Today’s use of private vehicles leads to too much waste. To transport a 75 kg occupant from point A to point B, we also have to consume enough energy to transport a 1500 kg vehicle. Making vehicles lighter and smaller can not only save energy and protect the environment, but can also reduce the risk of traffic injuries. This is because kinetic energy, which is proportional to mass, is a contributing factor to injuries in traffic accidents.
Future of Urban Traffic
As a supplement to public transportation, I think the urban commute is heading towards the use of small, lightweight vehicles that are powered by clean energy, individualized, connected with the traffic environment, smartly controlled, and driven automatically.
More and more advanced lightweight materials are becoming alternative and feasible materials for vehicles. These include ultra-high-strength steels, lightweight metals such as aluminum alloys and magnesium alloys, enhanced engineered plastics, and composite materials. We also see hybrid uses of these materials: for example, metal imbedded in plastic. These technologies would make vehicle structures more optimal and more energy efficient for various loads. Adhesive bonding combined with spot-welding or riveting enables the structural joining of dissimilar materials and also significantly contributes to the structural rigidity and strength.
Importance of Crash Safety
When small lightweight vehicles become the trend for the urban commute in the future, vehicle crash safety design will become increasingly challenging, although intelligent and connected vehicles and roads may improve the efficiency and safety of urban traffic. For several reasons, crash safety and lightweight vehicles are tightly connected:
- First, there will be a long transition period during which an increasing number of small lightweight vehicles will mix with many traditional-sized vehicles on the roads, so vehicles with very different masses will be used. However, a small, light vehicle is at a great disadvantage when it collides with a large, heavy vehicle.
- Second, automated or semi-automated vehicles will mix with traditional vehicles. When fully automated driving is achieved, vehicles will be moving as platoons at high speed and with a small following distance. Crash safety has to be developed so that if any incident triggers an accident, a catastrophe can be prevented.
- Third, battery-powered vehicles present new challenges in crash safety. As the battery pack is large and heavy, good protection without too much extra structure which increases the mass of the vehicle is difficult.
Crash safety research has to continue to develop technologies to characterize and model the mechanical behaviors of various advanced lightweight materials to aid in the application of new materials in vehicle structures. Engineers know how to characterize mechanical properties of traditional materials such as steel. New materials such as high strength steels and composite materials are stronger, lighter, more brittle, temperature dependent, but their material properties are more complicated. We need to continue to advance our understanding of the relevant phenomena. In addition, adhesive bonding has lots of advantages over spot welding, as it can join dissimilar materials. But its degradation behavior has to be studied before it can be used in a large scope on vehicles.
About the Author
Professor Qing Zhou, Department of Automotive Engineering at Tsinghua University in Beijing, China, is leader of the Lightweight Vehicle Thrust of the US-China Clean Vehicles Consortium, Director of the Vehicle Safety Committee of the Chinese Society of Automotive Engineers, and Associate Editor of the International Journal of Impact Engineering.
His research interests involve the structural and material failure of lightweight vehicles under impact loading, vehicle crash safety, and occupant and pedestrian impact protection.