Affected by the geological characteristics of coal bearing strata in western mining areas of China,the double soft composite roof has low strength and poor integrity,which is prone to induce disasters such as large de...Affected by the geological characteristics of coal bearing strata in western mining areas of China,the double soft composite roof has low strength and poor integrity,which is prone to induce disasters such as large deformation and roof collapse.Four-point bending tests were conducted on anchored double-layer rock beams with different pre tightening force and upper/lower rock strength ratios(Ⅰ/Ⅱ)based on the digital speckle correlation method(DSCM).The research results indicate that the instability process of anchored roof can be divided into stages of elastic deformation,crack propagation,alternating fracture,and failure collapse.The proportion of crack propagation and alternating fracture processes increased with the increase of pre-tightening force and Ⅰ/Ⅱ.The pre-tightening force can suppress the sliding of the upper/lower rock interface,and delay the initiation and propagation of cracks.As Ⅰ/Ⅱ increases,the failure mode changes from tensile failure steel strip to shear failure anchor rod.Steel strip can improve the continued bearing effect of anchored roof during crack propagation and alternating fracture processes.展开更多
Faulted gas reservoirs are very common in reality,where some linear leaky faults divide the gas reservoir into several reservoir regions with distinct physical properties.This kind of gas reservoirs is also known as l...Faulted gas reservoirs are very common in reality,where some linear leaky faults divide the gas reservoir into several reservoir regions with distinct physical properties.This kind of gas reservoirs is also known as linear composite(LC)gas reservoirs.Although some analytical/semi-analytical models have been proposed to investigate pressure behaviors of producing wells in LC reservoirs based on the linear composite ideas,almost all of them focus on vertical wells and studies on multiple fractured horizontal wells are rare.After the pressure wave arrives at the leaky fault,pressure behaviors of multiple fractured horizontal wells will be affected by the leaky faults.Understanding the effect of leaky faults on pressure behaviors of multiple fractured horizontal wells is critical to the development design.Therefore,a semi-analytical model of finite-conductivity multiple fractured horizontal(FCMFH)wells in LC gas reservoirs is established based on Laplace-space superposition principle and fracture discrete method.The proposed model is validated against commercial numerical simulator.Type curves are obtained to study pressure characteristics and identify flow regimes.The effects of some parameters on type curves are discussed.The proposed model will have a profound effect on developing analytical/semi-analytical models for other complex well types in LC gas reservoirs.展开更多
Interface debonding between particle and matrix in composite propellant influences its macroscopic mechanical properties greatly. For this, the laws of interface cohesive damage and failure were analyzed. Then, its mi...Interface debonding between particle and matrix in composite propellant influences its macroscopic mechanical properties greatly. For this, the laws of interface cohesive damage and failure were analyzed. Then, its microscopic computational model was established. The interface mechanical response was modeled by the bilinear cohesive zone model. The effects of interface properties and particle sizes on the macroscopic mechanical behavior were investigated. Numerical simulation of debonding damage evolution of composite propellant under finite deformation was carried out. The debonding damage nucleation, propagation mechanism and non-uniform distribution of microscopic stress-strain fields were discussed. The results show that the finite element simulation method based on microstructure model can effectively predict the trend of macroscopic mechanical behavior and particle/matrix debonding evolution process. It can be used for damage simulation and failure assessment of composite propellants.展开更多
The stiffness matrix of semi-rigidly connected composite beams considering interface slip was established and the calculation method for elastic seismic response of composite frame was derived.The corresponding calcul...The stiffness matrix of semi-rigidly connected composite beams considering interface slip was established and the calculation method for elastic seismic response of composite frame was derived.The corresponding calculation programs were developed.Introducing the dimensionless quantities that were related to the connector shearing stiffness and the joint rotation stiffness,the influences of interface slip and semi-rigid joint on composite frame were transferred to quantitative parameter analysis,taking account of cross sectional properties,materials and linear stiffness of composite beam synthetically.Based on the calculation programs,free vibration frequencies and seismic responses of semi-rigid joint steel-concrete composite frame considering interface slip were calculated.The influences of interface slip and semi rigid joint on dynamic characteristics and seismic response were analyzed and the seismic design advices were presented.The results show that the interface slip decreases the free vibration frequencies and increase the seismic responses of composite frame.The semi-rigid joint reduces the free vibration frequencies and increases seismic responses of composite frame compared with rigid joint.With the increase of joint rotational stiffness,the elastic seismic responses of composite frame increase firstly and then decrease.The effects are related to the ratio of joint rotation stiffness to linear stiffness of composite beam.展开更多
