The present study consists of two parts. The first part supplies an exact semi-analytical solution for a general model of rigid plastic strain hardening material at large strains. The second part applies this solution to tube hydroforming design. The solution provides stress and velocity fields in a hollow cylinder subject to simultaneous expansion and elongation/contraction. No restriction is imposed on the hardening law. A numerical method is only required to evaluate ordinary integrals. The solution is facilitated using Lagrangian coordinates. The second part of the paper is regarded as an alternative to the finite element design of tube hydroforming processes, restricted to rather simple final shapes. An advantage of this approach is that the hardening law is not required for calculating many process parameters. Therefore, the corresponding design is universally valid for all strain hardening materials if these parameters are of concern. In particular, the prediction of fracture initiation at the outer surface is independent of the hardening law for widely used ductile fracture criteria. The inner pressure is the only essential process parameter whose value is controlled by the hardening law.

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A New Semi-Analytical Solution for an Arbitrary Hardening Law and Its Application to Tube Hydroforming

Abstract Nowadays, due to importance of the lightweight materials in industries and reducing the consumed energy, obtaining a lightweight material with high strength and stiffness is required. A combination of fiber and metal materials can close us reach our goal. Fiber-metal composite tube structures can be one of these ultra-hybrid materials which have high strength and stiffness with flexible material properties like fiber tubes which provide a light structure with improved performance compared to singular tube parts. In this research, a combined tubular structure of AL-6063 and carbon fiber was used. The free bulge hydroforming, lateral 3-point bending test, and axial compression were numerically and experimentally conducted to evaluate the effect of the carbon fiber on the AL-6063 tube. Also, a bi-layer AL-6063 tube was used to compare the result between a bi-layer of metal tube and the fiber metal tube laminates (FMTLs). The results demonstrated that the bi-layer tube of carbon fiber-Al can show a considerable performance in a high pressure while it is not a proper structure where a radial load is applied. 

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Effect of Carbon Fiber Reinforcement Composite on the Formability of Multi-Layer Tube Utilizing Hydroforming Technology

: Hydroforming has gained increasing attention in the manufacturing industry in recent years due to the demand for fast yet reliable production for parts, the applications of which accept a wide range of dimensional tolerances. In this study, tube hydroforming in conical dies has been analyzed. The study consists of two parts: computer simulations and experimental work. The simulation results were utilized to find the load paths which produce successful hydroforming for the selected tube specimens. Twelve load paths were identified and implemented with two friction coefficients and three pressure ranges. During the simulation process, the tubes were given an end movement that ranged from a sealing distance to twice that distance. The experimental work was implemented to verify some of the simulation results. The results showed that the best hydroforming limit was reached when the axial feeding was twice as much as the sealing distance. Also, the maximum amount of deformation rate happens shortly after the specimen-die interface starts having relative motion, and it is at its slowest when the hydroforming reaches the fully- formed specimen’s shape.

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Theoretical and Experimental Study of Conical Tube Hydroforming with One-Sided Axial Feeding

In order to achieve crack free elliptical shape under controlled conditions, an experimental set-up was designed and fabricated. This setup consists of three hydraulic cylinders, an intensifier, a hydraulic power pack, storage tanks, forming die, and all parts are controlled by a Programmable Logic Controller (PLC) system. The elliptical samples can be achieved through proper control of internal pressure and axial force with proper sealing. Experimental work has been carried out with different magnitudes of internal pressure and constrained conditions of axial force. Initially die of elliptical shape has been designed and modeled in Abaqus to successfully achieve the particular shape of the Al6061T4 tube under different internal pressure. The fabricated tube hydroforming machine set-up is highly effective for forming 0.5 mm-2 mm thick Al6061T4 alloy tube samples. The Experimental test has been carried out at 12.7 mm outer diameter, 175 mm length and 0.5 mm thick Al6061T4 samples. Bulge height parameters measured at different points of regular distance gap on the axial direction of the tube length and corner radius found at different pressures range of the samples are plotted under different internal pressures. Samples having an 18.7 mm major elliptical bulge were achieved during the experiment. The experimental data was validated by simulation results.

Experimental Study of Hydroformed Al6061T4 Elliptical Tube Samples under Different Internal Pressures

Due to the complex and structural characteristics of non-homogeneous layers in hydroforming, their forming is a challenging process. In this research, the manufacturing process of three-layered bellows made of 304 stainless steel (two outer layers) and Inconel 718 (inner layer) is numerically investigated. The effects of different parameters on the forming of bellows are studied. To study the effect of friction between layers, two models are used; a model with friction between layers and a model with tied layers. It is observed that the amount of displacement in the model with a tie connection is more. The maximum values of stresses are detected in the inner region after the second stage of forming, i.e. folding. These values reduce after the spring-back step.

Numerical analysis of forming the tri-layer non-homogeneous bellows via the hydroforming process

The objective of this study is to improve the bulging and minimize the thinning ratio to enhance manufacturing of components in Industries. Tube hydroforming is an advanced manufacturing technology used for making intricate and complex tubular parts which required less cycle time. This research focuses on hydroforming process, formability and process parameters design to replace the conventional tube bending, welding and cutting operations. The prediction of parameters is done by applying numerical and experimental approach. During experimentation the pressurized fluid is used to deform the tubes in a plastic deformation. In this study, two types of grade materials are used such as AISI304 and AISI409L of 57.15 mm external diameter with 1.5 mm thickness in the form of electric resistance welded tubes to measure stain path, thinning and bulge height. However, it is observed that the internal pressure and L/D ratio are effective parameters in both numerical analysis and experimentation. In axial feed condition, it is observed that 16.3% thinning in weld region and 44.6% thinning in base metal region, whereas, in fixed feed condition, it is observed that 7.7% thinning in weld region and 18.6%thinning in base metal region for L/D = 1 and L/D = 3 respectively. The numerical analysis with experimental results shows a very good match. It is seen that the axial feed leads to better formability with fixed feed condition because in axial feed condition material supplies towards the center of the bulge tube. The feasibility of the hydroforming process for manufacturing of AISI304 and AISI409L grade material as per the requirements of the industries is also checked. The maximum bulging is observed in L/D = 2 by comparing with the other ratios. This process can be effectively used for AISI304 grade material because the formability is better than AISI409L.

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Predictions of formability parameters in tube hydroforming process

The purpose of this study is to improve the bulging and minimise the thinning ratio so that manufacturing processes will be improved in Industries. Tube hydroforming is an advanced manufacturing te...

Bapurao G. Marlapalle

Papers

Predictions of formability parameters in tube hydroforming process

Numerical and experimental predictions of formability parameters in tube hydroforming process