A big enough transverse magnetic field applied to soft magnetic ferrite toroid can magnetize the ferrite to a saturation level in transverse direction and almost completely suppresses magnetic domain structures in the...A big enough transverse magnetic field applied to soft magnetic ferrite toroid can magnetize the ferrite to a saturation level in transverse direction and almost completely suppresses magnetic domain structures in the ferrite,the response to the longitudinal alternating electromagnetic field changes from the original domain wall displacements and spin rotations to the precession of magnetization around the transverse field,and the hysteresis loss disappears in the ferrites.Both theoretical and experimental results indicate that the permeability and magnetic loss in the ferrite can be controlled by adjusting the transverse magnetic field.A higher Q value with relatively low permeability can be achieved by increasing the transverse field,which ensures that the ferrite can be operated at high frequencies,with magnetic loss being very low.展开更多
Since the discovery of high‐temperature superconductors(HTS),superconducting magnetic bearings(SMB)have attracted much attention for practical applications such as flywheel energy storage systems,electrical machines,...Since the discovery of high‐temperature superconductors(HTS),superconducting magnetic bearings(SMB)have attracted much attention for practical applications such as flywheel energy storage systems,electrical machines,gyroscopes,etc.,because of their ability to provide passive stable levitation under high‐load conditions.Despite providing contactless linear and rotational motion,SMBs gradually decelerate by AC losses mainly generated by magnetic field inhomogeneity.The main component of AC losses at low rotational speeds is hysteresis loss,which is said to be independent of rotational speed,intrinsic to HTS,and proportional to the cube of magnetic field inhomogeneity.Although the state‐of‐the‐art analytical expression of hysteresis loss in SMBs captures the general physics of the loss mechanism,it ignores the periodicity of the magnetic field in one complete rotation of the bearing.In this paper,the analytical expression of hysteresis loss is modified,taking into account the impact of magnetic field periodicity and the distribution of loss over the bearing surface.The new expression is tested by performing spin‐down experiments with magnets of different levels of inhomogeneity in an actual SMB environment.The impact of magnetic field inhomogeneity on the dynamic behaviour of the bearing is also investigated.The results show consistency between modified analytical calculations and experimental data.展开更多
A full-frequency instant core-loss equation built from the induction physical model of magnetic materials, where the iron loss, eddy loss, and hysteresis loss no longer have an integral term, and this new equation pro...A full-frequency instant core-loss equation built from the induction physical model of magnetic materials, where the iron loss, eddy loss, and hysteresis loss no longer have an integral term, and this new equation provides high simulation accuracy and performs dynamic core loss analysis on non-sinusoidal or pulse magnetic fields. The simulation examples use a high-grade electrical steel sheet 65CS400 by Epstein experimental data covering magnetic field 0.1 - 1.8 T and frequency 50 - 5000 Hz, and the average error of the simulated core loss is less than 4%. Since the simulation is converged by magnetic physical parameters, so the physical relevance of the similar laminated materials can be compared with the coefficient results. .展开更多
Despite growing interest in nano-sized fillers,micro-sized fillers with desired compatibility are still used for reinforcing rubbers,owing to their lower production cost and easier processing relative to nano-sized fi...Despite growing interest in nano-sized fillers,micro-sized fillers with desired compatibility are still used for reinforcing rubbers,owing to their lower production cost and easier processing relative to nano-sized fillers.Especially,the abundant and eco-friendly clay minerals are recognized as the materials of the twenty-first century.Herein,illite,a naturally occurring clay having dimension in micrometric scale,has been selected as filler to reinforce the SBR.To improve