Much of Ramin Younessi's work deals with extremes, such as searing heat and bitter cold, and how they affect trucks and components. It's work that takes place largely behind the scenes. But it's work that makes sure new designs are ready for whatever the world throws their way.
“We break testing down into two categories: components and vehicles,” explains Younessi, chief test engineer for Freightliner LLC. Components undergo electrical and mechanical test to validate durability, compatibility with other parts, and compliance with safety standards. Vehicles are subjected to lab and field tests, as well as testing by fleet customers.
Some tests are routine, such as making sure all components meet or exceed SAE standards and government regulations. But a number of more unusual procedures are also used to make sure vehicles can withstand a variety of service conditions.
Electromagnetic testing is a good example. “We put a truck up on a dynamometer, get it up to highway speed, and then bombard it with different levels of radio and electrical waves, similar to what it would experience if it was driven near a radio station or high-power electrical line,” says Younessi. “We do that to make sure those electromagnetic waves don't interfere with the truck's engine control module (ECM), antilock braking system or any other computer-controlled component.”
First, however, components are tested individually. “For example, we put frame rails and other structural pieces on a static bed plate and apply huge loads — sometimes in excess of 100,000 lb. — to see how they perform,” explains Younessi. We do this to make sure components can hold up on their own before they are integrated into the vehicle.”
Flexural testing, which measures the amount of structural fatigue components can withstand, is also used‥ “We apply and remove loads repeatedly until the structure fails, specifically to see if it fails at the targets we've set.”
Once the vehicle is assembled, Younessi and his engineers conduct what he calls “shake, bake, and marinate” tests, exposing the truck to extreme vibration, temperature, and moisture conditions to see how it holds up. “We simulate conditions where a truck is driving down a bumpy road, vibrating all over the place, with the engine running hot,” he says. “Then it will ‘hit’ a pothole that sprays cold water onto the engine. We want to know what happens next.”
Freightliner's cab shaker can handle GVWs up to 68,000 lb. Tests are designed to simulate 500,000 miles of road vibration in a month or two, enabling engineers to track life cycle effects on the cab, engine, and transmission.
To find out how different chemicals affect painted surfaces, rubber hoses, etc., trucks are sprayed with caustic salt mixtures and immersed in vats of oil and ethylene glycol. which mimics the road debris kicked up underneath the vehicle.
After lab tests are completed, trucks are ready for road tests. They may be taken to northern Minnesota in the middle of January, for example, to check starting capability and transmission shifting in super-cold conditions, as well as whether or not cabs warm up within 30 min. Similar testing takes place in hot weather locales. Gearboxes are put to the test on mountain roads with 10% grades.
The final stage of testing — customer field tests — is the most important. “When we give a new truck, or one equipped with a new component, to a customer, we find out how it really gets used — and we learn something every time,” Younessi points out. For example, field tests demonstrated that drivers placed things like coins and rings on the dashboard that then fell down the HVAC vents and into the engine. As a result, Freightliner made sure HVAC vent openings are small enough so these kind of items won't fall in, yet big enough to allow air to pass through without excessive noise.
“The customer has to drive that truck in the real world, so we use all this testing to make sure vehicles are ready for just about anything,” he says. “We take new technology and put it in the truck to see how it performs. For me, that process is a lot of fun.”
Name: Ramin Younessi, general manager/chief test engineer, Freightliner LLC.
Background: B.S. in Electrical Engineering, Rochester Institute of Technology; M.S. in EE, Syracuse Univ.; M.S. in Engineering Management, Univ. of Maryland.
Work Experience: Joined Freightliner in '94 as project engineer. Promoted to manager-engineering operation & planning in '98. Appointed director-strategic product planning & production for DaimlerChrysler's commercial vehicle division., Returned to Freightliner as general manager-chief testing engineer in December '02.