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[Abstract](157) [FullText HTML](184) [PDF 1164KB](8)
Abstract:
The effect of stress concentration around the hole easily leads to fatigue failure of aircraft structures, and usually causes catastrophic accidents. In order to elucidate the influence of cold expansion on the fatigue life of AA2024-T351 specimens, fatigue tests of specimens before and after cold expansion were accomplished on high frequency fatigue test machine. Combining the finite element simulation with X-ray diffraction measurement, the evolution of residual stress around the hole was thus investigated. Meanwhile, scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to observe the fatigue fracture morphology, fatigue striation and microstructure characteristics, and to explore the influence of microstructure features on fatigue life. Research results show that the cold expansion with 0.4 mm can significantly improve the fatigue resistance of AA2024-T351 specimens, and the fatigue limit can be increased by about 42%.
[Abstract](72) [FullText HTML](49) [PDF 1178KB](5)
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The flap peening method with two different shot peening intensity was used to strength the 7B04-T6 for studying the effect of shot peeing on the stress corrosion cracking resistance andmechanical properties of 7B04-T6. Comparative testing about surface roughness, surface residual stress, surface topography, constant load stress corrosion cracking experiment and static strength tensile experiment were performed, the fracture surfaces were observed with SEM. The results show that, shot peening has imparted a surface residual compressive stress of −350 MPa (0.1-0.2 A intensity) and -275 MPa(0.2-0.3 A intensity). The surface roughness has increased from Ra 0.9 μm to Ra 1.6 μm (0.1-0.2 A intensity)and Ra 1.8 μm (0.2-0.3 A intensity). The duration of stress corrosion cracking has extended with 11.3 times (0.1-0.2 A intensity)and 8.7 times (0.2-0.3 A intensity) in the 3%NaCl + 0.5%H2O2 solution and with an application of 350 MPa load. Shot peening has not influenced the ultimate strength and percentage reduction in area, but slightly decreased the yield strength with a value of 15 MPa.
[Abstract](54) [FullText HTML](29) [PDF 924KB](0)
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[Abstract](55) [FullText HTML](38) [PDF 1212KB](2)
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In order to study the lightning damage characteristics of CFRP with fastener, this paper established a three-dimensional finite element model of CFRP with fastener and CFRP without fastener, and analyzed the lightning damage morphology of CFRP through electrothermal coupling simulation by finite element software. The lightning current damage test was carried out and the damage characteristics of two kinds of CFRP under different lightning current peaks were compared. The results show that when the peak value of lightning current is low, the surface damage degree of CFRP with fastener is lower than that of CFRP without fastener. As the peak value of the lightning current increases, the longitudinal damage of the CFRP with fasteners gradually increases along the carbon fiber, and eventually exceeds the CFRP without fasteners. The experimental results show that CFRP without fastener appears linear damage on the surface perpendicular to the direction of carbon fibers when lightning struck. The linear damage of CFRP with fastener on the surface perpendicular to the direction of carbon fibers is not obvious.
[Abstract](52) [FullText HTML](39) [PDF 718KB](2)
Abstract:
The matrix of fiber bundle composite C/SiC was modified by the combination means of precursor infiltration and pyrolysis (PIP) and chemical vapor infiltration (CVI). The microstructure of SiC matrix fabricated by PIP (PIP-SiC), and the fracture morphologies of the unmodified and modified composites were observed. Meanwhile, the tensile properties of the unmodified and modified composites were tested. The results show that PIP-SiC matrix modification improves the modulus matching between the fiber and matrix of C/SiC composite, and effectively improves the strength, toughness and stability of C/SiC composite. The tensile strength of modified C/SiC composite is slightly higher than that of unmodified C/SiC composite. Furthermore, the Weibull modulus, elongation and fracture work of modified C/SiC composite are 22%, 28% and 20% higher than those of unmodified C/SiC composite, respectively. Meanwhile, the variation coefficient (C.V.) of tensile strength, elongation and fracture work of modified C/SiC composite is 15%, 12% and 5% lower than that of unmodified C/SiC composite.