the compatibility of illite with SBR,the illite was modified by either bis[3-(triethoxysilyl)propyl]tetrasulfide(Si69-illite)or 3-mercaptopropyltriethoxysilane(KH580-illite).The interfacial interactions of SBR composites filled with pristine illite(illite/SBR)and Si69-illite(Si69-illite/SBR),or KH580-illite(KH580-illite/SBR)were characterized by bound rubber content and Payne effect measurements,while dynamic hysteresis losses of these uncured and cured composites were also analyzed under various strain amplitudes.It was found that the filler-rubber interactions were greatly improved for Si69-illite/SBR and KH580-illite/SBR systems compared to the illite/SBR composite.This leads to an increment of modulus at 300%strain of the composites from 3.46 MPa for illite/SBR to 7.70 MPa for Si69-illite/SBR and12.96 MPa for KH580-illite/SBR.Moreover,lower rolling resistance and better wear resistance without compromising wet traction of Si69-illite/SBR and KH580-illite/SBR have been achieved.This demonstrates the high possibility of Si69 and KH580 modified illites as promising alternative fillers for reinforcing rubbers.展开更多
Due to the influence of magnetic hysteresis and energy loss inherent in giant magnetostrictive materials （GMM）, output displacement accuracy of giant magnetostrictive actuator （GMA） can not meet the precision and ...Due to the influence of magnetic hysteresis and energy loss inherent in giant magnetostrictive materials （GMM）, output displacement accuracy of giant magnetostrictive actuator （GMA） can not meet the precision and ultra precision machining. Using a GMM rod as the core driving element, a GMA which may be used in the field of precision and ultra precision drive engineering is designed through modular design method. Based on the Armstrong theory and elastic Gibbs free energy theory, a nonlinear magnetostriction model which considers magnetic hysteresis and energy loss characteristics is established. Moreover, the mechanical system differential equation model for GMA is established by utilizing D＇Alembert＇s principle. Experimental results show that the model can preferably predict magnetization property, magnetic potential orientation, energy loss for GMM. It is also able to describe magnetostrictive elongation and output displacement of GMA. Research results will provide a theoretical basis for solving the dynamic magnetic hysteresis, energy loss and working precision for GMA fundamentally.展开更多
Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines.</span><span style="font-family:""> </span&g...Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">On the other hand, they are exposed to several risks and physical damages, since they are buried in the ground. Though the cables are armoured in order to provide mec</span><span style="font-family:Verdana;">hanical protection and achieve tensile strength, and also to provide effective conductance of earth fault currents.</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">The main purpose of this paper is to introduce insulated underground cables, armouring process, and to analyze the induced currents in metallic parts such as sheath and armour </span><span style="font-family:Verdana;">that causeohmic losses which are categorized mainly in two groups as circulating current and eddy current. This paper presents a review on analytical techniques used to analyze the effect of magnetic fields, andcalculate the losses in </span><span style="font-family:Verdana;">the armour of the cables,</span><span style="font-family:""> </span><span style="font-family:Verdana;">besides providing the strategies and solutions used for armour loss reduction.展开更多
Power loss of Fe-3%Sigrain-oriented silicon steelwas measured after ballscribing with different spacing using a self-designed tool.Three different sections of power loss,including hysteresis loss,abnormalloss,and eddy...Power loss of Fe-3%Sigrain-oriented silicon steelwas measured after ballscribing with different spacing using a self-designed tool.Three different sections of power loss,including hysteresis loss,abnormalloss,and eddy current loss,were measured and calculated,respectively.The loss variation and ratio were analyzed based on the experimentaldata.At 1.0 T,hysteresis loss of tested steelwith scribing spacing of 8 mm descends by 8.2% compared to samples without scribing,which is similar to the totalloss variation,and abnormalloss descends by 16.8%.At 1.0 T,hysteresis loss ratio of the steelwith scribing spacing of 16 mm ascends from 55.7% to 57.9%,and eddy current loss increases from 17.4% to 24.1%,while abnormalloss descends from 26.9% to 23.7%.The experimentalresults show that the reduction of power loss after scribing is mainly due to decreasing of hysteresis loss and abnormalloss.展开更多
