Technology Applied Damping Material

Date: 20.05.21

Keeping QuietIf you thought electric cars were silent, think again. Electric drivelines are certainly quieter than internal combustion engines, but they have their own noise and vibration issues. Thankfully, new technology from Trelleborg helps ensure a smoother, quieter journey.- By Andrew Montgomery

WHEN ELECTRIC CARS WERE INVENTED,

many people thought the noisy world of the internal combustion engine would soon be history. Although electric and hybrid electric cars are quieter, it doesn’t mean they’re silent.

Electric drivelines have their own range of noise, vibration and harshness issues. And the noise of a typical combustion engine is no longer there to mask other structure-borne noises from the likes of the gearbox housing. But there’s also another culprit.

“Power inverters are one of the main contributing sources of noise in the electric vehicles’ driveline,” says Reine Axelsson, Product Manager for laminates for damping solutions within Trelleborg Sealing Solutions.

Reassuring sound of silence

This worries automotive industry Original Equipment Manufacturers(OEMs) and their component suppliers. E-Mobility is a fast-growing market, and the last thing they need is a noisy car that puts off potential consumers.

When a component supplier had a power inverter noise issue, it approached Trelleborg for help.

Trelleborg’s solution is based on the same basic technology used for brake shims. It’s called Applied Damping Material (ADM), a constrained layer damping material that consists of metal layers that have been vulcanized together with rubber to produce a strong and durable laminate. Together, the polymers, rubber and adhesive are an excellent material to absorb mechanical energy and the vibrations that radiate noise.

It works on all sorts of vibrating structures in automotive drivelines, but Trelleborg has come up with a new variant of ADM for the power inverter issue.

Secret recipe for success

“We’ve developed a completely new material for inverters because they make a wider range of noise,” says Arvid Norberg, Director of Sales and Marketing for damping solutions at Trelleborg. “By combining a different thickness of metal with different types of polymer thickness you can have a higher level of damping at a wider noise frequency and temperature.”

The exact material composition is secret. Suffice it to say, the polymers are based on nitryl butadiene rubber (NBR), and the adhesive is typically an acrylic, though other materials can also be involved.

But it’s a challenging development process because electrical engines and drives have even tougher cleanliness standards than combustion engines.

“The most critical thing is that there are no loose metallic particles past a certain size, as these can get into the engine or even the electronics and cause a short circuit,” Axelsson says. “We are asked to control the level of particles on the parts we supply.”

Norberg adds, “We’re talking about tenths of millimeters that are often invisible to the naked eye.”

Shock and future proof

With the growth of e-mobility, Norberg believes ADM has significant market potential. It underlines the decision of Trelleborg Sealing Solutions several years ago to diversify from brakes and solidify its market-leading position in damping solutions. The team working in this area is growing too.

“We are at the forefront of the market, and we see e-Mobility as being very important in the years ahead,” says Norberg.

So how will the technology develop? “We’re using more lightweight materials wherever possible,” says Axelsson. “Our focus is noise and vibration, but we are also looking to see how we can respond to other new requirements that come from our customers.

There are also new workplace directives on noise from the European Union to consider. The health and safety requirements regarding noise and vibration are only getting tougher, but that’s good for us as we’re regarded as the leading developer of brake and damping products.”

With the possibility of this technology being used in other industries, such as consumer electronics, it’s clear that ADM has enormous potential, keeping Trelleborg ahead of the competition.

About Trelleborg Damping Solutions

Headquartered in Kalmar, Sweden, Trelleborg Damping Solutions is the world leader in the manufacture and development of products to reduce brake noise and vibrations in automotive OEM and industrial applications. Alongside a program of brake shim solutions that covers all major car platforms available today, the company is also the market leader in the innovation of rubber-to-metal sandwich composites.

Apart from their excellent noise damping, these materials offer compressibility, sealing capacity, strong adhesion and vibration insulation, as well as thermal, chemical and mechanical stress resistance.

FACT

Turn off that noise!

Sound is a physical disturbance in the surrounding medium in the form of rapid pressure variation.
Noise is defined as any sound that’s perceived to be disturbing. It’s audible air pressure, where a very small vibration (in this case, from the power inverter) interacts with the surrounding air to cause a sound wave that eventually reaches the human ear. “It’s just like the speaker of a sound system,” says Reine Axelsson.
When something oscillates about a static position, it can be said to vibrate.
Constrained layer damping works by using a visco-elastic damping layer that is constrained (held down) by a metal layer.
Vibrations in the structure will cause deformation in the constrained layer.
Damping occurs due to shear deformation in the damping layer.
Mechanical energy (vibration) is transferred into a small amount of heat in the damping layer (structural damping).
Trelleborg’s Applied Damping Materials lower the vibration in the structure, reducing the ability to transmit the vibration into the air. “You’re lowering the volume of the speaker,” says Axelsson.

All Trelleborg sites