Materials Science Forum Vols. 704-705

Abstract: A new kind of solar chimney power plant system combining chimney and heat collector was designed. Paraffin was chosen as the material of energy storage layer and the unsteady conjugate numerical simulation of the system was done by Fluent software. The operation condition of the system was simulated when the solar radiation value was changed with time according to the actual situation. Simulation results showed that: with the increase of solar radiation, flow velocity of the air and the maximum output power increased. At twelve o'clock, the air velocity could reach 1.24 m/s and output power was 122W. Due to the energy storage effect of phase change materials, the system had output power of 1.3W at night. Moreover because of the continuous work of the heat storage layer, in the same condition of solar radiation, the air velocity and maximum output power increased with the system operation days extended.

Abstract: Crosslinking density of vulcanized rubber which was filled with carbon black and silica was experimentally researched, and its corresponding heat generation, dynamic lag loss (tanδ) and loss modulus ( E″) were also studied. Based on these tests, the model of the relationship among them was established. The results showed that the characteristic value of crosslinking density Vr almost showed downward trend as a straight line when the quantity of silica increased, but temperature rise, loss modulus E″ and tanδ increased obviously. Silane coupling agent Si-69 could improve the crosslink density and dynamic performance. In the drawing, linear correlation was good in linear fitting between temperature rise and loss modulus, as well as between temperature rise and tanδ. Keywords: vulcanized rubber; crosslingking density; heat generation; hysteresis

Abstract: Mg-10Ho-0.6Zr alloys with different amount of Y additions are prepared by metal mould casting method. The effects of Y content on microstructure, age hardening behavior and mechanical properties are investigated. Results show that all the as-cast Mg-10Ho-xY-0.6Zr alloys are mainly comprised of α-Mg matrix and Mg₂₄(Ho,Y)₅ phase. With increasing Y content, grain size of the as-cast alloys is reduced. Age hardening response, Vickers hardness and mechanical properties are improved with the addition of Y. The maximum ultimate tensile strength (UTS) and yield strength (YS) are obtained in Mg-10Ho-3Y-0.6Zr alloy at peak-aged state, and the values are 215 MPa, 158 MPa at room temperature, and 144 MPa, 126 MPa at 250 °C, respectively. The improvement of the UTS is mainly attributed to the fine distributed quadrate-like β stable phase. Key words: Mg-Ho-Y-Zr alloy; Microstructure; Age hardening behavior; Mechanical properties

Abstract: As a kind of crude and green material, wood is essential to human life. Meanwhile, the amount of water played a vital role to almost all engineering properties of wood. Moisture affects dimensional stability, physical and mechanical properties, and susceptibility toward biological degradation. Consequently, it provides a theoretical basis for the reasonable drying model to explore the water assignment and content in timber. we present here the application of a nuclear magnetic resonance technique, which is used to quantitatively analyse water distribution in wood on the basis of T2. In this paper, we will analyse the water distribution in hardwood on the basis of T2. Refer to the scanning electron micrographs of the hardwood, we can speculate the relaxation time of the water in different cell lumens respectively. Moreover, it is even more important to calculate the organic proportion in wood by the corresponding amplitude of signal derived from the water in different cell lumens. This, compared with a scanning electron micrograph, has allowed us to produce a assumable distribution of water in wood, even the corresponding organic proportion in wood, which allows us to speculate physical and mechanical properties of wood. A mobile NMR probe has been used as a non-destructive and non-invasive tool for water content analysis on wood samples. In this paper, we will adopt NMR methods to explain. This, has opened up a way for the accurate determination of the moisture content of wood, even can be applied to the areas of food and so on. Keywords: Nuclear magnetic resonance; Water distribution in wood; T2; Scanning electron micrograph; Water content

Abstract: Based on extensive literature review, the state of the art of coupled hydromechanical models and in-situ monitoring for groundwater inrush predictions are summarized in detail, based on which, it is proposed that the key issues for describing the seepage characteristics during groundwater inrush are to calibrate the equations for damage-induced evolution of permeability and of effective stress. Depending on in-situ experiments and numerical simulations, a new academic idea, i.e.“the rock micro seismicity induced by mining processes and water pressure disturbance is in essence the index of groundwater inrush” is put forward based on case studies, coupled hydro-mechanical theory, high-performance computing technology and microseismic monitoring. The authors propose that the tendency for analyzing and predicting the groundwater inrush is to synthetically inverse the inrush pathway formation, strata microseismic precursor and high performance computing results. And relying on the microseismic monitoring events, the groundwater inrush models are calibrated, which could be used to clarify the precursory characteristics and to locate the inrush pathway. This study will lay theoretical basis for establishing the models to predict the groundwater inrush in underground mining. Key words：rock mechanics, groundwater inrush models, calibrating, numerical simulation, microseismic monitoring

Abstract: Differential scanning calorimetry was used to study melt and solidification and microstructure of austenitic stainless steels containing boron. The liquidus and solidus temperatures decreased because of the boron content, and boron inhibited the formation of δ-Fe. A large content of eutectic boride structure was detected when the boron content was higher. The boride was M2B, and the crystal structure was orthorhombic. The crystal structure and elemental composition of M2B were investigated in detail by SEM-EDS and XRD analysis.

