Papers by Keyword: Hydroforming

Abstract: The reshaping approach is widely considered a virtuous strategy in line with the pillars of the Circular Economy. According to this approach, End-of-Life (EoL) components are subjected to a second forming process to achieve a new functional geometry. However, EoL parts often exhibit a non-uniform thickness distribution and work-hardened zones resulting from the primary manufacturing step, which makes the design of the reshaping step not trivial. Beyond the standard objectives like avoiding fracture and minimizing springback during the reshaping operations, one of the most concerning aspects is the complete removal of the geometrical features coming from the initial forming process. Flexibility and versatility of the forming process are unavoidable requirements to make the reshaping successful. Therefore, three different reshaping routes are numerically investigated in the present work: (i) reshaping by hydroforming (RH) at room temperature; (ii) reshaping by gas forming (RGF) at hot temperature; (iii) a hybrid approach, based on the combination of an intermediate deformation step via Single Point Incremental Forming followed by sheet hydroforming (RHA). The three routes share the same EoL, characterized by the presence of a deep-drawn square feature. Comparing the three routes, in terms of final shape and thinning distribution, with a reference case study (represented by the sole hydroforming process carried out on an undeformed flat blank) allowed to conclude that the feature removal and a non-severe thinning could not be achieved simultaneously: in fact, while RGF and RHA ensure a more evident suppression of the pre-existing feature, they simultaneously induce a more pronounced and localized thinning compared to the RH route.

Abstract: Forming Fiber Metal Laminates (FMLs) is still challenging. There are some inherent limitations to forming smaller and complex-shaped FML parts. In particular, the process parameters have a major impact on the final FMLs part. In this paper, several investigations were conducted to optimize these process variables. In the investigations, different Blank Holder Gap (BHG) thicknesses were used to predict the optimal range; variable Blank Holder Force (BHF) and Cavity Pressure (CP) were chosen to make the results more convincing. Based on the numerical analysis, it is found that the optimum BHF should be between 10 to 15 KN; CP has a range from 8 to 10 MPa; optimum BHG should be 1.0 mm. And through using these predicted process parameters, a successful Glare cup has been formed. Furthermore, the forming performance of the Glare material is improved and the laminate has shown better formability. Finally, optimized process variables can be used for mass production of FMLs parts.

Abstract: Recently, hydroforming was developed to address the emerging problems encountered by the conventional rigid tool-based deep drawing process. Hydroforming is a specialized type of die forming process, that uses a rigid die while the pressure provided by the liquid acts as a punch to shape the sheet metal. The current paper is directed to study the hydroforming process numerically and experimentally as a means for shaping aluminum alloy sheets based on the quality of product thickness variation and surface roughness. Moreover, it offered a comparative investigation of the experimental and numerical findings of this process. Therefore, thickness variation has been calculated numerically by designing a numerical model using Marc software which fits in large deformation simulation. On the other hand, thickness variation and surface roughness were measured experimentally along drawn cups and compared with the numerical results. The numerical results of thickness variation are matched with the experimental results. Furthermore, surface roughness was measured and compared before and after drawing at five regions. Since there is no contact between the upper side of a cup and any metallic parts, surface roughness depends only on the effect of plastic strain and was found to be increased in all regions.

Abstract: This paper deals with the hydro-forming of a flat thin metallic disc to achieve a forward domed disc which will be subsequently adopted to manufacture a rupture disc. The plastic deformation induced by the hydraulic energy is numerically simulated through an isotropic hardening plasticity model using a non-linear explicit finite element analysis (FEA). The variation in disc’s central deformation, thickness, equivalent plastic stress and equivalent plastic strain with respect to the applied hydraulic pressure are determined from FEA simulations. The hydro-forming setup is then designed and manufactured, and the metallic disc is experimented under hydro-forming process. The reduction in thickness due to stretching of the thin disc is evaluated from experiment and simulation and a close agreement is found. This research attempt helped in finalizing the hydro-forming fluid pressure, the feasibility and the accuracy of practically achieving the desired geometry of the metallic disc. The near-fixidity effects on abrupt variation in sheet thickness and plastic strain are well captured through simulations which are very difficult to be studied through hydro-forming experiments.

