Fatigue Life Prediction And Optimization Design Of Loader Bucket Based On Load Spectrum

The research on the prediction of the fatigue life in wheel loader bucket is extremely important to improve the fatigue reliability of the bucket.This prediction is the kernel to restricting the wheel loader to improve its product quality.The bucket is the core part in wheel loader.It is prone to damage under the action of random load,which greatly affects the life and using performance of the whole machine.In order to improve the performance of the bucket in wheel loaders,this paper uses the bucket of SEM6-series wheel loaders as the research object.Based on technical methods such as load spectrum measurement and compilation,finite element stress and strain analysis,and also fatigue damage accumulation theory,this paper has made a deep research of the fatigue life prediction and optimization design of the bucket in wheel loaders.(1)Analysis of fatigue life theory: This topic has deeply studied the estimation method of non-parametric density used in the compilation of load spectrum and the theory of fatigue damage accumulation.It has comprehensively analyzed the influence of notch shape,part size,surface condition,and average stress on fatigue strength.(2)Load spectrum measurement and compilation analysis: According to the operating characteristics of wheel loader,a new loading measurement method is adopted to establish the external load identification model of the work tool.The time accumulation of the bucket load is obtained by using the method of force pin sensor in the three directions of X,Y,and Z.Using signal processing,rain flow statistical analysis,load spectrum extrapolation and other methods,the research has compiled the two-dimensional load spectrum and one-dimensional load spectrum of the bucket required for fatigue life prediction.(3)Finite element analysis of the bucket: A three-dimensional bucket model is established by using Pro/E.Also,total five traditional working conditions of the loader are simulated by using ABAQUS and HyperMesh software.The maximum pressure on the bucket appears at the position where the lug plate reaming hole is connected to the rear arm.The maximum stress point is 317 MPa,which is less than the yield limit of the bucket material of 355 MPa.However,the allowable stress with a safety factor that is greater than 1.2 is 295 MPa,which may cause fatigue failure,and the maximum bucket deformation is 38.75 mm.(4)The prediction and analysis of the life of the loader bucket: Based on the FE-SAFE software platform,the research has predicted the life of the loader bucket by using the nominal stress method and the P-S-N curve of the material,which is combined with the fatigue load spectrum data and the results of finite element analysis.The part with the smallest service life is consistent with the most dangerous part with the finite element analysis result.The minimum service life of the bucket under typical working conditions is 2620 h.(5)Bucket optimization design analysis: The paper uses the size optimization design method in the Hyper-Optistruct module to optimize the design of the bucket by selecting the total mass of the bucket as the objective function,taking the thickness of the steel plate size of each part of the bucket as the design variable,and setting the constraint conditions as the maximum stress and maximum deformation of the bucket.The optimized maximum stress and dangerous parts of the bucket are the same as the vulnerable parts of the original model bucket.The maximum stress is 289 MPa and the maximum deformation is 38.74 mm.Also,by optimizing,the minimum fatigue life of the new bucket is 2930 h,which has an increase of 310 h compared with the original bucket,and the life increasing rate is 11.8%.Therefore,it has realized the lightweight design of the bucket weight reduction ratio of 2.1%.This paper achieves the design goal of increasing the life of the bucket and reducing the weight of the bulk.Furthermore,it improves the performance of the bucket product,which forms a new and systematic method for the load spectrum analysis and fatigue life prediction of the loader bucket.This method has the great significance for breaking through the current development status of wheel loaders in Chinese market and moving towards high-technical industries.