Uncertainty evaluation of plane strain fracture toughness K_1c

According to the GUM method in JJF 1059.1—2012, the uncertainty of fracture toughness K_1c of 7075-T651 aluminum alloy was evaluated. Pre-crack test conditions: stress ratio R=0.1, frequency f=20 Hz, waveform was sine wave, termination crack length a=25 mm. According to the Shapiro-Wilk test, the fracture toughness followed a normal distribution. The fracture toughness K_1c test results of 7075-T651 aluminum alloy could be expressed as K=25.3 MPa·m^0.5, U=0.9 MPa·m^0.5, k=2 and degree of freedom ν_eff=10.