Assignment 6-Frontal Crash Simulation Challenge

Frontal Crash Simulation:

Aim: To Perform The Crash Simulation On the Frontal Section Of The Car To Study How The Impact Forces Are Distributed Through The Structure To Prevent Damage To The Occupants.

Objective :

• Check Unit System And Either Follow[Mg Mm S] Or [Kg Mm Ms].
• Create Appropriate Interface, Friction 0.2 And Recommended Parameters.
• Make Sure Of No Penetrations And Intersection.
• Correct Rigid Bodies If Any Issues.
• Create Rigid Wall With Friction 0.1.
• Compare The Model Weight With The Full-Scale 300k Nodes Model And Use Added Masses To Reach Target Weight 700kg While Getting CG About The Required Range.
• Initial Velocity 35 Mph.
• Use Model Checker To Ensure Good Quality.
• Time-Step :0.5 To 0.1 Microseconds.
• Run 80 Ms.

Output Requests:

• Sectional Force In The Rails At Location Of Indicated Node 174247.
• Axial Force Received On The Rails From Bumper.
• Shotgun Cross-Sectional Forces.
• A-Pillar Cross Section.
• Acceleration Curve Received On The Accelerometer At Base Of B Pillar (On B Pillar Rocker).
• Intrusions On The Dash Wall 66695,66244

Procedure:

Objective 1:

Checking  The Unit System And Following [Kg Mm Ms ].

Step 1 _ Open The Starter File Neon_Front_000.Rad File , Goto Menu Bar >> File >>Import >> Solver Deck >> Select .Rad File >> Import .

Step 2_ Checking Unit System Of The Model And Set To [Kg Mm Ms ]  This Can Be Done As Shown Below.

Model Browser >> Cards >> Begin_Card >> Change The Units In Kg  ,Mm ,Ms

Objective 2 : Creating Appropriate Interfaces , Friction 0.2 And Recommended Parameters .

Model Browser >> Group >> Create Group Card As Type 7 Interface (Select Grnod_Id And Surf_Id By Component, This Selects Nodes As Slave And Surface As Master .) 

Input All The Necessary Parameters In This Card As Shown Below.

Objective 3: Making Sure Of There Should Be No Penetration  And Intersections

In Manu bar >> Tool >> Penetration Check >> Select Entity Type As Component >> In Selection Select All The Components As Shown In Second Image >> And Click On Checks

Objective 4: To Correct Rigid Bodies If Any Issues.

To Check Conenctivity  Goto Tools>>Find Conectivity >> Select Components >> Check  As Shown Below

Objective 5 _ To Create Rigid Wall With Friction 0.1

To Create A Rigid Wall Goto Solver Browser >>Right Click >> Create >> Rwall >> Plane

After Crating Rwall We Have To Defined Rwall Cards Parameters For Geometry Type – Infinite Plane In Engineering Data We Have To Specify Its Co-Ordinates Which We Can Select By Single Node By Clicking On Rightward Direction As Shown Below.

Other Properties Are As Below Picture

Objective 6: To Compare The Model Wight With Full Scal 300k Nodes Model And Use Added Masses To Reach Target Weight 700 Kg While Getting CG About Required Range

First We Have To Know About Mass Of Model That Is How Much Mass The Model Currently Holds To Know This Goto To>> Mass Details  >>  Mass Cog Inertia

Here The Model Has Some Mass Of Around 288 Kg Already Assign To It , Now We Have To Add Some Mass To This Model So That This Model Reach To 700 Kg And We Can Get Cog Of The Model To Appropriate Location

Similarly, We Can Know the Cog Location Of The Model By Clicking COG Window Near The Mass Window Shows Co-Ordinate Of The Current Cog Of The Model  By These Co-Ordinate We Can Create A Node From Geometry >> Node

After Checking This  We Can Add Mass In The Model From Solver >> Create >> Admas

Select Mass Type  As Mass Added At Each Node Of The Node Group. And Select Appropriate Node On Logical Position.

