Assignment 5-RADIOSS Interfaces & Study of Effect of Notches Challenge

AIM :

       To run the crash tube model by using different types of the contact interface and tweak the model shape & settings as per requirements.

       Discretize the given bumper assembly with the given element size. All should be done in HyperMesh RADIOSS.

OBJECTIVES :

      Run the crash model without any modification.

      Change into 6 as "Inacti" and run it.

      Switch to type 11 contact and run it.

      Remove the notches from the model, remove the boundary condition on the rigid body node and then run it.

      Create a new notch in the middle of the model and run it.

      Create a new notch on the opposing faces in the model and run it.

      Perform geometry cleanup on the bumper assembly.

      Performing meshing operation on the bumper assembly as per given quality criteria.

PROCEDURE FOR OBTAINING THE OBJECTIVES :

PREPROCESSING :

     Open a Hyperworks software & keep HyperMesh interface. Since the given file is in ".hm" format so we can directly open it in the HyperMesh.

     After opening the bumper component, it will look as below.

     

     We have to remove the unwanted nodes from the component. Open the "Temp node" submodule & click the clear all options to remove the nodes from the model.

     After removing the nodes from the component, it will look as below.

     

     By using the "Quick edge" option we can fix the geometrical issues from the component.

     Use the "Toggle" option to fix the free edge is converted into a shared edge line or Non-manifold edge.

     After fixing the geometrical issues on the component, it has looked as below.

    

     Before going perform the meshing operation, we have to set the element quality criteria.

     In this component, we have to perform the meshing as per these criteria as below.

     

     Go to the "Auto mesh" option, provide the element size as 5 mm and then perform the meshing operation on the surface by surface.

     After done the meshing on the component, it will look as below.

     

 

SOLVING :

Importing the model :

     Open a HyperWorks software, select the "Radioss" as an Explicit solver and then switch to "HyperMesh". Followingly, import the appropriate file through the import solver deck which crash tube.

     After importing the model, it will be showing in the Hyperworks graphical window as below.

     

     As per requirement, we have to add the component and assigned it to a PART.

     

     Apart from that, we don't edit values in any parameters which come under the model browser. Perform the simulation as it is for all the cases.

     

Important Interface parameters :

Igap : Determines how the size of the gap is calculated.

 

GAPmin : Minimum gap for activation of the interface.

 

Inacti : Action to takes if initial penetration exists.

 

Istf : Affects how the stiffness of the interface is calculated.

 

Iform : Friction formulation.

 

Stmin : Minimum stiffness to use in the interface.

 

Idel : Behaviour of slave and master segment if an element fails

 

CASE 1 :

     In this case, we have to run the model without any modification as per requirement.

     By default, TYPE 7 has been assigned in this case. TYPE 7 is a node to surface contact with defined self contact.

     An "Igap" is set to be zero so the solver will take it as a constant gap between slave node and master segment. If you want to change the "Igap" value instead of 0, then we have to define the "Gapmin" value in this card as before set the "Igap" parameter. In this case, we kept "1" as a "Gapmin".

     An "Inacti" is set to be in 0 which is a default one, it will take any action while any intersection happens.

     An "Idel" is set to be in 0 by default, it isn't a recommended one. But, we keep this as it is.

     

      Select the "Radioss" sub-panel under the "Analysis" panel, save the file in the separate folder, and click the radioss button to solve the problem by solver itself.

     After calculating the model, a solver is generated different files such as the Starter listing file, Engine listing file, Animation files, Time history file and then restart file.

     If the mass error has been falling in between -15 % to -5 %, that means the mass error is an acceptable thing. In this case, the error has been falling between -5 to 1 which means results are accurate and acceptable too.

     A mass error has been zero from beginning to end, so it's an acceptable thing.

     

       After completion of solving, switch to "Hyperview" from the "HyperMesh" section.

       Select the appropriate file in an "h3d" format and open the same file in the Hyperview interface.

Contour plot for Von mises stress :

       Stress generated up to 0.69 Mpa only from zero at the beginning.

       A component starts deformation at the middle where the notch is located. A stress concentration is more on the notch area. And then continuously stress is generated on the bottom of the middle notch.

     

      Switch to the "HyperGraph 2d" interface instead of the "Hyper View" interface for plotting the required one.

      A resultant force is a resultant of x component, y component & z component. The resultant force is plotted below from starting time to termination time.

      Initially, a component has more resistance force due to inertia. Over the period of time, a component starts to deform so eventually inertia is reduced as well as a resultant force is also reduced.

     

Contact energy :

     

      As we know the formula for internal energy = Q + W. Since, there's no heat transfer in the system so only have to consider work done for calculating the internal energy. As we know, a product of force and displacement is work done. Since a displacement is continuously increased on the plate over a period of time so work done is to be increased, as a result, internal energy too increased respectively.

