Assessment of Recently Developed Low-Force Extrusion Methods for Manufacturing Aluminium Vehicular Hydrogen Tank Liners

With increasing climate concerns and the urgent need to reduce carbon emissions, hydrogen as a clean and renewable energy source for vehicles has attracted rising interest. A major challenge is the on-board storage of flammable hydrogen gas, which restricts the commercialisation of fuel cell electric vehicles (FCEVs). This paper investigates the advantages and limitations of the existing backward extrusion techniques in producing the aluminium liners of the Type III tanks. Backward extrusion is a simple and efficient method that can manufacture near net-shape cylindrical liners in one step without the requirement of welding. However, this process requires high extrusion force, which makes the production of large tanks difficult and leads to high manufacturing cost. In the recent decades, several advanced tool designs have been proposed to reduce the extrusion force, and the merits and limitations of these designs are reviewed and analysed in this paper. Furthermore, the feasibility of these designs in processing aluminium alloys is assessed using the finite element analysis (FEA). The simulation results show that these designs are effective in reducing the extrusion load as compared to the conventional method, but the product size is restricted. Further improvements are required to make these designs suitable for producing large and long tanks for practical applications.