15CrMoG耐高温合金钢Johnson-Cook本构模型建立与精度分析

Establishment and Accuracy Analysis of Johnson-Cook Constitutive Model for 15CrMoG High-temperature Resistant Alloy Steel

目的掌握不同条件下15CrMoG的高温流变规律。方法在变形温度为1173.15、1273.15、1373.15、1473.15K,应变速率为5、10、15、20s^(-1)条件下,对15CrMoG进行等温压缩实验。根据实验数据构建15CrMoG的Johnson-Cook本构模型,并对应变速率强化参数C和温度敏感系数D进行分别修正和同时修正。将修正后的3种模型预测值与实验值进行线性拟合,分别得到各模型的相关系数。引入相对误差ARE函数,计算不同条件下各模型的平均误差,通过对比得到精度较高的模型。结果15CrMoG具有温度和应变速率敏感性,高温流变曲线整体呈现先上升后平稳的趋势。拟合取值的局限性导致未修正的本构模型的精度较差。在较低变形温度下,修正后的模型均具有良好的预测精度,在高变形温度下,修正温度敏感系数的模型具有更好的适应性。3种修正模型预测值与实验值的线性相关系数均在0.9以上,具有良好的相关性。在低变形温度下,3种模型的相对误差均较小;在高变形温度下,修正温度敏感系数的Johnson-Cook模型具有较高的预测精度,最大误差为4.75%。结论对Johnson-Cook进行修正可更准确地描述15CrMoG的高温变形行为,其中修正温度敏感系数模型的误差最小,为推荐本构模型。

The work aims to grasp the high-temperature rheological law of the material under different conditions.Isother-mal compression experiments were conducted on 15CrMoG at deformation temperatures of 1173.15,1273.15,1373.15,1473.15 K,and strain rates of 5,10,15,20 s^(-1).A Johnson Cook constitutive model of 15CrMoG was constructed based on ex-perimental data,and the strain rate enhancement parameter C and the temperature sensitivity coefficient D were corrected sepa-rately and simultaneously.The predicted values of the three modified models were linearly fitted with the experimental values to obtain the correlation coefficients for each model.The relative error ARE function was introduced to calculate the average error of each model under different conditions,and obtain a model with high accuracy through comparison.The result showed that 15CrMoG was sensitive to temperature and strain rate,and the high-temperature rheological curve showed a trend of first in-crease and then stable.The uncorrected constitutive model had poor accuracy due to the limitations of fitting values.The modi-fied model had good prediction accuracy at lower deformation temperatures,while the model with a modified temperature sensi-tivity coefficient D had better adaptability at higher deformation temperatures.The linear correlation coefficients between the predicted values of the three modified models and the experimental values were all above 0.9,indicating good correlation.The relative errors of the three models were relatively small at low deformation temperatures.At high deformation temperatures,the Johnson Cook model,which corrected the temperature sensitivity coefficient D,had higher prediction accuracy,with a maxi-mum error of 4.75%.The conclusion indicates that modifying Johnson Cook can more accurately describe the high-temperature deformation behavior of 15CrMoG,with the model error of the temperature sensitivity coefficient D being the smallest,making it the recommended constitutive model.