Joining and Forming by Plastic Deformation

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      Work area

      The focus of the research in joining by deformation is on questions relating to the joining of lightweight construction materials, such as fibre reinforced plastics or wrought aluminium alloys both as joints using purely deformation and in combination with adhesive bonding. The main fields of application for the joining methods in question are within the mobility sector (aircraft, rail and automotive industries).

      © Fraunhofer IGP

      The research covers both the initial qualification of the deformation or setting process of the joint and the analysis of the load-bearing capacity of the joint under static and cyclic loading and in the event of a crash. A particular focus here is on the fracture-mechanical evaluation of the joints with respect to crack initiation, crack propagation and fracture behaviour. Furthermore, the properties of the joints are analysed over the service life, and topics such as corrosion resistance, leak tightness, electrical conductivity or the possibilities of (non-destructive) testing (NDT) are examined.

       

      The focus of the research into forming by plastic deformation centres on fundamental questions of forming and deformation of component structures. The main emphasis here is on the development of prediction models and the derivation of process control concepts for cold and hot plastic forming, predominantly for the forming of large steel plates with material thicknesses of more than 5 mm. These have to be evaluated and optimised with respect to their real-time capability for integration into machine control systems.

      Project overview

      Crack Initiation

      At what point does the clinch joint break?

      FRICTION-BASED CRACK INITIATION

      Due to their efficiency, deformation joining processes requiring no pre-holing are increasingly used in the mobility sector. The focus is on processes that do not require the use of an auxiliary joining part, such as clinching. There is currently an acceptance problem in the field of aircraft construction, due in part to a lack of knowledge on the failure-behaviour of clinch-bonded connections under cyclic loading. The aim of the research project is therefore the in-depth analysis of crack initiation on deformation joined clinch-bonded connections and the prediction of the location and crack-related service life of these connections. A central task is to demonstrate the impact of friction-based crack initiation on the failure behaviour of clinch connections.

      Services

      • Application-specific development and optimisation of deformation joining processes of lightweight construction materials
      • Process integration of joining by deformation through joint sampling, innovative setting device concepts and ergonomic workplace design
      • Establishment of quality assurance procedures, for example by monitoring the setting process or by NDT methods
      • Material and joining testing under mechanical load (static, cyclic, mechanical cracking)
      • Transformation of heavy plates and development of simplified
      • predictive models for technical control integration
      • Development of self-learning systems for joining and forming by plastic deformation processes (AI)
      • Process simulation during joining and forming by means of numerical FEM (ANSYS, LS-Dyna, etc.)
      • Analysis methods for sensitivity and damage analysis during joining and forming (material and metallography)

      Equipment

      Test laboratory

      • Static universal testing machines (up to 1000 kN)
      • Dynamic pulsators (0.1...100 kN; 0.1...100 Hz)
      • Torque test bench up to 500 Nm
      • Corrosion test chambers/UV irradiation facilities
      • Climate chambers for samples and component tests (90 m³, -50...60 °C)

      Production Engineering

      • NC workshop for sample preparation and fixture construction
      • Test stand for conventional and ultrasonic-supported clinching up to max. 50 kN
      • Test stand for solid and semi-tubular self-pierce riveting
      • Process monitoring for setting processes (force / travel torque / angle of rotation)

      Analytics laboratory

      • Incident and transmitted light microscopes
      • Spark Emission Spectrometry
      • Helium leak tester
      • Hardness tester

      Software used

      • Catia V5
      • LS-Dyna
      • ABAQUS (Forschungslizenz)
      • Ansys Workbench V12