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Validation, Benchmarking and Deployment of GT-CRANK at
Cummins
Ilya PiranerCummins, Inc.
J. Rodriguez, M. Okarmus, S. Erogbogbo, R.Keribar
Gamma Technologies
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• 2+ year project, now near completion
• GTI Objectives – Team with a leading industrial partner with expertise/data
– Explore fast analysis methods for crankshaft durability
analysis• Cummins Objectives
– Unify crankshaft design analysis procedures in a singletool
– Migrate from in-house to commercially supported software
– Integrate with other GT-SUITE elements (GT-POWER,GT-VTRAIN) used at Cummins
Joint GTI-Cummins Development Project
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Cummins Perspective & Background
• Since late 90s the Company strategy has been to partnerwith leading software development / consulting companies inorder to replace in-house simulation codes with a more
efficient commercial software utilizing latest technologies.
• In 2005 a DFSS project has been run to “Determine voice of the customers and Identify commercial tool for concept/design level crankshaft and bearing analysis ”
• The primary customers voice was “Improve ease of use
and efficiency while preserving current tool functionality and speed ”.
• As a result of the project technical requirements have been
developed and a number of competitive products have beenexamined.
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Cummins: Evaluation of Tools
Functional Product Requirements Target Range (with Units) In-house Tool 1 GT
ESW tasks supported 100% 100 90 100
Time to run single analysis 2 min 2 2 2
Tech. Documentation and Support (ToolFunctionality Covered in Help)
95% 75 90 95
Set up Time 4 hours 4 4 4
Integrated Block Bending Analysis 100% Configurations 100 0 100
Integrated Balance Analysis 100% Configurations 0 0 100
Platform Independent GUI with Help 2 0 2 2Time to Learn 2 days 1 3 2
Parametric Study 5 parameters/3 levels 1 3 5
Optimization tool y/n N Y Y
Adequate Physical Models 10 (scale) 9 5 9
PTO Tool 10 (scale) 8 0 9
IACS (M53) Analysis y/n Y Y Y
Postprocessing Time 10 (scale) 3 6 9
Overall Score 621 606 990
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Joint GTI-Cummins Development Project
• Project Scope – Absorb existing Cummins crankshaft analysis techniques into GT-
CRANK
– Benchmark and validate GT-CRANK against Cummins in-housetools
– Deploy GT-CRANK at Cummins worldwide
• GT-CRANK models affected(*
indicates new feature)
– Freq. domain torsional analysis (2005-2006)
– Crankshaft Bending (2006)*
– Bearing oil films (2006)
– Stresses & fatigue (2006-2007)* – Outputs and post-processing (2005-2007)
• Most objectives met by the initial v6.2 release
• Remainder in GT-CRANK v6.2 Builds 6, 8
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Project Objectives
• GTI
– Team with a leading industrial partner with expertise/data – Explore fast analysis methods for crankshaft durability
analysis
• Cummins – Unify crankshaft design analysis procedures in a single
tool
– Migrate from in-house to commercially supported software
– Integrate with other GT-SUITE elements (GT-POWER,GT-VTRAIN) used at Cummins
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Cummins HD I-6 Diesel Engine Model
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Cummins V-8 Short Block Engine Model
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Torsional Vibrations
GT-CRANK v6.1:• Time and frequency-domain (free + forced) TV
• General, cranktrain + attached components
Additional Features:
• Frequency-dependent non-linear damping
• Enhanced and very comprehensive outputoptions
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Comparison to Cummins Torsional Vibration Analysis
I-6 Engine Speed Sweep
Power Loss in Torsional DamperDisplacement Amplitude vs. Speed:
Orders 1.5, 3.0, 4.5 and 6.0
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Journal Bearing Oil Films
GT-CRANK v6.1:
• HD-Impedance solution, Orbit, MOFT, Friction
Now:
• HD-Mobility solution option• Oil flow modeling and thermal balance
• Coupled crank bending + bearing oil film
solution• Effect of oil grooves and holes
• Option for a simplified power loss/flow model
(Orlov)
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Comparison to Cummins V-8 Main Bearing Orbits – 4000 RPM
0
20
40
60
80
100
120
140
160
180
200
1 2 3 4 5
P O F P ( M p a
)
Main Bearing Number
Peak Oil Film Pressure
GT
Cummins
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1 2 3 4 5
M O F T ( µ m
)
Main Bearing Number