     

     As we know the formula for Kinetic energy = 1/2 * m * V^2. As we see below, kinetic energy is decreasing from starting time to termination time. Because a displacement rate is reduced over a period of time so that kinetic velocity too decreased respectively.

     

      

CASE 2 :

        In this case, changed into 6 as an "Inacti" parameter and keep remaining things as it is.

        When we keep 6 to the "Inacti" parameter, it will remove the initial penetrations where possible. Elsewhere, reduce to less than 30% of the defined gap value and adjust the gap. In simple terms, the gap is reduced and scaled.

       

      Similarly, do the same thing as how we have done in the previous case. Select the "Radioss" sub-panel under the "Analysis" panel, save the file in the separate folder, and click the radioss button to solve the problem by solver itself.

     After calculating the model, a solver is generated different files such as the Starter listing file, Engine listing file, Animation files, Time history file and then restart file.

     If the mass error has been falling in between -15 % to -5 %, that means the mass error is an acceptable thing. In this case, the error has been falling between -5 to 1 which means results are accurate and acceptable too.

     A mass error has been zero from beginning to end, so it's an acceptable thing.

       

        After completion of solving, switch to "Hyperview" from the "HyperMesh" section.

       Select the appropriate file in an "h3d" format and open the same file in the Hyperview interface.

Contour plot for Von mises stress :

       Stress generated around 0.7 Mpa for this case.

       Seems to have the same behaviour as the previous simulation.

       

       Switch to the "HyperGraph 2d" interface instead of the "Hyper View" interface for plotting the required one.

Rigid wall forces :

       It will start from around 150, after 20 milliseconds it will start increased gradually up to 1400 afterwards rapidly return to zero at end of the simulation.

       

Contact energy:

       Initially, it's goes increased slowly, after 20 ms it goes increased highly due to defined friction between them. At end of the few milliseconds, it maintained constant force due to happened the crushing.

       

Internal energy :

       Initial energy starts from 0 and ends with around 42500 over the period of time. In the last few seconds, energy was maintained at a constant level because crushing has happened on the model.

       Internal energy is higher than the previous case because keeping the "Inacti" parameter is 6.

       

Kinetic energy :

       An initial velocity is high so kinetic velocity also is high. Over the period of time, a velocity is decreased gradually. After doing the crushing, there's no velocity at the last few milliseconds so that has been maintained at constant.

       

       

CASE 3 :

       In this case, use the same model, but change the contact interface to TYPE 11 instead of TYPE 7.

       Change into "components" instead of "set" for the Slave & master line id and define the component.

       Keep "4" as an "Istf" which means the solver will set the stiffness of the interface based on the softer of the master and solver.

       Keep "3" as an "Igap" which means the gap varies according to the characteristics of the impacted master line and impacted slave line in addition to that a gap is taken into account the size of the elements.

       Keep "2" as an "Idel" which means remove the slave nodes from contact because of element deletion.

       Keep the value "1000" as a "Stmin" which means the solver will specify the minimum stiffness in the contact to avoid soft contact.

       Keep "2" as an "Iform" which means sliding forces are computed using the stiffness of the interface.

       Keep "6" as an "Inacti", a gap is reduced and scaled. And remaining parameters are kept as it is by default.

       

       In this case, errors are falling within the acceptance range. An error is well control in this case as compared to the previous case.

       

       After completion of solving, switch to "Hyperview" from the "HyperMesh" section.

       Select the appropriate file in an "h3d" format and open the same file in the Hyperview interface.

Contour plot for Von mises stress :

       Stress generated up to 0.6414 Mpa only from zero at the beginning.

       A component starts deformation at the middle where the notch is located because there's less resistance strength on that area and also some stress flow interruption has happened.

 

       

Rigid wall resultant forces :

        A rigid wall force plot is followed by the same pattern as the previous one, but the maximum force has been reached 1600 N

       

Contact energy :

      Energy is not developed up to 7 ms, then it slightly increased & maintain constant force up to 19 ms. After 20 ms & up to 25 ms, it will linearly increase up to 1200.

      

Internal energy :

      Internal energy has started from Zero at the initial time and end up with around 45000 at the termination time.

      

Kinetic energy :

      Kinetic energy has started from around 45000 at the initial time and end up with around zero at the 25 ms and is maintained constant for the rest of the time.

      

      

CASE 4 :

      In this case, we have to remove the notched from the model using align node option which is available in HyperMesh. And also removed the boundary condition from the solver entity for this case.

      After aligning the node, a model has looked like as below.

      

      

       In this case, errors are falling within the acceptance range. An error is got as same as in the previous case, but it has taken more cycles to complete the solving.

