Question

Irwin modified the Griffith's theory and introduced the concept of:

• A. Stress intensity factor.
• B. Plastic zone size.
• C. Energy release rate.
• D. Crack tip opening displacement.

Hint:

Irwin’s major advancement in fracture mechanics was the introduction of the stress intensity factor \( K \), bridging Griffith’s theory to real-world ductile materials.

Answer 1

The Correct Option is A

A.A. Griffith originally proposed a theory of brittle fracture based on energy balance, stating that a crack grows when the energy release rate equals the surface energy required to create new surfaces. However, this approach was limited to brittle materials.
George R. Irwin later extended Griffith’s theory to include ductile materials by introducing the concept of the Stress Intensity Factor (\( K \)). This factor quantifies the stress state near the tip of a crack and is a cornerstone of Linear Elastic Fracture Mechanics (LEFM).
- The stress intensity factor \( K \) depends on the applied stress, crack size, and geometry of the component.
- Fracture occurs when \( K \) exceeds a critical value \( K_{IC} \), known as the fracture toughness.
While other terms like plastic zone size, energy release rate, and crack tip opening displacement are also relevant in fracture mechanics, the key contribution of Irwin was the formalization of \( K \).