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A major limitation in chemisorptive hydrogen storage in metal hydrides is the long time required for the adsorption reaction during charging. This study investigates how the shape and material of the reaction chamber influences the adsorption and desorption rates. Numerical simulations of hydrogen storage in a cylindrical reaction chamber filled with LaNi5 hydride are conducted for a range of chamber thermal conductivities and aspect ratios. The results show that adsorption and desorption processes are limited by thermal diffusion in the hydride bed and storage chamber. A storage efficiency is proposed based on an ideal isothermal process and used to evaluate the impact of chamber thermal conductivity and aspect ratio on the adsorption and desorption rates. Empirical correlations are proposed for predicting the adsorption and desorption efficiency of cylindrical LaNi5 hydride beds. Finally, a machine-learning based data model for predicting storage efficiency in metal hydride chambers is presented. Comparison against the empirical correlations highlights that the machine learning-based data model can predict the storage efficiency more accurately.

The charging and discharging times are some of the very important factors for the design of highly efficient hydrogen storage chambers with metal hydrides or activated carbon. However, experimental research or numerical simulations have to be performed to determine these factors, which could be time consuming and expensive. In this study, the possible existence of a general time scale for hydrogen storage chambers with large amount of sorption heat is discussed. By scale analysis of the energy equation and rapid heat generation and slow cooling assumption, it is found that there likely exists a general time scale for hydrogen charging and discharging. The time scale is determined as the thermal diffusion time scale of the porous storage bed. Its validity is demonstrated by comparing with the available metal hydrides and activated carbon data in previous literature. Furthermore, a minimum bed thickness scale for a specific charging time is also derived according to the developed general time scale. The proposed temporal and spatial scales may serve as a low cost and efficient tool for the design and optimization of hydrogen storage devices with metal hydrides or activated carbon.

This study presents numerical modeling and simulations of thermal fluid flows in high-volumetric-density metal hydride beds during hydrogen (H2) adsorption and desorption within the lattice Boltzmann method (LBM) framework. A novel LBM is developed for predicting the flow and conjugate heat transfer in a practical lab apparatus involving a combination of solid chamber, free expansion zone, and porous media metal hydride that have not been addressed to date. With a correction term in the collision operator and a new equilibrium distribution function, the present model has a consistent expression of the heat capacity ratio for different fluid regions and derives the correct form of macroscopic energy and generalized momentum equations (including Darcy, Brinkman, and Forchheimer terms). The model is then validated through comparisons of the simulated results with previous experimental data under different initial pressure and temperature conditions for LaNi5–H2 storage systems as well Mg–H2 reactors, achieving excellent agreement. In addition, accounting for conjugate heat transfer and other porous forces in the present LBM yields improved predictions over prior numerical approaches.

Aiming to investigate the propagation behaviour of distortion-induced fatigue cracks in steel bridge web gaps, multi-scale numerical analysis models were built based on fracture mechanics theory an...

Fatigue and corrosion damage in existing old steel bridges are accumulated continuously in service stage, probably leading to structural failure. One old welded steel bridge and one old riveted ste...

This work aims to combine the effects of the near-wall and core flow disturbance by proposing novel wing-shaped turbulators. The new turbulators are fabricated with the fused deposition modeling (3D printing) technology. To explore their effects on detailed flow fields, local temperature distributions, and pressure drops in a two-pass square channel, particle image velocimetry (PIV), infrared thermography (IR camera), and pressure transducer measurements are performed. The turbulator pitch, clearance, and truncation gap ratio based on the channel hydraulic diameter of 45.5 mm are, respectively, fixed at 0.7, 0.25, and 0.06. Varied parameters include turbulator attack angle (α = 10 deg, 15 deg, 20 deg, and 30 deg), maximum thickness to chord line ratio (t/C = 0.08, 0.13, 0.16, 0.20, and 0.23), and bulk Reynolds number (Re = 5000–20,000). From the experimental results and flow parameters analyzed, the dimensionless spanwise-averaged mean transverse velocity and cross-sectionally averaged vorticity magnitude are identified to be the most relevant ones to spanwise-averaged local Nusselt number ratio in the first and second pass. Among all examined cases and previous data with Fanning friction factor ratio (f¯/fo) less than 50, the case with α = 20 deg and t/C = 0.20 attains the highest thermal performance factor (TPF) and overall Nusselt number ratio Nu¯/Nuo up to 1.68 and 5.36, respectively. Furthermore, empirical correlations of Nu¯/Nuoandf¯/fo versus α, t/C, and Re are proposed.

