1998-02-23

Use of Powdered Metal for a Valve Bridge in a 4-Valve Heavy Duty Diesel Engine 980330

A new 12.5 L four-valve heavy duty diesel engine has demonstrated that Powdered Metal (PM) is an effective material alternative to wrought steel for the valve bridge. The valve bridge, an element that spans the pair of intake or exhaust valves, allows a single rocker arm to actuate the pair of valves. The component is subjected to a high number of cycles at a moderately high load and geometry precision is essential for desirable wear characteristics. The PM material selected, MPIF FL4605-120HT, has replaced 8620 steel after making component geometry changes. The PM part has a higher load capacity than the original design with equivalent wear characteristics and offers a 80% cost saving over the original design.
This paper presents the geometry changes defined by FEA analysis and component testing performed to verify the change from wrought steel to PM. A required characteristic of this component is moderately high fatigue strength. It also needs to have good wear resistance since slight increases in wear can have a significant negative effect on engine performance and engine life. The summarized testing demonstrated the appropriateness of PM to meet these requirements for this component.

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