Search

2195 Al-Li alloy is famous for high strength, excellent fatigue strength and good stress corrosion resistance, which is widely used in the manufacture of high-performance aerospace components. The aim of this study is to validate how the stress relaxation aging behavior effect on the mechanical properties of 2195 Al-Li alloy. Through mechanical property test, the research was found that the performance after stress relaxation aging is higher than artificial aging (AA). In addition, the analysis of scanning electron microscopy SEM and TEM revealed that dislocations should be introduced by the stress relaxation aging process, which is more conducive to the precipitation of the T1 phase and strengthened the material with prolong ageing time. The results show that stress relaxation aging can significantly promote the precipitation of the T1. Therefore, this paper sheds new light on how SRA can improve mechanical properties and that SRA make better improve the distribution of precipitates in the grain boundary.

This editorial outlines the vision that the new Journal of Service Research editorial team has about moving service research forward, which requires more than just duplicating the service research of the past. We encourage authors to be forward-looking and futuristic in their orientation. In this way, JSR can help guide the service research of the future.

The capability of noble metal nanoparticles (NPs) as efficient charge transfer mediators to stimulate Schottky-junction-triggered charge flow in multifarious photocatalysis has garnered enormous attention in the past decade. Nevertheless, fine-tuning and controllable fabrication of a directional charge transport channel in metal/semiconductor heterostructures via suitable interface engineering is poorly investigated. Here, we report the progressive fabrication of a tailor-made directional charge transfer channel in Pt nanoparticles (NPs)-inlaid WO

The effects of pre-treatments on the precipitate microstructures of an Al-Zn-Mg-Cu alloy are investigated. Meanwhile, the creep-rupture behavior of the under-aged and peak-aged alloys are comparatively analyzed. Additionally, the effects of pre-treatment on the fracture mechanisms are discussed. It is found that the precipitate microstructures are sensitive to pre-treatments. The intragranular precipitates of the peak-aged alloy are larger than those of the under-aged. The precipitate free zone of the peak-aged alloy is wider than that of the under-aged. Some large intergranular precipitates appear on the grain boundaries of the under-aged alloy, and induce the nucleation of microvoids. Eventually, the creep fracture of the under-aged alloy is accelerated. Therefore, the differences in microstructures lead to the shorter creep-rupture life of the under-aged alloy, compared to the peak-aged alloy.

A series of tests were carried out to investigate the effects of process parameters on mechanical properties and microstructures of 2124 aluminum alloy in creep aging process. The results show that creep strain and creep rate increase with the increase of aging time, temperature and applied stress. The hardness of specimen varies with aging time and stress in a low-to-peak-to-low manner. No significant effect of temperature on hardness of material is seen in the range of 185–195 °C. The optimum mechanical properties are obtained at the conditions of (200 MPa, 185 °C, 8 h) as the result of the coexistence of strengthening S′ and S′ phases in the matrix by transmission electron microscopy (TEM). TEM observation shows that applied stress promotes the formation and growth of precipitates and no obvious stress orientation effect is observed in the matrix.

In the paper, Construction technology and equipment improvement of plastic drainage boards driven in land area are studied. Because overlying hardpan is thick in some areas, drainage plate cant be driven by common vibratory board machine. In allusion to this instance, the machine was refitted to superficial drilling holes machine, a bore was drilled and then the drainage plate was driven to deal with the foundations covered with thick hardpan. Performance of this technology is researched and explored to deal with a complex foundation treatment by reclamation silt.

Creep Age Forming (CAF) is an effective forming technique combined forming and heat treatment, based on creep and age hardening characteristics of some aluminum alloys. It has been widely used to manufacture large integral panels with airfoil sections and complex curvatures of high strength aluminum alloy. The aim of this paper is to study the influence of element types on springback prediction of creep age forming of aluminum alloy integral panel. Firstly, the finite element models are built by 3D-solid elements and Shell elements separately. And then a set of creep aging constitutive equations of 7055 aluminum alloy are implemented into the commercial FE solver MSC.MARC through user defined subroutine. Finally, springback values predicted by 3D-solid elements model and Shell elements model respectively are compared under different height to width ratios. Some important conclusions were drawn. For the reinforcing panel with the height to width ratio is more than 5:1, shell elements should be used to get more accurate springback prediction result. If the height to width ratio is less than 5:1, solids elements should be used. Above conclusions provide theoretical basis for the study of CAF of the aluminum alloy integral panel by finite element simulation method.

