Magnesium alloys with excellent degradability and biocompatibility are promising materials for biomedical implants,saving patients the burden of second surgeries.However,their mechanical properties and corrosion resis...Magnesium alloys with excellent degradability and biocompatibility are promising materials for biomedical implants,saving patients the burden of second surgeries.However,their mechanical properties and corrosion resistance are significantly below the requirements for implant applications.This study aims to improve the mechanical and corrosion resistance properties of Mg-3Zn-0.2Ca alloy by pre-torsion treatment,and find out the optimal shear strain.The rod-shaped Mg-3Zn-0.2Ca alloy specimens were pre-torsion treated at different torsion angles.The effect of free-end torsion on Mg-3Zn-0.2Ca alloy was characterized through microstructure analysis,mechanical testing,and corrosion testing.Pre-torsion treatment can refine grain and induce twins and dislocations in Mg-3Zn-0.2Ca alloy.The surface hardness increases with the increase in torsion angle.Tensile yield strength and ultimate strength initially increase and then decrease with increasing torsion angle,while ductility decreases with increasing torsion angle.Specimens with a shear strain of 30%exhibit the highest tensile strength,reaching 284.78±10.62 MPa,with an elongation of 19.37±1.66%.Furthermore,they show a significant improvement in fatigue lives both before and after pre-corrosion.When the stress amplitude is 120 MPa,the fatigue lives for specimens without pre-torsion treatment are 54,275 cycles and 4324 cycles before and after pre-corrosion,while they increased significantly to 92,015 cycles and 5050 cycles with the 30%shear strain,respectively.Additionally,the 30%shear strain specimens show a significant reduction in corrosion rates.In conclusion,pre-torsion treatment can effectively modify the microstructure of Mg-3Zn-0.2Ca alloy,enhancing both mechanical properties and corrosion resistance.The optimal shear strain for this improvement is 30%.This study provides a practical method to enhance the mechanical properties and corrosion resistance of Mg-3Zn-0.2Ca alloy,making it more suitable for biomedical implant applications.展开更多
An air source heat pump system (ASHPS) used in an office building is set up and studied experimentally. Its operating performance in winter is evaluated based on test data and a comparative discussion is given on the ...An air source heat pump system (ASHPS) used in an office building is set up and studied experimentally. Its operating performance in winter is evaluated based on test data and a comparative discussion is given on the effect of climate conditions and heating load ratio on the operation behavior. Then heating capacity variation caused by evaporator frosting is analyzed as well. Finally, the defrosting parameters and the technical feasibility are studied for a constant heating demand. The experimental results indicate that both the outlet water temperature drop and the system COP should be taken into account when setting defrosting parameters, and ASHPS is a viable technology for space heating and hot-water production in winter in Tianjin, which can maintain the room temperature above 19 ℃ when the outdoor temperature is -2 ℃.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
Mechanical stimuli play critical roles in cardiovascular diseases,in which in vivo stresses in blood vessels present a great challenge to predict.Based on the structural-thermal coupled finite element method,we propos...Mechanical stimuli play critical roles in cardiovascular diseases,in which in vivo stresses in blood vessels present a great challenge to predict.Based on the structural-thermal coupled finite element method,we propose a thermal expansion method to estimate stresses in multi-layer blood vessels under healthy and pathological conditions.The proposed method provides a relatively simple and convenient means to predict reliable in vivo mechanical stresses with accurate residual stress.The method is first verified with the opening-up process and the pressure-radius responses for single and multi-layer vessel models.It is then applied to study the stress variation in a human carotid artery at different hypertension stages and in a plaque of vascular stenosis.Our results show that specific or optimal residual stresses exist for different blood pressures,which helps form a homogeneous stress distribution across vessel walls.High elastic shear stress is identified on the shoulder of the plaque,which contributes to the tearing effect in plaque rupture.The present study indicates that the proposed numerical method is a capable and efficient in vivo stress evaluation of patient-specific blood vessels for clinical purposes.展开更多
Analysis, evaluation and interpretation of measured signals become important components in engineering research and practice, especially for material characteristic parameters which can not be obtained directly by exp...Analysis, evaluation and interpretation of measured signals become important components in engineering research and practice, especially for material characteristic parameters which can not be obtained directly by experimental measurements. The present paper proposes a hybrid-inverse analysis method for the identification of the nonlinear material parameters of any individual component from the mechanical responses of a global composite. The method couples experimental approach, numerical simulation with inverse search method. The experimental approach is used to provide basic data. Then parameter identification and numerical simulation are utilized to identify elasto-plastic material properties by the experimental data obtained and inverse searching algorithm. A numerical example of a stainless steel clad copper sheet is consid- ered to verify and show the applicability of the proposed hybrid-inverse method. In this example, a set of material parameters in an elasto-plastic constitutive model have been identified by using the obtained experimental data.展开更多
The force model during needle insertion into soft tissue is important for accurate percutaneous intervention.In this paper,a force model for needle insertion into a tissue- equivalent material is presented and a serie...The force model during needle insertion into soft tissue is important for accurate percutaneous intervention.In this paper,a force model for needle insertion into a tissue- equivalent material is presented and a series of experiments are conducted to acquire data from needle soft- tissue interaction process.In order to build a more accurate insertion force model,the interaction force between a surgical needle and soft tissue is divided into three parts:stiffness force,friction force,and cutting force.The stiffness force is modeled on the basis of contact mechanics model.The friction force model is presented using a modified Winkler' s foundation model.The cutting force is viewed as a constant depending on a given tissue.The proposed models in the paper are established on the basis of the mechanical properties and geometric parameters of the needle and soft tissue.The experimental results illustrate that the force models are capable of predicting the needle-tissue interaction force.The force models of needle insertion can provide real-time haptic feedback for robot-assisted procedures,thereby improving the accuracy and safety of surgery.展开更多
