As an independent sand control unit or a common protective shell of a high-quality screen,the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and g...As an independent sand control unit or a common protective shell of a high-quality screen,the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and gas well.However,most screens only consider the influence of the internal sand retaining medium parameters in the sand control performance design while ignoring the influence of the plugging of the punching screen on the overall sand retaining performance of the screen.To explore the clogging mechanism of the punching screen,this paper established the clogging mechanism calculation model of a single punching screen sand control unit by using the computational fluid mechanics-discrete element method(CFD-DEM)combined method.According to the combined motion of particles and fluids,the influence of the internal flow state on particle motion and accumulation was analyzed.The results showed that(1)the clogging process of the punching sand control unit is divided into three stages:initial clogging,aggravation of clogging and stability of clogging.In the initial stage of blockage,coarse particles form a loose bridge structure,and blockage often occurs preferentially at the streamline gathering place below chamfering inside the sand control unit.In the stage of blockage intensification,the particle mass develops into a relatively complete sand bridge,which develops from both ends of the opening to the center of the opening.In the stable plugging stage,the sand deposits show a“fan shape”and form a“V-shaped”gully inside the punching slot element.(2)Under a certain reservoir particle-size distribution,The slit length and opening height have a large influence on the permeability and blockage rate,while the slit width size has little influence on the permeability and blockage rate.The microscopic clogging mechanism and its law of the punching screen prevention unit are proposed in this study,which has some field guidance significance for the design of punching screen and sand prevention selection.展开更多
With economic progress and the continuous advancement of science and technology,the issue of employees substituting punch cards has gradually become a significant challenge in enterprise management.The purpose of this...With economic progress and the continuous advancement of science and technology,the issue of employees substituting punch cards has gradually become a significant challenge in enterprise management.The purpose of this paper is to discuss the causes,effects,and countermeasures of the employee punch card phenomenon,with the aim of providing effective management recommendations for Chinese enterprises.In practice,enterprises should flexibly apply the countermeasures proposed in this paper according to their specific circumstances to prevent substitute punch card incidents and improve overall management efficiency.展开更多
Solid-liquid suspension in stirred tank is a common operation in the chemical industry. The power consumption, flow pattern and flow field instability of three systems named as unbaffled stirred tank, traditional baff...Solid-liquid suspension in stirred tank is a common operation in the chemical industry. The power consumption, flow pattern and flow field instability of three systems named as unbaffled stirred tank, traditional baffled stirred tank and punched baffled stirred tank(Pun-BST) were studied by using the computational fluid dynamic analysis. Results showed that perforating holes in the baffles could reduce power consumption of mixing. Meanwhile, the punched baffle system could maintain the solids in suspension as traditional baffle system. The results also showed that the baffles could increase the “effective flow” of stirred tank even though the whole velocity of the vessel is lower than un-baffled vessel. In addition, both the solid-liquid suspension and “effective flow” were related to instability of the flow field.Perfect solid-liquid suspension results always along with obvious instability of the flow field. But, the strengthening effect of punched baffle on flow field instability mainly happened in the near-wall area.It's because the collision and aggregation among sub-streams induced by holes intensified the unstable fluid flow. On the whole, the Pun-BST system provided much better mixing characteristics and recommended to apply in the industrial process.展开更多
To accurately describe the mechanical properties of aluminium alloy sheet during deformation, an inverse identification was presented to deal with material parameters from the popular punch stretch test. In the identi...To accurately describe the mechanical properties of aluminium alloy sheet during deformation, an inverse identification was presented to deal with material parameters from the popular punch stretch test. In the identification procedure, the optimization strategy combines finite element method （FEM）, Latin hypercube sampling （LHS）, Kriging model and multi-island genetic algorithm （MIGA）. The proposed approach is used on material parameter identification of aluminium alloy sheet 2D12. The anisotropic yield criterion Hill’90 is discussed. The results show that the Hill’90 anisotropic yield criterion with identified anisotropic material parameters has a good potential in describing the anisotropic behaviours. It provides a way to obtain the material parameters for FE simulations of sheet metal forming.展开更多
