The bonding strength and corrosion resistance of aluminum alloy by anodizing treatment in a phosphoric acid modified boric acid/sulfuric acid bath

The process of phosphoric/boric/sulfuric acids anodizing was studied as a new pre-treatment for adhesive bonding of aluminum alloys. The microstructure and topography of the anodic films were examined using SEM and AFM, and the adhesive strength and corrosion behavior were studied with lap-shear test, wedge test and electrochemical technology. The results showed that by the process of phosphoric/boric/sulfuric acids anodizing a thicker film with high porosity and big pores can be obtained. The porous film was beneficial to improve the durability and lap-shear strength of the bonding joints. The thicker film can also provide better corrosion resistance. Compared with the films by boric/sulfuric acids anodizing and phosphoric acid anodizing, under humid and hot environments the phosphoric/boric/sulfuric acids anodic film showed better corrosion resistance, higher bonding strength and durability, and is a promising pre-treatment for adhesive bonding of aluminum alloys instead of the chromic acid anodizing process.     

一种新型充膏型高压超高压密封及其应用

开发出了一种新型充膏型高压、超高压密封。介绍了充膏型高压、超高压密封的结构原理、技术要求及应用。与传统的填料密封、间隙密封和组合密封相比,充膏型密封的密封压力高,可靠性好,密封寿命长,并对所密封的介质无选择。     

Thermal conductivity measurements of pitch-bonded graphites at millikelvin temperatures: Finding a replacement for AGOT graphite

Pitch-bonded graphites are among the best known thermal insulators at sub-kelvin temperatures, but are very good conductors at higher temperatures. This makes them ideal for mechanical supports which must provide good thermal isolation at an operating temperature below 1 K, but must have good conductance at higher temperatures to aid in initially cooling down an instrument (a “passive heat switch”). One type of graphite, AGOT, has been known as having the lowest thermal conductivity below 1 K not only among graphites, but also compared with any other material. It is, however, no longer available. We have carried out thermal conductivity measurements at temperatures between 60 mK and 4 K on a proposed replacement, POCO AXM-5Q graphite, as well as a sample of AGOT graphite. Our measurements show that both graphites have a difference of about six orders of magnitude in conductivity between room temperature and 100 mK, but that AGOT graphite is not as good an insulator as previously believed. We conclude that AXM-5Q graphite is not only a suitable replacement for AGOT, but in fact is somewhat superior.     

Characterization of thin TiO2 films prepared by plasma enhanced chemical vapour deposition for optical and photocatalytic applications

Thin titanium oxide films were deposited using a radio frequency (RF) plasma enhanced chemical vapour deposition method. Their optical properties and thickness were determined by means of ultraviolet-visible absorption spectrophotometry. Films of the optical parameters very close to those of titanium dioxide have been obtained at the high RF power input. Their optical quality is high enough to allow for their use in a construction of stack interference optical filters. At the same time, these materials exhibit strong photocatalytic effects. The results of structural analysis, carried out by Raman Shift Spectroscopy, show that the coatings posses amorphous structure. However, Raman spectra of the same films subjected to thermal annealing at 450 °C disclose an appearance of a crystalline form, namely that of anatase. Surface morphology of the films has also been characterized by Atomic Force Microscopy revealing granular, broccoli-like topography of the films.     

Structural integrity assessment of superheater outlet penetration tubeplate

In recent years, the Linear Matching Method (LMM) has been developed for the integrity assessment of the component subjected to cyclic thermal and mechanical loads. In this paper, the fatigue damage of a superheater outlet penetration tubeplate is assessed in detail using the LMM with an ABAQUS 3D finite element model. The significant thermal transients of the component are due to out of phase steam temperature oscillations. The primary loading on the component is from pressure (steam and gas) and system moment on the penetration and tailpipes. A transient thermal analysis is performed as the first step to determine the component temperature history during the cycle. Then these temperature solutions are used as an input to structural analysis to obtain the elastic stress history caused by these temperature loads. A shakedown analysis is thereafter carried out and the evaluation of the steady cyclic behaviour of the tubeplate during the steady state cycle is then achieved using the LMM. By assessing both constant and changing residual stress solutions associated with the steady state cycle, an LMM ratchet limit analysis is carried out to determine the capacity of the component subjected to the existing thermal transients to withstand additional primary loads including both pressure and moment. The total strain range over the steady state cycle is evaluated for the fatigue damage assessment. The comparisons of stress and strain range calculations for the out of phase temperature oscillations by the LMM and other methodologies prove the applicability and effectiveness of the LMM. The temperature-dependent elastic–plastic properties are adopted throughout the LMM assessment.     

