采用三点弯曲实验研究应力比R对处于不同环境下的D36钢稳定裂纹扩展区疲劳裂纹扩展速率的影响。结果表明,空气中应力比对pairs区的疲劳裂纹扩展速率影响不大,然而海水环境中,在中等△K值范围内,应力比对裂纹扩展速率影响较空气中明显,...采用三点弯曲实验研究应力比R对处于不同环境下的D36钢稳定裂纹扩展区疲劳裂纹扩展速率的影响。结果表明,空气中应力比对pairs区的疲劳裂纹扩展速率影响不大,然而海水环境中,在中等△K值范围内,应力比对裂纹扩展速率影响较空气中明显,且其裂纹扩展速率随着应力比的增加而增大。这种现象产生的原因是氢脆作用随着应力比的增大显著增强。通过三电极体系在f=1 Hz,R=0.1条件下分别对试件施加-400,-600,-800,-1000和-1200 m V的电极电位。结果表明,强阴极极化(-1200 m V)和阳极极化(-400 m V)在一定△K范围内会加速裂纹扩展,综合得出该条件下腐蚀疲劳的阴极保护电位为-800 m V。而应力比为0.3和0.5时施加-800 m V的电极电位对材料的保护作用减弱。展开更多
Weld bead morphology plays an important role in welding procedure specification and welding process planning.In order to obtain the quantitative relationship between process parameters and weld morphology of DH36 mari...Weld bead morphology plays an important role in welding procedure specification and welding process planning.In order to obtain the quantitative relationship between process parameters and weld morphology of DH36 marine steel plate,grey correlation method was used to study multiple morphology characteristics simultaneously.Eighteen experimental runs were proposed according to orthogonal method.With grey correlation theory,three response objectives,aspect ratio,depth of penetration and weld were transformed into a single grey correlation grade(GRG).The process parameters were quantitatively correlated to the GRG value and optimized with the target of maximum aspect ratio,minimum depth of penetration and maximum weld area.The results show that the optimized weld bead morphology is better than other weld bead morphology.The relative error of the predicted GRG with respect to the actual value is 5.06%,which further verifies the accuracy of the established model.The microstructure and hardness analysis suggests that the optimized welded joint has obtained required mechanical properties.The research outcomes provide a theoretical basis for multi-objective optimization of arc welding morphology in practical applications.展开更多
Investigation was carried out of the crack growth rate in weld metal and heat affected zone (HAZ)of offshore structural steels,homemade steel 36Z together with foreign steel A537 of similar strength grade by compariso...Investigation was carried out of the crack growth rate in weld metal and heat affected zone (HAZ)of offshore structural steels,homemade steel 36Z together with foreign steel A537 of similar strength grade by comparison,in artificial sea water undergone fatigue with different frequencies.The crack growth rate in weld metal and HAZ of steel 36Z fatigued at low fre- queney may be 3—5 and 4—10 times as high as that at high frequency respectivley.The crack growth rate for steel 36Z may fairly match that of A537,The crack growth model and frac- ture of weld metal in corrosive medium were also discussed.展开更多
Accurate prediction of ductile fracture requires determining the material properties,including the parameters of the constitutive and ductile fracture model,which represent the true material response.Conventional cali...Accurate prediction of ductile fracture requires determining the material properties,including the parameters of the constitutive and ductile fracture model,which represent the true material response.Conventional calibration of material parameters often relies on a trial-and-error approach,in which the parameters are manually adjusted until the corresponding finite element model results in a response matching the experimental global response.The parameter estimates are often subjective.To address this issue,in this paper we treat the identification of material parameters as an optimization problem and introduce the particle swarm optimization(PSO)algorithm as the optimization approach.We provide material parameters of two uncoupled ductile fracture models—the Rice and Tracey void growth model(RT-VGM)and the micro-mechanical void growth model(MM-VGM),and a coupled model—the gurson-Tvergaard-Needleman(GTN)model for ASTM A36,A572 Gr.50,and A992 structural steels using an automated PSO method.By minimizing the difference between the experimental results and finite element simulations of the load-displacement curves for a set of tests of circumferentially notched tensile(CNT)bars,the calibration procedure automatically determines the parameters of the strain hardening law as well as the uncoupled models and the coupled GTN constitutive model.Validation studies show accurate prediction of the load-displacement response and ductile fracture initiation in V-notch specimens,and confirm the PSO algorithm as an effective and robust algorithm for seeking ductile fracture model parameters.PSO has excellent potential for identifying other fracture models(e.g.,shear modified GTN)with many parameters that can give rise to more accurate predictions of ductile fracture.Limitations of the PSO algorithm and the current calibrated ductile fracture models are also discussed in this paper.展开更多