This study aims to investigate the regional variations of trabecular morphological parameters and mechanical parameters of the femoral head,as well as to determine the relationship between trabecular morphological and...This study aims to investigate the regional variations of trabecular morphological parameters and mechanical parameters of the femoral head,as well as to determine the relationship between trabecular morphological and mechanical parameters.Seven femoral heads from patients with fractured proximal femur were scanned using a micro-CT system.Each femoral head was divided into 12 sub-regions according to the trabecular orientation.One 125 mm^3 trabecular cubic model was reconstructed from each sub-region.A total of 81 trabecular models were reconstructed,except three destroyed sub-regions from two femoral heads during the surgery.Trabecular morphological parameters,i.e.trabecular separation（Tb.Sp）,trabecular thickness（Tb.Th）,specific bone surface（BS/B V）,bone volume fraction（BV/TV）,structural model index（SMI）,and degree of anisotropy（DA） were measured.Micro-finite element analyses were performed for each cube to obtain the apparent Young＇s modulus and tissue level von Mises stress distribution under 1%compressive strain along three orthogonal directions,respectively.Results revealed significant regional variations in the morphological parameters（P〈0.05）.Young＇s moduli along the trabecular orientation were significantly higher than those along the other two directions.In general,trabecular mechanical properties in the medial region were lower than those in the lateral region.Trabecular mechanical parameters along the trabecular orientation were significantly correlated with BS/BV,BV/TV,Tb.Th,and DA.In this study,regional variations of microstructural features and mechanical properties in the femoral head of patients with proximal femur fracture were thoroughly investigated at the tissue level.The results of this study will help to elucidate the mechanism of femoral head fracture for reducing fracture risk and developing treatment strategies for the elderly.展开更多
In a hybrid system, the subsystems with discrete dynamics play a central role in a hybrid system. In the course of engineering machinery of cluster construction, the discrete control law is hard to obtain because the ...In a hybrid system, the subsystems with discrete dynamics play a central role in a hybrid system. In the course of engineering machinery of cluster construction, the discrete control law is hard to obtain because the construction environment is complex and there exist many affecting factors. In this paper, hierarchically intelligent control, expert control and fuzzy control are introduced into the discrete subsystems of engineering machinery of cluster hybrid system, so as to rebuild the hybrid system and make the discrete control law easily and effectively obtained. The structures, reasoning mechanism and arithmetic of intelligent control are replanted to discrete dynamic, conti- nuous process and the interface of the hybrid system. The structures of three types of intelligent hybrid system are presented and the human experiences summarized from engineering machinery of cluster are taken into account.展开更多
Mechanical properties of micro-structured porous silicon film （PS） were studied combining X-ray diffraction with micro-Raman spectroscopy. The micro-structured porous silicon samples with different porosities rangin...Mechanical properties of micro-structured porous silicon film （PS） were studied combining X-ray diffraction with micro-Raman spectroscopy. The micro-structured porous silicon samples with different porosities ranging from 30.7700 to 96.2500 were obtained by chemical etching. Lattice parameters of the samples were measured using X-ray diffraction and its maximal change is up to （1.000.） This lattice mismatch with the bulk silicon substrate may introduce residual stress to the porous film. The residual stress measurement by micro-Raman spectroscopy reveals that the maximum of tensile residual stress has reached GPa level in the porous film. Moreover, the lattice mismatch and its corresponding residual stress are increasing with the porosity of PS, but average （elastic） modulus is about 14.5 GPa, one order of magnitude lower than that of substrate Si. The mechanical properties of PS have a close relation with its micro-pore structure.展开更多
Hydroxyapatite bioceramics is simulated by using finite element method （FEM）. The influences of porosity, hole shape, angle of crack and other parameters on the ceramics are analyzed. The results show that with the ...Hydroxyapatite bioceramics is simulated by using finite element method （FEM）. The influences of porosity, hole shape, angle of crack and other parameters on the ceramics are analyzed. The results show that with the increase of the angle between crack and horizontal direction, the stress intensity factor KⅠ decreases gradually, but stress intensity factor KⅡ increases at first and then it decreases. The value of KⅡ reaches maximum when the angle between crack and horizontal direction is 45°. KⅠ and KⅡ rise with the increase of porosity, and they are almost the same for the circular and hexagonal holes. For elliptical holes, KⅠ and KⅡ reach maximum when the long axis of ellipse is perpendicular to the loading direction and they reach minimum when the same axis is parallel to the loading direction. Moreover, with the increase of the angle between the long axis and loading direction, KⅠ and KⅡ increase gradually.展开更多
7075 aluminum alloy is often used as an important load-bearing structure in aircraft industry due to its superior mechanical properties.During the process of deep hole boring,the boring bar is prone to vibrate because...7075 aluminum alloy is often used as an important load-bearing structure in aircraft industry due to its superior mechanical properties.During the process of deep hole boring,the boring bar is prone to vibrate because of its limited machining space,bad environment and large elongation induced low stiffness.To reduce vibration and improve machined surface quality,a particle damping boring bar,filled with particles in its inside damping block,is designed based on the theory of vibration control.The theoretical damping coefficient is determined,then the boring bar structure is designed and trial-manufactured.Experimental studies through impact testing show that cemented carbide particles with a diameter of 5 mm and a filling rate of 70% achieve a damping ratio of 19.386%,providing excellent vibration reduction capabilities,which may reduce the possibility of boring vibration.Then,experiments are setup to investigate its vibration reduction performance during deep hole boring of 7075 aluminum alloy.To observe more obviously,severe working conditions are adopted and carried out to acquire the time domain vibration signal of the head of the boring bar and the surface morphologies and roughness values of the workpieces.By comparing different experimental results,it is found that the designed boring bar could reduce the maximum vibration amplitude by up to 81.01% and the surface roughness value by up to 47.09% compared with the ordinary boring bar in two sets of experiments,proving that the designed boring bar can effectively reduce vibration.This study can offer certain valuable insights for the machining of this material.展开更多
