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Capturing Pin-Ejection in Drop-Tower Tests of Digger Tooth Systems
This simulation provided the first true glimpse of the completely transient impact behavior of digger-tooth system.  The point (the digging part) is attached to the nose (interior supporting part) by deceptively simple arrangement of steel and rubber pins. The interaction of these pins creates the locking mechnism between the point and the nose. When working as designed - the point or tooth stays "locked" in place during the digging operation (think gigantic buckets and digging systems. When this locking pin ejects the tooth is lost and can cause a bit of a disruption when this massive steel part is ingested by downstream ore processing equipment. The goal of this work was then to learn more about how this pin can eject and use these results to drive the design process toward better locking mechanisms.

View a movie of the pin-ejection process:
> Click here for AVI version (68 MByte file)
> Click here for QT version (31 MByte file)
> Click here to download a zipped version (40 MByte file)

Modeling Notes: The Unigraphics part file was directly read by Femap V9.2 and used as the starting point for the contruction of the hex and tex mesh. To control the tetrahedral mesh size, an API was written to calculate the explicit time step based on the element's size and material properties. Mesh size was then controled to ensure a time step of the order of 0.1 micro-second. 

The material models were based on steel and a high-density polyurethane. A simplified rubber model (*Mat_181) was developed based on uniaxial tensile and compressive data. The cast steel material model as implemented using *Mat_24. Contact between the steel and rubber parts was enforced using *Automatic_Surface-to-Surface with Soft=1 due to the large stiffness differences between the two materials.

All analysis work was done with LS-DYNA V971.