C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high...C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high density of 0.94 g/cm3 as preform.Experimental results indicated that the fracture characteristics of C/C composites were closely related to the frequency of high-temperature treatment（HTT） at the break of CVI process.According to the load？displacement curves,C/C composites showed a pseudoplastic fracture after twice of HTT.After three times of HTT,load？displacement curves tended to be stable with a decreasing bending strength at 177.5 MPa.Delamination failure and intrastratal fiber fracture were observed at the cross-section of C/C composites by scanning electronic microscope.Because the content of pyrocarbon and fibers has a different distribution in layers,the C/C composites show different fracture characteristics at various regions,which leads to good toughness and bending strength.展开更多
To analyze the bending properties of GCr15 steel guide rail based on the elastic-plastic theory, the novel bending loading method consisting of multi-step loading and corresponding unloading was applied in three speci...To analyze the bending properties of GCr15 steel guide rail based on the elastic-plastic theory, the novel bending loading method consisting of multi-step loading and corresponding unloading was applied in three specimens with different cross section shape and different heat treatment condition. According to the experimental results, using numerical calculation software program and the numerical simulation with finite element analysis （FEA）, the relationships among the maximal load and displacement on cross section shape with each step bend loading, the loading stroke with the heat treatment condition, and the loading stroke with cross section shape were gained, and also those curves were discussed qualitatively. Finally, the contrast results between the numerical simulation and experiment were carried out to study the influence about the multi-step loading on specimen. It is put forward that enlightenment for the straightening stroke in the precision linear guide rail manufacture process.展开更多
Connection plays an important role in structural components and end jointing is one of the most common connections in structural applications. This study was designed to investigate some mechanical properties （MOE an...Connection plays an important role in structural components and end jointing is one of the most common connections in structural applications. This study was designed to investigate some mechanical properties （MOE and MOR） of solid wood samples manufactured from poplar （Populus nigra）, joined together through end jointing. As well, we studied combinations of lumber manufactured from 10-mm veneer, using a polyvinyl acetate adhesive. The results show that non-jointed lumber （control samples） have better bending properties （MOE and MOR） than jointed specimens and lumber made from laminated layers. On the whole, side-by- side joints have a negative effect on the MOR and MOE of laminated products, which is more pronounced in the MOR. By increasing the number of joints, the properties of combination of three-ply, i.e., bending strength and modulus of elasticity, decreased.展开更多
A NiTi@Mg interpenetrating phase composite with high strength and lightweight was prepared by additive manufacturing(AM)and infiltration technology,and the interface bonding,three-point bending properties and cyclic c...A NiTi@Mg interpenetrating phase composite with high strength and lightweight was prepared by additive manufacturing(AM)and infiltration technology,and the interface bonding,three-point bending properties and cyclic compressive properties of NiTi@Mg composites were investigated.The results show that the metallurgically bonded interface is formed at the NiTi/Mg interfaces.The bending strength and compressive strength of the NiTi@Mg composite are 2.5 and 1.7 times higher than those of the NiTi scaffold,respectively.During the bending deformation process,a large number of dislocations are observed to accumulate in the soft Mg area at the interface.Furthermore,the finite element model showed that the stress accumulation area,where the bending crack is initiated,is located at the interface of NiTi and Mg.The strengthening mechanism of NiTi@Mg composites is attributed to the twinning strengthening of Mg and heterogeneous structure strengthening.展开更多
To improve the mechanical properties of Trabecular Beetle Elytron Plates(TBEPs,a type of biomimetic sandwich structure inspired by the beetle elytron)under transverse loads,three-point bending tests are performed to i...To improve the mechanical properties of Trabecular Beetle Elytron Plates(TBEPs,a type of biomimetic sandwich structure inspired by the beetle elytron)under transverse loads,three-point bending tests are performed to investigate the influence of the trabecular and chamfer radii of the core structure on the mechanical performance of TBEPs manufactured by 3D printing technology.The results show that the three-point bending performance of TBEPs can be improved by setting reasonable trabecular and chamfer radii;however,excessive increases in these radii can cause a decline in the mechanical performance.For the reason,these two structural parameters can enhance the deformation stiffness of the whole structure and the connection property between the core and skin,which is also the mechanical reason why Prosopocoilus inclinatus beetle elytra have thick,short trabeculae with a large chamfer radius.However,when these radii increase to a certain extent,the cracks are ultimately controlled between two adjacent trabeculae,and the failure of the plate is determined by the skin rather than the core structure.Therefore,this study suggests a reasonable range for trabecular and chamfer radii,and indicates that TBEPs are better suited for engineering applications that have high compression requirements and general bending requirements.展开更多