We previously determined 'Tableting properties' by using a multi-functional single-punch tablet press(GTP-1). We proposed plotting 'Compactability' on the x-axis against'Manufacturability' on t...We previously determined 'Tableting properties' by using a multi-functional single-punch tablet press(GTP-1). We proposed plotting 'Compactability' on the x-axis against'Manufacturability' on the y-axis to allow visual evaluation of 'Tableting properties'. Various types of tableting failure occur in commercial drug production and are influenced by the amount of lubricant used and the shape of the punch. We used the GTP-1 to measure'Tableting properties' with different amounts of lubricant and compared the results with those of tableting on a commercial rotary tableting machine. Tablets compressed with a small amount of lubricant showed bad 'Manufacturability', leading to sticking of powder on punches.We also tested various punch shapes. The GTP-1 correctly predicted the actual tableting results for all punch shapes. With punches that were more likely to cause tableting failure, our system predicted the effects of lubricant quantity in the tablet formulation and the occurrence of sticking in the rotary tableting machine.展开更多
Based on a new semi empirical analytical method, namely equivalent doping transformation, the breakdown voltage and the peak field of the epitaxial diffused punch through junction have been obtained. The basic prin...Based on a new semi empirical analytical method, namely equivalent doping transformation, the breakdown voltage and the peak field of the epitaxial diffused punch through junction have been obtained. The basic principle of this method is introduced and a set of breakdown voltage and peak field plots are provided for the optimum design of the low voltage power devices. It shows that the analytical results coincide with the previous numerical simulation well.展开更多
The servomotor drive turret punch press is attracting more attentions and being developed more intensively due to the advantages of high speed,high accuracy,high flexibility,high productivity,low noise,cleaning and en...The servomotor drive turret punch press is attracting more attentions and being developed more intensively due to the advantages of high speed,high accuracy,high flexibility,high productivity,low noise,cleaning and energy saving.To effectively improve the performance and lower the cost,it is necessary to develop new mechanisms and establish corresponding optimal design method with uniform performance indices.A new patented main driving mechanism and a new optimal design method are proposed.In the optimal design,the performance indices,i.e.,the local motion/force transmission indices ITI,OTI,good transmission workspace good transmission workspace(GTW) and the global transmission indices GTIs are defined.The non-dimensional normalization method is used to get all feasible solutions in dimensional synthesis.Thereafter,the performance atlases,which can present all possible design solutions,are depicted.As a result,the feasible solution of the mechanism with good motion/force transmission performance is obtained.And the solution can be flexibly adjusted by designer according to the practical design requirements.The proposed mechanism is original,and the presented design method provides a feasible solution to the optimal design of the main driving mechanism for servo punch press.展开更多
The microstructure evolution of spray formed and rapidly solidified Al-Cu-Mg alloy with fine grains during rapid cold punching and recrystallization annealing was investigated by transmission electron microscopy(TEM)....The microstructure evolution of spray formed and rapidly solidified Al-Cu-Mg alloy with fine grains during rapid cold punching and recrystallization annealing was investigated by transmission electron microscopy(TEM). The results show that the precipitates of fine-grained Al-Cu-Mg alloy during rapid cold punching and recrystallization annealing mainly consist of S phase and a small amount of coarse Al6Mn phase. With the increase of deformation passes, the density of precipitates increases, the size of precipitates decreases significantly, and the deformation and transition bands disappear gradually. In addition, the grains are refined and tend to be uniform. Defects introduced by rapid cold punching contribute to the precipitation and recrystallization, and promote nucleation and growth of S phase and recrystallization. Deformation and transition bands in the coarse grains transform into deformation-induced grain boundary during the deformation and recrystallization, which refine grains, obtain uniform nanocrystalline structure and promote homogeneous distribution of S phase.展开更多
High-resolution transmission electron microscopy(TEM),X-ray diffractometer(XRD),and hardness test were used to study the evolution of long plate-shaped S'phase in the spray-formed fine-grained Al−Cu−Mg alloy durin...High-resolution transmission electron microscopy(TEM),X-ray diffractometer(XRD),and hardness test were used to study the evolution of long plate-shaped S'phase in the spray-formed fine-grained Al−Cu−Mg alloy during aging after rapid cold punching deformation.Results show that the long plate-shaped S'phase in the extruded Al−Cu−Mg alloy undergoes evident distortion,brittle failure,separation and redissolution,during rapid cold punching deformation,leading to the transformation of long plate-shaped S'phase into short rod or even redissolution and disappearance,causing the matrix to become a supersaturated solid solution.After the aging treatment,the reprecipitation of the phases occurs,and these aging phases are mainly long plate-shaped and granular.The incompletely dissolved S'phase acts as nucleation core,promoting uphill diffusion of the surrounding solute atoms.The S'phase gradually grows with increasing the aging time.The completely dissolved S'phase forms the incoherent equilibrium phase with the matrix to reduce its free energy.After rapid cold punching,the aging response of the deformed Al−Cu−Mg alloy is accelerated,and the hardness of the alloy is substantially increased.展开更多