Magnetic properties and magnetocaloric effects of La1-xRxFe11.5Si1.5 （R=Pr, （0 ≤ x ≤ 0.5）; R = Ce and Nd, （0 ≤ x ≤ 0.3）） compounds are investigated. Partially replacing La with R = Ce, Pr and Nd in La1-xRxFe...Magnetic properties and magnetocaloric effects of La1-xRxFe11.5Si1.5 （R=Pr, （0 ≤ x ≤ 0.5）; R = Ce and Nd, （0 ≤ x ≤ 0.3）） compounds are investigated. Partially replacing La with R = Ce, Pr and Nd in La1-xRxFe11.5Si1.5 leads to a reduction in Curie temperature due to the lattice contraction. The substitution of R for La causes an enhancement in field-induced itinerant electron metamagnetic transition, which leads to a remarkable increase in magnetic entropy change ASm and also in hysteresis loss. However, a high effective refrigerant capacity RCeff is still maintained in La1-xRxFe11.5Si1.5. In the present samples, a large △Sm and a high RCeff have been achieved simultaneously.展开更多
We have investigated the magnetic transition and magnetocaloric effects of Mn1＋xCo1-xGe alloys by tuning the ratio of Mn/Co. With increasing Mn content, a series of first-order magnetostructural transitions from ferr...We have investigated the magnetic transition and magnetocaloric effects of Mn1＋xCo1-xGe alloys by tuning the ratio of Mn/Co. With increasing Mn content, a series of first-order magnetostructural transitions from ferromagnetic to paramagnetic states with large changes of magnetization are observed at room temperature. Further increasing the content of Mn （x = 0.11） gives rise to a single second-order magnetic transition. Interestingly, large low-field magnetic entropy changes with almost zero magnetic hysteresis are observed in these alloys. The effects of Mn/Co ratio on magnetic transition and magnetocaloric effects are discussed in this paper.展开更多
Hysteresis loss is one of the electromagnetic characteristics controlled by time evolution of magnetic field and current distribution inside the conductor. Brandt＇s method allows us to model the interaction of the co...Hysteresis loss is one of the electromagnetic characteristics controlled by time evolution of magnetic field and current distribution inside the conductor. Brandt＇s method allows us to model the interaction of the conductor with an external magnetic field. Instead of the constant critical current density （Jc =CONST）, the Jc scaling law from current-voltage （I-V） measurement is used to model the magnetization loop. By comparing the calculated results with the measured data, it is shown that the Jc scaling law, i.e. the deviatoric strain model, is not useful in a very low field. To solve this problem, the Kim model about Jc as a function of applied field has been applied in the low field case. This method can be used to predict the hysteresis loss of Nb3Sn filamentary strand.展开更多
Eucommia ulmoides gum（EU gum）,known as gutta percha in Southeast Asia,is a natural polymer with double characteristics of rubber and plastic.In present paper,tanδ-T curve and hysteresis loss（HL） were chosen to ch...Eucommia ulmoides gum（EU gum）,known as gutta percha in Southeast Asia,is a natural polymer with double characteristics of rubber and plastic.In present paper,tanδ-T curve and hysteresis loss（HL） were chosen to characterize its damping property.The results indicated that its tanδvalue would increase with rising of temperature when T0℃and form another damping peak at 40-80℃besides T_g peak.This phenomenon resulted from meltage of crystals of EU gum could increase its damping property at ambient-high temperature.Its tanδvalue even exceeded those of conventional damping rubbers,such as nitrile-butadiene rubber（NBR） and chlorinated isobutene-isoprene rubber（CIIR）.展开更多
