The TiB+TiC dual-reinforced B_(4)C/TC4 composite was in-situ fabricated via incorporating 0.5wt%B_(4)C reinforcement during the laser melting deposition process.Different heat treatments of annealing and solid solutio...The TiB+TiC dual-reinforced B_(4)C/TC4 composite was in-situ fabricated via incorporating 0.5wt%B_(4)C reinforcement during the laser melting deposition process.Different heat treatments of annealing and solid solution were used to regulate the microstructure,mechanical properties,and corrosion properties of B_(4)C/TC4 composite.Results show that with the increase in temperature from 500℃to 800°C,partial lamellarα-Ti in the as-deposited sample is gradually transformed into equiaxedα-Ti,accompanied by the disappearance of basketweave microstructure.At 1100°C,a small portion of TiC phase suffers fusion.This composite exhibits the optimal combination of strength and plasticity after annealing at 500℃for 4 h followed by furnace cooling,which is attributed to the stress release effect and the refined basketweave microstructure.However,this composite shows a decline in corrosion resistance after various heat treatments due to grain coarsening and micro-galvanic corrosion.展开更多
Conductive hydrogel-based stretchable electronics have been extensively investigated,among which strain sensors are the most prominently studied.While the mechanical properties significantly affect the performance of ...Conductive hydrogel-based stretchable electronics have been extensively investigated,among which strain sensors are the most prominently studied.While the mechanical properties significantly affect the performance of these devices,the systematic correlation between specific mechanical parameters and sensing performance remains rarely explored.This work compares the influences of Young’s modulus and mechanical hysteresis on the sensing performance between highly entangled PAM-Li and double-network PAM-Li-Agar-3 strain sensors.Owing to the brittle agar network,which imparts a higher Young’s modulus and pronounced mechanical hysteresis to the double-network PAMLi-Agar-3 hydrogel,the corresponding sensor requires a greater driving force for deformation and yields signals with poor reproducibility.In comparison,the PAM-Li hydrogel,characterized by highly entangled polymer chains,exhibits a lower Young’s modulus and negligible mechanical hysteresis.Consequently,signals from the PAM-Li strain sensor demonstrate enhanced sensitivity and stability.Therefore,this work demonstrates that a low Young’s modulus and minimal mechanical hysteresis are critical factors for achieving superior sensing performance in strain sensors,as systematically validated through comparative analyses across diverse application scenarios.展开更多
Irregular bone scaffolds fabricated using the Voronoi tessellation method resemble the morphology and properties of human cancellous bones.This has become a prominent topic in bone tissue engineering research in recen...Irregular bone scaffolds fabricated using the Voronoi tessellation method resemble the morphology and properties of human cancellous bones.This has become a prominent topic in bone tissue engineering research in recent years.However,studies on the radial-gradient design of irregular bionic scaffolds are limited.Therefore,this study aims to develop a radial-gradient structure similar to that of natural long bones,enhancing the development of bionic bone scaffolds.A novel gradient method was adopted to maintain constant porosity,control the seed site-specific distribution within the irregular porous structure,and vary the strut diameter to generate radial gradients.The irregular scaffolds were compared with four conventional scaffolds(cube,pillar BCC,vintiles,and diamond)in terms of permeability,stress concentration characteristics,and mechanical properties.The results indicate that the radial-gradient irregular porous structure boasts the widest permeability range and superior stress distribution compared to conventional scaffolds.With an elastic modulus ranging from 4.20 GPa to 22.96 GPa and a yield strength between 68.37 MPa and 149.40 MPa,it meets bone implant performance requirements and demonstrates significant application potential.展开更多
Aero engines are key power components that provide thrust for the aircraft.The cerme turbine disc allows the new-generation domestic fighter aircraft to increase the overall thrust of the aero engine.Quantifying coati...Aero engines are key power components that provide thrust for the aircraft.The cerme turbine disc allows the new-generation domestic fighter aircraft to increase the overall thrust of the aero engine.Quantifying coatings and analyzing the stress on the teeth play critical roles in improving the turbine disc’s performance,which are two issues must be solved urgently.First,this work pro poses a quantitative analysis algorithm to conduct the Three-Dimensional(3D)distribution informa tion mining of the extracted coatings.Then,it proposes an Industrial Computed Laminography(ICL)reconstruction algorithm for non-destructively reconstructing the turbine disc’s high-quality3D morphological actual feature.Finally,a Finite Element Analysis(FEA)under the ultimate thrus is conducted on ICL reconstruction to verify the working status of the new-generation aero-engine turbine disc.The results show that the proposed quantitative analysis algorithm digitizes the aggre gated conditions of the coating with a statistically normalized Z_(1)value of–2.15 and a confidence leve higher than 95%.Three image-quality quantitative indicators:Peak Signal-to-Noise Ratio(PSNR)Structural Similarity Index Measure(SSIM),and Normalized Mean Square Distance(NMSD)of the proposed ICL reconstruction algorithm on turbine disc laminographic image are 26.45,0.88,and 0.73respectively,which are better than other algorithms.The mechanical analysis of ICL more realisti cally reflects the stress and deformation than that of 3D modeling.This work provides new ideas for the iterative research of new-generation aero-engine turbine discs.展开更多
The gear transmission system directly affects the operational performance of high-speed trains(HST).However,current research on gear transmission systems of HST often overlooks the effects of gear eccentricity and run...The gear transmission system directly affects the operational performance of high-speed trains(HST).However,current research on gear transmission systems of HST often overlooks the effects of gear eccentricity and running resistance,and the dynamic models of gear transmission system are not sufficiently comprehensive.This paper aims to establish an electromechanical coupling dynamic model of HST traction transmission system and study its electromechanical coupling vibration characteristics,in which the internal excitation factors such as gear eccentricity,time-varying meshing stiffness,backlash,meshing error,and external excitation factors such as electromagnetic torque and running resistance are stressed.The research results indicate that gear eccentricity and running resistance have a significant impact on the stability of the system,and gear eccentricity leads to intensified system vibration and decreased anti-interference ability.In addition,the characteristic frequency of gear eccentricity can be extracted from mechanical signals and current signals as a preliminary basis for eccentricity detection,and electrical signals can also be used to monitor changes in train running resistance in real time.The results of this study provide some useful insights into designing dynamic performance parameters for HST transmission systems and monitoring train operational states.展开更多
