5/26/21
Exterior noise of a high-speed train
Transport by high-speed train is becoming more widespread particularly in these climate-conscious times. How can the external noise from these moving sources be efficiently measured and assessed?
May 26, 2020 AUTOMOTIVE
Located in Canton, Michigan, Material Sciences Corporation (MSC) is a materials supplier and engineering services provider, primarily working on innovative solutions for lightweighting, acoustics and coated-metals solutions. They offer products and services for a wide range of industries and markets – from automotive to appliances.
A Ford GT, the sleek supercar successor to the 60s GT40 Le Mans champ, comes to a stop at a light, the driver and passers-by listen to the low, pleasantly menacing rumble of the engine. Not long after, a Ford Galaxy van pulls up next to the GT, and while waiting for the lights to change, the parents remind the kids, for the forty-second time, that if they don’t settle down they will turn right around and go home. These two vehicles are at opposite ends of the vehicular spectrum, but they have more in common than just having four wheels. In both cases, while stopping for the light, all the sounds heard were exactly the sounds intended to be heard: the carefully engineered growl of the GT and the back-and-forth conversation of the parents and children.
What they didn’t hear was the equally well-engineered silence of the brakes. Brakes are a vital component in vehicles, but they are not something people want to notice. Brakes are just supposed to work, quietly and effectively: rain, sleet, snow, blazing heat or freezing cold – they must make the car stop without one tiny squeak.
MSCs climate-controlled semi-anechoic test chamber can transform a comfortable room temperature into a humid –15 °C, then with a series of hard stops jack up the brake temperature to 300 °C – in under 24 hours
MSC works with original equipment manufacturers (OEMs) like Ford to make sure that the materials used to make the brakes can meet the requirements of the target market group (be it the durability demanded by transport vans and family wagons or the stopping power required to reign in the mass of a heavy-duty work truck) without contributing one single decibel to the overall cabin noise.
Motor vehicles are used privately and commercially in just about any environment imaginable, and the stresses placed on material components can differ drastically depending on the environmental conditions. Driving or, more to the point here, braking hard or gently at +45 to –45 °C with zero to 100% humidity affects the brake components in drastically different ways, and the components need to be tested across those environmental spectra.
Ford has been in the industry for a very long time. And because they keep track of the weather conditions and locations where brake noise issues have been reported, they have a good idea of where potential problems can creep in. These locales are not environmentally placid and stable climates, but places where temperature and humidity can reach extremes or change rapidly and drastically. They are also not environments that are readily available or convenient for testing outside, and they’re difficult, if not near impossible for most test houses to simulate.
The MSC test facility is not one of those places. They test on a four-wheel chassis dynamometer in a climate-controlled (temperature and humidity) semi-anechoic test environment that can – in under 24 hours – transform a comfortable room temperature into a humid –15 °C, then with a series of hard stops jack up the brake temperature to 300 °C. And those tests can last up to two days – running non-stop. In these extreme environments, the measurement equipment used must not just be able to survive the environmental changes, but be able to continue to provide accurate, reliable data throughout the process. To meet their needs, MSC uses a combination of a LINK dynamometer with HBK’s PULSE™ LabShop software and LAN-XI data acquisition module, simultaneously measuring all four wheels with five to six channels.
The sequence of events that make up the testing process is often the same, whether it is a new brake system or an existing one. The vehicle to test is secured on the chassis dynamometer, then it is cycled across a range of speeds and brake conditions all under the various environmental conditions specified by Ford engineers. Ford also provides prototype and real-world data that is needed for correlation with chamber and environment simulation. From this point, it becomes an iterative process that requires close collaboration between MSC and Ford.
At any given time, MSC may have two to three vehicles in various stages of testing, running the gamut of its environmental and performance parameters. This cycle through extremes generates a mass of data that is then provided to Ford, who makes adjustments based on that data. The close working relationship is important because the vehicle might be back the next day with a new set of test parameters. And this cycle of exchange and test continues until that ideal quiet brake is achieved.
In the end, everyone benefits when things work as they should. The end user enjoys coming safely to a nice quiet stop without ever having to think about what is going on between the brake pad and disc. And MSC and Ford benefit from the results of having satisfied their respective customers. The return on investment for accurate, quality data and the determination to maintain stringent testing standards is well worth the price.
Based in Dearborn, Michigan, Ford Motor Company designs, manufactures, markets and services a full line of cars, trucks, SUVs, and electrified vehicles, and they are in a constant process of improving and refining their entire line and developing new vehicles. This means they are constantly working with new materials and designs that must adhere to their strict standards for functionality and noise.
Transport by high-speed train is becoming more widespread particularly in these climate-conscious times. How can the external noise from these moving sources be efficiently measured and assessed?
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