Dynamic load on anchoring structures(AS)within deep roadways can result in cumulative damage and failure.This study develops an experimental device designed to test AS under triaxial loads.The device enables the inves...Dynamic load on anchoring structures(AS)within deep roadways can result in cumulative damage and failure.This study develops an experimental device designed to test AS under triaxial loads.The device enables the investigation of the mechanical response,failure mode,instability assessment criteria,and anchorage effect of AS subjected to combined cyclic dynamic-static triaxial stress paths.The results show that the peak bearing strength is positively correlated with the anchoring matrix strength,anchorage length,and edgewise compressive strength.The bearing capacity decreases significantly when the anchorage direction is severely inclined.The free face failure modes are typically transverse cracking,concave fracturing,V-shaped slipping and detachment,and spallation detachment.Besides,when the anchoring matrix strength and the anchorage length decrease while the edgewise compressive strength,loading rate,and anchorage inclination angle increase,the failure intensity rises.Instability is determined by a negative tangent modulus of the displacement-strength curve or the continued deformation increase against the general downward trend.Under cyclic loads,the driving force that breaks the rock mass along the normal vector and the rigidity of the AS are the two factors that determine roadway stability.Finally,a control measure for surrounding rock stability is proposed to reduce the internal driving force via a pressure relief method and improve the rigidity of the AS by full-length anchorage and grouting modification.展开更多
The exploration of Mars would heavily rely on Martian rocks mechanics and engineering technology.As the mechanical property of Martian rocks is uncertain,it is of utmost importance to predict the probability distribut...The exploration of Mars would heavily rely on Martian rocks mechanics and engineering technology.As the mechanical property of Martian rocks is uncertain,it is of utmost importance to predict the probability distribution of Martian rocks mechanical property for the success of Mars exploration.In this paper,a fast and accurate probability distribution method for predicting the macroscale elastic modulus of Martian rocks was proposed by integrating the microscale rock mechanical experiments(micro-RME),accurate grain-based modeling(AGBM)and upscaling methods based on reliability principles.Firstly,the microstructure of NWA12564 Martian sample and elastic modulus of each mineral were obtained by micro-RME with TESCAN integrated mineral analyzer(TIMA)and nanoindentation.The best probability distribution function of the minerals was determined by Kolmogorov-Smirnov(K-S)test.Secondly,based on best distribution function of each mineral,the Monte Carlo simulations(MCS)and upscaling methods were implemented to obtain the probability distribution of upscaled elastic modulus.Thirdly,the correlation between the upscaled elastic modulus and macroscale elastic modulus obtained by AGBM was established.The accurate probability distribution of the macroscale elastic modulus was obtained by this correlation relationship.The proposed method can predict the probability distribution of Martian rocks mechanical property with any size and shape samples.展开更多
Mechanically lined pipe(MLP)is often used for offshore oil and gas transport because of its low cost and corrosion resistance.During installation and operation,the pipe may undergo severe bending deformation,which cau...Mechanically lined pipe(MLP)is often used for offshore oil and gas transport because of its low cost and corrosion resistance.During installation and operation,the pipe may undergo severe bending deformation,which causes the liner to separate from the outer pipe and buckles,affecting the stability of the whole line.In this paper,the buckling response of MLP subjected to bending is investigated to clarify its bending characteristics by employing both experiments,numerical simulation,as theoretical methods.Two types of MLPs were manufactured with GB 45 carbon steel(SLP)and Al 6061(ALP)used as the outer pipe material,respectively.The hydraulic expansion and bending experiments of small-scale MLPs are conducted.In addition to the ovalized shape of the cross-section for the SLP specimens,the copper liner was found to wrinkle on the compressive side.In contrast,the liner of ALP remains intact without developing any wrinkling and collapse mode.In addition,a dedicated numerical framework and theoretical models were also established.It was found both the manufacturing and bending responses of the MLP can be well reproduced,and the predicted maximum moment and critical curvatures are in good agreement with the experimental results.展开更多
The infamous type Ⅳ failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants.In this work,the traditional the...The infamous type Ⅳ failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants.In this work,the traditional thermo-mechanical treatment was modified via the replacement of hot-rolling with cold rolling,i.e.,normalizing,cold rolling,and tempering (NCT),which was developed to improve the creep strength of the FGHAZ in G115 steel weldments.The NCT treatment effectively promoted the dissolution of preformed M_(23)C_(6)particles and relieved the boundary segregation of C and Cr during welding thermal cycling,which accelerated the dispersed reprecipitation of M_(23)C_(6) particles within the fresh reaustenitized grains during post-weld heat treatment.In addition,the precipitation of Cu-rich phases and MX particles was promoted evidently due to the deformation-induced dislocations.As a result,the interacting actions between precipitates,dislocations,and boundaries during creep were reinforced considerably.Following this strategy,the creep rupture life of the FGHAZ in G115 steel weldments can be prolonged by 18.6%,which can further push the application of G115 steel in USC power plants.展开更多
To investigate the thermal and mechanical behavior of casting wheel,a two-dimensional thermoelastic-plastic finite element model was used to predict the temperature,stress and distortion distribution of the casting wh...To investigate the thermal and mechanical behavior of casting wheel,a two-dimensional thermoelastic-plastic finite element model was used to predict the temperature,stress and distortion distribution of the casting wheel during the wheel and belt continuous casting process.The effects of grinding thickness and casting speed on the thermal and mechanical behaviors of the center of the hot face of the casting wheel were discussed in detail.In each rotation,the casting wheel passes through four different spray zones.The results show that the temperature distribution of the casting wheel in different spray zones is similar,the temperature of the hot face is the highest and the temperature reaches the peak in the spray zoneⅢ.The stress and distortion depend on the temperature distribution,and the maximum stress and distortion of the hot face are 358.2 MPa and 1.82 mm,respectively.The temperature at the center of the hot face decreases with increasing grinding thickness and increases with increasing casting speed.展开更多
