In tube hydroforming process, due to friction condition, uniform wall thickness, as well as sharp corners may not be achieved. Use of ultrasonic vibration can improve the contact conditions at the tube-die interface. The current work studies the effect of applying ultrasonic vibration on wall thickness and corner filling of hydroformed tubes. Firstly, a numerical model based on geometric relationships and stress-strain state has been established by which wall thickness and corner radius of hydroformed tubes can be obtained. In this model, the ultrasonic vibrations affect the non linear friction conditions at the tube-die interface. By comparing the FEM models of tubes in two cases of with vibration and without vibration, it is possible to investigate the effects of vibration on wall thickness and corner filling. The results indicate superimposing ultrasonic vibrations to the process will increase corner filling ratio of the tube significantly, and more uniform tube wall thickness will be achieved.

This paper aims to establish a basic understanding of double bulge tube hydroforming process of stainless steel deep drawn cups. The method is briefly reviewed by carrying outexperimental tests and Finite element analysis. After measuring bulge height in both formed curves by CMM and thickness variation of formed tube by ultrasonic thickness measurement unit, it’s found out that thickness variation in this process is less that other traditional methods such as traditional spinning and rubber pad forming. A finite element model is constructed to simulate the double bulge tube hydroforming process and asses the influence of friction coefficient and tube material properties. It is found that material hardening coefficient had the most significant influence on formability characteristics during double bulge tube hydroforming. As similar as other tube hydroforming processes, increasing friction decrease bulge height and thickness.

Considering a kinematical velocity admissible field, the upper bound method has been used for predicting the amount of pressure in hydroforming of sheet metals. The effects of work hardening, friction and blank size have been considered in pressure prediction. Also the effect of sheet thickness variation has been considered in the present work formulations. The relation between pressure and punch stroke has been obtained and optimized by changing the selective parameters in the velocity components. The results for cylindrical and hemispheric parts have been obtained and compared with the published experimental results. The effects of work hardening, friction and blank size on hydroforming pressure have been examined on an elliptical part. Good agreement was found between the experimental and numerical results.

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.

Hydroforming process in one of the most effective production method, for improving the drawing ratio in sheet metal forming process. This is due to the fact that in hydroforming process, forming takes place using a punch which drives the part forward via a controlled fluid pressure. In this paper, deep drawing hydroforming for circular punch is investigated. Different pressure paths are tested using ABAQUS 6.7 software, in order to determine practical pressure constraint via simulation. Finally, drawing ratio effect on practical pressure constraint is investigated. In order to evaluate simulation accuracy, the obtained results are compared with some experimental results. Results indicate that by increasing drawing ratio, rupture curve is dropped significantly, and allowed zone area is reduced. Moreover, with increasing time, allowed zone area is expanded, and with increasing drawing ratio, allowed zone distance is reduced.