Drum-shaped stone tongue that there are 3 ~ 5 m thick wedge silt on the bottom formed in the junction of silt and the stone embankment by reclamation silt with mountain stone during the course of backfill. In the paper, on the basis of drills, superficia drilling holes, deep drilling holes and vibrating stop plank model, boundary stone embankment shape and soft soil layer depth were obtained, cross section of stone embankment and stone embankment boundary were revealed during the course of artificial fill, study the stone tongue shape, soft soil around stone tongue, silt characters on stone tongue bottom and reinforcement treatments were studied to obtain treatment method which can satisfy the engineering requirement and can save the engineering cost and provide mature construction technology and method for the similar subgrade treatment of sea reclamation engineering.

Samples consisting of new aluminum lithium alloy (Al–Li alloy) plate developed by the Aluminum Company of America and Ti–6Al–4V alloy (Ti alloy) plate were investigated. Plate of 400 mm × 140 mm × 2 mm with single edge notch was anodized in phosphoric solution and Ti alloy plate of 200 mm × 20 (40) mm × 2 mm was anodized in alkali solution. Patterns of two alloys were studied at original/anodized condition. And then, aluminum alloy and Ti alloy plates were assembled into a sample with FM 94 film adhesive. Fatigue crack behaviors of the sample were investigated under condition of nominal stress σ = 36 MPa and 54 MPa, stress ratio of 0.1. Testing results show that anodization treatment modifies alloys surface topography. Ti alloy bonding to Al–Li alloy plate effectively retards crack growth than that of Al–Li alloy plate. Fatigue life of sample bonded with Ti alloy strap improves about 62.5% than that of non-strap plate.

A new type of aluminum lithium alloy Al-Li-S-4 was investigated in this paper. Process of phosphoric acid anodization and method of making bonding joint sample was introduced. Micrographs of plate surface were study by scanning electron microscopy. The pattern of aluminum alloy was modified after anodization. Plates were bonded with FM94 film adhesive and cured at 121°Cin the special clamping fixture. Morphology of bonding sample cross-section interface was investigated after bonding and curing process.

In order to study the similarities and dissimilarities between creep and stress relaxation behavior of age formed aluminum alloys, both creep ageing and stress relaxation ageing experiments have been conducted with plate shaped 7055 aluminum alloy specimens on the 100 KN tensile testing machine performed at 120 °C for 20 h, under different stress levels from 190.0 to 357.8 MPa. The experimental results show that similar variation trends for creep and stress relaxation behavior were observed. Both creep and stress relaxation curves can be divided into two stages. During the first stage, higher creep rate and stress relaxation rate occur, which increase with stress levels but decrease with ageing time. While during the second stage, both the creep rate and the stress relaxation rate reach its lowest value and keep constant. A set of unified creep ageing constitutive equations has been developed and calibrated from creep experimental data, which can be used to predict the creep strain under age forming conditions perfectly. But the experimental results from stress relaxation ageing tests cannot be predicted with the established creep ageing constitutive equations, which shows that there is not a one-to-one correspondence between creep and stress relaxation, creep deformation is the most important but not the only reason for stress relaxation under age forming condition.

