Uncertainty Analysis of Plane Strain Fracture Toughness (KIC) Measurements of R350HT Rail Steels According to ASTM E399

Fracture toughness is a very important mechanical attribute that affects the strength of rail steel used in high-speed rail systems. This study tests the measurement uncertainty that comes with measuring the plane strain fracture toughness (KIC) of R350HT rail steel. We used the Single-Edge Bend (SEB) specimen to do fracture toughness testing. We used the Guide to Expressing Measurement Uncertainty (GUM)-based method to figure out how much uncertainty came from measuring the load, the crack opening displacement (COD), and the specimen’s shape and figuring out the crack length. At a 95% confidence level (k = 2), the combined standard uncertainty was found to be 0.881 MPa·m1/2, which is the same as an expanded uncertainty of 1.761 MPa·m1/2. The measured fracture toughness value of 40.59 ± 1.76 MPa·m1/2 meets the standards for rail steels. The results show how important it is to include measurement uncertainty in conformity assessment methods for safety-critical railway components. They also provide an experimentally proven framework for accurate mechanical property evaluation.