Mg-Gd-Y-Zr alloy,as a typical magnesium rare-earth(Mg-RE)alloy,is gaining popularity in the advanced equipment manufacturing fields owing to its noticeable age-hardening properties and high specific strength.However,i...Mg-Gd-Y-Zr alloy,as a typical magnesium rare-earth(Mg-RE)alloy,is gaining popularity in the advanced equipment manufacturing fields owing to its noticeable age-hardening properties and high specific strength.However,it is extremely challenging to prepare wrought components with large dimensions and complex shapes because of the poor room-temperature processability of Mg-Gd-Y-Zr alloy.Herein,we report a wire-arc directed energy deposited(DED)Mg-10.45Gd-2.27Y-0.52Zr(wt.%,GW102K)alloy with high RE content presenting a prominent combination of strength and ductility,realized by tailored nanoprecipitates through an optimized heat treatment procedure.Specifically,the solution-treated sample exhibits excellent ductility with an elongation(EL)of(14.6±0.1)%,while the aging-treated sample at 200°C for 58 h achieves an ultra-high ultimate tensile strength(UTS)of(371±1.5)MPa.Besides,the aging-treated sample at 250°C for 16 h attains a good strength-ductility synergy with a UTS of(316±2.1)MPa and a EL of(8.5±0.1)%.Particularly,the evolution mechanisms of precipitation response induced by various aging parameters and deformation behavior caused by nanoprecipitates type were also systematically revealed.The excellent ductility resulted from coordinating localized strains facilitated by active slip activity.And the ultra-high strength should be ascribed to the dense nano-β'hampering dislocation motion.Additionally,the shearable nano-β1 contributed to the good strength-ductility synergy.This work thus offers insightful understanding into the nanoprecipitates manipulation and performance tailoring for the wire-arc DED preparation of large-sized Mg-Gd-Y-Zr components with complex geometries.展开更多
To explore the wide-frequency damping and vibration-attenuation performances in the application of aerospace components,the cylindrical sandwich shell structure with a gradient core of entangled wire mesh was proposed...To explore the wide-frequency damping and vibration-attenuation performances in the application of aerospace components,the cylindrical sandwich shell structure with a gradient core of entangled wire mesh was proposed in this paper.Firstly,the gradient cores of entangled wire mesh in the axial and radial directions were prepared by using an in-house Numerical Control weaving machine,and the metallurgical connection between skin sheets and the gradient core was performed using vacuum brazing.Secondly,to investigate the mechanical properties of cylindrical sandwich shells with axial or radial gradient cores,quasi-static and dynamic mechanical experiments were carried out.The primary evaluations of mechanical properties include secant stiffness,natural frequency,Specific Energy Absorption(SEA),vibration acceleration level,and so on.The results suggest that the vibration-attenuation performance of the sandwich shell is remarkable when the high-density core layer is at the end of the shell or abuts the inner skin.The axial gradient material has almost no influence on the vibration frequencies of the shell,whereas the vibration frequencies increase dramatically when the high-density core layer approaches the skin.Moreover,compared to the conventional sandwich shells,the proposed functional grading cylindrical sandwich shell exhibits more potential in mass reduction,stiffness designing,and energy dissipation.展开更多
Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV...Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures.In addition,UV treatment can significantly passivate the primary Mn-rich Al15Mn3Si2 intermetallics.The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed.Compared with the gravity die-cast alloys,the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures.These results can be attributed to the refinement of theα(Al)grains and the secondary intermetallics,the increased proportion of refined heat-resistant precipitates,and the formation of nano-sized Si particles.The ultimate tensile strength of the UV treated alloys at 350℃ exceeds that of commercial piston alloys.This indicates the high application potential of the developed piston alloys in density diesel engines.展开更多
The torque ripples resulting from external electromagnetic excitation and mechanical internal excitation contribute to significant torsional vibration issues within electromechanical coupling systems.To mitigate these...The torque ripples resulting from external electromagnetic excitation and mechanical internal excitation contribute to significant torsional vibration issues within electromechanical coupling systems.To mitigate these fluctuations,a passive control strategy centered around a multi-stable nonlinear energy sink(MNES)is proposed.First,models for electromagnetic torque,gear nonlinear meshing torque,and misalignment torque are established.Building upon this foundation,an electromechanical coupling dynamic model of the electric drive system is formulated.Sensitivity analysis is conducted to determine the sensitive nodes of each mode and to provide guidance for the installation of the MNES.The structure of the MNES is introduced,and an electromechanical coupling dynamic model with the MNES is established.Based on this model,the influence of the misaligned angle on the electromechanical coupling characteristics is analyzed.In addition,the vibration suppression performance of the MNES is studied under both speed and uniform speed conditions.Finally,experimental testing is conducted to verify the vibration suppression performance of the MNES.The results indicate that misalignment triggers the emergence of its characteristic frequencies and associated sidebands.Meanwhile,the MNES effectively mitigates the torsional vibrations in the coupled system,demonstrating suppression rates of 52.69%in simulations and 63.3%in experiments.展开更多
A three-dimensional(3D)thermomechanical vibration model is developed for rotating pre-twisted functionally graded(FG)microbeams according to the refined shear deformation theory(RSDT)and the modified couple stress the...A three-dimensional(3D)thermomechanical vibration model is developed for rotating pre-twisted functionally graded(FG)microbeams according to the refined shear deformation theory(RSDT)and the modified couple stress theory(MCST).The material properties are assumed to follow a power-law distribution along the chordwise direction.The model introduces one axial stretching variable and four transverse deflection variables including two pure bending components and two pure shear ones.The complex modal analysis and assumed mode methods are used to solve the governing equations of motion under different boundary conditions(BCs).Several examples are presented to verify the effectiveness of the developed model.By coupling the slenderness ratio,gradient index,rotation speed,and size effect with the pre-twisted angle,the effects of these factors on the thermomechanical vibration of the microbeam with different BCs are investigated.It is found that with the increase in the pre-twisted angle,the critical slenderness ratio and gradient index corresponding to the thermal instability of the microbeam increase,while the critical material length scale parameter(MLSP)and rotation speed decrease.The sensitivity of the fundamental frequency to temperature increases with the increasing slenderness ratio and gradient index,and decreases with the other increasing parameters.Moreover,the size effect can suppress the dynamic stiffening effect and enhance the Coriolis effect.Finally,the mode transition is quantitatively demonstrated by a modal assurance criterion(MAC).展开更多
