INTERMET STUDY REVEALS THE ADVANTAGES OF CAST DUCTILE IRON CRANKSHAFTS

Significant Cost and Weight Savings with Positive NVH Characteristics

TROY, MICHIGAN, March 4, 1999 - Intermet Corporation (NSADAQ: INMT) will present a paper today to the Society of Automotive Engineers that demonstrates the lower-cost, weight-saving, and positive NVH (noise, vibration and harshness) characteristic advantages of utilizing cast ductile iron crankshafts in an aluminum block, V-6 engine.

The results of the joint study conducted by Intermet Corporation, Ricardo Inc. and Simpson Industries Inc., found that the NVH characteristics of a modern, aluminum block, V-6 engine were as good or better when a cast ductile iron crankshaft with a multi-mode damper was substituted for the production, forged steel crankshaft with conventional, single torsional mode damper.

Dr. Alan P. Druschitz, Intermet corporate director of materials development, says that the recent trend in automotive crankshaft design to replace cast ductile iron with forged steel has often been based on an anticipated NVH benefit brought on by the higher elastic modulus (stiffness) of steel. However, not only do cast ductile iron crankshafts weigh and cost less due to their lower material, production and machining costs, they also produce comparable NVH performance to steel forged crankshafts when certain key system elements are addressed.

Much of the long-standing perception that steel components perform better than those cast in ductile iron has to do with the belief that there will be greater torsional and bending vibrations in the iron component. Druschitz says, though, that this claim ignores the effects of rotating mass and vibration dampers. "To begin with, a cast ductile iron crankshaft can be cast with hollow pins, mains and counterweights, which allow further reductions in rotating mass.

Torsional vibration dampers are commonly used to reduce the effect of critical vibrations by absorbing and dissipating torsional vibration energy. However, dampers can also be designed to reduce bending vibrations.

Druschitz says, that none of the previous studies in this area took into account the significant effect dampers can have on NVH characteristics. The Intermet study, for the first time, included suitably designed dampers for each crankshaft as part of its comparison.

Results of the new study concluded:

• Sound pressure measurements for an engine with a cast ductile iron crankshaft with a multimode damper tuned to torsional frequencies of 209 and 309 Hz produced similar noise levels over an rpm range of 1000-6500 compared to the same engine with production, forged steel crankshaft and a single torsional mode damper.
• Bedplate acceleration measurements using the cast ductile iron crankshaft also produced very similar or even slightly lower accelerations over a rpm range of 1000-6500 compared to the production part.
• And, engine mount acceleration measurements produced similar results over the same rpm range.

Druschitz presented his findings on the influence of crankshaft material and design on the NVH characteristics of a modern aluminum block, V-6 engine at this week's 1999 Society of Automotive Engineers Expo at Cobo Conference and Exposition Center in Detroit, Michigan.  The presentation was one of two given this year by Intermet at the annual SAE event.

With headquarters in Troy, Michigan, Intermet Corporation and its subsidiaries design and manufacture precision iron and aluminum cast components for automotive and industrial equipment manufacturers worldwide.  Intermet also produces precision-machined components and manufactures cranes and specialty service vehicles.  The company has more than 6,900 employees at 19 operating locations in North America and Europe.  The company's internet address is www.intermet.com.

Ductile Home   •   Officers & Directors   •   Back Issues   •   Contact Us   •   Legal