共查询到20条相似文献,搜索用时 31 毫秒
1.
Li Longbiao 《Applied Composite Materials》2017,24(5):1061-1088
In this paper, the synergistic effects of loading frequency and testing temperature on the fatigue damage evolution and life prediction of cross-ply SiC/MAS ceramic-matrix composite have been investigated. The damage parameters of the fatigue hysteresis modulus, fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of SiC/MAS composite. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S–N curves of SiC/MAS composite under the loading frequency of 1 and 10 Hz at 566 °C and 1093 °C in air condition have been predicted. The synergistic effects of the loading frequency and testing temperature on the degradation rate of fatigue hysteresis dissipated energy and the interface shear stress have been analyzed. 相似文献
2.
Li Longbiao 《Applied Composite Materials》2017,24(4):965-981
In this paper, the synergistic effects of temperature, oxidation and multicracking modes on damage evolution and life prediction in 2D woven ceramic-matrix composites (CMCs) have been investigated. The damage parameter of fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of CMCs. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperature, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composite fatigue fractures. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S–N curves of SiC/SiC at 1000, 1200 and 1300 °C in air and steam condition have been predicted. The synergistic effects of temperature, oxidation, fatigue peak stress, and multicracking modes on the evolution of interface shear stress and fatigue hysteresis dissipated energy versus cycle numbers curves have been analyzed. 相似文献
3.
Li Longbiao 《Applied Composite Materials》2016,23(3):357-374
The damage evolution of unidirectional C/SiC ceramic-matrix composite (CMC) under cyclic fatigue loading has been investigated using a hysteresis loss energy-based damage parameter at room and elevated temperatures. The experimental fatigue hysteresis modulus and fatigue hysteresis loss energy versus cycle number have been analyzed. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the interface shear stress corresponding to different cycle number and peak stress has been estimated. The experimental evolution of fatigue hysteresis loss energy and fatigue hysteresis loss energy-based damage parameter versus cycle number has been predicted for unidirectional C/SiC composite at room and elevated temperatures. The predicted results of interface shear stress degradation, stress–strain hysteresis loops corresponding to different number of applied cycles, fatigue hysteresis loss energy and fatigue hysteresis loss energy-based damage parameter as a functions of cycle number agreed with experimental data. It was found that the fatigue hysteresis energy-based parameter can be used to monitor the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs. 相似文献
4.
Li Longbiao 《Applied Composite Materials》2016,23(3):337-355
In this paper, the relationship between hysteresis dissipated energy and temperature rising of the external surface in fiber-reinforced ceramic-matrix composites (CMCs) during the application of cyclic loading has been analyzed. The temperature rise, which is caused by frictional slip of fibers within the composite, is related to the hysteresis dissipated energy. Based on the fatigue hysteresis theories considering fibers failure, the hysteresis dissipated energy and a hysteresis dissipated energy-based damage parameter changing with the increase of cycle number have been investigated. The relationship between the hysteresis dissipated energy, a hysteresis dissipated energy-based damage parameter and a temperature rise-based damage parameter have been established. The experimental temperature rise-based damage parameter of unidirectional, cross-ply and 2D woven CMCs corresponding to different fatigue peak stresses and cycle numbers have been predicted. It was found that the temperature rise-based parameter can be used to monitor the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs. 相似文献
5.
纤维增强陶瓷基复合材料(CMCs)在疲劳载荷作用下,纤维相对基体在界面脱粘区往复滑移导致其出现疲劳迟滞现象,迟滞回线包围的面积,即迟滞耗散能,可用于监测纤维增强CMCs疲劳损伤演化过程。提出了一种基于迟滞耗散能的纤维增强CMCs疲劳寿命预测方法及考虑纤维失效的迟滞回线模型,建立了迟滞耗散能、基于迟滞耗散能的损伤参数、应力-应变迟滞回线与疲劳损伤机制(多基体开裂、纤维/基体界面脱粘、界面磨损与纤维失效)之间的关系。分析了疲劳峰值应力、疲劳应力比与纤维体积分数对纤维增强CMCs疲劳寿命S-N曲线、迟滞耗散能和基于迟滞耗散能的损伤参数随循环次数变化的影响。疲劳寿命随疲劳峰值应力增加而减小,随纤维体积含量增加而增加;迟滞耗散能随疲劳峰值应力增加而增加,随应力比和纤维体积分数增加而减小;基于迟滞耗散能的损伤参数随纤维体积分数增加而减小。 相似文献
6.
