Assignment 3-2D Element Formulation Challenge

• AIM:-

To perform the 2D Element Formulation using the hypermesh radioss model software.

• OBJECTIVE:- The following are the given object.

Comparison results in between simulation & improved shell element properties

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

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

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

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

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

6. Change all the shell elements properties to recommended properties, save this as separate, rad files and run the simulation.

7. Follow steps 5 and 6.

8. Create a brief report comparing all the results from steps 5 and 6 for both simulations.

9. Comment whether there is any change in the results and why there is any change in the result.

• CASE 1 SETUP AND PROCEDURE :-

• UPLOADING THE MODEL:

• The base file is loaded in the hypermesh software and the figure is as follows:

• EDITING THE RUN TIME & ANIMATION DETAILS :-

• The run time has been changed from 60ms to 55ms in the ENG_RUN control card which is show below.

• The output time step has been chosen to give 40 animation steps and therefore the frequency is as follows:
• Tfreq = 55/40
• Tfreq = 1.375

• This value can be changed in the ENG_ANIM_DT Control card.

• PERFORMING THE ANALYSIS :-

•  The file is run without any modifications in the shell element properties under the Analysis tab>Radioss.
• After the analysis, the Out file is opened to check the energy error and the mass error values.

• Here, the options is given as -nt 4 which means there are 4 cpus running simultaneously to solve the problem.

•  The energy error values change from -0.0% to -10.3% which is within the acceptable limits and the mass error remains constant with the value of 0.1659E-03.
• Since the errors are within the acceptable range, Plot rigid wall forces, internal energy, hourglass energy, contact energy, total energy of the simulations.

• The Beam_elementh 3d file is opened to see the animation of the component which is shown below:

• After that,the hypergraph 2D window is opened to plot all the graphs.The T01 file is opened to plot the internal energy, hourglass energy, contact energy, total energy of the simulations.

• From this graph the observations are as follows:

1. There is a slight decrease in the total energy of the simulations from the start to end.
2. There is an increase in the Internal energy of the system(strain energy) because of the deformation of the tube as it comes in contact with the mass.
3. There is an increase in the Hourglass energy in the simulations.
4. The contact energy remains zero throughout the simulation.

• Secondly, the rigid wall forces are plotted in a new plot which is as below:

• Here, we have plotted both the normal force and the resultant force.The normal force decreases because of the internal deformations that

happened inside the model, the resultant force is the combination of both the normal and the frictional force.

• The contour option is used to plot the displacement of the component with different colour regions.

• Similarly,the contour option is used to plot the Hourglass energy of the component with different colour regions.

• CASE 2 SETUP AND PROCEDURE :-

• LOADING THE MODEL :-

• The base file is loaded into the hypermesh software.

• In the case setup 2, running the simulation with the recommended properties and then comparing both the results.

Recommended properties:

• EDITING THE RUN TIME,RECOMMENDED PROPERTIES AND ANIMATION DETAILS :-

• The run time has been changed from 60ms to 55ms in the ENG_RUN control card which is show below.

• The output time step has been chosen to give 40 animation steps and therefore the frequency is as follows:
• Tfreq = 55/40
• Tfreq = 1.375

• This value can be changed in the ENG_ANIM_DT Control card.
• The recommeded values are updated and it is as follows:

• PERFORMING THE ANALYSIS :-

•  The file is run without any modifications in the shell element properties under the Analysis tab>Radioss.
• After the analysis, the Out file is opened to check the energy error and the mass error values.

• Here, the options is given as -nt 4 which means there are 4 cpus running simultaneously to solve the problem.

•  The energy error values change from -0.0% to -0.1% which is within the acceptable limits and the mass error remains constant with the value of 0.1659E-03.
• Since the errors are within the acceptable range, Plot rigid wall forces, internal energy, hourglass energy, contact energy, total energy of the simulations.

• After that,the hypergraph 2D window is opened to plot all the graphs.The T01 file is opened to plot the internal energy, hourglass energy, contact energy, total energy of the simulations.

• From this graph the observations are as follows:

1. The total energy of the simulations remains the same from the start to end.
2. There is an increase in the Internal energy of the system(strain energy) because of the deformation of the tube as it comes in contact with the mass.
3. The contact energy and Hourglass energy remains zero throughout the simulations and follows the origin.

• Secondly, the rigid wall forces are plotted in a new plot which is as below:

• Here, we have plotted both the normal force and the resultant force.The normal force decreases because of the internal deformations that

happened inside the model, the resultant force is the combination of both the normal and the frictional force.

• The contour option is used to plot the displacement of the component with different colour regions.

• The contour option is used to plot the hourglass modes of the component with different colour regions.

• COMPARISON OF BOTH THE CASES :-
• DEFAULT SIMULATION WITHOUT RECOMMENDED PROPERTIES :-

• SIMULATION WITH RECOMMENDED PROPERTIES :-

• OBSERVATIONS :-

1. The total energy remains constant after applying the properties whereas it was decreasing in the default simulation.The energy error was also -0.1% with the properties and -10.3% in the case of default simulation.
2. Hourglass energy has been reduced to zero after applying the properties whereas it wasn't in the default zone.
3. Contact energy remains zero in both the cases.
4. The internal energy increased in both the cases.
5. Rigid wall forces also decreased to a lower level than that of the default rigid wall forces.
6. In the case of displacement from contour plot, the value increased as compared to the default displacement value.

• THEORY ON HOURGLASS :-

• WHAT IS HOURGLASS :-

1. Hourglass are nonphysical modes of deformation that occur in under integrated elements and produce no stress.
2. As stresses are not produced, it reduces the accuracy and true response of the structure.
3. It leads to inaccurate strain and displacement results with unrealistic deformation.

•   HOURGLASS PRODUCED :-

1. In an under integrated element, there are forces and displacements which exist for each node of the element.
2. If the summation of all these forces and displacements provide zero stress and strain on the integration point of the element,then the element fails to calculate the stiffness for the mode of deformation.
3. Due to no stiffness calculation,the deformation happens in a wierd manner.
4. This is when we call the element has entered into hourglass deformation.

• CONTROL OF HOURGLASS :-

1. To avoid hourglass, we go with reduced integration elements.
2. we can go with two methods for controlling hourglass parameter:
3. Ishell = 1,2,3,4(Q4) employs perturbation method for controlling hourglassing.
4. Ishell = 24(QEPH) employs a physical stabilization method for controlling hourglassing.

• CONCLUSION :-
• Therefore the 2D element formulation has been completed.
• Understood, how to plot rigid wall forces, internal energy,hourglass energy, contact energy, total energy of the simulations.
• Noted, how to run the animations of the component.
• Studied theory on hourglass modes.