EDEM - Stress relaxation

Johnson_21712

Hello,

I hope this finds you well.

I am trying to perform a stress relaxation experiment in which the force increases gradually from 0 to the maximum force of 42 N. After reaching 42N, it is held constant for 50 secs and then decreases gradually.

Just to take things bit by bit, I decided to start with the gradual increase in force from 0 to 42N.

To achieve this, i used a force controller and a parametric equation of -(1+(1+t))  so that the force will increase gradually to the maximum force.  the picture below shows what I did.

However, while running the simulation, the punch started increasing gradually but I think this stopped immediately this comes in contact with the particles.

So using the analyst I plotted the total force against time and did not see any notable increase in the force from 0 to 42. I have included a picture of the plot for the punch and the particles.

Please I will appreciate any assistance on this. 

I have also included a video of the compression process.

Thank you.

 

 

 

Prasad Avilala_20558

Hi Johnson,

let me explain the phenomenon with a simple equation

Force=  Stiffness x Overlap means that force depends on stiffness and overlap.

Stiffness is obtained through the Young's/ Shear Modulus, the higher the modulus higher resistive force but the simulation time increases with shear modulus.

As an alternate instead of applying force, i would prefer to go with applying velocity/displacement

Question can arise for the same shear modulus with velocity how do we get large force, there is a lot more physicis involved but to simplify things when we apply a velocity/displacement it is a constant velocity applied irrespective of the time.

I would suggest applying a velocity/displacement rather than a force will help to achieve the necessary force but requires need couple of iterations to get the velocity at which 42N reaction force.

Apply initial velocity and verify the force on the punch at what velocity and time force of 42N is obtained then run the simulation for the desired time and pull the punch back to get material/stress relaxation.

 

Hope this helps.

 

Thanks,

Prasad A

Johnson_21712

Hello Prasad,

I will try this approach out.

Thank you so much for the response.

Johnson.