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I am trying to drill through a layer of Aluminum alloy (Al 6061). The model consists of two layers one above the other with Aluminum being on top and steel alloy on the bottom while the tool is made of 4340 steel alloy and is deformable too. The thickness of Aluminum layer is 1.5 mm while that of steel alloy is 1.4 mm. There are two steps involved in the model i.e. Penetration and Cleaning. The tool drills through the first layer halfway through second step 'cleaning'. A feed of 500 mm/sec (increased to complete simulation in short time) and a force of 5 kN is applied on top of the tool. I have used Johnson-Cook plasticity model for all three parts and Johnson-Cook damage model for the Aluminum layer. All the parts are modeled using Lagrangian specification and coupled temp.-disp. dynamic explicit step.

I'm facing difficulty in choosing right constants for the JC damage model and value for damage evolution for the Aluminum layer as there are many values available in the literature for Al 6061 and they vary significantly. Same is true for JC plasticity models for all three parts. The values for the JC damage constants is as follows:
D1= -0.77, D2= 1.45, D3= 0.47, D4=0, D5= 1.6, TRANSITION TEMP=293 K, MELTING TEMP.=855 K,
Damage evolution is specified using fracture energy criteria and value is 0.0001
(this is just a trial value since I'm not sure about using the formula available in literature which uses Poisson's ratio, Elastic modulus and Strenght intensity factor)

The above values were taken from a paper studying projectile deformation (high velocity) of Al 6061. In the simulations I've observed that elements are not being deleted in the Aluminum layer right beneath the tool tip but elements are being deleted from the side surfaces which come into contact with the sides of the tool. Also, the elements beneath the tool do not undergo much deformation thereby not reaching damage failure criteria. The Aluminum layer is getting sort of compressed as in forging instead of elements being deleted from it due to interaction with tool.

Another problem noticed in the simulations is of intersection of Aluminum layer elements and tool elements which can be due to high feed rate and 'penalty' contact algorithm in the 'general contact'.

I have tried using different values available in the literature and also varied the above mentioned values but the result was almost the same for all simulations.

Can anyone suggest JC damage values they have sued for Al 6061 alloy or a way to get the elements deleted in the Aluminum layer so that tool can drill through? I am attaching image of the model at the end of second step (cross-section view).
Any suggestion/advise is welcome!
Thanks in advance!

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