[Abstract](44) [FullText HTML](34) [PDF 796KB](0)
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Defect information obtained by non-destructive identification for more than four thousand composite components fabricated by convex mould in autoclave molding was statistically analyzed in this paper. The correlated rules between curvature radius of composite components and manufacturing defects were revealed. By self-designed solid pressure distribution testing method, the pressure distribution in the interface between flexible mould and rigid convex mould was also measured. Furthermore, combined with stress analysis in corner section and defect micrograph, the forming mechanism of defects was primarily analyzed. The process control measures to avoid manufacturing defects are given. The results indicate that the defect ratio and the size of delamination in corner section of composite components both decrease with increasing curvature radius of components. The thickness distribution near the corner shows that the thickness of the corner is thicker than the flat near after consolidation due to the interaction of shear flow, the percolation flow and the uniformity of pressure distribution.
[Abstract](67) [PDF 1479KB](3)
Abstract:
The evolution rule of γ′ phase in typical cross sections of DD6 single crystal superalloy turbine blade was investigated experimentally by SEM. The results show that to compare with the as-cast microstructures, the γ′ phase sizes of typical cross sections in the interdendrite regions of the heat-treated turbine blade are obviously refined, the γ′ phase sizes of the interdendritic (ID) region and dendritic core (DC) tended to be the same, and the γ′ phase size dispersion tended to decrease, the γ′ phases cubed degree increased. The sizes of as-cast and heat-treated γ′ phases in the dendrite core and interdendritec region of each cross section of the blade follow the normal distribution law. The size of γ′ phase in the section of the heat-treated blade is smaller than that of the tenon, and the size of the γ′ phase in the middle of the section is larger than that of the leading edge and trailing edge.
[Abstract](69) [FullText HTML](66) [PDF 1144KB](0)
Abstract:
In order to analyze the ablation damage law of composite laminates with fasteners subjected to the action of lightning current, the lightning finite element analysis model of fastener-containing laminates was constructed based on the principle of thermoelectric coupling, and the results of lightning ablation damage were analyzed and tested. The results compare the validity of the model. The ablation damage of fastener-containing laminates under different ratios of electrical conductivity, specific heat and thermal conductivity was analyzed. The variation of ablation damage area under different factors was summarized. The results show that the lightning ablation damage of the fastener-containing laminates compared with the fastener-free laminates is more threatening to the safety of civil aircraft. In addition, the electrical conductivity and specific heat of the laminate have a great influence on the ablation area of the laminate containing the fastener. When the two factors are reduced to 1/3, the ablation damage area increases by 211% and 229%, respectively, while the thermal conductivity of the laminate and the properties of the fastener have little effect on the ablation area.
[Abstract](49) [PDF 841KB](0)
Abstract:
In order to study the ablation damage law of composite laminates with fasteners under the action of lightning current, the lightning finite element analysis model of fastener-containing laminates was established based on thermoelectric coupling, and the results of lightning ablation damage were analyzed and tested. The results were compared with the validity of the model. The ablation damages of fastener-containing laminates under different peak currents, fastener sizes and laminate width ratios were analyzed, and the variations of ablation damage area under different factors were summarized. The results show that the peak current of the lightning strike, the size of the fastener, and the width of the laminate have great influences on the ablation damage areas of the fastener-containing laminates. The same lightning strike current waveform, the ablation damage area caused by lightning current with a peak value of 150 kA is 15.39 times that of 50 kA The smaller the fastener is, the larger the area of ablation damage is, and the larger the area of delamination damage is. Among them, when the diameter of the fastener is reduced by 2 times, the ablation damage area can be increased by 4.97 times, and the delamination damage area can be increased by 1.91 times. The damage area increases first and then decreases with the increase of the width, and finally tends to be stable. The ratio of the largest damage area to the minimum damage area can reach 1.81 times, and the ratio increases with the increase of the fastener diameter.
[Abstract](3696) [FullText HTML](1995) [PDF 1763KB](25)
Abstract:
The metal/ceramic laminated composites prepared from the unique "brick + mud" structure of biomimetic shells have been proved to have better strength and toughness, and have gradually become the research focus at domestic and abroad. In this paper, the current research of Al-based, Ti-based, Ni-based and other common metal/ceramic laminated composites is introduced, and the characteristic and process of each method are analyzed. The failure modes such as crack deflection, multiple crack propagation and crack bridging in metal/ceramic laminated composites are commonly summarized. The interface bonding strength of metal/ceramic laminated composites can be increased by controlling interfacial reactions and improving interfacial wettability. Optimizing of the preparation process and understanding the failure mechanism are the basis of engineering application of metal-ceramic layered composite materials. The introduction of the computational science into the research of metal/ceramic interface and damage mechanisms is an effective way to realize the controllability of the whole preparation process, and the realization of large size and diversified shape of products is the key to its large-scale application and promotion.
