To explore the influence of path deflection on crack propagation,a path planning algorithm is presented to calculate the crack growth *** fatigue crack growth life of metal matrix composites(MMCs)is estimated based on...
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To explore the influence of path deflection on crack propagation,a path planning algorithm is presented to calculate the crack growth *** fatigue crack growth life of metal matrix composites(MMCs)is estimated based on an improved Paris *** the different expansion coefficient of different materials,the unequal shrinkage will lead to residual stress when the composite is molded and *** crack growth model is improved by the modified stress ratio based on residual *** Dijkstra algorithm is introduced to avoid the cracks passing through the strengthening base and the characteristics of crack *** model can be extended to predict crack growth length for other similarly-structured composite *** shortest path of crack growth is simulated by using path planning algorithm,and the fatigue life of composites is calculated based on the shortest path and improved *** the residual stress caused by temperature change is considered to improve the fatigue crack growth model in the *** improved model can well predict the fatigue life curve of *** analyzing the fatigue life of composites,it is found that there is a certain regularity based on metal materials,and the new fatigue prediction model can also reflect this regularity.
Based on the system dynamic model, a full system dynamics estimation method is proposed for a chain shell magazine driven by a permanent magnet synchronous motor(PMSM). An adaptive extended state observer(AESO) is pro...
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Based on the system dynamic model, a full system dynamics estimation method is proposed for a chain shell magazine driven by a permanent magnet synchronous motor(PMSM). An adaptive extended state observer(AESO) is proposed to estimate the unmeasured states and disturbance, in which the model parameters are adjusted in real time. Theoretical analysis shows that the estimation errors of the disturbances and unmeasured states converge exponentially to zero, and the parameter estimation error can be obtained from the extended state. Then, based on the extended state of the AESO, a novel parameter estimation law is designed. Due to the convergence of AESO, the novel parameter estimation law is insensitive to controllers and excitation signal. Under persistent excitation(PE) condition, the estimated parameters will converge to a compact set around the actual parameter value. Without PE signal, the estimated parameters will converge to zero for the extended state. Simulation and experimental results show that the proposed method can accurately estimate the unmeasured states and disturbance of the chain shell magazine, and the estimated parameters will converge to the actual value without strictly continuous PE signals.
In the high-speed cold tandem rolling process of thin plate,chatter or slip instability gives rise to the deterioration of equipment and product *** instability behavior is closely related to interfacial friction-lubr...
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In the high-speed cold tandem rolling process of thin plate,chatter or slip instability gives rise to the deterioration of equipment and product *** instability behavior is closely related to interfacial friction-lubrication con-dition which is generally characterized by the friction ***,with higher and higher speed requirements,the commonly used model of friction coefficient is no longer applicable and accurate.A novel approach is suggested to calculate the speed-dependent friction coefficient,in which the viscosity-pressure-temperature effects of the lubricant,surface roughness states of work rolls and rolled piece are comprehensively involved and the mixed flm lubrication theory is ***,the influences of friction coefficient on the instability of slip and chatter are investigated for a five-stand cold tandem rolling *** one side,the critical friction coefficient for each stand is determined by calculating the corresponding slip factor;on the other hand,the friction coefficient varying with rolling speed is combined with the model of theoretical critical rolling speed presented under constant friction coefficient,so that the speed threshold is ***,the stable and unstable regions corresponding to the rear three stands are individually discussed,and the technical strategies are proposed to suppress both slip and chatter frequently occurring in the actual rolling process.
Experimental determination of heat generation rates is crucial in the thermal safety design of automotive batteries.A thermal protection method(TPM)is proposed to determine the heat generation rates of 18650 cylindric...
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Experimental determination of heat generation rates is crucial in the thermal safety design of automotive batteries.A thermal protection method(TPM)is proposed to determine the heat generation rates of 18650 cylindrical lithium-ion batteries under different discharge *** physical model based on the thermal protection method is established,and its feasibility is demonstrated through theoretical *** the experimental setup,by introducing lateral thermal protection batteries(TPB)to minimize the heat loss of the center test battery(CTB),heat generation rates of the battery can be obtained based on the temperature change of the *** average heat generation rates of the battery at 1,2,and 3 C discharge rates are found to be 0.255,0.844,and 1.811 W,respectively,which can be quadratically correlated with the discharge *** addition,a benchmark test of the present measurement against the commonly used accelerating rate calorimeter(ARC)was *** small deviations of 3.77%,4.20%,and 1.09%were identified in the heat generation rates for the discharge rates at 1,2,and 3 *** comparison with the ARC equipment,the present TPM can be more representative of the transient battery heat generation characteristics with a much shorter time for thermal ***,to further verify the accuracy of the present method,standard samples of the same size as the actual battery were made,which were capable of controlling heat generation through a direct current power supply.A comparison of the heat inputs of the standard sample with the heat generation rates measured by the thermal protection method shows a relative deviation of 1.01%*** high measurement accuracy and an easy-tobuild experimental setup,the proposed method has promising prospects in automotive applications.