Nine kinds of glass-ceramic matrix composites with different compositions and inter facial strength(L) were prepared. The influence of Ti on the fracture toughness (K1c.) of composites was studied. It was discoved tha...Nine kinds of glass-ceramic matrix composites with different compositions and inter facial strength(L) were prepared. The influence of Ti on the fracture toughness (K1c.) of composites was studied. It was discoved that, for the system no chemical reaction taking place at the interface, K1c. increased proportionallywith ts increasing at the first stage, then decreased when ts reached a certain value. According to this result,a model of relationship between L, thermal mismatch (Δαr) and K1c was built up. If a chemical reaction tookplace and a new phase was formed in the interface, the K1c. of composite was effected by the combination ofrs, chemical bonding, radial inter facial stress and other factors.展开更多
In order to obtain high-density dual-scale ceramic particles(8.5 wt.%SiC+1.5 wt.%TiC)reinforced Al-Mg Sc-Zr composites with uniform microstructure,50 nm TiC and 7μm SiC particles were pre-dispersed into 15−53μm alum...In order to obtain high-density dual-scale ceramic particles(8.5 wt.%SiC+1.5 wt.%TiC)reinforced Al-Mg Sc-Zr composites with uniform microstructure,50 nm TiC and 7μm SiC particles were pre-dispersed into 15−53μm aluminum alloy powders by low-speed ball milling and mechanical mixing technology,respectively.Then,the effects of laser energy density,power and scanning rate on the density of the composites were investigated based on selective laser melting(SLM)technology.The effect of micron-sized SiC and nano-sized TiC particles on solidification structure,mechanical properties and fracture behaviors of the composites was revealed and analyzed in detail.Interfacial reaction and phase variations in the composites with varying reinforced particles were emphatically considered.Results showed that SiC-TiC particles could significantly improve forming quality and density of the SLMed composites,and the optimal relative density was up to 100%.In the process of laser melting,a strong chemical reaction occurs between SiC and aluminum matrix,and micron-scale acicular Al_(4)SiC_(4) bands were formed in situ.There was no interfacial reaction between TiC particles and aluminum matrix.TiC/Al semi-coherent interface had good bonding strength.Pinning effect of TiC particles in grain boundaries could prevent the equiaxial crystals from growing and transforming into columnar crystals,resulting in grain refinement.The optimal ultimate tensile strength(UTS),yield strength(YS),elongation(EL)and elastic modulus of the SiC-TiC/Al-Mg-Sc-Zr composite were~394 MPa,~262 MPa,~8.2%and~86 GPa,respectively.The fracture behavior of the composites included ductile fracture of Al matrix and brittle cleavage fracture of Al_(4)SiC_(4) phases.A large number of cross-distributed acicular Al_(4)SiC_(4) bands were the main factors leading to premature failure and fracture of SiC-TiC/Al-Mg-Sc-Zr composites.展开更多
Continuous carbon fiber reinforced silicon carbide(C/SiC)composites are often subjected to low-velocity impacts when utilized as structural materials for thermal protection.However,research on in-plane impact damage a...Continuous carbon fiber reinforced silicon carbide(C/SiC)composites are often subjected to low-velocity impacts when utilized as structural materials for thermal protection.However,research on in-plane impact damage and multiple impact damage of C/SiC composites is limited.To investigate the in-plane impact damage behavior of C/SiC composites,a drop-weight impact test method was developed for strip samples,and these results were subsequently compared with those of C/SiC composite plates.Results show that the in-plane impact behavior of C/SiC strip samples is similar to that of C/SiC composite plates.Variation of the impact load with displacement is characterized by three stages:a nearly linear stage,a severe load drop stage,and a rebound stage where displacement occurs after the impact energy exceeds its peak value.Impact damage behavior under single and multiple impacts on 2D plain and 3D needled C/SiC composites was investigated at different impact energies and durations.Crack propagation in C/SiC composites was studied by computerized tomography(CT)technique.In the 2D plain C/SiC composite,load propagation between layers is hindered during impact,leading to delamination and 90°fiber brittle fracture.The crack length perpendicular to the impact direction increases with impact energy increases,resulting in more serious 0°fiber fracture and a larger area of fiber loss.In the 3D needled C/SiC composite,load propagates between the layers during impact through the connection of needled fibers.The fibers continue to provide substantial structural support,with notable instances of fiber pull-off and debonding.Consequently,the impact resistance is superior to that of 2D plain C/SiC composite.When the 3D needled C/SiC composite undergoes two successive impacts of 1.5 J,the energy absorption efficiency of the second impact is significantly lower,accompanied by a smaller impact displacement.Moreover,the total energy absorption efficiency of these two impacts of 1.5 J is lower than that of a single 3.0 J impact.展开更多
