Industrial Need
Wider scale use of the FSSW process is currently limited by a lack of industrial knowledge and by limited independent information on the capability of the process and its key variants. This project will aim to resolve these issues by providing an impartial assessment of the capabilities of basic, swept, and refill FSSW for representative industrial applications.
The topics of interest include:
- Aside from aluminium to aluminium joints, joining of dissimilar material (Aluminium to steel, aluminium to magnesium) for light-weighting.
- FSSW tool design, performance and lifetime.
- FSSW process cycle time and weld quality.
Project Outline
Friction Stir Spot Welding (FSSW) has recently emerged as an important variant of the FSW process and an area of significant research and development interest. FSSW in its basic form essentially involves using a FSW tool to make a spot weld (i.e. no traversing motion). The process has been successfully developed and transferred into industrial production, most notably in the automotive industry (where over 1 million vehicles containing friction stir spot welds have now been produced). A key benefit reported by industrial users is a saving of around 90% in the energy required to make spot welds in aluminium in comparison to resistance spot welding.
FSSW has recently become an area of significant interest for other industry sectors, including aerospace and rail, and a broadening of the range of interest has also been noted in automotive. The process has recently been enhanced by two key variations, as follows:
- The Swept FSSW process, (pioneered by TWI) where a short traversing motion is used to increase the volume and performance of the spot weld.
- The Refill FSSW process, where a special tool system is used to produce a high quality friction stir spot weld with no exit-hole feature.
Known industrial requirements in this area include:
- Automotive: Joining of car body skins / panels to each other and to stiffening members.
- Rail: High volume attachment of skins to main structural components and panels to skins.
- Aerospace: High quality joining of stiffener ribs to skins and reinforcement panels.
This project will aim to compare the performance of conventional, swept, and refill FSSW in order to highlight to member companies the new capabilities developed and new possibilities generated in this field. This work is in line with one of the key technology strands of TWI’s FFP section, namely development of leading edge FSW capability.
Objectives
- To identify a suitable FSSW test case geometry that is representative of current and emerging industrial interest in the field.
- To conduct direct comparison trials using basic FSSW, swept FSSW and refill FSSW in the test case geometry.
- To characterise the performance of three FSSW process types and to quantify the benefits of each in comparison to the base line technology.
- To compare the FSSW process cycle time and mechanical properties against current conventional joining techniques (resistance spot joining and riveting).
Relevant Industry Sectors