In the present study,two-layered stainless steel-copper composites with a thickness of 50μm were initially subjected to annealing at 800,900 and 1000℃for 5 min,respectively,to achieve diverse microstructural feature...In the present study,two-layered stainless steel-copper composites with a thickness of 50μm were initially subjected to annealing at 800,900 and 1000℃for 5 min,respectively,to achieve diverse microstructural features.Then the influence of annealing temperature on the formability of stainless steel-copper composites and the quality of micro composite cups manufactured by micro deep drawing(MDD)were investigated,and the underlying mechanism was analyzed.Three finite element(FE)models,including basic FE model,Voronoi FE model and surface morphological FE model,were developed to analyze the forming performance of stainless steel-copper composites during MDD.The results show that the stainless steel-copper composites annealed at 900℃possess the best plasticity owing to the homogeneous and refined microstructure in both stainless steel and copper matrixes,and the micro composite cup with specimen annealed at 900℃exhibits a uniform wall thickness as well as high surface quality with the fewest wrinkles.The results obtained from the surface morphological FE model considering material inhomogeneity and surface morphology of the composites are the closest to the experimental results compared to the basic and Voronoi FE model.During MDD process,the drawing forces decrease with increasing annealing temperature as a consequence of the strength reduction.展开更多
As a cathode material for thermal batteries,NiS_(2)has a high theoretical capacity but low thermal stability.Besides,the poor formability of NiS_(2)powders also restricts the cathode performance of thermal batteries.I...As a cathode material for thermal batteries,NiS_(2)has a high theoretical capacity but low thermal stability.Besides,the poor formability of NiS_(2)powders also restricts the cathode performance of thermal batteries.In this paper,the novel NiS_(2)/SiO_(2)composite material was developed by high temperature vulcanization to improve the thermal stability formability of NiS_(2).The good filling and lubrication of spherical SiO_(2)can improve the thermal conductivity of NiS_(2)electrode.The discharge test shows that the NiS_(2)/SiO_(2)cathode has a stable discharge voltage at a current density of 200 mA/cm^(2),and the activation time is shortened by nearly 20%compared with the NiS_(2)cathode.In addition,due to the favorable thermal insulation protection of SiO_(2),the initial decomposition temperature of NiS_(2)is increased by 30℃after the addition of SiO_(2).The incorporation of SiO_(2)not only effectively improves the thermal stability and electrochemical properties of NiS_(2),but also improves the cold pressing forming performance of the NiS_(2)powder.Therefore,the novel NiS_(2)/SiO_(2)composite material is more suitable for thermal batteries with high stability and fast response,which is of great significance for improving the maneuverability and quality reliability of weapons and equipment.展开更多
CAB is a binder commonly utilized in CL-20-based mixed explosives.Based on the requirements of CL-20-based polymer bonded explosives in formability,safety,and detonation energy,we explored a hightoughness and low dosa...CAB is a binder commonly utilized in CL-20-based mixed explosives.Based on the requirements of CL-20-based polymer bonded explosives in formability,safety,and detonation energy,we explored a hightoughness and low dosage CAB binder system.CAB was subjected to different toughening modifications and the effects of the modified CAB binders on the bonding and coating of CL-20 crystals,as well as the formability,safety,and mechanical properties of CL-20-based polymer bonded explosive molding powder(MP)were evaluated.The changes in glass transition temperature(Tg)and mechanical properties of the modified binders were investigated using the molecular dynamics simulation at first.A series of modified binders with different molecular weights were then synthesized and characterized by FTIR,1H NMR,^(13)C NMR and SEC.The T_(g) and cross-sectional morphologies of the binder membranes were determined by DSC and SEM.The tensile properties of the binder membranes with different molecular weights and their mixtures with the plasticizer were evaluated at different temperature.With the optimized modified binder,CL-20/CAB and CL-20/CAB-g-PCL-3 MPs with the same plasticizer ratio and Cl-20/CAB-g-PCL-3 MP with a lower plasticizer ratio and higher CL-20 content were prepared and evaluated for the bonding and coating effects,crystal form,mechanical sensitivity and specific heat capacity(C_(p))by SEM,XRD,sensitivity testing and DSC,respectively.Their compressive strengths and splitting tensile strengths were measured at different temperature using a universal testing machine.Our work has provided a high-toughness and low-dosage binder system for CL-20-based MPs and offers a novel strategy to improve the formability,safety,and energy of CL-20 based polymer bonded explosives.展开更多