The stability of the“surrounding rock-backfill”com posite system is crucial for the safety of mining stopes.This study systematically investigates the effects of steel slag(SS)content and interface angle on the stre...The stability of the“surrounding rock-backfill”com posite system is crucial for the safety of mining stopes.This study systematically investigates the effects of steel slag(SS)content and interface angle on the strength and failure characteristics of rock and SS-cemented paste backfill composite specimens(RBCS)through uniaxial compression strength tests(UCS),acoustic emission systems(AE),and 3 D digital image correlation monitoring technology(3 D-DIC).The intrinsic mechanism by which SS content influences the strength of SS-CPB was revealed through an analysis of its hydration reaction degree and microstructural characteristics under varying SS content.Moreover,a theoretical strength model incorporating different interface angles was developed to explore the impact of interface inclination on failure modes and mechanical strength.The main conclusions are as follows:The incorporation of SS enhances the plastic characteristics of RBCS and reduces its brittleness,with the increase of SS content,the stress-strain curve of RBCS in the“staircase-like”stag e becomes smoother;When the interface angle is 45°,the RBCS stress-strain curve exhibits a bimodal feature,and the failure mode changes from Y-shaped fractures to interface and axial splitting;The addition of SS results in a reduction of hydration products such as Ca(OH)_(2) in the backfill cementing system and an increase in harmful pores,which weakens the bonding performance and strength of RBCS,and the SS content should not exceed 45%;As the interface angle increases,the strength of RBCS decreases,and the critical interface slip angle decreases first and then increases with the increase in the E S/E R ratio.This study provides technical references for the large-scale application of SS in mine backfill.展开更多
A high speed steel composite roll billet was fabricated, which is regular in shape, smooth in surface, slight in trace, compact in internal structure, free of slag inclusion, shrinkage cavity, cracks and other flaws, ...A high speed steel composite roll billet was fabricated, which is regular in shape, smooth in surface, slight in trace, compact in internal structure, free of slag inclusion, shrinkage cavity, cracks and other flaws, and good in macro quality of junction surface using a vertical continuous casting machine. The interface zone microstructure of bimetallic in billet of high speed steel composite roll was analyzed by metallurgical microscope(OM), X-ray diffractmeter(XRD), scanning electron microscopy(SEM) and energy-dispersive X-ray analysis(EDS). The results indicate that the microstructure of roll billet is composed of chilled solidified layer, dendrite zone, interfacial zone of bimetal and core material zone. The microstructure of outer shell material is composed of martensite + bainite + residual austenite + some small labyrinth-shape, small-short lath-shape, or dollop-shape eutectic carbides. The microstructure of core material is slice-shape pearlite and a little ferrite along boundary of cells. The interface region microstructure of bimetallic composite roll consists of diffusion region, chilled solidified layer and columnar grain region.展开更多
Abstract： An alloy steel/alumina composite was successfully fabricated by pressureless infiltration of X10CrNil8-8 steel melt on 30% （mass fraction） Ni-containing alumina based composite ceramic （Ni/Al2O3） at 1 6...Abstract： An alloy steel/alumina composite was successfully fabricated by pressureless infiltration of X10CrNil8-8 steel melt on 30% （mass fraction） Ni-containing alumina based composite ceramic （Ni/Al2O3） at 1 600 ℃. The infiltration quality and interfacial bonding behavior were investigated by SEM, EDS, XRD and tensile tests. The results show that there is an obvious interfacial reaction layer between the alloying steel and the Ni/Al2O3 composite ceramic. The interfacial reactive products are （FexAly）3O4 intermetallic phase and （AlxCry）2O3 solid solution. The interracial bonding strength is as high as about 67.5 MPa. The bonding mechanism of X10CrNi 18-8 steel with the composite ceramic is that Ni inside the ceramic bodies dissolves into the alloy melt and transforms into liquid channels, consequently inducing the steel melt infiltrating and filling in the pores and the liquid channels. Moreover, the metallurgical bonding and interfacial reactive bonding also play a key role on the stability of the bonding interface.展开更多
Carrying on a series of compression and shear tests by a large number of specimens, reliabilities of T300/QY8911 laminated composite were studied when dispersibility models were described. The results show that the st...Carrying on a series of compression and shear tests by a large number of specimens, reliabilities of T300/QY8911 laminated composite were studied when dispersibility models were described. The results show that the stress is linearly dependent on the strain and the damage modes of specimens are brittle fracture for both kinds of tests. Dispersibility models of compression and shear strength are expressed as Re-N（415.39, 6 586.36） and Rs-ln（5.071 8, 0.155 3）, respectively. When normal and lognormal distributions were used to describe the dispersibility models of compression and shear strength, and the compression or shear load follows the normal distribution, the almost same failure probability can be obtained from different reliability analysis methods.展开更多
To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring art...To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring artificial boundary(VSAB) is adopted to simulate the radiation damping of their infinite foundations, and based on the Marc software, a simplified seismic motion input method is presented by the equivalent nodal loads. Finally, based on the practical engineering of a RCC gravity dam, effects of radiation damping and construction interfaces on the dynamic characteristics of dams are investigated in detail. Analysis results show that dynamic response of the RCC gravity dam significantly reduces about 25% when the radiation damping of infinite foundation is considered. Hot interfaces and the normal cold interfaces have little influence on the dynamic response of the RCC gravity dam.However, nonlinear fracture along the cold interfaces at the dam heel will occur under the designed earthquake if the cold interfaces are combined poorly. Therefore, to avoid the fractures along the construction interfaces under the potential super earthquakes,combination quality of the RCC layers should be significantly ensured.展开更多
