Hydraulic forming (HF) has good forming accuracy, but causes the material to break easily. Electromagnetic forming (EMF) can greatly improve the forming limit of materials, but its shape control ability is poor. In this paper, the two techniques were combined, i.e., electromagnetic hydraulic forming (EMHF), to obtain a new high-strain-rate forming method, which was investigated through experimental and simulation studies. Three kinds of specimens were designed, and the forming limits of 5052 aluminum alloy were determined. The results show that EMHF specimens have higher forming height and limit strain compared with HF specimens. The increase in forming limit is due to the uniform dislocation distribution at microscopic level and inertia effect at macroscopic level. The simulation results show that the deformation velocity exceeds 55.6 m/s and strain rate exceeds 689.7 s−1. The experimental results are consistent with the simulated deformation contours, which proves the reliability of simulation. Flat bottom die and wave shape die were used to investigate the shape control ability of EMF and EMHF. The sheet and die can be closely fitted in EMHF. However, EMF has significant rebound effect and poor forming accuracy. Thus, better forming accuracy can be obtained if liquid is added in high-speed forming. The difference between EMHF and EMF formation mechanisms is essentially the difference of force action. EMHF not only retains the strong shape control ability of HF, but also greatly improves the forming limit of materials. It is a potential forming process that can be widely used in industrial manufacturing field in the future. 

Deformation behavior of 5052 aluminum alloy sheets during electromagnetic hydraulic forming

Titanium alloy sheets present inferior formability and severe springback in conventional forming processes at room temperature which greatly restrict their applications in complex-shaped components. In this paper, deformation characteristics and formability and springback behaviors of titanium alloy sheet at room temperature are systematically reviewed. Firstly, deformation characteristics of titanium alloys at room temperature are discussed, and formability improvement under high-rate forming and other methods are summarized, especially the impacting hydroforming developed by us. Then, the main advances in springback prediction and control are outlined, including the advanced constitutive models as well as the optimization of processing paths and parameters. More importantly, notable springback reduction is observed with high strain rate forming methods. Finally, potential investigation prospects for the precise forming of titanium alloy sheet in the future are suggested.

/pdf/deformation-characteristics-formability-and-springback-9nth6swm.pdf

Deformation Characteristics, Formability and Springback Control of Titanium Alloy Sheet at Room Temperature: A Review

https://link.springer.com/content/pdf/10.3103/S1067821221050060.pdf

Effect of Strain Rate on the Microstructure and Mechanical Properties of AA2B06-O Aluminum Alloy of the Al–Cu–Mg System

Abstract Impact hydroforming (IHF), as a novel sheet metal forming technology with the advantages of high strain rate forming and flexible liquid loading, is highly suitable for efficiently manufacturing aluminum complex-shaped sheet parts. In this paper, deformation characteristics of complex sheet parts under IHF are systematically investigated. The mechanical properties of 2024 aluminum alloy under a wide range of strain rates (10 −3 s −1 –3.3×10 3 s −1 ) were studied. It indicated that the elongation of 2024 aluminum alloy was improved by 116.01% under strain rates of 3.306 × 10 3 s −1 , referring to 10 −3 s −1 . Further, a complex-shaped part with symmetrical and asymmetrical structures was selected. The deformation characteristics of sheet and role of inertial effect under IHF were investigated with well-developed solid–liquid coupling finite element (SLC-FE) model with high accuracy. Differentiating deformation tendency is found for symmetrical structure with notably prior deformation at central zone, showing a “bulging” profile at initial forming stage. Whereas, synchronous deformation is presented for asymmetrical structure with a “flat” profile. Additionally, distinctive inertial effect was observed at different positions change for both symmetrical and asymmetrical structures, in which lower values were resulted at their central regions. Meanwhile, the inertial effect evolved with the impacting speed. Specially, larger difference of inertial effect was observed with increasing impacting speed. 

/pdf/deformation-characteristics-and-inertial-effect-of-complex-1vk1jex0.pdf

Deformation characteristics and inertial effect of complex aluminum alloy sheet part under impact hydroforming: experiments and numerical analysis

Tristal steel is low-carbon construction-type steel widely used in the automotive industry, e.g., for braking components. Given the contemporary demands on the high-volume production of such components, these are typically fabricated using automatic sequential machines, which can produce components at strain rates up to 103 s−1. For this reason, characterising the behaviour of the used material at high strain rates is of the utmost importance for successful industrial production. This study focuses on the characterisation of the behaviour of low-carbon steel via developing its material model using the Johnson-Cook constitutive equation. At first, the Taylor anvil test is performed. Subsequently, the acquired data together with the results of observations of structures and properties of the tested specimens are used to fill the necessary parameters into the equation. Finally, the developed equation is used to numerically simulate the Taylor anvil test and the predicted data is correlated with the experimentally acquired one. The results showed a satisfactory correlation of the experimental and predicted data; the deformed specimen region featured increased occurrence of dislocations, as well as higher hardness (its original value of 88 HV increased to more than 200 HV after testing), which corresponded to the predicted distributions of effective imposed strain and compressive stress.

https://www.mdpi.com/1996-1944/14/17/4821/pdf

Determining Johnson-Cook Constitutive Equation for Low-Carbon Steel via Taylor Anvil Test.

A novel method to evaluate the high strain rate formability of sheet metals under impact hydroforming

Stress relaxation tests were conducted on 5A90 (Al–Mg–Li) sheets using in-plane tension along various loading directions with different pre-strain levels to investigate the effects of stress relaxa...

Alina A. Bakinovskaya

Papers

A novel method to evaluate the high strain rate formability of sheet metals under impact hydroforming

Study of the ductility enhancement of 5A90 Al–Mg–Li alloy sheets with stress relaxation