Friction Stir Welding 

Friction Stir Welding (FSW) is a relatively new solid state welding procedure that was developed at the Welding Institute (TWI), in the UK in 1991, and that has particular advantages over traditional welding techniques.The friction stir welding plays an important role in the joining of different materials and aluminum materials to meet compelling CO2 emissions.

Benefits of Friction Stir Welding: 

  •  No additional weight on the product, no need for filler wire or shielding gas
  •  Expanded types of welds, different materials can be welded together.
  •  The material uses less heat energy, so the material is less impacted.
  •  Use thinner materials with the same joint strength
  •  Better corrosion properties
  •  Great weld appearance and minimal under/over matching
  •  Improved safety due to the absence of toxic fumes and molten splatter
  •  Low environmental impact, environmentally friendly thanks to low energy consumption

Overall, Friction Stir Welding (FSW) is a material joining technique that is a major breakthrough due to its substantial advantages compared to other techniques for welding aluminum alloys. This has allowed aircraft manufacturers such as Boeing to achieve 60% cost saving and reduce manufacturing time by 73% in aircraft models. This is only a fraction of what could be achieved. Despite its merits, FSW use is still limited due to a certain defect termed “kissing bond”. Kissing bonds reduce the stress-load resilience of FSW materials and are extremely difficult to detect or accurately size using existing NDT methods.

In addition, previous work by the consortium has shown that the fatigue life of FS welds is significantly reduced if kissing bonds exist. Specifically, it was shown that a 0.67 mm kissing bond significantly reduces fatigue life by 91% in comparison to the base metal, with the kissing bond being responsible for crack initiation. Thus, out of fear of low fatigue performance, aerospace and automotive manufacturers cannot leverage FSW to its full potential which would translate to manufacturing cost savings of €1.6 billion, fuel savings of €1.9 billion and a reduction of 2 million tons of CO2, during the next 20 years.

 

FrictionHarmonics project 

The FrictionHarmonics project will develop a novel non destructive testing inspection system in order to address the challenging problem of detecting kissing bonds in friction stir welds. Kissing bonds consist a major concern in applying friction stir welding technique (especially in the aerospace and automobile sectors). Such defects can reduce the fatigue performance of joints and are very difficult to detect (or accurately size) using existing NDT methods. This concern limits the adoption of FSWs for some critical components.

The EU-funded project Friction Harmonics, which focuses on the detection of kissing bonds in friction stir welds, was initiated to develop a non-destructive testing system to detect kissing bonds in aerostructures and automotive components. The aim is the detection of defects smaller than 0.3 mm in length.

FrictionHarmonics advantages: 

  • High automation capability
  • Flexibility & Ease In Manipulation
  • User friendly interface
  • NLUT technique
  • Reliable kissing bond detection (FrictionHarmonics is currenlty capable of detecting kissing bonds of 0.3mm in length with 100% accuracy and only 98% false-positives)
  • Ability to scan flat and curved surfaces