finite element method final project “ rear suspension- double a- arms”
DESCRIPTION
Finite Element Method Final Project “ Rear Suspension- Double A- Arms”. Jaime Taha T.April 29 th 2003. Mini Baja. Competition takes place on a motor cross track. Suspension must React and perform well. Protect the driver from impacts from the rough terrain. - PowerPoint PPT PresentationTRANSCRIPT
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Finite Element Finite Element MethodMethod
Final ProjectFinal Project“ Rear “ Rear
Suspension-Suspension-Double A- Arms”Double A- Arms”
Jaime Taha T.Jaime Taha T. April 29April 29thth 20032003
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Mini Baja Mini Baja Competition takes place on a motor cross Competition takes place on a motor cross
track.track. Suspension must Suspension must
React and perform well.React and perform well. Protect the driver from impacts from the rough terrain.Protect the driver from impacts from the rough terrain. Be strong enough to survive the trackBe strong enough to survive the track
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More pictures.More pictures.
As we can see, is very As we can see, is very feasible feasible that the cars that the cars could be hit by another one, or that the tires could be hit by another one, or that the tires could hit a rock, bumps, etc. could hit a rock, bumps, etc.
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Problem StatementProblem Statement The Rear Suspension of the Mini Baja car The Rear Suspension of the Mini Baja car
must be able to withstand the rough must be able to withstand the rough terrains associated with the competition’s terrains associated with the competition’s motor cross track. motor cross track.
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Problem StatementProblem Statement The Rear Arm Suspension consist of 3 parts: Top The Rear Arm Suspension consist of 3 parts: Top
Arm, Bottom Arm, and a Hub. Arm, Bottom Arm, and a Hub. Using the material properties for 4130 Chromoly Using the material properties for 4130 Chromoly
Steel.Steel. The tubing is a 1” diameter and 0.058” thickness.The tubing is a 1” diameter and 0.058” thickness. In this project the Top arm was analyzed.In this project the Top arm was analyzed.
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FEA AnalysisFEA Analysis 3 Scenarios were analyzed (Worst Case 3 Scenarios were analyzed (Worst Case
scenarios)scenarios) Arm MovingArm Moving Tire hits a rock, wood, bump, etc.Tire hits a rock, wood, bump, etc. Tire hit from the sideTire hit from the side
F=820 lbf2 & 3 Scenarios
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Impact ForceImpact Force This force is applied in the second and This force is applied in the second and
third scenarios where:third scenarios where: Another car traveling at 30 MPH hits our car Another car traveling at 30 MPH hits our car
and comes to rest at one second and comes to rest at one second The car hits an object traveling at 30 MPHThe car hits an object traveling at 30 MPH
VVii=30 MPH, V=30 MPH, Vff=0 MPH, Time (t) = 1 =0 MPH, Time (t) = 1 second, Mass (m) = 600 lb second, Mass (m) = 600 lb
lbfF
impactamFt
VVimpacta
taVV
if
if
820
)(
)(
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Forces acting in the Forces acting in the systemsystem
Reaction force of the weight of the structure acting on both arms
Weight of the car, acting on both arms
Stress of the Spring/Damper forceonly on the Top Arm
Car Frame
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Pro E ModelPro E Model
Top Arm
Spherical JointsSpring/Damper
Spring Force = 175 lb/inDamper Force (C) = 10.2 Lbf
Impact Force
= 820 lbf
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AssumptionsAssumptions Welded zones where neglectedWelded zones where neglected The actuator in the tire simulates the displacement of The actuator in the tire simulates the displacement of
the tire-arm when the car is driven.the tire-arm when the car is driven. The spring-dash is acting in the as a distributed load The spring-dash is acting in the as a distributed load
(Pro E model image.)(Pro E model image.) Spherical joints were used where the arm is attached Spherical joints were used where the arm is attached
to the car’s structure, also the car frame was to the car’s structure, also the car frame was assumed that doesn’t move (Car’s frame doesn’t take assumed that doesn’t move (Car’s frame doesn’t take any load.)any load.)
To simulate the impacts in the car, a ramp function To simulate the impacts in the car, a ramp function was used.was used.
The reaction force of the tire is calculated as a worse The reaction force of the tire is calculated as a worse case scenario where all the weight of the car is case scenario where all the weight of the car is applied only in one tire applied only in one tire 600 lb, as a distributed 600 lb, as a distributed force.force.
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Finite Element ModelingFinite Element Modeling Scenario 1 – Arm moving.Scenario 1 – Arm moving.
Stress Analysis 0.03ftMax. Value = 7.46e8
Value in a specific point = 6.03e8 Pa
Stress Analysis 0.02ftMax. Value = 8.6 e8
Value in a specific point = 7.03e8 Pa
Stress AnalysisStress Analysis
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Finite Element ModelingFinite Element Modeling Scenario 1 – Arm moving.Scenario 1 – Arm moving.
Factor of SafetyFactor of Safety
FS-0.03 - Front (above) and Back (below) views of Factor of Safety (Mesh size of 0.03 ft)FS-0.02 - Front (above) and Back (below) views of Factor of Safety (Mesh size of 0.02 ft)
FS-0.03 FS-0.02
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Finite Element ModelingFinite Element Modeling Scenario 2 – Tire hits a rock, wood, Scenario 2 – Tire hits a rock, wood,
bump, etc.bump, etc. Using 0.02 ft. MeshUsing 0.02 ft. Mesh
Max. Value = 8.62e8 Pa Value in a specific point = 6.71e8 Pa
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Finite Element ModelingFinite Element Modeling Scenario 2 – Tire hits a rock, wood, Scenario 2 – Tire hits a rock, wood,
bump, etc.bump, etc. Using 0.03 ft. MeshUsing 0.03 ft. Mesh
Max. Value = 7.68e8 Pa Value in a specific point = 4.66e8 Pa
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Finite Element ModelingFinite Element Modeling Scenario 2 – Tire hits a rock, wood, Scenario 2 – Tire hits a rock, wood,
bump, etc.bump, etc. Using 0.04 ft. Using 0.04 ft.