Mg alloy matrix composites reinforced with short carbon fibers(C_(sf)/Mg)are considered as potential candidates for integrated structural-functional electronic parts that satisfy the requirements of lightweight,excell...Mg alloy matrix composites reinforced with short carbon fibers(C_(sf)/Mg)are considered as potential candidates for integrated structural-functional electronic parts that satisfy the requirements of lightweight,excellent mechanical properties,and heat dissipation.However,the different characteristics of C_(sf)and Mg alloy make the interface a critical issue affecting the synergistic improvement of thermal and mechanical properties of the composites.Here,Cu coating with different thicknesses is introduced to modify the C_(sf)/Mg interface,so as to simultaneously enhance the thermal and mechanical performances,which can combine the advantages of coating modification and matrix alloying.Results reveal that thermal diffusivity(TD)of 3-C_(sf)-Cu/Mg composites is as high as 22.12 mm^(2)/s and an enhancement of 52.97%is achieved compared with C_(sf)/Mg composites,as well as 16.3%enhancement of ultimate compressive strength(UCS)in the longitudinal direction,8.84%improvement of UCS in the transverse direction,and 53.08%increasement of ultimate tensile strength(UTS).Such improvement can be ascribed to the formation of intermetallic compounds.The formation of intermetallic compounds can not only effectively alleviate the lattice distortion of the matrix and decrease interfacial thermal resistance,but also bear the loads.Our work is of great significance for designing C_(sf)/Mg composites with integrated structure and function.展开更多
Deep geological sequestration is widely recognized as a reliable method for nuclear waste management,with expanded applications in thermal energy storage and adiabatic compressed air energy storage systems.This study ...Deep geological sequestration is widely recognized as a reliable method for nuclear waste management,with expanded applications in thermal energy storage and adiabatic compressed air energy storage systems.This study evaluated the suitability of granite,basalt,and marble as reservoir rocks capable of withstanding extreme high-temperature and high-pressure conditions.Using a custom-designed triaxial testing apparatus for thermal-hydro-mechanical(THM)coupling,we subjected rock samples to temperatures ranging from 20℃to 800℃,triaxial stresses up to 25 MPa,and seepage pressures of 0.6 MPa.After THM treatment,the specimens were analyzed using a Real-Time Load-Synchronized Micro-Computed Tomography(MCT)Scanner under a triaxial stress of 25 MPa,allowing for high-resolution insights into pore and fissure responses.Our findings revealed distinct thermal stability profiles and microscopic parameter changes across three phasesdslow growth,slow decline,and rapid growthdwith critical temperature thresholds observed at 500℃for granite,600℃for basalt,and 300℃for marble.Basalt showed minimal porosity changes,increasing gradually from 3.83%at 20℃to 12.45%at 800℃,indicating high structural integrity and resilience under extreme THM conditions.Granite shows significant increases in porosity due to thermally induced microcracking,while marble rapidly deteriorated beyond 300℃due to carbonate decomposition.Consequently,basalt,with its minimal porosity variability,high thermal stability,and robust mechanical properties,emerges as an optimal candidate for nuclear waste repositories and other high-temperature geological engineering applications,offering enhanced reliability,structural stability,and long-term safety in such settings.展开更多
This study compares the microstructural evolution,dynamic recrystallization(DRX)behavior,tensile properties,and age-hardenability between the newly developed high-speed-extrudable BA56 alloy and those of the widely re...This study compares the microstructural evolution,dynamic recrystallization(DRX)behavior,tensile properties,and age-hardenability between the newly developed high-speed-extrudable BA56 alloy and those of the widely recognized AZ31 alloy in industry.Unlike the AZ31 alloy,which retains partially unrecrystallized grains,the high-speed-extruded BA56 alloy demonstrates a coarser but entirely recrystallized and more homogeneous microstructure.The fine-grained structure and abundant Mg_(3)Bi_(2) particles in the BA56 extrusion billet significantly enhance its DRX behavior,thus enabling rapid and complete recrystallization during extrusion.The BA56 alloy contains band-like fragmented Mg_(3)Bi_(2) particles and numerous fine Mg_(3)Bi_(2) particles distributed throughout the material,in contrast to the sparse Al_(8)Mn_(5) particles in the AZ31 alloy.These features contribute to superior mechanical properties of the BA56 alloy,which achieves tensile yield and ultimate tensile strengths of 205 and 292 MPa,respectively,compared to 196 and 270 MPa for the AZ31 alloy.The superior strength of the BA56 alloy,even with its coarser grain size,can be explained by its elevated Hall-Petch constant and the strengthening contribution from the fine Mg_(3)Bi_(2) particles.Additionally,the BA56 alloy demonstrates significant age-hardenability,achieving a 22%enhancement in hardness following T5 aging,attributed to the precipitation of nanoscale Mg_(3)Bi_(2) and Mg_(17)Al_(12) phases.By contrast,the AZ31 alloy shows minimal hardening due to the absence of precipitate formation during aging.These findings suggest that the BA56 alloy is a promising candidate for the production of extruded Mg components requiring a combination of high productivity,superior mechanical performance,and wide-ranging process adaptability.展开更多
In this review,we propose a comprehensive overview of additive manufacturing(AM)technologies and design possibilities in manufacturing metamaterials for various applications in the biomedical field,of which many are i...In this review,we propose a comprehensive overview of additive manufacturing(AM)technologies and design possibilities in manufacturing metamaterials for various applications in the biomedical field,of which many are inspired by nature itself.It describes how new AM technologies(e.g.continuous liquid interface production and multiphoton polymerization,etc)and recent developments in more mature AM technologies(e.g.powder bed fusion,stereolithography,and extrusion-based bioprinting(EBB),etc)lead to more precise,efficient,and personalized biomedical components.EBB is a revolutionary topic creating intricate models with remarkable mechanical compatibility of metamaterials,for instance,stress elimination for tissue engineering and regenerative medicine,negative or zero Poisson’s ratio.By exploiting the designs of porous structures(e.g.truss,triply periodic minimal surface,plant/animal-inspired,and functionally graded lattices,etc),AM-made bioactive bone implants,artificial tissues,and organs are made for tissue replacement.The material palette of the AM metamaterials has high diversity nowadays,ranging from alloys and metals(e.g.cobalt-chromium alloys and titanium,etc)to polymers(e.g.biodegradable polycaprolactone and polymethyl methacrylate,etc),which could be even integrated within bioactive ceramics.These advancements are driving the progress of the biomedical field,improving human health and quality of life.展开更多
High entropy alloys(HEAs),particularly CoCrNiFeMn system,have emerged as a transformative class of high-performance alloys due to their exceptional mechanical and functional properties.However,traditional manufacturin...High entropy alloys(HEAs),particularly CoCrNiFeMn system,have emerged as a transformative class of high-performance alloys due to their exceptional mechanical and functional properties.However,traditional manufacturing methods for HEAs are limited by inefficiencies and high costs,restricting their widespread applications.Additive manufacturing(AM),specifically laser powder bed fusion(LPBF),offers a promising alternative by enabling the fabrication of HEAs with unique microstructures and enhanced properties.This study investigates the thermal stability and mechanical performance of LPBF-printed CoCrNiFeMn HEA across a wide temperature range.The as-built LPBF HEA with a hierarchically heterogeneous microstructure,featured by columnar grains and ultrafine dislocation cellular structure,demonstrates exceptional thermal stability,with minimal hardness reduction and no apparent recrystallisation even after prolonged exposure to high temperatures(up to 1373 K),in stark contrast to the significant property degradation observed in conventionally processed HEAs.This stability is attributed to the unique dislocation cellular structures and the intrinsic thermal self-stabilizing effects induced by the LPBF process and the inhibition of recrystallisation due to the low stored energy and columnar grain morphology.The LPBF-fabricated HEA also exhibits outstanding strength-ductility synergy across a broad temperature spectrum,with cryogenic deformation enhancing both strength and ductility due to the activation of deformation twinning.At elevated temperatures,the alloy undergoes a slight reduction in strength but retains good ductility,except at 873 K,where a sharp decline in ductility is observed likely due to grain boundary decohesion and porosity-related crack initiation manifested by the cleavage fracture surface and the cracks at grain boundaries.These findings provide new insights into the temperature-dependent mechanical behavior of AM HEAs,highlight the critical role of dislocation cellular structures in achieving superior thermal and mechanical performance,and underscore the potential of additively manufactured HEAs with tailored microstructures for extreme environments.展开更多