A novel double side friction stir Z shape lap-butt welding(DS-FSZW)process was proposed to achieve excellent mechanical properties of Al/Cu medium-thick dissimilar joints.The influence of welding parameters on weld mi...A novel double side friction stir Z shape lap-butt welding(DS-FSZW)process was proposed to achieve excellent mechanical properties of Al/Cu medium-thick dissimilar joints.The influence of welding parameters on weld microstructure and properties of DS-FSZW joint were systematically investigated.It indicated that defect-free medium-thick Al/Cu DS-FSZW joint could be achieved under an optimal welding parameter.DS-FSZW joint was prone to form void defects in the bottom of the second-pass weld.The recrystallization mechanisms at the top and middle of the weld nugget zone(WNZ)were continuous dynamic recrystallization(CDRX)and geometric dynamic recrystallization(GDRX).While the major recrystallization mechanism at the bottom of the WNZ was GDRX.DS-FSZW joint of the optimal welding condition with 850 r/min-400 mm/min was produced with a continuous thin and crack-free IMCs layer at the Al/Cu interface,and the maximum tensile strength of this joint is 160.57 MPa,which is equivalent to 65.54%of pure Cu base material.Moreover,the corrosion resistance of Al/Cu DS-FSZW joints also achieved its maximum value at the optimal welding parameter of 850 r/min-400 mm/min.It demonstrates that the DS-FSZW process can simultaneously produce medium-thick Al/Cu joints with excellent mechanical performance and corrosion resistance.展开更多
The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,a...The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,and high-cycle fatigue properties,were studied.The results showed that the LSP induced residual compressive stresses on the surface and near surface of the material.The maximum surface residual compressive stress was−661 MPa,and the compressive-stress-affected depth was greater than 1000μm.The roughness and Vickers micro-hardness increased with the number of shocks,and the maximum hardness-affected depth was about 700μm after three LSP treatments.LSP enhanced the fraction of low-angle grain boundaries,changed the grain preferred orientations,and notably increased the pole density ofαphase on the near surface from 2.41 to 3.46.The surface hardness values of the LSP samples increased with the increase of the number of shocks due to work hardening,while the LSP had a limited effect on the tensile properties.The high-cycle fatigue life of the LSP-treated sample was significantly enhanced by more than 20%compared with that of the untreated sample,which was caused by the suppression of the initiation and propagation of fatigue cracks.展开更多
Because inferior mechanical strength of granite polymer composite(GPC)has become the main drawback limiting its application and popularization,Mo fibers were added into(GPC)to improve its mechanical strength.Mechanica...Because inferior mechanical strength of granite polymer composite(GPC)has become the main drawback limiting its application and popularization,Mo fibers were added into(GPC)to improve its mechanical strength.Mechanical properties of matrix materials with different mass ratio of resin and stabilizer(MRRS)were investigated systematically.The influences of MRRS on interface bonding strength of Mo fiber-matrix,wettability and mechanical strength of GPC were discussed,respectively,and the theoretical calculation result of MRRS k was obtained,with the optimal value of k=4.When k=4,tensile strength,tensile strain and fracture stress of the cured resin achieve the maximum values.But for k=7,the corresponding values reach the minimum.With the increase of MRRS k,surface free energy of the cured resin first increases and then decreases,while contact angles between Mo sample and matrix have displayed the opposite trend.Wettability of resin to Mo fiber is the best at k=4.Pulling load of Mo fiber and interface bonding strength appear the maximum at k=4,followed by k=5,k=3 the third,and k=7 the minimum.When k=4,mechanical properties of Mo fiber-reinforced GPC are optimal,which is consistent with the result of theoretical calculation.This study is of great significance to get better component formulas of Mo fiber reinforced GPC and to improve its application in machine tools.展开更多
FeCoCrNiMox composite powders were prepared using the mechanical alloying technique and made into high-entropy alloy(HEA)coatings with the face-centered cubic phase using plasma spraying to address the element segrega...FeCoCrNiMox composite powders were prepared using the mechanical alloying technique and made into high-entropy alloy(HEA)coatings with the face-centered cubic phase using plasma spraying to address the element segregation problem in HEAs and pre-pare uniform HEA coatings.Scanning electron microscopy,transmission electron microscopy,and X-ray diffractometry were employed to characterize these coatings’microstructure and phase composition.The hardness,elastic modulus,and fracture toughness of coatings were tested,and the corrosion resistance was analyzed in simulated seawater.Results show that the hardness of the coating is HV0.1606.15,the modulus of elasticity is 128.42 GPa,and the fracture toughness is 43.98 MPa·m^(1/2).The corrosion potential of the coating in 3.5wt%NaCl solution is-0.49 V,and the corrosion current density is 1.2×10^(−6)A/cm^(2).The electrochemical system comprises three parts:the electrolyte,the adsorption and metallic oxide films produced during immersion,and the FeCoNiCrMo HEA coating.Over in-creasingly long periods,the corrosion reaction rate increases first and then decreases,the corrosion product film comprising metal oxides reaches a dynamic balance between formation and dissolution,and the internal reaction of the coating declines.展开更多
Automobiles are the inevitable mode of transportation.However,increasing fuel prices and carbon dioxide emissions are posing a serious threat to automobile users and the environment.Thus,the development of new lightwe...Automobiles are the inevitable mode of transportation.However,increasing fuel prices and carbon dioxide emissions are posing a serious threat to automobile users and the environment.Thus,the development of new lightweight materials has been a key area of research.Magnesium-based commercial alloys(AZ and ZK series alloys)are the lightest among all structural metals.However,there is still a question about the replacement of Aluminum-based alloys due to HCP crystal structure.In this connection,Mg-Al-Ca-Mn(AXM)Mg alloy can be a choice as an alternative to the existing Mg-based commercial alloys for structural applications.It contains(Al,Mg)_(2)Ca,Al_(2)Ca,Mg_(2)Ca,and Al_(8)Mn_(5)as the secondary phases,contributing to the microstructural refinement and property enhancement.However,the formation of those precipitates depends on the amount of Al,Ca,and Mn,especially,the Ca/Al ratio.In addition,the secondary processes influence the grain refinement and property enhancement of texture modifications.Hence,this review article focuses on elaborating on the significance of the Ca/Al ratio for the precipitate formation,secondary process,and texture modifications.The co-segregation behavior of other micro-alloying elements like Cerium,Lanthanum,and Zinc in AXM Mg alloy systems has also been discussed for property enhancement.展开更多
