Madison Heights, Michigan – Differing thermal expansion properties of multi-metal components has long been a sore spot for motor vehicle manufacturers. When automakers began using aluminum engine blocks with cast-iron heads in the 1970s, engines leaked oil and blew seals because the iron and aluminum expanded at different rates.
Adhesives and surface-treatment provider Henkel and researchers at Clemson University’s International Center for Automotive Research (CU-ICAR) in Greenville, South Carolina, have developed new techniques to measure thermal expansion of dissimilar materials, addressing a major concern that continues to grow as companies replace steel panels with lighter-weight materials.
“When one substrate grows faster than another during heating, potential issues can arise, including distortion, adhesive stress, and potential de-bonding of adhesive joints,” said Michael Flener, Innovation Program Manager, Transportation and Metals Industries, Henkel. “By using these experimental methods in conjunction with our predictive models, OEM’s can better determine the ideal location and types of joining areas needed during the vehicle design and development process.”
Henkel and CU-ICAR researchers developed systems using non-contact optical measurement systems, customized to read cold and high temperatures through thick glass windows used in industrial ovens (often used in paint shops) and environmental test chambers. Researchers validated test results by measuring coupon-level samples, sub-assemblies, and full-scale vehicles after heat treatment and comparing those real-world measurements to the more-theoretical results gained from the optical sensors.
“The experimental methods we’ve developed with Henkel, along with the predictive model Henkel already established, open up new opportunities for the vehicle manufacturing community, including the ability to measure changes in full-sized vehicles instead of just coupon-size samples,” said Fadi Abu-Farha, assistant professor, Automotive Engineering, CU-ICAR. “These methods can measure full-field thermal expansion within one-tenth of a millimeter of accuracy – resulting in data that provide highly accurate understanding of how substrates and adhesives are interacting within automotive thermal cycles.”
Abu-Farha will present results of CU-ICAR’s research with Henkel during the upcoming SAE World Congress, April 5, 2017, at Cobo Center in Detroit.