Atomic surfaces are strictly required by high-performance devices of diamond.Nevertheless,diamond is the hardest material in nature,leading to the low material removal rate(MRR)and high surface roughness during machin...Atomic surfaces are strictly required by high-performance devices of diamond.Nevertheless,diamond is the hardest material in nature,leading to the low material removal rate(MRR)and high surface roughness during machining.Noxious slurries are widely used in conventional chemical mechanical polishing(CMP),resulting in the possible pollution to the environment.Moreover,the traditional slurries normally contain more than four ingredients,causing difficulties to control the process and quality of CMP.To solve these challenges,a novel green CMP for single crystal diamond was developed,consisting of only hydrogen peroxide,diamond abrasive and Prussian blue(PB)/titania catalyst.After CMP,atomic surface is achieved with surface roughness Sa of 0.079 nm,and the MRR is 1168 nm·h^(-1).Thickness of damaged layer is merely 0.66 nm confirmed by transmission electron microscopy(TEM).X-ray photoelectron spectroscopy,electron paramagnetic resonance and TEM reveal that·OH radicals form under ultraviolet irradiation on PB/titania catalyst.The·OH radicals oxidize diamond,transforming it from monocrystalline to amorphous atomic structure,generating a soft amorphous layer.This contributes the high MRR and formation of atomic surface on diamond.The developed novel green CMP offers new insights to achieve atomic surface of diamond for potential use in their high-performance devices.展开更多
Aseries of [(Fe_(0.6)Co_(0.2)Ni_(0.2))_(0.75-0.03x)B_(0.2)Si_(0.05+0.03x)]_(96)Nb_(4) amorphous alloy composite coatings were prepared by adjusting the silicon content(x=0,1,2,3,4,5,and 6)and their microstructures and...Aseries of [(Fe_(0.6)Co_(0.2)Ni_(0.2))_(0.75-0.03x)B_(0.2)Si_(0.05+0.03x)]_(96)Nb_(4) amorphous alloy composite coatings were prepared by adjusting the silicon content(x=0,1,2,3,4,5,and 6)and their microstructures and tribological properties were investigated by laser cladding technique.Additionally,the effect of Si on the glass forming ability(GFA)of the layers was understood.Results show that an appropriate Si content can refine the microstructure of the FeCoNiBSiNb laser cladding layers and improve the mechanical and tribological properties.The hardness of the coating layer increases monotonically with the Si content.At the Si content of 4.8at%(x=0),the coating layer exhibits a relatively low hardness(734.2HV 0.1).Conversely,at the silicon content of 13.44at%(x=3),the coating layer exhibits the highest hardness(1106HV 0.1).The non-crystalline content and tensile strength exhibit an initial increase,followed by a subsequent decrease.At x=2,the coating exhibits its maximum fracture strength(2880 MPa).However,when x>2,the fracture strength of the coating decreases with an increase in x.Conversely,with an increase in Si content,the wear volume loss initially decreases and then increases.At a Si content of 10.56at%(x=2),the coating exhibits the highest non-crystalline content(42%),the highest tensile strength(2880 MPa),and the most favorable dry friction performance.展开更多
Cage plus plate(CP)and zero-profile(Zero-P)devices are widely used in anterior cervical discectomy and fusion(ACDF).This study aimed to compare adjacent segment biomechanical changes after ACDF when using Zero-P devic...Cage plus plate(CP)and zero-profile(Zero-P)devices are widely used in anterior cervical discectomy and fusion(ACDF).This study aimed to compare adjacent segment biomechanical changes after ACDF when using Zero-P device and CP in different segments.First,complete C1—C7 cervical segments were constructed and validated.Meanwhile,four surgery models were developed by implanting the Zero-P device or CP into C4—C5 or C5—C6 segments based on the intact model.The segmental range of motion(ROM)and maximum value of the intradiscal pressure of the surgery models were compared with those of the intact model.The implantation of CP and Zero-P devices in C4—C5 segments decreased ROM by about 91.6%and 84.3%,respectively,and increased adjacent segment ROM by about 8.3%and 6.82%,respectively.The implantation of CP and Zero-P devices in C5—C6 segments decreased ROM by about 93.3%and 89.9%,respectively,while increasing adjacent segment ROM by about 4.9%and 4%,respectively.Furthermore,the implantation of CP and Zero-P devices increased the intradiscal pressure in the adjacent segments of C4—C5 segments by about 4.5%and 6.7%,respectively.The implantation of CP and Zero-P devices significantly increased the intradiscal pressure in the adjacent segments of C5—C6 by about 54.1%and 15.4%,respectively.In conclusion,CP and Zero-P fusion systems can significantly reduce the ROM of the fusion implant segment in ACDF while increasing the ROM and intradiscal pressure of adjacent segments.Results showed that Zero-P fusion system is the best choice for C5—C6 segmental ACDF.However,further studies are needed to select the most suitable cervical fusion system for C4—C5 segmental ACDF.Therefore,this study provides biomechanical recommendations for clinical surgery.展开更多
A human semicircular canal(HSC)with“cupulolithiasis”(HSCC)causes abnormal perception and vertigo.Based on 3D printing technology and target tracking technology,models of a visualized bionic semicircular canal with c...A human semicircular canal(HSC)with“cupulolithiasis”(HSCC)causes abnormal perception and vertigo.Based on 3D printing technology and target tracking technology,models of a visualized bionic semicircular canal with cupulolithiasis(BSCC)were generated.The model,with careful scaling parameters,similar biomechanical responses to the vestibular-ocular reflex(VOR),and a similarly long time constant to the HSC,allows us to study the mechanics of the HSCC.The static experiments revealed that the bionic cupula of the BSCC continued to shift due to the effect of the gravity of the otolith after rotation stopped.The frequency broadband experiment indicated that the gain of the BSCC decreased as the phase difference increased,and the increase in otolith mass aggravated this trend.BSCCs can be used as a bionic model to study the pathology of human semicircular canal-related diseases and may promote the development of treatments.展开更多
Aluminum alloys manufactured using traditional processes are increasingly unable to meet the high flexibility and performance requirements of modern engineering.In this study,Al-Mg-Sc-Zr alloys were manufactured via l...Aluminum alloys manufactured using traditional processes are increasingly unable to meet the high flexibility and performance requirements of modern engineering.In this study,Al-Mg-Sc-Zr alloys were manufactured via laser powder bed fusion(LPBF)to obtain high-performance aluminum alloys.To this end,process parameter optimization and heat treatment were adopted.The optimal process parameters were determined by initially analyzing the relative density and defect distribution under varying energy densities.The sample obtained under the optimal process parameters exhibited a relative density of 99.84%.Subsequently,the corresponding phase compositions,microstructures,and mechanical performance of the as-fabricated specimens were determined using the optimal process parameters before and after heat treatment.The microstructures of the samples showed typical equiaxed columnar bimodal grain structures,with Al_(3)(Sc,Zr)precipitates detected.The samples exhibited no significant anisotropy before and after heat treatment,while the grain orientation differences were dominated by high-angle grain boundaries.The mechanical properties of all the samples were characterized using tensile and hardness tests.The yield strength,ultimate tensile strength,and elongation of the sample were 475.0 MPa,508.2 MPa,and 8.3%,respectively.Overall,samples with high density,low porosity,high strength,and high plasticity were obtained by process parameter optimization and appropriate heat treatment.展开更多