[ Objective] The aim is to research the relationship between bending property and density of wheat stem. [ Method ] The bending properties such as elastic modulus, bending strength, flexural rigidity, moment of inerti...[ Objective] The aim is to research the relationship between bending property and density of wheat stem. [ Method ] The bending properties such as elastic modulus, bending strength, flexural rigidity, moment of inertia, density and water content of the second base internodes of Zhengmai 9023 and Yumai 25 were determined. [ Result] The results show that during filling stage, there are significant differences in the elastic modulus, moment of inertia, flexural rigidity and density among wheat varieties, while there are no significant differences in the bending strength and water content among wheat varieties. The moment of inertia, flexural strength and flexural rigidity have positive relationship to density but negative relationship to water content. [ Conclusion] The study results provide some references for the research on high yield cultivation and lodging resistance of wheat.展开更多
Recent progress in production process for advanced high strength steel sheets（AHSS） is described focussing on Bainitic ferrite steel,transformation induced plasticity（TRIP） steel and precipitation hardened steel b...Recent progress in production process for advanced high strength steel sheets（AHSS） is described focussing on Bainitic ferrite steel,transformation induced plasticity（TRIP） steel and precipitation hardened steel by NANO sized precipitates are reviewed. In higher tensile strength（TS） grade,elongation（El）,hole expansion ratio（λ） and their balance are eagerly requested to improve by customers.Bainitic ferrite steel which has shear deformed lath with various distribution of iron carbides and retained austenite should be distinguished to produce different balance of El/λ. Chemical composition and heat cycle are reviewed to produce various kinds of metallurgical phase and mechanical property.5%Mn -2%Si TRIP steel is introduced in which a plenty of retained austenite at about 30%and larger absorbed energy（AE） more than 3 000 kgf/mm;TS·%El（gauge length:50 mm） can be obtained. That steel also showed excellent upper shelf energy in Charpy test of 140 J/cm;,as well as excellent property of 20%El and 1 400 MPa TS after forging. A new type of precipitation hardened steel having NANO sized（Ti,Mo） C in ferrite matrix is introduced.It satisfies the both of excellent El andλat the same time. Bending property and holes expansion property obey the same kind of deforming criteria which depends on the forming capability of work hardened parts.Homogeneity of structure is their controlling factor and a new parameterαwhich is obtained by gauge length dependency of total elongation is proposed.展开更多
The AZ31 and AM60 alloys were used for dissimilar friction stir welding(FSW)in this study.The microstructure characteristics of the joint and its three-point bending performance were investigated.The electron backscat...The AZ31 and AM60 alloys were used for dissimilar friction stir welding(FSW)in this study.The microstructure characteristics of the joint and its three-point bending performance were investigated.The electron backscattered diffraction results showed that the grains in the nugget zone(NZ)were more uniform and refined to a certain extent after FSW,but the grain size of AM60 in the NZ was larger than that of AZ31.The texture was strong locally in the NZ and presented a symmetric distribution characteristic from the advancing side to the retreating side.There were special texture features in the joint,resulting in the occurrence of severe strain localization during the bending process compared with the base materials,which can be well explained by the calculated Schmid factor in terms of the assumed stress state for bending.The bending tests revealed that the joint presented good bending properties compared with AZ31 BM.The bending fracture morphologies suggested that the fracture tended to the NZ interface on the AZ31 side,which was mainly due to the higher SF for basal slip and dislocation concentration degree in the region,and the relatively lower bending strength of AZ31 metal.展开更多
We investigated the resistance of acetylated rattan against soft rot and other soil inhabiting micro-organisms in comparison with wood of beech and Scots pine. Calamus manan of 10 and 13 years old under rubber tree ca...We investigated the resistance of acetylated rattan against soft rot and other soil inhabiting micro-organisms in comparison with wood of beech and Scots pine. Calamus manan of 10 and 13 years old under rubber tree canopy was acetylated to different levels by reaction times （0.25 to 30 hours） and was tested for soft rot decay for 32 weeks. Acetylated rattan at decay protection thresholds of 15.4% and 16.2% weight gain （WG） were fully protected, as shown by both weight loss and strength loss criteria. The static bending properties of untreated rattan decayed by soft rot were significantly lower than for acetylated rattan.展开更多
