NiTiNb shape memory alloys have attracted much attention in pipe coupling or sealing system because of their large transformation hysteresis upon a proper pre-deformation. In order to clarify the effects of adding Nb ...NiTiNb shape memory alloys have attracted much attention in pipe coupling or sealing system because of their large transformation hysteresis upon a proper pre-deformation. In order to clarify the effects of adding Nb on the mechanical properties as well as the transformation behavior of NiTiNb shape memory alloys, Ni47Ti44Nb9 and Ni49.8Ti45.2Nb5 alloys with different microstructures but with similar martensitic transformation start temperature, are prepared. Comparative studies on the microstructures, mechanical proPerties and transformation characteristics are conducted by means of scanning electron microscopy （SEM）, phase transformation measurements and mechanical property tests. It is found that Nia7Ti44Nb9 and Ni49.8Ti45.2Nb5 alloys possess similar transformation hysteresis in the as-annealed state. However, the presence of Nb and its status exerts important effects on the mechanical properties, especially the yield strength and the yield behavior of the alloys. Ni49.8Ti45.2Nb5 alloy exhibits remarkable increase in the yield strength than the Ni47Ti44Nb9 alloy. The transformation hysteresis of both alloys under pre-deformation is characterized and the relative mechanism is discussed.展开更多
为满足桥梁在正常使用荷载与地震极端荷载等不同工况下的性能需求,该文设计制作了一种新型多功能隔震支座,基于ANSYS有限元平台,建立了该支座的精细有限元模型,对其力学性能进行了数值模拟与试验验证。数值结果表明:在350 k N竖向压力...为满足桥梁在正常使用荷载与地震极端荷载等不同工况下的性能需求,该文设计制作了一种新型多功能隔震支座,基于ANSYS有限元平台,建立了该支座的精细有限元模型,对其力学性能进行了数值模拟与试验验证。数值结果表明:在350 k N竖向压力作用下,部分铅芯已进入塑性状态,橡胶则处于三向受力状态,其静水压力远大于Mises应力;在100 mm横向剪切位移作用下,单层橡胶片各处剪切应力仍近似相等,相差不超过5%,铅芯则发生了很大的塑性应变,最大Mises塑性应变值达到0.580。数值计算结果与该支座试验数据对比表明,支座数值计算所得剪切性能滞回曲线与试验结果一致性较好,验证了该文数值模拟的准确性与可靠性。展开更多
The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations.Methods for solving the contradiction between improving reinforcement and redu...The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations.Methods for solving the contradiction between improving reinforcement and reducing energy dissipation for rubber nanocomposites have not been well developed.Herein carbon black(CB)filled isoprene rubber(IR)/liquid isoprene rubber(LR)blend nanocomposites with similar crosslink density(ve)are prepared and influence of LR on the strain softening behaviors including Payne effect under large amplitude shear deformation and Mullins effect under cyclic uniaxial deformation is investigated.The introduction of LR could improve the frequency sensitivity of loss modulus and reduce critical strain amplitude for Payne effect and loss modulus at the low amplitudes.Meanwhile,tuning ve and LR content allows reducing mechanical hysteresis in Mullins effect without significant impact on the mechanical performances.The investigation is illuminating for manufacturing nanocomposite vulcanizates with balanced mechanical hysteresis and reinforcement effect.展开更多
（MnFe）2（P, Si）-type compounds are, to date, one of the best candidates for magnetic refrigeration and energy conversion applications due to the combination of giant magnetocaloric effect （MCE）, tunable working t...（MnFe）2（P, Si）-type compounds are, to date, one of the best candidates for magnetic refrigeration and energy conversion applications due to the combination of giant magnetocaloric effect （MCE）, tunable working temperature range and low material cost. The giant MCE in the （Mn, Fe）2（P, Si）-type compounds originates from strong mag- netoelastic coupling, where the lattice degrees of freedom and spin degrees of freedom are efficiently coupled. The tunability of the phase transition, in terms of the critical temperature and the character of the phase transition, is essentially attributed to the changes in the magnetoelastic coupling in the （Mn, Fe）2（P, Si）-type compounds. In this review, not only the fundamentals of the magnetoelastic coupling but also the related practical aspects such as magnetocaloric performance, hysteresis issue and mechanical stability are discussed for the （Mn, Fe）2（P, Si）- type compounds. Additionally, some future fundamental studies on the MCE as well as possible ways of solving the hysteresis and fracture issues are proposed.展开更多
N2 and N3 are known as the transition points of the three principal stages of fatigue: initial accommodation, accretion of damage and terminal fatigue. Many experiments show that the ratios of N2/Nf and N3/Nf tend to ...N2 and N3 are known as the transition points of the three principal stages of fatigue: initial accommodation, accretion of damage and terminal fatigue. Many experiments show that the ratios of N2/Nf and N3/Nf tend to be stable even though the specific N2 and N3 values may fluctuate widely. The primary goal of this research is to study the piezomagnetic field surrounding AISI 1018 steel specimen under repeated loads and to find the ratio values of N2/Nf and N3/Nf by analyzing 11 sets of low-cycle fatigue data. An MTS-810 testing system with a peak capacity of 222 kN was used to obtain the data which consisted of stress, strain, and piezomagnetic field. A computer program was constructed to track the evolution of the piezomagnetic field and re- gression analysis was carried out to determine N2 and N3 values. It was observed that there exists a consistent relationship between N2 and Nf. The apparent invariance of the ratio N2/Nf implies that N2 may be identified as an index of performance in the early loading response of a specimen that forecasts its fatigue life, Nf. It has been demonstrated that measurements of the magnetic and mechanical hysteresis can yield significant insights into the various stages of the development of a fatigue critical microstructure which culminates in complete rupture of the material.展开更多
基金Foundation items： National Natural Science Foundation of China （50971009） National High-Tech Research and Development Program of China （2006 AA03Z102） Aeronautical Science Foundation of China （2009ZF51059）
文摘NiTiNb shape memory alloys have attracted much attention in pipe coupling or sealing system because of their large transformation hysteresis upon a proper pre-deformation. In order to clarify the effects of adding Nb on the mechanical properties as well as the transformation behavior of NiTiNb shape memory alloys, Ni47Ti44Nb9 and Ni49.8Ti45.2Nb5 alloys with different microstructures but with similar martensitic transformation start temperature, are prepared. Comparative studies on the microstructures, mechanical proPerties and transformation characteristics are conducted by means of scanning electron microscopy （SEM）, phase transformation measurements and mechanical property tests. It is found that Nia7Ti44Nb9 and Ni49.8Ti45.2Nb5 alloys possess similar transformation hysteresis in the as-annealed state. However, the presence of Nb and its status exerts important effects on the mechanical properties, especially the yield strength and the yield behavior of the alloys. Ni49.8Ti45.2Nb5 alloy exhibits remarkable increase in the yield strength than the Ni47Ti44Nb9 alloy. The transformation hysteresis of both alloys under pre-deformation is characterized and the relative mechanism is discussed.
