Tire Bead Transition Element for Stress Gradient
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Solution Overview
Problem
Radial tires for heavy civil engineering vehicles experience crack propagation and degradation due to stress and deformation cycles, particularly at the end of the carcass reinforcement upturn, resulting from adhesion defects between metal reinforcing elements and polymeric coating and filling materials, leading to premature tire deterioration.
Innovation Solution
Incorporating a transition element made of polymeric material with a modulus of elasticity at 10% elongation intermediate between the flanging and filling materials, positioned between the end of the carcass reinforcement upturn and the bead core, to create a gradual stiffness gradient that reduces stress and deformation, thereby slowing crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polymeric filling material with high adhesion is used to cover the end of the carcass reinforcement upturn, then crack initiation is reduced, but the modulus of elasticity mismatch with the flanging material causes stress concentration and crack propagation
Solution Approach 1:
The patent introduces a transition element with intermediate modulus of elasticity (100-500 MPa) between the flanging material (500-1000 MPa) and filling material (50-200 MPa). This gradual parameter change creates a stiffness gradient that reduces stress concentration while maintaining adhesion, preventing both crack initiation and propagation at material interfaces.
Solution Approach 2:
The patent employs a composite structure with three distinct polymeric materials (flanging, transition, and filling) having progressively different mechanical properties. This composite approach allows each layer to serve its specific function while collectively resolving the stress concentration problem through controlled modulus of elasticity variation.
2Stress or pressure
If the modulus of elasticity of the filling material is increased to match the flanging material, then stress concentration is reduced, but crack propagation speed increases due to higher rigidity
Solution Approach 1:
The transition element's intermediate modulus of elasticity (100-500 MPa) creates a gradual stiffness transition zone. This parameter gradient allows stress distribution improvement without creating a rigid pathway for crack propagation, as the progressive rigidity change dissipates crack energy rather than transmitting it rapidly.
3Ease of manufacture
If a single-layer polymeric coating is used for simplicity, then manufacturing is easier, but adhesion defects occur at the interface between flanging and filling materials
Solution Approach 1:
The patent divides the polymeric coating into three distinct layers (flanging, transition, and filling materials) with different mechanical properties. This segmentation allows each layer to be optimized for its specific function while collectively providing superior adhesion and stress distribution compared to a single-layer coating.
Solution Approach 2:
Each polymeric layer is designed with specific local properties: the flanging material provides initial adhesion and flexibility, the transition material provides intermediate stiffness and stress distribution, and the filling material provides final coverage and protection. This local quality differentiation resolves adhesion defects while maintaining manufacturing feasibility.
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 decreasing the spread rate of the cracks initiated at the end of the carcass reinforcement frame and spreading through the polymeric covering, edging and filling materials. According to the invention, a transition element (25) consisting of a polymeric transition material is at least partially in contact, via the axially outer surface thereof, with the polymeric edging material (22) and, on the axially inner surface thereof, with a polymeric filling material (23b); the radially outer (E25) and radially inner (I25) ends of the transition element are radially outside and radially inside the end of the carcass reinforcement frame, and the modulus of elasticity at 10% elongation of the polymeric transition material is intermediate between the moduli of elasticity at 10% elongation of the polymeric edging material and polymeric filling material, respectively, with which the transition material is in contact.