The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interfa...The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interface. Fatigue properties of the composite beam under the action of negative moment were experimentally studied. Through inverted loading mode the load-beating state of a composite beam was simulated under the action of negative moment. With the ratios of constructional bars being 0, 0.082% and 0.164% respectively as parameters, the effects of constructional bars on the properties of composite beam, such as fatigue life, crack propagation, rigidity loss as well as damage behavior of bonding interface, were studied. The mechanism of the constructional bars on the fatigue properties of the composite beams and the restriction mechanism of crack widths and rigidity loss were analyzed. The test results show that the constructional bars can enhance the shear resistance of the bonding interface between composite layer and old concrete beam and restrict expanding of steel fiber reinforced self-stressing concrete, which are beneficial to synergistic action of composite layer and old concrete beam, to reducing the stress amplitude of bars and the crack width of composite layer, and to increasing the durability and fatigue life of the composite beam.展开更多
The fracture behavior of polymer-bonded explosive(PBX) seriously affects the safety and reliability of weapon system.The effects of interface debonding and initial meso-damage on the fracture behavior of PBX under qua...The fracture behavior of polymer-bonded explosive(PBX) seriously affects the safety and reliability of weapon system.The effects of interface debonding and initial meso-damage on the fracture behavior of PBX under quasi-static tension are studied using numerical method.A twodimensional representative volume element(RVE) is established based on Voronoi model in which the component contents could be regulated and the particles are randomly distributed.A nonlinear damage model of polymer matrix relative to matrix depth between particles is constructed.The results show that the simulated strain-stress relation is coincident with experiment data.It is found that interface debonding leads to the nucleation and propagation of meso-cracks,and a main crack approximately perpendicular to the loading direction is generated finally.The interface debonding tends to occur in the interface perpendicular to the loading direction.There seems to be a phenomenon that strain softening and hardening alternatively appear around peak stress of stress and strain curve.It is shown that the initial damages of intragranular and interfacial cracks both decrease the modulus and failure stress,and the main crack tends to propagate toward the initial meso-cracks.展开更多
Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the...Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.展开更多
Improving interfacial bonding and alloying design are effective strategies for enhancing mechanical properties of particle-reinforced steel matrix composites(SMCs).This study prepared SMCs with uniformly distributed T...Improving interfacial bonding and alloying design are effective strategies for enhancing mechanical properties of particle-reinforced steel matrix composites(SMCs).This study prepared SMCs with uniformly distributed TiC_(P) in matrix using master alloying method.The TiC(002)/Fe(011)interface model was established based on the orientation relationship of(011)_(Fe)//(002)_(TiC),and[100]_(Fe)//[100]_(TiC).The effects of single and co-doping of alloying elements(Mn,Cr,Mo,Ni,Cu and Si)on the interface bonding behavior of TiC/Fe in composites were investigated in conjunction with first principles.The results demonstrate that the interface between TiC and matrix is continuous and stable.Compared to the undoped TiC/Fe interface,single-doping Mn,Cr,and Mo can improve the stability of TiC/Fe interface and enhance tensile strength.Conversely,single-doping with Ni,Cu,and Si reduced the interface stability and marginally reduces tensile strength.Relative to the undoped and singly Ni-doped TiC/Fe interfaces,the co-doping Ni-Mo boosts binding energy and separation work at the TiC/Fe interface,which is conducive to the interface bonding between TiC_(P) and matrix,and thus improves the mechanical properties of composites.Thus,in the alloying design of TiC particle reinforced low-alloy SMCs,incorporating Mn,Cr,Mo,and Ni into matrix can enhance the overall mechanical properties of composites.展开更多
基金Project(SDAST2024QT060)supported by the Young Talent of Lifting Engineering for Science and Technology in Shandong,ChinaProjects(52304136,52304149,52204093)supported by the National Natural Science Foundation of China+1 种基金Project(ZR2022ME165)supported by the Shandong Provincial Natural Science Foundation,ChinaProject(2023YD02)supported by the Key Project of Research and Development in Liaocheng,China。
文摘Affected by the geological characteristics of coal bearing strata in western mining areas of China,the double soft composite roof has low strength and poor integrity,which is prone to induce disasters such as large deformation and roof collapse.Four-point bending tests were conducted on anchored double-layer rock beams with different pre tightening force and upper/lower rock strength ratios(Ⅰ/Ⅱ)based on the digital speckle correlation method(DSCM).The research results indicate that the instability process of anchored roof can be divided into stages of elastic deformation,crack propagation,alternating fracture,and failure collapse.The proportion of crack propagation and alternating fracture processes increased with the increase of pre-tightening force and Ⅰ/Ⅱ.The pre-tightening force can suppress the sliding of the upper/lower rock interface,and delay the initiation and propagation of cracks.As Ⅰ/Ⅱ increases,the failure mode changes from tensile failure steel strip to shear failure anchor rod.Steel strip can improve the continued bearing effect of anchored roof during crack propagation and alternating fracture processes.