Longbiao Li 《Applied Composite Materials》2016,23(1):1-27
When the fiber-reinforced ceramic-matrix composites (CMCs) are first loading to fatigue peak stress, matrix multicracking and fiber/matrix interface debonding occur. Under fatigue loading, the stress–strain hysteresis loops appear as fiber slipping relative to matrix in the interface debonded region upon unloading/reloading. Due to interface wear at room temperature or interface oxidation at elevated temperature, the interface shear stress degredes with increase of the number of applied cycles, leading to the evolution of the shape, location and area of stress–strain hysteresis loops. The evolution characteristics of fatigue hysteresis loss energy in different types of fiber-reinforced CMCs, i.e., unidirectional, cross-ply, 2D and 2.5D woven, have been investigated. The relationships between the fatigue hysteresis loss energy, stress–strain hysteresis loops, interface frictional slip, interface shear stress and interface radial thermal residual stress, matrix stochastic cracking and fatigue peak stress of fiber-reinforced CMCs have been established. 相似文献
7.
Brazing has been increasingly used to join metals to advanced ceramics. Brazing covalent materials requires either the use
of active filler alloys or the previous metallization of the surface. To that end, a new and simple mechanical technique has
been applied to metallize advanced ceramics, thus avoiding the use of costly Ti-based active filler alloys. The mechanical
metallization of Si3N4 with Ti was employed as an alternative route to deposit active metallic films prior to brazing with stainless steel using
72% Ag--28% Cu or 82% Au—18% Ni eutectic alloys. The brazing temperatures were set to 40°C or 75°C above the eutectic temperature
of each filler alloy. Ti-films of average thickness 4 μm produced adequate spreading of both filler alloys onto Si3N4 substrates, which were subsequently brazed to stainless steel. The interface of Si3N4/310 stainless steel basically consisted of a reaction layer, a precipitation zone and an eutectic microconstituent. Mechanically
sound and vacuum-tight joints were obtained, especially upon brazing at relatively lower temperatures. Increasing the brazing
temperature resulted in thermal cracking of the Si3N4, possibly due to increased thermal stress. 相似文献
8.
Yu. F. Kargin S. N. Ivicheva A. S. Lysenkov N. A. Ovsyannikov L. I. Shvorneva K. A. Solntsev 《Inorganic Materials》2012,48(9):897-902
Si3N4/TiN composites have been produced by hot pressing at temperatures from 1600 to 1800°C in a nitrogen atmosphere, using silicon nitride powders prepared by self-propagating high-temperature synthesis and surface-modified with titanium dioxide nanoparticles. We examined the effect of TiO2 content on the microstructure, phase composition, and mechanical strength of the ceramics. It is shown that titanium nitride can be formed by the reaction Si3N4 + TiO2 → TiN + NO + N2O + 3Si. The Si3N4/TiN composites containing 5–20% TiN have a low density, high porosity, and a bending strength of 60 MPa or lower. In Si3N4/TiN ceramics produced using calcium aluminates as sintering aids, the silicon nitride grains are densely packed, which ensures an increase in strength to 650 MPa. 相似文献
9.
Ceramic laminates with strong interfaces between layers are considered a very promising material for different engineering
applications because of the potential for increasing fracture toughness by designing high residual compressive and low residual
tensile stresses in separate layers. In this work, Si3N4/Si3N4-TiN ceramic laminates with strong interfaces were manufactured by rolling and hot pressing techniques. The investigation
of their mechanical properties has shown that the increase in apparent fracture toughness can be achieved for the Si3N4/Si3N4-20 wt.%TiN composite, while further increase of TiN content in the layers with residual tensile stresses lead to a formation
of multiple cracks, and as a result, a significant decrease in the mechanical performance of the composites. Micro-Raman spectroscopy
was used to measure the frequency shift across the Si3N4/Si3N4-20 wt.%TiN laminate. These preliminary Raman results can be useful for further analysis of residual stress distribution in
the laminate. 相似文献
10.
Ashok Kumar R. S. Katiyar Ramesh Nath Premnath Carlos Rinaldi J. F. Scott 《Journal of Materials Science》2009,44(19):5113-5119
Layered nanostructures (LNs) of the commercial ferroelectric Pb(Zr0.53Ti0.47)O3 (PZT) and the natural ferroic relaxor Pb(Fe0.66W0.33)O3 (PFW) were fabricated with a periodicity of PZT/PFW/PZT (~5/1/5 nm, thickness ~250 nm) on MgO substrates by pulsed laser
deposition. The dielectric behavior of these LNs were investigated over a wide range of temperatures and frequencies, observing
Debye-type relaxation with marked deviation at elevated temperatures (>400 K). High dielectric constant and very low dielectric
loss were observed below 100 kHz and 400 K, whereas the dielectric constant decreases and loss increases with increase in
frequency, similar to relaxor ferroelectrics. Asymmetric ferroelectric hysteresis loops across UP and DOWN electric field
were observed with high remanent polarization (Pr) of about 33 μC/cm2. High imprint (~5–7 V across 250 nm thin films) were seen in ferroelectric hysteresis that may be due to charge accumulation
at the interface of layers or significant amount of strain (~3.21) across the layers. Room temperature ferromagnetic hysteresis
was observed with remanent magnetization 5.32 emu/cc and a coercive field of ~550 Oe. Temperature and field dependent leakage
current densities showed very low leakage ~10−7–10−5 A/cm2 over 500 kV/cm. We observed imprint in hysteresis that may be due to charge accumulation at the interface of layers or active
role of polar nano regions (PNRs) situated in the PFW regions. 相似文献
11.
