The Greening of Diesel
By Dawn Hibbard
In one of the two research projects, Timothy Sullivan, a graduate student from Grand Blanc, is putting catalyst substrate or catalyst brick mat material through a series of tests to determine why it sometimes fails, what affects it and what characteristics it needs to have for robust performance.
The mat material is a spongy material put between the catalyst substrate and the metal casing of a catalytic converter. Under certain conditions, the metal casing can expand and cause the substrate to vibrate and break, which can result in failure of the catalytic converter. "We are looking at this material to determine its mechanical characteristics and its expansion and contraction characteristics," said Ramadan, "how do heat, moisture, mechanical stress and vibrations affect it?"
Delphi currently relies on suppliers to define this material, according to Ramadan. "They have funded this research to better understand the mat material and be able to select the right material for use in the catalytic converter," he said.
The composition of elements varies in different composite materials used for the mat material. The material is not homogeneous, but is made up of multiple substances with many different types of fibers.
Kettering has purchased a larger materials testing machine that can exert 7.5 kilo-Newtons, or 1700 pounds of force, for further testing. The larger machine adds an additional "twist" to their research capabilities because it has an upper plate that can rotate, allowing further testing variables such as shear (twisting or rotating).
Delphi and Ramadan have chosen to use testing machines with electric motors versus those that use hydraulic motors. The electric motors are better for this type of testing, according to Ramadan, because they produce less noise and vibration than hydraulic motors, and offer better control with faster and higher amplitude.
Delphi is interested in determining what basis weight of mat material works best under pressure and heat. Sullivan will use a furnace that can heat the samples to 800-900 centigrade to determine if temperature affects the material's performance and also perform testing with the top plate and the bottom plate at different temperatures. They are also going to study the effects of moisture content on the material.
Following initial testing, he and Ramadan are going to perform mathematical modeling using the test results to predict behavior under varying conditions, such as fatigue. One of the more common causes of fatigue is oscillation of load, which can cause the material to break. Ramadan and Sullivan want to identify the frequency and load that result in breakage.
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