Assignment 3

Objective: Comparison of results with base simulation and improved shell element properties.

Case 1

setup and Procedure: below details are the model with out any modification of crash beam ,

1.Using the crash beam file from the previous assignment, we changed the run time to 55 ms.

2. Changing the number of animation steps during simulation to a minimum of 25 and maximum of 60.

given run time=55ms

the no of steps min=25 and max=60

then the average will be the 42.5

frequency =time/step

f=55/42.5

Time frequency=1.29

3. Run the base simulation without any modification to element properties.

I run the base model with out any modification below at the end of simulation we found energy error and mass error as follow,

Without modification:

Withmodification:

• The error should be –ve and that should decrese and it must less than 15% at the end of the computation 5% is good fr models.
• If the errors increse means there will be problem in the model we need to look in to the model
• So in standard the error should be with in -15% and good to hv -5% and closer to the zero is good.
• If any +ve energy means energy have been created in the model that will crearte a model issue ,so that sholud be –ve or zero .

Plots:

Rigid wall forces:

Internal energy

hourglass energy

contact energy:

Total energy:

Case 2 setup and Procedure:

setup and Procedure: below details are the model with modification of crash beam,

Plots:

Rigid wall forces

Internal energy

hourglass energy

contact energy:

Total energy:

8. Creating a brief report comparing all the results as follow,

• In rigid wall force after modifying the properties time taken to failure of the part will be more as shown below

• In internal energy in both cases increasing we can say that strain energy is also increasing w.r.t time as seen in the graphs

• hourglass energy as we seen there is no hourglass energy change after changing the properties before that there is much HG as shown.
• 

• Total energy is decresing more inafter modification of properties

• 
  HOURGLASS :Hourglass is modes of deformation that occur in under integrated elements and zero stress will be produced. This can affect solution accuracy by varying the structures true response.

This leads to inaccurate stress ,strain and deflection results.

This can be avoided by using 2 methods as follow,

1. Perturbation(Q4 elements)
2. Physical stabilization(QEPH elements)

• RIGID WALL FORCES:

• AS we observed from the graphs when first impact resultant force is high and start decreasing through out the time ,and some fluctuation also present at the middle of simulation
• In 2 case there is sudden rise in the graph that is because at the end the full part of the body is rushed to the rigid wall and more normal force acted at that time.

Conclusion is after modification of the properties it shows more accurate results then without modification of propeties.