Based on the plastic deformation theory and energy method, the critical blank-holder forces (BHF) of wrinkling and fracture in the cylindrical cup deep-drawing are analyzed. The verify experiments were performed and c...Based on the plastic deformation theory and energy method, the critical blank-holder forces (BHF) of wrinkling and fracture in the cylindrical cup deep-drawing are analyzed. The verify experiments were performed and compared with the theory analysis results. The predictions agree well with the experiment results. Thus, the validated presenttheoretical analysis model may be applied to determinate the suitable BHF.展开更多
In this study, a novel punch toolset was developed to investigate the hot stamping of AA6082-T4 sheet. The effect of the process parameters, including forming temperature, punching velocity, friction coefficient, and ...In this study, a novel punch toolset was developed to investigate the hot stamping of AA6082-T4 sheet. The effect of the process parameters, including forming temperature, punching velocity, friction coefficient, and blank holder force(BHF) on formability was quantified using Taguchi design, analysis of variance(ANOVA) and mathematical statistics. The finite element(FE) model has been established in software Pamstamp for simulation and analysis of their effects on the minimum thickness and thickness variation of the hot-stamped component. The major factors influencing the minimum thickness of the hot-stamped part has been found to be BHF and friction coefficient with influence significance of 35.3% and 34.88%, respectively. Additionally, punch velocity and BHF affect the thickness deviation significantly with influence significance of 40.43% and 35.42%, respectively. Furthermore, a serious thinning occurs on the punch corner region of the hot-stamped cup when the BHF is larger than 2.4 kN. The thickness deviation of the hotformed cup has been found to be firstly decreased and then increased with the increase of punch velocity. Low friction coefficient between punch and blank led to crack at bottom centre of the cup. Moreover, different type, phenomenon and mechanism of defects occurring during hot stamping process, such as crack and wrinkling, were discussed. The crack mode was dimple-dominated ductile fracture, which was induced by micro-void nucleation, growth and coalescence.展开更多
基金Projects(51975398,52105392)supported by the National Natural Science Foundation of ChinaProject(YDZJSX2021A006)supported by the Central Government Guided Local Science and Technology Development Fund Project,China+1 种基金Project(20210035)supported by the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province,ChinaProject(2020-037)supported by the Fund Program for the Research Project Supported by Shanxi Scholarship Council,China。
文摘In the present study,two-layered stainless steel-copper composites with a thickness of 50μm were initially subjected to annealing at 800,900 and 1000℃for 5 min,respectively,to achieve diverse microstructural features.Then the influence of annealing temperature on the formability of stainless steel-copper composites and the quality of micro composite cups manufactured by micro deep drawing(MDD)were investigated,and the underlying mechanism was analyzed.Three finite element(FE)models,including basic FE model,Voronoi FE model and surface morphological FE model,were developed to analyze the forming performance of stainless steel-copper composites during MDD.The results show that the stainless steel-copper composites annealed at 900℃possess the best plasticity owing to the homogeneous and refined microstructure in both stainless steel and copper matrixes,and the micro composite cup with specimen annealed at 900℃exhibits a uniform wall thickness as well as high surface quality with the fewest wrinkles.The results obtained from the surface morphological FE model considering material inhomogeneity and surface morphology of the composites are the closest to the experimental results compared to the basic and Voronoi FE model.During MDD process,the drawing forces decrease with increasing annealing temperature as a consequence of the strength reduction.
