Applied Mechanics and Materials Vols. 34-35

Abstract: Clearance is inevitable，so, with the increasing of machine’s speed, nonlinear vibration phenomenon caused by clearance is more apparent, which influences the precision and stability of mechanical system. For increasing the stability of mechanical system, a robust design method based on sensitivity analysis is studied, by using four-bar linkage as the research object, deducing the nonlinear dynamic model with clearance and the sensitivity of dynamic response, based on the rational planning to the tracks and control the sensitivities. In the design example, it shows that although the track deviation of robust design is slightly bigger than that of optimization design, the comprehensive dynamic performance of the mechanical system is much better than the latter, which means the stability of mechanical system is improved greatly. Thus, the robust design based on sensitivity analysis is an effective way to improve the stability of the mechanical system.

Abstract: The authors found a type of sidewall failure during the construction of a tunnel with high geostress. And relative strong rockburst usually occurred in the areas nearby during the excavation. This paper shows this type of failure called Crisp Fissure Failure and some characteristics of the failure. Reasons of the failure are also discussed. Further more, the authors studied the fracture distribution under this type of failure by Ground Penetrating Radar. Suggestions of support in a high risk tunnel are put forward based on the research of the Crisp Fissure Failure.

Abstract: Sand inflow is one of the problems in unconsolidated sandstone oil reservoir recovery. The most frequently applied sandcontrol method is high-pressure gravel squeeze packing sand control technology. But incorrect knowledge of stratum shapes under high-pressure squeeze packing leads to unreasonable technology and implement parameters. This thesis, based on the discrete element theory and by means of two-dimension grain flow simulation software PFC2D, considers three oil wells with unconsolidated sandstone in terms of their cementing strengths . The simulation result shows that strata with diverse cementing strengths vary remarkably when high-pressure squeeze pack is asserted. Established calculation pattern might lead to sizable deviation.

Abstract: In addition to vertical pulling force, the ground-drive screw pump oil recovery rod also stands twisting moment and bending moment. The diameter of the polish rod is generally larger than that of the pumping rod, and it stands a bit less stress than the pumping rod close to it, and the polish rod is generally made of relatively better materials. In practice, however, the polish rod fractures more often than the pumping rod above. This thesis considers that if the driving head deflects, the upper and the lower polish rods of the packing set are not in the same axial line, and bending moment will come into being in the polish rod of the lower part of the packing set due to the restriction of the polish rod by the packing set. Alternating stress caused by bending moment yields fatigue rupture of the polish rod during its rotation. This verdict is confirmed by the fracture position, the shape of the fractured surface, and quantitative calculation. This thesis proposes strict controlling of the deflection of the driving head by means of polish rod verticality survey instrument. Both theory and practice have proved that this method can effectively avoid fatigue rupture of the polish rod.

Abstract: As a high technique environmental friendly material, Wood-plastic composite (WPC) material has wide range of applications and is extruded by recycled wood fiber products and wasted LDPE. Waste Paper-Al-Plastic materials including Tetrapak beverage and milk boxes are used to extrude the WPC as thermal insulation exterior wallboard instead of normal wood fiber material in the present research. In this paper, simulated thermal insulation and Oxygen index combustion test were operated at the Lab conditions. Some experimental results are presented as follow: heat transfer coefficient of 100mm thick WPC hollow wall is 0.922 W/m2•K, which is equivalent to the thermal insulation performance of a 0.35m thick fly ash aerated concrete block. Oxygen index of 27 indicates that WPC is inflammable material. Zinc borate (ZB) and ammonium polyphosphate (APP) are effective flame retardant for Paper-Al-Plastic WPC.

Abstract: Taking construction crane for example, this thesis builds a reliable, controllable and easy-to-exploiting CAN-bus application network on the basis of iCAN series functional module and CAN-bus interface card of ZLG system, and it explores the methods of rapid allocation in control networks of construction engine. With CAN-bus controlling devices to guide all signals of sensors and output dates, this system is easily constructing and conveniently stalling. Meanwhile, this system has a good anti-inference ability, a high reliability and a good real-time response. The application of CAN-bus enables lifting moment restriction system to act as a subsystem embedded in other engineering control systems. The construction of this system has an important reference in explore a new generation of engineering control system.

Abstract: The effects of titanium modification, which was added along with the pouring liquid in ladles, on the shrinkage porosity and cavity of cast steel ZG35 smelted in intermediate frequency induction furnace were studied. Proper content of titanium could effectively increase the volume of concentrated shrinkage cavity, and restrain the forming of shrinkage porosity. The concentrated shrinkage cavity was analyzed quantitatively by stuffing wet gluten and draining water method. The maximal cavity arrived at 0.15wt.% titanium modification. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that TiC, acting as heterogeneous nuclei, could refine the structure grains, diminish the strong dendrites, and increase the fluidity and feeding capacity of steel liquid. However, overdoes titanium modification easily caused mass nitrides or oxides, which kept solid phases with high meting point in metal liquid to increase its viscosity and decrease the fluidity. On the other hand, these solid state titanium compounds enlarged the composition supercooling, so the metal liquid changed from sequential solidification to simultaneous solidification, resulting in inadequate metal liquid feeding, less oncentrated shrinkage cavity and serious shrinkage porosity.

Abstract: Hydraulic confined piston engine (HCPE) is a new type power device which can directly turn indicated work into hydraulic power, and three cylinders axial HCPE prototype has been manufactured. The load and stress study on its crankshaft is very important for future design. The working principles of HCPE was discussed, the mathematic model of its working process was constructed, and the load on crankpin by connecting rod was obtained by simulation. The total contact model of crankshaft reflecting the actual conditions was built, through which Von Mises stress, contact stress and friction stress of crankshaft were calculated. The maximum of Von Mises stress occures at the fillets of main shaft neck. The fatigue secure coefficient of crankshaft is about 2.85, which meets the demand.

Abstract: This paper carried out the effective dynamic simulation analysis for the 750KW Horizontal Axis Wind Turbine blades in the wind, gravity and centrifugal force coupling. Based on the selected turbulence model, and considering the natural flow of air as a viscous incompressible steady flow, and the fan blades as the flexible body, simulated the flowing line graph of wind wheel surface, and the overall mechanical performance data at any moment. After effective analysis of the Coupling force, obtained the deformation distribution patterns and rules, which provide much reference to the further failure analysis of fan blade and structural optimization design.

Abstract: According to designed parameters, the rigid model of the large wind generators has been built in UG software, the impeller is selected to be researched object, modal neutral files of key parts are attained by the analysis in ANSYS software. The analysis model of multi-flexible bodies of the impeller is built in ADAMS software. With analyzing, predigesting, loading of wind loads and analyzing of dynamic simulation of impeller model, a lot of dynamic parameters of flexible impeller are obtained, which are truer and exacter. These provide certain basis of the loads for designing, analyzing, optimizing the design of key parts of large wind generators in future. The new thought is explored, which are about dynamic research of multi-flexible bodies of large wind Generators. Further more; the high-performance large wind generators are designed.