Study On The Test And Generation About Load Spectrum Of Deep Loosening Shovel

Deep loosening shovel is a key component of subsoiling and soil preparation combined operation machine,which is widely used in dryland crops,sugar cane,grass planting and other operations.At present,the soil environment on which domestic regions and crops depend varies greatly.The traditional design of deep loosening shovel cannot meet the different requirements and is easy to cause fatigue damage and failure of parts.This traditional design method is a strength design method in the static field.The method converts the influence of dynamic load into static load and increases the size of design load.However,it cannot reflect the change rule of load signal.It is impossible to estimate the damage to parts caused by the sequence of loads,the magnitude of the average amplitude,and the average amplitude cycle frequency,which leads to the inability to accurately calculate the strength of parts during design.Therefore,the compilation of load spectrum in dynamic field is introduced.The load spectrum of a part is a load history that can reflect the load condition of the part when it works and has statistical regularity.The load spectrum can be expressed not only by the load time history,but also in the form of charts,matrices,probability distributions and frequency spectra.After drawing lessons from the load spectrum research in the fields of automobiles,aviation and other construction machinery,this paper designs and carries out the research on the compilation of the load spectrum of the agricultural machinery-deep loosening shovel,which provides data and theoretical basis for the design and optimization of the deep loosening shovel and the reliability analysis.Based on the above research objectives,this paper has carried out the following work and obtained the conclusion:(1)Detailed analysis and demonstration are carried out on the structure of the deep loosening shovel and the stress situation in the working process,and the theoretical stress values of the two parts of the deep loosening shovel structure are obtained: 2467 N for the shovel tip part and 4975 N for the shovel handle part.Based on this,the finite element analysis is carried out,and the stress and strain distribution of the deep loosening shovel is obtained,and then the structural damage point is determined to be 85 mm from the top of the shovel handle.(2)Based on the stress analysis of the deep loosening shovel,the overall design scheme of the deep loosening shovel load test is determined,including the restructuring of the deep loosening shovel fixing device and the three-point suspension device,the location of the measuring points and the arrangement of strain gauges,the construction of the whole test system,the preparation of field tests and other aspects.Finally,the test tests of various load components of the deep loosening shovelvf are carried out,and the random load signals of various working conditions are obtained.(3)Interference noise and errors are eliminated from the test data to ensure the reliability and validity of the load data.The data after pretreatment are checked for stability and rotation,and the stability characteristics of the data are determined,which provides a theoretical basis for the compilation method of deep loosening shovel load spectrum and the determination of working condition ratio.(4)Using rain flow counting method to count the circulation frequency,the histogram of average amplitude frequency of deep loosening shovel load signal is obtained,the probability distribution function of average,amplitude-frequency is estimated,the circulation frequency is extrapolated to 106 times by using parameter extrapolation method,and the average amplitude is extrapolated to an extreme value.The final load conditions are synthesized with the depth of 25 cm,30cm and 35 cm accounting for 1/3 respectively,and the two-dimensional eight-level load spectrum of each measuring point under the deep loosening shovel combination conditions is finally obtained.Finally,a one-dimensional program load spectrum suitable for laboratory loading is obtained by using the wave center method.Specifically,the wave centers of the forward bending load spectrum,the lateral bending load spectrum and the lateral tensile load spectrum are 3516 MPa,?30MPa and 45 MPa respectively,and the cumulative frequency of their respective load cycles are 277671 times?247655 times and 289693 times respectively,and their respective maximum amplitudes are 8744 MPa,?264MPa and 392 MPa respectively.The maximum amplitudes are processed by the unequal interval method to obtain 8 grades,which are superimposed on the wave center when the program is loaded.