基金Project(2017QHZ031)supported by Scientific Research Starting Project of Southwest Petroleum University,ChinaProject(18TD0013)supported by Science and Technology Innovation Team of Education Department of Sichuan for Dynamical System and Its Applications,ChinaProject(2017CXTD02)supported by Youth Science and Technology Innovation Team of Southwest Petroleum University for Nonlinear Systems,China。
文摘Faulted gas reservoirs are very common in reality,where some linear leaky faults divide the gas reservoir into several reservoir regions with distinct physical properties.This kind of gas reservoirs is also known as linear composite(LC)gas reservoirs.Although some analytical/semi-analytical models have been proposed to investigate pressure behaviors of producing wells in LC reservoirs based on the linear composite ideas,almost all of them focus on vertical wells and studies on multiple fractured horizontal wells are rare.After the pressure wave arrives at the leaky fault,pressure behaviors of multiple fractured horizontal wells will be affected by the leaky faults.Understanding the effect of leaky faults on pressure behaviors of multiple fractured horizontal wells is critical to the development design.Therefore,a semi-analytical model of finite-conductivity multiple fractured horizontal(FCMFH)wells in LC gas reservoirs is established based on Laplace-space superposition principle and fracture discrete method.The proposed model is validated against commercial numerical simulator.Type curves are obtained to study pressure characteristics and identify flow regimes.The effects of some parameters on type curves are discussed.The proposed model will have a profound effect on developing analytical/semi-analytical models for other complex well types in LC gas reservoirs.
基金Sponsored by the General Armament Department Advanced Research Project (20101019)
文摘Interface debonding between particle and matrix in composite propellant influences its macroscopic mechanical properties greatly. For this, the laws of interface cohesive damage and failure were analyzed. Then, its microscopic computational model was established. The interface mechanical response was modeled by the bilinear cohesive zone model. The effects of interface properties and particle sizes on the macroscopic mechanical behavior were investigated. Numerical simulation of debonding damage evolution of composite propellant under finite deformation was carried out. The debonding damage nucleation, propagation mechanism and non-uniform distribution of microscopic stress-strain fields were discussed. The results show that the finite element simulation method based on microstructure model can effectively predict the trend of macroscopic mechanical behavior and particle/matrix debonding evolution process. It can be used for damage simulation and failure assessment of composite propellants.
基金Project(50778177) supported by the National Natural Science Foundation of ChinaProject(07JJ1009) supported by the Outstanding Younger Fund of Hunan Province,China
文摘The stiffness matrix of semi-rigidly connected composite beams considering interface slip was established and the calculation method for elastic seismic response of composite frame was derived.The corresponding calculation programs were developed.Introducing the dimensionless quantities that were related to the connector shearing stiffness and the joint rotation stiffness,the influences of interface slip and semi-rigid joint on composite frame were transferred to quantitative parameter analysis,taking account of cross sectional properties,materials and linear stiffness of composite beam synthetically.Based on the calculation programs,free vibration frequencies and seismic responses of semi-rigid joint steel-concrete composite frame considering interface slip were calculated.The influences of interface slip and semi rigid joint on dynamic characteristics and seismic response were analyzed and the seismic design advices were presented.The results show that the interface slip decreases the free vibration frequencies and increase the seismic responses of composite frame.The semi-rigid joint reduces the free vibration frequencies and increases seismic responses of composite frame compared with rigid joint.With the increase of joint rotational stiffness,the elastic seismic responses of composite frame increase firstly and then decrease.The effects are related to the ratio of joint rotation stiffness to linear stiffness of composite beam.
