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[Subhash N]

I am Trying to simulate the tensile testing process at various strain rates. Can anyone say what should be the appropriate boundary conditions and how to find the principal stresses in all the directions at a particular point of the specimen.

[peteroznewman]

What is your purpose in simulating the tensile testing process? 

What question do you have that you want the model to answer?

[Subhash N]

Thank you for responding sir,

Yes, I want to simulate the tensile testing process for various strain rates and I want the stress vs strain plots.

 along with that, I want the mean stress or the principal stresses acting at a point.

[peteroznewman]

What material data do you have to input into the simulation?

[Subhash N]

I have the Elastic data like Young's modulus and Poisson's ratio

for plastic data I am using Johnson-Cook material model  

[peteroznewman]

Here is a paragraph on Johnson-Cook Strength material model from the ANSYS Help.

Use this model to represent the strength behavior of materials, typically metals, subjected to large strains, high strain rates and high temperatures. Such behavior might arise in problems of intense impulsive loading due to high velocity impact.

This model is only available in Explicit Dynamics, which is the solver to use for very high speed events.

When you say you want to "simulate the tensile testing process at various strain rates", what strain rates are you talking about?

[Subhash N]

I want to simulate the tensile testing process at 1500/sec, 2500/sec and 3500/sec 

at these strain rates, I want to identify the mean stress or the principal stress induced in the elements.

Can I get principal stress values in all three directions?

[peteroznewman]

 

Yes, you can get principal stress values from a simulation.

Please describe the testing machine that delivers strain rates of 3500/sec.

What level of strain do you want to reach at that strain rate?

Do you have the low strain rate properties of the material you want to simulate at high strain rates?

 

[Subhash N]

This high strain rate can be achieved with tensile Split Hopkinson Pressure Bar, which consists of two bars the dogbone shaped specimen is mounted between these two bars. out of these two bars one of which is called the incident bar, this incident bar is struck by a striker bar (which is propelled using high-pressure gas) which results in such high strain rates.

Can you please tell me how can I find the principal stresses acting on any element

[peteroznewman]

Build the model in Workbench. You will either use Transient Structural or Explicit Dynamics. In either case, when you click on the Model item, the Mechanical program will launch. Under the Solution branch of the model, you insert a Stress result and pick the type: Maximum Principal, Minimum Principal or Middle Principal.

[Subhash N]

Ok, I will do that 

But how do I get the direction of the principal stresses 

basically, I want the principal in x, y and z directions or I need the Mean stress

Can I get Mean stress directly?

[peteroznewman]

You insert a Vector Principal plot. That will plot a triad on each element showing the directions of Maximum, Middle and Minimum Principal directions.

[Subhash N]

Ok I will Try that 

Thank you so much for your help sir

[peteroznewman]

You're welcome. Please click the Is Solution link on the post with the answer to your question. That will mark this discussion as Solved.