Tensile load-bearing capacity of co-cured double lap joints

The co-cured joining method has several advantages over the adhesively bonded joining method because both the curing and the joining processes for the composite structures are achieved simultaneously. In this study, the tensile load-bearing capacities of co-cured double lap joints were investigated experimentally and compared with the analytical results calculated by finite element analysis. Co-cured double lap joint specimens with several bond parameters such as bond length, surface roughness, and stacking sequence of the composite laminate were fabricated and tested. From the experimental results, it was found that the failure mechanism of the co-cured double lap joint was cohesive failure by delamination at the first ply of the composite laminate in the co-cured double lap joint. Finally, optimum values of several bond parameters were determined. Analytical tensile load-bearing capacities of the co-cured double lap joints were calculated by the three-dimensional Tsai-Wu failure criterion using stress distributions obtained from finite element analysis.     

System Concept and Simulation Model for a Proposed Class of Delay-Tolerant Variably-Priced Network Services

We describe a system concept for therevenue-producing disposition of surplus capacity atoff-peak times in real trunking networks. The idea is toapproximate a competitive market for distribution of the networks' time-varying excess capacity with apricing strategy controlled by the network. The schemeis intended to allow network operators to stimulatebackground traffic loads to gain new revenues from otherwise idle time on existing installedresources. The concept is suitable for low prioritydelay-tolerant or opportunistic applications such asremote backups, software distribution, dispatchingbatched faxes, disseminating newsgroup updates,updating web page caches or routing tables. Backgroundservice subscribers are notified of price reductions atoff-peak times to elicit additional traffic for the network. Traffic aggregators act on behalf ofsubscribing organizations or groups of users. Thebackground service is completely subordinate to theconventional tariff-priced on-demand calling services and the variable background pricing merges withthe foreground under suitable total load. This paperfocuses on the network problem of price setting tocontinually maximize the price-volume product in a time-varying price-sensitive trafficenvironment such as this concept implies. Aprice-stimulated offered traffic environment issimulated in which time of day, price, and hidden demandlatency and demand curve characteristics all affect the offeredtraffic. An analytically optimum strategy is availablefor the particular traffic model used and theperformance of a fuzzy logic price controller is tested against the revenue-optimal strategy. Dependingon econometric assumptions for latent traffic demand andprice-volume curves, increases in revenue from 4%-20%are obtained in simulation of a 30-trunk group having a typical daily load pattern.     

上海卷烟厂污水治理

上海卷烟厂选用一套日处理能力为1920m3(80m3/h)的生活、生产污(废)水二级生化处理装置处理污水。针对运行过程中产生的污染负荷增大、沉淀池沉淀区深度不足、污水中含有不能降解的纤维及影响中水回用问题,采取了相应的改进措施:①改厌氧池为缺氧池;②在沉淀池内增设斜板以弥补沉淀区深度不足的缺陷;③在二级生化处理后再增加过滤装置并进行投药杀菌。改进后,大大改善了出水水质,达到了接近零排放的环保要求,并且扩大了中水回用范围。实践证明,根据污水水质特点所选用的二级生化处理较为经济,能达到较好的治理效果。     

Sulphur partition between hot metal and high alumina blast furnace slag

Abstract

The sulphur partition ratio between hot metal and high alumina blast furnace slag (>18% alumina) has been examined on cast by cast basis for G blast furnace of Tata Steel. Equilibrium sulphur partition ratio was calculated from sulphide capacity with the help of oxygen activity in the melt. Oxygen activity was calculated from SiO₂/Si, MnO/Mn and CO/C equilibria. The equilibrium sulphur distribution calculated by considering the reaction [C]+[O]=(CO)_g in equilibrium for estimation of oxygen activity was very close to measured sulphur distribution ratio on cast by cast basis. Use of MnO/Mn pairs gives very high oxygen activity compared with SiO₂/Si and CO/C pairs.     

The Influence of FRW-1 Fire Retardant Treatment on the Bonding of Plywood

In this work the influence of FRW-1 fire retardant treatment on the bonding strength of plywood was studied. The results showed that the bonding strength of FRW-1 fire-retardant-treated Poplar plywood decreased by 25.3% as compared to untreated plywood; furthermore, free formaldehyde in the fire-retardant-treated Poplar plywood decreased by 64.9% when compared to untreated plywood. In our studies we also analyzed: the pH value and the buffering capacity of fire-retardant-treated and untreated wood powder; and the influence of FRW-1 fire retardant treatment on the gelation time of urea-formaldehyde (UF) adhesives. The results show that FRW-1 fire retardants reduced the pH value and increased the buffering capacity of FRW-1 fire-retardant-treated wood powder. The gelation time of the UF adhesive mixed with FRW-1 fire-retardanttreated wood powder was shortened by 15% as compared with the untreated wood powder. The results of the scanning electron microscope analysis showed that the FRW-1 fire retardant was mainly confined to: the trachea lumen of the Poplar wood; the wall of trachea; as well as around the pits when using an impregnation method at ambient temperature and pressure. It is possible that this has led to the decrease in mechanical action between the veneer and the adhesive.     