After Adding The Mass,  Check The Mass Details And Cog Location Again And Confirm Whether They Are In Acceptable Range Or Not

After Adding Mass Cog And Mass Location Can Be Seen As In Below Picture

Objective 7: Initial Velocity Of 35 Mph

To Apply Initial Velocity Of 35 Mph We Need To First Change Its Units As We Are Using Kg Mm Ms Unit System, To Know About Its Equivalent Value In mm/ms We Have Used Consistent Unit Data As Below.

Now That We Know Its Equvivalent Value We Have To Create INVEL  Card  , To Create It Go To Solver Deck >> Right  Click >> Create >>Boundary Conditions>>Invel

This Card Has To Be Filled As Below Images

Objective 8: Use Model Checker To Ensure Good Quality

Model Checker Can Be Found In Tool >> Model Checker >>Radioss Block>> After This Run This By Clicking On Highlighted Option 

In This Model We Only Found Warnings And There Are No Errors So We Can Run This Model

Objective 9:

Make Time Step 0.5 To 0.1 Micro Second

Go To Model Browser >> Cards >>ENG_ANIM_DT>>Tfreq= 5.0

Objective 10: Run The Model With 80 Ms

Model Browser >>Cards >>ENG_RUN >>Tstop = 80.

Output Request

To Perform Output Request We Have To Follow The Procedure That Is For  Sectional Force Output Request We Need Section To Be Created And For Section We Need Frame 

Axial Force Received On The Rails From The Bumper

Here We Have To Find Forces Passing Through Rails From Bumper To Do So We Need To Create An Output Request

Procedure :

First We Have To Isolate The Part In Concern To Do So Press D On Key Board It Will Open Display Panel On Screen

Now Click On The Component Which Is  To Be Isolated , In This Case We Are Concerned With Rails From The Bumper

After Selecting The Component It Gets Vanished 

Once It Is Vanished Click On Reverse , It Will Show Our Isolated Component.  

Now We Can Move To Create Frame For Sectional Force To Do That Goto Solver Browser >> Create >> Frame >> Mov .

A Frame Panel Will Appear In That We Have To Chose Three Nodes To Define Frame These Three Nodes Will Be Origin , Node For X From Origin & Third Node To Define Xy Plane .

Once Nodes Are Selected Click On Create , And Frame Will Be Created As Below

After Frame Has Been Done We Can We Have To Create Cross Section For That Go To Solver Browser Create >> Sect >> Sect

This Will Brought A Cross Section Property Section ,Here We Have To Select Nodes For Cross Section To Do So Select NODE Respective To N1,N2,N3 >> In Sub Panel Click On Node And Pick Node For Respective Node >> Proceed

Now Select Frame For Property For That Click On SYSTEM Near FRAME >> In Sub Panel Click On SYSTEM >> Pick The Frame For System>> Proceed. 

Frame Will Be For Reference Of The Section

After This System Will Appear As Below

For Property We Also Need To Define Element For That We Will Use Grshell Ids . To Define Grshell Id We Have To Create One To Do So Right Click On Grshell Id >> Create. It Will Open An Window For Gr Shell Property .

In This Property Card We Have To Select Some Element Which Is To Be Come In Gr Shell Id ,After Selection Click On Proceed .

Note: Select The Element Where You Want To Find Forces And And For Approximation Purpose Select One Or Two Rows Around It 

This Will Complete Our Cross Section Definition

Now That Cross Section Has Been Defined We Can Go To  Output Request For Force Through The Section . This Can Be Done By Right Clicking The Output Block >> Create New Block >> And In Entity Block Select Cross Section.

Here Select The Cross Sections We Have Created  Earlier And Click On Ok

To See Our Output Request We Can Do Right Click On Output Card And Click On Review It Will Show Our Output Elements

Similar To This We Have To Create Output Request In The Rails At Location Of Indicated Node 174247 To Find The Location Of This Node Click On Display Number

In Nodes Selection Select Nodes By Id And In Id Enter The Id As 174247 ,Enter And Click On It Will Display The Location Of The Node

The Location Of The Node Is Displayed In Below Picture.

