This study investigates the impact of silicon(Si)on the corrosion resistance and post-corrosion toughness of ferrite/martensitic(F/M)steels in a liquid lead-bismuth eutectic(LBE)environment.Corrosion tests were perfor...This study investigates the impact of silicon(Si)on the corrosion resistance and post-corrosion toughness of ferrite/martensitic(F/M)steels in a liquid lead-bismuth eutectic(LBE)environment.Corrosion tests were performed on HT-9 and EP-823(1.17 wt%Si)steels at 550℃for 1000 h under oxygen-controlled conditions.The resulting oxide layer consisted of an outer magnetite layer,a spinel layer and an inner oxide zone(IOZ).A Si-rich oxide layer was identified within the spinel and IOZ layers of EP-823,which slowed the growth rate of the oxide layer,enhanced antioxidant performance,and inhibited dissolution corrosion by the LBE.Post-corrosion mechanical properties were evaluated using a small punch test.Results showed a significant reduction in HT-9's toughness within 240 h of corrosion,while EP-823 exhibited increased brittleness after 500 h due to Si-promoted carbide and Laves phase precipitation,significantly reducing its toughness.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
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
Punch shear tests have been widely used to determine rock shear mechanical properties but without a standard sample geometric dimension suggestion.To investigate the impacts of sample geometric dimensions on shear beh...Punch shear tests have been widely used to determine rock shear mechanical properties but without a standard sample geometric dimension suggestion.To investigate the impacts of sample geometric dimensions on shear behaviors in a punch shear test,simulations using Particle Flow Code were carried out.The effects of three geometric dimensions(i.e.,disk diameter,ratio of shear surface diameter to disk diameter,and ratio of disk height to shear surface diameter)were discussed.Variations of shear strength,shear stiffness,and shear dilatancy angles were studied,and the fracture processes and patterns of samples were investigated.Then,normal stress on the shear surface during test was analyzed and a suggested disk geometric dimension was given.Simulation results show that when the ratio of the shear surface diameter to the disk diameter and the ratio of disk height to the shear surface diameter is small enough,the shear strength,shear stiffness,and shear dilatancy angles are extremely sensitive to the three geometric parameters.If the ratio of surface diameter to disk diameter is too large or the ratio of disk height to surface diameter is too small,a part of the sample within the shear surface will fail due to macro tensile cracks,which is characterized by break off.Samples with a greater ratio of disk height to shear surface diameter,namely when the sample is relatively thick,crack from one end to the other while others crack from both ends towards the middle.During test,the actual normal stress on the shear surface is greater than the target value because of the extra compressive stress from the part of sample outside shear surface.展开更多
In order to evaluate the tendency of mechanical properties degrudation due to weld-ing and other processing in materials used for supporting coils in super conducting rnaguets utilized in thermonuclear jusion reactore...In order to evaluate the tendency of mechanical properties degrudation due to weld-ing and other processing in materials used for supporting coils in super conducting rnaguets utilized in thermonuclear jusion reactore, a small punch (SP) test was used.This test, which was originally developed to study irradiation damage using miniatursized specimens was performed at 77 and 4 K for solution treated and sensitized JN1 austenitic stainless steel, a candidate cryogenic structural material. The area under the load-deflection curve up to the maximum applied load in SP test was defined as the SP enerpy, to characterize the resistance to fracture. Although solution treated material exhibited ductile fracture mode with high SP enerpy, embrittlement behavior due to sensitization at 650-800°for 1-5 h was shown clearlg by SP test with brittle intergranular fracture and decreased SP enerpy. Comparison of the results obtained by SP test with those by fracture toughness test showed the usefulness of SP test for evaluation of sensitization induced embrittlement at cryogenic temperature. The re-sults obtained in this study can be very usefol in predicting the degradation due to welding and other processing in cryogenic materials.展开更多