An ionic fluid based on aromatic heterocyclic family constituted by 1,3-diazole groups was investigated. The purpose is to describe their electrochemical characteristics in order to identify the strategy to avoid the ...An ionic fluid based on aromatic heterocyclic family constituted by 1,3-diazole groups was investigated. The purpose is to describe their electrochemical characteristics in order to identify the strategy to avoid the A36 carbon steel surface degradation by using electrochemical measurements. We found that the linear polarization resistance reveals an increasing value when the organic unsaturated cyclic ionic fluid was added to the corrosive electrolyte. The polarization curves and Tafel Extrapolation obtained to know the slopes tafel and the inhibitor efficiency from current density (i<sub>corr</sub>) shows a high efficiency inhibition value.展开更多
This study aims to analyse and forecast the significance of input process parameters to obtain a better ENi-P-TiO_(2) coated surface using artificial neural networks(ANN).By varying the four process parameters with th...This study aims to analyse and forecast the significance of input process parameters to obtain a better ENi-P-TiO_(2) coated surface using artificial neural networks(ANN).By varying the four process parameters with the Taguchi L9 design,fortyfive numbers of AH36 steel specimens are coated with ENi-P-TiO_(2) composites,and their microhardness values are determined.The ANN model was formulated using the input and output data obtained from the 45 specimens.The optimal design was developed based on mean squared error(MSE)and R2 values.The experimentally measured values were compared with their predicted values to determine the ANN model’s predictability.The efficiency of the ANN model is evaluated with an R2 value of 0.959 and an MSE value of 34.5634.The authors have concluded that the developed model is suitable for designing and predicting ENi-P-TiO_(2) composite coatings to avoid extensive experimentation with economic production.Scanning Electron Microscope(SEM)and X-ray diffraction analysis(XRD)are also utilised to compare the base metal and optimal coated surface.展开更多
文摘采用三点弯曲实验研究应力比R对处于不同环境下的D36钢稳定裂纹扩展区疲劳裂纹扩展速率的影响。结果表明,空气中应力比对pairs区的疲劳裂纹扩展速率影响不大,然而海水环境中,在中等△K值范围内,应力比对裂纹扩展速率影响较空气中明显,且其裂纹扩展速率随着应力比的增加而增大。这种现象产生的原因是氢脆作用随着应力比的增大显著增强。通过三电极体系在f=1 Hz,R=0.1条件下分别对试件施加-400,-600,-800,-1000和-1200 m V的电极电位。结果表明,强阴极极化(-1200 m V)和阳极极化(-400 m V)在一定△K范围内会加速裂纹扩展,综合得出该条件下腐蚀疲劳的阴极保护电位为-800 m V。而应力比为0.3和0.5时施加-800 m V的电极电位对材料的保护作用减弱。
基金Natural Science Foundation of Fujian Province(Grant No.2020J01873)Technology Major Project of Fujian Province(Grant No.2020H03018).
文摘Weld bead morphology plays an important role in welding procedure specification and welding process planning.In order to obtain the quantitative relationship between process parameters and weld morphology of DH36 marine steel plate,grey correlation method was used to study multiple morphology characteristics simultaneously.Eighteen experimental runs were proposed according to orthogonal method.With grey correlation theory,three response objectives,aspect ratio,depth of penetration and weld were transformed into a single grey correlation grade(GRG).The process parameters were quantitatively correlated to the GRG value and optimized with the target of maximum aspect ratio,minimum depth of penetration and maximum weld area.The results show that the optimized weld bead morphology is better than other weld bead morphology.The relative error of the predicted GRG with respect to the actual value is 5.06%,which further verifies the accuracy of the established model.The microstructure and hardness analysis suggests that the optimized welded joint has obtained required mechanical properties.The research outcomes provide a theoretical basis for multi-objective optimization of arc welding morphology in practical applications.