The aim of this research is to evaluate the local creep damage of various microstructures such as coarse grained heat affected zone （CGHAZ）, fine grained heat affected zone （FG- HAZ）, intercritical heat affected z...The aim of this research is to evaluate the local creep damage of various microstructures such as coarse grained heat affected zone （CGHAZ）, fine grained heat affected zone （FG- HAZ）, intercritical heat affected zone （ICHAZ） known as Type IV region, weld metal, and base metal of P92（9Cr-2W） steel weldment by small punch （SP） creep test at 600~ C. Also, to determine the weakest local part of the weldment, the effect of microstructures on creep rupture behavior in the weldment of P92 steel was studied. From the experimental results, the FGHAZ and Type IV region turned out to be very weak local parts of P92 weldment. Especially, the TYPE IV region showed the greatest displacement rate and had the shortest rupture life with many creep cavities widely spreaded in most of the region.展开更多
In order to estimate deformation and mechanical properties of material accurately,elastic and plastic deformation behavior of small punch test was discussed in this paper.A two-dimensional finite element model was est...In order to estimate deformation and mechanical properties of material accurately,elastic and plastic deformation behavior of small punch test was discussed in this paper.A two-dimensional finite element model was established based upon the Gurson-Tvergaard-Needleman(GTN)equation.According to the integration of load–displacement curves with different displacements,the evolution of elastic energy was obtained.The results show that the elastic energy increases quickly in the initial region and tends to be an approximate constant during the plastic bending phase.Meanwhile,an obvious change of the slope of load–displacement curve can be found in the elastic-plastic transition region.The macroscopic deformation and fracture feature were also discussed in order to verify the deformation analysis.Finally,the yield strength,tensile strength and elongation of AISI304 were obtained based on the analysis of deformation energy and percent fracture deflection.The results have a good agreement with that of conventional tensile tests,which may provide a theoretical basis of small punch analysis.展开更多
Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studi...Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studies have assessed the protective effect of PSP sand fences,especially through field observations.This study analyzes the effects of double-row PSP sand fences on wind and sand resistance using field observations and a computational fluid dynamics(CFD)numerical simulation.The results of field observations showed that the average windproof efficiencies of the first-row and second-row sand fences were 79.8%and 70.8%,respectively.Moreover,the average windproof efficiencies of the numerical simulation behind the first-row and second-row sand fences were 89.8%and 81.1%,respectively.The sand-resistance efficiency of the double-row PSP sand fences was 65.4%.Sand deposition occurred close to the first-row sand fence;however,there was relatively little sand on the leeward side of the second-row sand fence.The length of sand accumulation near PSP sand fences obtained by numerical simulation was basically consistent with that through field observations,indicating that field observations combined with numerical simulation can provide insight into the complex wind-blown sand field over PSP sand fences.This study indicates that the protection efficiency of the double-row PSP sand fences is sufficient for effective control of sand hazards associated with extremely strong wind in the Gobi areas.The output of this work is expected to improve the future application of PSP sand fences.展开更多
The influence of annealing on the formation of nanocrystalline of CuNi alloy surface was investigated by evaluating the microstructure, mechanical properties, and corrosion behavior of asprocessed condition （using se...The influence of annealing on the formation of nanocrystalline of CuNi alloy surface was investigated by evaluating the microstructure, mechanical properties, and corrosion behavior of asprocessed condition （using severe plastic deformation by punching process） and its annealed condition. It was observed that the microstructure changed after annealing of punched sample using an atomic force microscope. Mechanical resistance and corrosion resis tance were also characterized using nanoindentation test, electrochemical test, electron work function, and micro tribometer test. It was found that the punched and sub sequent annealed samples have increasing hardness, elastic behavior 07）, and corrosion resistance. Therefore, anneal ing can lead to the final formation of nanocrystalline and corresponding stability of grain boundary, which are responsible for the increasing mechanical properties and corrosion resistance.展开更多
