Research On Dynamic Response And Fatigue Strength Of Pump Truck Based On The Fluid-solid Interaction Theory

Attitude change of pump truck arms leads to the complicated working conditions.Design requirements of light-weight and maneuverability make arm structure complicated.Truck body vibration results in big vibration response of arms.Stress distribution on arms isvariable as arms attitude changs.So,it is necessary to carry out study on structure strength ofpump truck,especially on dynamics of arms.The arms,which are the key part of pump truck,are studied based on the fluid-solid theory and finite element theory.And the research onfatigue strength of arms is performed by the method of combining field test on pump truckwith experimentation on the fatigue resistance of the base material welded joints.(1)The horizontally moving fluid-tube cantilever model is put forward incorporating thestructural features of pump truck and the research achievements on cantilever pipe conveyingfluid.Dynamic differential equation of the model is derived based on kinematical theory andHamilton variation principle.(2)The most dangerous working situation where arm direction is perpendicular tosupporting point diagonal is concluded by mechanical analysis.So the field test is conductedunder this situation.According to the results of the finite element calculation and modalanalysis on whole model,the locations of high stress and weak in lateral stiffness are selectedas measuring points.The vertical amplitude response,vertical velocity response and verticalacceleration response of revolving table,which are used as boundary conditions of simulationanalysis,are concluded based on the analysis of measuring date of cylinder piston rod at thefront support.In the test conditions of stress ratio R=0.2,tensile fatigue tests on basematerial welded joints are carried out using MTS fatigue testing machine.The tests show thatthe fatigue limit of welded joints is 205N/mm².Based on Goodman equation,the GoodmanFatigue Limit Diagram of base material welded joints is plotted.(3)By contrast calculation with two concrete fluid flow velocities of 0rn/s and 2.265rn/s,the mean value of vibration response of arms are identical and the maximum amplituderatio(A_U=0/AU=2.265is approximate to 2.And by contrast calculation with the two Rayleigh damping ratio of 0 and 0.00845,the amplitude ratio is approximate to 1.So it is concludedthat the concrete fluid flowing can enhance the structural damping significantly.Compared thesimulation results which are carried out by MATLAB and ANSYS with the measuring results,the similar change tendency of dynamic stress history is verified.And the simulation resultsof mean stress and stress amplitude are close to that in measuring results according toassessment analysis in Goodman Fatigue Limit Diagram.Compared the results carried out bythe dynamic load coefficient method and our method,the stress distribution law is basicallysimilar,but the high stress value and the high stress location are not the same.Thecomparison result shows the availability of our method.(4)Dynamic differential equation of the arm system containing parameter of dip angleαis derived.According to the simulation results of arm system with parameters of dip angleas follows:α=0°,α=20°,α=52°andα=80°,stress histories are obtained.Not only doeshigh stress concentration always occur in weld position located in end of arms,but stressvalue and position also change with parameterα.The problems of insufficient fatiguestrength take place in ribbed plates according to assessment analysis in Goodman FatigueLimit Diagram.So,it is necessary to strengthen structure in design stage because of ribbedplates beside in box beams unable to repair for finished product.(5)Reinforcement schemes are designed and the fatigue assessment analysis onreinforced structure is performed again.The result shows that the method used is feasible.The study in this dissertation pays much attention to solve practical engineering problem.Conclusions are made on bases of experimental data.Analysis methods provide goodreferences for design and strength assessment of this kind of structure.