The effects of process parameters on evolution of microstructures of 7055 aluminum alloy in creep age forming were studied and the microstrucures were analyzed using transmission electron microscopy (TEM). Some important results are obtained: with the increasing of ageing time, the size of platelet shaped (known as Guinier-Preston (G-P) zones) precipitates and spherical shaped η' precipitates increased, the number of platelet shaped precipitates increased too, while the number of η' precipitates decreased; the precipitates with almost the same size distributed continuously and uniformly along the grain boundary with quite narrow precipitate free zones (PFZs) at 5 hours of ageing time, when the ageing time increases to 8 hours, the distribution of the precipitates along the grain boundary becomes discontinuous and the PFZs gets wider, while with the further increasing of the ageing time, the precipitates distributed continuously again along the grain boundary and the PFZs become more wider. From comparison of stress-aged alloy to stress-free-aged alloy, it was found that after 20 hours ageing, the precipitates in the stress-aged alloy are slightly coarser and the PFZs are wider, the density of retained η' is lower with the development of η phase.

This paper treats the vibration of slender suspension footbridges caused by eccentrically distributed walking dynamic loads. A suspension footbridge model with reverse profiled cables in both the vertical and horizontal planes was used in this conceptual study, while SAP2000 package is adopted in the numerical analysis. The dynamic behaviour of slender footbridges under walking dynamic loads is simulated by resonant vibration caused by synchronous excitations. It is found that slender suspension footbridges with shallow cable profiles often have coupled vibration modes such as coupled lateral–torsional or coupled torsional–lateral modes. When these coupled vibration modes are excited by walking pedestrians, excessive lateral vibration can be induced. Results also show that the effects of the reverse profiled cables on the dynamic performance in different vibration modes are complex. Reverse profiled cables in the horizontal plane can significantly suppress the lateral vibration in coupled lateral–torsional modes, but slightly increase the lateral vibration in coupled torsional–lateral modes.

A cable-supported footbridge model with pre-tensioned cables in vertical and horizontal planes is proposed to investigate the vibration characteristics of shallow suspension footbridges under walking dynamic loads in this conceptual study. In this bridge model, the tension forces in the supporting cables can be adjusted by introducing pre-tensions to the reverse-profiled cables, and therefore the natural frequencies can be altered to cover the frequency range of dynamic forces induced by pedestrians. In the numerical analysis, SAP2000 is adopted to study the vibration properties and dynamic response under walking loads. The synchronous response of the bridge structure is stimulated by resonant vibration. The crowd walking loads are modelled as uniform loads acting on the whole bridge deck and they consist of three parts: vertical dynamic force, lateral dynamic force and vertical static force. Numerical results show that for a shallow suspension footbridge the lowest frequencies correspond to lateral and torsional vibration modes which are always combined together and become two types of coupled modes: coupled lateral–torsional modes, as well as coupled torsional–lateral modes. As an example, a bridge model with fundamental frequency of 0·75 Hz in the lateral direction has been studied. It is found that the vibration in the lateral direction is quite different from that in the vertical direction and that damping has significant effect on the vertical vibration but small effect on the lateral one. Moreover, vertical static load has significant effect on the lateral vibration when the bridge structure vibrated in coupled modes.

Cable supported structures offer an elegant and economical solution for bridging over long spans with resultant low material content and ease of construction. In this paper, a model of shallow cable supported footbridge with reverse profiled pre-tensioned cables is treated and its load deformation characteristics under different quasi-static loads are investigated. Effects of important parameters such as cable sag and pre-tension are also studied. Numerical results performed on a 3D model show that structural stiffness of this bridge (model) depends not only on the cable sag and cross sectional areas of the cables, but also on the pre-tension in the reverse profiled cables. The tension in the top supporting cables can be adjusted to a high level by the pre-tension in the reverse profiled bottom cables, with the total horizontal force in the bridge structure remaining reasonably constant. It is also evident that pre-tensioned horizontally profiled cables can greatly increase the lateral horizontal stiffness and suppress the lateral horizontal deflection induced by eccentric vertical loads.

