Indentation forming is an internal tube forming process in which a mandrel with a diameter slightly larger than that of the tube is pressed inside the tube and in so doing, creates the internal profile. Forming forces have a significant effect on the spring back, residual stress, quality of the inner surface, quality of tube dimensions, and tool wear. In this study, the forming process of CK45 steel tube by carbide tungsten tool in the presence of ultrasonic vibration has been simulated and the effect of ultrasonic on the forming mechanism has been investigated by introducing two regimes according to the forming conditions. The effects of tool feed-speed and amplitude of vibration on forming force reduction have been investigated. According to the simulation results, the main reason for the force reduction in the presence of longitudinal tube ultrasonic vibration is the intermittent phenomenon which is the continuous or impulsive regime. The critical amplitude which determines the borderline of continuous and impulsive regimes is obtained 38μ m by the simulation of the process. The maximum force reduction obtained in continuous regime is 64. 2% at the critical amplitude. The simulation results are consistent well with the previous experimental data.

Effect of temperature on formability of AA6063 aluminum tubes in incremental forming process was investigated. Experiments are performed on AA6063 aluminum tubes. A spirally moving tool incrementally expands the tube wall. The tube is clamped from both ends while the deformation zone is not in contact with the die. A circumferential heating system is used to heat the tube due to the low formability of aluminum alloys at ambient temperature. The effects of process parameters including temperature, radial feed, axial feed and tool linear velocity are investigated in order to obtain the highest formability and surface quality. The results show that with a temperature rise from 100°C to 300°C, the expansion ratio increases from 28% to 34%. Axial feeding and temperature are the most effective parameters on the surface roughness and bulge diameter, respectively.

In this paper, the manufacturing of a cylindrical AA6063 step tube via hot metal gas forming (HMGF) process is studied both experimentally and numerically. The goal is to investigate the effect of loading rate on the specimen profile and thickness distribution. ABAQUS finite element software is used for the numerical simulation. Experiments were carried out at 580° C in two conditions; first, without axial feeding and then with an axial feeding of 14 mm at a maximum pressure of 0. 5 MPa. The studied parameters are the pressure rate and the axial feeding rate. The results show that in the non-axial feeding mode, the thickness distribution in the die cavity region was non-uniform and a rupture occurred at a pressure of 0. 6 MPa. The reduction of the pressure rate has no significant effect on the rupture pressure. In the case of axial feeding, by choosing the pressure rate of 0. 001 MPa/s and the axial feeding rate of 0. 1 mm/s, wrinkling has been created in the specimens. However, at a pressure rate of 0. 005 MPa/s and an axial feeding rate of 0. 02 mm/s, the specimens are raptured. Under low pressure rate of 0. 001 MPa/s and low axial feeding rate of 0. 02 mm/s, the thickness in the die cavity area has decreased. A suitable die filling and thickness distribution are obtained at a pressure rate of 0. 005 MPa/s and axial feeding rate of 0. 1 mm/s.

Tube forming is a common forming process in industry. There are several methods in tube forming, whereas industries are looking for best methods with low cost and high speed. For this reason, industries need new modern forming methods. Electromagnetic forming and tube hydroforming are two modern processes which are used in manufacturing of hollow complex parts. These two processes are considered as high speed forming methods in automotive industries. In this paper, the processes of electromagnetic forming of tubes and high speed hydroforming of tubes have been investigated by numerical simulations and empirical method. Firstly, the results of numerical solutions by ABAQUS software are compared with empirical tests. At last these two forming methods have been compared in terms of displacement, stress distribution and thickness distribution. The results of deformation and thickness of the tip of the bulged tubes in empirical tests are in good agreement with the results of numerical simulations of this research. The results show that formability and bulge height in electromagnetic forming process are higher than high speed hydroforming. However, high speed hydroforming may be used in applications such as shirring fitting of parts and rings on tubes instead of electromagnetic forming.

The coupling of the electromagnetic field and the mechanical structure field is one of the main problems in the theoretical study of Electromagnetic Forming (EMF). In this study, two possible approaches for the simulation of the electromagnetic tube compression forming process were implemented and compared: A loose-coupled and a sequential-coupled algorithm. In the loose-coupled the electromagnetic field and mechanical structure field were solved separately, but in the sequential-coupled algorithm, the electromagnetic simulation and the mechanical structure simulation were iteratively performed by using Maxwell equations and Finite Difference Method (FDM) as subroutine VDLOAD in ABAQUS software. A deformation of the tube and consequently a change in inductance of tube during the process in the sequential-coupled algorithm was considered. The depth of bead in loose-coupled algorithm compared to experimental result had a 35% error, but in a sequential-coupled algorithm this error has been reduced to 5%. To predict tearing in this process Johnson-Cook damage criterion used. Increasing of discharge voltage and tube thickness respectively, had maximum effect on Johnson-Cook damage. Amount of damage less than 0.8 is conservatively suitable for the safe area without fracture.

Tube hydroforming as a new metal forming process, has attracted the attention of many industries especially automotive industry. In this study finite element simulation of tube hydroforming of a tee joint was performed with use of a commercial code ABAQUS/EXPLICIT 6.3-1 and the effects of the key parameters such as friction coefficient, strain hardening exponent and the fillet radius on parameters, protrusion height, thickness distribution and clamping force have been analyzed. Also the relation between axial feeding and axial force which is very applicable for the designer has been presented. By the use of this curve and the clamping force curve one can determine the capacity of the side jacks and the press. Then it was shown that there is a good agreement between the results of the experiment and finite element simulation. So one can use the FEM to design the process for complicated pieces and reduce the number of costly trials and errors. At the end, some important experimental facts about the velocity of the side pistons, surface finishing and counter punch position and pressure were given. Also it is shown that the coefficient of friction affects axial force more than claming force and has most dominant effect on the protrusion height and thickness distribution. As results by using the parametric studies presented in this paper a designer can gain an understanding of how each parameter affects the product.

Electromagnetic forming is a high energy rate forming process which is applied for manufacturing and assembly of many parts that are used in automobile and aerospace industries. In this process, the electromagnetic body forces (Lorentz forces) are used to produce metallic parts. In this article, the influence of important process parameters such as discharge voltage, friction coefficient, clearance between the tube and die, wall thickness and length of tube, on the radial displacement and workpiece thinning were investigated. The output of governing equations in the form of pressure applied on the part by using a subroutine in a Fortran Program. A dynamic analysis using two dimensional axisymmetric models were performed and Johnson-Cook theory was applied to represent the effect of strain rate sensitivity and show the plastic behavior in the deformation process. Finally, the numerical results were compared with the results reported by other researchers and found a good agreement between them.