Abstract: Repeated bending occurs toward the direction of rail head and rail base during the cooling which can lead to significant bending deformation and residual stress after cooling, the longer the rail, the more obvious this phenomenon is. In addition to cooling function, a kind of cooling bed with a pre-bent process will be used in order to solve this problem on 100 meters rail. The synchronous movements on this cooling bed can be realized by the automatic control system after establishing the mathematical model of bending deformation after rolling. The rail is reversely bent toward the rail base before cooling according to the pre-bent control of the pre-bent curve and is straight after cooling which can realize the control of the residual stress after pre-bent and straightening. The straightening residual stress significantly reduced after the pre-bent. Fund: National Natural Science Foundation funded projects （50765004）

Abstract: Cunninghamia lanceolata has been the dominated species of plantation forest in South China. However, the most products made from Cunninghamia lanceolata biomass are lower value added. In order to obtain top value-added products, health function of Cunninghamia lanceolata biomass were studied by TD-GC-MS. Relative content of each component was determined by area normalization. The main 40°С volatiles were 1-propanone, 2-amino-1-phenyl-(14.22%), benzene (11.17%), acetic acid (10.16%), cyclopentanecarboxylic acid, 1-(2-butenyl)-2-oxo-, ethyl ester, (e)-( 7.56%), 1h-cyclopenta [1,3] cyclopropa [1,2] b enzene, octahydro-7-methyl-3-methylene-4-(1-methylethyl)-(6.24%), etc. And the main 60°С volatiles were cedrol (29.65%), acetic acid (12.35%), cyclopentanecarboxylic acid, 1-(2-butenyl)-2-oxo-, ethyl ester, (e)- (7.78%), 1,6-cyclodecadiene, 1-methyl-5-met hylene-8-(1-methylethyl)- (6.11%), etc. So Cunninghamia lanceolata biomass had health function under indoor temperature. Keywords: Health function; Cunninghamia lanceolata; Biomass; TD-GC-MS

Abstract: The experiment of the roll-casting for semi-solid AZ91D magnesium was carried out on the equipment made by ourselves in our laboratory. Parameters of annealing process and the effect of annealing temperature on structure and hardness of semi-solid magnesium were investigated. It was shown that annealing process can improve the structure and properties of roll-casting strips for semi-solid magnesium. In addition, it can relieve the eutectic structure segregation and make β-Mg17Al12 phase precipitate from primary α-Mg grain, which can cause dispersion strengthening process when the annealing temperature is about 420°C. With the increasing of annealing temperature, semi-solid primary α-Mg grain boundary become obscure gradually, grain growth is indistinct and β-Mg17Al12 phase is precipitated from the inner α-Mg grain. However, the aberrated eutectic α-Mg grain for non-equilibrium solidification increase continuously and separate gradually from β-Mg17Al12 phase, which makes the β-Mg17Al12 phase connect together and distribute on the α-Mg grain boundary closely approaching the equilibrium solidification structure. Hardness in eutectic structure area is higher than primary α-Mg grain. With the increasing of annealing temperature, hardness in eutectic structure area will increase and then decrease, when the temperature is over 400°C, the hardness will increase again, but hardness of primary α-Mg grain nearly unchanged. Keywords: casting-rolling; anneal; semi-solid; magnesium alloy; microstructure

Abstract: Ductile cast iron was quenched at different austempering temperatures with different isothermal time, so there were austempered ductile iron (ADI) materials with nine different mechanical properties. Their metallographic structures were qualitatively and quantitatively analyzed with scanning electron microscope and X-ray diffraction method. Curves of the relationships between heat treatment parameters, content of retained austenite and carbon content in retained austenite were studied respectively. Models that showed their relationships were built in the base of fuzzy subtractive clustering method to research the rules of isothermal temperatures and time affecting the microconstituent of ADI. The results show that the metallographical matrix structures of ADI become ausferrite, and its mechanical properties are strengthened notably. From the curves and fuzzy models, we knew that the effect of austempering temperature on the component content of ADI was predominant, and austempering time was inferior. Thus, as the temperature increased, the content of retained austenite, carbon content in retained austenite increased markedly. Keywords: ADI, heat treatment parameters, retained austenite, carbon content of retained austenite, fuzzy subtractive clustering model