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91.
A. M. Lokochtchenko 《Acta Mechanica Sinica》1991,7(2):157-161
In this paper the method of damage measurement of metal structure at the creep is proposed. In contrast to other methods,
it allows the measurement of this damage to be carried out in the process of creep test without unloading and cooling of specimens.
Experimental damage curves during creep are obtained as a result of test data processing by the suggested method. The analysis
of these curves leads to a conclusion that the material damage at repture is monotonically decreasing function of the applied
stress. This conclusion is an experimental verification of the theoretical result, obtained earlier.
Visiting scholar (1988–1989) at South China University of Technology 相似文献
92.
High-temperature mechanical behavior of ceramics is characterized by non-linear rate dependent responses, asymmetric behavior in tension and compression, and nucleation and coalescence of voids leading to rupture. Moreover, rupture experiments show considerable scatter or randomness in fatigue lives of nominally equal specimens. To capture the non-linear, asymmetric time-dependent behavior, a new non-linear viscoelastic model is proposed. Non-linearity and asymmetry are introduced in the volumetric component. To model the random formation and coalescence of voids, each element is assigned a failure strain sampled from a lognormal distribution. An element is deleted when its volumetric strain exceeds its failure strain. Temporal increases in strains produce a sequential loss of elements (a model for void nucleation and growth), which in turn leads to failure. Non-linear viscoelastic model parameters are determined from uniaxial tensile and compressive creep experiments on silicon nitride. The model is then used to predict the deformation of four-point bending and ball-on-ring specimens. Simulation is used to predict statistical moments of rupture lives. Numerical simulation results compare well with results of four-point bending experiments. 相似文献
93.
Xilian Wei Shizhou Fu Baolin Yin Dezhi Sun 《Journal of Dispersion Science and Technology》2013,34(4):525-529
Phase behavior of ternary systems containing 3‐dodecyloxy‐2‐hydroxypropyl trimethyl ammonium bromide (R12TAB), benzyl alcohol and water have been studied at 25±0.1°C. Ternary phase diagram of the systems shows a clear, isotropic, and low‐viscous region, a L phase, two liquid crystalline phases (lamella and hexagonal liquid crystal), and a coexisted phase of the liquid crystalline and micelles. 2H nuclear magnetic resonance (2H NMR) technology and polarizing‐light microscope were employed to confirm the symmetry structure of the liquid crystals and the boundaries for the different phases. In L phase, three types of different micelle regions (reverse micelles, normal micelles, and bicontinuous structures zones) were confirmed by means of the electric conductivity and the proton nuclear magnetic resonance spectroscopy (1H NMR) measurements. The microcosmic structures of the micelle were investigated, and the solubilizing position of benzyl alcohol were located according to the chemical shift of protons. 相似文献
94.
J. Gerstmayr H. J. Holl H. Irschik 《Archive of Applied Mechanics (Ingenieur Archiv)》2001,71(2-3):135-145
Summary A numerical algorithm for studying the development of plastic and damaged zones in a vibrating structural element with a
large, guided rigid-body motion is presented. Beam-type elements vibrating in the small-strain regime are considered. A machine
element performing rotatory motions, similar to an element of a slider-crank mechanism, is treated as a benchmark problem.
Microstructural changes in the deforming material are described by the mesolevel variables of plastic strain and damage, which
are consistently included into a macroscopic analysis of the overall beam motion. The method is based on an eigenstrain formulation,
considering plastic strain and damage to contribute to an eigenstrain loading of a linear elastic background structure. Rigid-body
coordinates are incorporated into this beam-type structural formulation, and an implicit numerical scheme is presented for
iterative computation of the eigenstrains from the mesolevel constitutive behavior. Owing to the eigenstrain formulation,
any of the existing constitutive models with internal variables could in principle be implemented. Linear elastic/perfectly
plastic behavior is exemplarily treated in a numerical study, where plastic strain is connected to the Kachanov damage parameter
by a simple damage law. Inelastic effects like plastic shakedown and damage-induced low-cycle rupture are shown to occur in
the examplary problems.
Received 1 September 1999; accepted for publication 9 March 2000 相似文献
95.
96.
