A5

Working Group A | Metallurgical joint

 
 
a5_spp1640

Investigation of the formation mechanisms of the bonding zone in collision welding

Prof. Dr.-Ing. Dipl.-Wirtsch.-Ing. Peter Groche, TU Darmstadt

 
 

Abstract:

A high speed impact under accurately defined conditions allows for the achievement of a metallurgical joint. Here, almost no thermal energy is introduced and, besides, not needed. Thus, this principle even allows for the joining of dissimilar metals such as aluminum, steel, copper and many more. The very low introduction of thermal energy by the plastic deformation during the impact is the reason why no negative influence on the grain structure occurs. In the industrial application, two processes exist that base on this mechanism: explosion welding and electromagnetic pulse welding.

Despite the great advantages of the process, especially when it comes to dissimilar metals, it is still not widely spread. The main cause is the great lack of knowledge concerning the underlying mechanisms, which is the reason why the design of a joint is still performed largely empirically.

Thus, the aim of this research project is to identify the governing mechanisms as well as their influencing factors. In the third phase, the focus is especially on the predictability of the process. The works comprise three main tasks:

 
 
Mechanischer Aufbau Versuchsstand
Mechanical setup of the test rig

Experimental works are performed with a special test rig, which is capable of reaching the necessary impact speeds for a successful joint beginning at about 250m/s completely mechanically. One sample is attached to one end of each of the two rotors, respectively. They rotate in the same direction, whereby the samples collide in the centre with twice the velocity. During the project, this test rig will be continuously developed concerning robustness, accuracy and velocity. At 5000U/min for both rotors, the angular deviation at the moment of impact is less than 0,1°. The impact is captured with a special camera and the images are analyzed.

Hochgeschwindigkeitsaufnahme vom Aufprall
High speed images of the impact
 
 
REM Aufnahme der Fügezone
SEM images of the joint area

The joined samples are then investigated metallographically. The experiments are performed with different metals, alloys and heat treatment conditions as well as superficial treatments. Comparing the test rig's results to electromagnetic pulse welding as industrial process, it could be shown that the joint area exhibits almost identical properties.

 

Not nearly all process characteristics are accessible for measurements during the impact, which makes the numerical simulation particularly important. The material model and the contact definition are of great importance. With the help of the numerical simulation it was possible to show the transient behavior of electromagnetic pulse welding and compare it to the stationary impact process in the test rig.

Numerical simulation of the test rig
Numerical simulation of the test rig
numerical simulation of electromagnetic pulse welding
Numerical simulation of electromagnetic pulse welding
 

The project is realized in collaboration with two further projects of the SPP:

A close cooperation exists with the Institute of Materials Science and Engineering of the TU Chemnitz (IWW, project A8), concerning the material examination with a great focus on strain rate effects and characteristics of the joint area.

At the Department for Cutting and Joining of the University of Kassel (tff, project A9), electromagnetic pulse welding is investigated. Results of these works are compared to the results of the test rig at the PtU.

 
 

Publications:

2019   
  Process boundaries of collision welding at low energies Groche, P.; Niessen, B.; Pabst, C.
In: Material Science and Engineering Technology, 2019 (accepted)
  Weld Interface Characteristics of Copper in Collision Welding Niessen, B.; Groche, P.
In: Proceedings ESAFORM 2019, Vitoria-Gasteiz, Spanien, 8.-10.05. 2019 (accepted)
  Hochgeschwindigkeitsfügen bei niedrigen Energien Niessen, B; Gerlitzky, C.; Groche, P.
In: Blechnet, 1, pp. 54-55, 2019
2018   
  Investigations on Shock Waves during Collision Welding Niessen, B.; Siegel M.; Groche P.
In: 8th International Conference on High Speed Forming,
Columbus, Ohio
  Proofs and Contradictions for Wave Formation Theories in Collision Welding Niessen, B., Franceschi, A., & Groche, P.
In: Key Engineering Materials, 767, pp. 447–455
  Identification of Process Parameters in Electromagnetic Pulse Welding and Their Utilisation to Expand the Process Window Pabst, C.; Groche, P.
In: International Journal of Materials, Mechanics and Manufacturing, 6 (1)
2017   
  Process window acquisition for impact welding processes Groche, P.; Becker, M.; Pabst, C.
In: Materials & Design, 118, 286–293
2016   
  The influence of thermal and mechanical effects on the bond formation during impact welding Pabst, C.; Groche, P.
In: 7th International Conference on High Speed Forming, Dortmund
  Microstructural characterization of magnetic pulse welded aluminum/aluminum and aluminum/steel joints Sharafiev, S; Wagner, M.F.-X.; Pabst, C.; Groche, P.
In: 18. Werkstofftechnisches Kolloquium, Chemnitz
2015   
  Numerical Simulation of Impact Welding Processes with LS-DYNA Pabst, C.; Groche, P.
In: 10th European LS-DYNA Conference, Würzburg
2014   
  Development of a novel test rig to investigate the fundamentals of impact welding Groche, P.; Wagner, M. F.-X.; Pabst, C.; Sharafiev, S.
In: Journal of Materials Processing Technology, 214 (214) pp. 1972–1994
  Electromagnetic Pulse Welding: Process Insights by High Speed Imaging and Numerical Simulation Pabst, C.; Groche, P.
In: 6th International Conference on High Speed Forming, Daejeon
  A novel method to investigate the principles of impact welding: Development and enhancement of a test rig, experimental and numerical results Pabst, C.; Sharafiev, S.; Groche, P.; Wagner, M. F.-X.
In: Advanced Materials Research, 966–967 pp. 500–509
 
 

back to working groups