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Joining by upset bulging – tooling design and new concepts for online process control using servo presses and local heating

Sviridov A., Grützner P., Rusch M., Bambach M.

Journal of Machine Engineering

2017

Vol. 17, No. 1

78--87

Conventional fusion-welding techniques pose limitations in modern multi-material assemblies due to the heat input. The negative influence of the heat-affected zone on the material properties must be avoided particularly in high-strength steels. During mechanical joining processes, which may also be used for joining of different materials e.g. steel and aluminium, high-performance joints can be produced without degradation of the material properties. Joining by upset bulging is an innovative joining method based on plastic buckling of tubes under axial compression. In previous investigations of joining by upset bulging the process parameters were determined and joints of tubes with sheet metal were tested under static and dynamic loads. The results of these studies have shown that the process of upset bulging has a large potential for the production of joints of tubes with sheets and plates. The present paper focuses on the tooling concepts for an efficient use of the technology and describes methods to control the forming and joining process. Two aspects are covered: (i) the application of servo-presses for joining by upset bulging and their possibilities for on-line process control, (ii) a moderate, process-integrated local heating of the forming area to avoid the formation of cracks and to further increase the strength of the joints.

Lateral extrusion of tailor welded aluminum alloy pipes with a lost core of low temperature melting alloy

Ohashi T., Liu G.

Journal of Achievements in Materials and Manufacturing Engineering

2009

Vol. 32, nr 1

61-65

Purpose: In this paper, the authors employ tailor welded aluminum alloy pipes for lateral extrusion process with a lost core to perform a hollow light-weight-part. Design/methodology/approach: The pipe is welded longitudinally by YAG-laser. “The lateral extrusion process with a lost core (LELC)” consists of lateral extrusion of pipes with a soluble solid core, called the “lost core”, which serves as a plastic mandrel. The process proceeds as follows. First, the pipe cavity is filled with the liquid low temperature melting material composing the lost core. The liquid is then solidified to form the soluble core of the pipe. The material is compressed longitudinally as a composite billet as well as forging, and extruded in the lateral direction. After the pipe is deformed, the lost core is melted and removed. s. The bulge by the LELC is carried out by extruding the material for the lateral direction, however the simple bulge by hydro-forming is done by internal pressure. Findings: The LELC process can make a hollow product having uneven wall thickness without the deformation concentrating on a thinner part of the material, because the circumferential deformation of the material will be performed by its meridian strain. Practical implications: The authors have developed LELC process in which the lost core consists of low-temperature melting alloys and have tried to apply the process to perform bulge process with a tailor-welded pipe having two different wall thickness. Originality/value: Optimum volume distribution is important for light-weight-parts, and employment of tailor-welded blanks is effective technique in sheet metal forming. Combination of employment of hollow shape and tailor-welded blanks seems to be hopeful.