| Bolted connections are widely used in modern machines.In the aerospace industry,the cost of bolted connection assembly can reach 40% of the total cost.The workload of assembling bolts is about half of the total assembly workload of the whole machine.The assembly quality of bolted connections is right The reliable and stable operation of the whole machine has a major impact.The characteristic of bolt connection is that the overall structure can withstand larger loads by applying appropriate pretension.The precise control of pretension has always been the difficulty and focus of bolt assembly.There are many factors that affect the accuracy of bolt tightening,including materials,Shape,size,number and arrangement of bolts,assembly environment,etc.,while our country’s bolt assembly theory has some research on bolt antiloosening and tightening process optimization,but there are few studies on the impact of manufacturing deviation on assembly quality;in addition,There is no practical method for calculating the actual load of bolts during the service stage.Because the bolts are subjected to eccentric loads in most cases,and the connection structures are different,it is difficult to make a unified calculation of the bolt load transfer function.Most studies use finite element simulation analysis and test methods to study a specific structure,and there are few studies on the factors that affect the load transfer function.In view of the above two problems,this paper introduces the manufacturing deviation of the joint surface into the process of pretension formation and contact stress state change,and on this basis,further analyzes the pretension dispersion and other factors that affect the fatigue of the bolted connection structure in the service stage.The law of influence on performance.First of all,this paper takes M10 bolt connection as an example,establishes a theoretical model of thread engagement considering the pitch deviation,and reveals the mechanism of stress redistribution.Then,in order to further quantitatively analyze the change law,a parameterized finite element single bolt tightening simulation model was established.By drawing the torque-pretension relationship curve under different manufacturing deviation,it was verified that the pretension formation mechanism is correct under the manufacturing deviation.By comparing the stress distribution cloud diagrams of bolt nodes under different manufacturing deviation,the correctness of the theory of stress redistribution on the contact surface is verified by manufacturing deviation,and a method to improve the bearing performance of bolts is proposed based on this.Finally,through a single bolt tightening test,the relationship between the pitch deviation and the thread friction torque,the end face friction torque and the bolt pretension is established,which verifies the rationality of the simulation model and the accuracy of the above-mentioned theory.On the basis of the above work,this paper studies the calculation of the actual bearing load of the bolt in service stage,analyzes the change of the bolt load in different stages,studies the influence of the dispersion of the pretension on the bolt load,and further analyzes the influence on the bolt load And then verify the accuracy of the influence law through the finite element simulation model.In this paper,the manufacturing deviation of the joint surface is brought into the process of bolt pretension formation during the tightening process,and its influence on the bolt load capacity in the service process is studied.Various aspects are analyzed from the perspective of the two continuous states of bolt tightening accuracy and bolt load capacity.The influence law of factors on the fatigue performance of bolt connections has certain guiding significance for the assembly process of bolts and the design of ring flange bolt connection structure. |
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