Assignment 3-2D Element Formulation Challenge

OBJECTIVE:

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

Import:

• The rad file is imported to hyperworks and is displayed as below.

• The elements view is set to shaded elems view which displays the elements as follows.

CASE-1

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

• Changing run time to 55ms:
• In model tree, under CARDS collector, ENG_RUN card have a Tstop of 60, which is changed to 55.

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

• Changing animation steps to 40:
• To have 40 animation steps, the frequency should be Run time/Animation steps = 55/40 = 1.375
• In model tree, under CARDS collector, ENG_ANIM_DT card have a Tfreq of 1.0, which is changed to 1.375.

3) The base simulation is run without any modification to element properties using Radioss option under Analysis tab.

• In the RUN OPTION panel it is recommended to write -nt 4. not stands for number thread it assigned to do the simulation at faster rate.
• Click RADIOSS and it will show JOB IS COMPLETED.
• Now click on RESULT, it will directly take you to hyperview where we can see the animation of the simulation. Animation file are in name of h3d.

Click apply

• Now switch to contour mode

• After switching choose the RESULT TYPE to see the deformation. I choose VON MISSES and click apply.

We can see animation

4. At the end of the simulation, do the energy error and mass error checks and determine whether results would be acceptable.

• After analysis, the .OUT file is viewed to check whether the Energy error and mass error fall within the aceptable range

• The Energy error starts from 0% to 10% which is within Acceptable range.
• Mass error stays constant throughout the simulation at 0.1659e-03 which is also within the Acceptable range.

5) If acceptable, Plot rigid wall forces, internal energy, hourglass energy, contact energy, total energy of the simulations.

• To plot the specific graphs, hyper graph 2-d is selected.
• Specified energies are plotted against time on the same plot as shown below:

From the plot obtained for base simulation without any modification to element properties, following observations are made:

• Internal energy increases throughout the simulation which is due to the force developed on tube due to deformation.
• There is a slight increase in hourglass energy throughout the simulation.
• Contact energy remains zero throughout the simulation.
• Total energy of the system has a slight decrease from the start to end of the simulation.

A new plot is created to plot the rigid wall forces.

Rigid wall forces are plotted against time as shown above.

• The rigid wall force curve is of a non-linear behaviour, which is due to the variation in the force exerted by the crush tube on the wall throughout the simulation.

Contour plot of Hourglass energy & Displacement is obtained using contour option under hyperview.

CASE=2

Changing the shell elements properties to recommended properties

Recommended properties:

Parameters		Comment
Ishell =24		QEPH 4 nodes shells are best combination of cost and accuracy.
Ismstr=2		Full geometric nonlinearities (default)with possible small strain formulation activation in RADIOSS Engine.
Ish3n=2		Standard 3 noded shell (C0)with modification for large rotation(default)
N=5		Number of integration points set to 5 for accuracy bending.
Ithick=1		Thickness change is taken into account for accuracy.
Iplas=1		Iterative plasticity for good accuracy.

The shell elements properties are modified to recommended property values:-

• Changing run time to 55ms:
• In model tree, under CARDS collector, ENG_RUN card have a Tstop of 60, which is changed to 55.

• Changing animation steps to 40:
• To have 40 animation steps, the frequency should be Run time/Animation steps = 55/40 = 1.375
• In model tree, under CARDS collector, ENG_ANIM_DT card have a Tfreq of 1.0, which is changed to 1.375.

• Running the simulation with the newly defined recommended properties using Radioss option under Analysis tab.
• Create a folder to save the rad files in local directory.

• edit options providing number of threads as " -nt 4 ".

• Click RADIOSS and it will show JOB IS COMPLETED.

• Now click on RESULT, it will directly take you to hyperview where we can see the animation of the simulation. Animation file are in name of h3d.

Click apply

• Now switch to contour mode

• After switching choose the RESULT TYPE to see the deformation. I choose VON MISSES and click apply.

We can see animation

• After analysis, the .OUT file is viewed to check whether the Energy error and mass error fall within the aceptable range.

• The energy error starts from 0% to -0.10% which is within acceptable range.
• Mass error stays constant throughout the simulation at 0.1659e-03 which is also within the acceptable range.
• Since the error values are acceptable, rigid wall forces, internal energy, hourglass energy, contact energy, total energy of the simulation are plotted with the help of hypergraph 2-D
• Specified energies are plotted against time on the same plot as shown below:

From the plot obtained for simulation after modification to element properties, following observations are made:

• Internal energy increases throughout the simulation which is due to the force developed on tube due to deformation.
• Total energy remains same throughout the simulation.
• Hourglass energy and contact energy remains zero and follows the origin throughout the simulation.

A new plot is created to plot the rigid wall forces.

The rigid wall force curve is of a non-linear behaviour, which is due to the variation in the force exerted by the crush tube on the wall throughout the simulation.

Contour plot of Hourglass energy & Displacement is obtained using contour option under hyperview.

Comparison:

Default

Recommended Properties

BELOW ARE THE COMMENST MADE BY COMPARING ABOVE TWO CASES.

When recomended properties are changed from the base values, simulation results shows that

• Hourglass energy which was increasing changed to zero throughout the simulation.
• Contact energy characteristics are same in both cases.
• Internal energy is having a gradual increasing characateristics in both the cases.
• Rigid wall forces also decreased to a lower value than that of default value rigid wall force value.
• Contour plots shows that there is a slight increase in maximum displacement of element with recommended property values.

CONCLUSION:--

1) Learned how to carry out simulation.

2) Learned about property card.

3) Learned how to use hypergraph 2D.

4)Learned how to use Hyperview.