FEM Simulations and Optimization about Residual Stresses in Coating Structures with Functionally Graded Materials Layer

An elasto-plastic finite element method is developed to predict the residual stresses of thermal spraying coatings with functionally graded material layer. In numerical simulations, temperature sensitivity of various material constants is included and mix

Work Softening And Annealing Hardening Of Deformed Nanocrystalline Nickel

We reported that work softening takes place during room-temperature rolling of nanocrystalline Ni at an equivalent strain of around 0.30. The work softening corresponds to a strain-induced phase transformation from a face-centered cubic (fcc) to a body-centered cubic (bcc) lattice. The hardness decreases with increasing volume fraction of the bcc phase. When the deformed samples are annealed at 423 K, a hardening of the samples takes place. This hardening by annealing can be attributed to a variety of factors including the recovery transformation from the bcc to the fcc phase, grain boundary relaxation, and retardation of dislocation gliding by microtwins.

Critical serrated flow features during nanoindentation in La-based bulk metallic glasses

La57.6Al17.5(Cu,Ni)(24.9) and La64Al14(Cu,Ni)(22) bulk metallic glasses (BMGs) were prepared by copper-mould casting method. Plastic deformation behavior of the two BMGs at various loading rates was studied by nanoindentation. The results showed that the La57.6Al17.5(Cu,Ni)(24.9) BMG with a glass transition temperature of 423 K exhibited prominent serrated flow at low loading rates, whereas less pronounced serrated flow at high rates during nanoindentation. In contrast, the La64Al14(Cu,Ni)(22) BMG with a glass transition temperature of 401 K exhibited prominent serrated flow at high loading rates. The different rate dependency of serrated flow in the two La-based BMGs is related to the different glass transition temperature, and consequently the degree of viscous flow during indentation at room temperature. A smoother flow occurs in the alloy with relatively lower glass transition temperature, due to the relaxation of stress concentration.

级联激波触发的太阳耀斑理论

<正> 随着观测特征不断积累和丰富,太阳耀斑的理论模型也越来越多。空间观测的结果似乎只要求活动区磁场是双极拱形,与大量的电流片模型不一致。耀斑过程可能并不总是一种机制。本文从理论上进一步讨论太阳耀斑的级联爆发模型。对流区的波动能量转换为活动区的横向磁场能量,由于扭转不稳定性使磁能释放,并转换为激波动能,活动区激发的级联

Fe基块体非晶合金在纳米压入过程中的变形行为

Fe基块体非晶合金具有极高的强度但通常表现出显著的宏观脆性,因此用常规拉伸、压缩等方法对这类合金的塑性变形行为和机理的研究具有很大困难.利用纳米压入和单轴压缩方法研究了Fe_(52)Cr_(15)Mo_9Er_3C_(15)B_6块体非晶合金的变形行为,考查了不同加载速率和不同晶化程度对变形行为和力学性能的影响,结果表明铸态和不同晶化程度样品在所研究的加载速率范围内的塑性变形过程中均未出现锯齿流变现象.用剪切带的时间和空间特性探讨了这种Fe基块体非晶合金在纳米压入过程中的特殊变形行为及其形成机制.

Multi-pipe string electromagnetic detection tool and its applications

The MID-K, a new kind of multi-pipe string detection tool is introduced. This tool provides a means of evaluating the condition of in-place pipe string, such as tubing and casino. It is capable of discriminating the defects of the inside and outside, and estimating the thickness of tubing and casing. It is accomplished by means of a low frequency eddy current to detect flaws on the inner surface and a magnetic flux leakage to inspect the full thickness. The measurement principle, the technology and applications are presented in this paper.

Coherent linking of periodic nano-ripples on a ZnO crystal surface induced by femtosecond laser pulses

We demonstrate the coherent linking of periodic nano-ripples formed on the surface of ZnO crystals induced by femtosecond laser pulses. By adjusting the distance between two laser scanning zones, the periodic nano-ripples induced by two separated laser writing processes can be coherently linked and the ZnO nanograting with much longer grooves is therefore produced. The length limitation of this kind of nanograting previously set by the laser focus size is thus overcome. The micro-Raman mapping technique is used to evaluate the quality of coherent linking, and the underlying physics is discussed. The demonstrated scheme is promising for producing large-size self-organized nanogratings induced by femtosecond laser pulses.

Effect of microcosmic optical parameters of dopants on the signal-to-noise ratio in doubly doped LiNbO3 crystals

We propose a united theory that describes the two-center recording system by taking scattering noise into account. The temporal evolution of the signal-to-noise ratio in doubly doped photorefractive crystals is described based on jointly solving material equations and coupled-wave equations with the fourth-order Runge-Kutta method. Roles of microcosmic optical parameters of dopants on the signal-to-noise ratio are discussed in detail. The theoretical results can confirm and predict experimental results. (c) 2005 Elsevier GmbH. All rights reserved.