The effects of various hot deformation states on the evolution of microstructures and mechanical properties in diffusion bonded TC4 alloys were investigated using the hot bending of thick plates.Finite element simulat...The effects of various hot deformation states on the evolution of microstructures and mechanical properties in diffusion bonded TC4 alloys were investigated using the hot bending of thick plates.Finite element simulations were conducted to characterize the deformation states during bending at 750℃ with angles of 17°and 32°.The microstructures and mechanical properties of the bonding interface were then analyzed.The joint subjected to uniaxial stress exhibited the highest ultimate tensile strength,which was attributed to the significant accumulation of dislocation density and the low-angle grain boundaries within the grains.The texture strengthening in the basal{0001}plane was also observed,along with a relatively low Schmid factor corresponding to the primary slip systems aligned with the deformation direction.In contrast,the joint under stress-free conditions showed a slip direction that was less favorable for deformation,resulting in an ultimate tensile strength higher than that of the joint under biaxial stress conditions.展开更多
With the development and popularization of computer application technology,the use of computer graphics and image processing technology has become the main means of modern engineering design and drawing.Learning and m...With the development and popularization of computer application technology,the use of computer graphics and image processing technology has become the main means of modern engineering design and drawing.Learning and mastering 3D modeling technology and mechanical information modeling technology have become an important goal of learning engineering drawing.To meet the teaching requirements of the“New Engineering”program,higher education should cultivate innovative talents with the ability to identify,express,analyze,and solve complex engineering problems;promote the transformation of teaching methods for the course of“Mechanical Drawing and Computer Drawing”from“teaching well”to“learning well.”This change is not only a change in course content,but also a change in training objectives.It introduces modern 3D design concepts into the drawing course,constructs a learning system with 3D modeling technology as the main line,solves the problem of imagination in traditional teaching,makes the learning process more in line with scientific cognitive laws,better meets the needs of modern manufacturing industry for new technologies,and improves students’drawing skills and ability to use modern tools(computer drawing).展开更多
In this work,the effect of ultrasonic vibration modes on the mechanical properties and relaxation of residual stress in 6061-T6 aluminum alloy was studied.A new ultrasonic vibration Johnson-Cook model was proposed,and...In this work,the effect of ultrasonic vibration modes on the mechanical properties and relaxation of residual stress in 6061-T6 aluminum alloy was studied.A new ultrasonic vibration Johnson-Cook model was proposed,and the relaxation and distribution of residual stress under ultrasonic vibration were predicted and analyzed using the finite element method(FEM).The mechanical properties of 6061-T6 aluminum alloy under different ultrasonic vibration modes were analyzed through experiments involving notched specimen tensile testing and scanning electron microscopy(SEM)analysis.The findings indicate that ultrasonic vibration treatment during deformation,unloading,and load-holding,as well as treatment with its natural ultrasonic frequency,can effectively release residual stress;however,treatment with its natural frequency has the highest rate of release up to 65.4%.Ultrasonic vibration treatment during deformation better inhibits fracture under the same conditions.The FEM results are in good agreement with the experimental results,and it can be used as a valid tool for predicting residual stress release under ultrasonic vibration.展开更多
Mg-RE alloys demonstrate exceptional comprehensive performance,finding widespread applications in biodegradable implants,aerospace,automotive,and other industries.This study investigated Mg-xHo binary alloys(x=1 wt%,3...Mg-RE alloys demonstrate exceptional comprehensive performance,finding widespread applications in biodegradable implants,aerospace,automotive,and other industries.This study investigated Mg-xHo binary alloys(x=1 wt%,3 wt%,5 wt%,7 wt%,9 wt%)synthesized via vacuum arc melting with copper mold cooling.Mechanical properties were evaluated through compression test,revealing that Ho addition significantly enhances the mechanical properties of Mg via solid solution strengthening,grain refinement,and second phase strengthening.The Mg-7Ho alloy exhibits optimal mechanical performa nce,with a co mpressive yield strength(CYS)of 101.2 MPa and ultimate compressive stre ngth(UCS)of274.0 MPa.However,excessive Ho addition leads to grain boundary aggregation,diminishing grain boundary cohesion and increasing susceptibility to intergranular fracture.Corrosion behavior was assessed using electrochemical tests and immersion experiments.A comprehensive analysis of corrosion rates reveals a wide spectrum of responses across different Ho concentrations.Notably,the Mg-1 Ho alloy exhibits the most pronounced corrosion susceptibility,as evidenced by its elevated corrosion current density of 0.043 mA/cm^(2).Conversely,the Mg-5Ho alloy demonstrates superior corrosion resistance,manifesting the lowest corrosion curre nt density of 0.088 mA/cm^(2)among the studied compositions.This phenomenon is attributed to Ho's solid solution in the α-Mg matrix,which elevates matrix potential,and the formation of a corrosion-resistant Ho-containing oxide layer.Additionally,the quantity and distribution of second phases influence corrosion resistance.A higher number of evenly distributed second phases act as a barrier to matrix corrosion rather than as cathodic sites acceleratingα-Mg matrix corrosion.展开更多
TIG surface remelting was performed to strengthen the surface of ZL109G alloy piston.The macrostructure indicates that surface remelting leads to the production of a remelted zone(RZ).The diameter of the primary Si de...TIG surface remelting was performed to strengthen the surface of ZL109G alloy piston.The macrostructure indicates that surface remelting leads to the production of a remelted zone(RZ).The diameter of the primary Si decreases from 65.8μm in the base metal(BM)to 7.1μm in RZ.The grain size of the RZ is refined to be approximately one-seventh that of the BM.The cellular microstructure in the RZ is characterised by theα(Al)in the centre and intermetallics preferentially located at the cellular boundaries.The results of the mechanical properties demonstrate that the average hardness value of RZ increases by 39%compared to that of BM.For the transverse samples,the ultimate tensile strength increases by~24.5%,which can be attributed to the solution strengthening of Si inα(Al).The average fracture toughness values are 15.0 and 12.7 MPa·m^(1/2)forα(Al)in BM and RZ,respectively.展开更多
基金Tianjin Municipal Natural Science Foundation(23JCYBJC00040)National Natural Science Foundation of China(52175369)。
文摘The TiB+TiC dual-reinforced B_(4)C/TC4 composite was in-situ fabricated via incorporating 0.5wt%B_(4)C reinforcement during the laser melting deposition process.Different heat treatments of annealing and solid solution were used to regulate the microstructure,mechanical properties,and corrosion properties of B_(4)C/TC4 composite.Results show that with the increase in temperature from 500℃to 800°C,partial lamellarα-Ti in the as-deposited sample is gradually transformed into equiaxedα-Ti,accompanied by the disappearance of basketweave microstructure.At 1100°C,a small portion of TiC phase suffers fusion.This composite exhibits the optimal combination of strength and plasticity after annealing at 500℃for 4 h followed by furnace cooling,which is attributed to the stress release effect and the refined basketweave microstructure.However,this composite shows a decline in corrosion resistance after various heat treatments due to grain coarsening and micro-galvanic corrosion.
