Issue 45

X.Z. Wang, Frattura ed Integrità Strutturale, 45 (2018) 100-107; DOI: 10.3221/IGF-ESIS.45.08 105 of the prediction curve and the original data points are consistent. In different working conditions, the development trend of curves is obviously different, but they are not linear, which is closer to the actual situation. Data sequence Weight loss rate /% Serial number Time/month Close and damp Permanently soaked in water Wet and dry alternately Weak acidity aqueous soaking 1 1 0.043 9 0.660 9 0.424 4 1.140 8 2 1.5 0.060 8 0.661 4 0.497 3 1.466 2 3 2 0.074 3 0.662 2 0.563 0 1.714 7 4 2.5 0.085 1 0.663 6 0.621 4 1.904 6 5 3 0.093 8 0.665 9 0.672 4 2.049 6 6 3.5 0.100 7 0.669 6 0.716 1 2.160 4 7 4 0.106 3 0.675 8 0.752 6 2.245 0 8 4.5 0.110 8 0.685 9 0.781 7 2.309 6 9 5 0.114 4 0.702 7 0.803 6 2.359 0 10 5.5 0.117 3 0.730 3 0.818 1 2.396 7 11 6 0.119 6 0.775 8 0.825 4 2.425 5 Table 2: Data sequences modeled by GM (1,1). Corrosion envi- ronment Test 1 Test 2 Test 3 predicted value /% actual value /% error /% predicted value /% actual val- ue/% error /% predicted value /% actual val- ue/% error /% Close and damp 0.1241 0.1144 -8.48 0.1333 0.117 -13.64 0.1428 0.120 -19.40 Permanently soaked in water 0.6846 0.7027 2.32 0.6886 0.730 5.71 0.6925 0.776 10.74 Wet and dry al- ternately 0.8592 0.8036 -6.92 0.9224 0.818 -12.75 0.9902 0.825 -19.97 Weak acidity aqueous soaking 2.5547 2.359 -8.30 2.7192 2.397 -13.46 2.8912 2.426 -19.32 Table 3: Feasibility verification of grey prediction. Corrosion environment Translation value Development coef- ficient Grey influencing coef- ficients Mean accu- racy Mean stepwise ratio deviation Predicted life /a Close and damp 0.2 -0.020 7 0.263 5 0.984 0 0.014 7 8.2 Permanently soaked in water 0 -0.015 9 0.625 5 0.979 6 0.014 9 8.4 Wet and dry alternately 0 -0.049 8 0.523 4 0.956 7 0.037 3 3.2 Weak acidity aqueous soaking 1 -0.009 0 11.483 5 0.991 4 0.006 8 2.4 Table 4: Parameters and grey prediction results of GM (1,1) model. (3) From the predicted results, according to the selected weight loss rate threshold value, under the permanently soaked in water condition, the life of anchor steel bar is the longest, reaching 8.3 years; the life of anchor bar under close and damp condition is 8.2 years; the life of anchor bar under weak acidity aqueous soaking condition is the shortest, only 2.4