文摘为满足桥梁在正常使用荷载与地震极端荷载等不同工况下的性能需求,该文设计制作了一种新型多功能隔震支座,基于ANSYS有限元平台,建立了该支座的精细有限元模型,对其力学性能进行了数值模拟与试验验证。数值结果表明:在350 k N竖向压力作用下,部分铅芯已进入塑性状态,橡胶则处于三向受力状态,其静水压力远大于Mises应力;在100 mm横向剪切位移作用下,单层橡胶片各处剪切应力仍近似相等,相差不超过5%,铅芯则发生了很大的塑性应变,最大Mises塑性应变值达到0.580。数值计算结果与该支座试验数据对比表明,支座数值计算所得剪切性能滞回曲线与试验结果一致性较好,验证了该文数值模拟的准确性与可靠性。
基金the National Natural Science Foundation of China(Nos.U1908221,51873190 and 51790503)the Fundamental Research Funds for the Central Universities(No.2020XZZX002-08).
文摘The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations.Methods for solving the contradiction between improving reinforcement and reducing energy dissipation for rubber nanocomposites have not been well developed.Herein carbon black(CB)filled isoprene rubber(IR)/liquid isoprene rubber(LR)blend nanocomposites with similar crosslink density(ve)are prepared and influence of LR on the strain softening behaviors including Payne effect under large amplitude shear deformation and Mullins effect under cyclic uniaxial deformation is investigated.The introduction of LR could improve the frequency sensitivity of loss modulus and reduce critical strain amplitude for Payne effect and loss modulus at the low amplitudes.Meanwhile,tuning ve and LR content allows reducing mechanical hysteresis in Mullins effect without significant impact on the mechanical performances.The investigation is illuminating for manufacturing nanocomposite vulcanizates with balanced mechanical hysteresis and reinforcement effect.
基金financially supported by the Key Research & Development Program of Jiangsu Province(No.BE2017102)
文摘（MnFe）2（P, Si）-type compounds are, to date, one of the best candidates for magnetic refrigeration and energy conversion applications due to the combination of giant magnetocaloric effect （MCE）, tunable working temperature range and low material cost. The giant MCE in the （Mn, Fe）2（P, Si）-type compounds originates from strong mag- netoelastic coupling, where the lattice degrees of freedom and spin degrees of freedom are efficiently coupled. The tunability of the phase transition, in terms of the critical temperature and the character of the phase transition, is essentially attributed to the changes in the magnetoelastic coupling in the （Mn, Fe）2（P, Si）-type compounds. In this review, not only the fundamentals of the magnetoelastic coupling but also the related practical aspects such as magnetocaloric performance, hysteresis issue and mechanical stability are discussed for the （Mn, Fe）2（P, Si）- type compounds. Additionally, some future fundamental studies on the MCE as well as possible ways of solving the hysteresis and fracture issues are proposed.
基金Project supported by the National Natural Science Foundation of China (No. 50901067)the Technological Research and Development Programs of the Ministry of Railways (No. 2010G007-E), China
文摘N2 and N3 are known as the transition points of the three principal stages of fatigue: initial accommodation, accretion of damage and terminal fatigue. Many experiments show that the ratios of N2/Nf and N3/Nf tend to be stable even though the specific N2 and N3 values may fluctuate widely. The primary goal of this research is to study the piezomagnetic field surrounding AISI 1018 steel specimen under repeated loads and to find the ratio values of N2/Nf and N3/Nf by analyzing 11 sets of low-cycle fatigue data. An MTS-810 testing system with a peak capacity of 222 kN was used to obtain the data which consisted of stress, strain, and piezomagnetic field. A computer program was constructed to track the evolution of the piezomagnetic field and re- gression analysis was carried out to determine N2 and N3 values. It was observed that there exists a consistent relationship between N2 and Nf. The apparent invariance of the ratio N2/Nf implies that N2 may be identified as an index of performance in the early loading response of a specimen that forecasts its fatigue life, Nf. It has been demonstrated that measurements of the magnetic and mechanical hysteresis can yield significant insights into the various stages of the development of a fatigue critical microstructure which culminates in complete rupture of the material.
