Advanced Materials Research Vol. 421

Abstract: The pressure pipeline is simplified as the beam model with two simple supported ends. The mathematical model is established, considering influence of the fluid-solid coupling vibration. Then the critical flow velocity is obtained by calculation and solving. By analyzing the practical numerical example，the influence of physical parameters on the first three-order natural frequency is discussed. Using Matlab software for programming, the instability condition of pressure pipeline is obtained, which is consistent with the result of numerical calculation.

Abstract: By modifying the profile of spur bevel gear，the load fluctuation in transmission process can be effectively reduced, the contact area of the gear pair can be greatly improved, and the stress distribution of gear teeth also can be controlled. However, during the actual work, many factors may influence gear work performance. This paper considers the influence of assembly error on contact performance of gear in mesh, builds the assembly error mathematical model of modified spur bevel gear, and deduces the parameter equation of modified tooth profile curve. Then dynamic contact simulation analysis is carried out by applying ANSYS/ LS-DYNA software, the distribution of the stress and strain of bevel gear pair in different shaft angle deviations is accurately obtained.

Abstract: In semiconductor industry, carrier concentration of a semiconductor material needs to be measured. Theoretical computation is complex and has its limitation. Experiment measurement always needs complicated and expensive instruments. Here, a new method for measuring the carrier concentration of Si was put forward. The dependence of thermoelectromotive force on temperature was graphed. The results showed that when temperature is below 460K, thermoelectromotive force is proportional to temperature of the hot probe. Compared with other similar methods, this method is more simplified and thet equipment is cheaper.

Abstract: Electrical wiring is the main fireorigin on electrical fire, and aluminum wire laying lines used more fire hazard. The melting mark formed in process of fire is the important material evidence to analysis the cause, but the aluminum wire melting mark organization feature is also different in different solidification conditions, therefore, to identify the mark characteristics formaed in different environment conditions has become a important task of fire evidence identification. Prepared fire sample melting by the means of simulation test, and observed to analysis the experimental sample, then summarizes the influence of solidification environment on microstructure characteristics of aluminum wire trace sample. Through the analysis found that, because of the influence of subcooled temperature, make the most of the organization of melt mark cooled in the air have oversize equiaxial crystal organization, almost no holes; and the dip in water cooling of melting mark is formed in larger subcooling, so the organization have more than a small columnar crystal and cellular crystal, and have more small holes exist. These features of aluminum conductor mark can provide strong technical support for fire investigation.

Abstract: In this work, the effects of the addition amount of rear earth on iron phase morphology of Al-7Si-0.3Mg alloy with 1.2%Fe were studied by Optical microscopy (OM), X-ray diffraction (XRD) and electron probe (EPMA). The results showed that: (1) the defined amount of RE addition can significantly inhibit the needle-like iron phase in Al-Si alloy. RE can make the needle-like β-Fe thick thinning, and some even blow or bending. When the addition of RE is 0.36%～0.48%, the modification effect to needle-like β-Fe phase are best. In high iron Al-Si alloys modified by RE, a small amount of bone-like Fe-rich compounds caused by Re were found. (2) after adding excess of RE (RE%>0.48%), a deterioration phenomenon emerged with the formation of large amount of needle-like and plate-like (AlSiRE) intermetallic compounds.

Abstract: Boolean operation is the key technology for modeling the bone scaffold. This paper proposes a Boolean operation algorithm based on triangle mesh model. It firstly voxelizes the mesh models based on project vector and octree, and classifies the vertices into inside, outside and surface type according to the position relationship between the vertex and the other mesh model’s voxel. Then the triangles can be easily classified based on the vertices class. Finally the Boolean model can be composed by the corresponding triangles of the Boolean operation. In order to obtain the intersection features well, it detects the intersection lines and gets the intersection polygons further, and then triangulates the polygon using the ear clipping method. This Boolean operation algorithm has been applied to the bone scaffold modeling and got good performance．

Abstract: A series of three-dimension molecular dynamics (MD) simulations are performed using hybrid potentials to investigate nanometric cutting process of single-crystal copper with diamond tool. The effect of tool geometry in nanometric cutting process is investigated. It is observed that with the negative rake angle, the volume of chips becomes smaller due to large hydrostatic pressure and plastic deformation generated in the subsurface layer. When the rake angle changes from -40° to 40°, the machined surface becomes smoother. Besides, the ratio of tangential force to normal force decreases with the increase of rake angle. In addition, the effect of clearance angle is analyzed and approximate entropy (APEN) is presented to denote the complexity and uncontrollability of the interactions between tool and workpiece with different clearance angles. With the decrease of clearance angle, the machined surface quality decreases with the local stress distribution in subsurface layer is uneven. An appropriate clearance angle not only keeps cutting force stable, but makes sure of the quality of machined surface as well.

Abstract: The impurities content of domestic hydrogenated transformer oil and three kinds of naphthenic transformer oil had been determined by using the specified experimental methods. A series of experimental data had been obtained, including mechanical impurities, particulate contamination, corrosive sulfur, sulfur content, total acidity and interfacial tension. The impurities content of four kinds of transformer oil were compared with the quality indicators of transformer oil on GB/T7595-2008. The results showed that the impurities content of the former was not so satisfying although it had excellent electrical properties and the technology needed to be improved.

Abstract: Cyclopentadiene is an important material for making norbornene, and can synthesize norbornene dicarboxylic ester through the maleate and Diels-Alder reaction. Also, a structure similar to that of the representative PVC plasticizer dioctyl phthalate(DOP) was synthesized, so as to confirm the structure of compounds through 1H-NMR, FT-IR, Mass, and HPLC, and to compare the basic properties with those of DOP.

Abstract: Run out table cooling equipment and coiling temperature control (CTC) system, especially mathematic models of a hot strip mill were introduced. Heat transfer models such as air convection model, heat radiation model and laminar cooling model, process control models such as segment tracking model, feedback control model, self-learning model and case-based reasoning model were detailed described. Since online application of the new CTC system, the laminar cooling control system has been running stably and reliably with a high precision of coiling temperature.