Tire Bead Cushion Rubber for Crack Propagation
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Solution Overview
Problem
Radial tires for civil-engineering heavy vehicles experience crack initiation and propagation in the coating elastomer of the reinforcing layer due to bending cycles, leading to damage and reduced endurance.
Innovation Solution
Incorporating a cushion rubber layer with a lower elastic modulus than the carcass layer reinforcement, positioned between the carcass reinforcement and the bead reinforcing layer, to absorb and distribute deformation and prevent crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bead reinforcing layer is added to improve bead endurance, then crack propagation is prevented, but device complexity increases
Solution Approach 1:
The bead reinforcing layer is segmented into multiple zones with different orientations: a first portion with cords oriented at 0-15 degrees to the circumferential direction and a second portion with cords oriented at 30-45 degrees. This segmentation allows different regions to handle different stress patterns, preventing crack propagation while maintaining structural efficiency.
Solution Approach 2:
The bead reinforcing layer uses composite construction with textile cords embedded in elastomeric material, combining the tensile strength of textiles with the flexibility and damping properties of elastomers. This composite approach enhances bead endurance without excessive complexity increase.
2Reliability
If the bead reinforcing layer covers the entire bead wire core, then protection is maximized, but manufacturing complexity increases
Solution Approach 1:
The bead reinforcing layer is applied selectively to specific zones where cracks are most likely to initiate and propagate, rather than uniformly across the entire bead. The first portion covers the heel area with 0-15 degree orientation while the second portion extends along the sidewall with 30-45 degree orientation, providing targeted protection where needed most.
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 cushion rubber effectively reduces deformation energy density and prevents crack propagation, enhancing the endurance of the tire by distributing stress and maintaining the tire's structural integrity under load and rotation.
Implementation Method 1
a cushion rubber made up of an elastomeric compound M3 having an elastic modulus in extension at 100% elongation E3, said cushion rubber being interposed between the carcass reinforcement and the bead reinforcing layer
Implementation Method 2
The cushion rubber effectively reduces deformation energy density and prevents crack propagation, enhancing the endurance of the tire by distributing stress
Data Source
AI summary
Improving the endurance of the beads (1) of a radial tire for a civil-engineering heavy vehicle by proposing a solution which blocks the propagation of the cracks initiated in the coating elastomer of the bead reinforcing layer (5), by inserting a cushion rubber (6) interposed between the coating elastomer of the carcass layer turn-up (312) and the coating elastomer of the bead reinforcing layer (5). The elastic modulus in extension of the cushion rubber (6) measured at 100% deformation must be less than the elastic modulus of the coating compound of the carcass layer. Still according to a disclosed embodiment, the thickness of the cushion rubber (6) is at least equal to the thickness of the bead reinforcing layer (5).