Uncertainty Quantification And Reliability Analysis Of Pump Truck Boom Structures

The boom is the key working part and the main bearing part of the concrete pump truck.It is a hydraulically-driven multi-joint variable-configuration slender flexible rod system that is subjected to complex alternating external dynamic loads.The dynamic response caused by the dynamic load is the pump arm.The key reason for the structural failure.Since the invention of the pump truck in the 1970 s,the domestic and international pump truck design standards have adopted the dynamic load coefficient method when considering the influence of dynamic loads on the boom structure,ie,the weight of the structure and the concrete load under the horizontal attitude of the boom.Superimposed by the corresponding dynamic load factor,the static method is used instead of the real dynamic effect.Due to the uncertainty of the dynamic load and the uncertainty of the multi-joint structure of the pump boom,this method cannot accurately reflect the The safety condition of the boom in actual operation.In response to these problems,existing reliability studies are mostly based on probabilistic assumptions,using anti-fatigue design method,experimental test collection of the dynamic stress spectrum of the pump vehicle prototype in the actual operation,fitting to expand the dynamic load spectrum and carry out the fatigue test of the boom system,The uncertainty of the load and structure is described by a random process,and the structural design is modified based on the test results.This kind of method presupposes the probability distribution function of the parameter,requires obtaining a large number of experimental data samples,the design and test period is long,and the cost is high.Unlike the probability density information,the definition of the range of uncertain parameters is usually relatively easy,and the The sample size of the parameter is also small.Therefore,in recent decades,non-probabilistic and probabilistic structural analysis methods based on uncertainty have attracted more and more attention and research from domestic and foreign scholars,and have gradually demonstrated certain advantages in terms of convenience and economy.The reliability of the multi-joint flexible manipulator represented by the pump arm boom plays an important role.In this paper,the uncertainty theory is introduced into the analysis of the truck arm structure,and the uncertainty factors in the boom structure system are effectively measured,and the structural reliability analysis of the boom is performed based on this.The attitude uncertainty and dynamic load frequency uncertainty of the multi-joint boom structure of a pump truck are modeled.Based on the probabilistic-interval mixed uncertainty analysis method,the resonance reliability of the boom structure of the pump truck is studied.The process model measures the friction force caused by the concrete flowing through the boom pipe,and then carries out non-random vibration analysis to obtain the dynamic response boundary of the boom vibration.In consideration of the randomness of the initial crack length and fracture toughness of the boom structure,the pump arm is developed.The probabilistic damage tolerance analysis of the frame structure predicts its fatigue reliability.The main work undertaken and completed is as follows:(1)The finite element dynamic model of the truck arm structure and the concrete flow impact load model were established.The computational method of the dynamic response of the pump truck boom under specific configuration and specific dynamic load was developed,and the accuracy of the finite element model was verified by experimental tests.The effectiveness of the boom structure dynamic model was verified by the multi-arm model rig experiments.The concrete flow rate,the pumping frequency and the commutation time were obtained through the multiple pumping system experiments.The flow impact load of the concrete was deduced and the effectiveness of the calculation of the dynamic response of the pump arm boom was verified by the dynamic response test of the multi-position boom.(2)Based on the probabilistic-interval hybrid uncertainty model and structural reliability analysis method,a hybrid reliability analysis method for vibration of a multi-joint flexible manipulator is proposed for the randomness and boundedness of the structural parameters of the engineering machine.The upper and lower bounds of failure of the manipulator can be then achieved.Probability interval estimation.The structural uncertainty and dynamic load uncertainty of the pump boom are modeled and described.According to the completeness of the information of the uncertain parameters of the boom and load,the uncertain parameters are measured by the probability variables and interval variables.The response surface function of the dynamic characteristic variable with respect to the configuration uncertainty parameter is established within the variable configuration range of the pump arm boom,and the probability-interval mixing is established based on the configuration-dynamic characteristic response surface function and the excitation load condition.The vibration reliability analysis model uses the iterative decoupling method to solve the vibration reliability.(3)By introducing the interval process model to describe the uncertainty of the dynamic excitation of the pump truck boom,a non-random vibration analysis method for the mechanical boom structure is proposed,and the upper and lower bounds of the dynamic response of the structure are obtained.In the non-random vibration analysis,the boom system is described by the finite element dynamic model,which avoids the derivation and solution of complex dynamic differential equations;the dynamic uncertain load parameters are described by the interval process,and only the fluctuation of the dynamic uncertain incentive is required to be obtained.Borders avoid reliance on large amounts of sample data.The calculation of the upper and lower bounds of the dynamic response is based on the structural unit impulse response and is obtained using the convolution integral and the correlation properties of the interval process.(4)Based on the linear elastic fracture mechanics,sub-model technology was used to simulate and analyze the existing crack defects and extended fracture on the pump truck boom,thus carrying out the crack propagation analysis and realizing the reliability prediction of damage tolerance.The high-precision finite element modeling of the local hazardous area of the pump boom was performed.The global model and the sub-model were used to simulate the crack propagation behavior of the boom,and the corresponding crack propagation path and crack propagation life were predicted.