Understanding the Fatigue Notch Sensitivity of High-Strength Steels through Fracture Toughness

This study presents an innovative approach for selecting high-strength materials for fatigue dimensioning parts, considering both fracture toughness and fatigue performance. Warm and hot forming processes enable the construction of high-strength parts above 1000 MPa with complex geometries, making them suitable for lightweight chassis in automotive and freight applications. This research reveals that high-strength steels can experience up to a 40% reduction in fatigue performance due to manufacturing defects introduced during punching and trimming. Fracture toughness has been proposed as a good indicator of notch sensitivity, with a strong correlation of 0.83 between fracture toughness and fatigue notch sensitivity. Therefore, by combining fracture toughness measurements and fatigue resistance obtained through the rapid fatigue test, it becomes possible to quickly identify the most fatigue-resistant materials to deal with defects. Among the nine materials analysed, warm-formed steels show promising characteristics for lightweight chassis construction, with high fatigue resistance and fracture toughness exceeding the proposed fracture threshold of 250 kJ/m(2).

Automated summary

This study introduces an innovative approach for selecting high-strength materials for fatigue dimensioning parts by considering fracture toughness and fatigue performance. Warm and hot forming processes enable the construction of high-strength parts with complex geometries, making them suitable for lightweight chassis in automotive and freight applications. The research shows that high-strength steels may experience a significant reduction in fatigue performance due to manufacturing defects, but fracture toughness can serve as an indicator of notch sensitivity with a strong correlation between fracture toughness and fatigue notch sensitivity. By combining fracture toughness measurements and fatigue resistance tests, the most fatigue-resistant materials can be quickly identified. Among the nine materials analyzed, warm-formed steels demonstrate promising characteristics for lightweight chassis construction with high fatigue resistance and fracture toughness exceeding the proposed fracture threshold of 250 kJ/m(2).