The small punch test technique (SPT) was used to evaluate the mechanical properties of various materials and the basic method to test material tensile mechanics peqeormance from an inverse finite element ( FE) ari...The small punch test technique (SPT) was used to evaluate the mechanical properties of various materials and the basic method to test material tensile mechanics peqeormance from an inverse finite element ( FE) arithmetic with SPT was put forward. The research shows that specific tensile mechanical behavior and strain-stress distribution of each district of weld seam can be accurately determined by small punch test. Therefore, mechanical behavior of the inhomogeneous joint can be predicted by a numerical model. The simulation comes to good agreement with experimental data.展开更多
Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram(FLD) of ta...Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram(FLD) of tailor-welded blanks(TWBs) on the basis of plastic constitutive relations and Hosford yield criteria. Hemispherical punch bulging tests were performed to verify the FLD theoretical calculation results. The results demonstrated that not only the FLD theoretical calculation of base materials but also that of TWBs had a good agreement with their experiments. Besides, poorer formability of TWBs caused its FLD significantly lower than that of base materials. The theoretical calculation model offers a reliable approach to obtain the specific FLD of TWBs.展开更多
Dual equal channel lateral extrusion(DECLE)process with various passes followed by sheet extrusion process was performed to produce fine-grained ZK60 alloy sheets.The coarse grain structure of the annealed sample afte...Dual equal channel lateral extrusion(DECLE)process with various passes followed by sheet extrusion process was performed to produce fine-grained ZK60 alloy sheets.The coarse grain structure of the annealed sample after applying sheet extrusion(size:68μm)changed to fine grains of 6.0 and 5.2μm after 3 and 5 passes of DECLE and following extrusion.The hot shear deformation behavior of samples was studied by developing constitutive equations based on shear punch test(SPT)results.SPT was carried out in the temperature range of 200−300℃ and strain rate range of 0.003−0.33 s^(–1).The activation energy of 125−139 kJ/mol and the stress exponent of 3.5−4.2 were calculated for all conditions,which indicated that dislocation creep,controlled by dislocation climb and solute drag mechanism,acted as the main hot deformation mechanism.It was concluded that material constants of n and Q are dependent on the microstructural factors such as grain size and second phase particle fraction,and the relationship of which was anticipated using a 3D surface curve.Moreover,the similar strong basal texture of extruded sheets gave rise to the same deformation mechanisms during SPT and similar n and Q values for ZK60 alloy.展开更多
An innovative semisolid technique termed as vibrating cooling slope(VCS)has been applied to producing in-situ Al-25%Mg2Si(mass fraction)composite.The molten Al-16.5Mg-9.4%Si(mass fraction)alloy with 100°C superhe...An innovative semisolid technique termed as vibrating cooling slope(VCS)has been applied to producing in-situ Al-25%Mg2Si(mass fraction)composite.The molten Al-16.5Mg-9.4%Si(mass fraction)alloy with 100°C superheat was poured on the surface of an inclined copper plate(set at 45°inclined angle)while it was vibrated at a frequency of 40 Hz and an amplitude of 400μm.After travelling the length of 40 cm on the slope,the resultant semisolid alloy was cast into a steel mold.For the purpose of comparison,reference composite samples were made by gravity casting(GC)and conventionally still cooling slope casting(CS)methods using the same alloy under identical conditions.The samples were hot extruded at 500°C.It was concluded that the size of Mg2Si particles was decreased by about 50%and 70%for the CS and VCS produced samples respectively when compared to that of the GC produced sample.Despite of their higher porosity contents,both the as-cast and hot-extruded VCS processed samples exhibited higher hardness,shear yield stress(SYS)and ultimate shear strength(USS)values as compared with their GC produced counterparts.These results were attributed to the refined and modified microstructure obtained via this newly developed technique.展开更多