The trade-off between mechanistic interpretability,operational convenience,and predictive accuracy is challenging for predicting the lifetime of lithium-ion batteries.To resolve this contradiction,we propose a damage ...The trade-off between mechanistic interpretability,operational convenience,and predictive accuracy is challenging for predicting the lifetime of lithium-ion batteries.To resolve this contradiction,we propose a damage model based on fatigue damage theory and electrochemical impedance spectroscopy.The causal relationship of“fatigue damage→resistance increase→capacity fading”is revealed to describe the underlying mechanism.Charge transfer resistance is chosen as the variable to ensure the convenience of data acquisition.To verify the accuracy of the model,the electrochemical impedance spectrum and capacity of a graphene-coated silicon electrode at two charging rates are collected and analyzed.50% and 75% of the measured data are utilized as inputs to compare the prediction capabilities of the proposed damage model and the existing empirical model.The particle filter algorithm is adopted to train the parameters of both models.The maximum prediction error of the damage model is less than 3%,showing better prediction accuracy and medium-term prediction stability than the empirical model.Our work demonstrates that the proposed damage model is an effective way to resolve contradictions in lifetime prediction.展开更多
Any product must undergo precise manufacturing before use.The damage incurred during the manufacturing process can significantly impact the residual strength of the product post-manufacturing.However,the relationship ...Any product must undergo precise manufacturing before use.The damage incurred during the manufacturing process can significantly impact the residual strength of the product post-manufacturing.However,the relationship between residual bending strength and manufacturing-induced damage remains unclear,despite being a crucial parameter for assessing material service life and performance,leading to a decrease in product performance reliability.This study focuses on investigating the impact of crack generation on residual bending strength through theoretical and experimental analyses of scratching,grinding,and three-point bending.The research first elucidates the forms and mechanisms of material damage through scratch experiments.Subsequently,using resin-bonded and electroplated wheels as case studies,the influence of different process parameters on grinding damage and residual bending strength is explored.The reduction of brittle removal can lead to a 50%–60%decrease in residual bending strength.Lastly,a model is developed to delineate the relationship between processing parameters and the residual bending strength of the product,with the model exhibiting an error margin of less than 11%.This model clearly reveals the effect of crack generation under different process parameters on residual flexural strength.展开更多
Monocrystalline Cu exhibits excellent electrical and signal-transmission properties due to its absence of grain boundaries,making it a critical material for the production of micro-machinery and micro-components;howev...Monocrystalline Cu exhibits excellent electrical and signal-transmission properties due to its absence of grain boundaries,making it a critical material for the production of micro-machinery and micro-components;however,achieving ultrahigh precision and ultralow damage machining of functional devices using traditional techniques such as grinding and polishing is extremely challenging.Consequently,nanocutting has emerged as an efficient means to fabricate monocrystalline materials with complex surface characteristics and high surface integrity.Nevertheless,the macroscopic cutting theory of metal materials cannot be applied to nanocutting.Accordingly,in this paper,both simulations and experiments were conducted to examine the chip deformation mechanisms of monocrystalline Cu.First,large-scale molecular dynamics(MD)simulations were conducted to gain a comprehensive understanding of the deformation behavior during nanocutting.This included examining the influencing factors and the variation patterns of the chip deformation coefficient,cutting force,and minimum cutting thickness.Subsequently,nanocutting experiments were performed using a specially designed nanocutting platform with high-resolution online observation by scanning electron microscopy.The experimental results served to verify the accuracy and reliability of theMDmodeling,as they exhibited excellent consistency with the simulated results.Although this work considered monocrystalline Cu,it is believed that the elucidated chip deformation mechanisms could also be applied to other face-centered-cubic metals.These results are of great value for advancing the understanding of the mechanisms of ultraprecision cutting.展开更多
The concept of non-Hermitian mechanics introduces new dimensions to metamaterial research,yet current studies have primarily focused on wave manipulation,neglecting the vibration transmittance characteristics of finit...The concept of non-Hermitian mechanics introduces new dimensions to metamaterial research,yet current studies have primarily focused on wave manipulation,neglecting the vibration transmittance characteristics of finite-size metamaterials with boundary reflections.This paper explores the asymmetric vibration transmittance characteristics of a simply supported NonHermitian Metamaterial Panel(NHMP)with two lossy resonators,under the impact of supersonic aerodynamic forces.By examining the non-Hermiticity of a non-aerodynamically loaded NHMP and a host panel aeroelastic system separately,we demonstrate that the NHMP subjected to supersonic aerodynamic force is a complex non-Hermitian system,exhibiting asymmetric vibration transmittance driven by both the fluid-structure interaction effect and lossy resonators.We theoretically and numerically clarify that an ideal aeroelastic system,such as a host panel aeroelastic system,functions as a non-Hermitian mechanical system due to the fluid-structure interaction effect,with the critical flutter point aligning with the Exceptional Point(EP).The results of this study indicate that at low dynamic pressures,the lossy resonators primarily govern asymmetric vibration transmittance,whereas at high dynamic pressures,the fluid-structure interaction effect becomes the dominant factor.Notably,at the EP,asymmetric vibration transmittance is unaffected by the mass ratio of lossy resonators,which is attributed to the invariance of the operational deflection shapes of the NHMP at the EP.This study offers a novel perspective on panel aeroelastic systems and nonHermitian metamaterials,advancing the field through its comprehensive analyses.展开更多
To address the critical need for safer and cleaner explosion suppression technologies in industrial settings,the suppression differences and mechanisms of the flame acceleration characteristics of CH_(4),LPG and H_(2)...To address the critical need for safer and cleaner explosion suppression technologies in industrial settings,the suppression differences and mechanisms of the flame acceleration characteristics of CH_(4),LPG and H_(2) explosions by N_(2)-water mist two-phase medium were investigated.The flame acceleration characteristics and suppression mechanism of methane,LPG and H_(2) explosions in N_(2)-water mist twophase medium were studied qualitatively and quantitatively from both experimental and simulation aspects.The experimental results show that compared with single N_(2) or water mist,the N_(2)-water mist two-phase medium is more effective in reducing the flame propagation speed and delaying the formation of flame hydrodynamic structure,thus slowing down the flame acceleration characteristics.The simulation results show that this two-phase medium exhibits a strong inhibitory effect on the thermal diffusion instability of CH_(4) and LPG,and significantly weakens the hydrodynamic instability of CH_(4),LPG,and H_(2) simultaneously.Mechanistic analysis confirms that the N_(2)-water mist two-phase medium has both chemical and physical inhibitory effects,among which the physical inhibition plays a dominant role.In addition,the study reveals a linear correlation between the concentration of H radicals in the three combustible gases and the laminar burning velocity.Moreover,this two-phase medium can significantly reduce the reaction rate of the H radical chain reaction,thereby effectively suppressing the laminar burning velocity.展开更多