基金Project(23JCYBJC01870)supported by the Natural Science Foundation of Tianjin,ChinaProject(U22A20119)supported by the National Natural Science Foundation of China。
文摘As a cathode material for thermal batteries,NiS_(2)has a high theoretical capacity but low thermal stability.Besides,the poor formability of NiS_(2)powders also restricts the cathode performance of thermal batteries.In this paper,the novel NiS_(2)/SiO_(2)composite material was developed by high temperature vulcanization to improve the thermal stability formability of NiS_(2).The good filling and lubrication of spherical SiO_(2)can improve the thermal conductivity of NiS_(2)electrode.The discharge test shows that the NiS_(2)/SiO_(2)cathode has a stable discharge voltage at a current density of 200 mA/cm^(2),and the activation time is shortened by nearly 20%compared with the NiS_(2)cathode.In addition,due to the favorable thermal insulation protection of SiO_(2),the initial decomposition temperature of NiS_(2)is increased by 30℃after the addition of SiO_(2).The incorporation of SiO_(2)not only effectively improves the thermal stability and electrochemical properties of NiS_(2),but also improves the cold pressing forming performance of the NiS_(2)powder.Therefore,the novel NiS_(2)/SiO_(2)composite material is more suitable for thermal batteries with high stability and fast response,which is of great significance for improving the maneuverability and quality reliability of weapons and equipment.
基金supported by"the Fundamental Research Funds for the Central Universities".
文摘CAB is a binder commonly utilized in CL-20-based mixed explosives.Based on the requirements of CL-20-based polymer bonded explosives in formability,safety,and detonation energy,we explored a hightoughness and low dosage CAB binder system.CAB was subjected to different toughening modifications and the effects of the modified CAB binders on the bonding and coating of CL-20 crystals,as well as the formability,safety,and mechanical properties of CL-20-based polymer bonded explosive molding powder(MP)were evaluated.The changes in glass transition temperature(Tg)and mechanical properties of the modified binders were investigated using the molecular dynamics simulation at first.A series of modified binders with different molecular weights were then synthesized and characterized by FTIR,1H NMR,^(13)C NMR and SEC.The T_(g) and cross-sectional morphologies of the binder membranes were determined by DSC and SEM.The tensile properties of the binder membranes with different molecular weights and their mixtures with the plasticizer were evaluated at different temperature.With the optimized modified binder,CL-20/CAB and CL-20/CAB-g-PCL-3 MPs with the same plasticizer ratio and Cl-20/CAB-g-PCL-3 MP with a lower plasticizer ratio and higher CL-20 content were prepared and evaluated for the bonding and coating effects,crystal form,mechanical sensitivity and specific heat capacity(C_(p))by SEM,XRD,sensitivity testing and DSC,respectively.Their compressive strengths and splitting tensile strengths were measured at different temperature using a universal testing machine.Our work has provided a high-toughness and low-dosage binder system for CL-20-based MPs and offers a novel strategy to improve the formability,safety,and energy of CL-20 based polymer bonded explosives.
基金This research was supported by the National Natural Science Foundation of China
文摘Based on the plastic deformation theory and energy method, the critical blank-holder forces (BHF) of wrinkling and fracture in the cylindrical cup deep-drawing are analyzed. The verify experiments were performed and compared with the theory analysis results. The predictions agree well with the experiment results. Thus, the validated presenttheoretical analysis model may be applied to determinate the suitable BHF.
文摘In this study, a novel punch toolset was developed to investigate the hot stamping of AA6082-T4 sheet. The effect of the process parameters, including forming temperature, punching velocity, friction coefficient, and blank holder force(BHF) on formability was quantified using Taguchi design, analysis of variance(ANOVA) and mathematical statistics. The finite element(FE) model has been established in software Pamstamp for simulation and analysis of their effects on the minimum thickness and thickness variation of the hot-stamped component. The major factors influencing the minimum thickness of the hot-stamped part has been found to be BHF and friction coefficient with influence significance of 35.3% and 34.88%, respectively. Additionally, punch velocity and BHF affect the thickness deviation significantly with influence significance of 40.43% and 35.42%, respectively. Furthermore, a serious thinning occurs on the punch corner region of the hot-stamped cup when the BHF is larger than 2.4 kN. The thickness deviation of the hotformed cup has been found to be firstly decreased and then increased with the increase of punch velocity. Low friction coefficient between punch and blank led to crack at bottom centre of the cup. Moreover, different type, phenomenon and mechanism of defects occurring during hot stamping process, such as crack and wrinkling, were discussed. The crack mode was dimple-dominated ductile fracture, which was induced by micro-void nucleation, growth and coalescence.