Punch shearing is used to form the part in the material process.Cryogenic treatment(CT)has active effect on local mechanical properties of steel,but it is still uncertain of the influence of CT on the properties of th...Punch shearing is used to form the part in the material process.Cryogenic treatment(CT)has active effect on local mechanical properties of steel,but it is still uncertain of the influence of CT on the properties of the magnesium alloy during punch shearing.In this work,the influence of AZ31 sheet treated by cryogenic on punch shearing was studied.Microstructures were observed with a ZEISS optical microscope,and mechanical properties,as well as shear properties were tested by tensile testing and punch shearing.The results show that the number of secondary phase increases and a large number of twins appear in the grains after CT.Meanwhile,the ultimate tensile strength(UTS),the ductility,and hardness of AZ31 are improved,while the yield strength(YS)decreases gradually during CT.During punch shearing,the shearing strength decreases,the rollover radius changes insignificantly,and the height of the burr on the edge of the cross section decreases.At the same time,a larger proportion of smooth zone on the cross section has been achieved.展开更多
To reduce the noise of the punch press during the punching process, the polyurethane elastomer is used as the damping material. The experiments of reducing noise were made by means of adding the polyurethane elastomer...To reduce the noise of the punch press during the punching process, the polyurethane elastomer is used as the damping material. The experiments of reducing noise were made by means of adding the polyurethane elastomer at different positions on the 100 kN and 1 000 kN punch presses. The better effect of reducing noise was obtained. After researching and analyzing a large number of test data, the ″equivalent damping hypothesis″ is put forward. The hypothesis makes the experiment of reducing noise simpler and also more economical. It is estimated that there is a vast application in the research area of vibration control and noise reduction.展开更多
Ion beam irradiation was adopted for surface treatment of the micro punch manufactured by precision machining.Ar plasma was used for the ion irradiation process,which was generated by the electron cyclotron resonance(...Ion beam irradiation was adopted for surface treatment of the micro punch manufactured by precision machining.Ar plasma was used for the ion irradiation process,which was generated by the electron cyclotron resonance(ECR)equipment.The surface finish processes of micro punch were carried out at irradiation angles of 45°and 10°,respectively.The surface roughness and topography were measured to estimate the quality of surface finish.The results show that the ion irradiation is very effective to reduce the surface roughness,which can be improved more significantly at irradiation angle of 10°than at 45°.The technology of surface finish with ion beam irradiation is suitable for the surface treatment of micro die.展开更多
The contact problem for thermoelectric materials with functionally graded properties is considered.The material properties,such as the electric conductivity,the thermal conductivity,the shear modulus,and the thermal e...The contact problem for thermoelectric materials with functionally graded properties is considered.The material properties,such as the electric conductivity,the thermal conductivity,the shear modulus,and the thermal expansion coefficient,vary in an exponential function.Using the Fourier transform technique,the electro-thermoelastic problems are transformed into three sets of singular integral equations which are solved numerically in terms of the unknown normal electric current density,the normal energy flux,and the contact pressure.Meanwhile,the complex homogeneous solutions of the displacement fields caused by the gradient parameters are simplified with the help of Euler’s formula.After addressing the non-linearity excited by thermoelectric effects,the particular solutions of the displacement fields can be assessed.The effects of various combinations of material gradient parameters and thermoelectric loads on the contact behaviors of thermoelectric materials are presented.The results give a deep insight into the contact damage mechanism of functionally graded thermoelectric materials(FGTEMs).展开更多
Spudcan may experience punch-through failure on strong over weak layered soils, such as sand overlying clay. A large deformation finite element method （LDFE） is used to simulate the penetration process of spudcan in...Spudcan may experience punch-through failure on strong over weak layered soils, such as sand overlying clay. A large deformation finite element method （LDFE） is used to simulate the penetration process of spudcan into sand overlying clay. The sand is simulated by smoothed hyperbolic Mohr-Coulomb model, and the clay is simulated by a simple elasto-plastic model which obeys Tresca yield criterion. According to the LDFE results of a large amount of cases, the effects of the strength, unit weight and thickness of the top sand layer, as well as the effect of the strength of the underlying clay on the spudcan punch-through behavior, are investigated. The critical depth occurring punch-through and the critical bearing capacity are presented in charts. Fitting equations to calculate the critical punch-through depth and the critical bearing capacity are proposed for the convenience of engineering practice.展开更多