As the basic protective element, steel plate had attracted world-wide attention because of frequent threats of explosive loads. This paper reports the relationships between microscopic defects of Q345 steel plate unde...As the basic protective element, steel plate had attracted world-wide attention because of frequent threats of explosive loads. This paper reports the relationships between microscopic defects of Q345 steel plate under the explosive load and its macroscopic dynamics simulation. Firstly, the defect characteristics of the steel plate were investigated by stereoscopic microscope(SM) and scanning electron microscope(SEM). At the macroscopic level, the defect was the formation of cave which was concentrated in the range of 0-3.0 cm from the explosion center, while at the microscopic level, the cavity and void formation were the typical damage characteristics. It also explains that the difference in defect morphology at different positions was the combining results of high temperature and high pressure. Secondly, the variation rules of mechanical properties of steel plate under explosive load were studied. The Arbitrary Lagrange-Euler(ALE) algorithm and multi-material fluid-structure coupling method were used to simulate the explosion process of steel plate. The accuracy of the method was verified by comparing the deformation of the simulation results with the experimental results, the pressure and stress at different positions on the surface of the steel plate were obtained. The simulation results indicated that the critical pressure causing the plate defects may be approximately 2.01 GPa. On this basis, it was found that the variation rules of surface pressure and microscopic defect area of the Q345 steel plate were strikingly similar, and the corresponding mathematical relationship between them was established. Compared with Monomolecular growth fitting models(MGFM) and Logistic fitting models(LFM), the relationship can be better expressed by cubic polynomial fitting model(CPFM). This paper illustrated that the explosive defect characteristics of metal plate at the microscopic level can be explored by analyzing its macroscopic dynamic mechanical response.展开更多
Two-dimensional(2D)materials are potential candidates for electronic devices due to their unique structures and exceptional physical properties,making them a focal point in nanotechnology research.Accurate assessment ...Two-dimensional(2D)materials are potential candidates for electronic devices due to their unique structures and exceptional physical properties,making them a focal point in nanotechnology research.Accurate assessment of the mechanical and tribological properties of 2D materials is imperative to fully exploit their potential across diverse applications.However,their nanoscale thickness and planar nature pose significant challenges in testing and characterizing their mechanical properties.Among the in situ characterization techniques,atomic force microscopy(AFM)has gained widespread applications in exploring the mechanical behaviour of nanomaterials,because of the easy measurement capability of nano force and displacement from the AFM tips.Specifically,AFM-based force spectroscopy is a common approach for studying the mechanical and tribological properties of 2D materials.This review comprehensively details the methods based on normal force spectroscopy,which are utilized to test and characterize the elastic and fracture properties,adhesion,and fatigue of 2D materials.Additionally,the methods using lateral force spectroscopy can characterize the interfacial properties of 2D materials,including surface friction of 2D materials,shear behaviour of interlayers as well as nanoflake-substrate interfaces.The influence of various factors,such as testing methods,external environments,and the properties of test samples,on the measured mechanical properties is also addressed.In the end,the current challenges and issues in AFM-based measurements of mechanical and tribological properties of 2D materials are discussed,which identifies the trend in the combination of multiple methods concerning the future development of the in situ testing techniques.展开更多
We employed a melt ultrasonic treatment near the liquidus to prepare a high-thermal-conductivity Al-4Si-2Ni-0.8Fe-0.4Mg alloy.The influences of various ultrasonic powers on its microstructure,mechanical properties,and...We employed a melt ultrasonic treatment near the liquidus to prepare a high-thermal-conductivity Al-4Si-2Ni-0.8Fe-0.4Mg alloy.The influences of various ultrasonic powers on its microstructure,mechanical properties,and thermal conductivity were investigated.It is shown that near-liquidus ultrasonication significantly refines the alloy grains and eutectic structure,synergistically improving the alloy’s mechanical properties and thermal conductivity.Specifically,the grain size decreased by 84.5%from 941.4 to 186.2μm.Increasing the ultrasonic power improved the thermal conductivity of the alloy slightly and significantly enhanced its mechanical properties.At an ultrasonic power of 2100 W,the tensile strength,yield strength,elongation rate,and thermal conductivity were 216 MPa,142 MPa,6.3%,and 169 W/(m·k),respectively.展开更多
As an important component of the running gear of high-speed trains,axle box bearings can cause lubricating grease failure and damage to bearing components under continuous high-temperature operation,which will affect ...As an important component of the running gear of high-speed trains,axle box bearings can cause lubricating grease failure and damage to bearing components under continuous high-temperature operation,which will affect the normal operation of highspeed trains.Therefore,bearing temperature is one of the key parameters to be monitored in the online monitoring system for trains.Based on the thermal network method,this paper establishes a thermal network model for the axle box bearing,considering the radial thermal deformation of the double-row tapered roller bearing components caused by the oil film characteristics and the temperature variations of the lubricating grease.A thermo-mechanical coupling model for the grease-lubricated double-row tapered roller axle box bearing of high-speed trains with track irregularity excitation is established.The correctness of the model is verified using the test bench data,and the temperature of the bearing at different rotational speeds,loads,fault sizes,and ambient temperatures are investigated.展开更多
Al Si10Mg porous protective structure often produces different damage forms under compressive loading,and these damage modes affect its protective function.In order to well meet the service requirements,there is an ur...Al Si10Mg porous protective structure often produces different damage forms under compressive loading,and these damage modes affect its protective function.In order to well meet the service requirements,there is an urgent need to comprehensively understand the mechanical behavior and response mechanism of AlSi10Mg porous structures under compressive loading.In this paper,Al Si10Mg porous structures with three kinds of volume fractions are designed and optimized to meet the requirements of high-impact,strong-energy absorption,and lightweight characteristics.The mechanical behaviors of AlSi10Mg porous structures,including the stress-strain relationship,structural bearing state,deformation and damage modes,and energy absorption characteristics,were obtained through experimental studies at different loading rates.The damage pattern of the damage section indicates that AlSi10Mg porous structures have both ductile and brittle mechanical properties.Numerical simulation studies show that the AlSi10Mg porous structure undergoes shear damage due to relative misalignment along the diagonal cross-section,and the damage location is almost at 45°to the load direction,which is the most direct cause of its structural damage,revealing the damage mechanism of AlSi10Mg porous structures under the compressive load.The normalized energy absorption model constructed in the paper well interprets the energy absorption state of Al Si10Mg porous structures and gives the sensitive location of the structures,and the results of this paper provide important references for peers in structural design and optimization.展开更多
基金This paper is financially supported by the National Natural Science Foundation of China(Grant Nos.52074263 and 52034007)the Postgraduate Research and Practice Innovation Program of Jiangsu Province(Grant No.KYCX21_2332).
