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961.
E. M. CASTRODEZA J. E. PEREZ IPI
A F. L. BASTIAN 《Fatigue & Fracture of Engineering Materials & Structures》2002,25(11):999-1008
ABSTRACT The aim of this work is to propose procedures for the measurement of the fracture toughness of fibre metal laminates (FMLs) reinforced with unidirectional fibres of aramid or glass. Experimental techniques for fracture toughness evaluation by using Compact (C(T)) and Single‐Edge Bend (SE(B)) specimens obeying ASTM standards are introduced. Procedures from the standard for thick metallic materials were modified in order to overcome problems, which can arise when testing FMLs – that is, specimen buckling, indentations and crack growth in planes other than the plane of the fatigue pre‐crack or notch. The methodology proposed was experimentally tested leading to satisfactory results. 相似文献
962.
本文对低碳钢微型试样在扫描电镜装置上所作的动态拉伸观测结果进行的分析表明:物理屈服现象的产生具有尺寸效应,即当试样厚度减至与晶粒尺寸相当时,物理屈服不再出现。表现在起始塑变机制上,则可能的机制是:先发生晶粒倾转,然后才出现晶粒内滑移带。 相似文献
963.
Hiong Yap Gan Yee Cheong Lam Nam Trung Nguyen Kam Chiu Tam Chun Yang 《Microfluidics and nanofluidics》2007,3(1):101-108
In this paper, we examined mixing of various two-fluid flows in a silicon/glass microchannel based on the competition of dominant
forces in a flow field, namely viscous/elastic, viscous/viscous and viscous/inertial. Experiments were performed over a range
of Deborah and Reynolds numbers (0.36 < De < 278, 0.005 < Re < 24.2). Fluorescent dye and microshperes were used to characterize
the flow kinematics. Employing abrupt convergent/divergent channel geometry, we achieved efficient mixing of two-dissimilar
viscoelastic fluids at very low Reynolds number. Enhanced mixing was achieved through elastically induced flow instability
at negligible diffusion and inertial effects (i.e. enormous Peclet and Elasticity numbers). This viscoelastic mixing was achieved
over a short effective mixing length and relatively fast flow velocities. 相似文献
964.
The local and global instability and vibration of systems subjected to non-conservative loading 总被引:1,自引:0,他引:1
The paper presents the results of theoretical and numerical studies on the slender, geometrically nonlinear system supported at the loaded end by a spring of a linear characteristic and subjected to non-conservative (generalized Beck's) loading. The boundary problem was formulated based on the Hamilton principle and then solved using, due to the nonlinearity, the small parameter method. The bifurcation force depending on system parameters and local and global instability regions has been determined in the study, and the characteristic curves have been plotted in the load-free vibration plane. 相似文献
965.
Joost Van Slycken Patricia Verleysen Joris Degrieck Jeremie Bouquerel Bruno C. De Cooman 《Metals and Materials International》2007,13(2):93-101
Multiphase TRansformation Induced Plasticity (TRIP) steels combine excellent ductility and high strength, making them ideally
suited for shock absorbing parts in the automotive industry. When designing structures for impact, an understanding of the
mechanical properties of materials under high strain rate conditions is essential. An extensive experimental program using
a split Hopkinson tensile bar set-up was established in an effort to investigate the dynamic properties of various TRIP steel
grades. Four different TRIP steels are described with varying contents of the alloying elements silicon, aluminium and phosphor.
Moreover, several phenomenological models describing the strain rate and temperature-dependent mechanical behaviour are validated.
TRIP steel grades in which aluminium is the main alloying element show high elongation values, whereas a high silicon content
results in an increase in strength. The widely used Johnson-Cook model can describe the behaviour of TRIP steels and provides
the opportunity to study its material and structural response. 相似文献
966.
甘德华 《石油化工腐蚀与防护》2007,24(3):57-61
文章分析了硫化亚铁自燃的原理和条件以及中国石化上海石油化工股份有限公司芳烃联合装置抽提蒸馏塔倒塌的原因。通过样品分析了抽提蒸馏塔下部筒体段、上部筒体段、过热弯曲部位的16 MnR钢的金相组织、机械性能、化学成分,确定抽提蒸馏塔材质没有劣化;并进行了稳定性验算,确定抽提蒸馏塔倒塌是由失稳引起的。 相似文献
967.