Ultra-high performance fiber reinforced cementitious (UHPFRC) and composite reinforcement techniques have great potential in achieving efficient structural resistance recovery and overall ...

In this study, a new thermal lattice Boltzmann model (TLBM) is developed to simulate conjugate heat transfer in a microchannel heat sink (MCHS) with porous ribs and pulsatile flow inlet. The examined parameters include the rib to channel height ratio ( H r * ), Strouhal number (St), and Reynolds number (Re), which are varied from 0.25 to 0.75, 0 to 3.2, and 100 to 300, respectively. The proposed TLBM is based on the double distribution function framework and capable of addressing heat transfer in combined fluid and porous media conditions. The simulation data show that the flow pulsation inside MCHS with porous ribs not only improves the bulk mean temperatures but also eliminates the rib recirculation zones at some phases, which promotes both the local and overall heat transfer. For fixed Re, the overall Nusselt number ( N u ‾ / N u 0 ) and Fanning friction coefficient ( f ‾ / f 0 ) increase and then decrease with increasing St. The maximum values appear at St = 2. For fixed Re and St, the thermal performance factor (TPF) displays a single peak trend with H r * and the optimal TPF of 2.2 occurs at H r * = 0.5 . In addition, compared with the previous ribbed, baffled, and porous MCHSs, the proposed porous rib design under pulsating conditions reports the highest N u ‾ / N u 0 of 13.4 in the range of f ‾ / f 0 ≤ 200 . Finally, the correlations of N u ‾ / N u 0 and f ‾ / f 0 with Re, St, and H r * for the present MCHS are established for the first time, with average differences below 6.7% and 12.4%, respectively.

The topic of compact micro heat exchanger is one of the most active areas in heat and mass transfer research today. However, there is a lack of literatures on serpentine channels with parallelogram cross-section. This article provides numerical study of the hydraulic and thermal performance in parallelogram serpentine channels with aspect ratios (α) ranging from 0.25 to 4 and wall included angles (θ) ranging from 45° to 90°. The Reynolds number (Re), characterized by channel hydraulic diameter and mean bulk velocity, is varied from 100 to 300. Their influences on the fluid flow and heat transfer characteristics are investigated under constant wall temperature condition. It is newly found that Nusselt number (Nu) distributions on bottom and top walls in slant wall channels (θ ≠ 90°) are asymmetric and there exists a critical value of α and Re for Nu and Fanning friction factor (f), respectively. Furthermore, two new correlations for overall Nu and f with respect to α, θ, and Re are proposed for laminar flow in parallelogram channels, with maximum errors less than 10% and 20%, respectively, compared with numerical results.

Numerical studies of laminar forced convective heat transfer and fluid flow in a 2D louvered microchannel with Al2O3/water nanofluids are performed by the lattice Boltzmann method (LBM). Eight louvers are arranged in tandem within the single-pass microchannel. The Reynolds number based on channel hydraulic diameter and bulk mean velocity ranges from 100 to 400, where the Al2O3 fraction varies from 0 to 4%. A double distribution function approach is adopted for modeling fluid flow and heat transfer. Code validations are performed by comparing the streamwise Nusselt number (Nu) profiles and Fanning friction factors of the present LBM and those of the analytical solutions. Good agreements are obtained. Simulated results show that the louver microstructure can disturb the core flow and guide coolant toward the heated walls, thus enhancing the heat transfer significantly. Furthermore, the addition of nanoparticles in microchannels can also augment the heat transfer, but it creates an unnoticeable pressure loss. With both the louver microstructure and nanofluid, a maximum overall Nu enhancement of 7.06 is found relative to that of the fully developed smooth channel.

