Structural Compliance of Electric Vehicle Battery Pack
FCA Intern Presentation
1. July 29, 2015
Kendall Moore
Vehicle Integration & Validation
Durability & Development Operations
Graduating May 2016
Mechanical Engineering
2. Kendall Moore
Hometown: Newport News, Virginia
Rising 5th year, Virginia Commonwealth University,
Richmond, VA
Degree: Mechanical Engineering, minors in
Math & Physics
RA & Extracurricular Involvement (social justice,
cultural, leadership/honor)
Interests: outdoor activities, live music, Game of
Thrones
Professional Experience
07/29/2015 2
3. Opportunities
CPG Ride and Drive
FCA Intern Social Events Walter P. Chrysler Museum
Mack Engine Plant Tour Cultural immersion Day
Road Test Simulation Lab Mechanical Life Testing Lab
Data Acquisition at Chelsea Proving Grounds
07/29/2015 3
4. 407/29/2015
Background
Resistance Spot Welds
Primary connection for joining vehicle body structures
~80% body structure durability issues are at resistance spot welds
Typical Loading Conditions and Failure Modes of Spot Welds
Lap Shear Coach Peel
5. 507/29/2015
Project Description
Investigate sensitivity of spot weld modeling with CBAR and CWELD
elements on stiffness and fatigue life predictions
• Compare to physical coupon test results
• Help harmonization activity
Testing Parameters:
• Element quality (CBAR) : best, worst
• Connection configurations (CWELD) : best, worst1, worst2
• Sheet metal thickness: 1.0 mm, 1.5 mm/1.6 mm
• Mesh size: 4.0 mm, 5.0 mm, 6.0 mm
• Loading condition: lap shear and coach peel
CBAR weld element CWELD weld element
6. 601/01/2015
Actual Testing/ANSA Model Set-up
Lap Shear Coach Peel
MTS Coupon Cyclic Loading Setup
Lap Shear Coach Peel
Coupon FEA Models
Spot Weld
Constraints
Force
8. 807/29/2015
Analysis Procedure
ANSA
Preprocessing
• Apply Surface Mesh
• Apply Boundary
Constraints and
Loads
HPC SERVER
Run NASTRAN job
• Utilizes Open
Terminal to solve
input deck at
provided parameters
HYPERVIEW
Solution Viewer
• Stress Solution
• Displacement
Solution
nCODE
Postprocessing
• Life fatigue
predictions
• S-N Curves
Report
• Results discussions
• Conclusions
9. 907/29/2015
Results – Stiffness
• CBAR model predicts lower overall stiffness ratio, CWELD predicts higher stiffness ratio
• CWELD Model provide stiffness ratio closer to 1 than CBAR Model.
0.77
0.85
1.20
1.05
0.90
0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
CBAR BEST
CBAR WORST
CWELD BEST
CWELD WORST1
CWELD WORST2
Ratio to Test
ElementConnectionConfiguration
10. 1007/29/2015
Results – Fatigue Life
• CBAR predicts fatigue ratio closer to 1 compared to CWELD
• Overall Fatigue Life is not sensitive for both CBAR and CWELD models, less than 10%
variation between the Worst to the Best element connection configurations.
1.13
1.13
1.25
1.25
1.15
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
CBAR BEST
CBAR WORST
CWELD BEST
CWELD WORST1
CWELD WORST2
Ratio to Test
ElementConnectionConfiguration
11. 1107/29/2015
Element Size Influence
1
1.1
1.2
1.3
CBAR BEST CBAR WORST CWELD BEST CWELD WORST 1 CWELD WORST 2
RatioAverage
Element Connection Configuration
Fatigue Life
4mm
5mm
6mm
• Spot-weld structural stiffness and fatigue for CBAR and CWELD models are not
sensitive to mesh element size.
0.60
0.80
1.00
1.20
1.40
CBAR BEST CBAR WORST CWELD BEST CWELD WORST 1 CWELD WORST 2
RatioAverage
Element Connection Configuration
Stiffness
4mm
5mm
6mm
Element Size
Element Size
12. 1207/29/2015
Future of Project/Takeaways
Contribution
• Obtain sensitivity results for Stiffness and Fatigue Life for CBAR and CWELD element
types to be utilized for future conclusions
• Played a role in prospective completion of harmonization project
Next Steps:
• More parameters (element size, element quality)
• Full-production model analysis
Takeaways
• Analysis software experience
• Transferrable skills
• Exposure to global company in Automotive Industry
13. 1307/29/2015
The Future and Beyond!
Complete Undergraduate
program (VCU)
CIE
Program
Master’s Degree
Mechanical Engineering
Engineer in Training(EIT)
EXAM
Studio Engineer/
Durability Engineer
Thank you coming to my FCA Intern final summer project presentation I had the pleasure of working in the Durability & Development Operations group
5th year majoring in Mech Eng minors in math and physics
Involved in a lot of Student Orgs
Live music, spending time outside, and a huge game of thrones fan, I guess the Michigan locals would say that winter is coming soon
I have previous experience in Project Management through Huntington Ingalls Shipbuilding
Thanks to FCA I’ve had the chance to explore a good amount of CTC as well as interact and network with other Interns from all over the area.
My project this summer was focused on resistance spot welds, let me give you some background on them
It’s important to have accurate CAE modeling because there are over 5,000 spot welds on a car
80% of body structure issues are at spot welds
My project focuses on Lap Shear ( tension shear failure ) and Coach Peel (Bending Moment failure )
This summer I was tasked with a Harmonization using Finite Element Analysis software to compare the sensitivity between two different weld modeling techniques by analyzing the stiffness and fatigue life and comparing those values to the actual testing
CBAR is used by FCA US and CWELD used by FCA Italy and I am trying to see which is better for modeling
CBAR – NODE TO NODE
CEWLD – ELEMENT TO ELEMENT
Looking at Element quality, element configuration, thickness, length of the element
Here you can see the coupon model in ANSA with the applied boundary conditions and loading conditions Top – All DOF constrained
Bottom – All DOF constrained but z (direction of motion)
Here you can see the other configurations for testing also known as element quality, ideal case is uniform
CBAR – the elements were skewed to represent alternatives manners of failure
CWELD – connections of elements altered to represent alternative manners of failure ( Diaganol, Parrallel)
Here is FEA process that I used to calculate the stiffness and life fatigue
Hyper view I calculated stiffness and nCode used for the Life fatigue calculation
The best way for me to gauge effectiveness of the weld method was to use a ratio from the software’s data to the testing data
Here are the ratios calculated for the stiffness calculations, a value of 1 is ideal which means is a good match
CBAR lap shear and coach peel stiffness ratios have little difference between them ( less sensitive )
5mm element size is average target size
CBAR less sensitive – not heavily influence by element configuration
CWELD more sensitive due to larger surface area connection
Real life situation: spot weld loading is combined of coach peel and lap shear
Spot weld fatigue calculation is based on S-N (Cycles) on both so numbers show offset
Element size is not sensitive to fatigue life or stiffness for CBAR and CWELD aligns with what we expect
Trend: as element size increase element becomes stiffer
-larger element size -> force moment is larger ->stress increase -> lower life
Element parameters ( element sizes, CWELD connections)
Spot weld analysis on full vehicle too see how it affects vehicle body structure
Thank you to FCA for this unique opportunity, I will now be taking questions!