Meng Wang Jianjun Li Qiang Lei Jun Yu Wenli Zhou 《Journal of Materials Science: Materials in Electronics》2011,22(8):1033-1039
Ba0.6Sr0.4TiO3 films were fabricated by RF magnetron sputtering method. The X-ray diffraction (XRD) showed that the preferred orientation
of films growing on platinum Si substrates can be tailored by sputtering pressure. The processing parameters such as sputtering
pressure and substrate temperature were optimized to obtain a developed perovskite film with (110) preferred orientation.
The polarization hysteresis loops and permittivity–voltage curves of the (110)-oriented film have been investigated,which
demonstrated that the film is in ferroelectric phase at room temperature. Besides, it had excellent fatigue properties without
polarization reduction after about 1010 switch cycles, and showed low leakage current (10−9–10−7 A/cm2) within an applied voltage of 5 V. Finally, the leakage current mechanism was studied. 相似文献
12.
Rajat Kanti Paul Chi-Woo Lee Hai-Doo Kim Byong-Taek Lee 《Journal of Materials Science》2007,42(12):4701-4706
Porous Si3N4–Si2N2O bodies fabricated by multi-pass extrusion process were investigated depending on the feldspar addition content (4–8 wt% Si)
in the raw silicon powder. The diameter of the continuous pores was about 250 μm. The polycrystalline Si2N2O fibers observed in the continuous pores as well as in the matrix regions of the nitrided bodies can increase the filtration
efficiency. In the 4 wt% feldspar addition, the diameter of the Si2N2O fibers in the continuous pores of the nitrided bodies was about 90–150 nm. A few number of rope typed Si2N2O fibers (∼4 μm) was found in the case of 8 wt% feldspar addition. However, in the 8 wt% feldspar addition, the matrix showed
highly porous structure composed of large number of the Si2N2O fibers (∼60 nm). The relative densities of the Si3N4–Si2N2O bodies with 4 wt% and 8 wt% feldspar additions were about 65% and 61%, respectively. 相似文献
13.
E. Restrepo-Parra G. Orozco-Hernández J. Urrea-Serna J. F. Jurado J. C. Vargas-Hernández J. C. Riaño-Rojas J. Restrepo 《Journal of Materials Science》2010,45(24):6763-6768
A Monte Carlo simulation study of La2/3Ca1/3MnO3/La1/3Ca2/3MnO3 bilayers exchange bias (EB) properties by using a classical Heisenberg model and Monte Carlo method with Metropolis algorithm
is addressed. Samples were built atom-by-atom in order to resemble the real roughness. In this model, several contributions
included nearest neighbors exchange interactions; two different interface couplings, magnetocrystalline anisotropy and Zeeman
term, were considered. Here, an influence of the relaxation steps on the interface roughness is present. Our study focuses
on the influence of interface roughness on hysteresis loops, particularly EB field (H
ex) and coercive force (H
c). Results reveal that H
ex and H
c decrease as the interface roughness increases. 相似文献
14.
Qingyu Xu Zheng Wen Jinlong Gao Xiao Liu Di Wu Shaolong Tang Bin Yang 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1497-1500
(Bi0.9Ba0.1)(Fe0.95Mn0.05)O3 films were prepared on LaNiO3-coated surface oxidized Si substrates. XRD and Raman measurements confirm that the (Bi0.9Ba0.1)(Fe0.95Mn0.05)O3 film has pure R3c structure. Clear ferromagnetism with saturated magnetization of about 25 emu/cm3 has been observed at room temperature. The ferroelectric properties of the (Bi0.9Ba0.1)(Fe0.95Mn0.05)O3 film was confirmed by the observation of the ferroelectric domains and the converse piezoelectric coefficient d
33 versus applied voltage hysteresis loops by piezoelectric force microscopy (PFM). The observation of ferromagnetism and ferroelectricity
in (Bi0.9Ba0.1)(Fe0.95Mn0.05)O3 films indicates the potential multiferroic applications. 相似文献
15.
Silicon-nitride-based ceramics containing Al2O3-CaO sintering aids and reinforced with silicon carbide whiskers have been prepared by hot pressing at 1650°C in a nitrogen
atmosphere, and their microstructure, phase composition, and mechanical properties have been studied. The results indicate
that the Si3N4 ceramic containing 15 wt % calcium aluminate additions and 10 wt % SiC fibers has a dense microstructure with a uniform distribution
of skeletal and dendritic silicon carbide crystals. The observed variations in the morphology of the crystals are tentatively
attributed to the secondary crystallization of silicon carbide from the eutectic calcium aluminate melt during cooling. 相似文献
16.