Al/Mg alloy multilayered composites were produced successfully at the lower temperature（280 C） by accumulative roll bonding（ARB） processing technique.The microstructures of Al and Mg alloy layers were characterize...Al/Mg alloy multilayered composites were produced successfully at the lower temperature（280 C） by accumulative roll bonding（ARB） processing technique.The microstructures of Al and Mg alloy layers were characterized by scanning electron microscopy and transmission electron microscopy.Vickers hardness and three-point bending tests were conducted to investigate mechanical properties of the composites.It is found that Vickers hardness,bending strength and stiffness modulus of the Al/Mg alloy multilayered composite increase with increasing the ARB pass.Delamination and crack propagation along the interface are the two main failure modes of the multilayered composite subjected to bending load.Strengthening and fracture mechanisms of the composite are analyzed.展开更多
With the purpose of improving both the strength and ductility,gradient equiaxed grains were successfully achieved in the matrix of the laminated TiB/Ti-TiB/Ti-6.58Al-1.76Zr-1.04V-0.89Mo composite via water quenching(W...With the purpose of improving both the strength and ductility,gradient equiaxed grains were successfully achieved in the matrix of the laminated TiB/Ti-TiB/Ti-6.58Al-1.76Zr-1.04V-0.89Mo composite via water quenching(WQ) and thermal compressing deformation. Gradient equiaxed grains varied from approximately 1.0 μm in TiB/Ti-6.58Al-1.76Zr-1.04V-0.89Mo layer to 5.5 μm in TiB/Ti layer. The formation of the gradient structure was related to the alloying elements diffusion during the initial sintering process,and the equiaxed shape was constructed by dynamic recrystallization during thermal compressing. WQ treatment before thermal compressing was adopted to obtain fine lamellar structure,which promoted the segmentation of αlamellae,and accelerated the dynamic recrystallization process. Raising the quenching temperature can increase the proportion of equiaxed grains in the composite,which improved both the bending strength and ductility. Compared with the as-sintered specimen,the specimen with gradient equiaxed grains exhibited nearly 30% enhancement in flexural strength(from 1719 to 2218 MPa),and the ultimate bending fracture strain was increased from 7.0% to 17.2%. This significant improvement should be attributed to the coordination deformation by interface gradient grains,the grain refinement strengthening and the good balance between strength and ductility of the recrystallized equiaxed grains.展开更多
基金Project (50802115) supported by the National Natural Science Foundation of ChinaProject (2011CB605801) supported by the National Basic Research Program of China
文摘C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high density of 0.94 g/cm3 as preform.Experimental results indicated that the fracture characteristics of C/C composites were closely related to the frequency of high-temperature treatment（HTT） at the break of CVI process.According to the load？displacement curves,C/C composites showed a pseudoplastic fracture after twice of HTT.After three times of HTT,load？displacement curves tended to be stable with a decreasing bending strength at 177.5 MPa.Delamination failure and intrastratal fiber fracture were observed at the cross-section of C/C composites by scanning electronic microscope.Because the content of pyrocarbon and fibers has a different distribution in layers,the C/C composites show different fracture characteristics at various regions,which leads to good toughness and bending strength.
基金Funded by the Open Research Foundation of State Key Lab of Digital Manufacturing Equipment & Technology in Huazhong University of Science & Technology (No. DMETKF2009016)the Hubei Province Science Founda-tion (No.2008CDB274)+1 种基金the Wuhan High-Tech Development Project Founda-tion (No.200812121559)the International Collaborative Research Funds of Chonbuk National University, 2008
文摘To analyze the bending properties of GCr15 steel guide rail based on the elastic-plastic theory, the novel bending loading method consisting of multi-step loading and corresponding unloading was applied in three specimens with different cross section shape and different heat treatment condition. According to the experimental results, using numerical calculation software program and the numerical simulation with finite element analysis （FEA）, the relationships among the maximal load and displacement on cross section shape with each step bend loading, the loading stroke with the heat treatment condition, and the loading stroke with cross section shape were gained, and also those curves were discussed qualitatively. Finally, the contrast results between the numerical simulation and experiment were carried out to study the influence about the multi-step loading on specimen. It is put forward that enlightenment for the straightening stroke in the precision linear guide rail manufacture process.
文摘Connection plays an important role in structural components and end jointing is one of the most common connections in structural applications. This study was designed to investigate some mechanical properties （MOE and MOR） of solid wood samples manufactured from poplar （Populus nigra）, joined together through end jointing. As well, we studied combinations of lumber manufactured from 10-mm veneer, using a polyvinyl acetate adhesive. The results show that non-jointed lumber （control samples） have better bending properties （MOE and MOR） than jointed specimens and lumber made from laminated layers. On the whole, side-by- side joints have a negative effect on the MOR and MOE of laminated products, which is more pronounced in the MOR. By increasing the number of joints, the properties of combination of three-ply, i.e., bending strength and modulus of elasticity, decreased.