Abstract: Hydroforming process is used for obtaining different kinds of sheet metal components in an economic manner in terms of time and costs reduction and increase of the product quality. This paper deals with the application of this type of technology for manufacturing a rotational auto part from aluminium alloy. An experimental tool for hydroforming with rubber membrane was used. A set of dies with different geometries has been designed and constructed. Experiments have been conducted for investigation the ability of transferring features from the die onto the blank surface for different die geometries and pressures. The hydroformed part was measured using CMM. Based on the experimental data a numerical model was designed. FEM using Abaqus solver was used for investigated the part geometry and the effective stress distribution under various pressures conditions and dies geometries. The experimental and simulation results show the feasibility of applying the sheet hydroforming process in order to obtain a sound product.

Abstract: Lead or low temperature melting alloys have been sucessfuly utilized as a filling medium in tube forming processes, such as bending and bulging; however, strict lead-free-control plan in industries have prohibited the use of lead in recent years. The authors suggest the use of fiber-reinforced ice (FRI) as an alternative. Fiber of recycled paper was utilized for the preparation of FRIs, and the results of compression tests revealed that the fabricated FRIs exhibit sufficient crushing-strength suitable for use as an alternative for lead-filled media. However, the high density of the fiber in the mixture of fiber and water makes it difficult to fill a tube with the fiber in the pre-freezing process owing to its high vscosity. Therefore, it is useful to examine other strong fibers for FRIs to reduce the ratio of the fiber. In this study, the authors examined glass fibers as reinforcement in FRIs. Compression tests were conducted at various crosshead speeds, and the difference in the stress-strain behaviors of the FRIs with glass fiber and paper-pulp fiber was analyzed.

Abstract: In this paper, the authors discuss process planning for the lateral extrusion of a pipe with a lost core. In this process, maximum longitudinal length of the bulged part is restricted by the balance of the extrusion speed of the material and the lost core. In the free bulging condition, longitudinal length is limited to the pipe radius, because the extrusion speed of the core is slower than that of the pipe material when the longitudinal length of the bulged part is longer. The authors designed a two-stage forming process using the transit shape of a truncated cone to solve this problem. The dimensions of the truncated cone were estimated through trial-and-error using a commercial FEM simulator and considering the stretch effect for wrinkles of the pipe by deformation and traveling of the lost core. Finally, the authors conducted experiments to confirm the design’s validity. As a result, a longer longitudinal length of the bulged part than the pipe radius was successfully obtained.

Abstract: The work is focused on hydroforming of T-shape connector for high temperature applications. A seamless part for use in industrial applications was formed in a high pressure liquid extrusion process. Due to the occurrence of faults in the final products, numerical simulations were conducted to reveal the possible sources of such failures. The numerical simulation took into account precisely determined boundary conditions allowing proper selection of processing parameters. The microstructure of charge material as well as that of the final product was also examined. Numerical simulations of the investigated extrusion process showed the possibility of obtaining good quality product, however, the quality of final part is strongly influenced by properly designed heat treatment schedule.

Abstract: The application of finite element method (FEM) in the area of metal forming and material processing has significantly increased in the recent years. The presented study provides details of the development of a finite element modelling approach to form a part via sheet hydroforming (SHF) process. Both FEM analysis and experimental trials were introduced in this study to produce a complex shape component from Inconel 718 material. The FEM provides a robust feasibility study for forming this part in terms of blank design, load path and process design optimisation. The simulated hydroformed part was validated by performing experimental trials. The analysis demonstrated close correlation between the predicted FE model and the physical trial.

Abstract: In this work, the hydroforming process in warm conditions was used for manufacturing an Al-Mg alloy (AA5754) benchmark component displaying different strain levels due to its geometry. The attention was focused on the effect of the rate to increase the forming pressure (PR), strictly related to the strain rate the material is subjected to. In fact, preliminary tensile and Nakajima tests (both at room temperature and in warm conditions) revealed that the mechanical and formability properties of the investigated alloy are strongly affected by the strain rate. Warm Hydroforming tests were conducted in order to investigate both the working temperature and the parameter PR. The Blank Holder Force profile was varied according to an experimentally determined profile able to avoid oil leakages. Experimental results were collected in terms of output variables related to the die cavity filling and to the strain level reached on the component: in such a way a multi-objective optimization could be carried out using the commercial integration platform modeFRONTIER. The best compromise between the high level of the component deformation and the cycle time could be obtained by conducting the warm hydroforming process at the temperature of 250°C and setting the parameter PR equal to 0.1 MPa/sec.