Applied Mechanics and Materials Vols. 117-119

Abstract: In the paper, the Deform-3D software was used to simulate the mechanism of metal flow behaviour under the influence of different friction in the backward extrusion process, and further study its influence on die stress. The numerical simulation demonstrates that: smaller friction could reduce difficult deformation area of extrusion metal significantly; friction state not only affected the plastic deformation extent, but also would increase the consumption of extrusion energy; the unit pressure of punch and stress of inner wall increased along with the increase of friction, meanwhile, the ratio of them increased as well.

Abstract: Deeply buried tunnels usually lie in high stress fields, whose horizontal stress which is not uniform is far larger than vertical stress, and their stability is dominated by the original in-situ stresses. With three-dimensional nonlinear finite element method, the axis orientation effects of tunnel on the displacement and stability of two types of surrounding rocks are studied systematically for one water diversion project. The tunnel lies in different original stress fields whose maximum horizontal principal stress is parallel with or perpendicular to the axis and lies in different kinds of rocks. The numerical analysis results show that the plastic zones develop in side wall of tunnel mostly when the horizontal maximum principal stress is parallel with the tunnel axis while the plastic zones distribute in the top and bottom of tunnel when the horizontal maximum principal stress is perpendicular to the tunnel axis. It is concluded that the principle of tunnel axis should be parallel with horizontal maximum principal stress regulated by the “specification for design of hydraulic tunnel” is not available for the stability of tunnel always.

Abstract: Wire saw has a unique benefit in cutting precious material like SiC, Si monocrystal and gem etc since the cutting force is small, and the kerf loss is low and so on. In the common wire saw cutting process, the production efficiency is low, the wire saw wear is dramatic severe, the surface roughness of part is not expected and collapses flaws often occur on wafer as well, all those problems have a heavy effectiveness on wafer quality. In order to solve those problem, the ultrasonic vibration machining (UVM) has been applied to cut the hard & brittle materials which has a significant improvement on surface integrity of wafer and increasingly apply to nonconductive materials cutting, such as glass, ceramics, Si, gem and so on. In this paper, the cutting force for SiC monocrystal wafer by wire saw with UVM is studied, the mathematic model of cutting force for wire saw with UVM is discussed and the Fourier series expansion is used to solve the equation of cutting force. The experiments that the process parameters influence on the cutting force by common wire saw cutting and wire saw with UVM are conducted, respectively. The result show that wire saw with UVM can significantly decrease the cutting force, which is consistent with the theoretical analysis.

Abstract: The registering precision is one of the most important specifications in printing press. Many factors that may influence the registering precision including the construction of the printing press in design, the assembly precision in manufacturing stage, adjustment in process of operation, the wear and tear of the machine when it is in use, crawl of blanket and extension of sheet are all considered comprehensively. The mathematical models are built up to describe the register error of press. The algorithm of accuracy and precision of sheet-feeding and sheet-transferring is introduced. With the aid of image technology, the coordinates of marks can be obtained automatically, and the registering accuracy and precision can also be calculated.

Abstract: The technological parameters determine the metal pool profile and the grain size and orientation in the electroslag remelting process, and thus affect the quality of the final ingot. The microstructure in the small electroslag casting process was simulated by CA method by means of the software MATLAB. Along with the remelting process, the columnar grain begins to grow to certain angle with axles, the shape of the metal pool gets closer to paraboloid shape. Improving the slag pool temperature or increasing the coefficient of heat transfer at the bottom or decreasing the coefficient of heat transfer at the side can lead the axial trend of grain growing to increase and the depth of the pool to shallow, otherwise can lead the trend of grain growing to radial direction to increase and the depth of the pool to deep.

Abstract: Through simulation experiment of CO₂ invading into drilling fluids that viscosity and yield point are increased dramatically and drilling fluids is in a bad rheology. The concentration of HCO₃^- and CO₃^2- both are increased, the concentration of OH^- and pH value of drilling fluid both are reduced. It does not meet the drilling requirement as the concentration of CO₂ is too high, so we must eliminate it as soon aspossible. The glue soluting with KOH and CaO through some Lab experiments have optimized, which has a better performance for prevention and management of CO₂ pollution.

Abstract: The geological structure is very complex in Haita Basin, due to the difficult drilling, sidewall instability phenomena happened frequently during drilling process. And it has restricted the drilling speed and the development and exploration process seriously. According to the borehole collapse problems, physical and chemical properties experiment of mud shale had been operated, then we analyzed and predicted borehole stability of Haita Basin by experimental data, discussed the collapse mechanism in this area, and established corresponding countermeasures to prevent the collapse which has laid a good foundation for further research on key drilling technology and improving drilling rate in Haita Basin.

Abstract: In this presented work, by freeze-thaw test for three groups of shale ceramsite concrete with different mix proportion, the experimental results show: the shale ceramsite concrete has preferable frost resistance property. After 100 times freeze-thaw cycles, its loss in weight and strength is very small; the frost resistance increases as ceramsite pre-wetting time is raised, and with the increasing of the water cement ratio, the frost resistance declines. The statement that ceramsite pre-wetting treatment is detrimental to frost resistance still deserves discussion, as it depends on the pore structure, water absorption characteristic and concrete air content of ceramsite itself. Meanwhile, freeze-thaw mechanism of the shale ceramsite concrete was analyzed in this paper. The study results provide some reference for other studies.

Abstract: With the cloud computing is becoming mature, many of its characteristics for meteorological data processing is extremely important. Since HDFS is designed for reading and writing large files, it’s difficult to be taken advantage of small meteorological files. In this paper, an improved approach on HDFS is proposed for small meteorological files, small files are to be merged, indexed, and blocks are compressed, the pressure of memory on master node occupied by metadata is relieved, the speed of reading and writing small files is increased, read speed is increased by 50%, and write speed is up to 3-4 times of the original, saving about 2/3 of storage space and computing performance has also been improved. Thus, meteorological data processing can make use of cloud computing platform more closely.

Abstract: Primeval TC4 titanium alloy was subjected to solution treatment at 1150°C for 1h, followed by water quenching, oil quenching, air cooling and furnace cooling, respectively. The pulse-echo method was carried out to measure ultrasonic longitudinal wave velocities (ν) and attenuation coefficients (α) of these heat-treated samples. The relationship between microstructures of different cooling rates and ultrasonic parameters such as ultrasonic longitudinal wave velocities (ν) and attenuation coefficients (α) was investigated. The results show that the microstructures of heat-treated TC4 alloy were α phase and β boundaries, and the ultrasonic longitudinal velocities and attenuation coefficients of these heat-treated samples, in turn, increased with reducing the cooling rate from water quenching to furnace cooling.