| The hydraulic cylinder of large-scale ship lock miter gate hydraulic hoist is a typical axially compressed slender rod,and its buckling stability is of great significance to insure safe operation.For the new navigation channel ship locks in the Three Gorges,the maximum submerged depth reaches 38 m,the designed capacity of the hoist is 3445 k N and the slenderness ratio of the hydraulic cylinder for the hoist reaches 116.58.However,the presented research on the buckling stability for horizontal hydraulic cylinder is still not clear.The structure and boundary conditions of the hydraulic cylinder are greatly simplified leading to a difficulty in obtaining a reasonable critical buckling load.To solve the above engineering problems,this dissertation conducts the following research work:(1)The hoist force characteristics of hydraulic hoist under extremely large submerged water depth are studied considering water resistance,friction between the bearing and the top / bottom pivot of the miter gate,wind load and inertia.The turbulence characteristics and the water resistance were analyzed during the opening and closing process by FLUENT.The dynamic model of miter gate and hoist was established,and the analytical calculation formula of hoist force was deduced.The hoist through opening and closing process was calculated by the formula.Also,the influence of submerged water depth,the operation mode of the hoist and the depth of the door on the hoist force were discussed.The results show that the maximum hoist force and its' sensitivity decrease with door depth increasing.With the increase of door depth from 0.26 m to 1.5m,the maximum hoist force decreases by 54.08? 61.24%.Among the three operation modes constant speed,variable speed and infinitely variable speed,the maximum hoist force and oscillating value of infinitely variable speed are the smallest.When the hoist runs with infinitely variable speed,the maximum hoist force occurs at the end of closing and the beginning of opening.Moreover,the theoretical calculation method was verified by ADAMS with 0.67 ? 5.73% error.(2)A calculation method for the buckling stability for the horizontal hydraulic cylinder under the small deflection assumption including virtual fixed state discrimination for hinge support was proposed.Buckling stability of hydraulic cylinder was analyzed.Based on Timoshenko beam theory,the small deflection mechanical separated body model for the cylinder tube and piston rod was established,considering the elastic support at the cylinder tube end.Then,the linear equations governing the deformation were obtained.The value of static friction moment and the dynamic friction moment were compared to determin whether the hinge support is in a virtual fixed state.The Newton downhill method and the static criterion were used to calculate the critical buckling load of the hydraulic cylinder.The influence of the friction at supports,the stiffness of the elastic support at the cylinder end and the shear effect on the buckling stability was analyzed.The results show that,due to the introduction of the virtual fixed state,the critical buckling load is sharply increased by105.27% with the increase of the friction coefficient of piston rod end support.By adding elastic support at the cylinder tube end,the buckling stability of the hydraulic cylinder is distinguished improved.When the elastic support stiffness changes from 0 to 3000 N/mm,the critical buckling load of the hydraulic cylinder increases by 54.68%.Under the small deflection assumption,the shear effect impact slightly on the deflection and critical buckling load of hydraulic cylinder(by < 1%).(3)A calculation method for critical buckling load of hydraulic cylinder considering large deflection was proposed,and the buckling stability of the hydraulic cylinder was analyzed.Based on large deflection theory,the buckling stability calculation model considering hinge support friction,self-weight,fit clearance and elastic support at cylinder tube end was established.The Runge-Kutta method and particle swarm optimization algorithm were used to solve the differential equations governing deformation.The results show that the calculation results of critical buckling load for the hydraulic cylinder decreases by 40.49% ? 48.69% after considering large deflection.By the proposed method taking large deflection condition,the calculated critical buckling load is increased by 3.98 ? 7.54%,and the deflection is decreased by 0.46 ? 8.27% when shear effect excluded.The influence of shear effect on the deflection and critical buckling load is more significant than that under small deflection assumption.Under the general tolerance fit,the influence of the clearance between the cylinder tube and the piston rod on the deflection is 4.83 ? 27.69%.The critical buckling load is slightly lower with increase of the clearance.The increase of the elastic support stiffness at the cylinder end can significantly improve the critical buckling load.With stiffness vary from 0 to 3000 N/mm,the critical buckling load of the hydraulic cylinder increases by 73.20%.(4)In order to verify the proposed calculation method,a proportional physical model test of the hydraulic cylinder for new navigation channel ship locks in the Three Gorges was designed.The deflection and critical buckling load of the hydraulic cylinder under different hinge support distance and cylinder tube end support condition were tested.Using small deflection and large deflection calculation method,the difference between the calculated and the experimental critical buckling load is 1.84?4.17% and 10.76?12.84%,respectively.After the elastic support added at cylinder tube end,compared with the free state,the deflection of the test cylinder decreases by 54.1% – 61.2%,and the critical buckling load increases by more than 34.8%.Through the research in this dissertation,two calculation methods of the critical buckling load under small deflection and large deflection condition for the hydraulic cylinder of the horizontal hoist were proposed.And the influence of the friction at hinge support,fit clearance,and the stiffness of the cylinder tube end elastic support on the critical buckling load of the hydraulic cylinder was revealed.For the engineering requirement,the hydraulic cylinder buckling stability calculation method under small deflection considering the hinge support virtual fixed state is effective. |
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