The Key Structure Optimization Design And CAE Analysis Of The Upper Assembly Of The Mixer Truck

Concrete,as an important material in the construction industry,has a significant impact on the structural safety of buildings.It is crucial to avoid a decrease in homogeneity during transportation of freshly mixed concrete from the mixing plant to improve its quality at the construction site.The quality of concrete during transportation is mainly related to the spiral blades of the concrete mixer truck.Traditional studies on the blades mainly focused on structural and flow field analysis through coupling methods to analyze the stress state of the blades,but they cannot accurately describe the particle motion of concrete under the action of the blades.This paper conducts numerical simulations of the motion process using the discrete element method to analyze the movement characteristics of concrete particles under the action of the blades and optimize their design.Meanwhile,the upper assembly,as the main loadbearing component of the mixer truck,has a significant effect on vehicle structural safety.In the past,the equivalent force application method was commonly used for the subframe and related components of the upper assembly,followed by calculating the structural stress state.To improve the accuracy of the analysis,this paper combines the discrete element method with the finite element method to study it and input the forces acting on the mixing drum and subframe components into the finite element model for analysis.Based on the analysis results,the structure of the subframe and related components of the upper assembly is optimized to reduce overall weight and improve safety.The main contents of this paper are as follows:(1)The front cone,cylindrical section,and rear cone of the mixing barrel of a concrete mixer truck have different requirements for the spiral blades.Under the premise of meeting the different usage requirements of each section,a study was conducted on the traditional blade spiral equation to optimize and design a type of mixing blade with variable helix angle for different parts of the mixing barrel.(2)The concrete particles were divided into coarse aggregates and mortar,and numerical simulations of concrete slump tests were conducted using both the Hertz-Mindlin and JKR models in the discrete element software.The different contact parameters between concrete particles were calibrated and optimized by combining the engineering database of the software with physical tests on the slump degree.To further improve accuracy,the particle equivalent density was set to achieve actual mass.Meanwhile,the homogeneity of concrete particles during different blade mixing processes was analyzed using the discrete coefficient as an evaluation index.The homogeneity and discharge efficiency of concrete particles under different working conditions for different blades were studied.(3)By combining discrete and finite element simulation,the stress situation of the mixing barrel under concrete action was analyzed under different working conditions.At the same time,to reduce the overall weight of the mixing barrel,the thickness of each part of the mixing barrel was optimized using it as an independent variable.A mixing barrel with different thicknesses in each section to meet the usage requirements under different working conditions was designed.(4)The subframe and related components of the upper assembly on the mixer truck were analyzed under multiple working conditions based on the joint simulation process.The topology optimization design was carried out with the targets of minimizing stress and maximizing low-order frequencies.Then,based on the initial structure obtained from the calculation,size optimization was conducted.After screening for parameter sensitivity,orthogonal experimental design and grey correlation analysis were performed on the dimensions of the optimized structure.Further optimization of the structural dimensions was carried out using the whale optimization algorithm with the low-order dynamic frequency as the evaluation index.Finally,random vibration fatigue analysis and structural optimization design were performed on the subframe and related components using the frequency domain method.