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This paper describes the basic principles of extensional rheometry, and the successful application to a variety of automotive fluids, including gear lubricants, paints, and forming lubricants. These fluids are used under very complex flow fields containing strong extensional (elongational) components. While exact derivation of extensional viscosities involves sophisticated theories, the measurement of liquid filament break-up time can provide fruitful information. Gear lubes showed different break-up time according to the kinematic viscosities. Addition of viscosity modifier (acrylic copolymer) significantly increased the breakup time, whereas surfactants had little effect. Clearcoat paint sample increased the breakup time, perhaps due to the deterioration. The waxy stamping lubricant showed remarkable change in the extensional properties as the temperature is raised.

The primary coating layer that inhibits salt spray induced corrosion on vehicle bodies is electrocoat. The application of electrocoat involves the electrodeposition of a polymer film on all metallic components of the vehicle body after body construction. Particularly challenging in the electrocoat process is the deposition of the coating in recessed areas of the vehicle due to material and electrical current access constraints to those regions. Currently the verification of correct electrocoat coverage requires the use of costly tear-down prototypes. A simulation tool, called EPD, has been developed that predicts the electrocoat coverage on the full vehicle body. The tool allows engineers to identify areas where there may be issues with electrocoat coverage and to see the effect of vehicle design or process modifications on coverage. A challenge in the development of any simulation tool is computational speed.