At low-Reynolds-number,the performance of airfoil is known to be greatly affected by the formation and burst of a laminar separation bubble(LSB),which requires a more precise simulation of the delicate flow structures...At low-Reynolds-number,the performance of airfoil is known to be greatly affected by the formation and burst of a laminar separation bubble(LSB),which requires a more precise simulation of the delicate flow structures.A framework based on the interior penalty discontinuous Galerkin method and large eddy simulation approach was adopted in the present study.The performances of various subgrid models,including the Smagorinsky(SM)model,the dynamic Smagorinsky(DSM)model,the wall-adapting local-eddy-viscosity(WALE)model,and the VREMAN model,have been analyzed through flow simulations of the SD7003 airfoil at a Reynolds number of 60000.It turns out that the SM model fails to predict the emergence of LSB,even modified by the Van-Driest damping function.On the contrary,the best agreement is generally achieved by the WALE model in terms of flow separation,reattachment,and transition locations,together with the aerodynamic loads.Furthermore,the influence of numerical dissipation has also been discussed through the comparison of skin friction and resolved Reynolds stresses.As numerical dissipation decreases,the prediction accuracy of the WALE model degrades.Meanwhile,nonlinear variation could be observed from the performances of the DSM model,which could be attributed to the interaction between the numerical dissipation and the subgrid model.展开更多
The type and quantity of active sites on a catalyst surface determine catalytic activity.In this study,machine learning was employed to assist in the construction of C=O and pyridine N active sites using sludge waste....The type and quantity of active sites on a catalyst surface determine catalytic activity.In this study,machine learning was employed to assist in the construction of C=O and pyridine N active sites using sludge waste.Reactive descriptors,including C%,N%,O%,Fe%,pyrolysis temperature,heating rate,and pyrolysis time were proposed.Decision tree,extra tree,extreme gradient boosting(XGB),automatic relevance determination,and Bayesian ridge regression models were constructed and optimized.Among these,the XGB model was demonstrated with superior accuracy for prediction of C=O sites on the catalyst surface.Additionally,an ensemble model combining extra trees and XGB was developed to predict pyridine N,with R~2 value as high as 0.80 and minimum root mean square error(RMSE)of 0.1386.The ensemble model demonstrated a 17%improvement in accuracy compared to individual models.The model enables high-throughput screening of construction conditions for C=O and pyridine N.The study found that a pyrolysis temperature above of 500–800℃,a heating rate of 10–20℃/min,and a heating time of 120–200 min favor the generation of C=O active sites.For pyridine N sites,a pyrolysis temperature between 400℃ and 600℃,a heating rate of 5–10℃/min,and a pyrolysis time of around 150 min are optimal.Experimental validation demonstrated that both models exhibit excellent predictive performance,with prediction errors below 10%in all cases.This research provides a method to assist in the construction of C=O and pyridine N active sites,which is beneficial for guiding the design of sludge catalysts.展开更多
Driven by the global“dual-carbon”goals,hydrogen fuel cell electric vehicles(FCEVs)are being rapidly promoted as a zero-emission transportation solution.However,their large-scale application is constrained by issues ...Driven by the global“dual-carbon”goals,hydrogen fuel cell electric vehicles(FCEVs)are being rapidly promoted as a zero-emission transportation solution.However,their large-scale application is constrained by issues such as inefficient operation,poor information flow between vehicles and stations,and potential safety hazards,which are caused by insufficient intelligence of hydrogen refueling stations.This study aims to address these problems by deeply integrating Cellular Vehicle-to-Everything(C-V2X)technology with hydrogen refueling stations,thereby building a safe,efficient,and low-carbon hydrogen energy application ecosystem to promote the global transition to zero-carbon transportation.Firstly,through literature review and technical analysis,this study expounds on the core technologies and process flows of current hydrogen refueling stations,aswell as the technical architecture and development evolution of C-V2X technology.Then,based on the analysis of relevant literature,it proposes a“vehicle-road-station-cloud”collaborative architecture that integrates C-V2X with hydrogen refueling stations.Combined with 5G communication and big data technologies,it elaborates on the implementation path for achieving real-time data interaction among hydrogen refueling stations,hydrogen-powered vehicles,and road infrastructure.This interconnection mode enables hydrogen refueling stations to obtain real-time information of surrounding vehicles,which plays an important role in building a safe,efficient,and low-carbon hydrogen energy application ecosystem and promoting the global transition to zero-carbon transportation.Finally,the future development prospects and potential of this scheme are put forward.展开更多
A dislocation density-based crystal plasticity finite element(CPFE)model is developed to reveal the mechanism of discontinuous dynamic recrystallization(DDRX)of the TC17 dual-phase titanium alloy during hot deformatio...A dislocation density-based crystal plasticity finite element(CPFE)model is developed to reveal the mechanism of discontinuous dynamic recrystallization(DDRX)of the TC17 dual-phase titanium alloy during hot deformation.The model incorporates the temperature and strain rate dependence of nucleation,growth and evolution during DDRX.The evolution of the dislocation densities in the matrix grains(MGs)and the recrystallized grains(RGs)is considered individually.The mechanical response and underlying microstructural evolution are systematically investigated by comparing the CPFE model predictions with experimental tests.The results indicate that at lower temperatures(700℃ and 800℃),TC17 titanium alloy exhibits a higher volume fraction of recrystallization and a notable drop in flow stress.As the temperature increases(900℃ and 1000℃),the volume fraction of recrystallization decreases,resulting in a weakened flow stress softening.The nucleation rate of DDRX increases with decreasing deformation temperature and increasing strain rate,while the size of RGs increases with higher temperature and lower strain rate.DDRX nuclei primarily occur at grain boundaries with high dislocation density.Furthermore,DDRX consumes a large number of dislocations and thus reduces the stress concentration and dislocation density at grain boundaries.This study provides a robust model that enhances the understanding of hot deformation mechanisms and informs the design of high-performance titanium alloys for future applications.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52105158,32271371,and U23A6009)the China Postdoctoral Science Foundation(No.2023M742586)+1 种基金the Tianjin Natural Science Foundation(Nos.21JCONJC01310 and 21JCYBJC00940)the Science and Technology Commissioner Foundation of Tianjin(22YDTPJC00660).