文摘Dynamic load on anchoring structures(AS)within deep roadways can result in cumulative damage and failure.This study develops an experimental device designed to test AS under triaxial loads.The device enables the investigation of the mechanical response,failure mode,instability assessment criteria,and anchorage effect of AS subjected to combined cyclic dynamic-static triaxial stress paths.The results show that the peak bearing strength is positively correlated with the anchoring matrix strength,anchorage length,and edgewise compressive strength.The bearing capacity decreases significantly when the anchorage direction is severely inclined.The free face failure modes are typically transverse cracking,concave fracturing,V-shaped slipping and detachment,and spallation detachment.Besides,when the anchoring matrix strength and the anchorage length decrease while the edgewise compressive strength,loading rate,and anchorage inclination angle increase,the failure intensity rises.Instability is determined by a negative tangent modulus of the displacement-strength curve or the continued deformation increase against the general downward trend.Under cyclic loads,the driving force that breaks the rock mass along the normal vector and the rigidity of the AS are the two factors that determine roadway stability.Finally,a control measure for surrounding rock stability is proposed to reduce the internal driving force via a pressure relief method and improve the rigidity of the AS by full-length anchorage and grouting modification.
文摘The exploration of Mars would heavily rely on Martian rocks mechanics and engineering technology.As the mechanical property of Martian rocks is uncertain,it is of utmost importance to predict the probability distribution of Martian rocks mechanical property for the success of Mars exploration.In this paper,a fast and accurate probability distribution method for predicting the macroscale elastic modulus of Martian rocks was proposed by integrating the microscale rock mechanical experiments(micro-RME),accurate grain-based modeling(AGBM)and upscaling methods based on reliability principles.Firstly,the microstructure of NWA12564 Martian sample and elastic modulus of each mineral were obtained by micro-RME with TESCAN integrated mineral analyzer(TIMA)and nanoindentation.The best probability distribution function of the minerals was determined by Kolmogorov-Smirnov(K-S)test.Secondly,based on best distribution function of each mineral,the Monte Carlo simulations(MCS)and upscaling methods were implemented to obtain the probability distribution of upscaled elastic modulus.Thirdly,the correlation between the upscaled elastic modulus and macroscale elastic modulus obtained by AGBM was established.The accurate probability distribution of the macroscale elastic modulus was obtained by this correlation relationship.The proposed method can predict the probability distribution of Martian rocks mechanical property with any size and shape samples.
基金Fofinancially supported by the National Natural Science Foundation of China(Grant No.52271288)Peiyang Scholar Initiation Fund from Tianjin University。
文摘Mechanically lined pipe(MLP)is often used for offshore oil and gas transport because of its low cost and corrosion resistance.During installation and operation,the pipe may undergo severe bending deformation,which causes the liner to separate from the outer pipe and buckles,affecting the stability of the whole line.In this paper,the buckling response of MLP subjected to bending is investigated to clarify its bending characteristics by employing both experiments,numerical simulation,as theoretical methods.Two types of MLPs were manufactured with GB 45 carbon steel(SLP)and Al 6061(ALP)used as the outer pipe material,respectively.The hydraulic expansion and bending experiments of small-scale MLPs are conducted.In addition to the ovalized shape of the cross-section for the SLP specimens,the copper liner was found to wrinkle on the compressive side.In contrast,the liner of ALP remains intact without developing any wrinkling and collapse mode.In addition,a dedicated numerical framework and theoretical models were also established.It was found both the manufacturing and bending responses of the MLP can be well reproduced,and the predicted maximum moment and critical curvatures are in good agreement with the experimental results.
基金financially supported by the National Key R&D Program of China(No.2022YFB3705300)the National Natural Science Foundation of China(Nos.U1960204 and 51974199)the Postdoctoral Fellowship Program of CPSF(No.GZB20230515)。
文摘The infamous type Ⅳ failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants.In this work,the traditional thermo-mechanical treatment was modified via the replacement of hot-rolling with cold rolling,i.e.,normalizing,cold rolling,and tempering (NCT),which was developed to improve the creep strength of the FGHAZ in G115 steel weldments.The NCT treatment effectively promoted the dissolution of preformed M_(23)C_(6)particles and relieved the boundary segregation of C and Cr during welding thermal cycling,which accelerated the dispersed reprecipitation of M_(23)C_(6) particles within the fresh reaustenitized grains during post-weld heat treatment.In addition,the precipitation of Cu-rich phases and MX particles was promoted evidently due to the deformation-induced dislocations.As a result,the interacting actions between precipitates,dislocations,and boundaries during creep were reinforced considerably.Following this strategy,the creep rupture life of the FGHAZ in G115 steel weldments can be prolonged by 18.6%,which can further push the application of G115 steel in USC power plants.
基金financially supported by the National Natural Science Foundation of China(Grant No.U20A20289)the Innovative Research Groups Project of the Natural Science Foundation of Hebei Province(Grant No.E2021203011)the Central Government Guides Local Science and Technology Development Fund Project(Grant No.206Z1601G)。
文摘To investigate the thermal and mechanical behavior of casting wheel,a two-dimensional thermoelastic-plastic finite element model was used to predict the temperature,stress and distortion distribution of the casting wheel during the wheel and belt continuous casting process.The effects of grinding thickness and casting speed on the thermal and mechanical behaviors of the center of the hot face of the casting wheel were discussed in detail.In each rotation,the casting wheel passes through four different spray zones.The results show that the temperature distribution of the casting wheel in different spray zones is similar,the temperature of the hot face is the highest and the temperature reaches the peak in the spray zoneⅢ.The stress and distortion depend on the temperature distribution,and the maximum stress and distortion of the hot face are 358.2 MPa and 1.82 mm,respectively.The temperature at the center of the hot face decreases with increasing grinding thickness and increases with increasing casting speed.
基金National Natural Science Foundation of China (52275374, 52205414)Xi’an Jiaotong University Basic Research Funds for Freedom of Exploration and Innovation-Student Programs (xzy022023066)+3 种基金Key Research and Development Projects of Shaanxi Province (2023-YBGY-361)Young Elite Scientists Sponsorship Program by CAST (2021QNRC001)State Key Laboratory for Mechanical Behavior of Materials (20212311)Xiaomi Foundation through Xiaomi Young Scholar Program
文摘Mg-Gd-Y-Zr alloy,as a typical magnesium rare-earth(Mg-RE)alloy,is gaining popularity in the advanced equipment manufacturing fields owing to its noticeable age-hardening properties and high specific strength.However,it is extremely challenging to prepare wrought components with large dimensions and complex shapes because of the poor room-temperature processability of Mg-Gd-Y-Zr alloy.Herein,we report a wire-arc directed energy deposited(DED)Mg-10.45Gd-2.27Y-0.52Zr(wt.%,GW102K)alloy with high RE content presenting a prominent combination of strength and ductility,realized by tailored nanoprecipitates through an optimized heat treatment procedure.Specifically,the solution-treated sample exhibits excellent ductility with an elongation(EL)of(14.6±0.1)%,while the aging-treated sample at 200°C for 58 h achieves an ultra-high ultimate tensile strength(UTS)of(371±1.5)MPa.Besides,the aging-treated sample at 250°C for 16 h attains a good strength-ductility synergy with a UTS of(316±2.1)MPa and a EL of(8.5±0.1)%.Particularly,the evolution mechanisms of precipitation response induced by various aging parameters and deformation behavior caused by nanoprecipitates type were also systematically revealed.The excellent ductility resulted from coordinating localized strains facilitated by active slip activity.And the ultra-high strength should be ascribed to the dense nano-β'hampering dislocation motion.Additionally,the shearable nano-β1 contributed to the good strength-ductility synergy.This work thus offers insightful understanding into the nanoprecipitates manipulation and performance tailoring for the wire-arc DED preparation of large-sized Mg-Gd-Y-Zr components with complex geometries.