A low-cost lumped parameter model (LPM) is developed to simulate hydrogen storage in solid-state materials. The proposed LPM is a zero-dimensional model based on an analogous transient thermal resistance network that considers the whole storage system as a resistor–capacitor (RC) circuit with a current source. Combined with the mass conservation, sorption kinetics, and equation of state, the LPM is capable of predicting key thermofluidic quantities of the storage system, such as the storage bed temperature and pressure, hydrogen fraction and flowrate, and storage tank temperature. To test the applicability of the LPM, chemisorptive (Mg and LaNi5) and physisorptive (activated carbon) solid-state materials are simulated for adsorption and desorption processes. For both material types, LPM achieves predictive accuracies comparable to three-dimensional computational fluid dynamics (CFD) simulations, especially for hydrogen fraction and storage times (with maximum errors less than 9.6%), for a fraction of the computational cost (23,734 times lower memory requirement and 126 times faster calculation time). In addition, several formulations of the bed thermal resistance are proposed and discussed in terms of their impact on the accuracy of the LPM predictions. For slender cylindrical tanks, an equivalent annulus formula achieves the best balance of simplicity and accuracy.

In this study, a thermal lattice Boltzmann model (TLBM) is developed for heat transfer in arbitrary combinations of solid, fluid, and porous media. The velocity and temperature field are modeled through a double distribution function (DDF) approach. By introducing a new temperature equilibrium DF, the present TLBM not only recovers the correct macroscopic energy equation via Chapman–Enskog expansion but also possesses a consistent definition of heat capacity ratio which is lacked in previous thermal models. To validate the proposed method, four benchmark cases are tested, including the heat conduction in dual heterogeneous media, Couette flow in partially porous channel, natural convection in a porous cavity, and natural convection in a partially solid and porous cavity. Good agreement is attained, which shows the applicability of the present model for simulating thermal flows in combined solid, fluid, and porous media conditions.

Normal 0 false false false EN-US X-NONE AR-SA /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";}Nanocrystalline cupric oxide (CuO) film was prepared by sputtering of pure copper metal on n-type single crystalline Si substrate under argon-oxygen ambient. Structural and morphological analyses of the as-deposited CuO films were performed by X-ray diffraction (XRD) diffractometer and Field Emission Scanning Electron Microscopy (FESEM). The results show Single crystalline granular nanocrystalline (002) CuO films, with 18 nm crystallite size. Current-voltage (I-V) and capacitance-voltage (C-V) measurements were performed for p-CuO/n-Si hetrojunction. Diode parameters such as saturation current (Is=9.5E-6 A) and ideality factor (n=1.86) were extracted from the dark I-V characteristics. Potential barrier height of the junction (ϕi=1.1V) was revealed from (1/C2- V) plot. Normal 0 false false false EN-US X-NONE AR-SA /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";}

It is well-known that TiO2is an environmental benign photocatalyst which can be used to decompose harmful organic compounds. Recently, many studies are concentrated on the purification of industrial wastewater due to the requirement of environmental protection. In present study, TiO2nanomaterials supported by fine zeolite particles have been used as the photocatalyst to purify the oily wastewater. It has been found that the oil concentration in the modulated water can be reduced significantly and rapidly under the action of photocatalytic degradation and the ultraviolet light radiation. After 80 minutes, oil concentration in the modulated water can be reduced by more than 80%. The results suggest that TiO2nanomaterials supported by fine zeolite particles are effective material for purification of oily wastewater. In addition, the present results show that the efficiency of water purification can be significantly increased by use of mechanical stirring during the photocatalytic degradation process.