Minimum Oil Film Thickness
GT
Cummins
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CrankShaft Bending
GT-CRANK v6.1: No crankshaft bending model
Now:
• Crankshaft bending by 3D Beam-FE
formulation• Beam cross-section properties from
compliances of crankthrow 3D FE model
• Quasi-static or dynamic solution• Coupled to journal bearing oil films, or
springs & dampers
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Equivalent 3D Beam FE Model
Elements
Nodes
3D crankthrow solid FE
model compliances usedto automatically createequivalent 3D Beam FEmodel
Compliance for 3 load cases3D FE Analysis
S o l u
t i o n f o r b
e a m
s e c t i o
n p r o p
e r t i e
s
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Comparison to Cummins V-8 Main Bearing Loads – 4000 RPM
Maximum Bearing Force
0
10000
20000
30000
40000
50000
60000
70000
1 2 3 4 5
Main Bearing Number
F o r c e ( N )
GT
Cummins
Crank Bending Animation with Contours of Mx
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Simplified EFR Stress/Fatigue Analysis
• Maximum stress/moment ratios for journal & crankpinfillet from 3D FE analysis of throw under in-planepositive and negative crankpin loads only, input to GT-
CRANK.• Instantaneous concentrated stresses recovered in GT-
CRANK
• EFR Stress calculated and fatigue “Acceptability”
predicted EFR= amp
/(1- mean / tfs
)
Acceptability = EFR.limit / EFR
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Main Fillets Stre ss
0
50
100
150
200
250
300
350
400
1 2 3 4 5 6 7 8
Web #
S t r e s s ( M p a )
GT
Cummins
Pin Fillets Stre ss
0
50
100
150
200
250
300
350
1 2 3 4 5 6 7 8
Web #
S t r e s s ( M p a )
GT
Cummins
Comparison to Cummins V-8 Web Fillet EFR Stresses I-6 1600 RPM V-8– 4000 RPM
Crankpin
Fillet
Journal
Fillet
Web 1L -1.94 -0.98
Web 1R -4.69 -3.81
Web 2L -3.04 -2.48
Web 2R -4.01 -3.21
Web 3L -3.48 -2.81
Web 3R -0.78 -0.93
Web 4L -1.74 -0.85
Web 4R -1.91 -1.94
Web 5L -2.98 -2.43
Web 5R -1.91 -1.37
Web 6L -4.66 -3.45
Web 6R -0.95 -0.93
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EFR Stress/Fatigue
by Unit Load FEA Stress Recombination • Technique developed by Cummins (Piraner,
2002)
• Embedded & automated in GT-CRANK (v6.2Build 8)
• More-comprehensive alternative to simplifiedEFR stress/fatigue analysis option:
- Does not rely on prior determination of maximum nodal FEA stress-
to-moment ratios in stress concentration zones- Considers the entire and true composite dynamic load stress field,
reconstituted from stress fields for all unit loads
• Rigorous coupling of GT-CRANK analysis + 3DFEA
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Unreliability or Acceptability Calculationfrom Stress and Strength Variances
EFR Stress/Fatigue Methodology II
EFR,max,m,s= max
i(EFR,j,m,s
)
EFR,max,s= maxm (EFR,max,m,s)
EFR,max = max j (EFR,max,,s)
EFR,j,m,s= amp,j,m,s
/(1- mean,j,m,s / tfs
)
Maximum EFR Stress in StressConcentration Zone, Crankthrow and
Crankshaft
EFR (Equivalent Fully-Reversed) Stress
Cyclic Maximum, Minimum, Mean &Amplitude of SPS and Stress Tensor.
Von Mises “amplitude” stress*
Sorted Principal Stress (SPS) j,k,m,s
Unit Load Stress Superposition(Instantaneous Stress Tensor)
i,j,k,m,s= nFk,nC n i,j,k,m,s
AEFR
= 1-UREFR
* “Von Mises” Stress based on stress cyclic amplitude
tensor
max,j,m,s= max
k ( j,k,m,s)
min,j,m,s= min
k ( j,k,m.s
)
mean,j,m,s=avg
k ( j,k,m,s
)
amp,j,m,s = (max,j,m,s- min,j,m,s)/2
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BackPin fillet
BackJournalFillet
Comparison to Cummins EFR Stress & Acceptability
Four stress concentration zones considered
Front JournalFillet
FrontPin fillet
FRONT
JOURNALFILLET
BACK
JOURNALFILLET
FRONT PINFILLET
BACK PINFILLET
% Diff % Diff % Diff % Diff
Max. Component Stress 0.86 0.38 0.80 0.48
EFR Stress –SPS Method 0.48 0.43 0.60 0.44
EFR Stress –VMS Method 0.45 0.40 0.30 0.26
Unreliability-SPS Method 8.41 8.12 9.65 5.19
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Outputs, Post-Processing, Automation
LoadAngle
FF
Cyclic Block Moment Diagram Oil Film Extent & Pressure Contours
Max. Acceptable End Load vs.Angle
Crankshaft Bending Animation
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Summary
• GT-CRANK now meets all Cumminsrequirements for a fast crankshaft design
analysis tool• GT-CRANK now has a comprehensive crankshaft
durability analysis capability, while at the same
time it remains a rapid tool still offeringopportunities for optimization/DOE.
• Current GT-CRANK development work focused
on
• Dynamic solution CPU time improvement via harmonic (Herting)reduction
• Improvement of stress/fatigue scheme for split-pin crankshafts