Structural stabilities, electronic structures and lithium deintercalation in LixMSiO4 (M = Mn, Fe, Co, Ni): A GGA and GGA + U study

Dilithium-orthosilicate oxides Li₂MSiO₄ (M denotes transition metals) have been one of the focuses in the field of new cathode materials for Li-ion batteries recently, due to their possible high capacities and probabilities achieving by experiment. Using the density functional theory within both the generalized gradient approximation (GGA) and GGA + U frameworks, the structural stabilities, electronic structures and delithiation process for the dilithium-orthosilicate oxides Li₂MSiO₄ (M = Mn, Fe, Co, Ni) are systematically investigated. Within the GGA + U approach, LiMSiO₄ is shown to be a stable non-stoichiometric structure, while the compound Li_1.5MSiO₄ are unstable relative to a two-phase form containing Li₂MSiO₄ and LiMSiO₄, which is consistent with the experimental voltage profiles. For Li_0.5MSiO₄, though the formation energies are negative for Mn-system and Ni-system, the absolute values are so small that they would be likely to also undergo phase separation at room temperature. The average deintercalation voltages calculated by the GGA + U scheme are in good agreement with the available experimental data. Furthermore, the possibility of the exchange of two electrons per M in Li₂MSiO₄ is also discussed based on the calculated results.     

Stream Sockets versus Web Services for High-Performance and Secure Structural Analysis in Internet Environments

The increased growth of internet use in the last several years has opened up new possibilities for structural engineering analysis, moving from personal computer oriented software to client–server distributed software. In this paper two client–server applications for structural engineering based on stream sockets and on web services are presented. These two technologies have been chosen to compare, in terms of performance and complexity, new internet protocols with traditional ways of implementing client–server applications. Moreover, special care has been taken in the security aspects as the internet has become much more susceptible to breaches of security. Therefore, two new applications based on the same technologies have been created that guarantee a secure use of structural software. Also, two different client applications are presented to emphasize the versatility and power of internet distributed technology—one as a stand-alone application and the other as an integrated commercial computer-aided design program.     

Graphical 3D Visualization of Highway Bridge Ratings

Aging highway infrastructure requires effective rating methodologies to prioritize bridges for rehabilitation and repair. To aid engineers in decision making regarding bridge maintenance, a three-dimensional (3D) visualization system is developed for rating reinforced concrete deck-girder bridge. Color codings show the most probable mode of failure for girder cross sections under combined moment-shear forces and allow an engineer to determine a rehabilitation strategy. The visualization system relies on 3D finite-element analyses using the open source framework OpenSees, making the system readily extensible to a wide range of bridge types and loading scenarios, as well as emergent reliability-based rating methodologies. Important features of the visualization system are emphasized, including the use of lighting and feature edge detection to improve the visual quality of a bridge model. Recent developments in scientific visualization are discussed for potential application to civil engineering problems.     

Integrity Problem of Large-Diameter Bored Piles

Bleeding is known to occur in bored piles (drilled pier). The generally accepted view is that bleeding in piles is confined to the upper part of the pile only. Under certain conditions during bleeding, channeling may happen. Practising engineers believed that the associated problems with bleeding and channeling in bored piles can be overcome by overcasting the piles. A case study of extensive integrity tests consisting of cross-hole sonic logging tests and dynamic load tests on bore piles, as well as continuous corings from top to bottom of the piles carried out, revealed that some bored piles have channeling of concrete at various depths. Most of them were larger diameter piles. The finding that bleeding and channeling are not confined to the upper part of the pile is contrary to the generally accepted view. This paper attempts to develop a theory for the bleeding and channeling of concrete to explain the mechanics of the occurrence of channeling in bored piles. The proposed theory is verified by the close correlation of the predictions of the theory with field observations of the case study. Based on the proposed theory, recommendation with regards to the quality of concrete will be made to avoid the occurrence of channeling of concrete in large-diameter bored piles. The implications on the structural performance pertaining to axial capacity, compressibility and durability of bored piles with channels will be investigated.     

GS4—52m^2电除尘器的改进

叙述了GS4—52m^2电除尘器的运行状况,介绍了针对电场积灰、振打装置故障、排灰系统结构不合理等问题所进行的改进及取得的效果。