Effective Strain of Frictionless Punch on Deep Plate

AI Thread Summary
The discussion focuses on determining the effective strain of a frictionless punch on a deep plate under plane strain conditions. The initial approach considered related tests, such as bulge tests and indentation methods, but these were deemed unsuitable due to differences in material behavior. The need for a stress-strain relationship is emphasized, as calculating strain requires knowledge of initial areas and lengths, which complicates the analysis. Suggestions include exploring plastic flow theories and using finite element methods for more accurate modeling. Overall, the conversation highlights the challenges in applying existing methods to this specific problem.
1350-F
Messages
15
Reaction score
0
I'm trying to figure out the effective strain of a frictionless punch on a deep plate. For simplicity's sake let's say it's in plane strain. Don't quite know where to start. Closest thing I can think of is the strain from a bulge test, but that involves a thin sheet. Looked at some indentor (Vickers, Brinell etc.) strains also, but these might not be applicable, since the indenter does not travel that far into the workpiece. I also looked at some of the literature concerning ballistics but they don't really report strain or how they calculated it. I feel like there's something very simple that I'm missing here.

I'd be grateful if someone could put me on the right path.
 
Engineering news on Phys.org
Shear stress .
 
  • Like
Likes 1350-F
Nidum said:
Shear stress .

I thought about doing σ = Ymε, but I don't have a value for Y!

[Edit] I suppose I could look it up, however
 
Nidum said:
https://www.google.co.uk/search?q=s...oTCKLqksi-98gCFUsaPgodFwgI_g&biw=1680&bih=939



Well no matter how I calculate the stress, I still need some sort of stress-strain relationship. Any method I can think of to find strain otherwise has to include reduction of length, area, etc. I could indeed calculate the new area created by the cavity but if my object is semifinite I wouldn't know the initial area.
 
Draw me a diagram so that I can understand what your actual problem is .
 
Here you go
 

Attachments

  • IMG-20151104-00002.jpg
    IMG-20151104-00002.jpg
    28.8 KB · Views: 377
I think you are actually looking at a plastic flow problem . There are various theory's regarding plastic flow in metals . Modelling real situations analytically is difficult and FE methods often have to be used . A not very accurate but sometimes useful approximate solution just assumes that all metal in zone around active end of punch is at yield stress .

Not the best of explanations but it's somewhere to start :

https://en.wikipedia.org/wiki/Flow_plasticity_theory
 
My inclination was to find P/2k from a hodograph and then use that pressure to solve for strain using th the formula I posted above. However I wasn't sure whether there was a commonly used formula or something based on the individual strains.
 

Hot Threads

Recent Insights

Back
Top