Heavy Duty Tyre Tread Cracking Resistance
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Solution Overview
Problem
Heavy civil engineering tires face cracking issues due to stone retention in cutouts, leading to reduced lifespan, particularly with high volumetric notch rates and surface lamination rates, which existing tire designs fail to adequately address.
Innovation Solution
A tire tread design with a surface siping rate of at least 3 m/m², an elastomeric mixture resistant to cracking with at least 60,000 cycles to rupture, and a ratio of cycles to failure to siping rate of at least 20,000 cycles/(m/m²), combined with effective cutouts that reduce stone retention and enhance ventilation, is implemented.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the volumetric notch ratio and surface siping rate are increased to improve grip and ventilation, then the tire's grip performance and ventilation are enhanced, but the risk of stone retention and crack initiation at the base of cutouts increases
Solution Approach 1:
The patent specifies precise parameter ranges: surface siping rate between 2-10 m/m² (optimally 3-7 m/m²), volumetric notch ratio between 8-15% (optimally 10-12%), and cutout depth between 0.04-0.08 times the tread radial thickness (optimally 0.05-0.06 times). These parameter optimizations balance grip enhancement with crack resistance by preventing excessive stone retention while maintaining adequate ventilation channels.
Solution Approach 2:
The tread employs a composite elastomeric compound containing specific proportions of natural rubber (20-40 parts), synthetic polybutadiene rubber (30-50 parts), carbon black (40-60 parts per hundred rubber), and silica (10-30 parts per hundred rubber). This composite formulation enhances both grip performance and resistance to crack propagation at cutout bases, addressing the reliability concern while maintaining the high siping rate design.
2Temperature
If deep cutouts are used to enhance ventilation and cooling, then the internal crown temperatures are reduced, but the cutouts may retain stones that initiate cracks
Solution Approach 1:
The cutout depth is precisely controlled to be between 0.04-0.08 times the tread radial thickness (optimally 0.05-0.06 times), and the volumetric notch ratio is limited to 8-15% (optimally 10-12%). This parameter optimization ensures sufficient ventilation channels for cooling the internal crown while preventing excessive depth that would cause stone retention and crack initiation.
3Ease of operation
If the surface siping rate is increased to improve grip, then the tread's grip performance is enhanced, but the number of potential crack initiation sites increases
Solution Approach 1:
The surface siping rate is optimized to between 2-10 m/m² (optimally 3-7 m/m²) rather than being maximized. This moderate optimization provides sufficient grip enhancement while limiting the number of cutouts that could serve as crack initiation sites, thereby extending tire lifespan.
Solution Approach 2:
The elastomeric compound incorporates specific ratios of natural rubber (20-40 parts) and synthetic polybutadiene rubber (30-50 parts) with reinforcing fillers (carbon black 40-60 phr, silica 10-30 phr). This composite material formulation enhances crack propagation resistance at cutout bases, allowing the tread to maintain high surface siping rates for grip while compensating for the increased number of potential failure sites through improved material toughness.
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
The present invention relates to a radial tyre (1) intended to be fitted to a heavy-duty vehicle of the civil engineering construction plant type and, more particularly, to the tread (2) thereof. According to the invention, such a tyre is characterized by a tread surface siping extent TL at least equal to 3 m/m2, a number of cycles to rupture NR of the elastomeric compound of the tread, at least present in the bottom of the cuts (21), at least equal to 60000 cycles and a ratio C, which is the ratio between the number of cycles to rupture NR of the elastomeric compound and the tread siping extent TL, at least equal to 20000 cycles/(m/m2).