Pneumatic Tire Bead Apex Elastic Moduli Stress Distribution
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Solution Overview
Problem
Run flat tires with high elastic modulus apices face stress concentration issues during punctures, affecting durability and ride comfort due to uneven stress distribution between the apex and insert.
Innovation Solution
A pneumatic tire design featuring beads with inner and outer apices of varying complex elastic moduli, where the inner apex is more flexible and the outer apex is harder, with an insert positioned outward of the inner apex, optimizing stress distribution and durability while maintaining ride comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a crosslinked rubber having a high elastic modulus is used for the apex, then steering stability is improved, but the apex transmits vibration caused due to unevenness of a road surface, deteriorating ride comfort
Solution Approach 1:
The apex is divided into multiple regions with different elastic moduli: a first region with a first elastic modulus and a second region with a second elastic modulus lower than the first. This segmentation allows the first region to provide steering stability while the second region reduces vibration transmission, resolving the contradiction between stability and ride comfort.
Solution Approach 2:
Different regions of the apex are assigned different material properties (elastic moduli) according to their functional requirements. The first region has higher stiffness for steering stability, while the second region has lower stiffness to absorb vibrations from road unevenness, achieving both stability and comfort through localized property variation.
2Stability of the object's composition
If an apex having a high elastic modulus is used, then steering stability is improved, but stress is concentrated on the boundary face between the insert and the apex when internal pressure is reduced, affecting run flat durability
Solution Approach 1:
The apex is designed with a first region having a first elastic modulus and a second region having a second elastic modulus lower than the first. The second region with lower modulus is positioned to reduce stress concentration at the boundary with the insert when internal pressure is reduced, while the first region maintains steering stability. This local variation in material properties resolves the contradiction between stability and durability.
Solution Approach 2:
The apex is segmented into multiple regions with different elastic moduli to distribute stress more evenly. The first region provides the necessary stiffness for steering stability, while the second region with lower modulus acts as a stress-relief zone at the boundary with the insert, preventing stress concentration and improving run flat durability.
3Ease of manufacture
If the apex is formed from a single rubber composition, then manufacturing is simplified, but it is difficult to simultaneously achieve both ride comfort and run flat durability
Solution Approach 1:
The apex is formed as a composite structure with a first region and a second region having different elastic moduli. This composite design allows the apex to simultaneously achieve ride comfort (through the lower modulus second region) and run flat durability (through the stress distribution provided by the multi-region structure), overcoming the limitations of single-composition apices while remaining manufacturable.
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 tire achieves improved ride comfort and run flat durability by reducing stress concentration and maintaining stiffness, allowing vehicles to travel a certain distance even with reduced internal pressure.
Implementation Method 1
A ratio of a complex elastic modulus Ea of the inner apex to a complex elastic modulus Eb of the outer apex is less than or equal to 0.3
Data Source
Figure 1
Figure 2
AI summary
A tire 2 includes beads 10, a carcass 12, and an insert 18. The carcass 12 includes a carcass ply 36. An inner part 34a of each bead 10 includes an inner core 46a and an inner apex 48a that extends almost outward of the inner core 46a in the radial direction. An outer part 34b of each bead 10 includes an outer core 46b and an outer apex 48b that extends almost outward of the outer core 46b in the radial direction. A ratio of a complex elastic modulus Ea of the inner apex 48a to a complex elastic modulus Eb of the outer apex 48b is less than or equal to 0.3. A ratio of the complex elastic modulus Ea to a complex elastic modulus Ec of the insert 18 is greater than or equal to 1.