How to determine fracture toughness Kic from a punch test?

[IB7899]

I am looking to determine fracture toughness for aluminium, from a punch test. I have the dimensions of the specimen and the load-displacement curve of the test. I have seen how to calculate Kic for brittle materials from a punch test but am struggling to find a formula for ductile materials such as aluminium.

thanks

 

[IB7899]

anyone please?