文摘As an independent sand control unit or a common protective shell of a high-quality screen,the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and gas well.However,most screens only consider the influence of the internal sand retaining medium parameters in the sand control performance design while ignoring the influence of the plugging of the punching screen on the overall sand retaining performance of the screen.To explore the clogging mechanism of the punching screen,this paper established the clogging mechanism calculation model of a single punching screen sand control unit by using the computational fluid mechanics-discrete element method(CFD-DEM)combined method.According to the combined motion of particles and fluids,the influence of the internal flow state on particle motion and accumulation was analyzed.The results showed that(1)the clogging process of the punching sand control unit is divided into three stages:initial clogging,aggravation of clogging and stability of clogging.In the initial stage of blockage,coarse particles form a loose bridge structure,and blockage often occurs preferentially at the streamline gathering place below chamfering inside the sand control unit.In the stage of blockage intensification,the particle mass develops into a relatively complete sand bridge,which develops from both ends of the opening to the center of the opening.In the stable plugging stage,the sand deposits show a“fan shape”and form a“V-shaped”gully inside the punching slot element.(2)Under a certain reservoir particle-size distribution,The slit length and opening height have a large influence on the permeability and blockage rate,while the slit width size has little influence on the permeability and blockage rate.The microscopic clogging mechanism and its law of the punching screen prevention unit are proposed in this study,which has some field guidance significance for the design of punching screen and sand prevention selection.
文摘With economic progress and the continuous advancement of science and technology,the issue of employees substituting punch cards has gradually become a significant challenge in enterprise management.The purpose of this paper is to discuss the causes,effects,and countermeasures of the employee punch card phenomenon,with the aim of providing effective management recommendations for Chinese enterprises.In practice,enterprises should flexibly apply the countermeasures proposed in this paper according to their specific circumstances to prevent substitute punch card incidents and improve overall management efficiency.
基金supported by the National Natural Science Foundation of China (22078030, Z20200804)National Key Research and Development Program of China (2019YFC1905802)+1 种基金Key Project of Independent Research Project of State Key Laboratory of Coal Mine Disaster Dynamics and Control (2011DA105287zd201902)Hubei Three Gorges Laboratory Open/Innovation Fund (SK211009, SK215001)。
文摘Solid-liquid suspension in stirred tank is a common operation in the chemical industry. The power consumption, flow pattern and flow field instability of three systems named as unbaffled stirred tank, traditional baffled stirred tank and punched baffled stirred tank(Pun-BST) were studied by using the computational fluid dynamic analysis. Results showed that perforating holes in the baffles could reduce power consumption of mixing. Meanwhile, the punched baffle system could maintain the solids in suspension as traditional baffle system. The results also showed that the baffles could increase the “effective flow” of stirred tank even though the whole velocity of the vessel is lower than un-baffled vessel. In addition, both the solid-liquid suspension and “effective flow” were related to instability of the flow field.Perfect solid-liquid suspension results always along with obvious instability of the flow field. But, the strengthening effect of punched baffle on flow field instability mainly happened in the near-wall area.It's because the collision and aggregation among sub-streams induced by holes intensified the unstable fluid flow. On the whole, the Pun-BST system provided much better mixing characteristics and recommended to apply in the industrial process.
基金Project(2011YSKF01)supported by the Henan Key Laboratory of Advanced Non-ferrous Metals,ChinaProject(50905008)supported by the National Natural Science Foundation of China
文摘To accurately describe the mechanical properties of aluminium alloy sheet during deformation, an inverse identification was presented to deal with material parameters from the popular punch stretch test. In the identification procedure, the optimization strategy combines finite element method （FEM）, Latin hypercube sampling （LHS）, Kriging model and multi-island genetic algorithm （MIGA）. The proposed approach is used on material parameter identification of aluminium alloy sheet 2D12. The anisotropic yield criterion Hill’90 is discussed. The results show that the Hill’90 anisotropic yield criterion with identified anisotropic material parameters has a good potential in describing the anisotropic behaviours. It provides a way to obtain the material parameters for FE simulations of sheet metal forming.
