Sensitivity Analysis and Optimization of Geometric Parameters of a New Fluid Bag Buffer Mechanism on Buffering Performance

A new fluid bag buffer mechanism,which can provide large axial stiffness under the small displacement,is designed.The dynamic change laws of the mechanism stiffness and the internal pressure of the fluid bag are studied when it is subjected to impact load.According to the protection performance for the flexible joint and the pressure change in the fluid bag during the impact process,the sensitivity of the geometric parameters of the fluid bag to the axial stiffness is analyzed by using the orthogonal experimental method,and the optimal parameter combination of the geometric parameters of the fluid bag under impact is obtained,leading to the displacement of the inner shell reduce by 41.4%.The results show that the internal pressure of the fluid bag is a rising process of oscillation and fluctuation.The sensitivity of the geometric parameters of the fluid bag to the displacement of the inner shell from high to low is as follows:Height H,radius r,wall thickness t,chamfer A.The correlation between the geometric parameters of the fluid bag and its internal pressure is:H is negatively correlated with the internal pressure,while the r,t,and A are positively correlated with the internal pressure.

Influence of Different Filling Materials on Stiffness of a New Buffer Bag

A buffer bag mechanism is designed,which can provide axial impact protection under small displacement.The stiffness characteristics of the structure under impact load are studied.The stiffness of the mechanism and the internal pressure change of the buffer bag are compared and analyzed,when the filling materials are liquid and gas respectively.Finally,the influence of initial fluid bag pressure,bulk modulus and shell thickness on the stiffness of the mechanism and the change of bag pressure are studied.The results show that the stiffness of the liquid bag is better than that of the gas bag when the filler is liquid and gas;the liquid bag has obvious pressure rise after the mechanism is subjected to axial force by 300 kN,and the gas bag has almost no pressure rise;the change of bulk modulus,which is1000,1500,2000 and 2500 MPa,has an obvious effect on the liquid bag,and it is positively correlated with the stiffness of the mechanism.The change of gas modulus,which is 28 and 44,has little effect on the stiffness of the mechanism;the thickness of the buffer bag,which is 5,10 and 15 mm,also has an obvious effect on the stiffness.The stiffness of the liquid bag is greater,and the protection for flexible joint is better in the same condition.

Surface Pressure Loading Technology of Ship Structures

A hull structure is prone to local deformation and damage due to the pressure load on the surface.How to simulate surface pressure is an important issue in ship structure test.The loading mode of hydraulic actuator combined with high-pressure flexible bladder was proposed,and the numerical model of the loading device based on flexible bladder was established.The design and analysis method of high-pressure flexible bladder based on aramid-fiber reinforced thermoplastic polyurethane was proposed to break through the surface pressure loading technology of ship structures.The surface pressure loading system based on flexible bladder was developed.The ultimate strength verification test of the box girder under the combined action of bending moment and pressure was carried out to systematically verify the feasibility and applicability of the loading system.The results show that the surface pressure loading technology can be used well for applying uniform pressure to ship structures.Compared with the traditional surface loading methods,the improved device can be applied with horizontal constant pressure load,with rapid response and safe process,and the pressure load is always stable with the increase of the bending moment load during the test.The requirement for uniform loading in the comprehensive strength test of large structural models is satisfied and the accuracy of the test results is improved by this system.