Bimetal cup hydroforming of Al/St and Cu/St composites: Adaptive finite element analysis and experimental study

Journal of Mechanical Science and Technology - An adaptive Finite element analysis (FEA) was proposed in this paper for the industrial design of bimetal conical-cylindrical cup hydroforming....     

Feasibility study on optimized process conditions in warm tube hydroforming

Feasibility study has been performed to estimate the optimized process conditions in warm tube hydroforming based on the simulated annealing optimization method. Precise prediction and control of process parameters play an important role in forming at warm conditions. Optimal pressure and feed loading paths are obtained for aluminium AA6061 tubes through the simulated annealing algorithm in conjunction with finite element simulations. Numerous axisymmetric geometries are investigated and the effects of expansion ratio, corner fillet to thickness ratio, and initial diameter to thickness ratio are studied. For the feasibility estimation, warm hydroforming experiments have been conducted on aluminum AA6061 under optimal designed conditions. The results show that the optimization procedure used in this research is a reliable and feasible tool in determination of optimal process conditions for the sound warm hydroforming process.     

Evolution of microstructure and mechanical properties of SUS430/C11000/SUS430 composites during the laser-forming process

Multilayered sheet metals have been widely used to achieve a wide range of favorable mechanical, physical, thermal and electrical properties. Laser beam irradiation over these materials creates extreme temperature changes that can lead to changes in the microstructural properties. Microstructure plays a very crucial role in determining the mechanical property of the irradiated region, thus determining the optimum laser processing conditions. In this study, metallographic studies, as well as tensile, fatigue and hardness tests, are undertaken on SUS430/C11000/SUS430 laminated composites that have been exposed to laser irradiation with different number of passes. This composite can be used in the microelectronics industry since it has the anti-corrosion and strength capability of stainless steel, and the electrical superiority of copper. Ytterbium fiber laser is used in such a way that the governing mechanism of the process is the temperature gradient mechanism. Evolution of the microstructure is revealed by metallography, and the fracture levels of tension and fatigue test specimens are further evaluated by SEM. This study illustrates the significant effects of successive laser irradiation on the evolution of microstructure and mechanical properties, which lead to some suggestions for improving the properties of laser-formed SUS430/C11000/SUS430 composites.     

The effect of tube dimensions on optimized pressure and force loading paths in tube hydroforming process

The precise control of internal pressure and axial force loading paths significantly affects the final product quality. In this study, the effect of tube dimensions on the pressure and force loading paths in tube hydroforming process is investigated by using simulated annealing optimization method linked to a commercial finite element code. The optimized loading paths, obtained for different tube geometries with a constant expansion ratio, are then compared. The effects of initial diameter and wall thickness on shape conformation, optimal internal pressure and axial force (or feed) are discussed on the basis of optimal loading paths. Several guidelines in prediction and determination of tube hydroforming parameters are obtained by optimization analysis.     

Characterization of laser bending of SUS304L/C11000 clad sheets

Journal of Mechanical Science and Technology - Laser bending process is an advanced method for manufacturing of various bends on different types of materials. The combination of different metals...     

Study of Al/St laminated sheet and constituent layers in radial pressure-assisted hydrodynamic deep drawing

In this research, radial pressure-assisted hydrodynamic deep drawing of single- and bilayer cups is studied using finite-element and experimental methods. The reason for using laminated composites is to take the combinatorial benefits of single materials, such as higher strength-to-weight ratio, improved corrosion and abrasion resistance, more favorable thermal and electrical characteristics, and even lower commercial price. Safe forming area and probability of failure occurrence are predicted for both single- and bilayer sheets using 3D process window diagram (PWD) as a practical tool based on the effective geometrical parameters on the pressure-drawing ratio. The effects of layers arrangement on the forming behavior of laminated sheets were also analyzed in different pressure loading paths. The results show that the aluminum/steel composite has a wider forming pressure range, higher drawing ratio and lower geometrical limitations compared with the single-layer aluminum in identical conditions. It is found that a thin layer of steel as the outer layer improves the formability of aluminum.     

Feasibility of underwater laser forming of laminated metal composites

Laminated metal composites are of great interest in various industries. Previous studies demonstrate undesired mechanical or microstructural changes in these composites during the laser forming process due to rapid temperature gradient. In this research, underwater laser forming is proposed to minimize this effect. This process could also be an effective method for on-site forming or repairing of large metal/composite sheets used in underwater applications, such as marine equipment, ships, and lake/sea-based offshore oil platforms. The underwater laser forming process is performed experimentally on a three-layered stainless steel/copper/stainless steel composite and compared with the results of in-air tests. Total forming time, bending rate, and microstructural changes are compared for both underwater and in-air conditions. The effects of forming parameters, such as the number of irradiations, laser beam velocity, diameter, and power, are also compared and discussed. It is shown that the bending angle per irradiation in underwater forming is significantly lower in comparison with in-air condition, but the production time is less due to the elimination of cooling time. Also, the microstructure of stainless steel at heat-affected zone was unchanged, and the hardness of upper layer experienced smaller changes when formed under water. The underwater laser forming process is demonstrated to be feasible and can be applied for underwater applications with a high degree of reliability.     

Process analysis of two-layered tube hydroforming with analytical and experimental verification

Two-layered tubular joints are suitable for special applications. Designing and manufacturing of two layered components require enough knowledge about the tube material behavior during the hydroforming process. In this paper, hydroforming of two-layered tubes is investigated analytically, and the results are verified experimentally. The aim of this study is to derive an analytical model which can be used in the process design. Fundamental equations are written for both of the outer and inner tubes, and the total forming pressure is obtained from these equations. Hydroforming experiments are carried out on two different combinations of materials for inner and outer tubes; case 1: copper/aluminum and case 2: carbon steel/stainless steel. It is observed that experimental results are in good agreement with the theoretical model obtained for estimation of forming pressure able to avoid wrinkling.