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. 

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

Effect of axial displacement on non-circular tube shaping in hydroforging

The hot metal gas forming process can significantly improve the formability of a tube and is suitable for the manufacturing of parts with complex shapes. In this paper, a double wave tube component is studied. The effects of different temperatures (400 °C, 425 °C, 450 °C and 475 °C) and different pressures (1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa and 3 MPa) on the formability of 6063 aluminum alloy tubes were studied. The influence of hot metal gas forming process parameters on the microstructure was analyzed. The optimal hot metal gas forming process parameters of 6063 aluminum alloy tubes were explored. The results show that the expansion rate increases with the increase in pressure. The pressure affects the deformation of the tube, which in turn has an effect on the dynamic softening of the material. The expansion rate of parts also increases with the increase in forming temperature. The increased deformation temperature is beneficial to the dynamic recrystallization of 6063, resulting in softening of the material and enhanced deformation uniformity between grains, so that the formability of the material is improved. The optimum hot metal gas forming process parameters of 6063 aluminum alloy tubes are the temperature of 475 °C and the pressure of 2.5 MPa; the maximum expansion ratio is 41.6%.

/pdf/effect-of-hot-metal-gas-forming-process-on-formability-and-2lw4ekki.pdf

Effect of Hot Metal Gas Forming Process on Formability and Microstructure of 6063 Aluminum Alloy Double Wave Tube

As one of the key safety components in motor vehicles, the steel wheel rim is commonly fabricated with the roll forming process. However, due to the varied cross-sections of the rim and the low formability of high-strength steel, it is difficult to produce thin-wall and defect-free wheel rims to realize the purpose of light weight. To solve these problems, a novel hydroforming process by combining internal and external pressures (HIEP) was proposed to produce thin-wall wheel rims in the current study. The designed initial tube with diameter between the maximum and minimum diameter of the wheel rim ensures dispersed deformation and effectively avoids local excessive thinning. During HIEP, a hydroforming process was performed with two successive stages: the external pressure and internal pressure stages. Theoretical analysis and finite element method (FEM) were jointly used to investigate the effect of process parameters on the wrinkling and thinning. With the optimized parameters for internal and external pressure, the wrinkling of wheel rims is prevented under compressive state during the external pressure forming stage. Additionally, HIEP was experimentally carried out with high-strength steel rims of 650 MPa ultimate tensile strength (UTS). Finally, wheel rims with weight reduction of 13% were produced successfully, which shows a uniform thickness distribution with a local maximum thinning ratio of 11.4%.

https://www.mdpi.com/1996-1944/15/19/6820/pdf?version=1665297851

A Novel Hydroforming Process by Combining Internal and External Pressures for High-Strength Steel Wheel Rims

Hydroforging is an innovative forming method used to form tubes with irregular cross-sections by using internal fluid pressure and axial force. Normally tube forming operations use solid mandrel to expand/bend the tube which does negative effect on tube or mandrel due to friction, buckling, and wrinkling. In this study, the tube material with various strain hardening exponents were hydroforged in a two-step numerical analysis with ramped fluid pressure and axial compression. The tube will be allowed to bulge with a ramped internal pressure and then shaped to a maximum expansion ratio by the axial compression in the shaping step. Some advanced materials exhibit the change in strain hardening exponent based on the plastic strain, the study focuses how the strain hardening exponent affects the deformation mechanics in tube hydroforging. It was found that the formability of tube during hydroforging is affected by the strain hardening exponent. The results show that tube can achieve a greater wall thickness reduction with increase in strain hardening exponent. Also, higher strain hardening exponent allowed tube to achieve a greater expansion ratio when axially compressed in the forging step. It was also observed that as the strain hardening exponent increases, the internal pressure requirements for the bulging and shaping steps decrease. The two model configurations of N01 and N02 failed from bursting and wrinkling, respectively, while every other model could form to the targeted disk-like shape. The forging step of the process showed that the die force for axial compression decreased as the strain hardening exponent increased for all successful models.

Deformation behavior of advanced high strength steel with different strain hardening exponents during tube hydroforging

The automobile exhaust manifold regularly has a multi-valved shape that used to be formed by the combination of stamping and welding. The current study intended to investigate and develop a tube hydro-mechanical forming (THMF) process to form an integral automobile exhaust manifold that has the characters of large deformation and small corner. It included three stages such as pre-forming stage, die-forming stage, and calibration stage. In addition, the non-feasibility of one-step hydroforming process was proved by FE modeling and experimental for the target component. An optimal loading path was obtained through the principle of dichotomy for pre-forming stage and die-forming stage, corresponding to the maximum thinning ratio of 19.7% and 13.27% respectively. The variation of stress and strain states were analyzed for the whole process. As a consequent, the thickness distribution exhibited a V-shaped along axial direction at each stage, while a fluctuated distribution after die-forming was presented along radial direction in the multi-valved area. For the final component, a maximum thinning ratio of 28.53% and the large deformation above 60% obtained from FE modeling kept a reasonable agreement with that achieved from experiments. It showed that THMF has advantages of not only decreasing the internal pressure but also improving the formability of tube.

Deformation characteristics in hydro-mechanical forming process of thin-walled hollow component with large deformation: experimentation and finite element modeling

Liang-Liang Xia

Papers

Deformation characteristics in hydro-mechanical forming process of thin-walled hollow component with large deformation: experimentation and finite element modeling