The shear punch test(SPT)is a suitable experiment for characterizing the shear behavior of various materials,especially where there are volume limitations.In the present investigation,the relations among various param...The shear punch test(SPT)is a suitable experiment for characterizing the shear behavior of various materials,especially where there are volume limitations.In the present investigation,the relations among various parameters such as clearance,die diameter and sample thickness,and the yield and ultimate shear strengths of AZ80Mg alloy were studied.Moreover,based on the Mohr-Coulomb theory,relatively optimum conditions were introduced for the shear punch test.With this regard,a range of2%-10%is found to be suitable for the clearance/sheet thickness ratio.To provide a simple shear stress state during a shear punch test,it is also necessary to select the die diameter/sheet thickness ratio between2:1and10:1.Based on the predictions of the Mohr-Coulomb theory,it is better to conduct a room-temperature shear punch test with a sample thickness of0.5mm,a clearance of25μm and a die diameter of2mm.Finally,the mean conversion factors to gain the tensile and compressive yield strengths of the cast AZ80from its shear one are found to be1.70and3.09,respectively.展开更多
This study investigated the effect of pressure,pre-charge time,punch velocity and oxygen content on the mechanical properties of X42 pipeline steel in gaseous hydrogen environment by using small punch test.When expose...This study investigated the effect of pressure,pre-charge time,punch velocity and oxygen content on the mechanical properties of X42 pipeline steel in gaseous hydrogen environment by using small punch test.When exposed to nitrogen,the fracture mode of X42 pipeline steel undergoes ductile fracture,but in the presence of hydrogen,it shifts to brittle fracture.Moreover,an increase in hydrogen pressure or a decrease in punch velocity is found to enhance the hydrogen embrittlement susceptibility of X42 pipeline steel,as evidenced by the decrease of maximal load,displacement at failure onset and small punch energy.But the effect of pre-charge time on the hydrogen embrittlement susceptibility of X42 pipeline steel is not very obvious.Meanwhile,the presence of oxygen has been found to effectively inhibit hydrogen embrittlement.As the oxygen content in hydrogen increases,the hydrogen embrittlement susceptibility of X42 pipeline steel decreases.展开更多
In this study, the punch resistance of the beetle forewing was investigated to address the ability of the forewing against the external force. The punch resistance of the forewing was measured for different sizes and ...In this study, the punch resistance of the beetle forewing was investigated to address the ability of the forewing against the external force. The punch resistance of the forewing was measured for different sizes and sexes of beetles using a conventional testing method in conjunction with the Digital Image Correlation (DIC) technique. The results showed that the maximum fracture load was measured around 23 N for the female beetle and around 20.2 N for the male beetle in the front-side punch test. Moreover, the fracture load in the front-side punch test was higher than that in the back-side punch test for both male and female beetles. This means that the beetle forewing plays a protection role against external loads. Furthermore, the puncture energy in the front-side punch test for the female beetle (6.91 m J) was a little higher than that for the male beetle (5.27 mJ). In addition, the DIC results revealed that the first crack occurred along the trachea line and the second crack then appeared in the direction that was perpendicular to the direction of the first crack. This study provides a com- prehensive understanding of the mechanical protection properties of the beetle forewing and offers a good lesson for studying lightweight bio-inspired composite material.展开更多
基金supported by the National Natural Science Foundation of China(No.52301121).
文摘This study investigates the impact of silicon(Si)on the corrosion resistance and post-corrosion toughness of ferrite/martensitic(F/M)steels in a liquid lead-bismuth eutectic(LBE)environment.Corrosion tests were performed on HT-9 and EP-823(1.17 wt%Si)steels at 550℃for 1000 h under oxygen-controlled conditions.The resulting oxide layer consisted of an outer magnetite layer,a spinel layer and an inner oxide zone(IOZ).A Si-rich oxide layer was identified within the spinel and IOZ layers of EP-823,which slowed the growth rate of the oxide layer,enhanced antioxidant performance,and inhibited dissolution corrosion by the LBE.Post-corrosion mechanical properties were evaluated using a small punch test.Results showed a significant reduction in HT-9's toughness within 240 h of corrosion,while EP-823 exhibited increased brittleness after 500 h due to Si-promoted carbide and Laves phase precipitation,significantly reducing its toughness.
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.
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supported by the Fundamental Research Funds for the Central Universities,CHD(Nos.300102210307,300102210308)the National Natural Science Foundation of China(Nos.51708040,41831286,51678063,51978065).
