A Sensitivity Study of the Unloading Compliance Single-Specimen J-Test Technique

A sensitivity analysis of the unloading compliance single-specimen J-test technique was performed to determine the effect of errors in test parameters on calculated ductile fracture toughness J_Ic values and the shape of the J-R curve. Systematic errors in measured specimen dimensions, material properties, and load and displacement transducer calibration were considered. In addition, the effect of extensometer nonlinearity on the test results was modeled. The results of the study indicate that the shape of the J-R curve and the calculated J_Ic value are relatively insensitive to errors in parameters in the magnitudes allowed by the ASTM Test Method for J_Ic, a Measure of Fracture Toughness E 813 and the Tentative Procedure for Determining the Plane Strain J₁-R curve. However, the J_Ic calculation appears to be quite sensitive to the location and spacing of J-Δa data points along the J-R curve. Means for desensitizing the J_Ic calculation to the manner in which the test is run are discussed.