文摘Nine kinds of glass-ceramic matrix composites with different compositions and inter facial strength(L) were prepared. The influence of Ti on the fracture toughness (K1c.) of composites was studied. It was discoved that, for the system no chemical reaction taking place at the interface, K1c. increased proportionallywith ts increasing at the first stage, then decreased when ts reached a certain value. According to this result,a model of relationship between L, thermal mismatch (Δαr) and K1c was built up. If a chemical reaction tookplace and a new phase was formed in the interface, the K1c. of composite was effected by the combination ofrs, chemical bonding, radial inter facial stress and other factors.
基金Project(2022J318)supported by the Natural Science Foundation of Ningbo,ChinaProject(2021A1515110525)supported by the Guangdong Basic and Applied Basic Research Foundation,ChinaProject(2022QN05023)supported by the Inner Mongolia Natural Science Foundation Youth Project,China。
文摘In order to obtain high-density dual-scale ceramic particles(8.5 wt.%SiC+1.5 wt.%TiC)reinforced Al-Mg Sc-Zr composites with uniform microstructure,50 nm TiC and 7μm SiC particles were pre-dispersed into 15−53μm aluminum alloy powders by low-speed ball milling and mechanical mixing technology,respectively.Then,the effects of laser energy density,power and scanning rate on the density of the composites were investigated based on selective laser melting(SLM)technology.The effect of micron-sized SiC and nano-sized TiC particles on solidification structure,mechanical properties and fracture behaviors of the composites was revealed and analyzed in detail.Interfacial reaction and phase variations in the composites with varying reinforced particles were emphatically considered.Results showed that SiC-TiC particles could significantly improve forming quality and density of the SLMed composites,and the optimal relative density was up to 100%.In the process of laser melting,a strong chemical reaction occurs between SiC and aluminum matrix,and micron-scale acicular Al_(4)SiC_(4) bands were formed in situ.There was no interfacial reaction between TiC particles and aluminum matrix.TiC/Al semi-coherent interface had good bonding strength.Pinning effect of TiC particles in grain boundaries could prevent the equiaxial crystals from growing and transforming into columnar crystals,resulting in grain refinement.The optimal ultimate tensile strength(UTS),yield strength(YS),elongation(EL)and elastic modulus of the SiC-TiC/Al-Mg-Sc-Zr composite were~394 MPa,~262 MPa,~8.2%and~86 GPa,respectively.The fracture behavior of the composites included ductile fracture of Al matrix and brittle cleavage fracture of Al_(4)SiC_(4) phases.A large number of cross-distributed acicular Al_(4)SiC_(4) bands were the main factors leading to premature failure and fracture of SiC-TiC/Al-Mg-Sc-Zr composites.
基金Aeronautical Science Foundation of China(2021Z057053001)。
文摘Continuous carbon fiber reinforced silicon carbide(C/SiC)composites are often subjected to low-velocity impacts when utilized as structural materials for thermal protection.However,research on in-plane impact damage and multiple impact damage of C/SiC composites is limited.To investigate the in-plane impact damage behavior of C/SiC composites,a drop-weight impact test method was developed for strip samples,and these results were subsequently compared with those of C/SiC composite plates.Results show that the in-plane impact behavior of C/SiC strip samples is similar to that of C/SiC composite plates.Variation of the impact load with displacement is characterized by three stages:a nearly linear stage,a severe load drop stage,and a rebound stage where displacement occurs after the impact energy exceeds its peak value.Impact damage behavior under single and multiple impacts on 2D plain and 3D needled C/SiC composites was investigated at different impact energies and durations.Crack propagation in C/SiC composites was studied by computerized tomography(CT)technique.In the 2D plain C/SiC composite,load propagation between layers is hindered during impact,leading to delamination and 90°fiber brittle fracture.The crack length perpendicular to the impact direction increases with impact energy increases,resulting in more serious 0°fiber fracture and a larger area of fiber loss.In the 3D needled C/SiC composite,load propagates between the layers during impact through the connection of needled fibers.The fibers continue to provide substantial structural support,with notable instances of fiber pull-off and debonding.Consequently,the impact resistance is superior to that of 2D plain C/SiC composite.When the 3D needled C/SiC composite undergoes two successive impacts of 1.5 J,the energy absorption efficiency of the second impact is significantly lower,accompanied by a smaller impact displacement.Moreover,the total energy absorption efficiency of these two impacts of 1.5 J is lower than that of a single 3.0 J impact.
