Rheo-optic in situ synchronous study on the gelation behaviour and mechanism of waxy crude oil emulsions

An improved rheo-optic in situ synchronous measurement system was employed to investigate the gelation behaviour and mechanism of waxy crude oil emulsions. By combining transmitted natural light and reflected polarized light microscopy, a multiangle composite light source was built to achieve the simultaneous observation of wax crystals and emulsified water droplets, as well as their dynamic aggregation process. Main outcomes on the microscopic mechanism were obtained by developed microscopic image processing method. It was found that the microstructure of W/O waxy crude oil emulsion has the evolution of “individual structure--homogeneous aggregate structure--heterogeneous coaggregate structure--floc structure” during the static cooling, which results in the four stages during gelation process. Different from previous studies, the aggregation of emulsified water droplets was found to be more significant and contributes to the formation and development of the wax crystals-emulsified water droplets coaggregate, which plays a decisive role in the further evolution of the gelled microstructure. Time series microscopic images show the dynamic aggregation of emulsified water droplets and wax crystals. Two different aggregation behaviours between wax crystals and water droplets were observed. That wax crystals can not only embed in gaps between adjacent water droplets and enhance the structure, but also surround the outside of the water droplets and continue to grow resulting in the interconnection of different coaggregates to form a larger floc structure. In addition, correlation between viscoelasticity and microstructure evolution of waxy crude oil emulsions of different water contents was discussed. With increasing water contents, the microstructure is changed from wax crystal flocculation structure as the main skeleton and the emulsified water droplets embedded in it, into the aggregation of emulsified water droplets occupying the main position. When the number of wax crystals and water droplets reaches a certain ratio, did wax crystals form coaggregates with emulsified water droplets, and the remaining wax crystals formed an overall flocculation structure, the viscoelasticity of the waxy crude oil emulsion is the highest.

Mechanical Behaviour and Structure Instability of Al_3Ti Alloy

Trialuminide alloys of elements such as Ti. Nb or Zr are of particular interest as materials for high temperature usage because their density is very low and specific strength and elastic rnoduli are then very high. This report concentrates on recent work on Al3Ti alloys which have been alloyed with ternary elements such that the higher symmetry ordered cubic structure is obtained, leading to somewhat easier operation of deformation mechan isms and hence improved ductility and toughness.Fine details of the crystal structure of cubic trialuminides are considered here and it is shown that the materials generally possess some remnant tetragonal chemical ordering which can affect their me chanical behaviour. In addition the compositional range over which a stable single phase is retained is shown to be extremely small, such that in most cases the materials examined show some form of microstructural instability. These instabilities affect the mechanical behaviour of the materials, for exarnple producing general strengthening. leading to precipitation hardening du ring hig h temperature testing, and causing age hardening instabilities during high temperature static or dynamic testing.Such structural instabifity feads to significant modifications at superdislocations, affecting both the dislocation cores and their associated APB's. Failure for these cubic materials still occurs at very small plastic strains and seems to be determined by difficulties of superdislocation creation near a propagating crack rather than by problems of suitable dislocation configuration and mobility. Possible ways to enhance ductility and toughness by alloying and microstructural modification will be discussed.

Structural Dependence of Creep/Fatigue Behaviour of Single Crystal Ni-base Superalloy

The effect of different initial microstructures deftned by γ' precipitate morphology has been investigated at the creep/fatigue conditions of 900℃ and 500 MPa. The wave form of stress as a function of time for cyclic load was of trapezoidal shape with a hold time of 10s at the upper stress level. The TEM was employed to examine the deformation process in strengthened γ' matrix in dependence of γ' precipitate morphology. The fracture lifetime and cycle number up to fracture were the criteria to evaluate the additional cyclic component efFect on the course of deformation

Influence of Structural Modification on Work-hardening Behaviour of Type 316 Stainless Steel

Work-hardening behaviour of type 316 austenitic stainless steel having difFerent initial dislocation structures introduced by swaging to various levels is analysed by a simplified Kock's model which takes into account the structural changes through the dislocation accumulation and annihilation process during deformation. The dislocation accumulation and annihilation factors show a temperature and structure dependence. The dislocation annihilation factor shows a plateau or decreasing tendency in the dynamic strain ageing (DSA) temperature range. This is attributed as either due to dislocation accumulation being more pronounced than dislocation annihilation or as due to precipitates being formed at DSA temperatures acting as obstacles to dislocation motion in the DSA temperature range.