基金supported by the National Natural Science Foundation of China(52303145,52403083)the Natural Science Foundation of Sichuan Province(2025ZNSFSC1400)supported by the start-up funding at Chengdu University(T202207)。
文摘Conductive hydrogel-based stretchable electronics have been extensively investigated,among which strain sensors are the most prominently studied.While the mechanical properties significantly affect the performance of these devices,the systematic correlation between specific mechanical parameters and sensing performance remains rarely explored.This work compares the influences of Young’s modulus and mechanical hysteresis on the sensing performance between highly entangled PAM-Li and double-network PAM-Li-Agar-3 strain sensors.Owing to the brittle agar network,which imparts a higher Young’s modulus and pronounced mechanical hysteresis to the double-network PAMLi-Agar-3 hydrogel,the corresponding sensor requires a greater driving force for deformation and yields signals with poor reproducibility.In comparison,the PAM-Li hydrogel,characterized by highly entangled polymer chains,exhibits a lower Young’s modulus and negligible mechanical hysteresis.Consequently,signals from the PAM-Li strain sensor demonstrate enhanced sensitivity and stability.Therefore,this work demonstrates that a low Young’s modulus and minimal mechanical hysteresis are critical factors for achieving superior sensing performance in strain sensors,as systematically validated through comparative analyses across diverse application scenarios.
基金the National Natural Science Foundation of China(No.52165026)。
文摘Irregular bone scaffolds fabricated using the Voronoi tessellation method resemble the morphology and properties of human cancellous bones.This has become a prominent topic in bone tissue engineering research in recent years.However,studies on the radial-gradient design of irregular bionic scaffolds are limited.Therefore,this study aims to develop a radial-gradient structure similar to that of natural long bones,enhancing the development of bionic bone scaffolds.A novel gradient method was adopted to maintain constant porosity,control the seed site-specific distribution within the irregular porous structure,and vary the strut diameter to generate radial gradients.The irregular scaffolds were compared with four conventional scaffolds(cube,pillar BCC,vintiles,and diamond)in terms of permeability,stress concentration characteristics,and mechanical properties.The results indicate that the radial-gradient irregular porous structure boasts the widest permeability range and superior stress distribution compared to conventional scaffolds.With an elastic modulus ranging from 4.20 GPa to 22.96 GPa and a yield strength between 68.37 MPa and 149.40 MPa,it meets bone implant performance requirements and demonstrates significant application potential.
基金supported by the National Natural Science Foundation of China(No.51975026)。
文摘Aero engines are key power components that provide thrust for the aircraft.The cerme turbine disc allows the new-generation domestic fighter aircraft to increase the overall thrust of the aero engine.Quantifying coatings and analyzing the stress on the teeth play critical roles in improving the turbine disc’s performance,which are two issues must be solved urgently.First,this work pro poses a quantitative analysis algorithm to conduct the Three-Dimensional(3D)distribution informa tion mining of the extracted coatings.Then,it proposes an Industrial Computed Laminography(ICL)reconstruction algorithm for non-destructively reconstructing the turbine disc’s high-quality3D morphological actual feature.Finally,a Finite Element Analysis(FEA)under the ultimate thrus is conducted on ICL reconstruction to verify the working status of the new-generation aero-engine turbine disc.The results show that the proposed quantitative analysis algorithm digitizes the aggre gated conditions of the coating with a statistically normalized Z_(1)value of–2.15 and a confidence leve higher than 95%.Three image-quality quantitative indicators:Peak Signal-to-Noise Ratio(PSNR)Structural Similarity Index Measure(SSIM),and Normalized Mean Square Distance(NMSD)of the proposed ICL reconstruction algorithm on turbine disc laminographic image are 26.45,0.88,and 0.73respectively,which are better than other algorithms.The mechanical analysis of ICL more realisti cally reflects the stress and deformation than that of 3D modeling.This work provides new ideas for the iterative research of new-generation aero-engine turbine discs.
基金supported by Sichuan Science and Technology Program(Grant No.2020YFH0080)the National Natural Science Foundation of China(Grant No.51475386)the National Basic Research Project of China(973 Program,Grant No.2015CB654801).
文摘The gear transmission system directly affects the operational performance of high-speed trains(HST).However,current research on gear transmission systems of HST often overlooks the effects of gear eccentricity and running resistance,and the dynamic models of gear transmission system are not sufficiently comprehensive.This paper aims to establish an electromechanical coupling dynamic model of HST traction transmission system and study its electromechanical coupling vibration characteristics,in which the internal excitation factors such as gear eccentricity,time-varying meshing stiffness,backlash,meshing error,and external excitation factors such as electromagnetic torque and running resistance are stressed.The research results indicate that gear eccentricity and running resistance have a significant impact on the stability of the system,and gear eccentricity leads to intensified system vibration and decreased anti-interference ability.In addition,the characteristic frequency of gear eccentricity can be extracted from mechanical signals and current signals as a preliminary basis for eccentricity detection,and electrical signals can also be used to monitor changes in train running resistance in real time.The results of this study provide some useful insights into designing dynamic performance parameters for HST transmission systems and monitoring train operational states.
基金supported by the National Natural Science Foundation of China(grant no.52231004 and 52072305).
文摘Mg alloy matrix composites reinforced with short carbon fibers(C_(sf)/Mg)are considered as potential candidates for integrated structural-functional electronic parts that satisfy the requirements of lightweight,excellent mechanical properties,and heat dissipation.However,the different characteristics of C_(sf)and Mg alloy make the interface a critical issue affecting the synergistic improvement of thermal and mechanical properties of the composites.Here,Cu coating with different thicknesses is introduced to modify the C_(sf)/Mg interface,so as to simultaneously enhance the thermal and mechanical performances,which can combine the advantages of coating modification and matrix alloying.Results reveal that thermal diffusivity(TD)of 3-C_(sf)-Cu/Mg composites is as high as 22.12 mm^(2)/s and an enhancement of 52.97%is achieved compared with C_(sf)/Mg composites,as well as 16.3%enhancement of ultimate compressive strength(UCS)in the longitudinal direction,8.84%improvement of UCS in the transverse direction,and 53.08%increasement of ultimate tensile strength(UTS).Such improvement can be ascribed to the formation of intermetallic compounds.The formation of intermetallic compounds can not only effectively alleviate the lattice distortion of the matrix and decrease interfacial thermal resistance,but also bear the loads.Our work is of great significance for designing C_(sf)/Mg composites with integrated structure and function.