基金Project(52308316)supported by the National Natural Science Foundation of China,Project(BBJ2024088)supported by the Fundamental Research Funds for the Central Universities(PhD.Top Innovative Talents Fund of CUMTB),China。
文摘The stability of the“surrounding rock-backfill”com posite system is crucial for the safety of mining stopes.This study systematically investigates the effects of steel slag(SS)content and interface angle on the strength and failure characteristics of rock and SS-cemented paste backfill composite specimens(RBCS)through uniaxial compression strength tests(UCS),acoustic emission systems(AE),and 3 D digital image correlation monitoring technology(3 D-DIC).The intrinsic mechanism by which SS content influences the strength of SS-CPB was revealed through an analysis of its hydration reaction degree and microstructural characteristics under varying SS content.Moreover,a theoretical strength model incorporating different interface angles was developed to explore the impact of interface inclination on failure modes and mechanical strength.The main conclusions are as follows:The incorporation of SS enhances the plastic characteristics of RBCS and reduces its brittleness,with the increase of SS content,the stress-strain curve of RBCS in the“staircase-like”stag e becomes smoother;When the interface angle is 45°,the RBCS stress-strain curve exhibits a bimodal feature,and the failure mode changes from Y-shaped fractures to interface and axial splitting;The addition of SS results in a reduction of hydration products such as Ca(OH)_(2) in the backfill cementing system and an increase in harmful pores,which weakens the bonding performance and strength of RBCS,and the SS content should not exceed 45%;As the interface angle increases,the strength of RBCS decreases,and the critical interface slip angle decreases first and then increases with the increase in the E S/E R ratio.This study provides technical references for the large-scale application of SS in mine backfill.
基金Project(200809123) supported by the National Natural Science Foundation of China
文摘A high speed steel composite roll billet was fabricated, which is regular in shape, smooth in surface, slight in trace, compact in internal structure, free of slag inclusion, shrinkage cavity, cracks and other flaws, and good in macro quality of junction surface using a vertical continuous casting machine. The interface zone microstructure of bimetallic in billet of high speed steel composite roll was analyzed by metallurgical microscope(OM), X-ray diffractmeter(XRD), scanning electron microscopy(SEM) and energy-dispersive X-ray analysis(EDS). The results indicate that the microstructure of roll billet is composed of chilled solidified layer, dendrite zone, interfacial zone of bimetal and core material zone. The microstructure of outer shell material is composed of martensite + bainite + residual austenite + some small labyrinth-shape, small-short lath-shape, or dollop-shape eutectic carbides. The microstructure of core material is slice-shape pearlite and a little ferrite along boundary of cells. The interface region microstructure of bimetallic composite roll consists of diffusion region, chilled solidified layer and columnar grain region.
基金Project(2009ZM0296) supported by the Fundamental Research Funds for the Central Universities in China
文摘Abstract： An alloy steel/alumina composite was successfully fabricated by pressureless infiltration of X10CrNil8-8 steel melt on 30% （mass fraction） Ni-containing alumina based composite ceramic （Ni/Al2O3） at 1 600 ℃. The infiltration quality and interfacial bonding behavior were investigated by SEM, EDS, XRD and tensile tests. The results show that there is an obvious interfacial reaction layer between the alloying steel and the Ni/Al2O3 composite ceramic. The interfacial reactive products are （FexAly）3O4 intermetallic phase and （AlxCry）2O3 solid solution. The interracial bonding strength is as high as about 67.5 MPa. The bonding mechanism of X10CrNi 18-8 steel with the composite ceramic is that Ni inside the ceramic bodies dissolves into the alloy melt and transforms into liquid channels, consequently inducing the steel melt infiltrating and filling in the pores and the liquid channels. Moreover, the metallurgical bonding and interfacial reactive bonding also play a key role on the stability of the bonding interface.
基金Project(51175424) supported by the National Natural Science FoundationProject(B07050) supported by the 111 Project,ChinaProject (JC20110257) supported by the Basic Research Foundation of Northwestern Polytechnical University
文摘Carrying on a series of compression and shear tests by a large number of specimens, reliabilities of T300/QY8911 laminated composite were studied when dispersibility models were described. The results show that the stress is linearly dependent on the strain and the damage modes of specimens are brittle fracture for both kinds of tests. Dispersibility models of compression and shear strength are expressed as Re-N（415.39, 6 586.36） and Rs-ln（5.071 8, 0.155 3）, respectively. When normal and lognormal distributions were used to describe the dispersibility models of compression and shear strength, and the compression or shear load follows the normal distribution, the almost same failure probability can be obtained from different reliability analysis methods.