[Abstract](57) [PDF 1466KB](1)
Abstract:
In order to study the initiation, propagation and material failure behavior of T800 carbon fiber reinforced composite joint structure with countersunk bolt under load, the quasi-static tensile tests were carried out on the bolt joint structure. The three-dimensional finite element model of the structure was established by using the finite element software ABAQUS. The three-dimensional Hashin failure criterion was used to predict the initial failure of the composite. Based on the progressive damage theory, a new scheme of gradually reducing material stiffness after damage was proposed, and the definition of the material constitutive relation was realized by using the UMAT user subroutine. The numerical analysis of the joint structure of carbon fiber composite countersunk bolt was carried out, and the numerical calculation results were compared with the tensile test results. The results show that the prediction of failure process by the numerical analysis is in good agreement with the experimental results.
[Abstract](1) [PDF 1466KB](1)
Abstract:
In order to study the initiation, propagation and material failure behavior of T800 carbon fiber reinforced composite joint structure with countersunk bolt under load, the quasi-static tensile tests were carried out on the bolt joint structure. The three-dimensional finite element model of the structure was established by using the finite element software ABAQUS. The three-dimensional Hashin failure criterion was used to predict the initial failure of the composite. Based on the progressive damage theory, a new scheme of gradually reducing material stiffness after damage was proposed, and the definition of the material constitutive relation was realized by using the UMAT user subroutine. The numerical analysis of the joint structure of carbon fiber composite countersunk bolt was carried out, and the numerical calculation results were compared with the tensile test results. The results show that the prediction of failure process by the numerical analysis is in good agreement with the experimental results.
[Abstract](63) [PDF 740KB](6)
Abstract:
The effect of temperature on surface oxidation characteristics of nickel-base superalloy GH4169 powder was investigated by field emission scanning electron microscope (FE-SEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The results showed that the surface of the GH4169 superalloy powder was partially oxidized at room temperature (RT), and the surface consisted of metallic dominated by Ni, Cr, Ti, Nb, and hydroxide/oxide which was mainly composed of Ni(OH)2, Cr2O3, TiO2, Nb2O5. With the temperature increasing (150 ℃~250 ℃), the XPS peaks of Ni, Cr, Ti, Nb elements became weaker, the degree of oxidation was slightly increased and the surface of powder was partially oxidized. When the temperature reached 350 ℃, the XPS peaks of Ni, Cr, Ti, Nb elements almost disappeared and the surface of powder was fully oxidized. The oxide layer thickness was about 5 nm, which was mainly composed of Ni(OH)2, Cr2O3, TiO2, Nb2O5. The effect of temperature on oxidation characteristics of the GH4169 superalloy powder was significant, and the maximum treatment temperature of the GH4169 superalloy powder for the research was no more than 250 ℃ exposed to atmospheric conditions for 1 h.
[Abstract](1) [PDF 1164KB](0)
Abstract:
The effect of stress concentration around the hole easily leads to fatigue failure of aircraft structures, and usually causes catastrophic accidents. In order to elucidate the influence of cold expansion on the fatigue life of AA2024-T351 specimens, fatigue tests of specimens before and after cold expansion were accomplished on high frequency fatigue test machine. Combining the finite element simulation with X-ray diffraction measurement, the evolution of residual stress around the hole was thus investigated. Meanwhile, scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to observe the fatigue fracture morphology, fatigue striation and microstructure characteristics, and to explore the influence of microstructure features on fatigue life. Research results show that the cold expansion with 0.4 mm can significantly improve the fatigue resistance of AA2024-T351 specimens, and the fatigue limit can be increased by about 42%.