文摘Magnesium alloys with excellent degradability and biocompatibility are promising materials for biomedical implants,saving patients the burden of second surgeries.However,their mechanical properties and corrosion resistance are significantly below the requirements for implant applications.This study aims to improve the mechanical and corrosion resistance properties of Mg-3Zn-0.2Ca alloy by pre-torsion treatment,and find out the optimal shear strain.The rod-shaped Mg-3Zn-0.2Ca alloy specimens were pre-torsion treated at different torsion angles.The effect of free-end torsion on Mg-3Zn-0.2Ca alloy was characterized through microstructure analysis,mechanical testing,and corrosion testing.Pre-torsion treatment can refine grain and induce twins and dislocations in Mg-3Zn-0.2Ca alloy.The surface hardness increases with the increase in torsion angle.Tensile yield strength and ultimate strength initially increase and then decrease with increasing torsion angle,while ductility decreases with increasing torsion angle.Specimens with a shear strain of 30%exhibit the highest tensile strength,reaching 284.78±10.62 MPa,with an elongation of 19.37±1.66%.Furthermore,they show a significant improvement in fatigue lives both before and after pre-corrosion.When the stress amplitude is 120 MPa,the fatigue lives for specimens without pre-torsion treatment are 54,275 cycles and 4324 cycles before and after pre-corrosion,while they increased significantly to 92,015 cycles and 5050 cycles with the 30%shear strain,respectively.Additionally,the 30%shear strain specimens show a significant reduction in corrosion rates.In conclusion,pre-torsion treatment can effectively modify the microstructure of Mg-3Zn-0.2Ca alloy,enhancing both mechanical properties and corrosion resistance.The optimal shear strain for this improvement is 30%.This study provides a practical method to enhance the mechanical properties and corrosion resistance of Mg-3Zn-0.2Ca alloy,making it more suitable for biomedical implant applications.
基金Supported bythe"11th Five-Year Plan"for National Plans of Major Technology Projects
文摘An air source heat pump system (ASHPS) used in an office building is set up and studied experimentally. Its operating performance in winter is evaluated based on test data and a comparative discussion is given on the effect of climate conditions and heating load ratio on the operation behavior. Then heating capacity variation caused by evaporator frosting is analyzed as well. Finally, the defrosting parameters and the technical feasibility are studied for a constant heating demand. The experimental results indicate that both the outlet water temperature drop and the system COP should be taken into account when setting defrosting parameters, and ASHPS is a viable technology for space heating and hot-water production in winter in Tianjin, which can maintain the room temperature above 19 ℃ when the outdoor temperature is -2 ℃.
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The authors would like to thank Prof.Shu Takagi and Prof.Huaxiong Huang for their instructive comments.The authors would also like to acknowledge Jianda Yang for assisting with FEM simulations.This work was supported by the National Natural Science Foundation of China(Grants 11372191,11232010,11650(Grant 91111138)the National Institute of Health(Grant 2R01DC005642-10A1).
文摘Mechanical stimuli play critical roles in cardiovascular diseases,in which in vivo stresses in blood vessels present a great challenge to predict.Based on the structural-thermal coupled finite element method,we propose a thermal expansion method to estimate stresses in multi-layer blood vessels under healthy and pathological conditions.The proposed method provides a relatively simple and convenient means to predict reliable in vivo mechanical stresses with accurate residual stress.The method is first verified with the opening-up process and the pressure-radius responses for single and multi-layer vessel models.It is then applied to study the stress variation in a human carotid artery at different hypertension stages and in a plaque of vascular stenosis.Our results show that specific or optimal residual stresses exist for different blood pressures,which helps form a homogeneous stress distribution across vessel walls.High elastic shear stress is identified on the shoulder of the plaque,which contributes to the tearing effect in plaque rupture.The present study indicates that the proposed numerical method is a capable and efficient in vivo stress evaluation of patient-specific blood vessels for clinical purposes.
基金supported by the National Natural Science Foundation of China (Nos.10732080 and 10572102)National Basic Research Program of China (No.2007CB714000)
文摘Analysis, evaluation and interpretation of measured signals become important components in engineering research and practice, especially for material characteristic parameters which can not be obtained directly by experimental measurements. The present paper proposes a hybrid-inverse analysis method for the identification of the nonlinear material parameters of any individual component from the mechanical responses of a global composite. The method couples experimental approach, numerical simulation with inverse search method. The experimental approach is used to provide basic data. Then parameter identification and numerical simulation are utilized to identify elasto-plastic material properties by the experimental data obtained and inverse searching algorithm. A numerical example of a stainless steel clad copper sheet is consid- ered to verify and show the applicability of the proposed hybrid-inverse method. In this example, a set of material parameters in an elasto-plastic constitutive model have been identified by using the obtained experimental data.
基金Supported by the National Natural Science Foundation of China(No.51175373)New Century Educational Talents Plan of Chinese Education Ministry(No.NCET-10-0625)+1 种基金Key Technology and Development Program of Tianjin Municipal Science and Technology Commission(No.12ZCDZSY10600)Tianjin Key Laboratory of High Speed Cutting&Precision Machining(TUTE)(2013120024001167)
文摘The force model during needle insertion into soft tissue is important for accurate percutaneous intervention.In this paper,a force model for needle insertion into a tissue- equivalent material is presented and a series of experiments are conducted to acquire data from needle soft- tissue interaction process.In order to build a more accurate insertion force model,the interaction force between a surgical needle and soft tissue is divided into three parts:stiffness force,friction force,and cutting force.The stiffness force is modeled on the basis of contact mechanics model.The friction force model is presented using a modified Winkler' s foundation model.The cutting force is viewed as a constant depending on a given tissue.The proposed models in the paper are established on the basis of the mechanical properties and geometric parameters of the needle and soft tissue.The experimental results illustrate that the force models are capable of predicting the needle-tissue interaction force.The force models of needle insertion can provide real-time haptic feedback for robot-assisted procedures,thereby improving the accuracy and safety of surgery.
