Yield strength refers to the amount of stress or force required to cause permanent deformation in a material. In metals and rigid materials, yield strength marks the transition from elastic deformation (where the material returns to its original shape) to plastic deformation (where it remains permanently deformed).

However, in rubber and elastomers, the concept of yield strength is not as commonly used because rubber behaves differently from metals:

1. Rubber is Highly Elastic

   • Unlike metals, rubber does not have a clear yield point.

   • It stretches significantly before breaking and often returns to its original shape unless overstressed.

2. Instead of Yield Strength, Other Properties Are Used:

   • Tensile Strength – Measures the maximum stress rubber can withstand before breaking.

   • Elongation at Break – Indicates how much rubber can stretch before failure.

   • Modulus of Elasticity – Defines stiffness and resistance to stretching at specific strain levels.

3. When Does Rubber "Yield"?

   • In practical applications, rubber can creep or deform permanently under continuous stress (known as stress relaxation or permanent set).

   • Yielding in rubber often refers to the point where it stretches beyond its recovery limit and does not return to its original shape.

Key Factors Affecting Rubber's Resistance to Deformation

• Material Composition – Natural rubber (NR) and silicone behave differently in stress conditions.

• Crosslinking (Vulcanization) – Stronger crosslinks improve elasticity and reduce permanent deformation.

• Temperature & Aging – Heat and UV exposure can weaken rubber and lead to creep or softening.

• Load Duration – Continuous or high stress may cause permanent set in rubber materials.

Applications Where Yield-like Behavior is Considered

• Seals & Gaskets – Must maintain elasticity without permanent deformation.

• Tires & Belts – Need high tensile strength and wear resistance.

• Shock Absorbers & Mounts – Should resist creep under continuous load.

Conclusion

While yield strength is not a key parameter for rubber materials, tensile strength, elongation, and modulus of elasticity are used to describe its mechanical performance. Rubber does not exhibit a clear yield point like metals, but permanent deformation (set) and stress relaxation are important considerations for rubber applications.