Applied Mechanics and Materials Vols. 446-447

Abstract: This paper based on the same wind conditions and geological data, and use the CFD software to established the square and round expansion foundation that satisfy the condition under Extreme Loads, and then analysis and comparison the calculation results of the two kinds of foundation. Compared and analyzed the amount of concrete, base pressure, subsidence, the crack width, tilt rate against overturning, skid safety factor and so on, to find out the pros and cons of the structure and provide a reference for the choice of the wind turbine foundation under the corresponding geological conditions.

Abstract: The hoisting forces on a 38.5m wind turbine blade in multiple positions are computed using the computational fluid dynamics (CFD) method. The computation model is constructed with the steady wind conditions, blade mesh model and the blade positions which are determined by the blade pitch angle, azimuth angle and rotor yaw angle. The maximal and minimal hoisting forces in three-dimensional coordinates are found and the corresponding pitch angle, azimuth angle and yaw angle are obtained. The change of the hoisting forces on wind turbine blades is analyzed. Suggestions are given to decrease the hoisting forces of the blade in open wind environment.

Abstract: In order to make a precise interpret and research of interior ballistics performance for a new-type light caliber cannon, an interior ballistics mathematical and physical model was established, on the basis of two-phase flow interior ballistics theory and description of interior ballistic cycle. MATLAB software was used to conduct numerical simulation. Conclusion indicates that the simulation results manifest favorable consistency with the experiment results. Simulation results can comprehensively interpret the physical process in guns by pressure distribution, projectile velocity and gas temperature distribution.

Abstract: The tower cranes need constantly attaching to rise in the construction of high-rise buildings. The tower body which sets attached frames combined with the four-rod-type unilateral statically indeterminate attachment system is a common form. With the attachment height and distance increasing, the attachment rods become more delicate and flexible. It is necessary to check the overall and local stability of the attachment structure. When a single limb instability happens, the reduced-order variation structure brings about the redistribution of internal forces. The anti-buckling capability depends on the structure of variation. To the condition that the single limb instability occurrs on the component which has the weakest stiffness, an exact internal force expression of the structure under composite loads has been deduced in terms of the moment equilibrium method. At the same time, the decoupling support stiffnesses of the attachment device in each direction have been obtained by the unit load method. Based on the refined calculation model, the internal forces are further analyzed under the condition that the instability rod bears the fixed Euler critical force, and the structural strength and stability capacity has been judged. The calculation result proves that the whole structure has great bearing potential after a local buckling.

Abstract: The out-of-plane stability of the crane jib with two symmetric drawbars is studied. Differential equation with two non-conservative forces caused by the two symmetric drawbars is established in critical condition. According to the boundary conditions and proper parameter processing, the out-of-plane characteristic equation is obtained for the crane jib. Comparison with the ANSYS results verified the correctness of the method. And special cases are given to show the consistency of the method used in this paper and that with one drawbar given by the Chinese Design Rules for crane (GB3811-2008). The contribution of the angle between two symmetric drawbars to the out-of-plane stability of the crane jib is also discussed. The results show that, the crane jib with two symmetric drawbars has higher out-of-plane stability than that with one drawbar, and the increase of the angle between the two symmetric drawbars will lead to the significant increase of the out-of-plane stability of the crane jib.

Abstract: To enhance the carrying capacity of the crane variable cross-section telescopic boom, the usual practice is using the cable at its top end, it makes the out-of-the-lifting plane stability problem of crane telescopic boom become solving the Euler critical force with follower force. This paper established the deflection differential equations of crane telescopic boom model which under actions of cable, with proper boundary conditions, the recurrence formula of buckling characteristic equations were presented, and some practical applications were given. The influence on buckling critical force of crane boom due to the ratio of the length of cable and crane boom was discussed. Took certain four-sectioned telescopic boom as example, the destabilizing critical force was calculated, the result showed that in comparison with the ANSYS method, the buckling characteristic equations in this paper is completely correct.

Abstract: Most current pressure transient analysis techniques of hydraulically fractured wells are based on the fully penetrating assumption, which assumes equal thickness of hydraulic fracture and the formation. However, field application show that the fractures thickness can be shorter than the thickness of formation, which leads to vertical flow into the fracture. Thus applying the thickness equality assumption of current well test models to a partial penetrating fracture may give contradictory result. Further, there are very few studies concerning pressure transient analysis of partial penetrated wells. So it is important to develop analysis model and procedure to this type of fracture. In this paper, we presented an analytical model for partially penetrating hydraulic fracture in isotropic systems, along with the assumption that fracture is finite conductive. This model is then applied in the analysis of field production data, which verified validity of this new model.

Abstract: The short comings and limitations of traditional inspection method of sheet metal parts were described in this paper. Aiming at the inspection method based on the 3D models of sheet metal parts, the method of the inspection information extraction was introduced also. The actual shape of the sheet metal was obtained by the portable photoelectric equipments and then the 3D model was formed. The inspection information was extracted from the 3D model by the system which developed by VC++ tools on the CATIA platform. The characteristics of this method are high accuracy, environmental protection and high efficiency.

Abstract: Spur gears are the most common type of gears for industry, due to its simple structures and low costs of manufacture. Under the complex loading conditions, failures can easily occur in the form of de-bonding, pitting, spalling or crushing of coating structures. Failure may originate from initiation of cracks, and its growth and propagation, however, basic failure mechanism is still not clear. In order to investigate the failure mechanism of coating structure failure for the spur gears, this paper presents some understandings about the coating damage at the teeth flank of a spur gear, based on a novel Finite Element simulation-procedures. This modeling procedure was developed based on several modeling approaches including: parameterized FE modeling, Cohesive-Zone Model and sub-modeling technique. The numerical model of spur gear was based on 42CrMo4 steel with PVD coating deposited as TiN/CrN multilayer structures. It was found that greater load bearing capacity exist for spur gears with the coating of nitride states deposited on 42CrMo4 steel.

Abstract: Interior permanent magnet synchronous motor (IPMSM) systems are vulnerable to uncontrolled generation (UCG) when the inverter switches loss their drive signals suddenly during flied weakening high speed operation. At this point, uncontrolled rectifier is composed by freewheel diodes in the inverter, the current comes from the motor through the rectifier, and then charges the battery. This paper develops a simple analytical model of this system firstly, and then carries out the simulation of UCG transient process to investigate the impact of the motor speed, battery capacity and other factors on UCG and feedback-power obtained throughout the process. Moreover, circuit improvement is presented in order to avoid destruction risk of the battery, motor, inverter and other relevant components during UCG.