      

       After completion of solving, switch to "Hyperview" from the "HyperMesh" section.

       Select the appropriate file in an "h3d" format and open the same file in the Hyperview interface.

Contour plot for Von mises stress :

       Stress generated up to 0.6031 Mpa only from 0.

       A component has been started deformation on the bottom because since we are removed the notch from the model.

      

Rigid wall resultant force :

      A Rigid wall force plot doesn't varied with & without notches on the component. Still, it has been followed by the same pattern and maximum force.

      

Contact energy :

      Contact energy is not varied with & without a notch on the model.

      

Internal energy :

      Internal energy is not varied with & without a notch on the model.

      

Kinetic energy :

      Kinetic energy is not varied with & without a notch on the model.

      

      

CASE 5 :

      In this case, keep the middle notch only for solving as below.

      

      It took around the same number of the cycle as the previous one. Errors also become within the acceptable value range.

       

        After completion of solving, switch to "Hyperview" from the "HyperMesh" section.

       Select the appropriate file in an "h3d" format and open the same file in the Hyperview interface.

Contour plot for Von mises stress :

       Stress generated up to 0.6607 Mpa only from zero at the beginning. Stress is a little higher in this case because we kept the notch in the middle of the model.

       A component starts deformation at the middle where the notch is located because there's less resistance strength on that area and also some stress flow interruption has happened.

 

      

Rigid wall total resultant forces :

       There's no change in the total resultant force plot if run the model is with or without the notch.

      

Contact energy :

      There's no change in the contact energy plot if run the model with or without the notch.

      

Internal energy :

      There's no change in the Internal energy plot if run the model with or without the notch.

      

Kinetic energy :

      There's no change in the Kinetic energy plot if run the model is with or without the notch.

      

      

CASE 6 :

      In this case, we have to keep a notch on the faces only like as shown below. The rest of the sides are in the same plane.

      

      In this case, errors are very close to 0 which means it's acceptable. It didn't take more cycles as compared to previous cases.

      

       After completion of solving, switch to "Hyperview" from the "HyperMesh" section.

       Select the appropriate file in an "h3d" format and open the same file in the Hyperview interface.

Contour plot for Von mises stress :

       Stress generated around 0.7 Mpa only from zero.

       A component has been starting the bending deformation at the middle on the flat side. At the end of the simulation, a model has ended up inclined in shape.

      

Rigid wall resultant forces :

     In this case, a maximum resultant force is lesser than in previous cases. Up to 15 ms, forces are varying gradually with a lesser rate. After 15 ms, forces are varying linearly up to 27 ms with a maximum value of around 1100. Then, it suddenly falls down to 0 at the termination time.

      

Contact energy :

      Contact energy also is varied as compared to previous cases. A maximum value reaches around 700 in this case.

      

Internal energy :

        There's no change in the Internal energy plot in this case.

      

Kinetic energy :

       There's no change in the Kinetic energy plot in this case.

      

 

CONCLUSION :

Cases\Parameters	Case 1	Case 2	Case 3	Case 4	Case 5	Case 6
Contact Interface Type	TYPE 7	TYPE 7	TYPE 11	TYPE 11	TYPE 11	TYPE 11
Changes on the model	No changes	Change into "Incti = 6"	Change into recommended parameters	Removed notches and boundary condition	Created a new notch in the middle.	Create a notch on opposing faces only.
Energy Errors in %	-3.8	-3.8	-1.6	-1.7	-1.6	-0.9
Maximum Stress in Mpa	0.694	0.694	0.641	0.603	0.660	0.690
Number of cycles	83500	83500	127900	132800	127600	118500
Internal Energy in J	2.0e+7	42500	42500	42500	42500	44000
Rigid wall forces in N	1.135e+5	1380	1600	1600	1500	1080
Contact forces in N	25500	44500	44500	44500	44500	44500

         

      TYPE 7 is a variable stiffness and its contact work node to surface. When we use this, it might be slave edge will penetrate across the master surface.

      TYPE 11 is also being a variable stiffness, but its contact works edge to edge. When we use this type, it will not allow penetrating across the element.

How does notch affect the results?

 

        A notch means is basically a change in the cross-section of the component. When we keep the notch in the components, by results in uneven stress distribution. When we use the notch in the component, that will lead to an increase the internal stress generation.

       In case 4, we didn't keep the notch in the component. As a result, a component experienced less stress generation as compared to all other remaining cases that have notches on it.

Why there is a change in internal energy?

      In case 1, we have used default parameters which are available in the Type 7 contact card. so, that will lead to an increase in the internal energy from the beginning time itself. Because it has a more inertial force on it. Rest of the cases, the internal energy is lesser than the previous one because we kept the parameter as recommended one.