Advanced Materials Research Vol. 413

Abstract: In order to increase wear resistance of Fe-0.7Cr-0.8Mn cold work tool steels, low weight percentage of Ti incorporated to the alloy and subsequently, because of high affinity between additive titanium and carbon content in this alloy, low weight percentage of TiC in situ formed in matrix. These composites can be used as the milling balls in mining and cement industries because of their improved wear resistance. Formation, shape, size and distribution of TiC particles within the matrix were studied by optical microscopy equipped with image analyzer, optical emission spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. Also microhardness and density of the samples measured. Abrasion wear tests were carried out using a pin on disc type machine. An experimental design based on Taguchi method was applied to investigate the effect of TiC content, applied load, sliding distance and roughness of SiC abrasive paper on wear behavior of samples. The results show that by reinforcing the Fe-0.7Cr-0.8Mn steels with low weight percentage of TiC, wear resistance of these kind of milling balls significantly increases. Sliding distance has the most influence on wear rate of samples, also weight loss of samples decreases as sliding distance, applied load and roughness of grinding decreases.

Abstract: 87 prismatic flexural steel fiber-reinforced reactive powder concrete (RPC) specimens with the size of 40mm×40mm×160mm were tested as well as 87 dumbbell-shaped axis tensile RPC specimens after being exposed to different high temperatures. The effect of steel fiber content and heating temperature on the flexural and tensile strength of steel fiber-reinforced RPC was analyzed. With the steel fiber content increasing, the flexural and tensile strength of steel fiber-reinforced RPC after high temperature improve significantly, and they increase first and then decrease with the heating temperature elevated, and the critical temperatures are 200¡æ and 120¡æ, respectively. Equations are established to express the relationship between the flexural and tensile strength of steel fiber-reinforced RPC and the heating temperature. The theoretical curves are in good agreement with the test data.

Abstract: In this paper a general numerical method to analyze some simple planar frames subjected to concentrated loads with elastic large deflection is presented. In the method some reactions or displacements at the ends of the frames with three or below redundant constraints are considered as unknown, and a numerical method based on a more-fold method of bisection is presented to solve for the unknown reactions or displacments under known boundary conditions. In the examples in the paper,the flow graphs of solving for unknown reactions or displacements are demonstrated and some analysical results are given by the aid of some graphics.These examples show that some simple frame structures with three or below redundant constraints can all be analyzed easily and quickly with the numerical method presented in the paper.

Abstract: The unification differential equation of buckling and motion of viscoelastic beam subjected to the uniformly distributed follower forces in time domain was established by differential operators including extension viscosity, shearing viscosity and moment of inertia. According to the unification differential equation, dynamic stability of three-parameter model of viscoelastic beams subjected to follower forces with clamped-free supported boundary condition was firstly analyzed by power series. The relations of the follower force versus vibration frequency and decay coefficient were obtained, so was the effect of viscous coefficient on the critical load of beams.

Abstract: The field socket gas pipeline is taken to make the loading experiment in order to study the deformation and force state of the pipelines and the limit value of the deformation curvature of the pipeline．The monitoring data from the shield tunnel construction are analyzed, the effect of shield tunneling on the deformation of ground surface and buried pipelines is studied, and the rationality of the deformation monitoring value of gas pipelines in the Shenyang area is discussed．

Abstract: The present research aims to synthesize a nanoscale multilayer CrTiAlMoN hard coating for the modification of wear and friction performance, as compare to CrTiAlN coatings. CrTiAlMoN coatings were deposited on 1045 carbon steel substrates by magnetron sputtering at different Mo target current. The wear and friction resistance were characterized by pin-on-disc test. When a WC-Co ball was used as the counterpart, the coefficients of friction of CrTiAlMoN coatings were found to decrease with the increase of Mo target current, with the lowest value (0.34) being only one half that of CrTiAlN coating (0.76). The combination of high hardness above 36GPa and low coefficients of friction reduces the specific wear rate of the CrTiAlMoN coatings to only 10% of CrTiAlN coatings. When tested against a bearing steel ball, results demonstrate that the effect of Mo on reducing friction of the CrTiAlMoN coatings is not significant and even negative due to adhesive wear.

Abstract: Erbium salt was used as additives for the first time in preparing anodic aluminum oxide (AAO) films to improve its performance. AAO films were prepared from a 15 vol. % sulphuric acid solution containing erbium salt by anodization method; the effects of concentration of erbium on microhardness and thickness of AAO film were researched, respectively. The effect of heat treatment temperature on structure of AAO film was researched. AAO films were characterized by XRD, EDAX and SEM techniques, respectively. The microhardness and thickness of AAO film were 378.5HV and 82μm respectively, which were higher 12.99% and 17.14% than those of the film prepared in electrolyte of nothing addition erbium salt respectively. The aperture of AAO film was more uniform and the surface of AAO film was smoother than those of films prepared in electrolyte of nothing addition erbium salt. The apertures of AAO film were in 25~30nm. There was not erbium in AAO film. AAO films were amorphous when heat treatment temperatures of AAO film were below 800°C, when heat treatment temperature of AAO film were 850°C and 1000°C respectively, and AAO films were γ-Al₂O₃ and α-Al₂O₃ film respectively.

Abstract: The controlled-release tablets of sasanquasaponin (SQS) were prepared by using SQS, broomcorn-stalk and lactose as the main drug and accessories. The effect of the particle size of broomcorn-stalk on release rate was studied. Kinetics equation of the controlled-release tablets of SQS releasing SQS was fitted. The thermal stability and wet stability of the controlled-release tablets of SQS were investigated. The controlled-release tablet of SQS was characterized by infrared absorption spectrum (IR) techniques. The releasing rate of the controlled-release tablets of SQS were controlled by controlling the particle size of broomcorn-stalk. Release speeds of the controlled-release tablets of SQS releasing SQS were constant. The thermal stability and wet stability of the controlled-release tablets of SQS were good. The chemical bonds were formed among SQS, broomcorn-stalk and lactose.

Abstract: NBR is the essential material selected for the stator of progressing cavity pump which is used for oil extraction. The premature failure of NBR is the primary cause for shortening working life of the pump. Wear behavior of NBR and its mechanism by 45 steel were studied in crude oil medium using a MPV-600-type compute-controlled abrasive wear test machine. Through the friction test found at constant low load, and at constant temperature, the friction coefficient is along with the rotational speed increased first and then decreased and then increased; At constant low speed, and at constant temperature, friction coefficient decreases as the force increases; The friction coefficient increases with rising temperature first and then drops; The main wear mechanism of the rubber in crude oil is wet abrasive wear. The test results on the rational selection of working parameters to improve rubber metal friction pair of whole life have practical significance.

Abstract: The design of foundation of wind turbine should meet the requirement of subgrade bearing capacity. In this paper, reliability method was used to analyze the bearing capacity of gravity foundation of wind turbine. The circular gravity foundation in coral sands is taken as research object. By deriving the expression of maximum pressure at the edge of foundation base under the action of overturning moment, the performance function of subgrade bearing capacity reliability analysis is established. JC method is used to calculate the subgrade bearing capacity reliability index. Effect of foundation size to reliability index is analyzed. Iterative calculation shows that the method proposed in this paper can calculate the reliability index of foundation quickly.