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51.
Fracture analysis of plane piezoelectric/piezomagnetic multiphase composites under transient loading
R. Rojas-Díaz F. García-Sánchez A. Sáez E. Rodríguez-Mayorga Ch. Zhang 《Computer Methods in Applied Mechanics and Engineering》2011,200(45-46):2931-2942
The transient response of cracked composite materials made of piezoelectric and piezomagnetic phases, when subjected to in-plane magneto-electro-mechanical dynamic loads, is addressed in this paper by means of a mixed boundary element method (BEM) approach. Both the displacement and traction boundary integral equations (BIEs) are used to develop a single-domain formulation. The convolution integrals arising in the time-domain BEM are numerically computed by Lubich’s quadrature, which determines the integration weights from the Laplace transformed fundamental solution and a linear multistep method. The required Laplace-domain fundamental solution is derived by means of the Radon transform in the form of line integrals over a unit circumference. The singular and hypersingular BIEs are numerically evaluated in a precise and efficient manner by a regularization procedure based on a simple change of variable, as previously proposed by the authors for statics. Discontinuous quarter-point elements are used to properly capture the behavior of the extended crack opening displacements (ECOD) around the crack-tip and directly evaluate the field intensity factors (stress, electric displacement and magnetic induction intensity factors) from the computed nodal data. Numerical results are obtained to validate the formulation and illustrate its capabilities. The effect of the combined application of electric, magnetic and mechanical loads on the dynamic field intensity factors is analyzed in detail for several crack configurations under impact loading. 相似文献
52.
L. E. Evseeva V. Ch. Kruplevich A. I. Lesnikovich G. V. Printsev V. R. Sobol' S. A. Tanaeva 《Journal of Engineering Physics and Thermophysics》1991,61(3):1113-1116
Measurements have been made on the thermal conductivity and specific heat of the powder product from quenching in nitrogen applied to the gas-liquid flame formed by the combustion of a tetrazole-sodium tetrazolate mixture in weight proportion 31. The thermal conductivity on the whole is a nonmonotone function of temperature in the range 100–450 K and has some local turning points associated with the multicomponent structure and the phase transitions associated with chemical and structural transformations.Translated from Inzhenrno-fizicheskii Zhurnal, Vol. 61, No. 3, pp. 422–426, September, 1991. 相似文献
53.
Bovine immunoglobulins (IgG1 type) have been isolated from colostral whey. Hydrolysis by pronase, trypsin and (or) chymotrypsin yield several glycopeptides structural studies of which lead to the following results. 1. IgG1 colostral immunoglobulins possess two glycan moieties which are linked to the peptidic chain by an N-(beta-aspartyl)-N-acetylglucosaminylamine bound. 2. The peptidic sequence around the linkage region has been determined by classical methods and is as follows: Thr-Lys-Pro-Arg-Glu-Glu-Gln-Phe-Asn(Glycan)-Ser-Thr-Tyr-Arg. 3. The following procedures: partial acidic hydrolysis, periodic oxidation, hydrazinolysis-nitrous deamination, methylation and use of specific glycosidases allowed us to determine the structure of the glycan moieties which fit with the general following scheme: (see article) Thus they could be related to the general glycan structure so-called of "N-acetyllactosamine type" because they possess the pentasaccharidic core common to numerous glycoproteins Man alpha 1 leads to [Man alpha 1 leads to 6] Man beta 1 leads to 4 GlcNAc beta 1 leads to 4 GlcNAc beta 1 leads to Asn on which are conjugated 2 N-acetyllactosamine residues. Besides they present a microheterogeneity which is due to the varying number of additional N-acetylneuraminic acid and fucose residues. 4. These structures are compared to various immunoglobulin structures proposed by others: bovine serum IgG and human serum IgG, IgE and IgA. 相似文献
54.
A meshless method based on the local Petrov-Galerkin approach is proposed for the solution of quasi-static and transient dynamic
problems in two-dimensional (2-D) nonhomogeneous linear viscoelastic media. A unit step function is used as the test functions
in the local weak form. It is leading to local boundary integral equations (LBIEs) involving only a domain-integral in the
case of transient dynamic problems. The correspondence principle is applied to such nonhomogeneous linear viscoelastic solids
where relaxation moduli are separable in space and time variables. Then, the LBIEs are formulated for the Laplace-transformed
viscoelastic problem. The analyzed domain is covered by small subdomains with a simple geometry such as circles in 2-D problems.