[Abstract](1) [PDF 1212KB](0)
Abstract:
In order to study the lightning damage characteristics of CFRP with fastener, this paper established a three-dimensional finite element model of CFRP with fastener and CFRP without fastener, and analyzed the lightning damage morphology of CFRP through electrothermal coupling simulation by finite element software. The lightning current damage test was carried out and the damage characteristics of two kinds of CFRP under different lightning current peaks were compared. The results show that when the peak value of lightning current is low, the surface damage degree of CFRP with fastener is lower than that of CFRP without fastener. As the peak value of the lightning current increases, the longitudinal damage of the CFRP with fasteners gradually increases along the carbon fiber, and eventually exceeds the CFRP without fasteners. The experimental results show that CFRP without fastener appears linear damage on the surface perpendicular to the direction of carbon fibers when lightning struck. The linear damage of CFRP with fastener on the surface perpendicular to the direction of carbon fibers is not obvious.
[Abstract](1) [PDF 718KB](0)
Abstract:
The matrix of fiber bundle composite C/SiC was modified by the combination means of precursor infiltration and pyrolysis (PIP) and chemical vapor infiltration (CVI). The microstructure of SiC matrix fabricated by PIP (PIP-SiC), and the fracture morphologies of the unmodified and modified composites were observed. Meanwhile, the tensile properties of the unmodified and modified composites were tested. The results show that PIP-SiC matrix modification improves the modulus matching between the fiber and matrix of C/SiC composite, and effectively improves the strength, toughness and stability of C/SiC composite. The tensile strength of modified C/SiC composite is slightly higher than that of unmodified C/SiC composite. Furthermore, the Weibull modulus, elongation and fracture work of modified C/SiC composite are 22%, 28% and 20% higher than those of unmodified C/SiC composite, respectively. Meanwhile, the variation coefficient (C.V.) of tensile strength, elongation and fracture work of modified C/SiC composite is 15%, 12% and 5% lower than that of unmodified C/SiC composite.
[Abstract](1) [PDF 1144KB](1)
Abstract:
In order to analyze the ablation damage law of composite laminates with fasteners subjected to the action of lightning current, the lightning finite element analysis model of fastener-containing laminates was constructed based on the principle of thermoelectric coupling, and the results of lightning ablation damage were analyzed and tested. The results compare the validity of the model. The ablation damage of fastener-containing laminates under different ratios of electrical conductivity, specific heat and thermal conductivity was analyzed. The variation of ablation damage area under different factors was summarized. The results show that the lightning ablation damage of the fastener-containing laminates compared with the fastener-free laminates is more threatening to the safety of civil aircraft. In addition, the electrical conductivity and specific heat of the laminate have a great influence on the ablation area of the laminate containing the fastener. When the two factors are reduced to 1/3, the ablation damage area increases by 211% and 229%, respectively, while the thermal conductivity of the laminate and the properties of the fastener have little effect on the ablation area.

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2020, 40(5): 0 -0
[Abstract](3143) [FullText HTML](2275) [PDF 2262KB](7)
Abstract:
2020, 40(5): 1 -12   doi: 10.11868/j.issn.1005-5053.2019.000143
[Abstract](4452) [FullText HTML](2186) [PDF 17485KB](11)
Abstract:
SiCf/SiC textile composites have enormous development potentials in the field of aerospace hot-end component owing to their strong structural design, low density, excellent mechanical properties, high-temperature resistance and oxidation resistance. However, there are few researches on the preparation technology, performance and meso-structure of SiCf/SiC textile composites. In the long run, it is still the research direction that must be carried out in country’s aviation engine manufacturing. In this paper, the research status of SiCf/SiC textile composites in recent years is introduced from three aspects: meso-scale structure, mechanical properties and numerical simulation. The research status of SiCf/SiC textile composites in recent years is summarized, and the basic research of domestic and foreign applications is comprehensively compared. Although the domestic preparation technology has made great progress and reached the international advanced level, it is still in its infancy in terms of component assessment and verification and application. Only by optimizing on the basis of the comprehensive balance of reliability, durability, process and performance, and realizing the synergy of materials and processes, structure and design, can breakthroughs be made in the future development of aeroengines.
