---

In recent years, rubber pad forming process have many advantages, such as high flexibility, good surface quality and lower manufacturing costs; RPF have been widely used in automotive, aerospace and military industries. In present research, numerical and experimental analysis of free bulging 304 stainless steel seamed tube, using a polyurethane elastic pad has been studied. Firstly, 3D simulation of seamed tube bulging using the finite element ABAQUS/Explicit 6.12 software by several frictional conditions has been performed. An incompressible hyperelastic pad has been modeled by Mooney-Rivlin constitutive equation and the elastic-plastic behavior as more as progressive ductile damage criterion FLD for steel tube were assumed. In the experimental activity, compression test of rubber was carried out according to ASTM D575-91 standard and compressive stress-strain curve and the Mooney-Rivlin constants were determined. Forming of meshed tubes by using elastic pad with different lubricating systems have been conducted up to onset of bursting in the seam weld and longitudinal, hoop and thickness strains were measured. Results showed that friction, especially between rubber and tube plays the main role in controlling wrinkles, increasing the bulge depth, reducing the forming load and friction dissipation energy of the process. Also observed that the intact parts without any wrinkles formed by using nylon lubricant between tube and rubber and drawing oil between tubes and die.

---

Bulging with elastomer tool has been used in the production of integrated hollow parts as one of flexible forming methods. Nowadays, most industries such as Aerospace and military are using flexible die forming methods due to their flexibility, high quality and lower cost. In this research, finite element simulation has been implemented by ABAQUS software to investigate the behavior of stainless steel 304 tube bulging process using elastomer tool. By comparing the geometry of deformed tubes in experimental tests and simulation results, the FEM model was verified. The aim of this study is to determine the process factors and their effects on the average thickness and depth of bulged tube. In this regard, design of experiment (DOE) was performed using a full factorial method and the results were interpreted using analysis of variance (ANOVA). Also a regression model was presented to predict these responses. Results showed that among the studied factors, friction (between tube and rubber), rubber height, punch displacement and tube axial feeding have significant effects on the process. Finally, the optimal values for significant factors were presented.

---

The ECAP-Conform is one of the newest and less known processes that improve mechanical properties. In the present study, the effective parameters of the ECAP-Conform process for AA7075 have been investigated. Influence of parameters such as roller radius, bending angle, die channel angles, rod/roll friction coefficient, rod/die friction coefficient, and the aspect ratio of the die groove on the torque, the applied force on the die, the stress, and the effective plastic strain, the output rod curvature, and the strain distribution uniformity have been investigated. The design of experiments was carried out based on the response surface method by the Minitab software, and simulations were performed using the ABAQUS software. To validate the FEM, the ECAP-Conform process of AA7075 rod was performed and the comparison of experimental and numerical results have acceptable compliance (7.5% error). It was found that the die channel angles and the rod/die friction coefficient have a more significant effect on all responses. Moreover, to maximize the imposed strain and strength, and to minimize the process torque and curvature, as well as achieving a uniform distribution of strain, the optimal output parameters have been obtained.