基金supported by the National Natural Science Foundation of China(Nos.11322223,11432016,81471753 and 11272134)the 973 Program(No.2012CB821202)
文摘This study aims to investigate the regional variations of trabecular morphological parameters and mechanical parameters of the femoral head,as well as to determine the relationship between trabecular morphological and mechanical parameters.Seven femoral heads from patients with fractured proximal femur were scanned using a micro-CT system.Each femoral head was divided into 12 sub-regions according to the trabecular orientation.One 125 mm^3 trabecular cubic model was reconstructed from each sub-region.A total of 81 trabecular models were reconstructed,except three destroyed sub-regions from two femoral heads during the surgery.Trabecular morphological parameters,i.e.trabecular separation（Tb.Sp）,trabecular thickness（Tb.Th）,specific bone surface（BS/B V）,bone volume fraction（BV/TV）,structural model index（SMI）,and degree of anisotropy（DA） were measured.Micro-finite element analyses were performed for each cube to obtain the apparent Young＇s modulus and tissue level von Mises stress distribution under 1%compressive strain along three orthogonal directions,respectively.Results revealed significant regional variations in the morphological parameters（P〈0.05）.Young＇s moduli along the trabecular orientation were significantly higher than those along the other two directions.In general,trabecular mechanical properties in the medial region were lower than those in the lateral region.Trabecular mechanical parameters along the trabecular orientation were significantly correlated with BS/BV,BV/TV,Tb.Th,and DA.In this study,regional variations of microstructural features and mechanical properties in the femoral head of patients with proximal femur fracture were thoroughly investigated at the tissue level.The results of this study will help to elucidate the mechanism of femoral head fracture for reducing fracture risk and developing treatment strategies for the elderly.
文摘In a hybrid system, the subsystems with discrete dynamics play a central role in a hybrid system. In the course of engineering machinery of cluster construction, the discrete control law is hard to obtain because the construction environment is complex and there exist many affecting factors. In this paper, hierarchically intelligent control, expert control and fuzzy control are introduced into the discrete subsystems of engineering machinery of cluster hybrid system, so as to rebuild the hybrid system and make the discrete control law easily and effectively obtained. The structures, reasoning mechanism and arithmetic of intelligent control are replanted to discrete dynamic, conti- nuous process and the interface of the hybrid system. The structures of three types of intelligent hybrid system are presented and the human experiences summarized from engineering machinery of cluster are taken into account.
文摘Mechanical properties of micro-structured porous silicon film （PS） were studied combining X-ray diffraction with micro-Raman spectroscopy. The micro-structured porous silicon samples with different porosities ranging from 30.7700 to 96.2500 were obtained by chemical etching. Lattice parameters of the samples were measured using X-ray diffraction and its maximal change is up to （1.000.） This lattice mismatch with the bulk silicon substrate may introduce residual stress to the porous film. The residual stress measurement by micro-Raman spectroscopy reveals that the maximum of tensile residual stress has reached GPa level in the porous film. Moreover, the lattice mismatch and its corresponding residual stress are increasing with the porosity of PS, but average （elastic） modulus is about 14.5 GPa, one order of magnitude lower than that of substrate Si. The mechanical properties of PS have a close relation with its micro-pore structure.
基金Supported by National Natural Science Foundation of China (No.10772133 and No.11072172)Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20090032110006)
文摘Hydroxyapatite bioceramics is simulated by using finite element method （FEM）. The influences of porosity, hole shape, angle of crack and other parameters on the ceramics are analyzed. The results show that with the increase of the angle between crack and horizontal direction, the stress intensity factor KⅠ decreases gradually, but stress intensity factor KⅡ increases at first and then it decreases. The value of KⅡ reaches maximum when the angle between crack and horizontal direction is 45°. KⅠ and KⅡ rise with the increase of porosity, and they are almost the same for the circular and hexagonal holes. For elliptical holes, KⅠ and KⅡ reach maximum when the long axis of ellipse is perpendicular to the loading direction and they reach minimum when the same axis is parallel to the loading direction. Moreover, with the increase of the angle between the long axis and loading direction, KⅠ and KⅡ increase gradually.
基金supported by the Scientific Research Program of Tianjin Education Committee(No.2022ZD030)。
文摘7075 aluminum alloy is often used as an important load-bearing structure in aircraft industry due to its superior mechanical properties.During the process of deep hole boring,the boring bar is prone to vibrate because of its limited machining space,bad environment and large elongation induced low stiffness.To reduce vibration and improve machined surface quality,a particle damping boring bar,filled with particles in its inside damping block,is designed based on the theory of vibration control.The theoretical damping coefficient is determined,then the boring bar structure is designed and trial-manufactured.Experimental studies through impact testing show that cemented carbide particles with a diameter of 5 mm and a filling rate of 70% achieve a damping ratio of 19.386%,providing excellent vibration reduction capabilities,which may reduce the possibility of boring vibration.Then,experiments are setup to investigate its vibration reduction performance during deep hole boring of 7075 aluminum alloy.To observe more obviously,severe working conditions are adopted and carried out to acquire the time domain vibration signal of the head of the boring bar and the surface morphologies and roughness values of the workpieces.By comparing different experimental results,it is found that the designed boring bar could reduce the maximum vibration amplitude by up to 81.01% and the surface roughness value by up to 47.09% compared with the ordinary boring bar in two sets of experiments,proving that the designed boring bar can effectively reduce vibration.This study can offer certain valuable insights for the machining of this material.
基金supported by the National Natural Science Foundation of China(12021002,12472183,and 12041201).
文摘The trade-off between mechanistic interpretability,operational convenience,and predictive accuracy is challenging for predicting the lifetime of lithium-ion batteries.To resolve this contradiction,we propose a damage model based on fatigue damage theory and electrochemical impedance spectroscopy.The causal relationship of“fatigue damage→resistance increase→capacity fading”is revealed to describe the underlying mechanism.Charge transfer resistance is chosen as the variable to ensure the convenience of data acquisition.To verify the accuracy of the model,the electrochemical impedance spectrum and capacity of a graphene-coated silicon electrode at two charging rates are collected and analyzed.50% and 75% of the measured data are utilized as inputs to compare the prediction capabilities of the proposed damage model and the existing empirical model.The particle filter algorithm is adopted to train the parameters of both models.The maximum prediction error of the damage model is less than 3%,showing better prediction accuracy and medium-term prediction stability than the empirical model.Our work demonstrates that the proposed damage model is an effective way to resolve contradictions in lifetime prediction.