Daqing oilfield ASP flooding drive target gradually changes from the first reservoir to the second and third reservoir,which leads to the unequal of the reservoirs producing extent, and seriously affects the developing for ASP flooding molecule weight. On the basis of that, we optimum the Molecule Weight Adjusting Mechanism of low permeability reservoir, and use the method of control variables to change the nozzle angle of diffuser section, cylinder length, diffuser angle, nozzle angle to establish 81 models. At the same time, we simulate flow field characteristics of these models with the help of Fluent. Ultimately, the models of low pressure drop and high stick loss rate could be found. Through analyzing and contrasting large of models, we found that shrinkage angle is 30 degree models under the same pressure drop condition the stick loss rate relativity high. Simultaneously, these models are suitable for the field requirements, and can provide theoretical basis for molecular weight adjusting and optimizing structure.

In this paper, fatigue damage and life prediction of laser lap joints were investigated based on natural frequency as the damage variable. At each fatigue stage, damage degree of laser welded specimen was monitored by the fatigue test and dynamic response tests. The results show that in the fatigue process during the increase in the number of fatigue cycles, each order natural frequency of test specimen decreased at different rate. There was almost no damage before the number of cycles reached 60% of the fatigue life, and then cracks began to initiate. When the number of cycles reaches 80% of the life, macroscopic cracks appeared and the predicted damage degree reached to 50%. Based on relation between the change rate of the natural frequency and the fatigue damage, a new fatigue life prediction model was established. The results from experimental tests were consistent with the fatigue life prediction model.

Resistance spot welding (RSW) is being taken place by partial lap laser welding for the poor surface quality and bad airtight due to the pressure of electrodes. The shape of partial lap laser welding is similar to the vase. When the penetration of the joint is in a certain range, there is no welding trace on the outer surface. Laser welding temperature field numerical analysis based on Abaqus finite element analysis software is committed to obtain a suitable range of process parameters to improve production efficiency and automation by determining the joint penetration. To master the laser lap welding of stainless steel weld penetration state, the combination of three-dimensional positive cone + three-dimensional inverted cone + half-ellipsoid heat source model was established simulating stainless steel lap laser weld pool shape and forecasting the range of process parameters .

A new steel-concrete composite girder which is an I-shaped girder with concrete-filled rectangular tubular flange was proposed in this paper. The web depth of the new composite girder is reduced, and lateral torsion buckling stiffness is improved, which can increase the buckling capacity of the girder. In order to study the bending capacity of concrete-filled rectangular tubular flange composite girders (CFRTFCG), the static tests of CFRTFCG with flat and corrugated webs under concentrate lateral loads had been performed. Based on the test results, the bending limit load capacity and mechanical behavior of the specimens were obtained, the bending failure mechanisms of CFRTFCG were also summarized.

This paper evaluates the shear resistance of hybrid I-beams fabricated by high performance steel and conventional steel. A number of hybrid I-beams are modeled and analyzed to determine their shear failure mechanism characteristics, considering parameters of web slenderness (hw/tw), frame action from end-stiffeners, ratio of flange width to web depth (bf/hw) and panel numbers. The analyses conclude that, in shear resistance calculation, plate beam with inter and slender webs often fail in inelastic or elastic shear buckling while ultimate shear resistance of compact webs is given by the shear strength of the material. What’s more, more rigid stiffeners provide more fixity to flange plates and increase the post-buckling resistance of plate beam. For plate beam with several panels, the shear stress at the ultimate load is similar. Finally, the I-beams with larger flange width to web depth ratio would develop larger shear strengths and then shear deformation cause formation of plastic hinges.

In order to study the bending capacity of steel and concrete composite girder with concrete filled tubular flange (SCCGCFTF), a formula for the ultimate bending capacity of normal section was proposed based on perfected elastic-plastic model for steel and restricted concrete model for inner high performance self-compacted concrete. Analysis result shows that the mechanical behavior under static load can be divided into two phases in accordance with confining effects. Confining effects strength of the concrete-filled steel tube flange was relation to the restriction effect coefficient ξ. The ratios of the calculated value to the experimental ultimate bending capacity were between 0.93 and 0.97. Therefore, the theoretical formula is relatively safe to calculate the ultimate bending capacity.

