Assignment 3-2D Element Formulation Challenge
AIM:
To simulate and compare the given challenge.
OBJECTIVE:
1.To run the simulation with the default property card assign as CASE-1.
2.To run the simulation with the changing in property card assign as CASE-2.
3.To compare CASE-1 and CASE-2.
THEORY:
HOURGLASS:
Hourglass is a deformation that is noticed when an element is deformed due to the applied load. But the strain energy due to this deformation is no recorded for that element.
It is also known as Zero Energy Deformation modes where an element is seen deformed.
METHODS TO CONTROL THE HOURGLASS:
1.Perturbation method or Viscous method.
2.Physical Stabilization method or Stiffness method.
1.VISCOUS METHOD:
1.This method is generally used for the elements with Ishell:1,2,3,4 or Q4 elements.
2.The process how this method work is when the hourglass deformation occurs. There will be some damping applied which is stablizes the deformation which results in controlling the speed of deformation.
3.But this damping opposes only the velocity but no the force. So the force is introduced which results in adding some stiffness to the elements. This stiffness helps in contolling the hourglass.
4.The force is applied externally by some other means. But not from FEA nature. This force constitutes energy called Hourglass Energy.
5.If the hourglass energy is added along with the kinetic energy and Internal energy. A balance system is obtained.
6.Recommended for high velocity or high strain rate problems. A huge amount of hourglass energy is generated.
2.STIFFNESS METHOD:
1.In this the stiffness is getting added right from the material level. This will have a large effect on our componnent.
2.It is recommended for fewer velocity problems.
3.Used for QEPH elements.
4.Less amount of hourglass energy is needed. Because it is going to be controlled before it arises.
i)Q4 element:
1.It is an reduced intergrated element. Because it has only 1 integration point for an element.
2.It is represented in the radioss solver by an entity name Ishell.
3.The cost required to solve this type of element is relatively low.
4.But there will be no accuracy in the results.
ii)QBAT element:
1.It is fully integrated element which means it comprises 4 integrated points. Each point is near to each node.
2.It is represented in the radioss solver by an entity named Ishell:12.
3.Usin this element is not econmical. But the results are more accurate than the remaining Ishell elements of quads.
iii)QEPH element:
1.It is an improved under-integrated element with physical hourglass stabilization within itself.
2.It represented in the radioss solver by an entity named Ishell:24.
3.This type of element is mostly used recently.It is widely used in the automotive industry.
iv)CO element:
1.It is a standard co-rotational triangle with modification for large rotations.
2.It helps in representing the tria elements with the entity name Ish3n:2.
3.It consists of 1 integration point.
4.No hourglass deformation and Results may not be accurate.
KEY PARAMETERS IN /PROP/SHELL:
1.Ishell : To select the element formulation for 4-noded shell elements.
2.Ish3n: To select the element formulation for 3-noded shell elements.
3.N: To choose the number of integration points through the thickness.
4.Ismstr: To specify whether the strain formulation is small or large.
5.Iplas: To choose method for the calculation of post yield strain.
6.Ithick: To determine if the thickness is constant under load or if the element thins.
PROCEDURE:
FOR CASE-1:
1.Import the model file as SOLVER DECK in RADIOSS interface.
2.Next step is to assign the value of time step in ENG_RUN card as 55ms as per question.
3.Here next we have assign the number of animation steps as 50ms as number of animation step as per the requirement.
Tfrequency = TIME STEP/NO.OF ANIMATION STEP
=55/55 =1.
4.In the property card every parameter is by default.
5.Now to run the simulation goto ANALYSIS > RADIOSS.
6.In the RUN option panel it s recommende to write -nt 4. It is assigned to do the simulation at faster rate.
7.Click the RADIOSS and it will generate the process and show JOB IS COMPLETED.
8.Now click on the results it will directly take you to hyperview where we can see the animation of the simulation. Animation file are in named as h3d.
9.Click apply and switch to contour mode.
10.After switching choose the RESULT TYPE to see the deformation.
11.Safe tolerance is -15% to +5%.
12.Graph for plotted for this various energy. For plotting graph we have to switch to hypergraph tab and import the file TO1 which is stands for time histroy.
FOR CASE-2:
1.Assign all the parameter property.
2.After assiging run the simulation same as CASE-1.
3.Safe tolerances is -15% to 5%.
4.Graphs for plotted for this various energy. For plotting graph we have to switch to hypergraph tab and import file TO1 which is stands for time history.
COMPARISION:
1.Obtained maximum energy error:
Case-1: -10.3%
Case-2:-0.1%
2.Obtained maximum kinetic energy:
Case-1: 0.3563E+08
Case-2: 0.4376E+08
3.Obtain maximum internal energy:
Case-1:0.1932E+08
Case-2:0.1750E+08
4.Hourglass energy:
Case-1: varying hourglass energy.
Case-2: constant hourglass energy.
5.Reason for hourglass energy:
Case-1: The elements dosent have physicall stabilization.
Case-2: The elements have physical stabilization.
6.Requirement for hourglass energy:
Case-1:It requires hourglass energy to the energy balance.
Case-2:No hourglass energy is required to balance the energy.
7.Output:
Case-1: The result is less accurate.
Case-2: The result is accurate.
OBSERVATION:
1.Thus the simulation with the default property card assign as CASE-1 obtained.
2.Thus the simulation with the changing in property card assign as CASE-2 obtained.
3.Thus the comparision of CASE-1 and CASE-2 performed.
4.Learned how to use hypergraph.
RESULT:
Thus the simualtion and comparision for the given challenge is determined sucessfully.