Understanding Valve Spring
Science
and Selection, for Optimization,
Performance, and Longevity
Presenter:
Jason YoudPAC Racing Springs
AETC Conference 2011
• Static Stress and Design
• Dynamic Stress and Design
• Other Finite Components
• It’s all in the details
Key Spring Life Factors Overview
Spring Design and Application
Processing
30%
Spring Design
25%
Material
15%
Dynamic Design (System)
30%
Spring Design Overview Application Performance
•Material Selection (Alloy)
• Processing Selection (Recipe)
• Spring Type: Single, Beehive, Dual, Dampers, Triple
• Wire Shape
• Stress Range Comparisons
• Fatigue Requirements or Performance Requirements
• System Design inputs (RPM, Valve Lift Profile, Mass, other)
Spring Life Design Factors (Static)
Spring Life Design Factors (Static)
Spring Design Factors for Stress/Life Management
•Increase Tensile Strength
• Alloy Selection
• Heat Treating
•Metal Improvement with Addition of Compressive Stress or reduction in Tensile Stress
• Shot Peening
• Stress Relieving
• Polishing (removes stress risers)
•Spring Design Considerations
• Wire Shape
• Space and Application Considerations
• Required Load (Dynamic Control)
Spring Life Design Factors (Static)
Material Tensile Strength V. Application
250
270
290
310
330
350
370
OEM LS (Street) Circle Track Drag Race
0
10
20
30
40
50
60
70
80
90
Tensile Strength
% of tensile
Typical ASTM
Fastener % UTS
Spring Life Design Factors (Static)
Spring Life (Fatigue and Load)
-
10,000,000
20,000,000
30,000,000
40,000,000
50,000,000
60,000,000
70,000,000
80,000,000
90,000,000
100,000,000
OEM LS (Street Replacement) Circle Track Drag Race
Cycles to failure
0
20
40
60
80
100
120
Load Loss (Lbs)
Life Expectancy
Load Loss
Spring Life Design Factors (Static)
Stress Range Comparisons
20%30%
40%
65%
0
50
100
150
200
250
300
350
OEM LS (Street Replacement) Circle Track Drag Race
Application Type
Stress Range (Factor)
0%
50%
100%
150%
200%
250%
Dynamic Amplification %
Static Stress Range
Dynamic Stress Range
Dynamic % increased
• Dynamic Stress Range
• Impact Force (Surge)
• Load Loss Impact (maintain dynamic robustness)
• Cooling and Heat
• Interference
• Damping (designed or external)
- Rate Curve (progressive, dual, linear)
- Frictional Damping (ribbon damper, interference of stacked springs,
or external damper)
Spring Life Dynamic Stress Factors
Spring Life Dynamic Factors
Dynamic Amplification % ( Stress Increase % over Static)
0
5
10
15
20
25
30
35
500 1500 2500 3500 4500 5500
Engine Speed (RPM)
Dynamic Amplification (%)
Spring Life Dynamic Factors
Exhaust Spring Seat Load
100
125
150
175
200
225
250
275
300
325
350
375
400
425
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440
Crank Angle (deg)
Spring Seat Load (lbs)
1000
1995
3005
4000
5003
6042
6154
6351
6575
6761
7025
7157
7360
7557
7780
Spring Life Dynamic Stress Factors
Dual LS Spring (Right Bank)
After 3 Hrs Steady Run Non-
Fired Engine
(no external heat or cooling)
***Note increased thermal
profile from inside spring
Spring Life Dynamic Stress Factors
Beehive LS Spring (Left
Bank)
After 3 Hrs Steady Run Non-
Fired Engine
(no external heat or cooling)
***Note reduction in heat
from inside spring
Spring Life Analysis
Excessive wear from spring to Excessive wear from spring to
spring contact resulting in failure. spring contact resulting in failure.
Removal of shot peened surfaceRemoval of shot peened surface
Spring Life Dynamic Performance
Effect of Temperature on Spring Open Load
-100
-80
-60
-40
-20
0
20
50 100 150 200 250 300 350 400
Temperature (Degrees F)
Load (lbs)
Spring Life Dynamic Performance
Effect of Temperature on Rate
-60
-50
-40
-30
-20
-10
0
10
50 100 150 200 250 300 350 400
Temperature (Degrees F)
Rate (lbs/inch)
Spring Life Dynamic Control (Hysteresis)
Hysteretic Loop - is the difference vs. the static applied load (input) vs. the measured output or response (in this case interference).
We use this method to gage interference and frictional damping coefficients.
This method is also used in industry to determine system rigidity and compliance.
Note****
This is essentially measuring the force in compression and overlaying the force in re-bound.
Spring Life Dynamic Control (Hysteresis)
Example of Hysteresis Loop
1.000
1.200
1.400
1.600
1.800
2.000
2.200
0 50 100 150 200 250 300 350 400
Force
Measured Height
Spring Force
Spring Life Dynamic Control (Hysteresis)
Hystresis - Percent Difference of Load
-7%
-6%
-5%
-4%
-3%
-2%
-1%
0%
Single Cylindrical
Spring
Single Beehive
Dual Minimum
Interference
Triple B&C Tight
C&D Loose
Dual Tight but
moves
Triple B&C Tight
C&D Tight but
moves
Triple B&C Tight
C&D Tight
Dual Tight
Single Beehive with
1 Steel Ring OD
Plastic Damper
Dual with Steel
Damper between
Outer and Inner
Dual with 2 Steel
Ring OD Plastic
Damper
Dual_plastic
damper bewteen
outer and inner
Difference Load (%)
Spring Life Dynamic Control Alternatives
Typical Steel OD damper Typical Steel Ribbon damper
Spring Life Dynamic Control Alternatives
Spring Life Dynamic Control Alternatives
Spring Life Dynamic Control Alternatives
Oil Ports
(Exit)
Spring Life Dynamic Control Alternatives
Tension Rings
(provide damping force)
Engine Oil >in<
through hydraulic
action-oil captive with
retainer.
Engine Oil >out< through
hydraulic action-sized for
volume-(hydraulic damping
and cooling needed)
Engine Oil >in<
through hydraulic
action-oil captive with
retainer.
Thank You!
For Attending the 2012 AETC Conference
For More information please contact PAC Racing Springs www.RacingSprings.com
Special thanks to:
Kyle Kibbey
John Keteyian
Spring Life Design Factors (Static)