Papers by Keyword: Dry

Abstract: Experimental techniques like X-ray diffraction (XRD) and pore size distribution determination (MIP), in conjunction with thermodynamic simulation (GEMS) and kinetic modeling of cement hydration (PK), were used to analyze the microstructures and phase compositions of cementitious materials under the coupling effect. This allowed researchers to study the evolution of formation products and pore structure of cementitious materials under the coupling of long-term wet and dry cycling and sulphate erosion. The findings demonstrate that the cement pastes with varying w/b ratios formed the expansion products calcium alumina and gypsum after 180 days of dry and wet cycling by 5% sodium sulphate solution; however, the specimens with lower water-ash ratios had denser structures, fewer erosion products, and better resistance to sulphate erosion. The following illustrates how sulphate erosion products affect the pore structure: during the early stages of erosion, the pore structure becomes more refined and has an increase in the number of transition pores between 10-100 nm due to the erosion products such calcium alumina and sodium sulphate crystals filling the pores. The degree of sulphate erosion is exacerbated by the formation of new cracks and larger macropores, which result in an increase in the number of erosion products, an increase in the average pore size, and a looser pore structure. However, the calcite growing in the transition pores is more destructive, and the crystallisation pressure keeps building up, leading to the destruction of some of the transition pores.

Abstract: Many of the previous studies on cutting properties have compared various steels with a same heat treatment, and there are almost no studies that focus on the differences in heat treatments of a same material. In this report, the influence of different heat treatments on tool wear of high-carbon steel (C55) is experimentally investigated in turning process. This study focused on three heat treatments: quenching and tempering, normalizing, and spheroidization annealing. We divided flank wear into 3 areas (corner, middle area and groove wear) for observation and analyzed each characteristic. It is found that for C55, regardless of heat treatment types, wear at the corner of the insert tip is highly dependent on cutting speed, whereas the dependence is lower where it is far away from the corner. This result is considered to be due to the adhesion that occurs while cutting. Therefore, selecting the cutting speed that minimizes flank wear at the corner can control tool wear and extend tool life. In terms of real-time monitoring for tool replacement, the correlation coefficient between the flank wear and the sensing data (spindle current, feed-axis servo motor current, and cutting sound) is also considered to depend on the adhesion condition at the insert tip. If adhesion occurs, the correlation coefficient is not stable and it’s likely to be difficult to predict wear trend to check the end of a tool life. Adhesion makes tool wear prediction using the sensing data difficult.

Abstract: This titanium material is very difficult to machine due to its low thermal conductivity resulting in heat generated when machining accumulates in the cutting zone. This causes the thermal effect to be absorbed in the drill tool so that the tool wears out quickly which affects the quality of the hole. This study aims to examine the effect of tool wear on the cutting force of hole quality under dry machining conditions and machining using the MQL method. The cutting force resulting from the process of drilling holes using MQL is smaller than drilling in dry conditions. The larger the feed (f), the greater the cutting force (N) that is generated during the drilling process in dry conditions and MQL conditions. The greater the cutting speed (v) used during the drilling process, the lower the cutting force generated

Abstract: The present work aims to experimentally investigate the effect of Kevlar fiber hybridization on dry sliding friction and wear behaviour of bamboo fiber reinforced laminated epoxy composite. Monolithic bamboo laminated composite and different bamboo/Kevlar inter-ply laminated hybrid composites with variation in number of both the laminas were developed in house by hand layup technique. Pin-on-disc experiment was employed to determine its tribological performance. The wear mass loss, specific wear rate and co-efficient of friction of the developed composites, when slide against a rotating disc, were determined and analyzed. The wear mechanisms were studied from the microstructure. From the results, it is observed that, wear loss and co-efficient of friction values were increased with the increase in number of Kevlar laminas.

Abstract: This study examined the influence of cutting speed, cutting fluid, and pre-impregnated carbon fiber orientation on tool wear and finished surface roughness during turning of carbon fiber reinforced plastic (CFRP) pipes. In the dry cutting process, the tool wear decreased as the cutting speed was increased. An average cutting speed of 92 m/min or higher was found to be acceptable with respect to tool wear. The use of mineral oil resulted in a reduction of tool wear when compared with that in the case of dry cutting. The tool wear with water was lower than that with mineral oil. It was assumed that cooling by water was more effective than lubrication by mineral oil. The results clearly indicated that the tool wear and the finished surface roughness were affected by the carbon fiber orientation.