Now Create Frame , Section And Output Request At This At This Location 

The Task We Have Include To Make Force Section In Both The Rails Left And Right , On Both Sides Of Rails From Bumper , Both Shotgun/Fender  And  Both A Pillar

The Sections We Have Created Are As Shown Below

Nest Task Is To Create Accelerometer At The Base Of Of B Pillar , To Do This  Go To Model Browser >> Right Click >> Create >> Accelerometer >> And In Card Node Id = Select Node On The Base Of The B Pillar

Create This Accelerometer On Both Side Of Car And Also Make Output Request

To Make Output Request For Accelerometer In Entity Instead Of Cross Section Select Accelerometer This Can Be Done By Doing Right Click On Entity Id And Choosing Accelerometer ,And Finally Select One Of The Accelerometer Which Were Created Earlier Individually

Create Intrusions On The Dash Wall At Location  66695,66244 And Make Out Output Request

To Create We First Need To Display The Nodes 66695 , 66244 Location After That We Have To Create New Component From Model Browser ,Name This Component As Spring And Give This  Component Properties As Shown Below

Once Component Is Been Created Make This Component As Current After This We Have To Create Spring Element And Assign This Component To New Spring Element

Run The Analysis :

Analysis >> Radioss >> Input File : (File Location)-Save As >> Check The Include Connectors>>Option: -Nt 4>> Hit Radioss.

Note : While Running The File First Time We Have Face Problems As We Didn’t Get .H3d File ,To Solve  This Issue We Have Check Wether Out ENG_ANIME_DT  File Is Correctly Defined Or Not , We Didn’t Find Any Issue In That , Then Deleted This ENG_ANIME_DT Card And Create New One With Tfreq = 5,

To Create New ENG_ANIME_DT   Card Go To Tools While In You Are In Model Browser >> And Do As Picture Shown Below.

Review The Simulation 

We Have To Import The Animation File In Hyperview

Hyperview>>First_Run.H3d>> Appy

The Tool To Review The Simulation Are Available On Hyperview

Hyperview Is A Post-Processing And Visualization Environment For FEA That Gives The Output Of Analysis In The Simulations Format That Is User Friendly To Understand

From The Simulation ,We Can Review How The Impact Force Acts And Cause Deformation And Point Of Rupture On The Model.

After This Model Will Be Appear In The Hyperview Environment

After This It Will Show The Animation Of The Simulation As Below

From The Simulation, We Can See That .Initially The Bumper Starts Crushing Then The Bumper Forces Are Transferred To The Left And Right Rail From The Rail, Forces Are Transferred To A Pillar LH &RH , In Each Stage The Forces Are Going To Reduce Because Energy Is Absorbed In Each Stage, Because Of No Engine Block , Suspension System Etc . The Car BIW Is Going Down At The End Of The Simulation.

Results After Simulation :

At The End Of The Simulation, We Do The Energy Error And Mass Error Check And Determine Whether Results Would Be Acceptable Or Not.

Open The Save Location File And Click On Output File Of The Simulation To Check For The Energy Error And Mass Error

If The Error Is Negative , It Means That Some Energy Has Been Dissipated

In The Case Of Under Integrated Elements (Belyschko Shell , Solid With 1 Integration Point ), Hourglass Energy Can 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 The Case Of Using QEPH Shell Formulation Or Fully Integrated Element 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 % Will Be Acceptable

In The Case Of A Larger Positive Energy , The Source Of This Energy Has To Be Identified. Incompatible Kinematic Conditions Can Lead To Such Situation .

After Simulation

Check The Starter Output File For Errors :

A Starter Output File Of .Out Format Is Generated After Analysis.

The Output File Contains The Data During Simulation , Such As Cycle ,Timestep , Energies And Error

We Have To Check For Energy And The Mass Error Which Means That The Solver Did Not Need To Add  Mass Onto The Nodes To Reduce The Timestep To Further Avoid The Hourglass Error.

Observation :

The Energy Error Is Negative And Has Been Linearly Increasing Upto  -1.2% Only Which Is Acceptable.

