To improve the hardness, fracture toughness, and overall mechanical properties of 3Y-TZP ceramics, Al2O3 whiskers were introduced as reinforcing phases. Composite ceramics containing 0.5, 1.0, 1.5, and 2.0 wt% Al2O3 w...
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Silicon carbide fiber reinforced silicon carbide ceramic matrix composites (CMC-SiCf/SiC) have been widely used in aerospace and other fields due to their excellent properties such as high hardness, oxidation resistan...
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A triaxial active control magnetic bearing with an axially asymmetric structure has been developed for a high-temperature turbomachinery. Since this magnetic bearing has a support force interference, disturbance suppr...
A triaxial active control magnetic bearing with an axially asymmetric structure has been developed for a high-temperature turbomachinery. Since this magnetic bearing has a support force interference, disturbance suppression was not possible. A nonlinear compensator has already been proposed to solve this problem. However, the disturbance suppression performance is insufficient. Therefore, this paper proposes a switching type disturbance suppression control system that estimates a disturbance from the states and switches the controller characteristics based on an estimated disturbance. This model improves the disturbance observer performance of the already proposed a variable structure type nonlinear control system. First, the characteristics of the proposed model are presented, followed by the disturbance estimation performance of the proposed model. Next, the disturbance suppression performance of the proposed model and a conventional compensator is compared. The results verify the superiority of the proposed model over conventional compensators.
High-quality crystalline copper gallate (CuGa2O4) thin films were grown on c-plane sapphire substrates using the pulsed laser deposition (PLD) technique by optimizing the growth parameters (i.e., temperature, oxygen c...
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Multi-component alloys have been confirmed to be excellent reinforcing phases in high-entropy alloy-based composite. However, achieving a balance between strength and ductility by controlling the reinforcement content...
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This paper presents a new approach to acquiring in-plane solutions for the stress singularities at internal junctions where multiple elastic isotropic materials meet, and then establishing the correlation between the ...
This paper presents a new approach to acquiring in-plane solutions for the stress singularities at internal junctions where multiple elastic isotropic materials meet, and then establishing the correlation between the singular stress field and the failure of electronic package structures. Extensive analyses have been conducted on the order of the stress singularities in relation to the material properties and interface angles, which address an important yet controversial issue regarding the utilization of the stress singularity for electronic package reliability assessment. The results obtained through calculating the stress singularity orders are further validated using finite element analyses. The basic findings indicate that the analyses of the singularity order can serve as an initial approach to evaluate structural design and system reliability. However, relying solely on the calculations of the stress singularity order is insufficient when exploring the variations in material parameters. Despite that, the calculations of the order of stress singularity still provide valuable guidance for electronic package design and help develop more robust and reliable packaging solutions for integrated circuit devices.
The study examines the evolution of dislocation structures in pure nickel with specific orientations near [100], [110], and [111]. The dislocation evolution pathways of grains with different orientations in both surfa...
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Due to its excellent corrosion and oxidation resistance, good formability, and affordability, 316L stainless steel (SS) is widely used in industries such as biomedical, marine, chemical, and water treatment. To furthe...
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To elucidate the mechanisms of regulating the microstructure uniformity in 7050 aluminum forgings through surface cumulative plastic deformation(SCPD),the microstructure under different solution treatments was investi...
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To elucidate the mechanisms of regulating the microstructure uniformity in 7050 aluminum forgings through surface cumulative plastic deformation(SCPD),the microstructure under different solution treatments was investigated using metallographic observation(OM),electron backscatter diffraction(EBSD),transmission electron microscopy(TEM),and X-ray diffraction(XRD).The findings demonstrate that the most uniform microstructure in the forgings is achieved with a solution treatment at 470℃for 30 *** SCPD process generates a significant number of needle-shaped precipitates,resulting in a higher dislocation density and stored *** treatments alleviate the pinning effect of second-phase particles and facilitate static recrystallization(SRX)in forgings,leading to a reduction in grain ***,mechanical testing results demonstrate 7%−13%increase in tensile strength and more uniform elongation of the forgings in different directions.
Epoxy resin-based composite panels used for armors may be subjected to a wide range of operating temperatures (-55℃ to 76℃) and high strain rates on the order of 103-104 s-1. Over the life cycle, various environment...
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ISBN:
(纸本)9781713837596
Epoxy resin-based composite panels used for armors may be subjected to a wide range of operating temperatures (-55℃ to 76℃) and high strain rates on the order of 103-104 s-1. Over the life cycle, various environmental factors also affect the resin properties and hence influence the performance of the composites. Therefore, it is critical to determine the stress-strain behavior of the epoxy resin over a wide range of strain rates and temperatures for accurate multi-scale modeling of composites and to investigate the influence of environmental aging on the resin properties. Additionally, the characterization of key mechanical properties such as yield stress, modulus, and energy absorption (i.e. area under the stress-strain curve) at varying temperatures and moisture can provide critical data to calculate the material operating limits. In this study, we characterize mechanical properties of neat epoxy resin, SC-15 (currently used in structural armor) and RDL-RDC using uniaxial compression testing. RDL-RDC, developed by Huntsman Corporation, has a glass transition temperature of ~ 120℃, compared to ~ 85℃ of SC-15. A split Hopkinson pressure bar is used for high strain rate testing. Quasistatic testing is conducted using a screw-driven testing machine (Instron 4484) at 10-3 s-1 and 10-1 s-1 strain rates and varying temperatures. The yield stress is fit to a modified Eyring model over the varying strain rates at room temperature. For rapid investigation of resistance to environmental aging, accelerated aging tests are conducted by immersing the specimens in 100℃ water for 48 hours. Specimens are conditioned in an environmental chamber at 76 ℃ and 88% RH until they reach equilibrium. Tests are then conducted at five different temperatures from 0℃ to 95℃, and key mechanical properties are then plotted vs. temperature. The results presented are an important step towards developing a methodology to identify environmental operating conditions for composite ground vehicle appli
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