We investigated the magnetocaloric effect in commercial Er_(2)O_(3) powders which presents almost no hysteresis losses at low temperature.At a magnetic field change of 5 T,it displays large magnetic entropy change(-Δ...We investigated the magnetocaloric effect in commercial Er_(2)O_(3) powders which presents almost no hysteresis losses at low temperature.At a magnetic field change of 5 T,it displays large magnetic entropy change(-ΔSM)max of 15.02 J/(kg·K)and a refrigerant capacity(RC)of 311 J/K at Neel temperature TN=3.32 K.The magnetic transition was found to be of a second-order.The maximum values of adiabatic temperature change(ΔTad)max reach 0.70 K for a magnetic field change of 1 T.The large value,of(-ASM)max as well as no hysteresis loss,makes Er_(2)O_(3) a promising material as a magnetic refrigerant at low temperature.展开更多
A three-stage molding process involving microcellular injection molding with core retraction and an ＂out-of-mold＂ expansion was developed to manufacture thermoplastic polyurethane into lightweight foams of varying l...A three-stage molding process involving microcellular injection molding with core retraction and an ＂out-of-mold＂ expansion was developed to manufacture thermoplastic polyurethane into lightweight foams of varying local densities, microstructures, and mechanical properties in the same microcellular injection molded part. Two stages of cavity expansion through sequential core retractions and a third expansion in a separate mold at an elevated temperature were carried out. The densities varied from 0.25 to 0.42 g/cm3 （77% to 62% weight reduction）. The mechanical properties varied as well Cyclic com- pressive strengths and hysteresis loss ratios, together with the microstructures, were characterized and reported.展开更多
Pure phase Y_(3)Fe_(5)O_(12)(YIG)ceramic was successfully produced by tape-casting forming process and one-step solid-state sintering method.The activation energy for densification was calculated to be 183.81 kJ/mol.P...Pure phase Y_(3)Fe_(5)O_(12)(YIG)ceramic was successfully produced by tape-casting forming process and one-step solid-state sintering method.The activation energy for densification was calculated to be 183.81 kJ/mol.Pure YIG ceramic with a relative density as high as 99.8%was fabricated.The existence of O vacancy and Fe^(2+)ions was determined by XPS and EPR spectra.The RT saturation magnetization was measured to be 28.2 emu/g,and the hysteresis loss was calculated to be smaller than 10 mJ/kg in the temperature range of 230~360 K and be as high as 238.8 mJ/kg at 30 K.The dielectric loss tangent tanδ_(ε)was nearly zero at 6~7 GHz and 11~12 GHz.For complex permeability in the frequency range of 5~18 GHz,the magnetic loss tangent tanδ_(μ)fluctuated at around zero.Therefore,the low values of tanδ_(ε)and tanδ_(μ)indicate that it is a low loss ceramic material.展开更多
The aim of this research is to characterize the development of fatigue damage by means of stress-strain hysteresis.Experiments were conducted on 14 specimens made of cold-finished unannealed AISI 1018 steel.Results de...The aim of this research is to characterize the development of fatigue damage by means of stress-strain hysteresis.Experiments were conducted on 14 specimens made of cold-finished unannealed AISI 1018 steel.Results demonstrate that the mechanical hysteresis loop areas,when plotted as a function of the number of loading cycles,show significant variations and demonstrate the three principal stages concerning the progress of the fatigue failure—initial accommodation,accretion of damage and terminal failure.These three stages of fatigue are marked by the transitions at cycles N2 and N3.Experimental results show that although fatigue life Nf ranges from 2644 cycles to 108 992 cycles,the ratios of N2/Nf and N3/Nf tend to be stable:N2/Nf=10.7%,N3/Nf=91.3%.展开更多
The structure and magnetocaloric properties of La1–xCexFe11.44Si1.56 and their hydrides La1–xCexFe11.44Si1.56Hy（x=0, 0.1, 0.2, 0.3, 0.4） were investigated.The samples crystallized mainly in the cubic Na Zn13-type ...The structure and magnetocaloric properties of La1–xCexFe11.44Si1.56 and their hydrides La1–xCexFe11.44Si1.56Hy（x=0, 0.1, 0.2, 0.3, 0.4） were investigated.The samples crystallized mainly in the cubic Na Zn13-type structure with a small amount of α-Fe phase as impurity.The lattice constants and Curie temperature presented the same change tendency with increasing of Ce content.For the hydrides, the influence of Ce content on lattice constants was weakened and the values of H concentration y were approximate to be 1.56.The La1–xCexFe11.44Si1.56 compounds exhibited large