TY - GEN

T1 - Process Optimization of Joining by Upset Bulging with Local Heating

AU - Rusch, Michael

AU - Almohallami, Amer

AU - Sviridov, Alexander

AU - Bonk, Christian

AU - Behrens, Bernd Arno

AU - Bambach, Markus

N1 - Funding information: 17639BG was financed and supervised by the European Research Association for Sheet Metal Working (EFB). In the scope of the program to promote Industrial Collective Research it was funded by the German Federation of Industrial Research Associations (AiF) with means of the Federal Ministry of Economic Affairs and Energy (BMWi) on basis of a decision by the German Bundestag.

PY - 2017/10/16

Y1 - 2017/10/16

N2 - Joining by upset bulging is a mechanical joining method where axial load is applied to a tube to form two revolving bulges, which clamp the parts to be joined and create a force and form fit. It can be used to join tubes with other structures such as sheets, plates, tubes or profiles of the same or different materials. Other processes such as welding are often limited in joining multi-material assemblies or high-strength materials. With joining by upset bulging at room temperature, the main drawback is the possible initiation of damage (cracks) in the inner buckling zone because of high local stresses and strains. In this paper, a method to avoid the formation of cracks is introduced. Before forming the bulge the tube is locally heated by an induction coil. For the construction steel (E235+N) a maximum temperature of 700 °C was used to avoid phase transformation. For the numerical study of the process the mechanical properties of the tube material were examined at different temperatures and strain rates to determine its flow curves. A parametrical FE model was developed to simulate the bulging process with local heating. Experiments with local heating were executed and metallographic studies of the bulging area were conducted. While specimens heated to 500 °C showed small cracks left, damage-free flanges could be created at 600 and 700 °C. Static testing of damage-free bulges showed improvements in tensile strength and torsion strength compared to bulges formed at room-temperature, while bending and compression behavior remained nearly unchanged. In cyclic testing the locally heated specimens underwent about 3.7 times as many cycles before failure as the specimens formed at room temperature.

AB - Joining by upset bulging is a mechanical joining method where axial load is applied to a tube to form two revolving bulges, which clamp the parts to be joined and create a force and form fit. It can be used to join tubes with other structures such as sheets, plates, tubes or profiles of the same or different materials. Other processes such as welding are often limited in joining multi-material assemblies or high-strength materials. With joining by upset bulging at room temperature, the main drawback is the possible initiation of damage (cracks) in the inner buckling zone because of high local stresses and strains. In this paper, a method to avoid the formation of cracks is introduced. Before forming the bulge the tube is locally heated by an induction coil. For the construction steel (E235+N) a maximum temperature of 700 °C was used to avoid phase transformation. For the numerical study of the process the mechanical properties of the tube material were examined at different temperatures and strain rates to determine its flow curves. A parametrical FE model was developed to simulate the bulging process with local heating. Experiments with local heating were executed and metallographic studies of the bulging area were conducted. While specimens heated to 500 °C showed small cracks left, damage-free flanges could be created at 600 and 700 °C. Static testing of damage-free bulges showed improvements in tensile strength and torsion strength compared to bulges formed at room-temperature, while bending and compression behavior remained nearly unchanged. In cyclic testing the locally heated specimens underwent about 3.7 times as many cycles before failure as the specimens formed at room temperature.

UR - http://www.scopus.com/inward/record.url?scp=85037700228&partnerID=8YFLogxK

U2 - 10.1063/1.5008137

DO - 10.1063/1.5008137

M3 - Conference contribution

AN - SCOPUS:85037700228

T3 - AIP Conference Proceedings

BT - Proceedings of the 20th International ESAFORM Conference on Material Forming, ESAFORM 2017

A2 - Brabazon, Dermot

A2 - Ul Ahad, Inam

A2 - Naher, Sumsun

T2 - 20th International ESAFORM Conference on Material Forming, ESAFORM 2017

Y2 - 26 April 2017 through 28 April 2017

ER -