文摘Punch shear tests have been widely used to determine rock shear mechanical properties but without a standard sample geometric dimension suggestion.To investigate the impacts of sample geometric dimensions on shear behaviors in a punch shear test,simulations using Particle Flow Code were carried out.The effects of three geometric dimensions(i.e.,disk diameter,ratio of shear surface diameter to disk diameter,and ratio of disk height to shear surface diameter)were discussed.Variations of shear strength,shear stiffness,and shear dilatancy angles were studied,and the fracture processes and patterns of samples were investigated.Then,normal stress on the shear surface during test was analyzed and a suggested disk geometric dimension was given.Simulation results show that when the ratio of the shear surface diameter to the disk diameter and the ratio of disk height to the shear surface diameter is small enough,the shear strength,shear stiffness,and shear dilatancy angles are extremely sensitive to the three geometric parameters.If the ratio of surface diameter to disk diameter is too large or the ratio of disk height to surface diameter is too small,a part of the sample within the shear surface will fail due to macro tensile cracks,which is characterized by break off.Samples with a greater ratio of disk height to shear surface diameter,namely when the sample is relatively thick,crack from one end to the other while others crack from both ends towards the middle.During test,the actual normal stress on the shear surface is greater than the target value because of the extra compressive stress from the part of sample outside shear surface.
文摘In order to evaluate the tendency of mechanical properties degrudation due to weld-ing and other processing in materials used for supporting coils in super conducting rnaguets utilized in thermonuclear jusion reactore, a small punch (SP) test was used.This test, which was originally developed to study irradiation damage using miniatursized specimens was performed at 77 and 4 K for solution treated and sensitized JN1 austenitic stainless steel, a candidate cryogenic structural material. The area under the load-deflection curve up to the maximum applied load in SP test was defined as the SP enerpy, to characterize the resistance to fracture. Although solution treated material exhibited ductile fracture mode with high SP enerpy, embrittlement behavior due to sensitization at 650-800°for 1-5 h was shown clearlg by SP test with brittle intergranular fracture and decreased SP enerpy. Comparison of the results obtained by SP test with those by fracture toughness test showed the usefulness of SP test for evaluation of sensitization induced embrittlement at cryogenic temperature. The re-sults obtained in this study can be very usefol in predicting the degradation due to welding and other processing in cryogenic materials.
文摘The small punch test technique (SPT) was used to evaluate the mechanical properties of various materials and the basic method to test material tensile mechanics peqeormance from an inverse finite element ( FE) arithmetic with SPT was put forward. The research shows that specific tensile mechanical behavior and strain-stress distribution of each district of weld seam can be accurately determined by small punch test. Therefore, mechanical behavior of the inhomogeneous joint can be predicted by a numerical model. The simulation comes to good agreement with experimental data.
基金Project(51275444) supported by the National Natural Science Foundation of ChinaProject(20121333110003) supported by the Specialized Research Fund for the Doctoral Program of Higher Education,China+1 种基金Project(E2014203271) supported by the Natural Science Foundation–Steel and Iron Foundation of Hebei ProvinceChina
文摘Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram(FLD) of tailor-welded blanks(TWBs) on the basis of plastic constitutive relations and Hosford yield criteria. Hemispherical punch bulging tests were performed to verify the FLD theoretical calculation results. The results demonstrated that not only the FLD theoretical calculation of base materials but also that of TWBs had a good agreement with their experiments. Besides, poorer formability of TWBs caused its FLD significantly lower than that of base materials. The theoretical calculation model offers a reliable approach to obtain the specific FLD of TWBs.
文摘Dual equal channel lateral extrusion(DECLE)process with various passes followed by sheet extrusion process was performed to produce fine-grained ZK60 alloy sheets.The coarse grain structure of the annealed sample after applying sheet extrusion(size:68μm)changed to fine grains of 6.0 and 5.2μm after 3 and 5 passes of DECLE and following extrusion.The hot shear deformation behavior of samples was studied by developing constitutive equations based on shear punch test(SPT)results.SPT was carried out in the temperature range of 200−300℃ and strain rate range of 0.003−0.33 s^(–1).The activation energy of 125−139 kJ/mol and the stress exponent of 3.5−4.2 were calculated for all conditions,which indicated that dislocation creep,controlled by dislocation climb and solute drag mechanism,acted as the main hot deformation mechanism.It was concluded that material constants of n and Q are dependent on the microstructural factors such as grain size and second phase particle fraction,and the relationship of which was anticipated using a 3D surface curve.Moreover,the similar strong basal texture of extruded sheets gave rise to the same deformation mechanisms during SPT and similar n and Q values for ZK60 alloy.