基金Supports from the National Natural Science Foundation of China(Grant No.12272094,No.52205185 and No.51975123)the Natural Science Foundation of Fujian Province of China(Grant No.2022J01541 and No.2020J05102)the Key Project of National Defence Innovation Zone of Science and Technology Commission of CMC(Grant No.XXX-033-01)。
文摘To explore the wide-frequency damping and vibration-attenuation performances in the application of aerospace components,the cylindrical sandwich shell structure with a gradient core of entangled wire mesh was proposed in this paper.Firstly,the gradient cores of entangled wire mesh in the axial and radial directions were prepared by using an in-house Numerical Control weaving machine,and the metallurgical connection between skin sheets and the gradient core was performed using vacuum brazing.Secondly,to investigate the mechanical properties of cylindrical sandwich shells with axial or radial gradient cores,quasi-static and dynamic mechanical experiments were carried out.The primary evaluations of mechanical properties include secant stiffness,natural frequency,Specific Energy Absorption(SEA),vibration acceleration level,and so on.The results suggest that the vibration-attenuation performance of the sandwich shell is remarkable when the high-density core layer is at the end of the shell or abuts the inner skin.The axial gradient material has almost no influence on the vibration frequencies of the shell,whereas the vibration frequencies increase dramatically when the high-density core layer approaches the skin.Moreover,compared to the conventional sandwich shells,the proposed functional grading cylindrical sandwich shell exhibits more potential in mass reduction,stiffness designing,and energy dissipation.
基金the National Natural Science Foundation of China(No.52265043)Science and Technology Plan,Guizhou Province,China(No.ZK2021(267))+2 种基金Technology Achievements Application and Industrialization Project,Guizhou Province,China(No.2021(067))Cultivation Project of Guizhou University,China(No.2019(23))Lastly,we thank the Shanghai Synchrotron Radiation Facility(SSRF)for providing the synchrotron radiation beamtime.
文摘Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures.In addition,UV treatment can significantly passivate the primary Mn-rich Al15Mn3Si2 intermetallics.The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed.Compared with the gravity die-cast alloys,the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures.These results can be attributed to the refinement of theα(Al)grains and the secondary intermetallics,the increased proportion of refined heat-resistant precipitates,and the formation of nano-sized Si particles.The ultimate tensile strength of the UV treated alloys at 350℃ exceeds that of commercial piston alloys.This indicates the high application potential of the developed piston alloys in density diesel engines.
基金Project supported by the National Natural Science Foundation of China(Nos.52075084 and 52475094)the Fundamental Research Funds for the Central Universities of China(No.N2303005)。
文摘The torque ripples resulting from external electromagnetic excitation and mechanical internal excitation contribute to significant torsional vibration issues within electromechanical coupling systems.To mitigate these fluctuations,a passive control strategy centered around a multi-stable nonlinear energy sink(MNES)is proposed.First,models for electromagnetic torque,gear nonlinear meshing torque,and misalignment torque are established.Building upon this foundation,an electromechanical coupling dynamic model of the electric drive system is formulated.Sensitivity analysis is conducted to determine the sensitive nodes of each mode and to provide guidance for the installation of the MNES.The structure of the MNES is introduced,and an electromechanical coupling dynamic model with the MNES is established.Based on this model,the influence of the misaligned angle on the electromechanical coupling characteristics is analyzed.In addition,the vibration suppression performance of the MNES is studied under both speed and uniform speed conditions.Finally,experimental testing is conducted to verify the vibration suppression performance of the MNES.The results indicate that misalignment triggers the emergence of its characteristic frequencies and associated sidebands.Meanwhile,the MNES effectively mitigates the torsional vibrations in the coupled system,demonstrating suppression rates of 52.69%in simulations and 63.3%in experiments.
基金the National Natural Science Foundation of China(Nos.11602204 and 12102373)the Fundamental Research Funds for the Central Universities of China(Nos.2682022ZTPY081 and 2682022CX056)the Natural Science Foundation of Sichuan Province of China(Nos.2023NSFSC0849,2023NSFSC1300,2022NSFSC1938,and 2022NSFSC2003)。
文摘A three-dimensional(3D)thermomechanical vibration model is developed for rotating pre-twisted functionally graded(FG)microbeams according to the refined shear deformation theory(RSDT)and the modified couple stress theory(MCST).The material properties are assumed to follow a power-law distribution along the chordwise direction.The model introduces one axial stretching variable and four transverse deflection variables including two pure bending components and two pure shear ones.The complex modal analysis and assumed mode methods are used to solve the governing equations of motion under different boundary conditions(BCs).Several examples are presented to verify the effectiveness of the developed model.By coupling the slenderness ratio,gradient index,rotation speed,and size effect with the pre-twisted angle,the effects of these factors on the thermomechanical vibration of the microbeam with different BCs are investigated.It is found that with the increase in the pre-twisted angle,the critical slenderness ratio and gradient index corresponding to the thermal instability of the microbeam increase,while the critical material length scale parameter(MLSP)and rotation speed decrease.The sensitivity of the fundamental frequency to temperature increases with the increasing slenderness ratio and gradient index,and decreases with the other increasing parameters.Moreover,the size effect can suppress the dynamic stiffening effect and enhance the Coriolis effect.Finally,the mode transition is quantitatively demonstrated by a modal assurance criterion(MAC).
基金Supported by National Natural Science Foundation of China(Grant Nos.52275349,52035005)Key Research and Development Program of Shandong Province of China(Grant No.2021ZLGX01)Qilu Young Scholar Program of Shandong University of China.