values of isothermal entropy change –ΔSm around the Curie temperature TC under a low magnetic field change of 1.5 T.The value of –ΔSm increased and then decreased with increasing Ce content, reached the maximum, 26.07 J/kg·K for x=0.3.TC increased up to the vicinity of room temperature by hydrogen absorption for the Ce substituted compounds, but TC only slightly decreased with increasing Ce content.The first-order metamagnetic transition was still kept in the hydrides and the maximum values of –ΔSm were lower than those of the La1–xCexFe11.44Si1.56 compounds, but still remained large values, about 10.5 J/kg K under a magnetic field change of 1.5 T.The values of –ΔSm were nearly independent of the Ce content and did not increase with increasing x for the hydrides.The La1–xCexFe11.44Si1.56Hy（x=0–0.4） hydrides exhibited large magnetic entropy changes, small hysteresis loss and effective refrigerant capacity covered the room temperature range from 305 to 317 K.These hydrides are very useful for the magnetic refrigeration applications near room temperature under low magnetic field change.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2022YFB3504800 and 2021YFB3502400)the Key Research and Development Plan of Anhui Province,China(Grant No.202003c08020012)the Key Program of Education Department of Anhui Province,China(Grant No.KJ2019ZD03)。
文摘A big enough transverse magnetic field applied to soft magnetic ferrite toroid can magnetize the ferrite to a saturation level in transverse direction and almost completely suppresses magnetic domain structures in the ferrite,the response to the longitudinal alternating electromagnetic field changes from the original domain wall displacements and spin rotations to the precession of magnetization around the transverse field,and the hysteresis loss disappears in the ferrites.Both theoretical and experimental results indicate that the permeability and magnetic loss in the ferrite can be controlled by adjusting the transverse magnetic field.A higher Q value with relatively low permeability can be achieved by increasing the transverse field,which ensures that the ferrite can be operated at high frequencies,with magnetic loss being very low.
文摘Since the discovery of high‐temperature superconductors(HTS),superconducting magnetic bearings(SMB)have attracted much attention for practical applications such as flywheel energy storage systems,electrical machines,gyroscopes,etc.,because of their ability to provide passive stable levitation under high‐load conditions.Despite providing contactless linear and rotational motion,SMBs gradually decelerate by AC losses mainly generated by magnetic field inhomogeneity.The main component of AC losses at low rotational speeds is hysteresis loss,which is said to be independent of rotational speed,intrinsic to HTS,and proportional to the cube of magnetic field inhomogeneity.Although the state‐of‐the‐art analytical expression of hysteresis loss in SMBs captures the general physics of the loss mechanism,it ignores the periodicity of the magnetic field in one complete rotation of the bearing.In this paper,the analytical expression of hysteresis loss is modified,taking into account the impact of magnetic field periodicity and the distribution of loss over the bearing surface.The new expression is tested by performing spin‐down experiments with magnets of different levels of inhomogeneity in an actual SMB environment.The impact of magnetic field inhomogeneity on the dynamic behaviour of the bearing is also investigated.The results show consistency between modified analytical calculations and experimental data.
文摘A full-frequency instant core-loss equation built from the induction physical model of magnetic materials, where the iron loss, eddy loss, and hysteresis loss no longer have an integral term, and this new equation provides high simulation accuracy and performs dynamic core loss analysis on non-sinusoidal or pulse magnetic fields. The simulation examples use a high-grade electrical steel sheet 65CS400 by Epstein experimental data covering magnetic field 0.1 - 1.8 T and frequency 50 - 5000 Hz, and the average error of the simulated core loss is less than 4%. Since the simulation is converged by magnetic physical parameters, so the physical relevance of the similar laminated materials can be compared with the coefficient results. .