2020, 40(5): 13 -19   doi: 10.11868/j.issn.1005-5053.2020.000015
[Abstract](3325) [FullText HTML](1753) [PDF 1086KB](7)
Abstract:
A Co-free Fe56.5Ni30Al10.5Nb3 (atom fraction/%) alloy was developed. In the preparation, the as-cast alloy was subjected to aging treatment at 650 ℃ and followed solution treatment directly. Scanning electron microscope (SEM) and X-ray diffractometer (XRD) were used to analyze the microstructure and phases of the alloy. At the same time, the hardness test, compressive strength test, superelasticity test and electron backscatter diffraction (EBSD) test were performed. The results show that, when the aging time range from 0 to 95 h, the alloy can exhibit superelasticity at room temperature with the maximum superelastic strain of 10.62%. There are nano-sized γ′ precipitates and fine β precipitates in the alloy. The γ′ phase is formed in the grain interiors and is most densely distributed when the aging time is 70 h. After the aging time exceeds 70 h, the γ′ phase enters the growth stage. The β phase can be formed both in the grain interiors and in the grain boundaries, and the amount of β precipitates increases with the aging time. The precipitation of the β phase can improve the hardness, but its formation in the grain boundaries is detrimental to the strength. With the increase of aging time, the hardness of the alloy increases continuously, and the compressive strength and superelastic strain first increase and then decrease, and reach the maximum value at the time of 70 h. The nano-sized γ′ precipitates and strong {100}<100> texture in the alloy have a great influence on its superelasticity.
2020, 40(5): 20 -28   doi: 10.11868/j.issn.1005-5053.2020.000083
[Abstract](9491) [FullText HTML](4451) [PDF 2864KB](19)
Abstract:
A uniform distribution of TiCp nanoparticles was realized in the TiCp/Mg-1.4Zn-2.6Ca-0.5Mn nanocomposite fabricated by the method of ultrasonic-assisted semisolid stirring. Microstructure and mechanical properties of the nanocomposite before and after extrusion were investigated. The results show that the grains in the dense area of the second phase were smaller than those in the barren area, and the second phase was Ca2Mg6Zn3. Dynamic recrystallization (DRX) occurred in the nanocomposites after extrusion at different temperatures (350 °C, 310 °C and 270 °C). Both the sizes and volume fraction of DRX grains and precipitates size were obviously refined as the extrusion temperature decreased, while the volume fraction of precipitates increased. Ultrafine recrystallized grain structure (≈0.34 μm) with a substantial of fine precipitates appeared in the nanocomposite extruded at 270 °C. The refined grain structure was not only due to DRX, but also the synergistic pinning effect of nano-TiCp, precipitated MgZn2 and α-Mn particles. The optimum tensile strength was achieved in the nanocomposites extruded at 270 °C/0.1 mm•s–1, and the yield strength (YS), ultimate tensile strength (UTS) and elongation to failure (EL)were ≈439.7 MPa、≈460.2 MPa and ≈1.73%, respectively. The grain refinement strengthening with the contribution ratio over 60% to YS increment was much higher relative to thermal expansion effect, Orowan strengthening and dislocation strengthening.
2020, 40(5): 29 -37   doi: 10.11868/j.issn.1005-5053.2019.000183
[Abstract](4281) [FullText HTML](2061) [PDF 1117KB](8)
Abstract:
The evolution of aging precipitation behavior and the formation of mechanical properties of X2A66 alloy under different aging heat treatment systems were investigated by using the experimental method combining mechanical properties test and microstructure observation. The research results indicate that the pre-stretching treatment before aging can accelerate the aging response rate of the alloy. In addition, while increasing the precipitation density of T1 phase, the diameter of T1 precipitate is decreased, but the thickness of T1 precipitate is not changed. With the increasing of pre-stretching, the strengthening effect of deformation dislocation increases gradually, and the strengthening effect of T1 phase precipitation decreases gradually. The pre-stretching of 5% can make the sample to obtain the best strong plastic ratio, and the yield strength, tensile strength and elongation rate are 593 MPa, 611 MPa and 10.7% respectively.
2020, 40(5): 38 -44   doi: 10.11868/j.issn.1005-5053.2020.000014
[Abstract](3070) [FullText HTML](1929) [PDF 1078KB](19)
Abstract:
DD15 single crystal superalloys with 9%Co and 12%Co were prepared in a directionally solidified furnace. By keeping the other alloying element contents unchanged, the influence of Co content on the microstructure, phase stability and stress rupture properties of the single crystal superalloy under the condition of 980 ℃/300 MPa was investigated. The results show that the primary dendrite arm spacing increases and the volume fraction of γ/γ′ eutectic decreases with increasing of Co content. The size of γ′ phase has no obvious change, its cubic shape turns a little irregular, its volume fraction decreases with increasing of Co content. The microstructure stability of the alloy increases with increasing of Co content. Increasing Co content decreases the stress rupture properties of the alloy.
