Advanced Materials Research Vols. 160-162

Abstract: The impregnation stage of the Resin Transfer Moulding process can be simulated by solving the Darcy equations on a mould model, with a ‘macro-scale’ finite element method. For every element, a local ‘meso-scale’ permeability must be determined, taking into account the local deformation of the textile reinforcement. This paper demonstrates that the meso-scale permeability can be computed efficiently and accurately by using meso-scale simulation tools. We discuss the speed and accuracy requirements dictated by the macro-scale simulations. We show that these requirements can be achieved for two meso-scale simulators, coupled with a geometrical textile reinforcement modeller. The first solver is based on a finite difference discretisation of the Stokes equations, the second uses an approximate model, based on a 2D simulation of the flow.

Abstract: Low alloy steels such as ASTM A508 and A533 and their equivalent materials have been extensively applied in fabricating pressure vessels due to their relatively excellent mechanical properties and moderately good weldability. The integrity of such materials governs the safety of the power plants. These vessels mainly are subjected to random loading in service and the load cycle interactions can have a significant effect in fatigue crack growth. Studying of fatigue crack growth rate and fatigue life calculation under spectrum loading is important for the reliable life prediction of vessels. Many models have been proposed, but as yet no universal model exists. In this paper, a fatigue life predicted under various load spectra, using three different fatigue crack growth models namely the Austen, modified Forman and NASGRO models. These models are validated with fatigue crack growth test data under various variable amplitude loadings. This application is performed with aids of three-point bend specimens. The results show clearly the load sequences effect and the predicted results agree with some discrepancies between the different models as well as with the test data. Neglecting, the cycle interaction effects in fatigue calculation under variable amplitude loading lead to invalid life prediction.

Abstract: The microstructure and property of 15Cr1Mo1V steel welded joints after 70,000h service have been researched by OM, SEM, Vickers hardness test and small punch test (SPT). The microstructure of 15Cr1Mo1V steel welded joints after service became coarse and the grain boundary became vague. More carbide particles were observed in welded joints after service. The microhardness gradient curve of 15Cr1Mo1V steel welded joints before service was higher than that after service. The SPT properties gradient curves, including yield strength gradient curve and tensile strength gradient curve by SPT, had the same shape and trend as the microhardness gradient curve before and after service. The SEM fracture appearance of SPT specimens was the characteristic of ductile fracture, irrespectively of before or after service, though the dimple size was a little bit big and deep before service and some cluster particles were observed after service for the ripening of carbides.

Abstract: The SiC thin films as the window layer of p-i-n solar cell was prepared by PECVD technology in this article,investigated the influence of hydrogen dilution on the structure and optical properties of SiC thin films,found the optimal growth craft under the same conditions. The results showed that the optical band-gap of the window layer achieved the widest 2.2ev when hydrogen dilution rate was 6.25, furthermore, got inerratic surface morphology with deposition rate up to 0.1nm / s.

Abstract: In order to investigate the effects of temperature on the contact strengths of the thick-walled cellular solids, materials of H59 brass was chosen for the preparation of cylindrical specimens which contain single pore, double pores, three pores and four pores respectively. The contact strengths of these specimens were determined in a YE-600 hydraulic testing machine at 20°C (room temperature) and 300°C respectively. The experimental results show that: the temperature had great effect on contact strength of the thick-walled cellular solids, mainly reflected in loading capacity and deformation, when the temperature increased from 20°C to 300°C, the loading capacity of the solids were reduced by 10.94 to 14.85% and the corresponding deformations were increased by 97.50 to 108.33%, which depended on the micro-pores structures. Furthermore, the effects of temperature on cracks out-look mainly reflected in cracks deepening with temperature. When the temperature increased from 20°C to 300°C, the depth of the cracks increased about 78 to 110%, which also depended on the micro-pores structures. However, temperature had little effect on the initiating position of the cracks for all micro-pores structures discussed from 20°C to 300°C.

Abstract: In this paper, coconut-shell activated carbons (CSAC) used as the carrier of nicotinic acid (VPP) and the process of controlled release of VPP were studied. CSACs with relatively high yield and good adsorptive capacity prepared by CO2 activation method under the condition of 850oC, 1.5h activation time and 1.5L/min CO2 flow rate, were used as the VPP carrier. Langmuir model was suitable for describing the process of CSAC adsorbing VPP, and the maximum adsorptive capacity of CSAC was 136.32mg/g. The cumulative release percentages of VPP in distilled water, simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) were 22.53%, 45.86% and 53.94%, respectively. Higuchi model was the most suitable for describing the processes of CSAC releasing of VPP in the different media.

Abstract: Hexamethoxymethyl melamine (HMMM) was used to modify UF resins to obtain good performance with low formaldehyde emission. The effect of urea to formaldehyde ratio, HMMM content on the properties of UF resin was studied in detail. The results suggested that urea to formaldehyde ratio to be 1:0.9 and 20% HMMM content is the optimum formulation to afford desired UF resin. The viscosity, solidification time, bond strength and formaldehyde emission of the modified UF resins were also studied. The results revealed that the performance of the modified UF achieved the chinese standard.

Abstract: A new concept, “Plus Calcium Oxide Grade”, was put forward, which is the very mass percentage of iron element when Calcium Oxide addition fulfills the need of the basicity of the blast furnace slag. The “Plus Calcium Oxide Grade” and “Minus Calcium Oxide Grade” of iron ore, iron concentrate, sinter and pellet was calculated, analyzed and also compared. The results showed that: the Plus Calcium Oxide Grade can reflect the smelting value more objectively and reasonably, while the basic grade and “Minus Calcium Oxide Grade” can not. So it is suggested that the concept of “Plus Calcium Oxide Grade” can be brought into the iron ore dealing and using, and also into the area of iron concentrate, sinter, pellet and furnace mixture.

Abstract: This paper describes an improved extended transfer matrix method to evaluate the acoustic absorption coefficient of multi-layered structure with viscoelactic materials for perpendicular incidence plane acoustic. Here, the dynamic behavior of viscoelastic materials is taken into account. By comparing the calculated and measured results, it is shown that the results calculated by the improved extended transfer matrix method are in good agreement with the results measured. This improved extended transfer matrix method can accurately estimate the sound properties of multilayered structures with viscoelastic materials.

Abstract: The exploitation of high acid wells is facing severe corrosion challenges in the A and B gas fields in Sichuan, thus using lined steel pipe is a reliable and cost-effective anti-corrosion measure. However, lined steel pipe welding involves dissimilar steel welding, and anti-corrosion performances will be affected if the welding process is unreasonable. So it is necessary to make evaluation for corrosion of lined steel pipe. In this paper, taking welding gap of L245/825 lined steel pipe as example, the anti-SSC performances of L245/825 straight and ring welding gaps in NACE A solution were studied by CR method, and anti-cracking performances of them were evaluated by laboratory experiments. Then corrosion performances of L245/825 lined steel pipe welding gaps and L360NCS carbon steel were studied in the corrosive environment found in the Tian Dong 5-1 high sour gas well. Laboratory and field tests show that straight and ring welding gaps of L245/825 lined steel pipe have good anti-environment and anti-cracking performances of electrochemical corrosion in the high acid environment. The technology of welding process selected in the paper is reliable. Research results provide references for welding operation of L245/825 lined steel pipe in high sour gas fields.