Abstract: According to expansive soil, consolidated drained tests and undrained tests are carried on under saturated and remoulded conditions. The stress-strain characteristics of saturated soil are researched systematically under different confining pressure, initial dry density, initial water content, shearing rate and drainage condition. The inherent unity of diversity of shearing strength for the same samples measured by different experimental methods is indicated according to the normalization of critical state test results.
Abstract: By conducting simple tension and torsion tests to material, constitutive equations of one dimension are obtained. Plastic theories of continuum mechanics are used for analyzing deformation behavior of the material after yielding. Here, material is presumed to have isotropic hardening characteristic. By using Mises loading function and the associative flow rule, the derivations are made to extend the constitutive equations of one dimension in the simple tension and torsion tests to that of multi-dimension and obtain the plastic constitutive equations of the material in complex stress state , respectively.
Abstract: Short carbon fiber is used to reinforce phenol formaldehyde (PF) resin/graphite composite. With carbon fiber by thick nitric acid liquid-phase oxidative surface treatment (TNALPOST) and its content 3.wt%~ 4.wt%, the composite flexural strength is increased highly and electrical conductivity is also increased on some degree. To PF resin/graphite matrix material without carbon fiber added, if PF resin content is 15.wt%, its flexural strength is 49.0MPa and electrical conductivity is 111S/cm. But with adding carbon fiber by TNALPOST and the same PF resin content , the composite flexural strength and electrical conductivity approach 68MPa、122S/cm respectively, both mechanical property and electrical property satisfy the requirement of USA Department of Energy on carbon filler/polymer composite bipolar plate. The PF resin/graphite composite without carbon fiber added presents brittle fracture mode, but with carbon fiber added, it presents ductile fracture mode. According to the fracture morphology by scanning electron microscopy, carbon fiber and matrix is on relatively weak boundary bonding state accompanied by fiber de-bounding、sliding、pulling-out and bridge-making to crack, they are main factors contributed to improving composite toughness.
Abstract: A microporous poly(vinyl alcohol)/Starch composite polymer membrane was successfully synthesized by a biodegradation method. Effects of different poly(vinyl alcohol)/Starch compositions on the porous structures of the porous polymer membranes were further investigated in detail. The characteristic properties of PVA/ Starch composite polymer membranes were systematically studied by scanning electron microscopy (SEM), SL200B angle of contact instrument and Sturm test. The result shows the formation of 1μm-10μm microporous in the blend polymer membrane, which strongly depended on the content of starch in the blend. This method is convenient and will greatly promote the practical application of porous polymer membranes in various areas.
Abstract: In this paper, the principle of coherent gradient sensing (CGS) technology is briefly introduced. Fracture behaviour of the PMMA specimens with single or double cracks under three-point-bending are studied using the CGS optical method. A series of CGS fringe patterns under different loading are abtained. With these fringes, stress intensity factors are caculated. The influences of the different spacing on stress intensity factors are discussed. These results will be useful for researching on strength of PMMA materials.
Abstract: The interface between matrix and casting tungsten carbide particle is produced by the the particles’ decomposition. Casting tungsten carbide particle is a kind of eutectic product，which is composed of two phases: WC and W2C. The two phases have differing chemical and physical properties, and thus follow different paths to achieve their decomposition process. By observing the decomposition of the particle, a hypothesis was put forward about how the casting tungsten carbide particle decomposes in steel/iron composites. An experiment was then designed to prove this hypothesis. The experimental result shows that heat gain plays a significant role in the decomposition process of casting tungsten carbide particles.
Abstract: The Mn loaded ACF (ACF-Mn), prepared by impregnation method combined with activation method under high temperature, can be used to adsorb the low concentration SO2. The modified ACF was characterized by iodine value and functional groups. The adsorption properties of low concentration SO2 on ACF-Mn-Cu50 were also studied. The result showed that the adsorption properties were improved with the granular Cu. Amount of Mn particles attached to the surface of ACF and the desulfurization rate of ACF-Mn-Cu50 both increased after second modification when the adsorption temperature was 60°C, the air velocity was Q1=0.3 L/min and Q2=0.4 L/min respectively and the concentration of SO2 was 0.62×10-4 μg/ml.
Abstract: A method for indirect online over-temperature detection of isolators in high voltage switchgear is proposed，which is based on Na Superionic Conductor CO2 sensor. The over-temperature detecting principle is put forward and an over-temperature detecting system based on the method is introduced. The reliability of over-temperature detection depends on signal noise ratio (SNR), but the sensor and signal processing determine the SNR of CO2 signal. Based on quantitative analysis, it is concluded that Na Superionic Conductor CO2 sensor has higher SNR. By signal processing, the necessity of moving average filter for SNR is demonstrated. A temperature compensation circuit is adopted to eliminate the influence of temperature. In view of the characteristics of rude signal, an appropriate method of real-time digital filtering is used to improve the Signal-to-Noise Ratio. The different features of the signal under over-temperature condition have been analyzed and compared to those under normal conditions. The paper introduces a reliable algorithm for identifying over-temperature detection based on sequential section differences. Experiments prove that the method is feasible.
Abstract: The evolution of surface roughness of Al-5052 plate subjected to shot peening was simulated by means of LS-DYNA, and the influences of variation of parameters, such as the size of shot, the velocity of shot, the density of shot, strength coefficient, strain hardening exponent, friction coefficient and incident angle, were investigated. Moreover, the effect of space ratio of two shots was also studied. The simulated results, analytical results and experimental results were compared, and the results showed that the simulated results were agreement with experimental results and analytical results, that the important roles played by the shot size and shot velocity, but to a much lesser extent by the other parameters.
Abstract: In this study, composite metastable (Ti,Al,Nb)N coatings were respectively deposited on a wrought martensite steel 1Cr11Ni2W2MoV by arc ion plating technique with different negative pulse bias. With the increase of negative bias, the deposition rate initially increases and then decreases, metallic composition of the coatings deviates from the target more obviously, grain size is refined and the orientation of B1 phase changes from (111) to (220), and the hardness of the coatings improve first and then drop.