and fracture instability. If the pressure at the bulged pole decreases, the shape is more prolate, leading toa decreased average thickness and a decreased polar curvature. The thickness reduction tends to be severe, and the diffuse necking is easy to produce. If the pressure at the bulged pole increases, the shape is more oblate, leading to an increased strain gradient. The thickness reduction tends to be severe, and the localized necking is easy to produce. Characteristics of the pressure to decrease thickness reduction and delay instability are presented. Viscous pressure bulge tests are carried out. Experiment results of the shape, thickness uniformity, polar strain, and fracture verify the theory. The fracture strain increases by 5.6 % compared with the uniform pressure condition. This study proves that non-uniform pressure can promote sheet formability, indicating that non-uniform pressure has broad application prospects in sheet metal forming.

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Section: Control Of the Uniformitymentioning

confidence: 99%

Effect of the non-uniform pressure on the deformation and instability of the sheet in flexible-die bulge forming

Wang,

Wang

2024

Preprint

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“…For simplified single curvature stretch bending model, convex radius of the die was assumed to be 1126 mm, initial length of the sheet was taken as 2900 mm, and the width was set as 140 mm. Also, 4-node quadrilateral Belytschko-Tsay (BT) shell elements were used to mesh sheet metal and die, using respectively 6776 and 7182 elements; 8-node hexahedral solid elements (27,104 elements in total) were used to mesh the rubber sheet. Five elements were meshed in thickness direction of the rubber.…”

Section: Finite Element Modelmentioning

confidence: 99%

“…When softer rubber was used, sheet blank did not fully fill the die cavity due to the large amount of lateral squeeze flow caused by pressure buildup. Except for rubber pad, variation of mechanical properties of flexible dies, such as mineral oil, viscous medium [27], and MR fluid [28,29], are commonly recognized to be able to change the friction condition and influence the stress and strain state in sheet metal forming.…”

Section: Introductionmentioning

confidence: 99%

Improved forming accuracy through controlling localized sheet metal deformation in the friction-assisted stretch bending process

Xiang

Shu

Wang

et al. 2021

Int J Adv Manuf Technol

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Tension-dominated stress state in the stretch bending process probably leads to localized tensile stress, especially in the manufacture of thin-walled, high-strength, or complex-shaped components. That results in nonuniform residual stress distribution and inferior shape accuracy. In this paper, a friction-assisted stretch bending (FASB) process is proposed to deal with this problem. A rubber sheet is attached with sheet metal to generate tangential friction at rubber/metal interface. The tangential friction assists in modifying stress distribution in the loading process. Finite element analysis was conducted to determine the effects of process parameters on deformation behaviors of the sheet metal. The results show that a rubber sheet with hardness ranging from Shore 57D to 70D and a rubber/metal thickness ratio (ξ) value around 1.0 can effectively reduce sheet metal thinning and decrease springback in the stretching and bending stress states. By taking the simulated process parameters as a reference, fuselage profiles with variable bending curvature and sections were successfully manufactured. Maximum thinning ratio of the formed part was 6.1%, and the section deviation after unloading was reduced by 52.9%, on average, compared with conventional stretch bending. The improved forming accuracy can be attributed to the relatively uniform distribution of longitudinal stress. That results in uniform elastic recovery in longitudinal direction. Further industrial application of the FASB process for the manufacture of large-sized and complex-shaped parts will be expectable.

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“…In addition to that, Xiang et al [29] applied a high-viscosity polymer to increase the formability in the bulging of SUS321 tubes and employed an analytical model of the viscous pressure bulging process for tubes via an extended M-K model. In the results, they reported that the tube can be formed under larger internal pressure before fracture by using the viscous medium with higher molecular weight and that the viscous medium leads to an increase in thickness shear strain and sheet formability.…”

Section: Introductionmentioning

confidence: 99%

On Improving Sheet Metal Formability in Hydrodynamic Deep Drawing Process through a Solid‐Oil‐Type Mineral Grease Pressure Medium

Modanloo,

Akhoundi,

Lee

et al. 2023

steel research int.

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In this research, the improvement in sheet metal formability obtained through the utilization of a mineral grease in solid oil type (SMG) pressure medium in the hydrodynamic deep drawing process assisted by radial pressure (HDDRP) was investigated by experiments and finite element method (FEM) simulations on flat‐bottom cups realized with pure copper and DIN 1.0338 steel. To determine the process parameters ranges, a FEM model was developed in ABAQUS/Explicit and validated against experimental results. Afterward, experiments were carried out using two pressure mediums with different viscosities, id est water, and SMG. Considering the results relevant for both sheet materials, the SMG medium allowed an average reduction of the sheet metal thinning of 15% and 10% on the corner edges while also granting a negligible thickness variation on the cup walls. On the other hand, the higher viscosity of the SMG, in comparison to the water medium, also resulted in an average 16% increase in the forming force when compared to the water pressure medium.This article is protected by copyright. All rights reserved.

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Mechanism on increased sheet formability induced by tangential adhesive stress in sheet flexible forming process employing viscoplastic pressure-carrying medium

Cited by 26 publications

References 25 publications

Effect of the non-uniform pressure on the deformation and instability of the sheet in flexible-die bulge forming

Effect of the non-uniform pressure on the deformation and instability of the sheet in flexible-die bulge forming

Improved forming accuracy through controlling localized sheet metal deformation in the friction-assisted stretch bending process

On Improving Sheet Metal Formability in Hydrodynamic Deep Drawing Process through a Solid‐Oil‐Type Mineral Grease Pressure Medium

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