文摘Despite growing interest in nano-sized fillers,micro-sized fillers with desired compatibility are still used for reinforcing rubbers,owing to their lower production cost and easier processing relative to nano-sized fillers.Especially,the abundant and eco-friendly clay minerals are recognized as the materials of the twenty-first century.Herein,illite,a naturally occurring clay having dimension in micrometric scale,has been selected as filler to reinforce the SBR.To improve the compatibility of illite with SBR,the illite was modified by either bis[3-(triethoxysilyl)propyl]tetrasulfide(Si69-illite)or 3-mercaptopropyltriethoxysilane(KH580-illite).The interfacial interactions of SBR composites filled with pristine illite(illite/SBR)and Si69-illite(Si69-illite/SBR),or KH580-illite(KH580-illite/SBR)were characterized by bound rubber content and Payne effect measurements,while dynamic hysteresis losses of these uncured and cured composites were also analyzed under various strain amplitudes.It was found that the filler-rubber interactions were greatly improved for Si69-illite/SBR and KH580-illite/SBR systems compared to the illite/SBR composite.This leads to an increment of modulus at 300%strain of the composites from 3.46 MPa for illite/SBR to 7.70 MPa for Si69-illite/SBR and12.96 MPa for KH580-illite/SBR.Moreover,lower rolling resistance and better wear resistance without compromising wet traction of Si69-illite/SBR and KH580-illite/SBR have been achieved.This demonstrates the high possibility of Si69 and KH580 modified illites as promising alternative fillers for reinforcing rubbers.
基金Supported by National Natural Science Foundation of China(Grant No.51305277)Doctoral Program of Higher Education China(Grant No.20132102120007)+1 种基金Shenyang Science and Technology Plan Project(Grant No.F15-199-1-14)China Postdoctoral Science Foundation(Grant No.2014T70261)
文摘Due to the influence of magnetic hysteresis and energy loss inherent in giant magnetostrictive materials （GMM）, output displacement accuracy of giant magnetostrictive actuator （GMA） can not meet the precision and ultra precision machining. Using a GMM rod as the core driving element, a GMA which may be used in the field of precision and ultra precision drive engineering is designed through modular design method. Based on the Armstrong theory and elastic Gibbs free energy theory, a nonlinear magnetostriction model which considers magnetic hysteresis and energy loss characteristics is established. Moreover, the mechanical system differential equation model for GMA is established by utilizing D＇Alembert＇s principle. Experimental results show that the model can preferably predict magnetization property, magnetic potential orientation, energy loss for GMM. It is also able to describe magnetostrictive elongation and output displacement of GMA. Research results will provide a theoretical basis for solving the dynamic magnetic hysteresis, energy loss and working precision for GMA fundamentally.
文摘Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">On the other hand, they are exposed to several risks and physical damages, since they are buried in the ground. Though the cables are armoured in order to provide mec</span><span style="font-family:Verdana;">hanical protection and achieve tensile strength, and also to provide effective conductance of earth fault currents.</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">The main purpose of this paper is to introduce insulated underground cables, armouring process, and to analyze the induced currents in metallic parts such as sheath and armour </span><span style="font-family:Verdana;">that causeohmic losses which are categorized mainly in two groups as circulating current and eddy current. This paper presents a review on analytical techniques used to analyze the effect of magnetic fields, andcalculate the losses in </span><span style="font-family:Verdana;">the armour of the cables,</span><span style="font-family:""> </span><span style="font-family:Verdana;">besides providing the strategies and solutions used for armour loss reduction.
基金Funded by the National Natural Science Foundation of China(Nos.51174057 and 51404159)the National High Technology Research and Development Program(No.2012AA03A503)Research Fund for the Doctoral Program of Higher Education of China(No.20130042110040)
文摘Power loss of Fe-3%Sigrain-oriented silicon steelwas measured after ballscribing with different spacing using a self-designed tool.Three different sections of power loss,including hysteresis loss,abnormalloss,and eddy current loss,were measured and calculated,respectively.The loss variation and ratio were analyzed based on the experimentaldata.At 1.0 T,hysteresis loss of tested steelwith scribing spacing of 8 mm descends by 8.2% compared to samples without scribing,which is similar to the totalloss variation,and abnormalloss descends by 16.8%.At 1.0 T,hysteresis loss ratio of the steelwith scribing spacing of 16 mm ascends from 55.7% to 57.9%,and eddy current loss increases from 17.4% to 24.1%,while abnormalloss descends from 26.9% to 23.7%.The experimentalresults show that the reduction of power loss after scribing is mainly due to decreasing of hysteresis loss and abnormalloss.