MeshMesh
Max. Value = 1.42e9 Pa Value in a specific point = 1.12e9 Pa
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Factor of SafetyFactor of Safety
Finite Element ModelingFinite Element Modeling Scenario 2 – Tire hits a rock, wood, Scenario 2 – Tire hits a rock, wood,
bump, etc.bump, etc.
FS – 0.02ft FS – 0.03ft
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Simulation of stress analysis in the Simulation of stress analysis in the tire-arm with movement tire-arm with movement
Finite Element ModelingFinite Element Modeling Scenario 2 – Tire hits a rock, wood, Scenario 2 – Tire hits a rock, wood,
bump, etc.bump, etc.
Change in stresses when object moves Movement and stresses
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Finite Element ModelingFinite Element Modeling Scenario 3 – Tire hit from the side.Scenario 3 – Tire hit from the side.
Using 0.03 ft. MeshUsing 0.03 ft. Mesh
Max. Value = 6.7e8 Pa Value in a specific point = 5.06e8 Pa
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Finite Element ModelingFinite Element Modeling Scenario 3 – Tire hit from the side.Scenario 3 – Tire hit from the side.
Using 0.02 ft. MeshUsing 0.02 ft. Mesh
Max. Value = 1.27e9 Pa Value in a specific point = 8.25e8 Pa
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Finite Element ModelingFinite Element Modeling Scenario 3 – Tire hit from the side.Scenario 3 – Tire hit from the side.
Change in stresses when object moves Movement and stresses
Simulation of stress analysis in the Simulation of stress analysis in the tire-arm with movement tire-arm with movement
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Improvement - Pro E Improvement - Pro E Drawings.Drawings.
Previous
Adding the pipe showed, the stresses Adding the pipe showed, the stresses concentration could be distributed.concentration could be distributed.
Possible Alternative
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……Cont’Cont’ Comparing the 1Comparing the 1stst case scenario: case scenario:
The addition of the pipe decreases the stresses The addition of the pipe decreases the stresses and also distribute the stress concentrationand also distribute the stress concentration
Stress Analysis 0.03ftMax. Value = 7.46e8 Pa
Value in a specific point = 6.03e8 Pa
Stress Analysis 0.03ftMax. Value = 1.4e8 Pa
Value in a specific point1 = 2.9e7 PaValue in a specific point2 = 1.1e8 Pa
Point2
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Finite Element ModelingFinite Element Modeling Scenario 1 – Arm moving.Scenario 1 – Arm moving.
As explained before, with the addition of the pipe, the stress As explained before, with the addition of the pipe, the stress concentration decrease and also was distributed (Mesh size concentration decrease and also was distributed (Mesh size 0.03 ft). An increase is notable in the new model (right image) 0.03 ft). An increase is notable in the new model (right image) in the Factor of Safety from 0.54 to 3.46.in the Factor of Safety from 0.54 to 3.46.
Actual part Modify part (addition of a pipe)
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Finite Element ModelingFinite Element Modeling Scenario 3 – Tire hit from the side.Scenario 3 – Tire hit from the side.
In this scenario, the addition of the pipe also affect the factor In this scenario, the addition of the pipe also affect the factor of safety, as we can see the red zones from the figures.of safety, as we can see the red zones from the figures.
Actual part Modify part (addition of a pipe)
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Problems/Comments Problems/Comments while doing my project.while doing my project.
Pro EPro E DrawingsDrawings Cut the inside of the pipesCut the inside of the pipes Verify unitsVerify units Geometry settings/connection to Visual Geometry settings/connection to Visual
Nastran (Why doesn’t work???)Nastran (Why doesn’t work???)
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Problems/Comments Problems/Comments while doing my project.while doing my project.
Visual Nastran Visual Nastran Meshing the part – “play” with the mesh size.Meshing the part – “play” with the mesh size. The use of H-Adaptivity is hard to run it The use of H-Adaptivity is hard to run it
because thin structure and other elements because thin structure and other elements (such as spring, actuator, etc)(such as spring, actuator, etc)
Verify the restraints, forces, springs, actuators, Verify the restraints, forces, springs, actuators, motor, etc.motor, etc.
Verify Joints (also is very important to verify the Verify Joints (also is very important to verify the dynamic loadings)dynamic loadings)
While running the FEA with motion there’s no While running the FEA with motion there’s no way to stop it.way to stop it.
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CommentsComments 3 scenarios were analyzed 3 scenarios were analyzed H-Adaptivity was not used because of the H-Adaptivity was not used because of the
complexity of the part and the thickness.complexity of the part and the thickness. A possible alternative of adding a pipe between A possible alternative of adding a pipe between
the arms with the purpose of decrease stress the arms with the purpose of decrease stress concentration and also distribute the load. In concentration and also distribute the load. In fact the results showed that by adding the fact the results showed that by adding the pipe, the stresses slightly reducepipe, the stresses slightly reduce
FEA is a time consuming process, it can be FEA is a time consuming process, it can be improve if the analysis is run on a more improve if the analysis is run on a more capable computers.capable computers.
Further work: Further work: Verify the pipes diameter/thickness and do FEAVerify the pipes diameter/thickness and do FEA
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Dr. Arturo Fuentes Dr. Arturo Fuentes
Mini Baja TeamMini Baja Team
ClassmatesClassmates
AcknowledgemAcknowledgementsents