In order to improve the laser-induced breakdown spectroscopy for low-level elements testing capability, the enhancement effect of CsCl additive on the emission spectra of soil samples was studied. The laser spectrum analytical system is composed of a high-energy neodymium glass laser used for abating samples, a multifunctional and automatic grating spectrometer, and a CCD data acquisition system used for recording plasma spectra. The electron temperature and electron density of plasmas were calculated by measuring spectral line intensity and stark broadening, respectively. The experimental results showed that with the increase of the CsCl additive, the intensity, signal-to-background ratio, the electron temperature and the electron density all went up firstly and then down. When 15% CsCl was added, the radiation intensity of plasma reached the maximum value, the spectral lines intensity of element Mn, K, Fe and Ti increased around 383%, 348%, 303% and 267% than that without additive; spectral signal-to-background ratio increased about 204%, 149%, 150% and 142%; while the electron temperature and electron density of plasmas went up 10% and 13%, respectively.

Recently the problems of resistance spot welding (RSW) stainless steel railway vehicles are causing more attention for poor surface quality. Lap laser welding of stainless steel is investigated with OED(Orthogonal experimental designing ) in this study to replace RSW with the aim of to increase the aesthetics of the car body by eliminating visible indentation on the surface and the flatness of the skin reducing welding deformations. After welding tensile tests and microstructure analysis are performed. The optimization of process parameters were: laser power =2.5kW；welding speed=2.2m/min, focal position=0mm. The fusion zone is symmetrical about the axis of the laser beam and no welding cracks or porosity can be found in any of the welds. This work has great significance of improving the manufacturing level of stainless steel railway vehicles.

This paper investigates the flexural strength and ductility of hybrid high performance steel (HPS) I-beams. Three simple supported I-beams were tested to study the bending behavior of hybrid beams with Q&T HPS 485W in flanges and Q235 in webs. Experimentally verified nonlinear finite element modeling techniques were then employed in a parametric study including the influence of cross section compactness and material match in hybrid design on rotation capacity of beams. It is observed that the compactness of flange and web have a major influence on the rotation capacity of flexural beam. As a result, appropriate compactness criteria are suggested for use in the design of HPS 485W hybrid beams employing compact webs made from lower strength steels.

This paper provides an introduction of existing fatigue and fracture behavior studies about high performance steel (HPS). This paper is emphasis on the crack propagation studies of HPS 485W, which is a new kind of structural weathered steel produced by Wuyang Steel Company using quenching and tempering (Q&T) in China. HPS has more advantages than traditional steel, such as high fracture toughness and cracking tolerance, high strength, low preheating weld or no preheating, recycle using and so on, so it can be used in sustainable bridge and building structures with low carbon releasing. To ensure the using safety and extend applying area of the new green civil material, the key material properties of HPS should be studied, such as fatigue crack growth rate. Fatigue crack growth rate characterizes the material resistance to stable crack extension under cyclic loading. A set of 5 compact specimens were made from 8mm and 14mm thick HPS 485W separately. Fatigue crack growth rate function of crack-tip stress-intensity factor range, da/dN versus ΔK, is proposed based on the test results, which shows HPS has high cracking tolerance ability.

