Non-Pneumatic Tire Spoke Edge Geometry Fatigue Reduction
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Solution Overview
Problem
Non-pneumatic tires with traditional spoke edge geometry are prone to fatigue due to bending stresses and manufacturing flaws like flash and mold mismatch, which create stress risers that lead to crack initiation and propagation, reducing the durability and operability of the tire.
Innovation Solution
The spoke edge geometry is redesigned with a reduced cross-section and a unique mold construction that includes angled shut-off surfaces and telescoping cores to minimize flash and mold mismatch, orienting flash parallel to the neutral bending plane, thereby reducing bending stresses and strains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional spoke edge geometry is used, then manufacturing is simpler, but bending stresses and stress risers increase leading to fatigue failure
Solution Approach 1:
The spoke edge geometry is modified locally at the extremity where it contacts the tread, creating a reduced cross-section that specifically addresses the stress concentration problem at this critical location while maintaining the original geometry elsewhere in the spoke body
Solution Approach 2:
A fillet radius is added at the spoke edge extremity to create a curved transition instead of a sharp corner, distributing stresses more evenly and eliminating the stress riser that would otherwise exist at the sharp edge
2Reliability
If traditional mold construction is used, then manufacturing process is simpler, but flash and mold mismatch create stress risers
Solution Approach 1:
The mold is designed with angled shut-off surfaces and telescoping cores that proactively prevent flash and mold mismatch from occurring in the first place, rather than trying to correct these defects after they form
Solution Approach 2:
The potential harmful effect of flash is converted into a beneficial outcome by orienting it parallel to the neutral bending plane through the angled shut-off surface design, making the flash less susceptible to cracking under bending loads
3Stress or pressure
If spoke cross-section is reduced at edge, then bending stresses are reduced, but structural strength may be compromised
Solution Approach 1:
The cross-section is reduced only at the specific location of the edge extremity where it contacts the tread, which is where the stress concentration problem occurs, while maintaining full cross-section elsewhere in the spoke to preserve overall structural strength
Solution Approach 2:
The fillet radius creates a smooth curved transition that distributes stresses evenly through the reduced cross-section, preventing stress concentration that would otherwise occur at sharp corners and maintaining strength despite the reduced material
Data Source
Figure 1
Figure 2A~2C
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AI summary
The present invention provides improved spoke edge geometry for a non- pneumatic or hybrid tire that is less prone to fatigue when used. The present invention also provides a way to manufacture such geometry in a mold, In particular the spoke edge geometry is provided with a reduced cross-section that reduces the bending stresses locally and allows a unique mold construction that changes the placement and orientation of potential flash and reduces other potential molding flaws when a liquid such as polyurethane is introduced into the cavity of the mold to form a spoke. This change results in a reduction in the possibility of a stress riser being found near the edge of the spoke, enhancing the durability of the tire.