2020, 40(5): 45 -52   doi: 10.11868/j.issn.1005-5053.2020.000111
[Abstract](3228) [FullText HTML](2029) [PDF 1032KB](267)
Abstract:
The effect of grain size and crystal orientation on the tensile deformation behavior of Ti-3Al-4.5V-5Mo titanium alloy was studied by using scanning electron scanning electron, X diffraction instrument and theoretical calculation. The results of tensile test of the wires in different states have verified that there are obvious macroscopic yield points on true stress-true strain curves of 720-840 ℃ annealing structures, and then a stress drop occurs. When the crystal orientation of α phase all shows <0001> fiber texture of different wires, the grain size determines the macroscopic yield stress of the wire. The larger the grain size is, the lower macroscopic yield stress is. Compared with <0001> fiber texture, the existence of <\begin{document}${10 \overline 10}$\end{document}> fiber texture of α phase generates larger plastic deformation in α phase, the internal stress in β phase, increased, and the macroscopic yield strength of the alloy decreased.
2020, 40(5): 53 -59   doi: 10.11868/j.issn.1005-5053.2020.000021
[Abstract](3321) [FullText HTML](1830) [PDF 868KB](7)
Abstract:
CoCrAlYSi-hBN coating was fabricated using the high-velocity oxygen fuel (HVOF) process under several processing conditions, and the effects of process parameters, gas flow and spray distance, on the microstructure and properties of the coating were investigated in the present paper. The microstructure, hardness, bonding strength and chemical composition of the coating was researched by using scanning electronmicroscopy (SEM), microhardness tester, adhesive strength measuring and energy dispersive spectroscopy (EDS). The results show that with the increasing gas flow, the porosity and h-BN content of the coating are reduced, and the hardness is improved; However, the bonding strength increases first and then decreases due to excessive energy leading serious oxidation. With the increase of spraying distance, the oxide inclusions are increased, which causes the hardness of coatings increase and the bonding strength decrease. In addition, when the spraying distance is 225 mm, the hardness and bonding strength of the coating are the highest due to the low porosity and boron nitride content.
2020, 40(5): 60 -69   doi: 10.11868/j.issn.1005-5053.2019.000174
[Abstract](3182) [FullText HTML](1903) [PDF 1013KB](4)
Abstract:
The effect of casting temperature and withdrawal rate on the interfacial reaction between DZ22B nickel-base superalloy and high-purity Al2O3 ceramic shell facecoat material was studied by changing the parameters of directional solidification process.The SLM was used to observe the different characteristic regions of the macroscopic reaction. The SEM analysis equipped with EDS was used to study the microstructure of the alloy-formed shell interface and the qualitative analysis of the interfacial reaction product elements. The phase and element valence of the interfacial reaction product were identified by XRD and XPS.The results show that the interface reaction products are mainly HfO2 and Al1.98Cr0.02O3 and exhibit a sub-regional distribution along the direction of directional solidification.Under the premise of ensuring the directionally solidified alloy structure, lowering the pouring temperature and increasing the withdrawal rate can inhibit the occurrence of delayed interface reaction.
2020, 40(5): 70 -79   doi: 10.11868/j.issn.1005-5053.2020.000029
[Abstract](3660) [FullText HTML](1723) [PDF 1386KB](7)
Abstract:
Carbon / epoxy composites are widely used in aviation due to their high strength, fatigue resistance and corrosion resistance. Aiming at the damage of carbon / epoxy composites during aircraft lightning strikes, a three-dimensional finite element model of carbon / epoxy composite laminates protected by copper mesh and aluminum mesh was established, and the lightning ablative element of composite structure was treated by element deletion method. The lightning protection effect of copper mesh and aluminum mesh was verified under different current peaks and different grid spacing, and the relationship between the weight change of the metal mesh and the lightning protection effect was studied. The test results show that the ablation area and damage depth of the composite laminate with metal mesh protection are significantly reduced. The denser the grid spacing is, the better the lightning protection effect is. The copper mesh composite laminate has better protection effect than the aluminum mesh. With the weight of the metal mesh increases, the degree of lightning damage to the composite laminate decreases.