基金Projects(20120094110005,20120094130003)supported by the Research Fund for the Doctoral Program of Higher Education of ChinaProjects(51379068,51139001,51279052,51209077,51179066)supported by the National Natural Science Foundation of China+1 种基金Project(NCET-11-0628)supported by the Program for New Century Excellent Talents in University,ChinaProjects(201201038,201101013)supported by the Public Welfare Industry Research Special Fund Project of Ministry of Water Resources of China
文摘To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring artificial boundary(VSAB) is adopted to simulate the radiation damping of their infinite foundations, and based on the Marc software, a simplified seismic motion input method is presented by the equivalent nodal loads. Finally, based on the practical engineering of a RCC gravity dam, effects of radiation damping and construction interfaces on the dynamic characteristics of dams are investigated in detail. Analysis results show that dynamic response of the RCC gravity dam significantly reduces about 25% when the radiation damping of infinite foundation is considered. Hot interfaces and the normal cold interfaces have little influence on the dynamic response of the RCC gravity dam.However, nonlinear fracture along the cold interfaces at the dam heel will occur under the designed earthquake if the cold interfaces are combined poorly. Therefore, to avoid the fractures along the construction interfaces under the potential super earthquakes,combination quality of the RCC layers should be significantly ensured.
基金Project(50578027) supported by the National Natural Science Foundation of China
文摘The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interface. Fatigue properties of the composite beam under the action of negative moment were experimentally studied. Through inverted loading mode the load-beating state of a composite beam was simulated under the action of negative moment. With the ratios of constructional bars being 0, 0.082% and 0.164% respectively as parameters, the effects of constructional bars on the properties of composite beam, such as fatigue life, crack propagation, rigidity loss as well as damage behavior of bonding interface, were studied. The mechanism of the constructional bars on the fatigue properties of the composite beams and the restriction mechanism of crack widths and rigidity loss were analyzed. The test results show that the constructional bars can enhance the shear resistance of the bonding interface between composite layer and old concrete beam and restrict expanding of steel fiber reinforced self-stressing concrete, which are beneficial to synergistic action of composite layer and old concrete beam, to reducing the stress amplitude of bars and the crack width of composite layer, and to increasing the durability and fatigue life of the composite beam.
文摘The fracture behavior of polymer-bonded explosive(PBX) seriously affects the safety and reliability of weapon system.The effects of interface debonding and initial meso-damage on the fracture behavior of PBX under quasi-static tension are studied using numerical method.A twodimensional representative volume element(RVE) is established based on Voronoi model in which the component contents could be regulated and the particles are randomly distributed.A nonlinear damage model of polymer matrix relative to matrix depth between particles is constructed.The results show that the simulated strain-stress relation is coincident with experiment data.It is found that interface debonding leads to the nucleation and propagation of meso-cracks,and a main crack approximately perpendicular to the loading direction is generated finally.The interface debonding tends to occur in the interface perpendicular to the loading direction.There seems to be a phenomenon that strain softening and hardening alternatively appear around peak stress of stress and strain curve.It is shown that the initial damages of intragranular and interfacial cracks both decrease the modulus and failure stress,and the main crack tends to propagate toward the initial meso-cracks.
文摘Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.
基金Project supported by the Special Funding Support for the Development of 1500 Meter Subsea Christmas Tree and Control System,China。
文摘Improving interfacial bonding and alloying design are effective strategies for enhancing mechanical properties of particle-reinforced steel matrix composites(SMCs).This study prepared SMCs with uniformly distributed TiC_(P) in matrix using master alloying method.The TiC(002)/Fe(011)interface model was established based on the orientation relationship of(011)_(Fe)//(002)_(TiC),and[100]_(Fe)//[100]_(TiC).The effects of single and co-doping of alloying elements(Mn,Cr,Mo,Ni,Cu and Si)on the interface bonding behavior of TiC/Fe in composites were investigated in conjunction with first principles.The results demonstrate that the interface between TiC and matrix is continuous and stable.Compared to the undoped TiC/Fe interface,single-doping Mn,Cr,and Mo can improve the stability of TiC/Fe interface and enhance tensile strength.Conversely,single-doping with Ni,Cu,and Si reduced the interface stability and marginally reduces tensile strength.Relative to the undoped and singly Ni-doped TiC/Fe interfaces,the co-doping Ni-Mo boosts binding energy and separation work at the TiC/Fe interface,which is conducive to the interface bonding between TiC_(P) and matrix,and thus improves the mechanical properties of composites.Thus,in the alloying design of TiC particle reinforced low-alloy SMCs,incorporating Mn,Cr,Mo,and Ni into matrix can enhance the overall mechanical properties of composites.
