Advanced Materials Research Vols. 284-286

Abstract: An implementation method of the virtual crack closure technique (VCCT) for fracture problems of non-homogeneous materials such as functionally graded materials (FGMs) with commercial finite element software ABAQUS^TM is introduced in this paper. In order to avoid the complex post proceeding to extract fracture parameters, the interface crack element based on the VCCT is developed. The heterogeneity of FGMs is characterized though user subroutine UMAT and the interface crack element is implemented by user subroutine UEL. Several examples are analyzed to demonstrate the accuracy of the present method.

Abstract: The coal-fired power plant is the main anthropogenic source of mercury pollution. The mercury in flue gas exists as elemental mercury(Hg⁰), oxidizing state mercury(Hg²⁺) and particulate mercury(Hg_p). Mercury speciation distribution in flue gas was influenced and controled by the factors including conditions of ignition, desulphurization or denitration and Based on the investigation of coal-fired power plant technologies of removing Hg, this research uses the modified activated carbon (MAC) and studies its removal efficiency. Result indicates that the uptake of Hg by MAC was﹥90%.

Abstract: Taking into account of the key technologies of manufacturing of metal gradient structure shaft with high strength and toughness, interface microstructure, element diffusion, interface micro hardness and resistance to crack propagation ability of the pre-compounding shaft of 25Cr5MoA/Q235 steel manufactured by the method solid-liquid were studied in this paper. The results show that using extrusion forming methods, dense microstructure formed near the interface, and after the quenching and tempering treatment, the interface microstructure appears continuous distribution. Interface shear test results indicate that the shear strength is 412.69MPa. Cr element in the combination of the interface appears a continuous distribution; after quenching and tempering it shows a more uniform distribution, and micro hardness changed about 240HV across a region ranging from the bonding interface to both sides by the distance of 50μm. While the micro hardness of 25Cr5MoA/Q235 steel by the method solid-liquid changed about 160HV after the quenching and tempering treatment. The fracture toughness test of gradient structure shaft by solid-liquid compounding shows that because of the termination of crack propagation at the interface between the outer and inner layer, the safety of the graded structured axis in service would be improved.

Abstract: The compressive strength and piezoresistive property of cement mortar with low adding level of multi-walled carbon nanotubes (MWCNTs) were investigated. Experimental results showed that the compressive strength of the MWCNTs/cement mortars increased with the adding amount of MWCNTs content for all the curing ages. Silica fume promoted the compressive strength development by well bonding with MWCNTs and filling effect. The electrical resistance changed synchronously with the compressive strength and the amount of the changes varied with the stress and MWCNTs addition levels. Higher MWCNTs doping level improved the piezoresistive sensitivity of the mortar. The mortar with silica fume (5-10% by weight of cement) exhibited better piezoresistive response than that without silica fume at the same MWCNTs doping levels.

Abstract: Element Mo plays a significant role in Ti(C,N)-based cermets. In this work, mixing was carried out in water and cermets with high mechanical properties were fabricated. The effect of Mo₂C content on microstructure and composition was investigated by field emission scanning electron microscope (FSEM) and energy dispersive spectrometer (EDS). Results showed that microstructure becomes uniformly distributed, binder distribution becomes symmetrical and the particle size becomes small with increase of Mo₂C content. The volume fraction of (outer + inner) rim structure increases, the volume fractions of core structure and binder phase decrease instead. It was found that Mo₂C content in raw material affects compositions in phases. With the level of Mo₂C content rising, the concentration of element Mo in rim structure increases, the concentration of element Ti in binder decreases.

Abstract: The fatty acid and antioxidant property of pawpaw coconut oil (PCO) and virgin coconut oil (VCO) were compared. GC and GC-MS were used to determine the fatty acid of PCO and VCO, respectively. The results show that there is no obvious difference of fatty acid composition between PCO and VCO. The scavenging rate to ABTS⁺• of PCO is higher than VCO at the same proportion. TEAC (Trolox equivalent antioxidant capacity) value of PCO is 67.5 µmol/l. The complexing ability to Fe²⁺ of PCO is stronger than VCO at the same proportion. The scavenging ability to DPPH• of 40% PCO is weaker than VCO, with the increase of PCO concentration, the difference of the scavenging ability to DPPH• between PCO and VCO is smaller.

Abstract: The research on ceramic matrix composites and their applications in aerospace field were discussed in terms of their advantages and features, fabrication methods, domestic and foreign research progress, difficulties and key technologies to be solved, and future development trends and directions.

Abstract: The section of steel column under axial compression presents heterogeneous material and its load condition changes after experiencing fire damage of one side. Taking H-section steel column under axial compression commonly used in engineering for study object in this thesis in order to study post-fire residual load bearing capacity, the post-fire eccentric effect of steel column under axial compression exposure to one-side fire is analyzed using the method of equivalent section which considering the change of the material strength after high temperature, the influence of non-uniform temperature field on material properties and the stiffness degradation of member section. Calculation methods of the eccentricity and additional moment are proposed and further given a formula of residual load bearing capacity.

Abstract: β-sialon-ZrO₂ composites with Si₅AlON₇ or Si₄Al₂O₂N₆ bonding phase were prapared in N₂ atmosphere at 1550°C with Si, Al₂O₃, AlN and ZrO₂ (Ca) as raw materials by reaction in situ pressureless sintering. Effect of Z value and content of β-sialon batch on its sintering performance, phase composition, microstructure, and thermal expansion character were investigated. Results showed that the phase of Si₅AlON₇ was formed in samples with β-sialon designing Z=1, and phases of Si₅AlON₇ and Si₄Al₂O₂N₆ were formed in samples with β-sialon designed Z=2 and β-sialon designed Z=3, respectively and Bending strength of samples increase with content of β-sialon batch. When content of β-sialon batch equals 10wt%, 15wt% and 15% respectively, the samples with β-sialon designed Z=1, Z=2, and Z=3 have lower apparent porosity, microstructure of homogeneous and compact and lower thermal expansion coefficient, respectively.

Abstract: In this paper fiber reinforced laminated composite for engine mount model are investigated by finite element method. Static analysis is carried out to find out the maximum displacement point or node on the bottom plate, on which the displacement is optimized. Different ply orientation and combinations of 0°/45°, 0°/90° and 0°/45°/90° are then studied under sinusoidal and dynamic load conditions to examine the effect of ply orientation on the structure’s displacement transportation, and to get the optimized ply orientation combination, which inherit least displacement from the excitation on the top plate. The result shows that the laminate with ply orientation of 0°/90° is the best as the Z-displacement on the bottom is considered.