Richard L. Allor

Overview of superplastic forming research at ford motor company

In an effort to reduce vehicle weight, the automotive industry has switched to aluminum sheet for many closure panels. Although the application of aluminum is compatible with existing manufacturing processes and has attractive qualities such as low density, good mechanical properties, and high corrosion resistance, it has less room-temperature formability than steel. The expanded forming limits that are possible with superplastic forming can significantly improve the ability to manufacture complex shapes from materials with limited formability. Aluminum closure panels produced by superplastic forming have been used by Ford Motor Company for over a decade. However, applications have been limited to low-volume, specialty vehicles due to the relatively slow cycle time and the cost penalty associated with the specially processed sheet alloys. While there has been substantial research on the superplastic characteristics of aluminum alloys, the bulk of this work has focused on the development of aerospace alloys, which are often too costly and perhaps inappropriate for automotive applications. Additionally, there has been a limited amount of work done to develop the technologies required to support the higher production volumes of the automotive industry. This work presents an automotive perspective on superplastic forming and an overview of the research being performed at Ford Motor Company to increase the production volume so superplastic forming can be cost competitive with more traditional forming technologies.

Effects of Composition and Surface Finish of Silicon Nitride Tappet Inserts on Valvetrain Friction

Abstract In order to build more fuel efficient engines, new materials and lubricant formulations are being sought to reduce frictional losses. The valvetrain contributes about 6-10% of the total frictional losses in an engine. To reduce valvetrain frictional losses, polished silicon nitride tappet inserts were evaluated for their friction reduction potential. Silicon nitrides obtained from three sources were polished using three different processes: the suppliers conventional diamond polishing technique and two non-diamond polishing techniques-“Ford Finish” and chemo-mechanical polishing. The valvetrain friction torque was measured in a laboratory apparatus using a single cam lobe rotating against a direct acting mechanical bucket tappet with production engine hardware. The friction torque values obtained with surfaces prepared by all three processes differed significantly although their initial centerline average surface roughnesses were similar. All three silicon nitride surfaces prepared by “Ford Finish” showed lower friction torque than the production steel surface when an engine oil containing no friction modifier was used. With a low friction oil containing a friction reducing additive, friction torque values were significantly lower and polished silicon nitride surfaces did not offer additional friction reduction benefit relative to the production steel surface. A simple calculation showed a maximum of about 0.5 % fuel economy benefit can be gained due to polishing with the engine oil without friction modifier but very little, if any, with low friction oil. However, silicon nitride inserts may be useful for weight reduction and increased durability.

Imaging pyrometer for monitoring the surface temperature of a spray-formed steel billet

A two-wavelength, imaging pyrometer was developed for real- time measurement of the surface temperature distribution of a spray-formed steel billet. This new spray-forming process is used to deposit bulk steel on a ceramic substrate in a surface temperature range of 300 degrees C to 400 degrees C, using four, twin-wire arc plasma torches. These steel billets are used as tools in metal forming processes, injection molding and die casting tools, and other processes that may need hard tooling, such as the automotive industry. The steel billet must be formed with a uniform, surface temperature distribution to minimize the thermal stresses within the steel, throughout the process. The imaging pyrometer uses a near-IR InGaAs CCD camera with high quantum efficiency from 0.95 to 1.75 microns. The wavelengths of 1.40 and 1.65 microns were selected to sense the low temperature billet. The camera has a format of 320 x 240 pixels with a pixel spacing of 30 microns and an integral 12-bit A/D converter with both video and digital outputs. The design of the pyrometer provides a working distance of 2.2 meters and a field of view of 0.6 meters. This technical paper describes the calibrations and initial measurement results obtained in a spray forming facility at the Ford Research Laboratory. The calibration provided intensity ratio measurements for surface temperatures ranging from 200 degrees C to 300 degrees C, the expected range of operation. The initial measurements described here depict the surface temperature distribution of the steel billet throughout the spray forming process, typically lasting several hours.