Minxia Liu Lichun Yang Yongzhao Xu Geng Zhang Rui Zhang 《Journal of Superconductivity and Novel Magnetism》2016,29(10):2519-2522
The ternary compound Sc2Fe3Si5 has attracted much attention because of the various anomalous physical properties. The specific heat experiment and energy band structure calculation suggest that Sc2Fe3Si5 is a two-gap superconductor. Based on this, we analyze the upper critical field for superconducting Sc2Fe3Si5 crystals using the two-band Ginzburg-Landau theory. A two-parameter variational approach is adopted to obtain the upper critical field in arbitrary direction. The temperature and angular dependences of the upper critical field are plotted. The results reproduce the experimental data in a very broad temperature range and strongly support previous specific heat data and theoretical calculation, pointing to the existence of two energy gaps in Sc2Fe3Si5. The anisotropy of the upper critical field is also studied and is about 2, in accordance with the experimental result. Moreover our calculations indicate that Sc2Fe3Si5 has rather a three-dimension character, in agreement with the energy band calculation. 相似文献
17.
The M23C6 precipitation behavior in a cast Ni-base superalloy M963 was investigated after tensile creep testing at 800°C and strain-controlled low cycle fatigue testing at 700–950°C. During high temperature creep and low cycle fatigue, the primary MC decomposed into M6C continuously, and a great amount of secondary carbide, chromium-rich M23C6, precipitated preferentially in the periphery of MC and γ +γ′ eutectic at grain boundaries. M23C6 was rarely present in grain interior, indicating that grain boundary promoted M23C6 carbide precipitation. The M23C6 precipitation was closely dependent on the stress state and testing temperature, seemed to be independent of the total strain amplitude. M23C6 is unstable during low cycle fatigue testing. The occurrence of M23C6 precipitation was sharply reduced during low cycle fatigue testing at 950°C. Crack was easily initiated at interface between MC and matrix, while fine M23C6 was effective to prevent grain boundary migration. 相似文献
18.
An Al2O3/5 vol.% mullite composite was synthesized by using reaction sintering of Al2O3/0.78 wt.% SiC at 1,600 °C for 2 h in air. The phase analysis of the Al2O3/mullite composite was carried out using X-ray diffraction (XRD). There were two kinds of mullite in alumina/mullite composite,
namely, 3Al2O3·2SiO2 and Al5.65Si0.35O9.175. The microstructure of the Al2O3/mullite composite was investigated using scanning electron microscope (SEM) and transmission electron microscope (TEM). The
mechanical properties such as Young’s modulus, Poisson’s ratio, hardness, toughness and strength of the Al2O3/mullite composite were investigated. The influence of mullite on the composite is discussed. 相似文献
19.
S. Manjura Hoque M. A. Hakim F. A. Khan N. H. Dan 《Journal of Materials Science》2007,42(22):9415-9420
Tb-substituted (Nd,Tb)2Fe14B/Fe3B nanocomposite ribbons have been synthesized by melt spinning of Nd3Tb1Fe76Cu0.5Nb1B18.5 alloys. Tb substitution has significantly enhanced the value of coercivity and Curie temperature. Highest value of coercivity
has been obtained as 4.76 kOe for the sample annealed at 953 K for 10 min. Curie temperature of Tb substituted sample, Nd3Tb1Fe76Cu0.5Nb1B18.5 is 549 K while Curie temperature of the sample without Tb, Nd4Fe76Cu0.5Nb1B18.5 is 535 K. Recoil hysteresis loops measured along the major demagnetization curve are steep having small recoil loop area.
Temperature dependence of coercivity, remanent ratio and maximum energy product have been measured for the sample annealed
at 893 K and 923 K for 10 min. At 5 K, coercivity and maximum energy product of the sample annealed at 893 K for 10 min are
5.2 kOe and 11.5 MGOe respectively and the sample annealed at 923 K for 10 min are 6 kOe and 13.1 MGOe respectively. 相似文献
20.
Fine Ti5Si3 powder has been mechanochemically synthesized from a mixture of elemental Ti and Si powders. When Ti5Si3 is added as a catalyst into Li3AlH6, it shows a good catalytic ability by reducing the decomposition temperature and improving the decomposition kinetics as
well. Although its catalytic effect is not as good as well-known TiCl3, the use of Ti5Si3 has a benefit of releasing more hydrogen than TiCl3 during dehydrogenation. This can be explained by that Ti5Si3, unlike TiCl3, does not incur any chemical reactions with Li3AlH6 and thus remains inert during milling for dispersion. 相似文献