TWI is working with a consortium of several organisations to develop new strategies of manufacturing aluminium alloy pressed parts for the transport industry. Funded by Innovate UK, project LightBlank is showing how to integrate friction stir welding (FSW) with advanced stamping techniques like hot form quenching (HFQ). The main objective is to reduce the cost of producing structurally optimised pressed aluminium alloy parts for the automotive, rail and aerospace sectors.
Manufacturers are being challenged by progressively stricter carbon dioxide emission regulations and an overall demand for more efficient and lower consumption vehicles. One of the cornerstone measures to tackle climate change was announced by the EU in 2009, committing car manufacturers to cut the average carbon dioxide emissions of new models from 130g/km in 2015 to 95g/km by 2020. Even lower targets are anticipated.
One of the most immediate ways to decrease fuel consumption and emissions is to reduce the weight of the vehicle. Designers increasingly rely on numerical modelling to determine the part load-bearing topology and identify potential weight savings.
Tailor welded blank (TWB) fabrication is commonly used to shape stamped parts according to the predicted stress distribution. Tailor welded blanks are semi-finished parts typically produced by joining sheets with different thicknesses or different alloys that are subsequently formed to the final structural shape. Their use in the automotive industry has increased significantly since the 1990s as a method of minimising part weight without compromising the structural integrity and crashworthiness of the vehicle.
Aluminium alloys are often the commercially viable choice to replace formed steel parts in car body structures and reduce overall weight. However, joining aluminium alloys sheets of dissimilar grades or thicknesses to produce TWB can involve numerous challenges. Designers typically expect reduced mechanical strength in the joint and heat-affected zone when fusion welding aluminium alloys. This decrease in strength hinders the weight reduction exercise, as the components are typically manufactured thicker to compensate for any local reductions in strength caused by the welding process.