Design Elements of Steel Belted Radial Tires
to Improve Belt Durability
By Don Lee
Cut-Away View of Car/SUV Radial Tire
Belt Edge Inter-laminar Shear Strain
Inter-laminar Shear Strain is Maximum at Belt Edges*
*The Pneumatic Tire, Ed. by A.N.Gent & J.D.Walter NHTSA 2005
Belt-leaving-belt Tread Separation
Major Design Factors affecting Belt Durability
 Nylon Overlay
 Belt Edge Strip Gauge
 Belt Skim Gauge
 Tire Contour
 Belt Cord Construction
 Belt Edge Step
3-D Finite Element Analysis
3-D Finite Element Analysis
3-D Finite Element Analysis
Braking
Traction
Applications of FEM in Tire Development/Evaluation
1.
2.
3.
4.
5.
6.
Durability (Stress/Strain Analysis)
Rolling Resistance Prediction
Ride & Handling (Force and Moment Calculation)
Hydroplaning
Noise
others
Strain Energy Density Analysis by FEM
A
A
Loaded
Inflated
Nylon Overlay Effect
-Strain Strain by FEM
Shear Strain
7.00E-01
6.00E-01
Shear Strain
5.00E-01
4.00E-01
Min
Max
3.00E-01
Amplitude
2.00E-01
1.00E-01
0.00E+00
No Nylon Overlay
1 Nylon Edge Cover
Reinforcement Type
1 Nylon Full Cover
Nylon Overlay Effect
-Indoor Drum Test*
140
125
130
120
100
Durability Index
100
80
60
40
20
0
No Nylon Overlay
1 Nylon Edge Cover
Reinforcement Type
1 Nylon Full Cover
* P-Metric Tires / Average of Step up speed and Step up load tests / Data courtesy of Q Tires Inc.
Belt Wedge Effect
-Shear Strain by FEM
Shear Strain
9.00E-01
8.00E-01
7.00E-01
Shear Strain
6.00E-01
Min
5.00E-01
Max
4.00E-01
Amplitude
3.00E-01
2.00E-01
1.00E-01
0.00E+00
0.5 mm
1.5 mm
Wedge Thickness
Belt Wedge Effect
-Indoor Drum Test
140
125
120
100
100
80
60
40
20
0
0.06"(1.5mm)
0.08"(2.0mm)
* P-Metric Tires / Average of Step up speed and Step up load tests / Data courtesy of Q Tires Inc.
3-Steel belted vs. 2-Steel belted with Nylon Overlay
-Shear Strain by FEM
Shear Strain
7.00E-01
6.00E-01
Shear Strain
5.00E-01
4.00E-01
Min
Max
3.00E-01
Amplitude
2.00E-01
1.00E-01
0.00E+00
3 steel Belt
2 Steel + 1 Nylon Full
Belt Construction
3-Steel belted vs. 2-Steel belted with Nylon Overlay
-Strain Strain FEM
Strain Energy Density
5.00E+05
Strain Energy Density (Pa)
4.50E+05
4.00E+05
3.50E+05
3.00E+05
Min
2.50E+05
Max
2.00E+05
Amplitude
1.50E+05
1.00E+05
5.00E+04
0.00E+00
3 Belt
2 Steel + 1 Nylon Full
Belt Construction
Conclusions:
3-dimensional FE analyses on P-metric tires have been pursued and the shear
strains and the strain energy densities have been calculated by changing various
design parameters. The following conclusions are evident:
1. The shear strain amplitude and the strain energy density can be used to predict belt
durability of steel belted radial tires.
2. The use of nylon cap plies including the nylon edge cover and the nylon full cover
can reduce belt edge shear strain and shear strain amplitude and it can improve
belt durability. The FE results agreed with the drum test results.
3. The thickness of belt edge strip (belt wedge) affects the shear strain and strain
energy density at belt edge. Keeping sufficient thickness of the belt wedge is critical
to belt durability.
4. Adding a steel belt layer (protection belt) cannot reduce maximum shear strain at
belt edge. The use of nylon cap ply is more efficient way to improve belt durability
Forward Plan
Further study will be followed to access other design parameters affecting to belt
durability of steel belted radial tires.
The design factors may include tire in-mold contour feature, rubber compound and
material properties.