Compacted graphite iron(CGI)is considered to be an ideal diesel engine material with excellent physical and mechanical properties,which meet the requirements of energy conservation and emission reduction.However,knowl...Compacted graphite iron(CGI)is considered to be an ideal diesel engine material with excellent physical and mechanical properties,which meet the requirements of energy conservation and emission reduction.However,knowledge of the microstructure evolution of CGI and its impact on flow stress remains limited.In this study,a new modeling approach for the stress–strain relationship is proposed by considering the strain hardening effect and stored energy caused by the microstructure evolution of CGI.The effects of strain,strain rate,and deformation temperature on the microstructure of CGI during compression deformation are examined,including the evolution of graphite morphology and the microstructure of the pearlite matrix.The roundness and fractal dimension of graphite particles under different deformation conditions are measured.Combined with finite element simulation models,the influence of graphite particles on the flow stress of CGI is determined.The distributions of grain boundary and geometrically necessary dislocations(GNDs)density in the pearlite matrix of CGI under different strains,strain rates,and deformation temperatures are analyzed by electron backscatter diffraction technology,and the stored energy under each deformation condition is calculated.Results show that the proportion and amount of low-angle grain boundaries and the average GNDs density increase with the increase of strain and strain rate and decreased first and then increased with an increase in deformation temperature.The increase in strain and strain rate and the decrease in deformation temperature contribute to the accumulation of stored energy,which show similar variation trends to those of GNDs density.The parameters in the stress–strain relationship model are solved according to the stored energy under different deformation conditions.The consistency between the predicted results from the proposed stress–strain relationship and the experimental results shows that the evolution of stored energy can accurately predict the stress–strain relationship of CGI.展开更多
To the Editor:Iliac vein compression syndrome(IVCS)is a well-documented anatomic abnormality characterized by the compression of iliac veins from the adjacent artery and vertebra.Depending on whether deep vein thrombo...To the Editor:Iliac vein compression syndrome(IVCS)is a well-documented anatomic abnormality characterized by the compression of iliac veins from the adjacent artery and vertebra.Depending on whether deep vein thrombosis was co-existing,IVCS could be classified into thrombotic and nonthrombotic lesions.Endovascular procedures have become the mainstream treatment for nonthrombotic IVCS.[1]In most cases.展开更多
An accurate estimation of tool wear morphology can provide the opportunity to investigate the influence of tool wear on cutting performance as well as reduce the overall production cost.However,tool wear prediction is...An accurate estimation of tool wear morphology can provide the opportunity to investigate the influence of tool wear on cutting performance as well as reduce the overall production cost.However,tool wear prediction is still a very challenging research issue.In this paper,a novel method for simulating the actual chip formation and wear evolution thorough the 3 D finite element model has been carried out.In order to improve the accuracy of simulation results,the influence of worn tool,stress and temperature distribution on wear rate are considered.Then cutting experiment has been conducted by turning AISI1045 with uncoated carbide tools to validate the accuracy of the proposed model.The comparison between experimental and simulation results show good agreement which proves the ability of the proposed model in forecasting the tool wear.The validated finite element model has been further utilized studying how the worn tool affects the cutting performance including actual cutting rake,stress distribution,cutting force and temperature.The results of this paper not only provide a clear understanding of wear evolution between tool rake face and chip,but also are meaningful to optimize tool design and cutting parameters.展开更多
基金the National Natural Science Foundation of China(Grant Nos.52275464 and 52075300)the Scientific Research Project for National High-level Innovative Talents of Hebei Province Full-time Introduction,China(Grant No.2021HBQZYCXY004).
文摘Compacted graphite iron(CGI)is considered to be an ideal diesel engine material with excellent physical and mechanical properties,which meet the requirements of energy conservation and emission reduction.However,knowledge of the microstructure evolution of CGI and its impact on flow stress remains limited.In this study,a new modeling approach for the stress–strain relationship is proposed by considering the strain hardening effect and stored energy caused by the microstructure evolution of CGI.The effects of strain,strain rate,and deformation temperature on the microstructure of CGI during compression deformation are examined,including the evolution of graphite morphology and the microstructure of the pearlite matrix.The roundness and fractal dimension of graphite particles under different deformation conditions are measured.Combined with finite element simulation models,the influence of graphite particles on the flow stress of CGI is determined.The distributions of grain boundary and geometrically necessary dislocations(GNDs)density in the pearlite matrix of CGI under different strains,strain rates,and deformation temperatures are analyzed by electron backscatter diffraction technology,and the stored energy under each deformation condition is calculated.Results show that the proportion and amount of low-angle grain boundaries and the average GNDs density increase with the increase of strain and strain rate and decreased first and then increased with an increase in deformation temperature.The increase in strain and strain rate and the decrease in deformation temperature contribute to the accumulation of stored energy,which show similar variation trends to those of GNDs density.The parameters in the stress–strain relationship model are solved according to the stored energy under different deformation conditions.The consistency between the predicted results from the proposed stress–strain relationship and the experimental results shows that the evolution of stored energy can accurately predict the stress–strain relationship of CGI.
文摘To the Editor:Iliac vein compression syndrome(IVCS)is a well-documented anatomic abnormality characterized by the compression of iliac veins from the adjacent artery and vertebra.Depending on whether deep vein thrombosis was co-existing,IVCS could be classified into thrombotic and nonthrombotic lesions.Endovascular procedures have become the mainstream treatment for nonthrombotic IVCS.[1]In most cases.
基金financial support for this work by the National Natural Science Foundation of China(No.51975334)Key R&D project of Shandong Province(2018GGX103005 and 2019JMRH0407)the Fundamental Research Funds of Shandong University。
文摘An accurate estimation of tool wear morphology can provide the opportunity to investigate the influence of tool wear on cutting performance as well as reduce the overall production cost.However,tool wear prediction is still a very challenging research issue.In this paper,a novel method for simulating the actual chip formation and wear evolution thorough the 3 D finite element model has been carried out.In order to improve the accuracy of simulation results,the influence of worn tool,stress and temperature distribution on wear rate are considered.Then cutting experiment has been conducted by turning AISI1045 with uncoated carbide tools to validate the accuracy of the proposed model.The comparison between experimental and simulation results show good agreement which proves the ability of the proposed model in forecasting the tool wear.The validated finite element model has been further utilized studying how the worn tool affects the cutting performance including actual cutting rake,stress distribution,cutting force and temperature.The results of this paper not only provide a clear understanding of wear evolution between tool rake face and chip,but also are meaningful to optimize tool design and cutting parameters.