The tensile behavior and microstructure of bulk, Sn-3.5Ag solders as a function of cooling rate were studied. Cooling rate
is an important processing parameter that affects the microstructure of the solder and, therefore, significantly influences
mechanical behavior. Controlled cooling rates were obtained by cooling specimens in different media: water, air, and furnace.
Cooling rate significantly affected secondary dendrite-arm size and spacing of the Sn-rich phase, as well as the aspect ratio
of Ag3Sn. The Sn-rich dendrite-arm size and spacing were smaller for water-cooled specimens than for air-cooled specimens. Furnace
cooling yielded a nearly eutectic microstructure because the cooling rate approached equilibrium cooling. The morphology of
Ag3Sn also changed from spherical, at a fast cooling rate, to a needlelike morphology for slower cooling. The changes in the
microstructure induced by the cooling rate significantly affected the mechanical behavior of the solder. Yield strength was
found to increase with increasing cooling rate, although ultimate tensile strength and strain-to-failure seemed unaffected
by cooling rate. Cooling rate did not seem to affect Young’s modulus, although a clear coorelation between modulus and porosity
was obtained. The mechanical behavior was correlated with the observed microstructure, and fractographic analysis was employed
to elucidate the underlying damage mechanisms. 相似文献
968.
Sergei Bulanov Francesco Pegoraro Jun-ichi Sakai 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1998,410(3):17-487
We discuss the formation of typical (structurally stable) singularities in nonlinear wave breaking in stable and unstable media. The wake wave-break due to the inhomogeneity of the Langmuir frequency is accompanied by electron injection into the acceleration phase. In a wake wave excited behind a finite width laser pulse, the wave-breaking mechanism involves the increase, with the distance behind the pulse, of the curvature of the wake front, followed by the self-intersection of the electron trajectories. In the long wavelength limit, the Weibel instability which leads to the generation of a strong magnetic field, the relativistic self focusing and the Rayleigh-Taylor instability of a thin plasma slab provide examples of a common behavior with the rarefaction wave-breaking in unstable media. We present a solution of the Cauchy problem that describes the evolution of nonlinear perturbations of the Rayleigh-Taylor instability in terms of analytical functions of a complex variable. 相似文献
969.
An experimental study on the thermomechanical properties of microelectronic gold-bonding wires was conducted using high-precision,
microforce tensile tests. The load-displacement behavior of three types of gold wire (GL-2 type, FA type, and SR type) was
carefully recorded for determining the elastic modulus and stress-strain curves. Tests were conducted with miniature specimens
at temperatures ranging from room temperature to 250°C and load rates on the order of 1 mm/min and 10 mm/min. The testing
results indicated that the tensile strength of all three types of wire decreased with temperature, especially the SR type.
The load strain rate has a significant effect on the SR type but little effect on the GL-2 and FA wires. The stress-strain
curves from these tests were analyzed to fit into empirical constitutive models that account for the strain, temperature,
and strain-rate effects. 相似文献
970.
Chul‐Hyun Yoon Jin‐Sup Shin In‐Woo Cheong Doug‐Youn Lee Young‐Jun Park Jung‐Hyun Kim 《应用聚合物科学杂志》2003,90(3):792-798
The effect of interfacial crosslinking on miscibility behavior in blend systems of isocyanate‐functionalized poly(n‐butyl methacrylate) (PBMA) and a carboxylic alkali‐soluble resin, poly(styrene/alpha‐methylstyrene/acrylic acid) (SAA), was studied with different dimethyl meta‐isopropenyl benzyl isocyanate (TMI) concentrations. For the blend films of pure PBMA and SAA, both theoretical analysis and direct observation showed immiscibility between PBMA and SAA. For the blend systems of isocyanated PBMA and SAA, Fourier transform infrared spectra and gel permeation chromatography analyses qualitatively showed the crosslinking between the isocyanate group in isocyanated PBMA and the carboxylic group in SAA. Two tan δ peaks were shown in the blend system of SAA and isocyanated PBMA containing low concentrations of TMI (from 0 to 5 wt %), and the span of the two peaks became shorter as the TMI concentration increased. For a high TMI concentration (7 wt %), only one tan δ peaks was observed. This result means the interfacial crosslinking between isocyanated PBMA and SAA occurred fully, and thus the miscibility between two polymers was significantly improved. As these results showed, the tensile strength of the blend film of isocyanated PBMA and SAA was higher than that of pure PBMA and SAA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 792–798, 2003 相似文献