基金supported by the National Basic Research Program of China(Grant No 2006CB601101)the National Natural Science Foundation of China(Grant Nos 50731007 and 50571112)the Knowledge Innovation Project of Chinese Academy of Sciences
文摘Magnetic properties and magnetocaloric effects of La1-xRxFe11.5Si1.5 （R=Pr, （0 ≤ x ≤ 0.5）; R = Ce and Nd, （0 ≤ x ≤ 0.3）） compounds are investigated. Partially replacing La with R = Ce, Pr and Nd in La1-xRxFe11.5Si1.5 leads to a reduction in Curie temperature due to the lattice contraction. The substitution of R for La causes an enhancement in field-induced itinerant electron metamagnetic transition, which leads to a remarkable increase in magnetic entropy change ASm and also in hysteresis loss. However, a high effective refrigerant capacity RCeff is still maintained in La1-xRxFe11.5Si1.5. In the present samples, a large △Sm and a high RCeff have been achieved simultaneously.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50701022,51001019,and 50831006)the Program for New Century Excellent Talents of China (Grant No. NCET-08-0278)
文摘We have investigated the magnetic transition and magnetocaloric effects of Mn1＋xCo1-xGe alloys by tuning the ratio of Mn/Co. With increasing Mn content, a series of first-order magnetostructural transitions from ferromagnetic to paramagnetic states with large changes of magnetization are observed at room temperature. Further increasing the content of Mn （x = 0.11） gives rise to a single second-order magnetic transition. Interestingly, large low-field magnetic entropy changes with almost zero magnetic hysteresis are observed in these alloys. The effects of Mn/Co ratio on magnetic transition and magnetocaloric effects are discussed in this paper.
基金Major State Basic Research Development Program of China(No.151J00035602)
文摘Hysteresis loss is one of the electromagnetic characteristics controlled by time evolution of magnetic field and current distribution inside the conductor. Brandt＇s method allows us to model the interaction of the conductor with an external magnetic field. Instead of the constant critical current density （Jc =CONST）, the Jc scaling law from current-voltage （I-V） measurement is used to model the magnetization loop. By comparing the calculated results with the measured data, it is shown that the Jc scaling law, i.e. the deviatoric strain model, is not useful in a very low field. To solve this problem, the Kim model about Jc as a function of applied field has been applied in the low field case. This method can be used to predict the hysteresis loss of Nb3Sn filamentary strand.
文摘Eucommia ulmoides gum（EU gum）,known as gutta percha in Southeast Asia,is a natural polymer with double characteristics of rubber and plastic.In present paper,tanδ-T curve and hysteresis loss（HL） were chosen to characterize its damping property.The results indicated that its tanδvalue would increase with rising of temperature when T0℃and form another damping peak at 40-80℃besides T_g peak.This phenomenon resulted from meltage of crystals of EU gum could increase its damping property at ambient-high temperature.Its tanδvalue even exceeded those of conventional damping rubbers,such as nitrile-butadiene rubber（NBR） and chlorinated isobutene-isoprene rubber（CIIR）.
文摘We investigated the magnetocaloric effect in commercial Er_(2)O_(3) powders which presents almost no hysteresis losses at low temperature.At a magnetic field change of 5 T,it displays large magnetic entropy change(-ΔSM)max of 15.02 J/(kg·K)and a refrigerant capacity(RC)of 311 J/K at Neel temperature TN=3.32 K.The magnetic transition was found to be of a second-order.The maximum values of adiabatic temperature change(ΔTad)max reach 0.70 K for a magnetic field change of 1 T.The large value,of(-ASM)max as well as no hysteresis loss,makes Er_(2)O_(3) a promising material as a magnetic refrigerant at low temperature.