文摘Investigation was carried out of the crack growth rate in weld metal and heat affected zone (HAZ)of offshore structural steels,homemade steel 36Z together with foreign steel A537 of similar strength grade by comparison,in artificial sea water undergone fatigue with different frequencies.The crack growth rate in weld metal and HAZ of steel 36Z fatigued at low fre- queney may be 3—5 and 4—10 times as high as that at high frequency respectivley.The crack growth rate for steel 36Z may fairly match that of A537,The crack growth model and frac- ture of weld metal in corrosive medium were also discussed.
基金the National Natural Science Foundation of China(No.51908416)the Shanghai Pujiang Program(No.19PJ1409500)the Fundamental Research Funds for the Central Universities,China。
文摘Accurate prediction of ductile fracture requires determining the material properties,including the parameters of the constitutive and ductile fracture model,which represent the true material response.Conventional calibration of material parameters often relies on a trial-and-error approach,in which the parameters are manually adjusted until the corresponding finite element model results in a response matching the experimental global response.The parameter estimates are often subjective.To address this issue,in this paper we treat the identification of material parameters as an optimization problem and introduce the particle swarm optimization(PSO)algorithm as the optimization approach.We provide material parameters of two uncoupled ductile fracture models—the Rice and Tracey void growth model(RT-VGM)and the micro-mechanical void growth model(MM-VGM),and a coupled model—the gurson-Tvergaard-Needleman(GTN)model for ASTM A36,A572 Gr.50,and A992 structural steels using an automated PSO method.By minimizing the difference between the experimental results and finite element simulations of the load-displacement curves for a set of tests of circumferentially notched tensile(CNT)bars,the calibration procedure automatically determines the parameters of the strain hardening law as well as the uncoupled models and the coupled GTN constitutive model.Validation studies show accurate prediction of the load-displacement response and ductile fracture initiation in V-notch specimens,and confirm the PSO algorithm as an effective and robust algorithm for seeking ductile fracture model parameters.PSO has excellent potential for identifying other fracture models(e.g.,shear modified GTN)with many parameters that can give rise to more accurate predictions of ductile fracture.Limitations of the PSO algorithm and the current calibrated ductile fracture models are also discussed in this paper.
文摘An ionic fluid based on aromatic heterocyclic family constituted by 1,3-diazole groups was investigated. The purpose is to describe their electrochemical characteristics in order to identify the strategy to avoid the A36 carbon steel surface degradation by using electrochemical measurements. We found that the linear polarization resistance reveals an increasing value when the organic unsaturated cyclic ionic fluid was added to the corrosive electrolyte. The polarization curves and Tafel Extrapolation obtained to know the slopes tafel and the inhibitor efficiency from current density (i<sub>corr</sub>) shows a high efficiency inhibition value.
文摘This study aims to analyse and forecast the significance of input process parameters to obtain a better ENi-P-TiO_(2) coated surface using artificial neural networks(ANN).By varying the four process parameters with the Taguchi L9 design,fortyfive numbers of AH36 steel specimens are coated with ENi-P-TiO_(2) composites,and their microhardness values are determined.The ANN model was formulated using the input and output data obtained from the 45 specimens.The optimal design was developed based on mean squared error(MSE)and R2 values.The experimentally measured values were compared with their predicted values to determine the ANN model’s predictability.The efficiency of the ANN model is evaluated with an R2 value of 0.959 and an MSE value of 34.5634.The authors have concluded that the developed model is suitable for designing and predicting ENi-P-TiO_(2) composite coatings to avoid extensive experimentation with economic production.Scanning Electron Microscope(SEM)and X-ray diffraction analysis(XRD)are also utilised to compare the base metal and optimal coated surface.