基金Supported by National Key Research and Development Program of China(Grant No.2023YFB3711100)National Natural Science Foundation of China(Grant Nos.52275458,52275207)Tianjin Municipal Natural Science Foundation(Grant No.22JCZDJC00050)。
文摘Any product must undergo precise manufacturing before use.The damage incurred during the manufacturing process can significantly impact the residual strength of the product post-manufacturing.However,the relationship between residual bending strength and manufacturing-induced damage remains unclear,despite being a crucial parameter for assessing material service life and performance,leading to a decrease in product performance reliability.This study focuses on investigating the impact of crack generation on residual bending strength through theoretical and experimental analyses of scratching,grinding,and three-point bending.The research first elucidates the forms and mechanisms of material damage through scratch experiments.Subsequently,using resin-bonded and electroplated wheels as case studies,the influence of different process parameters on grinding damage and residual bending strength is explored.The reduction of brittle removal can lead to a 50%–60%decrease in residual bending strength.Lastly,a model is developed to delineate the relationship between processing parameters and the residual bending strength of the product,with the model exhibiting an error margin of less than 11%.This model clearly reveals the effect of crack generation under different process parameters on residual flexural strength.
基金support of the National Natural Science Foundation of China(Grant No.51805371)the Innovation and Entrepreneurship Training Program of Tianjin University of Commerce(Grant No.202310069067).
文摘Monocrystalline Cu exhibits excellent electrical and signal-transmission properties due to its absence of grain boundaries,making it a critical material for the production of micro-machinery and micro-components;however,achieving ultrahigh precision and ultralow damage machining of functional devices using traditional techniques such as grinding and polishing is extremely challenging.Consequently,nanocutting has emerged as an efficient means to fabricate monocrystalline materials with complex surface characteristics and high surface integrity.Nevertheless,the macroscopic cutting theory of metal materials cannot be applied to nanocutting.Accordingly,in this paper,both simulations and experiments were conducted to examine the chip deformation mechanisms of monocrystalline Cu.First,large-scale molecular dynamics(MD)simulations were conducted to gain a comprehensive understanding of the deformation behavior during nanocutting.This included examining the influencing factors and the variation patterns of the chip deformation coefficient,cutting force,and minimum cutting thickness.Subsequently,nanocutting experiments were performed using a specially designed nanocutting platform with high-resolution online observation by scanning electron microscopy.The experimental results served to verify the accuracy and reliability of theMDmodeling,as they exhibited excellent consistency with the simulated results.Although this work considered monocrystalline Cu,it is believed that the elucidated chip deformation mechanisms could also be applied to other face-centered-cubic metals.These results are of great value for advancing the understanding of the mechanisms of ultraprecision cutting.
基金co-supported by the National Natural Science Foundation of China(Nos.12372170,12402104 and 12072276)the National Science Basic Research Program of Shaanxi Province,China(No.2022JM-047)the 111 Project of China(No.BP0719007)。
文摘The concept of non-Hermitian mechanics introduces new dimensions to metamaterial research,yet current studies have primarily focused on wave manipulation,neglecting the vibration transmittance characteristics of finite-size metamaterials with boundary reflections.This paper explores the asymmetric vibration transmittance characteristics of a simply supported NonHermitian Metamaterial Panel(NHMP)with two lossy resonators,under the impact of supersonic aerodynamic forces.By examining the non-Hermiticity of a non-aerodynamically loaded NHMP and a host panel aeroelastic system separately,we demonstrate that the NHMP subjected to supersonic aerodynamic force is a complex non-Hermitian system,exhibiting asymmetric vibration transmittance driven by both the fluid-structure interaction effect and lossy resonators.We theoretically and numerically clarify that an ideal aeroelastic system,such as a host panel aeroelastic system,functions as a non-Hermitian mechanical system due to the fluid-structure interaction effect,with the critical flutter point aligning with the Exceptional Point(EP).The results of this study indicate that at low dynamic pressures,the lossy resonators primarily govern asymmetric vibration transmittance,whereas at high dynamic pressures,the fluid-structure interaction effect becomes the dominant factor.Notably,at the EP,asymmetric vibration transmittance is unaffected by the mass ratio of lossy resonators,which is attributed to the invariance of the operational deflection shapes of the NHMP at the EP.This study offers a novel perspective on panel aeroelastic systems and nonHermitian metamaterials,advancing the field through its comprehensive analyses.
基金financially supported by the National Natural Science Foundation of China (52474216 and 52374197)the Science&Technology Innovation Talents in Universities of Henan Province(22HASTIT027)the Scientific and Technological Key Project of Henan Province (222102320142)。
文摘To address the critical need for safer and cleaner explosion suppression technologies in industrial settings,the suppression differences and mechanisms of the flame acceleration characteristics of CH_(4),LPG and H_(2) explosions by N_(2)-water mist two-phase medium were investigated.The flame acceleration characteristics and suppression mechanism of methane,LPG and H_(2) explosions in N_(2)-water mist twophase medium were studied qualitatively and quantitatively from both experimental and simulation aspects.The experimental results show that compared with single N_(2) or water mist,the N_(2)-water mist two-phase medium is more effective in reducing the flame propagation speed and delaying the formation of flame hydrodynamic structure,thus slowing down the flame acceleration characteristics.The simulation results show that this two-phase medium exhibits a strong inhibitory effect on the thermal diffusion instability of CH_(4) and LPG,and significantly weakens the hydrodynamic instability of CH_(4),LPG,and H_(2) simultaneously.Mechanistic analysis confirms that the N_(2)-water mist two-phase medium has both chemical and physical inhibitory effects,among which the physical inhibition plays a dominant role.In addition,the study reveals a linear correlation between the concentration of H radicals in the three combustible gases and the laminar burning velocity.Moreover,this two-phase medium can significantly reduce the reaction rate of the H radical chain reaction,thereby effectively suppressing the laminar burning velocity.