基金financial supported by Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines(Grant No.DM2022B03)Youth Program of National Natural Science Foundation of China(Grant No.51904195)Scientific and Technological Innovation Programs of Higher Educations Institutions in Shanxi Province(Grant No.2022L608).
文摘Deep geological sequestration is widely recognized as a reliable method for nuclear waste management,with expanded applications in thermal energy storage and adiabatic compressed air energy storage systems.This study evaluated the suitability of granite,basalt,and marble as reservoir rocks capable of withstanding extreme high-temperature and high-pressure conditions.Using a custom-designed triaxial testing apparatus for thermal-hydro-mechanical(THM)coupling,we subjected rock samples to temperatures ranging from 20℃to 800℃,triaxial stresses up to 25 MPa,and seepage pressures of 0.6 MPa.After THM treatment,the specimens were analyzed using a Real-Time Load-Synchronized Micro-Computed Tomography(MCT)Scanner under a triaxial stress of 25 MPa,allowing for high-resolution insights into pore and fissure responses.Our findings revealed distinct thermal stability profiles and microscopic parameter changes across three phasesdslow growth,slow decline,and rapid growthdwith critical temperature thresholds observed at 500℃for granite,600℃for basalt,and 300℃for marble.Basalt showed minimal porosity changes,increasing gradually from 3.83%at 20℃to 12.45%at 800℃,indicating high structural integrity and resilience under extreme THM conditions.Granite shows significant increases in porosity due to thermally induced microcracking,while marble rapidly deteriorated beyond 300℃due to carbonate decomposition.Consequently,basalt,with its minimal porosity variability,high thermal stability,and robust mechanical properties,emerges as an optimal candidate for nuclear waste repositories and other high-temperature geological engineering applications,offering enhanced reliability,structural stability,and long-term safety in such settings.
基金supported by the National Research Foundation of Korea(NRF)grants funded by the Korea government(MSIT)(Nos.RS-2024–00351052 and RS-2024–00450561).
文摘This study compares the microstructural evolution,dynamic recrystallization(DRX)behavior,tensile properties,and age-hardenability between the newly developed high-speed-extrudable BA56 alloy and those of the widely recognized AZ31 alloy in industry.Unlike the AZ31 alloy,which retains partially unrecrystallized grains,the high-speed-extruded BA56 alloy demonstrates a coarser but entirely recrystallized and more homogeneous microstructure.The fine-grained structure and abundant Mg_(3)Bi_(2) particles in the BA56 extrusion billet significantly enhance its DRX behavior,thus enabling rapid and complete recrystallization during extrusion.The BA56 alloy contains band-like fragmented Mg_(3)Bi_(2) particles and numerous fine Mg_(3)Bi_(2) particles distributed throughout the material,in contrast to the sparse Al_(8)Mn_(5) particles in the AZ31 alloy.These features contribute to superior mechanical properties of the BA56 alloy,which achieves tensile yield and ultimate tensile strengths of 205 and 292 MPa,respectively,compared to 196 and 270 MPa for the AZ31 alloy.The superior strength of the BA56 alloy,even with its coarser grain size,can be explained by its elevated Hall-Petch constant and the strengthening contribution from the fine Mg_(3)Bi_(2) particles.Additionally,the BA56 alloy demonstrates significant age-hardenability,achieving a 22%enhancement in hardness following T5 aging,attributed to the precipitation of nanoscale Mg_(3)Bi_(2) and Mg_(17)Al_(12) phases.By contrast,the AZ31 alloy shows minimal hardening due to the absence of precipitate formation during aging.These findings suggest that the BA56 alloy is a promising candidate for the production of extruded Mg components requiring a combination of high productivity,superior mechanical performance,and wide-ranging process adaptability.
基金sponsored by the Science and Technology Program of Hubei Province,China(2022EHB020,2023BBB096)support provided by Centre of the Excellence in Production Research(XPRES)at KTH。
文摘In this review,we propose a comprehensive overview of additive manufacturing(AM)technologies and design possibilities in manufacturing metamaterials for various applications in the biomedical field,of which many are inspired by nature itself.It describes how new AM technologies(e.g.continuous liquid interface production and multiphoton polymerization,etc)and recent developments in more mature AM technologies(e.g.powder bed fusion,stereolithography,and extrusion-based bioprinting(EBB),etc)lead to more precise,efficient,and personalized biomedical components.EBB is a revolutionary topic creating intricate models with remarkable mechanical compatibility of metamaterials,for instance,stress elimination for tissue engineering and regenerative medicine,negative or zero Poisson’s ratio.By exploiting the designs of porous structures(e.g.truss,triply periodic minimal surface,plant/animal-inspired,and functionally graded lattices,etc),AM-made bioactive bone implants,artificial tissues,and organs are made for tissue replacement.The material palette of the AM metamaterials has high diversity nowadays,ranging from alloys and metals(e.g.cobalt-chromium alloys and titanium,etc)to polymers(e.g.biodegradable polycaprolactone and polymethyl methacrylate,etc),which could be even integrated within bioactive ceramics.These advancements are driving the progress of the biomedical field,improving human health and quality of life.
基金support from the Australian Centre for Microscopy and Microanalysis(ACMM)as well as the Microscopy Australian node at the University of Sydneysupport from the Australian Research Council under DP23010228,from The University of Sydney under the Robinson Fellowship Scheme and from The University of Sydney Nano Institute under the Kickstarter Funding and Student Ambassador Scholarshipsupport from the National Natural Science Foundation of China(Grant number 52274381).
文摘High entropy alloys(HEAs),particularly CoCrNiFeMn system,have emerged as a transformative class of high-performance alloys due to their exceptional mechanical and functional properties.However,traditional manufacturing methods for HEAs are limited by inefficiencies and high costs,restricting their widespread applications.Additive manufacturing(AM),specifically laser powder bed fusion(LPBF),offers a promising alternative by enabling the fabrication of HEAs with unique microstructures and enhanced properties.This study investigates the thermal stability and mechanical performance of LPBF-printed CoCrNiFeMn HEA across a wide temperature range.The as-built LPBF HEA with a hierarchically heterogeneous microstructure,featured by columnar grains and ultrafine dislocation cellular structure,demonstrates exceptional thermal stability,with minimal hardness reduction and no apparent recrystallisation even after prolonged exposure to high temperatures(up to 1373 K),in stark contrast to the significant property degradation observed in conventionally processed HEAs.This stability is attributed to the unique dislocation cellular structures and the intrinsic thermal self-stabilizing effects induced by the LPBF process and the inhibition of recrystallisation due to the low stored energy and columnar grain morphology.The LPBF-fabricated HEA also exhibits outstanding strength-ductility synergy across a broad temperature spectrum,with cryogenic deformation enhancing both strength and ductility due to the activation of deformation twinning.At elevated temperatures,the alloy undergoes a slight reduction in strength but retains good ductility,except at 873 K,where a sharp decline in ductility is observed likely due to grain boundary decohesion and porosity-related crack initiation manifested by the cleavage fracture surface and the cracks at grain boundaries.These findings provide new insights into the temperature-dependent mechanical behavior of AM HEAs,highlight the critical role of dislocation cellular structures in achieving superior thermal and mechanical performance,and underscore the potential of additively manufactured HEAs with tailored microstructures for extreme environments.