Hydraulic-electric rock fragmentation(HERF)plays a significant role in improving the efficiency of high voltage pulse rock ***,the underlying mechanism of HERF remains *** this study,considering the heterogeneity of t...
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Hydraulic-electric rock fragmentation(HERF)plays a significant role in improving the efficiency of high voltage pulse rock ***,the underlying mechanism of HERF remains *** this study,considering the heterogeneity of the rock,microscopic thermodynamic properties,and shockwave time domain waveforms,based on the shockwave model,digital imaging technology and the discrete element method,the cyclic loading numerical simulations of HERF is achieved by coupling electrical,thermal,and solid mechanics under different formation temperatures,confining pressure,initial peak voltage,electrode bit diameter,and loading ***,the HERF discharge system is conducive to the laboratory experiments with various electrical parameters and the resulting broken pits are numerically reconstructed to obtain the geometric *** results show that,the completely broken area consists of powdery rock *** the pre-broken zone,the mineral cementation of the rock determines the transition of type CⅠcracks to type CⅡand type CⅢ***,the peak pressure of the shockwave increased with initial peak voltage but decreased with electrode bit diameter,while the wave front time ***,increasing well depth,formation temperature and confining pressure augment and inhibit HERF,but once confining pressure surpassed the threshold of 60 MPa for 152.40,215.90,and 228.60 mm electrode bits,and 40 MPa for 309.88 mm electrode bits,HERF is ***,for the same kind of rock,the volume and width of the broken pit increase with higher initial peak voltage and rock fissures will promote ***,the electrode drill bit with a 215.90 mm diameter is more suitable for drilling pink *** research contributes to a better microscopic understanding of HERF and provides valuable insights for electrode bit selection,as well as the optimization of circuit parameters for HERF technology.
The possibility of freely manipulating flow in accordance with humans will remain indispensable for breakthroughs in fields such as microfluidics,nanoengineering,and biomedicines,as well as for realizing zero-drag hyd...
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The possibility of freely manipulating flow in accordance with humans will remain indispensable for breakthroughs in fields such as microfluidics,nanoengineering,and biomedicines,as well as for realizing zero-drag hydrodynamics,which is essential for alleviating the global energy ***,persistent challenges arise from the D’Alembert paradox and the unresolved Navier-Stokes solutions,known as the Millennium *** obstacles also complicate the development of hydrodynamic zero-drag cloaks across diverse Reynolds *** research introduces a paradigm for such cloaks,relying exclusively on isotropic and homogeneous *** experimental and numerical validations,our cloaks exhibit zero-drag properties,effectively resolving the D’Alembert paradox in viscous potential ***,they possess the capability to activate or deactivate hydrodynamic concealment at *** analysis emphasizes the critical role of vorticity manipulation in realizing cloaking effects and drag-reduction ***,controlling vorticity emerges as a pivotal aspect for future active hydrodynamic zero-drag cloak *** conclusion,our study challenges the prevailing belief in the impossibility of zero drag,offering valuable insights into invisibility characteristics in fluid mechanics with implications for microfluidics,biofluidics demanding the drug release or biomolecules transportation accurately and timely,and hypervelocity technologies.
In this study,a novel multi-physics multi-scale model with the dilute multicomponent phase-field method in three-dimensional(3D)space was developed to investigate the complex microstructure evolu-tion in the molten po...