基金This work was supported by the National Key R&D Program of China(Grant No.2022YFE0207000)the National Natural Science Foundation of China(Grant Nos.12372289,11972250,and 12102298)+1 种基金the China Postdoctoral Science Foundation(Grant No.2021M702443)Tianjin Natural Science Foundation(Grant No.22JCZDJC00910).
文摘At low-Reynolds-number,the performance of airfoil is known to be greatly affected by the formation and burst of a laminar separation bubble(LSB),which requires a more precise simulation of the delicate flow structures.A framework based on the interior penalty discontinuous Galerkin method and large eddy simulation approach was adopted in the present study.The performances of various subgrid models,including the Smagorinsky(SM)model,the dynamic Smagorinsky(DSM)model,the wall-adapting local-eddy-viscosity(WALE)model,and the VREMAN model,have been analyzed through flow simulations of the SD7003 airfoil at a Reynolds number of 60000.It turns out that the SM model fails to predict the emergence of LSB,even modified by the Van-Driest damping function.On the contrary,the best agreement is generally achieved by the WALE model in terms of flow separation,reattachment,and transition locations,together with the aerodynamic loads.Furthermore,the influence of numerical dissipation has also been discussed through the comparison of skin friction and resolved Reynolds stresses.As numerical dissipation decreases,the prediction accuracy of the WALE model degrades.Meanwhile,nonlinear variation could be observed from the performances of the DSM model,which could be attributed to the interaction between the numerical dissipation and the subgrid model.
基金supported by the Young Scientific and Technological Talents(Level Two)in Tianjin(No.QN20230214)Climbing Program of Tianjin University(No.2023XPD-0006)+1 种基金National Natural Science Foundation of China(No.52100156)National Engineering Research Center for Digital Construction and Evaluation Technology of Urban Rail Transit(No.2023HJ02)for the financial support。
文摘The type and quantity of active sites on a catalyst surface determine catalytic activity.In this study,machine learning was employed to assist in the construction of C=O and pyridine N active sites using sludge waste.Reactive descriptors,including C%,N%,O%,Fe%,pyrolysis temperature,heating rate,and pyrolysis time were proposed.Decision tree,extra tree,extreme gradient boosting(XGB),automatic relevance determination,and Bayesian ridge regression models were constructed and optimized.Among these,the XGB model was demonstrated with superior accuracy for prediction of C=O sites on the catalyst surface.Additionally,an ensemble model combining extra trees and XGB was developed to predict pyridine N,with R~2 value as high as 0.80 and minimum root mean square error(RMSE)of 0.1386.The ensemble model demonstrated a 17%improvement in accuracy compared to individual models.The model enables high-throughput screening of construction conditions for C=O and pyridine N.The study found that a pyrolysis temperature above of 500–800℃,a heating rate of 10–20℃/min,and a heating time of 120–200 min favor the generation of C=O active sites.For pyridine N sites,a pyrolysis temperature between 400℃ and 600℃,a heating rate of 5–10℃/min,and a pyrolysis time of around 150 min are optimal.Experimental validation demonstrated that both models exhibit excellent predictive performance,with prediction errors below 10%in all cases.This research provides a method to assist in the construction of C=O and pyridine N active sites,which is beneficial for guiding the design of sludge catalysts.
基金supported in part by the Key Research and Development Program of Shandong Province under Grant 2022KJHZ002.
文摘Driven by the global“dual-carbon”goals,hydrogen fuel cell electric vehicles(FCEVs)are being rapidly promoted as a zero-emission transportation solution.However,their large-scale application is constrained by issues such as inefficient operation,poor information flow between vehicles and stations,and potential safety hazards,which are caused by insufficient intelligence of hydrogen refueling stations.This study aims to address these problems by deeply integrating Cellular Vehicle-to-Everything(C-V2X)technology with hydrogen refueling stations,thereby building a safe,efficient,and low-carbon hydrogen energy application ecosystem to promote the global transition to zero-carbon transportation.Firstly,through literature review and technical analysis,this study expounds on the core technologies and process flows of current hydrogen refueling stations,aswell as the technical architecture and development evolution of C-V2X technology.Then,based on the analysis of relevant literature,it proposes a“vehicle-road-station-cloud”collaborative architecture that integrates C-V2X with hydrogen refueling stations.Combined with 5G communication and big data technologies,it elaborates on the implementation path for achieving real-time data interaction among hydrogen refueling stations,hydrogen-powered vehicles,and road infrastructure.This interconnection mode enables hydrogen refueling stations to obtain real-time information of surrounding vehicles,which plays an important role in building a safe,efficient,and low-carbon hydrogen energy application ecosystem and promoting the global transition to zero-carbon transportation.Finally,the future development prospects and potential of this scheme are put forward.
基金supported by the National Natural Science Foundation of China(Grant Nos.52105393,52305334,and U22A20186).
文摘A dislocation density-based crystal plasticity finite element(CPFE)model is developed to reveal the mechanism of discontinuous dynamic recrystallization(DDRX)of the TC17 dual-phase titanium alloy during hot deformation.The model incorporates the temperature and strain rate dependence of nucleation,growth and evolution during DDRX.The evolution of the dislocation densities in the matrix grains(MGs)and the recrystallized grains(RGs)is considered individually.The mechanical response and underlying microstructural evolution are systematically investigated by comparing the CPFE model predictions with experimental tests.The results indicate that at lower temperatures(700℃ and 800℃),TC17 titanium alloy exhibits a higher volume fraction of recrystallization and a notable drop in flow stress.As the temperature increases(900℃ and 1000℃),the volume fraction of recrystallization decreases,resulting in a weakened flow stress softening.The nucleation rate of DDRX increases with decreasing deformation temperature and increasing strain rate,while the size of RGs increases with higher temperature and lower strain rate.DDRX nuclei primarily occur at grain boundaries with high dislocation density.Furthermore,DDRX consumes a large number of dislocations and thus reduces the stress concentration and dislocation density at grain boundaries.This study provides a robust model that enhances the understanding of hot deformation mechanisms and informs the design of high-performance titanium alloys for future applications.
