Lightweighting is a process of replacing a material with another to reduce weight while maintaining performance. Automotive reduces weight to improve fuel efficiency primarily since the payload itself is fairly constant. Aerospace uses lightweigting to increase payload and range. In that respect, the advantage of lightweighting for heavy manufacturing is closer to that for the aerospace industry: increase useful payload and range.
The efficiency increase and savings are real. Faster, more efficient work is good for the contractor and also for the customer. For every hundred pounds in weight reduction, another hundred pounds can be pulled or pushed every time there is a pull or a push.
Materials substitutions are often based on weight saved for equivalent stiffness. Replacing steel with a composite gives equivalent stiffness with 25-30% weight savings. The same holds true for replacing aluminum with composite. Replacing steel with higher strength steel gives more modest weight savings but has the advantage of not introducing a different material family.
Examples of areas where lightweighting can impact overall efficiency are:
- Earth moving equipment – crew compartment, fenders and skirts, radiator shell, equipment housings, battery boxes.
- Cranes – tower, booms, crew compartment. This results in easier and faster assembly on site. The tower sees mostly compressive load while the boom sees bending moment. Every lift can carry a higher payload, resulting in less time on site and faster completion.
- Marine – replacement of superstructure with composite reduces topside load and center of gravity. It offers better corrosion resistance and less maintenance.
- Heavy duty truck – the advantages of composites in HD trucking are legendary. Most of the industry has converted to composite cabs. Newer bonding techniques enable joining to aluminum or steel sub-components.
- Trailer – aluminum and composites can replace steels and are making inroads.
What technologies apply?
Working with materials substitutions invariably requires working with materials joining technologies. Starting with modeling, engineered joint designs and predicted performance are needed for combinations of metals, composites, and thermoplastics. In bonded structure, it is possible to implement aluminum-composite, steel-composite, and even titanium-composite combinations as well as composite-composite bonding. Advanced reinforced thermoplastic welding is also an option.
On the metals side, newer approaches include friction stir welding (FSW) of steels, thick-section aluminum, and titanium. Upgraded welding techniques are needed for the newer high strength steels to provide minimum HAZ strength effects. Distortion control is important for welding of thick-section steels. Coupled with nondestructive evaluation (NDE), testing, and fatigue life testing capabilities, it is possible to provide a complete engineering package to enable the transition in to 21st century structure.
I’m George Ritter, Principal Engineer in EWI’s Materials and Structural Integrity group. Contact me at firstname.lastname@example.org or 614.688.5199 if you have any questions. Or post a comment below.