文摘We previously determined 'Tableting properties' by using a multi-functional single-punch tablet press(GTP-1). We proposed plotting 'Compactability' on the x-axis against'Manufacturability' on the y-axis to allow visual evaluation of 'Tableting properties'. Various types of tableting failure occur in commercial drug production and are influenced by the amount of lubricant used and the shape of the punch. We used the GTP-1 to measure'Tableting properties' with different amounts of lubricant and compared the results with those of tableting on a commercial rotary tableting machine. Tablets compressed with a small amount of lubricant showed bad 'Manufacturability', leading to sticking of powder on punches.We also tested various punch shapes. The GTP-1 correctly predicted the actual tableting results for all punch shapes. With punches that were more likely to cause tableting failure, our system predicted the effects of lubricant quantity in the tablet formulation and the occurrence of sticking in the rotary tableting machine.
文摘Based on a new semi empirical analytical method, namely equivalent doping transformation, the breakdown voltage and the peak field of the epitaxial diffused punch through junction have been obtained. The basic principle of this method is introduced and a set of breakdown voltage and peak field plots are provided for the optimum design of the low voltage power devices. It shows that the analytical results coincide with the previous numerical simulation well.
基金supported by National Natural Science Foundation of China(Grant No.51021064)National Key Scientific and Technological Program of China(Grant No.2010ZX04004-116)
文摘The servomotor drive turret punch press is attracting more attentions and being developed more intensively due to the advantages of high speed,high accuracy,high flexibility,high productivity,low noise,cleaning and energy saving.To effectively improve the performance and lower the cost,it is necessary to develop new mechanisms and establish corresponding optimal design method with uniform performance indices.A new patented main driving mechanism and a new optimal design method are proposed.In the optimal design,the performance indices,i.e.,the local motion/force transmission indices ITI,OTI,good transmission workspace good transmission workspace(GTW) and the global transmission indices GTIs are defined.The non-dimensional normalization method is used to get all feasible solutions in dimensional synthesis.Thereafter,the performance atlases,which can present all possible design solutions,are depicted.As a result,the feasible solution of the mechanism with good motion/force transmission performance is obtained.And the solution can be flexibly adjusted by designer according to the practical design requirements.The proposed mechanism is original,and the presented design method provides a feasible solution to the optimal design of the main driving mechanism for servo punch press.
基金Project(2019JJ60050)supported by the Natural Science Foundation of Hunan Province,China
文摘The microstructure evolution of spray formed and rapidly solidified Al-Cu-Mg alloy with fine grains during rapid cold punching and recrystallization annealing was investigated by transmission electron microscopy(TEM). The results show that the precipitates of fine-grained Al-Cu-Mg alloy during rapid cold punching and recrystallization annealing mainly consist of S phase and a small amount of coarse Al6Mn phase. With the increase of deformation passes, the density of precipitates increases, the size of precipitates decreases significantly, and the deformation and transition bands disappear gradually. In addition, the grains are refined and tend to be uniform. Defects introduced by rapid cold punching contribute to the precipitation and recrystallization, and promote nucleation and growth of S phase and recrystallization. Deformation and transition bands in the coarse grains transform into deformation-induced grain boundary during the deformation and recrystallization, which refine grains, obtain uniform nanocrystalline structure and promote homogeneous distribution of S phase.
基金financially supported by the Major Special Projects in Anhui Province,China(No.202003c08020005)the Key Projects in Hunan Province,China(No.2020GK2045).
文摘High-resolution transmission electron microscopy(TEM),X-ray diffractometer(XRD),and hardness test were used to study the evolution of long plate-shaped S'phase in the spray-formed fine-grained Al−Cu−Mg alloy during aging after rapid cold punching deformation.Results show that the long plate-shaped S'phase in the extruded Al−Cu−Mg alloy undergoes evident distortion,brittle failure,separation and redissolution,during rapid cold punching deformation,leading to the transformation of long plate-shaped S'phase into short rod or even redissolution and disappearance,causing the matrix to become a supersaturated solid solution.After the aging treatment,the reprecipitation of the phases occurs,and these aging phases are mainly long plate-shaped and granular.The incompletely dissolved S'phase acts as nucleation core,promoting uphill diffusion of the surrounding solute atoms.The S'phase gradually grows with increasing the aging time.The completely dissolved S'phase forms the incoherent equilibrium phase with the matrix to reduce its free energy.After rapid cold punching,the aging response of the deformed Al−Cu−Mg alloy is accelerated,and the hardness of the alloy is substantially increased.
