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.