文摘A novel double side friction stir Z shape lap-butt welding(DS-FSZW)process was proposed to achieve excellent mechanical properties of Al/Cu medium-thick dissimilar joints.The influence of welding parameters on weld microstructure and properties of DS-FSZW joint were systematically investigated.It indicated that defect-free medium-thick Al/Cu DS-FSZW joint could be achieved under an optimal welding parameter.DS-FSZW joint was prone to form void defects in the bottom of the second-pass weld.The recrystallization mechanisms at the top and middle of the weld nugget zone(WNZ)were continuous dynamic recrystallization(CDRX)and geometric dynamic recrystallization(GDRX).While the major recrystallization mechanism at the bottom of the WNZ was GDRX.DS-FSZW joint of the optimal welding condition with 850 r/min-400 mm/min was produced with a continuous thin and crack-free IMCs layer at the Al/Cu interface,and the maximum tensile strength of this joint is 160.57 MPa,which is equivalent to 65.54%of pure Cu base material.Moreover,the corrosion resistance of Al/Cu DS-FSZW joints also achieved its maximum value at the optimal welding parameter of 850 r/min-400 mm/min.It demonstrates that the DS-FSZW process can simultaneously produce medium-thick Al/Cu joints with excellent mechanical performance and corrosion resistance.
基金the National Natural Science Foundation of China(No.52205240).
文摘The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,and high-cycle fatigue properties,were studied.The results showed that the LSP induced residual compressive stresses on the surface and near surface of the material.The maximum surface residual compressive stress was−661 MPa,and the compressive-stress-affected depth was greater than 1000μm.The roughness and Vickers micro-hardness increased with the number of shocks,and the maximum hardness-affected depth was about 700μm after three LSP treatments.LSP enhanced the fraction of low-angle grain boundaries,changed the grain preferred orientations,and notably increased the pole density ofαphase on the near surface from 2.41 to 3.46.The surface hardness values of the LSP samples increased with the increase of the number of shocks due to work hardening,while the LSP had a limited effect on the tensile properties.The high-cycle fatigue life of the LSP-treated sample was significantly enhanced by more than 20%compared with that of the untreated sample,which was caused by the suppression of the initiation and propagation of fatigue cracks.
基金Fouded by the National Natural Science Foundation of China(No.51175308)the National Science and Technology Major Project of China(No.2012ZX04010032)。
文摘Because inferior mechanical strength of granite polymer composite(GPC)has become the main drawback limiting its application and popularization,Mo fibers were added into(GPC)to improve its mechanical strength.Mechanical properties of matrix materials with different mass ratio of resin and stabilizer(MRRS)were investigated systematically.The influences of MRRS on interface bonding strength of Mo fiber-matrix,wettability and mechanical strength of GPC were discussed,respectively,and the theoretical calculation result of MRRS k was obtained,with the optimal value of k=4.When k=4,tensile strength,tensile strain and fracture stress of the cured resin achieve the maximum values.But for k=7,the corresponding values reach the minimum.With the increase of MRRS k,surface free energy of the cured resin first increases and then decreases,while contact angles between Mo sample and matrix have displayed the opposite trend.Wettability of resin to Mo fiber is the best at k=4.Pulling load of Mo fiber and interface bonding strength appear the maximum at k=4,followed by k=5,k=3 the third,and k=7 the minimum.When k=4,mechanical properties of Mo fiber-reinforced GPC are optimal,which is consistent with the result of theoretical calculation.This study is of great significance to get better component formulas of Mo fiber reinforced GPC and to improve its application in machine tools.
基金supported by the National Natural Natural Science Foundation of China(No.52271055)the Natural Science Foundation of Hebei Province,China(No.E2024202154).
文摘FeCoCrNiMox composite powders were prepared using the mechanical alloying technique and made into high-entropy alloy(HEA)coatings with the face-centered cubic phase using plasma spraying to address the element segregation problem in HEAs and pre-pare uniform HEA coatings.Scanning electron microscopy,transmission electron microscopy,and X-ray diffractometry were employed to characterize these coatings’microstructure and phase composition.The hardness,elastic modulus,and fracture toughness of coatings were tested,and the corrosion resistance was analyzed in simulated seawater.Results show that the hardness of the coating is HV0.1606.15,the modulus of elasticity is 128.42 GPa,and the fracture toughness is 43.98 MPa·m^(1/2).The corrosion potential of the coating in 3.5wt%NaCl solution is-0.49 V,and the corrosion current density is 1.2×10^(−6)A/cm^(2).The electrochemical system comprises three parts:the electrolyte,the adsorption and metallic oxide films produced during immersion,and the FeCoNiCrMo HEA coating.Over in-creasingly long periods,the corrosion reaction rate increases first and then decreases,the corrosion product film comprising metal oxides reaches a dynamic balance between formation and dissolution,and the internal reaction of the coating declines.
文摘Automobiles are the inevitable mode of transportation.However,increasing fuel prices and carbon dioxide emissions are posing a serious threat to automobile users and the environment.Thus,the development of new lightweight materials has been a key area of research.Magnesium-based commercial alloys(AZ and ZK series alloys)are the lightest among all structural metals.However,there is still a question about the replacement of Aluminum-based alloys due to HCP crystal structure.In this connection,Mg-Al-Ca-Mn(AXM)Mg alloy can be a choice as an alternative to the existing Mg-based commercial alloys for structural applications.It contains(Al,Mg)_(2)Ca,Al_(2)Ca,Mg_(2)Ca,and Al_(8)Mn_(5)as the secondary phases,contributing to the microstructural refinement and property enhancement.However,the formation of those precipitates depends on the amount of Al,Ca,and Mn,especially,the Ca/Al ratio.In addition,the secondary processes influence the grain refinement and property enhancement of texture modifications.Hence,this review article focuses on elaborating on the significance of the Ca/Al ratio for the precipitate formation,secondary process,and texture modifications.The co-segregation behavior of other micro-alloying elements like Cerium,Lanthanum,and Zinc in AXM Mg alloy systems has also been discussed for property enhancement.
基金Science and Technology Project of Fire Rescue Bureau of Ministry of Emergency Management(Grant No.2022XFZD05)S&T Program of Hebei(Grant No.22375419D)National Natural Science Foundation of China(Grant No.11802160).