Prediction of the tensile load-bearing capacity of a co-cured single lap joint considering residual thermal stresses

In this paper, stress distributions in a co-cured single lap joint subjected to a tensile load were investigated using the finite element analysis. Residual thermal stresses, which resulted from the curing process of the co-cured single lap joint, were also considered. Since the adhesive layer in the co-cured single lap joint was about 10 μm thick, very thin compared with the thickness of both adherends, the interface between the steel and composite adherends was assumed to be perfectly bonded. The co-cured single lap joint was analyzed with respect to several bond parameters such as the bond length and stacking sequence of the composite adherend. The failure mechanism of the co-cured single lap joint was partial cohesive failure in the composite material, which was significantly affected by the interfacial tensile stress at the free edge of the co-cured single lap joint. Interfacial tensile stress was a primary factor that caused interfacial delamination between the steel and composite adherends in the co-cured single lap joint. Finally, tensile load-bearing capacities calculated from the Ye-delamination failure criterion were compared with the experimental results, and relatively good agreement was found.     

Efficient CDMA System Design for Highway Microcells Based on Accurate Modeling of Path Loss

Out-of-cell interference is an important factorin determining the system capacity of CDMA systems.Out-of-cell interference is influenced by propagationparameters such as slope index s of the path loss model, the standard deviation sigma of shadowloss, and the correlation coefficients of shadow lossfor propagation from the desired base station and fromthe interfering base station. For line-of-sight (LOS) cells along streets or roadways,propagation may be described by a two-slope model thathas smaller slow-fading loss sigma and a larger slopeindex past the breakpoint R_b than thesingle-slope model. As a result, smaller out-of-cellinterference is obtained with the two-slope model,leading to system designs having less infrastructurethan are obtained using the single-slope model. In thispaper we examine how a more realistic prediction ofquality of service (QOS) made with the two-slope modelleads to cost-effective system designs.     

New method to determine optimum water content for iron ore granulation

Abstract

Granulation is necessary before iron ore sintering. The optimum granulation moisture added to the mixture of iron ores, fuel and coke for obtaining suitable size distribution of the granules after tumbled in a drum is of vital importance for the sintering. In order to investigate the optimum moisture content, the moisture capacity of the iron ore, which means the maximum water content held in iron ores of unit mass, is defined and measured in a self-designed apparatus. The relationship between the moisture capacity and some other characteristics of iron ores, which include mineral and chemical composition, size distribution and mineralogy, is discussed. It was found that the mineral composition and the size distribution of the iron ore particles greatly influence the moisture capacity of the iron ores. The moisture capacity of the iron ore was also applied to optimise the granulation by finding the relationship between the moisture capacity of the mixture and the optimum water content. The moisture capacity has positive correlation with the optimum water content. The iron ore, which has high moisture capacity, needs more water added in the granulation process in order to get high permeability. The correlation was given to predict the optimum water content in the granulation based on the moisture capacity measurement.     

Mechanism of post-weld heat treatment cracking in Rene 80 nickel based superalloy

Abstract

Microstructural studies carried out on Rene 80 (approximate composition 60Ni–14Cr–9.5Co–4Mo–5Ti–3Al–0.17C–Zr–B, wt-%) weldments before and after post-weld heat treatment (PWHT) revealed abundant evidence of constitutionally liquated and resolidified grain boundaries extending from the mushy zone into the heat affected zone (HAZ). While total dissolution of γ' occurred along such grain boundaries, a much lesser degree of γ' dissolution was noted in the adjacent material. During the PWHT, a high density of γ' precipitated out both within the mushy zone and in the constitutionally liquated and resolidified grain boundary regions in the HAZ. As the dissolution and reprecipitation of γ' occurred fairly uniformly throughout the mushy zone, the ensuing aging contraction stress/ strain was fairly uniformly distributed in the region. In contrast, in the adjacent part of the HAZ, an extreme volume of γ' precipitation occurred locally along the grain boundary regions, a result of the highest concentration of γ' forming solutes and the complete dissolution of γ' during welding in these regions. This, combined with the much stronger adjacent grain matrix, caused the aging contraction stress and strain to become highly concentrated along the grain boundary regions in the HAZ. This promoted the formation of PWHT cracks along such grain boundaries, which then propagated along the grain boundary into the mushy zone and beyond.     

Novel technology for improving damping capacity of aluminium foam by interface layer

Abstract

A novel technology of designing interface layer using macromolecule resin element, polystyrene, to enhance the damping capacity of aluminium foam is successfully attempted. The interface layer was fabricated by coating a polystyrene film on the pore surface of the aluminium foam using a similar sol–gel technology. Results of the measurements show that the introduction of interface layer not only improves the mechanical strength, but also significantly enhances the damping capacity that can be an order increase relative to the corresponding aluminium foam matrix in the temperature range of room temperature to 80°C. The involved damping mechanisms include the intrinsic damping and interface damping of the constituents. The latter should be dominant as a result of relatively easy energy dissipation through interfacial friction.