Mass Error Is 0.3524 X 10^-1 Which Is Acceptable

We Can Conclude That There Are No Errors In The Analysis 

PLOT THE GRAPH & COMPARE THE RESULTS

HYPERGRAPH 2D >>DATA FILE : T01 FILE  >>CHOOSE THE GRAPH WHICH YOU WANT AS SHOWN IN BELOW PICTURE >> APPLY

First Plot Internal , Kinetic ,Contact & Total Energies

The Ininternal Energy And Kinematic Energy :

Internal Energy Is Nothing But The Heat Of The System And Energy That Component Has Absorbed . When The Kinematic Energy Is Decreases , The Energy Absorbed By The System Increases I.E We All Know That Energy Nirtether Be Created Nor Be Destroyed . Once The Vehicle Is Moving With Certain Velocity (15.646 Mm/Ms For The Model ),The Initial Kinetic Energy Will Be High (Refer To Above Graph ). Once The Car Is Hit By The Rigid Wall , The Vehice Starts Deforming Results In Absorbing The Energy And Stored It . Thus ,Internal Energy Starts Increasing At The Maximum Deformation, The Velocity Will Become Zero And Thus The Kinetic Energy Will Also Be Dropping Down To Zero Resulting There Is No Energy To Absorb In The  System . Thus , The Internal Energy Remains Constant Therafter

Once After The Simulation , The Maximum Kinetic Energy Is Found At T=0 Ms Is 86729.5 Kn/Mm And Minimum  At T=79.5 Ms Is 42960.59kn/Mm

For Internal Energy  At T=0 Ms Is 0 Kn /Mm And At T=79.5 Ms Is 41529.50 Kn/Mm

Contact Energy And Hourglass Energy

From The Above Graph ,We Can See That The Hourglass Energy Is Almost Negligible Since We Have Used Improved Integrated Element Formation (Qeph)

Ideally, All Of Ke Should Be Converted Into Ie And The Total Energy Must Remain Constant, But In Our Case, Since We Have Hourglass Energy Error, Our Total Energy Is Decreasing. We Can Rectify This Hourglass Energy By Further Reducing The Timestep Of The Simulation And Giving The Ideal Properties Wherever We Can. Our Requirement From An Ideal Simulation Is That We Have Minimal Contact Energy And Maximum Energy Absorption/Deformation In The Elements. We Can Check The Energy Error In The Engine Output File, Which Has Maxed Out At -1.2 % Which Is Within The Limits For It To Be. Our Mass Error Is Also 0% Which Means That The Solver Did Not Need To Add Mass Onto The Nodes To Reduce The Timestep To Further Avoid The Hourglass Error.

Contact Energy Is Nothing But The Opposite Energy Generated From The System To Avoid Penetration. To Avoid Penetration, We Have Determined The Gap Min Value To 0.5. When The Car Is Moving With A Velocity Of 35mph And Hits The Rigid Wall, It Starts Deformation At The Bumper Section And Hence The Penetration Of The Elements Occurs And Thus The Opposite Reaction Force Also Exerted In Order To Avoid The Penetration. Hence The Contact Energy Increasing Gradually From Zero. The Maximum Contact Energy Found Is 1638.72

1638.72 Kn/Mm At T-79.5ms.

SECTIONAL FORCES

1.ON RAILS

The Maximum Cross-Sectional Force At Left Rail Is 5.616 Kn/Mm At T= 37.5ms Whereas The Maximum Cross-Sectional Force At The Right Rail Is 4.93 Kn/Mm At T=11.50 Ms. The Force Acting On The Rail Is The Force Transmitted By The Bumper During The Crash. The Force Transmitted By The Bumper To The Rail Can Be Unequal Due To Which The Force Received At The LH Rail May Differ From The RH Rail. During A Crash, The Rail Will Get Into Direct Contact With The Rigid Wall Which Will Increase The Compressive Force And Then Deform. Therefore, The Compressive Force Drops Down.

