# Experimental Study on Fatigue Performance of Steel Used in U75V Rails

## TL;DR

This study tests the fatigue performance of U75V steel rails used in China's high-speed rail network to understand their durability and crack propagation behavior.

## Contribution

The study reveals that crack growth in U75V rails is influenced by both stress-intensity range and loading force due to plasticity-induced crack closure.

## Key findings

- Monotonic tensile tests confirmed U75V rail compliance with Chinese national standards.
- Fatigue crack propagation is affected by loading force range due to crack tip shielding effects.
- Results provide data for predictive fatigue life modeling and refined finite element analysis.

## Abstract

The 60 kg/m U75V rail serves as the predominant rail type within China’s high-speed rail network. This study comprehensively evaluates the fatigue behavior of U75V rails through experimental investigations encompassing monotonic tensile testing, high-cycle fatigue characterization, and fatigue crack propagation analysis. All specimens were extracted from standardized 60 kg/m high-speed rail sections to ensure material consistency. Firstly, monotonic tensile tests were conducted to determine the fundamental mechanical properties of the U75V rail. Secondly, uniaxial tension–compression fatigue tests were conducted to establish the S-N and P-S-N relationships of the U75V rail. Lastly, fatigue crack propagation analysis was carried out on three compact tension specimens under three incremental loading forces. Monotonic tensile test results demonstrated full compliance of the material’s basic mechanical properties with Chinese national standards. Fatigue crack propagation results indicated that the crack growth rate of the U75V rail was not only related to the stress-intensity range ∆K but was also correlated with the loading force range ∆F due to a typical crack tip shielding effect, i.e., plasticity-induced crack closure effect. The derived fatigue performance parameters and crack growth mechanism provide essential inputs for predictive fatigue life modeling of high-speed rail infrastructure and development of refined finite element models for fatigue analysis.