Applied Mechanics and Materials Vols. 157-158

Abstract: The fast urbanization in Chongqing metropolitan has had a great impact on the environment and resources. The water resource has been recognized as one of the key elements to the sustainable development of this region. This paper presents a method of predicting the regional Water Resource Carrying Capacity (WRCC) using the supply-demand balance model. The method predicts that the WRCC of Chongqing metropolitan is from 8.8 million persons to 14 million persons in 2020 and it will not become the bottleneck of the social and economic development of Chongqing Metropolitan in the coming period of time. However the climate change and its impact on the regional ecology will have an effect on it. The results show that the usable capacity of Passing-by water is the most important element of the WRCC of Chongqing metropolitan therefore the protection of the ecological environment in the upstream area is very important. This paper has proposed tangible advice on the sustainable social and economic development in context of water resource.

Abstract: In this paper, a distributed attitude consensus control law has been proposed in the context of multiple homogeneous spacecraft formation flying only through local interactions while the GPS and antenna are denied. One of the engineering problems of implementing the aforementioned spacecraft formation is that some relative measurement sensors, e.g. the camera, have limited field-of-view (FOV). It raises that the maximum relative attitude of any two neighbor spacecrafts in the formation should not be greater than the constant attitude deviation determined by the FOV of these immobile sensors during formation maneuvers and keeping. Our approach to this problem is based on the state-weight strategy for network consensus problems, which has been a little investigated in the literature. We present a leaderless distributed attitude consensus control law such that all the attitudes of the formation flying spacecrafts can globally reach consensus, and the connectivity of the interconnected commination topology is strictly preserved. Throughout this paper, the interconnected communication topology is assumed to be undirected. Simulation results demonstrate the effectiveness of the control law. The future research has been discussed in the end.

Abstract: In mechanical engineering, earthquake engineering and modern municipal construction, It can be found that there are shallow-buried cavity or inclusion structure everywhere. In this paper, Green's Function is studied, which is the solution of displacement field for elastic semi-space with semi-cylindrical gap and multiple shallow-buried cavities and inclusions while bearing anti-plane harmonic line source force at any point. In the complex plane, considering the symmetry of SH-wave scattering, the displacement field aroused by the anti-plane harmonic line source force and the scattering displacement field impacted by semi-cylindrical gap and multiple cylindrical cavities and inclusions are constructed. Through applying the method of multi-polar coordinate system, the equations with unknown coefficients can be obtained by using the stress or displacement condition of the cylindrical cavities and inclusions in the radial direction. According to orthogonality condition for trigonometric function, these equations can be reduced to a series of algebraic equations. By solving these algebraic equations the value of the unknown coefficients can be obtained. So the total wave displacement field could be got. By using the expressions, an example is provided to show the effect of the change of relative location of semi-cylindrical gap, the cylindrical cavities and inclusions and the location of the line source force.

Abstract: The determination of pouring time is the important content in the casting process design. Pouring time to determine the design of the casting process is very important content. Appropriate pouring time can avoid many defects such as misrun, cold lap, entrapped slag, distortion, blowhole, swell, cope raise and so on. This paper analyzes the characteristics and shortcomings of determining several kinds of pouring time in current production of gray iron castings. The writer proposed a new calculate formula of pouring time about gray iron casting. By comparing the successful production instances, it is proved that it is good reliability, scientific and suitability.

Abstract: Hydrogels based on Poly(vinyl alcohol) (PVA) were synthesized using the combining method of chemical agent and freezing-thawing cycle. Sodium Trimetaphosphate (STMP) is a kind of crosslinking agent in this reaction. The resulting hydrogels were characterized in terms of tensile properties and compression stress-strain testing. The influences of STMP and water content on mechanical properties of hydrogels were investigated. It is suggested that PVA hydrogel has excellent tensile strength, higher elongation at break and viscoelastic materials’ stress-strain curve. Tensile strength of specimens without STMP increases from 4 to 6.8 MPa, as well as elongation increase from 300% to 458%, respectively. When the strain changes from 10% to 50%, tangent compressive modulus dramatically increases from 0.58 to 9.9 MPa for hydrogels with 80wt % water and 0.41 to 5.4 MPa for 85wt % water. Meanwhile, the addition of STMP can further improve the mechanical properties of PVA hydrogel.

Abstract: Road slope and vehicle parameter is of great importance in vehicle control. In order to estimate the on-line road grade, an accelerometer is mounted on a vehicle. A state-space model for the Kalman Filter is established. And R and Q matrix of the filter is tuned offline to optimize the filter. By experiments, the feasibility of the model as well as the algorithm is verified to be able to estimate the road grade online with precision and little delay. Other vehicle parameters can therefore be estimated with the road grade.

Abstract: An analytic design method on an approximately equal velocity ratio transmission mechanism is presented. The mathematical principle is that a compound function produced by two basic functions, let its one order differential is equal to an assigned constant on the special point, and then two to three order derivatives of the compound function are all zeroes, thus one algebraic equation is got, its solution defines the mechanism dimensions. This a principle not only sets up a new design method on approximately equal velocity ratio mechanisms but approximately equal velocity is independently designed. A design example shows that this method is simpler and transmission characteristics are better than optimization method.

Abstract: According to electromagnetic waves theories, emissivity modeling of a layered casting surface has been developed to elucidate the different emissivity during the growth of oxide film. Through test detection a angle where p-polarized emissivity assumes a peak value is between 60°-80°. Emissivity stabilized when the growth of oxide film is enough. The conclusion provides an important theory for the design the temperature measurement equipment on the surface of casting.

Abstract: This paper presents a method for the problem of optimal trajectory planning of redundant robot manipulators in the presence of fixed obstacles. Quadrinomial and quintic polynomials are used to describe the segment of the trajectory. Cultural based PSO algorithm (CBPSO) is proposed to design a collision-free trajectory for planar redundant manipulators. CBPSO optimizes the trajectory and ensures that obstacle avoidance can be achieved. Simulations are carried out for different obstacles to prove the validity of the proposed algorithm. Different test data generated by GA, QPSO and CBPSO are provided with a tabular comparison. Simulation studies show CBPSO has potential online usage in engineering and distinct fast computation speed compared with the other two algorithms. Results demonstrate the effectiveness and capability of the proposed method in generating optimized collision-free trajectories.

Abstract: Top drive casing running tool, because of its convenience, speed and safety, has been widely received by the research enterprises of petroleum mechanism and instrument. Now, there have been developed several kinds of casing running tools which have gradually been used by the drilling corporation at home and abroad. The slips system’s parameters, such as the axial thrust, slips length, teeth form, teeth interval, etc., directly affect the performance and safety of casing running tools. Those have no reports about correlative theoretical investigation results. Here, we found the mechanical analysis model between slip and casing and gain the minimum primitive axis thrust of slips. Then the minimum teeth interval of the slips is deduced by contact mechanics. And then the slips available working length is worked out through the shell theory and empirical formulas. Finally, based on finite element method, we obtain tooth form angles’ recommendable range by studying the tooth form. This study supplies theoretical basis to structural design of slips system of the top drive casing running tool.