文摘As the basic protective element, steel plate had attracted world-wide attention because of frequent threats of explosive loads. This paper reports the relationships between microscopic defects of Q345 steel plate under the explosive load and its macroscopic dynamics simulation. Firstly, the defect characteristics of the steel plate were investigated by stereoscopic microscope(SM) and scanning electron microscope(SEM). At the macroscopic level, the defect was the formation of cave which was concentrated in the range of 0-3.0 cm from the explosion center, while at the microscopic level, the cavity and void formation were the typical damage characteristics. It also explains that the difference in defect morphology at different positions was the combining results of high temperature and high pressure. Secondly, the variation rules of mechanical properties of steel plate under explosive load were studied. The Arbitrary Lagrange-Euler(ALE) algorithm and multi-material fluid-structure coupling method were used to simulate the explosion process of steel plate. The accuracy of the method was verified by comparing the deformation of the simulation results with the experimental results, the pressure and stress at different positions on the surface of the steel plate were obtained. The simulation results indicated that the critical pressure causing the plate defects may be approximately 2.01 GPa. On this basis, it was found that the variation rules of surface pressure and microscopic defect area of the Q345 steel plate were strikingly similar, and the corresponding mathematical relationship between them was established. Compared with Monomolecular growth fitting models(MGFM) and Logistic fitting models(LFM), the relationship can be better expressed by cubic polynomial fitting model(CPFM). This paper illustrated that the explosive defect characteristics of metal plate at the microscopic level can be explored by analyzing its macroscopic dynamic mechanical response.
基金support from the National Natural Science Foundation of China(Nos.52005151,12172118,52205591,12227801,and 12072005)the Local Science and Technology Development Fund Projects Guided by the Central Government of China(No.236Z1810G)+4 种基金the Natural Science Foundation of Hebei Province(Nos.E2021202008 and E2021202100)the Fund for Innovative Research Groups of Natural Science Foundation of Hebei Province(No.A2020202002)the Key Program of Research and Development of Hebei Province(No.202030507040009)the Project of High-Level Talents Introduction of Hebei Province(No.2021HBQZYCSB009)the Key Project of National Natural Science Foundation of Tianjin(No.S20ZDF077).
文摘Two-dimensional(2D)materials are potential candidates for electronic devices due to their unique structures and exceptional physical properties,making them a focal point in nanotechnology research.Accurate assessment of the mechanical and tribological properties of 2D materials is imperative to fully exploit their potential across diverse applications.However,their nanoscale thickness and planar nature pose significant challenges in testing and characterizing their mechanical properties.Among the in situ characterization techniques,atomic force microscopy(AFM)has gained widespread applications in exploring the mechanical behaviour of nanomaterials,because of the easy measurement capability of nano force and displacement from the AFM tips.Specifically,AFM-based force spectroscopy is a common approach for studying the mechanical and tribological properties of 2D materials.This review comprehensively details the methods based on normal force spectroscopy,which are utilized to test and characterize the elastic and fracture properties,adhesion,and fatigue of 2D materials.Additionally,the methods using lateral force spectroscopy can characterize the interfacial properties of 2D materials,including surface friction of 2D materials,shear behaviour of interlayers as well as nanoflake-substrate interfaces.The influence of various factors,such as testing methods,external environments,and the properties of test samples,on the measured mechanical properties is also addressed.In the end,the current challenges and issues in AFM-based measurements of mechanical and tribological properties of 2D materials are discussed,which identifies the trend in the combination of multiple methods concerning the future development of the in situ testing techniques.
基金Funded by the Zhaoqing Xijiang Innovation and Entrepreneurship Team Project Funding of China(No.2017A0109004)。
文摘We employed a melt ultrasonic treatment near the liquidus to prepare a high-thermal-conductivity Al-4Si-2Ni-0.8Fe-0.4Mg alloy.The influences of various ultrasonic powers on its microstructure,mechanical properties,and thermal conductivity were investigated.It is shown that near-liquidus ultrasonication significantly refines the alloy grains and eutectic structure,synergistically improving the alloy’s mechanical properties and thermal conductivity.Specifically,the grain size decreased by 84.5%from 941.4 to 186.2μm.Increasing the ultrasonic power improved the thermal conductivity of the alloy slightly and significantly enhanced its mechanical properties.At an ultrasonic power of 2100 W,the tensile strength,yield strength,elongation rate,and thermal conductivity were 216 MPa,142 MPa,6.3%,and 169 W/(m·k),respectively.
基金Project supported by the National Natural Science Foundation of China(Nos.12393780,12032017,and 12002221)the Key Scientific Research Projects of China Railway Group(No.N2021J032)+2 种基金the College Education Scientific Research Project of Hebei Province of China(No.JZX2024006)the S&T Program of Hebei Province of China(No.21567622H)the National Scholarship Council of China。
文摘As an important component of the running gear of high-speed trains,axle box bearings can cause lubricating grease failure and damage to bearing components under continuous high-temperature operation,which will affect the normal operation of highspeed trains.Therefore,bearing temperature is one of the key parameters to be monitored in the online monitoring system for trains.Based on the thermal network method,this paper establishes a thermal network model for the axle box bearing,considering the radial thermal deformation of the double-row tapered roller bearing components caused by the oil film characteristics and the temperature variations of the lubricating grease.A thermo-mechanical coupling model for the grease-lubricated double-row tapered roller axle box bearing of high-speed trains with track irregularity excitation is established.The correctness of the model is verified using the test bench data,and the temperature of the bearing at different rotational speeds,loads,fault sizes,and ambient temperatures are investigated.
基金financially supported by the National Natural Science Foundation of China(Nos.12272356,12072326,and 12172337)the State Key Laboratory of Dynamic Measurement Technology,North University of China(No.2022-SYSJJ-03)。
文摘Al Si10Mg porous protective structure often produces different damage forms under compressive loading,and these damage modes affect its protective function.In order to well meet the service requirements,there is an urgent need to comprehensively understand the mechanical behavior and response mechanism of AlSi10Mg porous structures under compressive loading.In this paper,Al Si10Mg porous structures with three kinds of volume fractions are designed and optimized to meet the requirements of high-impact,strong-energy absorption,and lightweight characteristics.The mechanical behaviors of AlSi10Mg porous structures,including the stress-strain relationship,structural bearing state,deformation and damage modes,and energy absorption characteristics,were obtained through experimental studies at different loading rates.The damage pattern of the damage section indicates that AlSi10Mg porous structures have both ductile and brittle mechanical properties.Numerical simulation studies show that the AlSi10Mg porous structure undergoes shear damage due to relative misalignment along the diagonal cross-section,and the damage location is almost at 45°to the load direction,which is the most direct cause of its structural damage,revealing the damage mechanism of AlSi10Mg porous structures under the compressive load.The normalized energy absorption model constructed in the paper well interprets the energy absorption state of Al Si10Mg porous structures and gives the sensitive location of the structures,and the results of this paper provide important references for peers in structural design and optimization.