文摘An innovative semisolid technique termed as vibrating cooling slope(VCS)has been applied to producing in-situ Al-25%Mg2Si(mass fraction)composite.The molten Al-16.5Mg-9.4%Si(mass fraction)alloy with 100°C superheat was poured on the surface of an inclined copper plate(set at 45°inclined angle)while it was vibrated at a frequency of 40 Hz and an amplitude of 400μm.After travelling the length of 40 cm on the slope,the resultant semisolid alloy was cast into a steel mold.For the purpose of comparison,reference composite samples were made by gravity casting(GC)and conventionally still cooling slope casting(CS)methods using the same alloy under identical conditions.The samples were hot extruded at 500°C.It was concluded that the size of Mg2Si particles was decreased by about 50%and 70%for the CS and VCS produced samples respectively when compared to that of the GC produced sample.Despite of their higher porosity contents,both the as-cast and hot-extruded VCS processed samples exhibited higher hardness,shear yield stress(SYS)and ultimate shear strength(USS)values as compared with their GC produced counterparts.These results were attributed to the refined and modified microstructure obtained via this newly developed technique.
文摘The shear punch test(SPT)is a suitable experiment for characterizing the shear behavior of various materials,especially where there are volume limitations.In the present investigation,the relations among various parameters such as clearance,die diameter and sample thickness,and the yield and ultimate shear strengths of AZ80Mg alloy were studied.Moreover,based on the Mohr-Coulomb theory,relatively optimum conditions were introduced for the shear punch test.With this regard,a range of2%-10%is found to be suitable for the clearance/sheet thickness ratio.To provide a simple shear stress state during a shear punch test,it is also necessary to select the die diameter/sheet thickness ratio between2:1and10:1.Based on the predictions of the Mohr-Coulomb theory,it is better to conduct a room-temperature shear punch test with a sample thickness of0.5mm,a clearance of25μm and a die diameter of2mm.Finally,the mean conversion factors to gain the tensile and compressive yield strengths of the cast AZ80from its shear one are found to be1.70and3.09,respectively.
基金supported by the National Key R&D Program of China(2021YFB4001601)the Youth Innovation Promotion Association CAS(2022187).
文摘This study investigated the effect of pressure,pre-charge time,punch velocity and oxygen content on the mechanical properties of X42 pipeline steel in gaseous hydrogen environment by using small punch test.When exposed to nitrogen,the fracture mode of X42 pipeline steel undergoes ductile fracture,but in the presence of hydrogen,it shifts to brittle fracture.Moreover,an increase in hydrogen pressure or a decrease in punch velocity is found to enhance the hydrogen embrittlement susceptibility of X42 pipeline steel,as evidenced by the decrease of maximal load,displacement at failure onset and small punch energy.But the effect of pre-charge time on the hydrogen embrittlement susceptibility of X42 pipeline steel is not very obvious.Meanwhile,the presence of oxygen has been found to effectively inhibit hydrogen embrittlement.As the oxygen content in hydrogen increases,the hydrogen embrittlement susceptibility of X42 pipeline steel decreases.
文摘In this study, the punch resistance of the beetle forewing was investigated to address the ability of the forewing against the external force. The punch resistance of the forewing was measured for different sizes and sexes of beetles using a conventional testing method in conjunction with the Digital Image Correlation (DIC) technique. The results showed that the maximum fracture load was measured around 23 N for the female beetle and around 20.2 N for the male beetle in the front-side punch test. Moreover, the fracture load in the front-side punch test was higher than that in the back-side punch test for both male and female beetles. This means that the beetle forewing plays a protection role against external loads. Furthermore, the puncture energy in the front-side punch test for the female beetle (6.91 m J) was a little higher than that for the male beetle (5.27 mJ). In addition, the DIC results revealed that the first crack occurred along the trachea line and the second crack then appeared in the direction that was perpendicular to the direction of the first crack. This study provides a com- prehensive understanding of the mechanical protection properties of the beetle forewing and offers a good lesson for studying lightweight bio-inspired composite material.