Time-varying Reliability Of Boom Structure Of Combined Harvester Based On ITRPD

The combined breeding machine is widely used in the field of forestry engineering,in which the boom is the key working part and the main bearing part of the combined breeding machine,Therefore,the safety of boom structure determines the operation performance of the whole machine.At present,the research on joint efforts frame with more attention paid to the reliability of the machine arm.However,the traditional reliability analysis methods are generally to directly analyze the reliability of the boom structure,while ignoring the long-term use process of the boom structure.Affected by complex environmental changes in forest areas,random loads,material performance degradation of the boom,and changes in structural resistance,the structural reliability of the boom usually changes with the change of service time.This also leads to the fact that in the actual use process,the reliability problem of the boom of the combined breeding machine is often not a traditional time-invariant reliability problem,but a more complex time-varying reliability problem.In this paper,the time-varying characteristics of the boom structure of the combined breeding machine during use are fully considered,and various uncertain factors in the boom structure are effectively measured.A time-varying reliability model and a solution method of the boom structure considering the time effect of load and the degradation of resistance with time are proposed.The main research contents are as follows:This paper summarizes the development of the combined harvester and the research status of the safety and reliability of the boom structure at home and abroad,and makes clear the significance of the research on the reliability of the boom structure of the combined harvester combined with the characteristics of the boom structure and work.Based on ANSYS finite element analysis,in a typical construction boom crawler forest joint efforts of the boom and the auxiliary arm as the research object,the solid finite element model is established for finite element analysis,respectively,combining the response surface method,the results of finite element analysis based on considering the effect of load resistance degradation and time-varying reliability model.Based on the idea of static transformation in time-varying reliability calculation method,iTRPD method is used to calculate time-varying reliability index of boom structure,and the changes of reliability index in different service years are obtained by comparing the static reliability index.On the basis of the reliability index of each year,the time-varying reliability analysis without considering the resistance factor is carried out and the influence of the resistance factor on the reliability index is compared.Through the analysis of engineering examples,the results show that the reliability index of the boom structure of the combined breeding machine will decrease rapidly with the increase of the service life cycle,and the decline speed will accelerate with the increase of the service life,which proves that the cumulative effect of time is considered.The obtained time-varying reliability research is more scientific and reasonable than the time-invariant reliability research,and is more in line with engineering practice.It also shows that the structural resistance of the boom will attenuate with the increase of service life,which means that the structural resistance can have a significant impact on the reliability index.This research provides a new idea for the structural reliability research of other forestry engineering machinery.