Materials Science Forum Vol. 982

Abstract: Study on microstructure appearance of 3 mm thick TC4 titanium alloy welded join by common electron beam and pulsed electron beam were carried out. Experimental results show that pulsed electron beam improved grain size and decreased the cooling velocity of weld metal by oscillation and fast cooling effect, the acicular martensite decomposes β phase and transforms to finer and more α′ phase, which shows an interwoven pattern.

Abstract: This paper mainly investigated the revolution of residual stresses and dimension stability in high-precision components during thermal-mechanical processes. Especially, originate of residual stress and its influences on dimension stability, from each step of the design and manufacture processes to thermal-mechanical processes, as well as their complicated interactions were elucidated in detail. Finally, the recent progress of modern analytical and computational techniques were discussed to provide possibilities to quantitative predict and control residual stresses and dimensional stabilities in high-precision components.

Abstract: It is the hot point of the present study to obtain the metal titanium by using the carbon-titanium-oxygen electrolysis. The electrical conductivity, melting point and hardness of C-Ti-O have great influence on the feasibility of electrolysis process. In this paper, the conductivity of rutile titanium dioxide, carbon replacement solid solution (20%, 50%, 80%) and titanium carbide are calculated by first principles. It was found that the more carbon substituted rutile titanium dioxide, the better its conductivity. The electrical conductivity of objects are changed from semiconductors to good conductors. The experimental results show that the conductivity of the experimental results is higher than that of the calculated ones, which may be due to the existence of a large number of hole-excited elements.

Abstract: With the increasing requirements for steel quality, the refining conditions are increasing strict. The high-speed movement of molten steel under mechanical or pneumatic agitation can uniform the temperature and composition, and accelerate the collision of the inclusions to eliminate. However, the electromagnetic field has an important influence on the removal of inclusions in steel and the corrosion of refractory materials. The magnetic phenomenon caused by the movement of molten steel needs to be explored. Considering the complexity of high temperature thermal simulation, this work adopted the physical modeling combined with mathematical simulation method, saturated sodium chloride solution was selected to simulate molten steel as a liquid electrolyte, the magnetic phenomenon caused by solution motion was tested and analyzed, and mathematical model of solution motion magnetization was based on discharge mechanism and magnetic vector potential superposition principle, then the variation law of spatial magnetic field generated by liquid electrolyte flow was discussed. The results show that the simulation results agree with that of the physical modeling, and the mathematical model is promising for prediction of the magnetic field generated by liquid electrolyte flow. Under a constant flow speed of 2000 r/min, a magnetic field with magnetic flux density up to 0.15 Gs was produced, which has a significant effect on the refractory corrosion and removal of impurities in the molten steel.

Abstract: An experimental investigation on square and circular high-strength concrete short columns confined with aramid fiber-reinforced polymer (AFRP) sheets was conducted in this study. Fiber Bragg grating sensors have been applied successfully in monitoring of the strains of the AFRP-confined square and circular concrete columns. The experimental results demonstrate that two types of axial force-strain curves were observed depending on the form of the column. Results show fiber Bragg grating sensors have good repeatability and the ultimate load of the circular concrete column is larger than that of the square concrete column. The interlaminar strains of AFRP and high-strength concrete have also been attained. It helps to analyze the constraint effect of the concrete column and compute the ultimate load of the square and circular concrete column.

Abstract: Cellular automata can be used to analyze a physical system which is satisfying differential equations. A cellular automata program for a thermal analysis of hydration heat was developed. Based on the fundamental theory of cellular automata, the heat conduction equation was deduced for validating the cellular automata approach. By introduction of the concept of equivalent time, the variation of the chemical reaction rate of hydration heat with temperature was studied by use of the Arrhenius function. The relationship between the adiabatic temperature rise and equivalent time was determined by analyzing testing data．A parametric analysis of ambient temperature and concrete slab thickness was also conducted. The temperature rise of concrete increases with increasing ambient temperature and thickness of the slab.

Abstract: Bamboo is a prospective biomass fuel due to its high heating value and growth rate. The addition of kaolin is necessary in the thermal conversion of biomass to increase its ash fusion temperature (AFT), thus reducing fouling and corrosion of the combustion system. This study evaluates the feasibility of utilizing bamboo-kaolin co-processing residue for geopolymer synthesis. Thermochemical calculations suggest that bamboo culm ash liquidus increases by 15% by adding kaolin during combustion at a biomass to kaolin mass ratio of 95:5%. A 2³ full factorial experiment measures the effect of activator Na₂SiO₃:KOH ratio, KOH concentration, and heat-curing period at 60 °C on the early strength of geopolymer mortars. Co-processing residue of bamboo-kaolin at a mass ratio of 95:5% produces geopolymer mortars with compressive strengths in the 10.7-40.3 MPa range. ANOVA treatment of the data indicate strong positive effect of KOH concentration. Crystalline phase characterizations indicate that the co-processing is able to convert kaolin to the amorphous, more reactive metakaolin. A shift in the IR absorption band from 1034 to 1008 cm^-1 is attributed to the conversion of Si-O-Si bonds of the co-processing residue into Si-O-Al and Si-O-K bonds of the geopolymer gel phase. These results suggest the feasibility of geopolymerization as a waste valorization pathway to ensure the sustainability of the biomass-based energy production.

Abstract: Nanotechnology has contributed significantly to different subfields of the construction industry, including asphalt pavement engineering. The improved properties and new functionalities of the nanomaterials have provided different desired properties of asphalt. In this study, the effectiveness of multi-walled carbon nanotubes (MWCNT) in resisting the oxidation of polymer-modified asphalt was measured. A total of three different percentages (0.5%, 1%, and 1.5%) of MWCNT were used to modify the Styrene-Butadiene (SB) and styrene–butadiene–styrene (SBS) modified asphalt (4% and 5%). The laboratory oxidized asphalt samples were evaluated by an atomic force microscopy machine. The oxidation of the polymer-MWCNT modified asphalt is measured by simulating the existing functional group of the asphalt and as a function of the adhesive force. It is observed that the use of MWCNT in SB and SBS can increase the resistance to oxidation.

Abstract: In this paper, the experimental study on the pultruded fiber-reinforced polymer (pultruded FRP) angle beams subjected to transversely eccentric load are presented. A summary of critical buckling load and buckling behavior for full-scale flexure tests with various span-to-width ratios (L/b) and eccentricities are investigated, and typical failure mode are identified. Three-point flexure tests of 50 pultruded FRP angle beams are performed. The E-glass fibre/polyester resin angle specimens are tested to examine the effect of span-to-width ratio of the beams on the buckling responses and critical buckling loads. The angle specimens have the cross-sectional dimension of 76x6.4 mm with span-to-width ratios, ranging from 20 to 40. Also, four different eccentricities are investigated, ranging from 0 to ±2e. Eccentric loads are applied below the horizontal flange in increments until beam buckling occurred. Based upon the results of this study, it is found that the load and mid-span vertical deflection relationships of the angle beams are linear up to the failure. In contrast, the load and mid-span lateral deflection relationships are geometrically nonlinear. The general mode of failure is the flexural-torsional buckling. The eccentrically loaded specimens are failed at critical buckling loads lower than their concentric counterparts. Also, the quantity of eccentricity increases as buckling load decreases. In addition, it is noticed that span-to-width ratio increases, the buckling load is decreased. The eccentric location proved to have considerable influence over the buckling load of the pultruded FRP angle beams.