Comparison of results with base simulation and improved properties

Comparison of results with base simulation and improved properties

For Details Click on link.............>>>>>>>https://drive.google.com/file/d/1eNk3RA-VvseX8nH4PgY2eI8S290ewLPK/view?usp=sharing

OBJECTIVES

1. To Change the run time and animation steps and during the simulation.
2. To assign recommended shell properties for crash analysis.
3. To change the run time and shell properties compare the two different results.
4. To plot the different graphs as internal energy, kinetic energy, hourglass energy, etc.
5. To study energy error and shell formulation of elements

CASE 1 SETUP AND PROCEDURE

• Import the engine input file (runname_0000.rad) from the import tab in a solver deck.
• It will appear in wireframe mode.
• 
• Click on shaded mesh to view the mesh in shaded form
• 
• Now click on the analysis tab and select as Radioss as a solver.
• 
• Give the input file destination as the solvers create a lot of instantaneous files, so better to save the files in a specific folder.
• The export option should be all – it will take all the components hidden too.
• Number of the run as 1 and Run option as analysis
• Options should be (-nt 4 means four CPU solves problems at a time)
• Click on the shaded mesh to view the mesh in shaded form.
• After completion of Radioss analysis, you will get the result card.
• 
• Now change the mode from hyper mesh to hyper view
• Load the model of files created folder the file should be in form of .h3d
• .h3d file is a animation file which is combined file of animation files( A01, A02, A03….)
• 
• We can change the visualization of the different elements.
• Click on preferences and click on visualization and change the 1D elements to dot.
• The size of the marks can be modified accordingly.
• 
• Click on the contours option to get the different required result values of stress, displacement,hourglass energy etc
• 
• The dynamic max-min result can be calculated as follow.
  • If you want to plot different graphs. Change the mode to hypergraph 2D.
  • Hypergraph can be accessed with the file name with format(runname_T01). This file format should be in runname_T01
  • Here choose the global variable for different energy graphs such as internal, Kinetic energy, Hour glass energy etc.
  • Select the different entities which you want to plot and use the snipping tool for reports.

•  

  • Here choose the global variable for different energy graphs such as internal, Kinetic energy, Hourglass energy,etc.
  • Select the different entities which you want to plot and use the snipping tool for reports.

                                                                           

•  

   

• 
• 

•  

  CASE 2 SETUP AND PROCEDURE

  • Import the engine input file (runname_0000.rad) from import tab in a solver deck.
  • It will appear in wireframe mode.
•  
  • Click on shaded mesh to view the mesh in shaded form
•  
  • For 2^nd case we are applying shell properties as mentioned below
  • The choice of shell element properties depends on integration type and relative cost.
  • Depend on this we mostly choose QEPH with Ishell Value 24. It will give economic method with good accuracy.
  • Applying these properties we can control accuracy of and time required for simulation.

   

•  

  • 
  • 
  • Now click on analysis tab and select as Radioss as a solver.

   

  • Give the input file destination as the solvers create lot of instantaneous files, so better to save the files in a specific folder.
  • Export option should be all – it will take the all the components hidden too.
  • Number of run as 1 and Run option as analysis
  • Options should be (-nt 4 means four CPU solves problems at a time)
  • Click on shaded mesh to view the mesh in shaded form.
  • After completion of Radioss analysis you will get result card.
•  
  • Now change the mode from hyper mesh to hyper view
  • Load the model of files created folder the file should be in form of .h3d
  • .h3d file is a animation file which is combined file of animation files( A01, A02, A03….)
  • 
  • We can change the visualization of the different elements.
  • Click on preferences and click on visualization and change the 1D elements to dot.
  • Size of marks can be modified accordingly.
  • 
  • Click on the contours option to get the different required result values of stress, displacement,hourglass energy etc
  • 
  • Dynamic max min result can be calculated as follow.
  • 
  • If you want to plot different graphs. Change the mode to hypergraph 2D.
  • Hypergraph can be accessed with the file name with format(runname_T01). This file format should be in runname_T01
  • 
  • Here choose the global variable for different energy graphs such as internal, Kinetic energy, Hour glass energy etc.
  • Select the different entities which you want to plot and use the snipping tool for reports.
  • 
  • 
  • 
  • 
  • 

   

•  

        

   

• HOURGLASS ENERGY AND MODES

  • Hourglass modes are nonphysical mode of deformation that occurs in under integrated elements and produce no stress.

  -solid elements with a single integration point

  -Shell elements with a single in-plane integration point

  • Reduced integration can lead to non-physical zero-energy modes, called hourglass modes.
  • There are two methods used to control the formulation of hour glassing:

  - Perturbation (Q4 Elements)

  - Physical Stabilization (QEPH Elements)

   

  Perturbation (Q4 Elements) ->Viscous method- damping is applied -> Due to damping deformation is stabilized -> that tries to control the velocities only ->Hour glass is an artificial energy. This method is used for very high-velocity problems such as explosive or bullet fire (100-1000m/s)

  Physical Stabilization (QEPH Elements) -> Stiffness method -> Stiffness is added to material level so it may consistent. -> most of the time this method is preferred for analysis purpose.

  Energy Error

  • The result reliability is strongly affected by the energy error percentage; if the error is negative it means some energy has been dissipated while it positive there is energy.
  • Considering radioss explicit solver the energy error percentage depends on translational, rotational kinetic energy, internal energy, work of external forces and energy at the beginning of the run.
  • In the case of using QEPH shell formulation or fully integrated elements the energy error percentage can be slightly positive since no hourglass is involved and its computation is much more accurate (%E= 1%-2%). In case of more important positive energy, the source of energy must be identified as related to incompatible kinematic conditions.
  • The energy error must be negative and decreasing (except for the first cycle or in spring backstage). The real must be less than 15% at the end of the consumption (5% for good model). If the air increases a little then decreases may be normal. If the error increases this means that a problem has occurred. Then the error may grow to 99.9% with computation send your message.
  • So ideally the error should be at most -15% and better to have -5%. The closer to zero percent error is better.
  • QEPH cell formation for 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 one or two percent will be acceptable otherwise any positive energy error means energy has been created which indicates a model issue.

   

   

  CONCLUSION:

  1. There are two different types of radioss files namely engine file (runname_0001.rad) and starter file (runname_0000.rad).
  2. Learn about how to change the run time during simulations using various types of radioss files.
  3. The use of different shell properties and its use. Creation of property cards of different shell elements.
  4. We can use different shell element formulation methods based on integration quality and relative cost. Based on this we can choose QEPH elements for IMPROVED UNDER INTEGRATION. This method gives physical stabilization for hourglass energy control.
  5. When we choose shell element formulation as QEPH element the hourglass energy remains close to zero whereas when we are not using initial properties the hourglass energy increases drastically which will lead to a considerable % energy error.
  6. The result reliability is strongly affected by the energy error percentage; if the error is negative it means some energy has been dissipated while it positive there is energy.
  7. QEPH cell formation for fully integrated elements the energy error can be slightly positive since there is no hourglass energy and the computation is much more accurate.
  8. An error of one or two percent will be acceptable otherwise any positive energy error means energy has been created which indicates a model issue

   

• For Details Click on link.............>>>>>>>https://drive.google.com/file/d/1eNk3RA-VvseX8nH4PgY2eI8S290ewLPK/view?usp=sharing