基金supported by KESRI(R-2005-7-021),which is funded by MOICE(Ministry of Commerce,Industry and Energy).
文摘The aim of this research is to evaluate the local creep damage of various microstructures such as coarse grained heat affected zone （CGHAZ）, fine grained heat affected zone （FG- HAZ）, intercritical heat affected zone （ICHAZ） known as Type IV region, weld metal, and base metal of P92（9Cr-2W） steel weldment by small punch （SP） creep test at 600~ C. Also, to determine the weakest local part of the weldment, the effect of microstructures on creep rupture behavior in the weldment of P92 steel was studied. From the experimental results, the FGHAZ and Type IV region turned out to be very weak local parts of P92 weldment. Especially, the TYPE IV region showed the greatest displacement rate and had the shortest rupture life with many creep cavities widely spreaded in most of the region.
基金Project(2012AA040105)supported by National High-technology Research and Development of China
文摘In order to estimate deformation and mechanical properties of material accurately,elastic and plastic deformation behavior of small punch test was discussed in this paper.A two-dimensional finite element model was established based upon the Gurson-Tvergaard-Needleman(GTN)equation.According to the integration of load–displacement curves with different displacements,the evolution of elastic energy was obtained.The results show that the elastic energy increases quickly in the initial region and tends to be an approximate constant during the plastic bending phase.Meanwhile,an obvious change of the slope of load–displacement curve can be found in the elastic-plastic transition region.The macroscopic deformation and fracture feature were also discussed in order to verify the deformation analysis.Finally,the yield strength,tensile strength and elongation of AISI304 were obtained based on the analysis of deformation energy and percent fracture deflection.The results have a good agreement with that of conventional tensile tests,which may provide a theoretical basis of small punch analysis.
基金This research was funded by the Fellowship of the China Postdoctoral Science Foundation(2021M703466)the Basic Research Innovation Group Project of Gansu Province,China(21JR7RA347)the Natural Science Foundation of Gansu Province,China(20JR10RA231).
文摘Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studies have assessed the protective effect of PSP sand fences,especially through field observations.This study analyzes the effects of double-row PSP sand fences on wind and sand resistance using field observations and a computational fluid dynamics(CFD)numerical simulation.The results of field observations showed that the average windproof efficiencies of the first-row and second-row sand fences were 79.8%and 70.8%,respectively.Moreover,the average windproof efficiencies of the numerical simulation behind the first-row and second-row sand fences were 89.8%and 81.1%,respectively.The sand-resistance efficiency of the double-row PSP sand fences was 65.4%.Sand deposition occurred close to the first-row sand fence;however,there was relatively little sand on the leeward side of the second-row sand fence.The length of sand accumulation near PSP sand fences obtained by numerical simulation was basically consistent with that through field observations,indicating that field observations combined with numerical simulation can provide insight into the complex wind-blown sand field over PSP sand fences.This study indicates that the protection efficiency of the double-row PSP sand fences is sufficient for effective control of sand hazards associated with extremely strong wind in the Gobi areas.The output of this work is expected to improve the future application of PSP sand fences.
基金supported by the Scientific Research Startup Foundation of Nanjing Institute of Technology for Introducing Talents(No.YKJ201008)the Industrialization of Scientific Research Promotion Projects of Colleges and Universities in Jiangsu Province(No.JHB2011-25)Innovation Foundation of Nanjing Institute of Technology(No.CKJB201206)
文摘The influence of annealing on the formation of nanocrystalline of CuNi alloy surface was investigated by evaluating the microstructure, mechanical properties, and corrosion behavior of asprocessed condition （using severe plastic deformation by punching process） and its annealed condition. It was observed that the microstructure changed after annealing of punched sample using an atomic force microscope. Mechanical resistance and corrosion resis tance were also characterized using nanoindentation test, electrochemical test, electron work function, and micro tribometer test. It was found that the punched and sub sequent annealed samples have increasing hardness, elastic behavior 07）, and corrosion resistance. Therefore, anneal ing can lead to the final formation of nanocrystalline and corresponding stability of grain boundary, which are responsible for the increasing mechanical properties and corrosion resistance.
