复合化学镀层在盐化物料中的耐蚀性

采用极化曲线研究了不同磷含量的Ni-P镀层在盐化物料中的耐腐蚀性,对比了不同种类的复合化学镀层在盐化物料中的耐蚀性能,对镀层的组成、表面形貌以及镀层力学性能、孔隙率等进行了分析。结果表明,镀层在盐化物料中的耐腐蚀性与其成分关系密切。镍磷镀层的磷含量越高,耐腐蚀性越好;合金镀层中,Ni-Sn-P的耐蚀性能较Ni-Cu-P镀层为优。合金镀层用于盐化设备有利于获得较好的综合性能。结果还显示镀层的微观形貌对镀层的耐蚀性有很大的影响。

Interface repairing for AA5083/T2 copper explosive composite plate by friction stir processing

Multi-pass friction stir processing(M-FSP)was performed to repair the interface defects of AA5083/T2 copper explosive composite plates.The interface morphology and its bonding mechanism were explored.The results show that higher rotation speed and lower transverse speed produce more heat generated during FSP.The defect-free and good mechanical properties of the AA5083/T2 copper composite plate can be obtained under the condition of the rotation speed of 1200 r/min,the transverse speed of 30 mm/min and the overlap of 2/24.Moreover,M-FSP changes the interface bonding mechanism from metallurgical bonding to vortex connection,improving the bonding strength of composite plate,which can guarantee the repairing quality of composite plates.

Low cycle fatigue behavior of zirconium−titanium−steel composite plate

The low cycle fatigue behavior of zirconium−titanium−steel composite plate under symmetrical and asymmetric stress control was studied.The effects of mean stress and stress amplitude on cyclic deformation,ratcheting effect and damage mechanism were discussed in detail.The results show that under symmetric stress control,the forward ratcheting deformation is observed.Under asymmetric stress control,the ratcheting strain increases rapidly with mean stress and stress amplitude increasing.Under high stress amplitude,the influence of mean stress is more significant.In addition,by studying the variation of strain energy density,it is found that the stress amplitude mainly promotes the fatigue damage,while the mean stress leads to the ratcheting damage.In addition,fractographic observation shows that the crack initiates in the brittle metal compound at the interface,and the steel has higher resistance to crack propagation.Finally,the accuracy of life prediction model considering ratcheting effect is discussed in detail,and a high-precision life prediction model directly based on mean stress and stress amplitude is proposed.

Numerical Investigation on Power Outputs of a Wind Turbine Sited over Continuous Hilly Terrain

The location of wind turbines on a continuous hilly terrain has an influence on its power outputs.A CFDbased approach is developed to investigate the complex aerodynamic interference between two wind turbines and the hilly terrain.In this approach,a new three-dimensional model of hilly terrain is established to analyze its viscous effect,and a wind shear is modelled through logarithmic function.They are coupled into the aerodynamics of wind turbine based on“FLUENT”software.Then we apply the proposed method to the NREL Phase VI wind turbines and compare with an experiment in the atmospheric boundary layer(ABL)wind tunnel to validate its accuracy.The simulation also investigates the power outputs of wind turbines on the flat ground and the continuous hilly terrain by changing the location of the wind turbine related to the hilly terrain and the shape of the 1st hill.The results show that the wind turbine located on the top of the 2nd hill has the maximum power;and that when the wind turbine is located on the downstream of the hill,the stall zone should be avoided,and the power of the wind turbine located on the side of the hill is higher than that of the wind turbine located on the front and rear of the hilly terrain.

Simulation and Experimental Research on Fuel Spray Characteristics of a Self-pressurized Injector

As a miniaturized direct injection(DI)solution,a self-pressurized injector is of great significance for small aviation piston engines,such as spark-ignited two-stroke heavy-fuel engines.The spray characteristics of DI injectors are an important application prerequisite.In this paper,the computational fluid dynamics(CFD)software AVL Fire is employed to study the spray characteristics.Two types of spray models are established based on the Han Sheet model and the KH-RT model,and simulation works are carried out according to two types of spray tests in the literature.The comparison results show that in the constant volume bomb test,the spray patterns obtained by simulation under the two sets of environmental pressures are similar to those in the experiment,and the simulation spray using the KH-RT model can fit the spray contraction of the near nozzle field and the vortex of the far nozzle field better.In the tube test,the spray patterns obtained by simulation under the five sets of flow velocity are similar to those in the experiment,and the simulation spray using the KH-RT model can fit the spray expansion and the vortex of the far nozzle field better.The RP-3 kerosene spray characteristics of the self-pressurized injector are also experimentally studied,and the results demonstrate that due to the higher viscosity of kerosene,the spray shrinks more easily,resulting in a smaller spray cone angle and larger penetration.Therefore,changes in environmental pressure have greater impact on the kerosene spray pattern.