基金supported by the National Natural Science Foundation of China (Nos.52001030,51803200,52105356,52003104)the Natural Science Foundation of Hunan Province,China (Nos.2021JJ40590,2021JJ40600)+6 种基金the Natural Science Foundation of Hunan Province Youth Fund,China (No.2021JJ20011)the Major Research Plan of the National Natural Science Foundation of China (No.92166112)the Project of MOE Key Lab of Disaster Forecast and Control in Engineering in Jinan University,China (No.20200904006)the Guangdong Province Basic and Applied Basic Research Foundation,China (No.2020B1515420004)the Guangxi Key Laboratory of Information Materials,China (No.211003-K)the Open Project Program of the State Key Laboratory of Mechanical Transmissions in Chongqing University,China (No.SKLMT-MSKFKT-202102)the Fundamental Research Funds for the Central Universities,China (No.21622110)。
文摘A NiTi@Mg interpenetrating phase composite with high strength and lightweight was prepared by additive manufacturing(AM)and infiltration technology,and the interface bonding,three-point bending properties and cyclic compressive properties of NiTi@Mg composites were investigated.The results show that the metallurgically bonded interface is formed at the NiTi/Mg interfaces.The bending strength and compressive strength of the NiTi@Mg composite are 2.5 and 1.7 times higher than those of the NiTi scaffold,respectively.During the bending deformation process,a large number of dislocations are observed to accumulate in the soft Mg area at the interface.Furthermore,the finite element model showed that the stress accumulation area,where the bending crack is initiated,is located at the interface of NiTi and Mg.The strengthening mechanism of NiTi@Mg composites is attributed to the twinning strengthening of Mg and heterogeneous structure strengthening.
基金The work was financially supported by the National Key R&D Program of China under project 2017YFC0703700.
文摘To improve the mechanical properties of Trabecular Beetle Elytron Plates(TBEPs,a type of biomimetic sandwich structure inspired by the beetle elytron)under transverse loads,three-point bending tests are performed to investigate the influence of the trabecular and chamfer radii of the core structure on the mechanical performance of TBEPs manufactured by 3D printing technology.The results show that the three-point bending performance of TBEPs can be improved by setting reasonable trabecular and chamfer radii;however,excessive increases in these radii can cause a decline in the mechanical performance.For the reason,these two structural parameters can enhance the deformation stiffness of the whole structure and the connection property between the core and skin,which is also the mechanical reason why Prosopocoilus inclinatus beetle elytra have thick,short trabeculae with a large chamfer radius.However,when these radii increase to a certain extent,the cracks are ultimately controlled between two adjacent trabeculae,and the failure of the plate is determined by the skin rather than the core structure.Therefore,this study suggests a reasonable range for trabecular and chamfer radii,and indicates that TBEPs are better suited for engineering applications that have high compression requirements and general bending requirements.
基金Supported by Natural Foundation Program of Henan Province(2009B210016)~~
文摘[ Objective] The aim is to research the relationship between bending property and density of wheat stem. [ Method ] The bending properties such as elastic modulus, bending strength, flexural rigidity, moment of inertia, density and water content of the second base internodes of Zhengmai 9023 and Yumai 25 were determined. [ Result] The results show that during filling stage, there are significant differences in the elastic modulus, moment of inertia, flexural rigidity and density among wheat varieties, while there are no significant differences in the bending strength and water content among wheat varieties. The moment of inertia, flexural strength and flexural rigidity have positive relationship to density but negative relationship to water content. [ Conclusion] The study results provide some references for the research on high yield cultivation and lodging resistance of wheat.
文摘Recent progress in production process for advanced high strength steel sheets（AHSS） is described focussing on Bainitic ferrite steel,transformation induced plasticity（TRIP） steel and precipitation hardened steel by NANO sized precipitates are reviewed. In higher tensile strength（TS） grade,elongation（El）,hole expansion ratio（λ） and their balance are eagerly requested to improve by customers.Bainitic ferrite steel which has shear deformed lath with various distribution of iron carbides and retained austenite should be distinguished to produce different balance of El/λ. Chemical composition and heat cycle are reviewed to produce various kinds of metallurgical phase and mechanical property.5%Mn -2%Si TRIP steel is introduced in which a plenty of retained austenite at about 30%and larger absorbed energy（AE） more than 3 000 kgf/mm;TS·%El（gauge length:50 mm） can be obtained. That steel also showed excellent upper shelf energy in Charpy test of 140 J/cm;,as well as excellent property of 20%El and 1 400 MPa TS after forging. A new type of precipitation hardened steel having NANO sized（Ti,Mo） C in ferrite matrix is introduced.It satisfies the both of excellent El andλat the same time. Bending property and holes expansion property obey the same kind of deforming criteria which depends on the forming capability of work hardened parts.Homogeneity of structure is their controlling factor and a new parameterαwhich is obtained by gauge length dependency of total elongation is proposed.