The moving least squares (MLS) method is used for approximation of physical quantities in LBIEs. 相似文献
55.
为改善V2O5薄膜的电致变色性能,采用溶胶-凝胶法将具有高离子电导率并具有水溶性的聚环氧乙烷(PEO)直接嵌入V2O5层间,制备了PEO/V2O5纳米复合薄膜。采用标准三电极法从0.5mol/L LiClO4的PC电解质溶液向PEO/V2O5纳米复合薄膜注入锂离子,测量了纳米复合薄膜在注入不同数量锂离子时的可见光透射光谱以及对应的颜色变化,并运用循环伏安法测试其电化学性能。实验结果表明,PEO/V2O5纳米复合薄膜的循环伏安图出现了2对氧化还原峰,并且具有稳定的循环可逆性。随着应用电压的不同,薄膜呈现黄色、绿色和蓝色的多色可逆变化。PEO/V2O5纳米复合薄膜的电化学稳定性和机械性能都优于V2O5干凝胶薄膜,可以作为电致变色材料得到应用。X射线光电子能谱(XPS)成分分析表明PEO/V2O5纳米复合薄膜的电致变色效应与V、O的化合价和化学环境密切相关。 相似文献
56.
Ch. M. Gadzhiev 《Measurement Techniques》2006,49(4):357-366
A recurrent algorithm is derived for estimating the parameters of a calibration curve with allowance for the errors in reproducing
the inputs. That algorithm is combined with a proposed rule for halting the calibration to reduce considerably the length
of the calibration, which promises a real economic advantage.
__________
Translated from Izmeritel’naya Tekhnika, No. 4, pp. 32–38, April, 2006. 相似文献
57.
We propose a simple all-optical clock recovery technique for short data packets at 160 Gb/s, and beyond, which is based on the concept of using a Fabry-Peacuterot filter (FPF). The novel feature of the technique is the use of a highly nonlinear fiber followed by an optical bandpass filter, centered at the initial carrier wavelength, which acts as an ultrafast power limiter, removing drastically the amplitude modulation of the FPF's output and providing the clock signal 相似文献
58.
Carbon fibre reinforced ceramic matrix composites (CMC), originally developed for lightweight heat shields of spacecraft, are used for high performance brake discs in sports cars from different manufacturers. In contrast to the CMC materials for space applications, based on woven fabrics and costly manufacturing methods, these low cost friction materials are produced by liquid silicon infiltration of porous Carbon/Carbon (C/C) preforms, based on short fibre reinforced CFRP green bodies manufactured via warm press technique. In this work, different manufacturing methods for ventilated CMC brake discs are compared to each other, and the development of a new technology for the manufacture of single piece C/C‐SiC brake discs in net shape technique is presented. 相似文献
59.
The present paper aims to demonstrate that melt-flow during electron beam evaporation can be effectively controlled by using external magnetic fields to considerably reduce the convective heat transfer. We discuss the various effects of a static magnetic field, a static field combined with an applied electrical current, and a rotating magnetic field. We perform model experiments using GaInSn in eutectic composition as a test liquid. The liquid metal is heated locally at its free surface by an electric resistance heater. The results of the measurements are compared to prediction of numerical simulations. 相似文献
60.
Tensile tests were conducted at various temperatures (77 to 550 K) and strain rates (10−5 to 10−1 s−1) in order to study the effects of hydrogen on the ductility loss and the intergranular fracture of hydrogen-charged (32 wt
ppm) tensile specimens of alloy 600. The H-induced intergranular cracking was shown to require H segregation to grain boundaries
(GBs) during plastic deformation. The concordance between the temperature/strain rate domains, where H-induced intergranular
rupture of alloy 600 is observed and those of H transport by dislocations, is in favor of a major influence of this mechanism
of H transport on the intergranular rupture of H-charged alloy 600 in the 180 to 500 K temperature range. The possible contribution
of this mechanism to intergranular stress corrosion cracking (IGSCC) of alloy 600 in the pressurized water reactor (PWR) environment
is discussed. 相似文献