J. M. Maia J. A. Covas J. M. Nbrega T. F. Dias F. E. Alves 《ournal of non Newtonian Fluid Mechanics》1999,80(2-3)
Knowledge of the extensional behaviour of polymer melts is extremely important due to the industrial relevance of extensional flows in common processing techniques and sequences such as blow moulding, film blowing, fibre spinning, melt flow through extrusion dies and injection mould filling. One of the main problems both researchers and industrialists come across is the fact that, unlike shear flows, steady-state extensional flows are not easy to generate and maintain experimentally. This fact limits the extent to which one can characterise the materials and, therefore, the degree of optimisation of the productive process. In this paper, a modification to a commercially available controlled rate rotational rheometer is proposed in order to produce a cheap, easy to set-up, flexible extensional rheometer. This is based on the well-known Meissner-type extensional rheometer and makes use of the accurate velocity control and torque measurement possibilities of the rotational apparatus. In this case, the adaptation was performed on a TA Instruments Weissenberg Rheogoniometer, but the idea is applicable to most other similar devices. The feasibility of the modification will be discussed and confirmed, results being presented for two materials at different temperatures. These include the calculation of transient uniaxial extensional viscosity and a study of rupture conditions. 相似文献
97.
纳米级零价铁的湿化学法制备及性能表征 总被引:1,自引:0,他引:1
采用湿化学法制备了纳米级零价铁,研究了湿法化学还原过程中工艺条件对产物的影响.对纳米级零价铁制备过程中物质微观结构随工艺条件的变化规律有了明确地认识.最终确认湿化学还原过程的最佳工艺条件是:在有机反应介质中,加入分散剂,以一定的滴加速度加入还原剂,同时在修饰剂的作用下得到产物,最终在合适的清洗制度下得到纳米零价铁. 相似文献
98.
微粒子观测相机调焦机构设计 总被引:1,自引:0,他引:1
为满足微粒子观测相机对光学系统的要求,提出了一种基于滚珠丝杆驱动的传动式调焦机构,介绍了其独特的直线运动结构形式。针对调焦机构承受的静载荷工况和温度工况,用有限元模拟法仿真分析了它的应力和变形情况,得到的最大静力变形为0.001 mm,最大热变形为0.002 mm。通过分析该结构各个传动件误差及装配误差,给出了结构总的理论相对误差值为2.2%。在样机的装调检测中实现了步进分辨率为0.005 mm,平均空回误差步距角为0.2个,完全可以满足整机对调焦机构的要求。 相似文献
99.
Laser Raman spectroscopy was used to investigate the microcosmic and photosensitive damage of YHPD to lysozyme, of which the three-dimensional structure has been elucidated. The experimental results shown by various damages of the main-chain and side-chain of lysozyme are as follows: (ⅰ) Phe and Cys are also damaged by photosensitization of YHPD, except for Trp, Tyr, Met, 1/2Cys and His; (ⅱ) the order of the photosensitized sensitivity of various groups of these amino acids have been described; (ⅲ) Trp and Tyr buried in the three-dimensional structure of the protein are damaged very greatly, and (ⅳ) the main-chain conformation of the protein has changed considerably, such as a decrease in orderly structure (α-helix, β-sheet and β-turn) and a simultaneous increase in random coil. 相似文献
100.
Fast and accurate determination of the relative binding affinities of small compounds to HIV‐1 protease using non‐equilibrium work 下载免费PDF全文
Son Tung Ngo Huynh Minh Hung Minh Tho Nguyen 《Journal of computational chemistry》2016,37(31):2734-2742
The fast pulling ligand (FPL) out of binding cavity using non‐equilibrium molecular dynamics (MD) simulations was demonstrated to be a rapid, accurate and low CPU demand method for the determination of the relative binding affinities of a large number of HIV‐1 protease (PR) inhibitors. In this approach, the ligand is pulled out of the binding cavity of the protein using external harmonic forces, and the work of pulling force corresponds to the relative binding affinity of HIV‐1 PR inhibitor. The correlation coefficient between the pulling work and the experimental binding free energy of shows that FPL results are in good agreement with experiment. It is thus easier to rank the binding affinities of HIV‐1 PR inhibitors, that have similar binding affinities because the mean error bar of pulling work amounts to . The nature of binding is discovered using the FPL approach. © 2016 Wiley Periodicals, Inc. 相似文献