Error Analysis of Image Area Percentage Measurement

Analysis of image area percentage measurement error was carried out for the measurement of porosity and residual eutectic in a single-crystal superalloy as an example. Synthesizing the experimental and theoretical analysis results, it is found that the error of the measurement results mainly comes from the image color and the color gamut range of the object to be tested. In other words, the measurement error mainly comes from whether the “boundary pixels” of the object have been defined. The measured results of porosity and residual eutectic content were obtained through experiments at different magnification multiples and color thresholds. The influence law of parameters on the two measured objects is similar. The measured value increases with the increase of the range of selected color threshold, and the change degree generally decreases with the larger magnification multiples. At a certain color threshold, the measurement results corresponding to each magnification are similar. In practical application, the effect of cognitive and other biases can be reduced by setting relatively reasonable magnification, and the efficiency and accuracy can be improved, so as to evaluate and control the error of measurement results.