基金financial support from the National Key Research and Development Program of China(2018YFA0703400)the Fundamental Research Funds for the Provincial Universities of Zhejiang(GK239909299001021)+1 种基金the Ninth China Association for Science and Technology Youth Talent Lift Project Support Plan(KYZ015324002)the Changjiang Scholars Program of Chinese Ministry of Education。
文摘Atomic surfaces are strictly required by high-performance devices of diamond.Nevertheless,diamond is the hardest material in nature,leading to the low material removal rate(MRR)and high surface roughness during machining.Noxious slurries are widely used in conventional chemical mechanical polishing(CMP),resulting in the possible pollution to the environment.Moreover,the traditional slurries normally contain more than four ingredients,causing difficulties to control the process and quality of CMP.To solve these challenges,a novel green CMP for single crystal diamond was developed,consisting of only hydrogen peroxide,diamond abrasive and Prussian blue(PB)/titania catalyst.After CMP,atomic surface is achieved with surface roughness Sa of 0.079 nm,and the MRR is 1168 nm·h^(-1).Thickness of damaged layer is merely 0.66 nm confirmed by transmission electron microscopy(TEM).X-ray photoelectron spectroscopy,electron paramagnetic resonance and TEM reveal that·OH radicals form under ultraviolet irradiation on PB/titania catalyst.The·OH radicals oxidize diamond,transforming it from monocrystalline to amorphous atomic structure,generating a soft amorphous layer.This contributes the high MRR and formation of atomic surface on diamond.The developed novel green CMP offers new insights to achieve atomic surface of diamond for potential use in their high-performance devices.
文摘Aseries of [(Fe_(0.6)Co_(0.2)Ni_(0.2))_(0.75-0.03x)B_(0.2)Si_(0.05+0.03x)]_(96)Nb_(4) amorphous alloy composite coatings were prepared by adjusting the silicon content(x=0,1,2,3,4,5,and 6)and their microstructures and tribological properties were investigated by laser cladding technique.Additionally,the effect of Si on the glass forming ability(GFA)of the layers was understood.Results show that an appropriate Si content can refine the microstructure of the FeCoNiBSiNb laser cladding layers and improve the mechanical and tribological properties.The hardness of the coating layer increases monotonically with the Si content.At the Si content of 4.8at%(x=0),the coating layer exhibits a relatively low hardness(734.2HV 0.1).Conversely,at the silicon content of 13.44at%(x=3),the coating layer exhibits the highest hardness(1106HV 0.1).The non-crystalline content and tensile strength exhibit an initial increase,followed by a subsequent decrease.At x=2,the coating exhibits its maximum fracture strength(2880 MPa).However,when x>2,the fracture strength of the coating decreases with an increase in x.Conversely,with an increase in Si content,the wear volume loss initially decreases and then increases.At a Si content of 10.56at%(x=2),the coating exhibits the highest non-crystalline content(42%),the highest tensile strength(2880 MPa),and the most favorable dry friction performance.
基金the National Natural Science Foundation of China(Nos.32260235 and 82260446)。
文摘Cage plus plate(CP)and zero-profile(Zero-P)devices are widely used in anterior cervical discectomy and fusion(ACDF).This study aimed to compare adjacent segment biomechanical changes after ACDF when using Zero-P device and CP in different segments.First,complete C1—C7 cervical segments were constructed and validated.Meanwhile,four surgery models were developed by implanting the Zero-P device or CP into C4—C5 or C5—C6 segments based on the intact model.The segmental range of motion(ROM)and maximum value of the intradiscal pressure of the surgery models were compared with those of the intact model.The implantation of CP and Zero-P devices in C4—C5 segments decreased ROM by about 91.6%and 84.3%,respectively,and increased adjacent segment ROM by about 8.3%and 6.82%,respectively.The implantation of CP and Zero-P devices in C5—C6 segments decreased ROM by about 93.3%and 89.9%,respectively,while increasing adjacent segment ROM by about 4.9%and 4%,respectively.Furthermore,the implantation of CP and Zero-P devices increased the intradiscal pressure in the adjacent segments of C4—C5 segments by about 4.5%and 6.7%,respectively.The implantation of CP and Zero-P devices significantly increased the intradiscal pressure in the adjacent segments of C5—C6 by about 54.1%and 15.4%,respectively.In conclusion,CP and Zero-P fusion systems can significantly reduce the ROM of the fusion implant segment in ACDF while increasing the ROM and intradiscal pressure of adjacent segments.Results showed that Zero-P fusion system is the best choice for C5—C6 segmental ACDF.However,further studies are needed to select the most suitable cervical fusion system for C4—C5 segmental ACDF.Therefore,this study provides biomechanical recommendations for clinical surgery.
基金supported by the National Key Research and Development Program of China(No.2024YFD2000203)the National Natural Science Foundation of China(No.51775483).
文摘A human semicircular canal(HSC)with“cupulolithiasis”(HSCC)causes abnormal perception and vertigo.Based on 3D printing technology and target tracking technology,models of a visualized bionic semicircular canal with cupulolithiasis(BSCC)were generated.The model,with careful scaling parameters,similar biomechanical responses to the vestibular-ocular reflex(VOR),and a similarly long time constant to the HSC,allows us to study the mechanics of the HSCC.The static experiments revealed that the bionic cupula of the BSCC continued to shift due to the effect of the gravity of the otolith after rotation stopped.The frequency broadband experiment indicated that the gain of the BSCC decreased as the phase difference increased,and the increase in otolith mass aggravated this trend.BSCCs can be used as a bionic model to study the pathology of human semicircular canal-related diseases and may promote the development of treatments.
基金supported by National Natural Science Foundation of China(Grant Nos.5233500651975073)State Key Laboratory of Mechanical Transmission for Advanced Equipment(Grant No.SKLMT-MSKFKT-202104).