OUT-OF-PLANE COMPRESSIVE PROPERTIES OF HEXAGONAL PAPER HONEYCOMBS

The compressive behaviour of paper honeycombs is studied by means of an experimental analysis. Experiment results show how geometry aspects of hexagonal paper honeycombs, e.g. the height of paper honeycomb, the thickness and length of honeycomb cell-wall, the drawing ratio of hexagonal honeycomb, affect the compressive properties of the paper honeycombs. It is in good agreement with the theory model. The constraint factor K of the critical buckling stress is mainly determined by the length of honeycomb cell-wail. It can be described as K=1.54 for B type paper honeycombs and K=3.32 for D type paper honeycombs. The plateau stress is the power exponent function of the thickness to length ratio of honeycomb cell-wall, and the experiment results show that the constant is 13.2 and the power exponent is 1.77. The research results can be used to characterize and improve efficiently the compressive properties of paper honeycombs.

Small-scale multi-axial hybrid simulation of a shear-critical reinforced concrete frame

This study presents a numerical multi-scale simulation framework which is extended to accommodate hybrid simulation （numerical-experimental integration）. The framework is enhanced with a standardized data exchange format and connected to a generalized controller interface program which facilitates communication with various types of laboratory equipment and testing configurations. A small-scale experimental program was conducted using a six degree-of-freedom hydraulic testing equipment to verify the proposed framework and provide additional data for small-scale testing of shear- critical reinforced concrete structures. The specimens were tested in a multi-axial hybrid simulation manner under a reversed cyclic loading condition simulating earthquake forces. The physical models were 1/3.23-scale representations of a beam and two columns. A mixed-type modelling technique was employed to analyze the remainder of the structures. The hybrid simulation results were compared against those obtained from a large-scale test and finite element analyses. The study found that if precautions are taken in preparing model materials and if the shear-related mechanisms are accurately considered in the numerical model, small-scale hybrid simulations can adequately simulate the behaviour of shear-critical structures. Although the findings of the study are promising, to draw general conclusions additional test data are required.

High-pressure scheelite-type polymorph of SmCrO_4: synthesis, structural characterization and magnetic properties

The new scheelite form of SmCrO4 oxide was obtained by heating the zircon-type SmCrO4 oxide at 4 GPa and 803 K. X-ray diffraction revealed that this scheelite SmCrO4 phase crystallized with tetragonal symmetry, S.G. I41/a and lattice parameters: a=0.50776(3) nm and c=1.15606(2) nm. This structural phase transition from zircon to scheelite involved a decreasing of around 10% in the unit cell volume. Although the Cr-O and Sm-O distances did not change very much in both zircon and scheelite polymorphs, the changes occurred in the bond angles were remarkable that appear to support the proposed reconstructive model to explain this structural zircon-scheelite phase transition. Magnetic susceptibility and magnetization measurements revealed that the scheelite SmCrO4 oxide behaved an antiferromagnetic material, where the Sm3+ and Cr5+ were simultaneously ordered. The estimated Néel temperature, TN, was 16 K and the critical field at 12 K associated with the metamagnetic transition was 3.2 T.

Serration and Noise Behavior in Advanced Materials

The Chinese Materials Research Society（C-MRS）Conference（2015）was held in the Guizhou Park Hotel International Conference Center,Guiyang,China,from July 10-14,2015.This conference consists of 30symposia,including 4international symposia.As one of 4international symposia,＂Serration and noise behavior in advanced materials＂