文摘A three-stage molding process involving microcellular injection molding with core retraction and an ＂out-of-mold＂ expansion was developed to manufacture thermoplastic polyurethane into lightweight foams of varying local densities, microstructures, and mechanical properties in the same microcellular injection molded part. Two stages of cavity expansion through sequential core retractions and a third expansion in a separate mold at an elevated temperature were carried out. The densities varied from 0.25 to 0.42 g/cm3 （77% to 62% weight reduction）. The mechanical properties varied as well Cyclic com- pressive strengths and hysteresis loss ratios, together with the microstructures, were characterized and reported.
基金the National Key R&D Program of China(2017YFB0403200)the National Natural Science Foundation of China(No.51872327)。
文摘Pure phase Y_(3)Fe_(5)O_(12)(YIG)ceramic was successfully produced by tape-casting forming process and one-step solid-state sintering method.The activation energy for densification was calculated to be 183.81 kJ/mol.Pure YIG ceramic with a relative density as high as 99.8%was fabricated.The existence of O vacancy and Fe^(2+)ions was determined by XPS and EPR spectra.The RT saturation magnetization was measured to be 28.2 emu/g,and the hysteresis loss was calculated to be smaller than 10 mJ/kg in the temperature range of 230~360 K and be as high as 238.8 mJ/kg at 30 K.The dielectric loss tangent tanδ_(ε)was nearly zero at 6~7 GHz and 11~12 GHz.For complex permeability in the frequency range of 5~18 GHz,the magnetic loss tangent tanδ_(μ)fluctuated at around zero.Therefore,the low values of tanδ_(ε)and tanδ_(μ)indicate that it is a low loss ceramic material.
基金supported by the National Natural Science Foundation of China (No. 50901067)the Technological Research and Development Programs of the Ministry of Railways of China (No. 20101007-EG)the Julian S. SCHWINGER Foundation,USA
文摘The aim of this research is to characterize the development of fatigue damage by means of stress-strain hysteresis.Experiments were conducted on 14 specimens made of cold-finished unannealed AISI 1018 steel.Results demonstrate that the mechanical hysteresis loop areas,when plotted as a function of the number of loading cycles,show significant variations and demonstrate the three principal stages concerning the progress of the fatigue failure—initial accommodation,accretion of damage and terminal failure.These three stages of fatigue are marked by the transitions at cycles N2 and N3.Experimental results show that although fatigue life Nf ranges from 2644 cycles to 108 992 cycles,the ratios of N2/Nf and N3/Nf tend to be stable:N2/Nf=10.7%,N3/Nf=91.3%.
基金Project supported by National Natural Science Foundation of China(51261001)
文摘The structure and magnetocaloric properties of La1–xCexFe11.44Si1.56 and their hydrides La1–xCexFe11.44Si1.56Hy（x=0, 0.1, 0.2, 0.3, 0.4） were investigated.The samples crystallized mainly in the cubic Na Zn13-type structure with a small amount of α-Fe phase as impurity.The lattice constants and Curie temperature presented the same change tendency with increasing of Ce content.For the hydrides, the influence of Ce content on lattice constants was weakened and the values of H concentration y were approximate to be 1.56.The La1–xCexFe11.44Si1.56 compounds exhibited large values of isothermal entropy change –ΔSm around the Curie temperature TC under a low magnetic field change of 1.5 T.The value of –ΔSm increased and then decreased with increasing Ce content, reached the maximum, 26.07 J/kg·K for x=0.3.TC increased up to the vicinity of room temperature by hydrogen absorption for the Ce substituted compounds, but TC only slightly decreased with increasing Ce content.The first-order metamagnetic transition was still kept in the hydrides and the maximum values of –ΔSm were lower than those of the La1–xCexFe11.44Si1.56 compounds, but still remained large values, about 10.5 J/kg K under a magnetic field change of 1.5 T.The values of –ΔSm were nearly independent of the Ce content and did not increase with increasing x for the hydrides.The La1–xCexFe11.44Si1.56Hy（x=0–0.4） hydrides exhibited large magnetic entropy changes, small hysteresis loss and effective refrigerant capacity covered the room temperature range from 305 to 317 K.These hydrides are very useful for the magnetic refrigeration applications near room temperature under low magnetic field change.
