Extraction of important variables and mining of dependencies of atmospheric corrosion of carbon steel based on a comprehensive intelligent model
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摘要: 針對碳鋼在大氣腐蝕過程中影響變量多且作用機制復雜的問題,提出一種基于綜合智能模型的重要變量挖掘框架,利用該框架可以挖掘影響碳鋼早期大氣腐蝕的重要環境變量及其對腐蝕電偶電流產生的影響。本文通過大氣腐蝕監測儀(ACM)收集了我國5個試驗站點的大氣腐蝕數據,首先,構建了隨機森林(RF)、梯度提升回歸樹(GBRT)和BP神經網絡(BPNN)三種機器學習模型;其次,利用多模型集成重要變量選擇算法(MEIVS)量化環境變量的重要性并提取影響碳鋼早期大氣腐蝕的重要環境變量;最后,繪制了環境變量與腐蝕電偶電流的局部依賴曲線(PDP)。仿真結果顯示,MEIVS算法挖掘出的重要環境變量更符合大氣腐蝕的先驗規律;PDP與MEIVS算法的結論具有很好的一致性,重要環境變量對應的PDP的變化幅度大,且PDP的變化趨勢能夠反映環境變量對腐蝕電偶電流的影響。Abstract: Machine learning algorithms are widely used to predict the corrosion rate of materials in a specific environment. However, the interpretability of such black-box models is poor, which hinders their application in the field of material corrosion. Therefore, to increase algorithm transparency in practical applications, the causal relationship in the material corrosion phenomenon based on machine learning models needs to be further explored. To solve the aforementioned problems, this study analyzed the corrosion process of carbon steel in the atmosphere with many variables and complex mechanisms and proposed an important variable mining framework based on the comprehensive intelligent model. This framework can mine the important environmental variables that affect the early atmospheric corrosion of carbon steel and their influence on the corrosion galvanic current. This study collected the hour-level atmospheric corrosion data, including relative humidity, temperature, rainfall, and O3, SO2, NO2, PM2.5, and PM10 concentrations, of 45# carbon steel from five test sites in China using the atmospheric corrosion monitor of the China Meteorological Administration. To ensure the stability of the results, three machine learning models with different fitting strategies, namely, random forest, gradient boosted regression trees, and backpropagation neural network, are constructed. Then, the multimodel ensemble important variable selection (MEIVS) algorithm is used to quantify the importance of environmental variables and extract important environmental variables that severely affect the early atmospheric corrosion of carbon steel. Eventually, the partial dependence plot (PDP) of the environmental variables and corrosion galvanic current is drawn. Based on the simulation results, three significant conclusions are obtained: (1) Compared with Pearson’s and Spearman’s correlation coefficients, the important environmental variables mined using the MEIVS algorithm are more consistent with the prior law of early atmospheric corrosion of carbon steel. Relative humidity, temperature, and rainfall have the most significant impact on the early atmospheric corrosion of carbon steel, and O3 has a considerable influence on the early atmospheric corrosion of carbon steel in Sanya. Moreover, other pollutants in various regions have a weak impact on the early atmospheric corrosion of carbon steel. (2) PDP shows that, in most cases, the corrosion galvanic current of 45# carbon steel is negatively correlated with temperature and positively correlated with relative humidity. (3) PDP and MEIVS are well consistent. The simulation reveals that PDP corresponding to important environmental variables has a greater range of change, and the changing trend of PDP can reflect the influence of environmental variables on the corrosion galvanic current.
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表 1 大氣腐蝕試驗場地理和氣候信息
Table 1. Geographic and climatic information of the atmospheric corrosion test sites
Region Longitude and latitude Climate type External environment Corrosion grade Beijing 116°21′E, 39°59′N Temperate monsoon climate Country C3–C4 Hangzhou 120°30′E, 30°22′N Subtropical monsoon humid climate Industrial zone C4 Wuhan 114°15′E, 30°34′N Subtropical monsoon climate Country C3–C4 Qingdao 120°26′E, 36°04′N Temperate monsoon climate Coastal industrial zone C5–CX Sanya 109°21′E, 18°17′N Tropical marine monsoon climate Coastal industrial zone C4 表 2 三種模型在不同地區的擬合表現
Table 2. Fitting performance of the three models in different regions
Region Model Training set Testing set R2 RMSE R2 RMSE
BeijingRF 0.956 0.408 0.815 0.743 GBRT 0.878 0.679 0.788 0.795 BPNN 0.767 0.938 0.642 1.034
HangzhouRF 0.951 0.472 0.795 1.053 GBRT 0.822 0.903 0.765 1.125 BPNN 0.687 1.197 0.696 1.280
WuhanRF 0.946 0.438 0.751 1.085 GBRT 0.895 0.611 0.761 1.064 BPNN 0.727 0.986 0.700 1.191
QingdaoRF 0.952 0.620 0.756 1.381 GBRT 0.892 0.926 0.708 1.511 BPNN 0.785 1.304 0.661 1.628
SanyaRF 0.931 0.587 0.688 1.501 GBRT 0.786 1.036 0.654 1.581 BPNN 0.666 1.292 0.598 1.704 表 3 不同地區PCC和SCC分析結果
Table 3. Pearson’s and Spearman’s correlation coefficient results in different regions
Region Method Result T RH Rainfall O3 PM2.5 PM10 SO2 NO2 Beijing PCC ?0.32 0.68 0.69 ?0.08 0.24 0.21 0.11 0.11 SCC ?0.17 0.56 0.43 ?0.03 0.28 0.20 0.08 0.12 Hangzhou PCC ?0.65 0.70 0.67 ?0.25 ?0.04 ?0.06 ?0.16 0.23 SCC ?0.74 0.78 0.63 ?0.34 0.03 0.02 ?0.14 0.42 Wuhan PCC ?0.63 0.65 0.50 ?0.32 ?0.10 ?0.24 ?0.25 ?0.02 SCC ?0.73 0.73 0.36 ?0.41 ?0.16 ?0.27 ?0.36 0.01 Qingdao PCC ?0.60 0.46 0.52 ?0.15 ?0.20 0.03 ?0.24 ?0.19 SCC ?0.62 0.48 0.49 ?0.11 ?0.16 0.06 ?0.45 ?0.23 Sanya PCC ?0.53 0.59 0.51 0.07 0.03 ?0.06 ?0.02 0.10 SCC ?0.54 0.64 0.43 0.01 0.06 ?0.02 ?0.11 0.07 www.77susu.com -
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