基金financially supported by the National Natural Science Foundation of China(No.52071035,U1764253)。
文摘The AZ31 and AM60 alloys were used for dissimilar friction stir welding(FSW)in this study.The microstructure characteristics of the joint and its three-point bending performance were investigated.The electron backscattered diffraction results showed that the grains in the nugget zone(NZ)were more uniform and refined to a certain extent after FSW,but the grain size of AM60 in the NZ was larger than that of AZ31.The texture was strong locally in the NZ and presented a symmetric distribution characteristic from the advancing side to the retreating side.There were special texture features in the joint,resulting in the occurrence of severe strain localization during the bending process compared with the base materials,which can be well explained by the calculated Schmid factor in terms of the assumed stress state for bending.The bending tests revealed that the joint presented good bending properties compared with AZ31 BM.The bending fracture morphologies suggested that the fracture tended to the NZ interface on the AZ31 side,which was mainly due to the higher SF for basal slip and dislocation concentration degree in the region,and the relatively lower bending strength of AZ31 metal.
文摘We investigated the resistance of acetylated rattan against soft rot and other soil inhabiting micro-organisms in comparison with wood of beech and Scots pine. Calamus manan of 10 and 13 years old under rubber tree canopy was acetylated to different levels by reaction times （0.25 to 30 hours） and was tested for soft rot decay for 32 weeks. Acetylated rattan at decay protection thresholds of 15.4% and 16.2% weight gain （WG） were fully protected, as shown by both weight loss and strength loss criteria. The static bending properties of untreated rattan decayed by soft rot were significantly lower than for acetylated rattan.
基金supported by the National Natural Science Foundation of China (Grant No. 50890173)
文摘Al/Mg alloy multilayered composites were produced successfully at the lower temperature（280 C） by accumulative roll bonding（ARB） processing technique.The microstructures of Al and Mg alloy layers were characterized by scanning electron microscopy and transmission electron microscopy.Vickers hardness and three-point bending tests were conducted to investigate mechanical properties of the composites.It is found that Vickers hardness,bending strength and stiffness modulus of the Al/Mg alloy multilayered composite increase with increasing the ARB pass.Delamination and crack propagation along the interface are the two main failure modes of the multilayered composite subjected to bending load.Strengthening and fracture mechanisms of the composite are analyzed.
基金This work was supported by the National Key R&D Program of China(Grant No.2017YFB0703100)the Guangdong Province Key Area R&D Program(Grant No.2019B010942001)+1 种基金the National Natural Science Foundation of China(Grant Nos.51822103,51801206 and 51731009)the Fundamental Research Funds for the Central Universities(Grant No.HIT.BRETIV.201902)。
文摘With the purpose of improving both the strength and ductility,gradient equiaxed grains were successfully achieved in the matrix of the laminated TiB/Ti-TiB/Ti-6.58Al-1.76Zr-1.04V-0.89Mo composite via water quenching(WQ) and thermal compressing deformation. Gradient equiaxed grains varied from approximately 1.0 μm in TiB/Ti-6.58Al-1.76Zr-1.04V-0.89Mo layer to 5.5 μm in TiB/Ti layer. The formation of the gradient structure was related to the alloying elements diffusion during the initial sintering process,and the equiaxed shape was constructed by dynamic recrystallization during thermal compressing. WQ treatment before thermal compressing was adopted to obtain fine lamellar structure,which promoted the segmentation of αlamellae,and accelerated the dynamic recrystallization process. Raising the quenching temperature can increase the proportion of equiaxed grains in the composite,which improved both the bending strength and ductility. Compared with the as-sintered specimen,the specimen with gradient equiaxed grains exhibited nearly 30% enhancement in flexural strength(from 1719 to 2218 MPa),and the ultimate bending fracture strain was increased from 7.0% to 17.2%. This significant improvement should be attributed to the coordination deformation by interface gradient grains,the grain refinement strengthening and the good balance between strength and ductility of the recrystallized equiaxed grains.