基金Projects(51275201,51311130129)supported by the National Natural Science of ChinaProject(20140204062GX)supported by the Jilin Key Scientific and Technological Project,China
文摘Punch shearing is used to form the part in the material process.Cryogenic treatment(CT)has active effect on local mechanical properties of steel,but it is still uncertain of the influence of CT on the properties of the magnesium alloy during punch shearing.In this work,the influence of AZ31 sheet treated by cryogenic on punch shearing was studied.Microstructures were observed with a ZEISS optical microscope,and mechanical properties,as well as shear properties were tested by tensile testing and punch shearing.The results show that the number of secondary phase increases and a large number of twins appear in the grains after CT.Meanwhile,the ultimate tensile strength(UTS),the ductility,and hardness of AZ31 are improved,while the yield strength(YS)decreases gradually during CT.During punch shearing,the shearing strength decreases,the rollover radius changes insignificantly,and the height of the burr on the edge of the cross section decreases.At the same time,a larger proportion of smooth zone on the cross section has been achieved.
文摘To reduce the noise of the punch press during the punching process, the polyurethane elastomer is used as the damping material. The experiments of reducing noise were made by means of adding the polyurethane elastomer at different positions on the 100 kN and 1 000 kN punch presses. The better effect of reducing noise was obtained. After researching and analyzing a large number of test data, the ″equivalent damping hypothesis″ is put forward. The hypothesis makes the experiment of reducing noise simpler and also more economical. It is estimated that there is a vast application in the research area of vibration control and noise reduction.
基金Project(2006AA04Z331)supported by the Hi-tech Research and Development Program of ChinaProject(50835002)supported by theKey Program of the National Natural Science Foundation of ChinaProject(JC-06-07)supported by the Science Foundation for Distinguished Young Scholars of Heilongjiang Province,China。
文摘Ion beam irradiation was adopted for surface treatment of the micro punch manufactured by precision machining.Ar plasma was used for the ion irradiation process,which was generated by the electron cyclotron resonance(ECR)equipment.The surface finish processes of micro punch were carried out at irradiation angles of 45°and 10°,respectively.The surface roughness and topography were measured to estimate the quality of surface finish.The results show that the ion irradiation is very effective to reduce the surface roughness,which can be improved more significantly at irradiation angle of 10°than at 45°.The technology of surface finish with ion beam irradiation is suitable for the surface treatment of micro die.
基金supported by the National Natural Science Foundation of China(Nos.11972257,11832014,11762016,11472193)the Fundamental Research Funds for the Central Universities(No.22120180223)。
文摘The contact problem for thermoelectric materials with functionally graded properties is considered.The material properties,such as the electric conductivity,the thermal conductivity,the shear modulus,and the thermal expansion coefficient,vary in an exponential function.Using the Fourier transform technique,the electro-thermoelastic problems are transformed into three sets of singular integral equations which are solved numerically in terms of the unknown normal electric current density,the normal energy flux,and the contact pressure.Meanwhile,the complex homogeneous solutions of the displacement fields caused by the gradient parameters are simplified with the help of Euler’s formula.After addressing the non-linearity excited by thermoelectric effects,the particular solutions of the displacement fields can be assessed.The effects of various combinations of material gradient parameters and thermoelectric loads on the contact behaviors of thermoelectric materials are presented.The results give a deep insight into the contact damage mechanism of functionally graded thermoelectric materials(FGTEMs).
基金supported by the National Natural Science Foundation of China(Grant Nos.50978045,51121005 and 51209033)
文摘Spudcan may experience punch-through failure on strong over weak layered soils, such as sand overlying clay. A large deformation finite element method （LDFE） is used to simulate the penetration process of spudcan into sand overlying clay. The sand is simulated by smoothed hyperbolic Mohr-Coulomb model, and the clay is simulated by a simple elasto-plastic model which obeys Tresca yield criterion. According to the LDFE results of a large amount of cases, the effects of the strength, unit weight and thickness of the top sand layer, as well as the effect of the strength of the underlying clay on the spudcan punch-through behavior, are investigated. The critical depth occurring punch-through and the critical bearing capacity are presented in charts. Fitting equations to calculate the critical punch-through depth and the critical bearing capacity are proposed for the convenience of engineering practice.
