Dynamic Modeling And Study On Their Dynamic Characteristics Of Bolted Joints

Bolt joints are widely used in mechanical structure because of their convenient disassembly.The characteristics of bolt joint have a great influence on the dynamic characteristics of the whole machine.Because the bolt joint is a complex joint with multiple joint surfaces,it is impossible to model directly when using finite element software to analyze and study the dynamic characteristics of mechanical structures with bolts.Therefore,it is of great significance to explore a simple and effective modeling method which can reflect the characteristics of bolt joints.In this thesis,the dynamic modeling of bolt joint and the influence factors of its dynamic characteristics are analyzed and researched.Using combin14 element in ANSYS element library to equivalent the single bolt joint of overlapped beam structure,free modal analysis is carried out to obtain the first six modal parameters;at the same time,virtual material layer modeling method is used to equivalent the single bolt joint,and the first six order modal parameters are extracted by free modal analysis.The first six natural frequencies and modal modes of the structure are obtained through the modal test of LMS Test.Lab14A.The results of the two theoretical calculations are compared with those of the modal test.The results show that the theoretical and experimental modes of the two modeling methods are similar.Compared with the experimental natural frequencies,the accuracy of the spring element modeling method is higher than that of the virtual material layer modeling method,and the error is less than 2.2%.The results show that the spring element equivalent method is correct and effective in the modeling of single bolt joint.The dumbbell-shaped structure with double bolts is modeled and modal analyzed by two equivalent modeling methods,and the accuracy of the two methods is verified by the experimental results.The results show that the maximum error between the spring element modeling method and the experimental natural frequency is 14.8%,while the error of the virtual This study was funded by the National Natural Science Foundation of China(No.51675422).material layer modeling method is 33.60%.Therefore,when modeling multi-bolt joint,in order to obtain higher modeling accuracy,the modeling method of spring element equivalent joint should be selected.Compared with the experimental results,the spring element equivalent modeling method has higher modeling accuracy.Therefore,the spring element equivalent method is further used to analyze and study the dynamic characteristics of the bolt joint.The effects of different bolt pretension,surface roughness,bonding materials,bolt distribution and bolt number on the natural frequencies of bolt joint are studied,which provides a reference for dynamic analysis of bolt joint.