文摘Aluminum alloys manufactured using traditional processes are increasingly unable to meet the high flexibility and performance requirements of modern engineering.In this study,Al-Mg-Sc-Zr alloys were manufactured via laser powder bed fusion(LPBF)to obtain high-performance aluminum alloys.To this end,process parameter optimization and heat treatment were adopted.The optimal process parameters were determined by initially analyzing the relative density and defect distribution under varying energy densities.The sample obtained under the optimal process parameters exhibited a relative density of 99.84%.Subsequently,the corresponding phase compositions,microstructures,and mechanical performance of the as-fabricated specimens were determined using the optimal process parameters before and after heat treatment.The microstructures of the samples showed typical equiaxed columnar bimodal grain structures,with Al_(3)(Sc,Zr)precipitates detected.The samples exhibited no significant anisotropy before and after heat treatment,while the grain orientation differences were dominated by high-angle grain boundaries.The mechanical properties of all the samples were characterized using tensile and hardness tests.The yield strength,ultimate tensile strength,and elongation of the sample were 475.0 MPa,508.2 MPa,and 8.3%,respectively.Overall,samples with high density,low porosity,high strength,and high plasticity were obtained by process parameter optimization and appropriate heat treatment.
基金the financial support from Fundamental Research Funds for the Central Universities,China(No.YWF-23-L-1012)the National Natural Science Foundation of China(No.52005020).
文摘The effects of various hot deformation states on the evolution of microstructures and mechanical properties in diffusion bonded TC4 alloys were investigated using the hot bending of thick plates.Finite element simulations were conducted to characterize the deformation states during bending at 750℃ with angles of 17°and 32°.The microstructures and mechanical properties of the bonding interface were then analyzed.The joint subjected to uniaxial stress exhibited the highest ultimate tensile strength,which was attributed to the significant accumulation of dislocation density and the low-angle grain boundaries within the grains.The texture strengthening in the basal{0001}plane was also observed,along with a relatively low Schmid factor corresponding to the primary slip systems aligned with the deformation direction.In contrast,the joint under stress-free conditions showed a slip direction that was less favorable for deformation,resulting in an ultimate tensile strength higher than that of the joint under biaxial stress conditions.
文摘With the development and popularization of computer application technology,the use of computer graphics and image processing technology has become the main means of modern engineering design and drawing.Learning and mastering 3D modeling technology and mechanical information modeling technology have become an important goal of learning engineering drawing.To meet the teaching requirements of the“New Engineering”program,higher education should cultivate innovative talents with the ability to identify,express,analyze,and solve complex engineering problems;promote the transformation of teaching methods for the course of“Mechanical Drawing and Computer Drawing”from“teaching well”to“learning well.”This change is not only a change in course content,but also a change in training objectives.It introduces modern 3D design concepts into the drawing course,constructs a learning system with 3D modeling technology as the main line,solves the problem of imagination in traditional teaching,makes the learning process more in line with scientific cognitive laws,better meets the needs of modern manufacturing industry for new technologies,and improves students’drawing skills and ability to use modern tools(computer drawing).
基金Project(51775480)supported by the National Natural Science Foundation of ChinaProjects(E2018203143,E2022203050)supported by the Natural Science Foundation of Hebei Province,China。
文摘In this work,the effect of ultrasonic vibration modes on the mechanical properties and relaxation of residual stress in 6061-T6 aluminum alloy was studied.A new ultrasonic vibration Johnson-Cook model was proposed,and the relaxation and distribution of residual stress under ultrasonic vibration were predicted and analyzed using the finite element method(FEM).The mechanical properties of 6061-T6 aluminum alloy under different ultrasonic vibration modes were analyzed through experiments involving notched specimen tensile testing and scanning electron microscopy(SEM)analysis.The findings indicate that ultrasonic vibration treatment during deformation,unloading,and load-holding,as well as treatment with its natural ultrasonic frequency,can effectively release residual stress;however,treatment with its natural frequency has the highest rate of release up to 65.4%.Ultrasonic vibration treatment during deformation better inhibits fracture under the same conditions.The FEM results are in good agreement with the experimental results,and it can be used as a valid tool for predicting residual stress release under ultrasonic vibration.
基金Project supported by the National Natural Science Foundation of China(51971100)Joint Project of Industry-University-Research of Jiangsu Province(BY20230207)。
文摘Mg-RE alloys demonstrate exceptional comprehensive performance,finding widespread applications in biodegradable implants,aerospace,automotive,and other industries.This study investigated Mg-xHo binary alloys(x=1 wt%,3 wt%,5 wt%,7 wt%,9 wt%)synthesized via vacuum arc melting with copper mold cooling.Mechanical properties were evaluated through compression test,revealing that Ho addition significantly enhances the mechanical properties of Mg via solid solution strengthening,grain refinement,and second phase strengthening.The Mg-7Ho alloy exhibits optimal mechanical performa nce,with a co mpressive yield strength(CYS)of 101.2 MPa and ultimate compressive stre ngth(UCS)of274.0 MPa.However,excessive Ho addition leads to grain boundary aggregation,diminishing grain boundary cohesion and increasing susceptibility to intergranular fracture.Corrosion behavior was assessed using electrochemical tests and immersion experiments.A comprehensive analysis of corrosion rates reveals a wide spectrum of responses across different Ho concentrations.Notably,the Mg-1 Ho alloy exhibits the most pronounced corrosion susceptibility,as evidenced by its elevated corrosion current density of 0.043 mA/cm^(2).Conversely,the Mg-5Ho alloy demonstrates superior corrosion resistance,manifesting the lowest corrosion curre nt density of 0.088 mA/cm^(2)among the studied compositions.This phenomenon is attributed to Ho's solid solution in the α-Mg matrix,which elevates matrix potential,and the formation of a corrosion-resistant Ho-containing oxide layer.Additionally,the quantity and distribution of second phases influence corrosion resistance.A higher number of evenly distributed second phases act as a barrier to matrix corrosion rather than as cathodic sites acceleratingα-Mg matrix corrosion.
基金the financial support of the National Natural Science Foundation of China(Nos.52205394,12202251,52305432),ChinaPostdoctoral Science Foundation(No.2021M702024)+3 种基金Ministry of Education Industry-School Cooperative Education Project,China(No.220606517023742)Natural Science Foundation of Shandong Province,China(No.ZR2022QE122)the Open Projects Fund of State Key Laboratory of Mechanical System and Vibration,China(No.MSV202215)Shanghai Key Laboratory of Digital Manufacture of Thin-walled Structure,China(No.202302).
文摘TIG surface remelting was performed to strengthen the surface of ZL109G alloy piston.The macrostructure indicates that surface remelting leads to the production of a remelted zone(RZ).The diameter of the primary Si decreases from 65.8μm in the base metal(BM)to 7.1μm in RZ.The grain size of the RZ is refined to be approximately one-seventh that of the BM.The cellular microstructure in the RZ is characterised by theα(Al)in the centre and intermetallics preferentially located at the cellular boundaries.The results of the mechanical properties demonstrate that the average hardness value of RZ increases by 39%compared to that of BM.For the transverse samples,the ultimate tensile strength increases by~24.5%,which can be attributed to the solution strengthening of Si inα(Al).The average fracture toughness values are 15.0 and 12.7 MPa·m^(1/2)forα(Al)in BM and RZ,respectively.