2020, 40(5): 80 -87   doi: 10.11868/j.issn.1005-5053.2019.000138
[Abstract](3114) [FullText HTML](2032) [PDF 914KB](5)
Abstract:
The composites were separately prepared by a domestic T700-grade carbon fiber used for aviation and four types of bismaleimide resin. The composite laminates were treated by three hygrothermal conditions, including 100 ℃ boiling water, 70 ℃ water immersion and 70 ℃/85% relative humidity to study the hygrothermal mechanical properties of the composite laminates related to interface and matrix under ambient temperature and 150 ℃. The results show that the moisture absorption decreases the mechanical properties of composites, and the effect on mechanical properties under high temperature is significant. Furthermore, 90o tensile property, 0o compressive strength, flexural strength and open-hole compressive strength are sensitive to moisture absorption and temperature, while the sensitivities of 0o compressive modulus, flexural modulus and open-hole tensile strength are small. By comparing the changes of the mechanical properties of composite after different hygrothermal treatment conditions, it is found that the degree of degradation after 100 ℃ boiling water is larger, which is believed to be related to its higher equilibrium moisture absorption rate. Based on fracture morphology of composite after 90o tensile testing using scanning electron microscope, it is considered that the hygrothermal property of interface is the critical factor to determine the hygrothermal property of domestic carbon fiber composite.
2020, 40(5): 88 -95   doi: 10.11868/j.issn.1005-5053.2020.000087
[Abstract](3044) [FullText HTML](2152) [PDF 978KB](6)
Abstract:
Metallic-ceramic functionally graded materials have potential application value in the design of thermal barrier systems for aircraft panels due to their ultrahigh temperature resistant and high strength properties. In this article, the FGMs plate was used as the object to study the influence of parameters such as the volume fraction index, the geometric size of the plate and the thermal environment on the modal frequencies of a FGMs plate. Firstly, the power law distribution function was employed to discuss the influence of thermal environment on the physical properties of FGMs plates. Thereafter, the FGMs linear layered model dependent on temperature field was established by using the temperature continuously changing with the spatial position trait in the finite element, and the validity of this model in dynamic analysis was verified. Finally, the effects of ceramic volume fraction index, FGMs plate length-to-width ratio, temperature gradient and other variables on the modal frequencies of a FGMs plate were comprehensively analyzed and discussed. Results indicate that the higher order modes are mostly impacted by the uniform temperature field, while the linear and nonlinear temperature fields have the greatest impact on the first-order modes. In linear and nonlinear temperature fields, the volume fraction index is the most sensitive one to the effects of modal frequency drop ratio, while the modal frequency drop ratio is mainly affected by the coupling effect of the volume fraction index and the temperature gradient in uniform temperature field.
2020, 40(5): 96 -103   doi: 10.11868/j.issn.1005-5053.2020.000016
[Abstract](3142) [FullText HTML](1921) [PDF 702KB](13)
Abstract:
High cycle fatigue P-S-N curve of material are important for the design of aero-engine strength. Based on the data processing requirement of the high cycle fatigue of aero-engine materials, a novel data processing method has been developed by proposing the criterion of selecting fitting model and the method for determining the critical stress between the medium and high fatigue cycle regions. Furthermore, the testing data of two common Ti-alloy materials in aero-engine are used to validate the present batch processing method, and the P-S-N curves in various conditions have been obtained. And the comparison of the process time between the present method and the conventional method has been conducted finally. The results show that the present data processing method is suitable not only for the data processing of the traditional high cycle fatigue issues, but also for the data processing of very high cycle fatigue issues. And the efficiency of data processing is significantly improved.
1998, 18(4): 52-61
[Abstract](4435) [PDF 446KB](2151)
2000, 20(1): 46-54
[Abstract](3801) [PDF 1174KB](2050)
2006, 26(3): 283-288
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2000, 20(1): 55-61
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2000, 20(2): 55-63
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2002, 22(2): 49-53
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1998, 18(2): 53-62
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2009, 29(1): 1-6
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2006, 26(3): 148-151
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2002, 22(3): 59-62
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2010, 30(4): 92-96
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2006, 26(3): 244-250
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2000, 20(3): 172-177
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2001, 21(1): 55-62
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2006, 26(3): 226-232
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2006, 26(3): 238-243
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