On Shotgun/Fender :

The Maximum Cross-Sectional Force At Left Shotgun Is 0.85047 Kn/Mm At T-68.50 Ms Whereas The Maximum Cross-Sectional Force At Right Shotgun Is 0.3439 Kn/Mm At T-65ms. The Force That Occurred At The Shotgun Is The Force Transmitted From The Rail Section. The Force Propagation Is Not The Same At Both The Rails And Hence The Amount Of Deformation At Both The Shotgun Sections Are Different. Once The Compressive Force Reaches Its Maximum Value It Starts To Deform Rapidly. Therefore, The Compressive Force Is Decreasing As Referred From The Graph. As The Crash Happen Continuously, The Shotgun Will Come Into Contact With The Rigid Wall As Found In Animation, The Rigid Wall Also Exerts The Force Directly On To The Shotguns And Hence There Is An Increase In The LH  Sectional Force As Seen In The Graph.

A Pillar:

The Maximum Cross-Sectional Force At Left A-Pillar Is 2.635 Kn/Mm At T= 72 Ms Whereas The Maximum Cross-Sectional Force At Right A-Pillar Is 2.335 Kn/Mm At T-27.5 When The Car Hits The Rigid Wall, There Will Be Some Amount Of Force Coming Into The A-Pillar At Both Sides. These Forces Coming To The A-Pillar Are Nothing But The Force Transmitted From The Rail And The Shotgun. The Force Flowing Into The LH And RH Of The A-Pillars Will Not Be Equal And Hence The Deformation Of The Elements Will Differ Accordingly. During A Frontal Crash, The Sectional Force Reaching The A-Pillars Are Coming In From The Rails And Shotgun, Hence The Force At The A-Pillars Will Be Less When Compared To The Front Sections. When The Compressive Force Between The Wall And Car Is Maximum, The Rail And Shotgun Get In Contact With The Rigid Wall Which Causes The Shotgun And Rail To Exert More Force. This Force Then Propagates To The A-Pillars And Hence The Force Reaching The A-Pillar Increases Again.

Intrusion Spring :

To Check The Intrusion At The Dash Wall At The Particularly Given Node, We Have Created The Spring Over The Place. The Intrusion At This Particular Node Calculated In Order To Check Whether The Crash Will Result In The Safety Of The Driver Due To The Deformation That Occurred At The Front Portion Of The Vehicle. From The Above Graph, We Can See That The Maximum Intrusion Occurred In The Spring (Node 66695,121754) During A Crash Is 7.66 Mm And The Maximum Intrusion Occurred In The Spring (Node 66244,121868) During A Crash Is 5.40 Mm. Practically This Elongation Referred To Which Extent The Foot Pedal Or The Passenger's Legs Will Move Once The Crash Is Happening. From The Animation, We Can Notice That There Is Not Much Deformation That Occurred At This Location And The Elongation Is Also Low. Hence, We Can Conclude That There Are Fewer Injuries Will Happen To The Passenger/Driver.

Accelerometer

As We All Know That An Acceleration Is The Rate Of Change Of Velocity. To Measure The Acceleration, We Have Placed The Accelerometer Near The Rocker Of B-Pillar On Both Sides, From Graph We Can See That Acceleration Is High Initially After That It Is Almost Zero

Maximum Acceleration At LH = 339.26 Mm/Ms2 At T=0.5ms

Maximum Acceleration At RH = 208.844 Mm/Ms2 At T=0.5ms

Axial Forces On Rail Of Bumper:

From The Graph, We Can See That Initially There Is No Axial Force Is Transmitted From The Bumper To The Rail. Once The Vehicle Hits The Rigid Wall, First The Bumper Will Start Deforming Transmitting The Strain Energy To The Rail Sections. From The Graph, We Found That The Maximum Axial Force Received From The Bumper To The LH Rail Is 9.25 Kn At 14 Ms And The Maximum Axial Force Received From The Bumper To The RH Rail Is 6.56 Kn At 16.5 Ms.

Conclusion:

The Given Model Was Simulated For The Frontal Crash Using Radioss And The Results Obtained Were Validated. The Graphical Results Were Plotted For All The Test Cases. From