Tire Bead Transition Element for Crack Propagation Control
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Solution Overview
Problem
Radial tires for heavy vehicles experience crack propagation in the polymeric coating and stuffing materials due to bending cycles, leading to tire degradation, as existing designs fail to effectively manage stresses and strains at the bead-winding zone on the rim flange.
Innovation Solution
Incorporating a transition element made of polymeric material with a modulus of elasticity intermediate between the coating and stuffing materials, positioned to create a stiffness gradient that reduces stress and strain on the axially outer face of the carcass reinforcement upturn, thereby slowing crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a carcass reinforcement layer with metallic reinforcing elements coated with polymeric coating material is used, then the tire provides mechanical connection and structural integrity, but bending cycles cause crack propagation in the polymeric coating and stuffing materials
Solution Approach 1:
The patent introduces a transition element made of polymeric material with intermediate modulus of elasticity between the stiff polymeric coating material and the more compliant polymeric stuffing material. This transition element acts as a mediator that gradually transitions the stiffness, reducing stress concentration and preventing crack propagation at the interface between the carcass reinforcement upturn and the stuffing material.
Solution Approach 2:
The patent applies parameter changes by selecting a polymeric material for the transition element whose modulus of elasticity is specifically tailored to be intermediate between the coating and stuffing materials. This gradual change in material stiffness parameter creates a stress gradient that reduces the harmful stress concentration at the interface, thereby preventing crack initiation and propagation.
2Device complexity
If the polymeric stuffing material directly contacts the axially outer face of the carcass reinforcement upturn, then the structure is simplified, but stress and strain concentrations initiate cracks that propagate through the polymeric materials
Solution Approach 1:
The transition element serves as an intermediary layer between the carcass reinforcement upturn and the polymeric stuffing material. This additional layer, while increasing structural complexity, prevents direct contact that would cause stress concentration and crack propagation, thereby significantly improving the endurance and reliability of the tire bead.
Solution Approach 2:
The transition element provides beforehand cushioning by being positioned in advance to absorb and distribute stresses before they can concentrate at the critical interface. This preventive measure cushions against the bending cycles and stress concentrations that would otherwise initiate cracks, extending the tire's service life.
3Adaptability or versatility
If the modulus of elasticity of the polymeric stuffing material is significantly different from the polymeric coating material, then material selection flexibility increases, but stress concentration at the interface accelerates crack propagation
Solution Approach 1:
The patent addresses the stress concentration issue by introducing a transition element with a modulus of elasticity parameter that is intermediate between the coating and stuffing materials. This creates a gradual parameter transition rather than an abrupt change, reducing stress concentration while still allowing flexibility in material selection for the outer layers.
Solution Approach 2:
The transition element applies the local quality principle by having different material properties at different locations within the bead structure. The polymeric material's modulus of elasticity varies locally to create an optimal stress distribution gradient, with stiffer material near the carcass reinforcement and more compliant material toward the stuffing material.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The transition element effectively decreases stress and strain, slowing down crack propagation and enhancing the endurance of the tire's beads by establishing a progressive stiffness gradient, reducing the speed at which cracks initiate and spread through the polymeric materials.
Implementation Method 1
a transition member, consisting of a transition polymeric material, being in contact, via its axially inner face, with the polymeric coating material of the axially outer face of the carcass reinforcement upturn and, via its axially outer face, with the polymeric stuffing material, and the modulus of elasticity at 10% elongation of the transition polymeric material being intermediate between the moduli of elasticity at 10% elongation, respectively, of the polymeric coating material and of the polymeric filling material
Data Source
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AI summary
The invention relates to improving the endurance of the beads of a radial tire for a heavy civil engineering vehicle, by reducing the spread rate of the cracks initiated on the axially outer surface of the carcass reinforcement frame and spreading through the polymeric covering and filling materials. According to the invention, a transition element (28) consisting of a polymeric transition material is in contact, via the axially inner surface thereof, with the polymeric covering material of the axially outer surface of the carcass reinforcement frame (21b), and, via the axially outer surface thereof, with the polymeric filling material (26), and the modulus of elasticity at 10% elongation of the polymeric transition material lies between the moduli of elasticity at 10% elongation of the polymeric covering material and polymeric filling material, respectively.