Abstract: In the influence of the atmosphere,the soil of the subgrade would frequently in continuous humidification and dehumidifying situation, and it will result in large variation of the engineering properties of the subgrade. So, it is important to study the water migration in subgrade under the influence of the climate. In this paper, based on moisture and heat coupling thermal, non isothermal equation of unsaturated soil are introduced, the subgrade evaporation model are established. The theoretical analysis and numerical calculation of the subgrade moisture changes and its influence factors under the effect of the atmosphere are studied. The study results show that: solar intensity are the most important factors to the subgade moisture, the solar radiation makes the temperature of the pavement rising, the evaporation of the pavement would be speed up. In the wet and dry cycle process, as the rainfall intensity is small, it has little effect to the subgrade moisture, in the same rainfall duration conditions, although the evaporation duration is the same, the subgrade moisture still changes with the rainfall intensity, the larger the rainfall, the more changes of the subgrade moisture. Little intensity and long duration rainfall pattern affect the subgrade moisture more intensity than that of large intensity and short duration rainfall pattern.

Abstract: To determine the friction forces and friction coefficient in dry and lubricated conditions between steel and a triol crosslinked polyurethane, the authors developed a new experimental method consist in sliding of a steel cylinder on a plate polymer sample in the direction of the cylinder axis. By using this method the experiments were realized on a deformed path in the polymer sample by maintaining the same pressure distribution between the contact elements during the experiments. The experiments were realized with normal load between 1 N and 8 N and a cyclic linear speed having values between 1mm/s and 10 mm/s. Were determined the friction forces and friction coefficients in dry and lubricated contacts. An analytical model to evaluate the friction force in the cylinder – polymer contact surface has been developed and a good correlation with the experiments was obtained.

Abstract: In order to study the gas-solid flow characteristics in a rotational spouted-fluidized bed dryer, the eulerian multi-phase model was applied in three-dimensional numerical simulation of a rotational spouted-fluidized bed to analyze the effect of different velocity ratios between bottom and tangential wind on gas and particle velocity distribution characteristics, and the change rule of gas-solid flow state with the time at the velocity ratio of 30 m·s^-1/30 m·s^-1 was derived. The results show that the increase of tangential wind velocity is propitious to enhance the gas flow rate in the region near the wall and make the gas-solid phase mix sufficiently as well as augment of the contact area of gas and particle phase, and decrease of the gas flow dead zones and the adhesion of viscous materials to cylinder wall. However, the negative pressure formed by the entrainment effect of tangential wind goes against the development of gas flow along the axial direction reducing the penetration effect of axial wind to the granular layer.

Abstract: In this article, the molecular weight of wet Natural Rubber (NR) with different initial moisture contents, 3.80%, 10.05%, 19.76%, respectively, dried by microwave at frequency of 2450MHz was investigated using GPC. It can be seen from the results that an obvious trend of M_n and M_w changes was presented. With the increment of initial moisture contents, M_n and M_w decreased gradually. The molecular weight distribution (d) increased with the initial moisture contents increment, but quite closer to each other.

Abstract: Along with our country " west-east electricity transmission " project and UHV projects, HTV-silicon rubber with superior properities has been more and more widely used in the western regions of China.The paper focus on hami to zhengzhou ±800kV UHV DC transmission project which in hami HTV-silicon rubber insulators aging problems, extract dry and the strong UV radiation climatic characteristics of the hami area to quantify, in the dry environment we conduct UHV levels of HTV-silicon rubber materials and normal voltage levels of HTV-silicon rubber materials on UV accelerated aging experiment.And the tests of hardness,static contact angle and Fourior transform infrared spectroscopy ( FTIR) are performed for the samples. The experimental results show that both samples hardness are larger, the flexibility are reduced; their both surface static contact angle are decreased, the hydrophobic are part of the loss; their both surface roughness are bigger,and a part of filler is leaked; FTIR of peak area of Si-CH3 and Si-O-Si keys absorption peak are reduced, shows a portion of the Si-CH3 and Si-O-Si keys is interrupted into free radicals; under the condition of the initial data of the two kinds of samples are similar , the variation of UHV levels of each data sample is lower than it of normal levels of samples. This is due to the UHV grade of HTV-silicon rubber materials on the formulation and manufacturing process are optimized, in the dry environment the UV aging resistance of UHV levels of HTV-silicon rubber materials is superior to it of ordinary voltage grade of HTV-silicon rubber materials.