Assignment 3-2D Element Formulation Challenge
OBJECTIVE-
the primary objective of this assignment to compare two simulation wih diffrent shell element properties. the comparison would be between the one with default properties and one with the following properties.
PARAMETER COMMENT-
Ishell=24 QEPH 4 nods shell 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 (co) with modification for large rotation (default).
N=5 number of integration point set to 5 for accuracy bending.
Ithick=1 thickness is change taken into account of accuracy .
Iplass=1 iterative plasticity for good accuracy.
PROCEDURE-
1) we shall be changing a couple of simulation properties by accessing them through the hyperwork.this first quetion require us to change the run time to 55ms. we need first need to import the solver deck file in quetion to RADIOSS.
for that we need to go to FILE> IMPORT> SOLVER DECK.the brings up the import menu . here we can select the file we need to import . the file would be the STARTER INPUT DECK file( which is the file that end with 0000.rad)
with the model imported we can go ahead and change the run time to 55ms( as required). to do that we need to proceed the solver tab in the sidebar.proocessing the ENGINE_KEYWORDS>RUN>ENG_RUN, we can now edit properties of ENG_RUN in small window below the tab.
2) the next quetion requires us to change the number of simulation step to a minimum of 25 and a maximum of 60. for this we need to go same the solver tab and procceed to ENGINE_KEYWORD > RUN > ANIM >ANIM/DT. we shall be changing the perticular attributes properties.
in properties section we can change the Tstart value to be 25 and to accomodate a maximum of 60 animations steps, Tfreq can be set at 1.
3) next requirement is to run the base simulation for that , we need to save the current file with edited parameter . this can be carried out via the analysis process .
for this we can go to the analysis section from the bottom panel. there we select RADIOSS.
i the next section , we are given the option to save the file before running it in the solver. we can go ahead and given it a different name from the base file to avoid confusion. clicking save as let us to do that.
after saving before running it into the solver .we can activate into include connector and in the options bar,we need to enter -nt 4 to increase the proccesing power of the solver ( as in to use all 4 cores) after that we can click 'RADIOSS' to activate the solver and it process it the file .
now we just need to visualize it for that , we need to switch to the hyperview utility.this can be done by clicking the client selector option in the toolbar ( might need to be activated from VIEW > TOOLBARS > HYPERWORKS > CLIENT SELECTOR). for that menu we can select hyperview to switch to it.
after accessing the hyperview . we can asked to input the simulation file.for this we shall be using the h3d file that was genrated when RADIOSS procesed the starter file . it should be genrated in the same folder. after selecting it . we can click 'apply'.
doing so genrates the simulatiwe on animation we can can change what is being represnted by selecting the contouroption in the toolbar.
4) the next step to carry out energy error and mass error check and this is done by analysing the RADIOSS engine output file . this can be accessed from the same directory as the satrer and engine file and it is denoted by the out extension . we need to check that file that contain _0001.out by using any text editor.
an opening the file can scrolling down to the end . we can see the final energy and mass error values.
the final energy error is -10.3% which is less than the threeshold of -15% and is acceptable. the acceptable energy error values are supposed to between -15% and 10% the closer to 0 it is is the better.
5) with energy and mass error demand acceptable, we can go ahead plot graph for this we will shall be using the hypergraph client . we can switch to it using the same client selector option in the toolbar. in the hypergraph section , we are met with a graph and met in the panel below we are input a file this will be result will genrated by the RADIOSS solver.( also known as the T01 file). this file is available in the same directory as the starter engine and animation file . the file name end T01. After adding it we can select the variable that would go with time (x axis).first we can take a look at the energy graph ( internal energy, hourglass energy,contact energy,kinetic energy and total energy.)
now to genrate a graph for rigid wall surface (rigid wall/Rwall force - 4 RIGID WALL1- total resultant force.)
6) for this quetion we are carried out simulation for a new case recommended shell element properties,we can repeat the process of importing the orignal server deck file and change the values of Tstop,Tstart and Tfreq in the solver tab. after that we can move to the model tab and goto the properties submenu . the shell properties of the model componants are to be changed so we need to select each of 'Hat- section and close out panel one by one and change the values in the properties window below in the shown.
as specified Ishell would be 24,Ismstr would be 2, Ish3n would be 2 , Nwould be 5,Ithick would be 1 and Iplas would be 1. these values are changed for both affromentioned componet.
after they changed we need to the gernrate the RADIOSS analysis file again via analysis> radioss in the bottome panel . we can save it in diffrent name and assign the same setting as the previous case( option.'- nt4' and which include connector checked . the solver file is then genrated by clicking the radioss.
after that , we can switch to hyperview to genrate the simulation . like last time . we need to pick the h3d file of this case and click apply.
the following animation shows the von mises stress contour of the component using recommended shell formulation the settings.
7) having genrated the simulation , we can go ahead and carry out energy and mass error check again using this perticular simulation RADIOSS output file. this can be accessed from the same directory as the starter and engine file of this simulation and denoted by the .out extension . we have need to the check the file that contain_0001.out by using any text editor.
as we can see , there is drastic reduction in energy error , as we evident inthe more natural looking the simulation (reduction in horglass energy )
now we can genrate the graphs by switching to hypergraph and selecting the simulations T01 file , firstly the energy graph.
as we can se the almost no hourglass energy and this corresponds with the energy error observation . we shall the genrate the graph for rigid wall forces.
8 and 9) the obivious difference in both simulation in the reduction in hourglass energy . the introduction of QEPH shell formulation(Ishell =24) in the second case, provide an artificial stiffness to the shell elements and helps contour hourglass formation.
as a result hourglass reduction in the more natural looking simulation in the second case with less crumpling.
as reduction in hourglass mean a reduction in hourglass energy since an artificial ,external force needn't be applied to negate the hourglass formation ( as in the case Q4 elements)
the more realistic simulation also resulted in a different resulatant force graph that represent the collision events more realastically . the formation of kink at round 20ms causes a sudden spike in case 1, whreas the second simulation , as the QEPH shell formulation is used . there is no sudden spike as the element are deformed in much better manner . understandbly there is a large force at the begining . which happens at contact . and in the same in both cases.
RESULT-
1) two simulations were carried out on the sme crush beam using different shell element formulation properties.
2) comparing the results of both cases . it can easily be figured out that there is a big difference in the values of hourglass energy,internal energy and rigid wall forces.
3) also the amount and nature of the deformation of the 2nd case are much higher and different than first case. this deformation is more practical than the first case .
4) it was established that using the recommended setting helped reduced hourglass formation drastically du to introduction of the physical stabilization method that is deployed by QEPH elements.