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In this study,a novel multi-physics multi-scale model with the dilute multicomponent phase-field method in three-dimensional(3D)space was developed to investigate the complex microstructure evolu-tion in the molten pool during laser welding of Al-Li *** accurately compute mass data within both two and three-dimensional computational domains,three efficient computing methods,including central processing unit parallel computing,adaptive mesh refinement,and moving-frame algorithm,were *** was placed on the distinctive equiaxed-to-columnar-to-equiaxed transition phenomenon that occurs during the entire solidification process of Al-Li alloy laser *** results indi-cated that the growth distance of columnar grains that epitaxially grew from the base metal(BM)de-creased as the nucleation rate *** the nucleation rate increased,the morphology of the newly formed grains near the fusion boundary(FB)changed from columnar to equiaxed,and newly formed equiaxed grains changed from having high-order dendrites to no obvious dendrite *** the nucleation rate was sufficiently high,non-dendritic equiaxed grains could directly form near the FB,and there was nearly no epitaxial growth from the ***,simulation results illustrated the com-petition among multiple grains with varying orientations that grow in 3D space near the ***,how equiaxed grain bands develop was *** equiaxed band not only hindered the growth of early columnar grains but also some of its grains could grow epitaxially to form new columnar *** predicted results were in good agreement with experimental measurements and observations.
The memory effect in a single-crystal spin glass (Cu0.92Mn0.08) has been measured using 1 Hz ac susceptibility techniques over a temperature range of 0.4–0.7Tg, and a model of the memory effect has been developed. A ...
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The memory effect in a single-crystal spin glass (Cu0.92Mn0.08) has been measured using 1 Hz ac susceptibility techniques over a temperature range of 0.4–0.7Tg, and a model of the memory effect has been developed. A double-waiting-time protocol is carried out where the spin glass is first allowed to age at a temperature below Tg, followed by a second aging at a lower temperature, Tw2, after it has fully rejuvenated. The model is based on calculating typical coincident growth of correlated regions at the two temperatures. It accounts for the absolute magnitude of the memory effect as a function of both waiting times and temperatures. The data can be explained by the memory loss being a function of the relative change in the correlated volume at the first waiting temperature because of the growth in the correlations at the second waiting temperature.
The simultaneous investigation on the parameters affecting the flow of electrically conductive fluids such as volumetric radiation,heat absorption,heat generation,and magnetic field(MF)is very vital due to its existen...
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The simultaneous investigation on the parameters affecting the flow of electrically conductive fluids such as volumetric radiation,heat absorption,heat generation,and magnetic field(MF)is very vital due to its existence in various sectors of industry and *** present research focuses on mathematical modeling to simulate the cooling of a hot component through power-law(PL)nanofluid convection *** temperature reduction of the hot component inside a two-dimensional(2D)inclined chamber with two different cold wall shapes is *** formulation of the problem is derived with the lattice Boltzmann method(LBM)by code writing via the FORTRAN *** variables such as the radiation parameter(0–1),the Hartmann number(0–75),the heat absorption/generation coefficient(−5–5),the fluid behavioral index(0.8–1.2),the Rayleigh number(103–105),the imposed MF angle(0°–90°),the chamber inclination angle(−90°–90°),and the cavity cold wall shape(smooth and curved)are *** findings indicate that the presence of radiation increases the mean Nusselt number value for the shear-thickening,Newtonian,and shear thinning fluids by about 6.2%,4%,and 2%,*** most cases,the presence of nanoparticles improves the heat transfer(HT)rate,especially in the cases where thermal conduction dominates *** is the lowest cooling performance index and MF effect for the cavity placed at an angle of 90°.The application in the design of electronic coolers and solar collectors is one of the practical cases of this numerical research.
In low-density steel,κ-carbides primarily precipitate in the form of nanoscale particles within austenite ***,their precipitation within ferrite matrix grains has not been comprehensively explored,and the second-phas...
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In low-density steel,κ-carbides primarily precipitate in the form of nanoscale particles within austenite ***,their precipitation within ferrite matrix grains has not been comprehensively explored,and the second-phase evolution mechanism during aging remains *** this study,the crystallographic characteristics and morphological evolution ofκ-carbides in Fe-28Mn-10Al-0.8C(wt%)low-density steel at different aging temperatures and times and the impacts of these changes on the steels’microhardness and properties were comprehensively *** different heat treatment conditions,intragranularκ-carbides exhibited various morpho-logical and crystallographic characteristics,such as acicular,spherical,and short rod-like *** the initial stage of aging,acicularκ-carbides primarily precipitated,accompanied by a few spherical carbides.κ-Carbides grew and coarsened with aging time,the spherical carbides were considerably reduced,and rod-like carbides *** hardness testing demonstrated that the material’s hardness was affected by the volume fraction,morphology,and size ofκ-*** aging at higher temperatures led to an increase in carbide size and volume fraction,resulting in a gradual rise in *** deformation,the primary mechanisms for strengthening were dislocation strengthening and second-phase *** on these findings,potential strategies for improving material strength are proposed.
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