Comparing the results of a rail crashing on the rigid wall with base element properties and improved shell element properties

Comparing the results of a rail crashing on the rigid wall with base element properties and improved shell element properties

Objectives: the main objective of this assignment is to compare the result with default properties and recommend shell element properties and understand the graph results

Procedure:

CASE1: Simulations with default shell element properties

1. Import the crash beam file by using import solver desk
3. Change the run time to 55ms it can be done in ENGINE_RUN card, it is the time required to run the simulations
5. To maintain the number of animation file as per the time step , we need to edit card value of animations (ENG_ANIM_DT card).so we taken time at 30ms,therefore Tfreq as 1.833
7. The above time step and animations file which had been changed should be reflected in engine file_0001.rad
9. As per the objective we have to run the simulation without any modification in element properties card(default)
11. We have to run the simulations, go the hypermesh panel in the analysis menu and load the starter input file from the target folder and hit radios tab, so that required file can be saved in the respected folder it will generate animations file in .h3d and time history in runmane_T01.
13. By the end of the simulations, we have to check the energy error and mass error and determine whether result would be acceptable. it can be done by view engine output file
14. In the engine out file , we need to check if the energy error and mass error are within the limit
15. If the error is negative, it means that some energy has been dissipated.
16. In case of under integrated elements (Belytschko shells, solids with 1 integration point), the Hourglass energy can also explain a negative Energy Error since it is not counted in the energy balance. The normal amount of Hourglass energy is about -10% to -15%.

If the error is positive, there is an energy creation.

In case of using QEPH shell formulation (Ishell=24) or fully integrated elements, the Energy Error can be slightly positive since there is no Hourglass energy and the computation is much more accurate. An error of +1% or +2% is acceptable

11. We can see the energy error generated during the run is -10.3% which acceptable and for mass error it is recorded as 016% which is also within the limit ,after accepting the conditions we have to plot the various graphs
13. Play the animation file as we seen in the graphical area the model simulate as per the given data (default) and time step the visibilities of element is not as good they formed like something coarse
15. Let generate the displacement and von Mises stress contour plots for the model
17. Displacement (mag) analysis , with a maximum value of 7.610E+02
19. Von Mises with simple average method von mises stress is a value to determine if a given material will yield or fracture it mostly used for ductile material, such as metals
20. Now let us generate the necessary plots. Open a new page and switch to hypergraph 2D . load the time history file from the target folder
21. Import the element _formulatons_shell-3_assignmentT01 file and plot the required graphs.
23. To plot the graph go to global variable and generate the plot for internal Energy, kinetic energy, hourglass energy ,contract energy and total energy
24. Internal energy- The internal energy of a system is the energy contained within the system, excluding the kinetic energy of motions of the system as a whole and the potential energy of the system as a whole due to external force field
25. HourGlass energy-For the under-integrated (single integrations point at the middle) shell element , displacements and forces may exit for each node of the element, like the sum of these forces and displacement gives null strain and stress on the integrations points of the element
26. also generate the plots for Rigid wall force
28. Now all the requested contours and plots have been generated

CASE2: Simulations with recommended shell element properties

1. Import the crash beam file by using import solver desk
2. Change the run time to 55ms it can be done in ENGINE_RUN card, it is the time required to run the simulations
3. To maintain the number of animation file as per the time step , we need to edit card value of animations (ENG_ANIM_DT card).so we taken time at 30ms,therefore Tfreq as 1.833
4. We have to change the shell properties as per the recommended value give below
6. The value has been changed as per the respected parameters cad
8. We have to run the simulations (repeat step 6 from case 1)
9. The above changed parameters should be reflected in engine file_0001.rad
11. By the end of the simulations, we have to check the energy error and mass error and determine whether result would be acceptable. it can be done by view engine output file
12. In the engine out file , we can see that energy error number has been changed to -0.1, which indicate better results from case-1 even mass error result is also better then cas-1
14. After accepting the conditions we have to plot the various graph so go to huperview and import the h3d.file and run simulation, absorb the deformations of crash beam element is quit improved from case-1
16. Let generate the displacement and von Mises stress contour plots for the model
19. Now let us generate the necessary plots. Open a new page and switch to hypergraph 2D . load the time history file from the target folder
20. Import the element _formulatons_shell-3_assignmentT01 file and plot the required graphs.
21. To plot the graph go to global variable and generate the plot for internal Energy, kinetic energy, hourglass energy ,contract energy and total energy
23. also generate the plots for Rigid wall force
25. Now all the requested contours and plots have been generated for case-2

Result study:

no	Study report
Energy plots vs Time
1	Case-1	Case-2
	The hourglass energy gets accumulated over the time steps caused by the default element formulations Internal energy is lower as compare to case-2,because loss of energy which know as energy error Contact energy remained null Kinetic energy rate of diminishing is lower compare to the case_1 Hence case­-1 has lower velocity relative due to the kinetic energy	Almost zero hourglass energy registered over the time accused by the QEPH element formulations due to its fundamental ability to reduce the total accumulated hourglass deformations over the time steps Internal energy is bit higher as compare to case-1,due loss to no energy loss Contact energy remained null Kinetic energy rate of diminishing is higher compare to the case-1 Hence case-2 has higher velocity relative due to the kinetic energy
2	Resultant rigid wall force plot vs Time
	It is observed that the model have similar normal resultant force up to 20 ms. From 20 ms to 50 ms ,the case2 model tends to have a lower resultant normal force because of higher energy absorptions due to relatively larger deformation but from 50 ms up to 55ms, there is a spike in the resultant normal force . this spike in force is caused by the impacting of the lower member of the crash beam into the rigid wall .This signifies that the case -2 model has lower impulse in the normal directions relative to the case-1 model. Also relative to case-1 model, the case-2 model has lower result tangential force up to 50 ms again a spike is registered from 50 ms to 55ms due to the increase in contact area as caused by the impacting of the lower member of the crash beam into the rigid wall
	Von-mises strss contour
	case_1	case-2
	The von-mesis stress can be clearly seen to increase at he bending region in case-1 which is not clearly visible in case simulations The variations of von- misses stress contour plots using the using the simple averaging method for the crash beam with Q4(case 1) and QEPH (case-2) element formulation. The difference in the deformation mechanism is evident from the video which is caused due to the difference in the element formulation.
3	Displacement contour
	Case-1	case-2
	in both case the max deformations and the magnitude remained nearly similar with displacement being slight higher in case-2

Comparing all the result from both simulations
Parameters	default element		modifications to element properties
	Maximum value	minimum value	Maximum value	minimum value
Internal energy	2.00E+07	0.00E+00	2.00E+07	0.00E+00
Contact energy	25100	0	6100	0
Hour glass energy	6.40E+0.6	0.00E+00	0	0
Total energy	6.13E+07	5.50E+07	6.13E+07	1.26E+06
Rigid wall forces	1.14E+05	2.00E+04	1.07E+05	5.00E-01
Displacement	7.61E+02	2.11E+00	4.42E+02	1.03E+00
Vio Mesis	3.50E+02	0.00E+00	3.37E+02	0.00E+00

Conclusions

1. The Engine file is edited as specified.
2. The component is subjected to crash simulations with and without recommended element properties
3. The Separate out files are checked for energy error and mass error and acceptable case is judged
4. The Hyper graph plotting is done to understand the result

Link for case 1- https://1drv.ms/u/s!AlDYq9nTGAGChBh-rCuLxJY9XMlW?e=FhZGWq

Link for case 2 - https://1drv.ms/u/s!AlDYq9nTGAGChETCJ62lFwXgyAV1?e=oPwlIO