This paper gives a brief introduction of the developmental history of high performance steel (HPS) all over the world. Emphasis of current paper is on the characteristic studies of HPS 485W, which is new structural weathered steel produced by Wuyang Steel Iron Company using quenching and tempering (Q&T) in China. To obtain the strength and ductility of HPS 485W, the tensile coupons were machined from each 8mm, 10mm, 12mm and 14mm thick plate. Based on the static tensile tests in room temperature, major of material mechanical characters were obtained, such as yield strength, ultimate strength, elastic modulus and so forth. Besides, to examine plate toughness, 30 Charpy V-Notch (CVN) specimens from 12mm thick HPS 485W plate were tested from 20 oC to -196 oC . Compared with conventional bridge steels, the CVN test results show that the fracture toughness of HPS 485W is much higher, and the brittle-ductile transition of HPS occurs at a much lower temperature. A set of 9 single-edge bend specimens were took from 20mm and 30mm thick HPS 485W separately for ductility fracture toughness test. The calculated JIC value is 415.8 kJ/m2 for 18mm thick specimen and 507.79 kJ/m2 for 28mm thick specimen, which shows ideal ductility of HPS 485W.

We have studied the high-pressure and high-temperature behaviour of calcium fluoride (CaF2) using molecular dynamics simulations with the Born-Mayer-Huggins potentials. The thermal (pressure-volume) equation of state, radial distribution functions (RDFs) just nearby the melting temperature, isothermal bulk modulus, and volume thermal expansion coefficients were calculated from the isobaric and isothermal ensemble. Structural and thermodynamical properties at ambient temperature were well reproduced for the cubic fluorite-type phase of CaF2. At an extended pressure and temperature ranges, the thermal expansivity and bulk modulus of CaF2 have also been predicted. The RDFs indicated that the melting temperature is bracketed between 1600 and 1700 K, and the thermodynamic properties of CaF2 with fluorite-type cubic structure are investigated in the pressure range 0–95 kbar and temperature up to 1600 K.

The current stainless steel railway vehicles body and structure are usually assembled by resistance spot welding process. The weak points of this process are the poor surface quality and bad airtight due to the pressure of electrodes. In this study, the partial penetration lap laser welding process was investigated to resolve the problems. The effects of the laser welding process parameters such as laser power, welding speed and focused distance to the shape of the weld seam and the shear tensile strength were discussed to find the optimal parameters. And the mechanical tests and microstructure analysis were also taken in this study. The optimal parameters are P=2.0kW，S=22mm/s，F=0mm. This work has great significance of improving the manufacturing level of stainless steel railway vehicles.

Ultra-high performance fiber reinforced concrete (UHPFRC) is an optimal selection for bridge strengthening projects, because of the distinguished material properties like high compressive and tensile strengths, ductility, durability, compactness, and low creep. This paper focuses on a strengthening method for both steel bridges and concrete bridges using UHPFRC. For steel bridges, UHPFRC overlay is proposed to strengthen orthotropic steel bridge decks. The UHPFRC layer acts in composite action with the steel deck plate by applying an epoxy resin glue at the interface of the two materials, which is verified to be an effective way to improve structural rigidity by means of experiments. For concrete bridges, UHPFRC layer is cast on the top surface of the deck slab. This technology has already been applied to several bridges as waterproofing layer and to effectively increase the ultimate resistance of the deck slab of bridges. Besides, for the bottom flange of concrete girders in the tensile state, UHPFRC and steel composite strengthening method is proposed. Studs are anchored in the bottom flange of the original concrete girder and a U- shaped steel plate with studs is arranged such as to cover the bottom flange and part of the web. This U- shaped steel plate also serves as a formwork for UHPFRC casting between original concrete girder and steel plate, such that an overall cross section is formed and the UHPFRC-steel plate strengthening part work in composite action with the original girder. A concrete bridge box girder section is selected as a case study to validate the UHPFRC strengthening method for both steel and concrete bridges with the objective to improve structural performance effectively.

Concrete bridges often have damages after opening to traffic for several years, it is necessary to reinforce the bridges in order to ensure the safety and extend the service life of the bridges. The steel plate and concrete composite strengthening (SPCCS) is a new retrofit technique, it works through welding studs on the reinforcing steel plates, planting steel bars in the original concrete, and casting concrete between the original structure and the steel plates, thus the new and existing concrete can work together. The strengthened structure has the advantages of high bearing capacity, large stiffness and long term durability. In order to investigate the mechanical performance of the strengthened bridge, a full-scale damaged box girder released from an actual bridge was reinforced by SPCCS technique. The bending resistance test was carried out and the test results were analyzed in this article. On the basis of the test, the SPCCS technique was applied to reinforce a damaged bridge. From the field test data, it showed that the bend resistance of the bridge was increased a lot after reinforcement. The SPCCS technique is an effective method to reinforce the concrete bridge, which can help realizing the sustainable maintenance of the bridge.

