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Table 1 Eight equations of traditional FCG rates prediction models

From: Crack Growth Rate Model Derived from Domain Knowledge-Guided Symbolic Regression

Model name

Equation

Paris’ model

\(\ln C + m \cdot \ln \Delta K\)

Forman’s model

\(\ln C + m \cdot \ln \Delta K - \ln \left[ {(1 - R) \cdot K_{{\text{C}}} - {\Delta }K} \right]\)

Elber’s model

\(\ln C + m \cdot \ln \left( {\frac{\Delta K}{{1 - R}} - K_{{{\text{op}}}} } \right)\)

Kujawski’s model

\(\ln C + m \cdot \alpha_{{\text{K}}} \cdot \ln \frac{\Delta K}{{1 - R}} + (1 - \alpha_{{\text{K}}} )m \cdot {\text{ln}}\Delta K^{ + }\)

Huang’s model

\(\ln C + m \cdot \ln \Delta K + m \cdot \ln M\)

Zhan’s model

\(\ln C + m \cdot \ln {\Delta }K + m \cdot \alpha_{{\text{Z}}} \cdot R\)

NASGRO model

\(\ln C + {\text{m}} \cdot \ln \Delta K + {\text{m}} \cdot \ln \frac{1 - f}{{1 - R}} + p \cdot \ln (1 - \frac{{\Delta K_{{{\text{th}}}} }}{\Delta K}) - q \cdot \ln (1 - \frac{{K_{\max } }}{{K_{{\text{C}}} }})\)

Simplified NASGRO model

\(\ln C + {\text{m}} \cdot \ln \Delta K + {\text{m}} \cdot \ln \frac{1 - f}{{1 - R}} + p \cdot \ln (1 - \frac{{\Delta K_{{{\text{th}}}} }}{\Delta K})\)