Cable supported structures offer an elegant and economical solution for bridging over long spans with resultant low material content and ease of construction. These structures, however, tend to be slender and flexible as the structural stiffness depends mainly on the suspending cables. In this paper a cable supported bridge model with pre-tensioned reverse profiled cables is proposed to carry out a conceptual study on the free vibration characteristics of shallow suspension pedestrian bridge structures. Effects of some structural parameters such as cable sag, cross sectional area, applied mass and pre-tensions in the reverse profiled cables have been investigated. Numerical results show that for cable supported bridges with shallow sag the lowest frequencies correspond to lateral and torsional vibration modes which are always combined together and become two types of coupled modes: coupled lateral–torsional modes, as well as coupled torsional–lateral modes. The effects of structural parameters are complex and the natural frequencies can be altered by introducing different pre-tensions in the reverse profiled cables.

A huge amount of research in academia and industry has focused on the hardware and technological side of information systems, while the role of emotions in the way these systems are utilized has been largely neglected. However, recent developments in other disciplines have suggested that emotions play a significant role in decision-making. To address this state of affairs, this study draws upon hypotheses from environmental psychology; specifically, that users' tendencies to approach or avoid environments are modeled on the basis of user reaction to the information load of a virtual environment and the emotions that such an environment elicits. A field experiment was conducted in which users visited popular shopping websites. The work demonstrated how information load and emotions influence virtual exploratory and shopping decisions.

A procedure incorporating the finite strip method and a spring system has been developed and applied to treat the dynamic response of plate structure resting on an elastic foundation to moving loads. The response to a single moving concentrated load is first investigated and then the effects of velocity, elastic foundation stiffness, moving path, and distance between multiple moving loads are studied. The response under a moving harmonic load with constant velocity is finally treated and the effect of the load frequency is investigated. Results indicate that the foundation stiffness and the velocity and frequency of the moving load have significant effects on the dynamic response of the plate and on resonant velocities. Some of these findings might find use in practical applications.

A procedure incorporating the finite strip method together with spring systems is proposed in this paper for treating plates on elastic supports. The spring systems can simulate different elastic supports, such as elastic foundation, line and point elastic supports, and also mixed boundary conditions. To illustrate the application of this procedure, two numerical examples are presented. A three-span simply supported plate is first considered and the effects of support stiffness on the static and free vibration responses and on the critical buckling stress are discussed. A plate resting on Winkler elastic foundation is next studied and the effects of dimension ratio on the static and free vibration responses are discussed. Numerical results show that the spring system can successfully simulate different kinds of elastic supports.

In this research work, a procedure incorporating the finite strip method, together with a spring system has been developed and applied to treat the response of rectangular plate structures resting on elastic foundation. The dynamic response to moving accelerated point loads is investigated and the effects of initial moving velocity, acceleration and initial load position on the response are discussed. Results indicate that the initial velocity and acceleration have influence on the dynamic response. Response of the plate away form the boundaries resembles that of an infinite plate and might have practical applications.

This article documents an effort to experimentally examine the effects of information characteristics of Web shopping sites on consumers' desire to approach the sites. A field experiment was conducted in which respondents visited shopping sites characterized by varying levels of information load. Two dimensions of information load, complexity and novelty were identified and were found to have differential effects on the desire to approach shopping sites. The novelty dimension kept consumers exploring the shopping sites, whereas the complexity dimension has the potential to induce impulse purchases. Managers are advised to design their virtual shopping environments in line with their marketing objectives. Novelty is the key to successfully shaping attitudes, delivering content and soliciting responses, whereas complexity encourages on-line transactions. Future research directions for information academicians are suggested to formulate alternative models for on-line exploration behavior and to develop better measures for on-line informational environments.

In view of high-precision requirements for synchronism measurement of huge die forging press, using grating detection technology, the sensors' installation devices of active connection is designed to minimize the incline of moving beam on the impact of measurement accuracy. The analysis models of beam position detection devices are established by Adams, and comparative analysis of two types of detection devices based on the simulation result, providing some references for the follow-up detection and control strategy design through a comprehensive error analysis. The test indicates that the system finishes the synchronism measurement of moving beam in it's full path, and the measuring precision can be reached 0.002 percent radian.