ZrW2O8 powder was prepared by the solid-state method. A heterogeneous precipitation process was developed to fabricate Cu coated ZrW2O8 composite powders based on a cementation process under 100oC. SEM and XRD were applied to assess the coating quality as well as the phase composition. The result shows that the mean size of ZrW2O8 powders is less than 2 microns. The nanometer compounds are easier formed on the surface of the spheric agglomerated ZrW2O8 powders. The Cu coated ZrW2O8 composite powders can be obtained with flowing hydrogen at 300oC.

A series of thermoplastic polyurethanes was synthesized with varying hard segment composition or content and the effect of the hard segments on morphology and properties was studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA), Fourier transform infrared analysis (FTIR) and tensile testing. The diisocyanates included 4,4' -diphenylmethane diisocyanate (MDI) and 4,4' -dicyclohexylmethane diisocyanates (H,2MDI). The chain extenders 1,4-butanediol, 1,5-pentanediol and 1,3-butanediol were used. The soft segment material was poly(oxytetramethylene) glycol of molecular weight 2000. It was found that the interchain attractive forces between hard segments affect physical properties and morphologies. The degree of phase mixing, hardness and strength increased with increasing hard segment content and with decreasing degree of hard segment crystallinity (packing arrangements) at the same hard segment content.

Dense arrays of micro-columns are formed on the surface of Ti-Al alloy by cumulative nanosecond pulsed laser ablation in water. The fabric-like structure characterized by Ti-Al nano-spheres absorbed on micro-cluster in liquid is most likely responsible for the occurrence of laser micro-etching and localized melting, resulting in continuous deepening of micro-holes and the formation of micro-columns. Laser induced plasma spectroscopy is carried out to reveal the effect of micro-columns on subsequent pulse laser ablation. The intensity of spectral lines from Ti ions by additional laser ablation of the modified spot is higher than that created over a smooth surface. These results suggest that the micro-columns lead to an enhanced absorption of the following laser energy. The proposed results and relevant discussions are of importance for the development of light-trapping coatings on a metal surface.

Cold stiffening of the plate of Orthotropic Steel Deck (OSD) of bridges can be achieved by adding a layer of Ultra-High Performance Fiber Reinforced Cementitious Composite material (UHPFRC) on top of the deck plate by composite design, thus expecting to reduce stresses in fatigue critical details of OSD and avoid fatigue vulnerable welded details at composite interface. This paper focuses on experimental and analytical study for the bending behavior of UHPFRC - steel composite specimens in elastic domain, corresponding to the stress levels of deck plate for in-service steel bridge with OSD. In the total 11 UHPFRC - steel composite test specimens, it was considered UHPFRC with thicknesses ranging from 25 mm to 50 mm, loading configurations simulating sagging or hogging moment region, and different composite designs including materials natural bonding, epoxy-glued interface and epoxy-glued corrugated steel plate shear connector. Epoxy-glued interface was effective composite method leading to stiffness improvement for sagging moment region of OSD and thus decreased stresses in the OSD deck plate. The proposed corrugated steel plate shear connector turned out to be effective for stiffness improvement especially for specimens simulating hogging moment region, indicating that this mechanical connector acted as both shear connector and confined steel bar. The bending processes were analyzed for UHPFRC - steel composite specimens simulating sagging and hogging moment region respectively, especially for the loading stage before attaining 0.5 epsilon(sy) at mid-span section. Based on test and analytical results, design recommendations were given for OSD stiffening by means of UHPFRC. (C) 2020 Elsevier Ltd. All rights reserved.