Research On Contact Characteristics Of Assembly Structures Based On Ultrasonic Guided Waves

Many mechanical parts are assembled with each other by contact,such as the interference fit between high-speed train axle and wheels,the fit among gas turbine rod fastening rotor disks and the bolted connections.Because of the high load-carrying capacity of this kind of fit,it is always used in key locations of the assembly structure to guarantee the normal operation of machines.But this kind of fit raises high requirement to the contact surface characteristics,it also requires that the assembly must be preloaded properly.Neither excessive preloading nor insufficient preloading can make the assembly operate normally.However,at present,there are few studies concentrate on the contact characteristics of shaft and disk structures.Guided waves,as a kind of stress wave,can propagate at long distance with low attenuation and are sensitive to tiny damage.So researching the contact characteristics of assembly structures on the basis of guided waves has important practical significance.Firstly,this paper researches on the guided-waves basic theory.Then,combining finite element analysis and experimental research,the contact characteristics of the interference fit between high-speed train wheelset and the contact characteristics among rotor disks are studied respectively.For high-speed train axle,most current researches focus on the single-axle damage detection.In this paper,the influence of the interference fit and the interference fit tolerance on the guided-wave propagation characteristics is studied firstly.The results show that the existence of interference fit will reduce the amplitude of guided waves signal,and the larger the interference fit tolerance is,the smaller the received guided-wave amplitude is.Then,the energy difference method was used to detect the fatigue damage on the high-speed train axle.The study found that this method still works in the wheelset assembly,and the smaller the interference is,the more obvious the energy difference is.The research lays a foundation for the energy difference method applied to the actual high-speed train axle damage detection.For the fit among the rotor disks,the contact between two disks is studied firstly in this paper,and the relationship between the preload force amplitude and the guided waves energy is researched.The results show that the received guided-wave energy increases with the increase of the applied preload force.When the preload force reaches a certain value,the guided-wave energy approaches the saturation value without increasing.When the number of disks increases,the same trend is still exhibited.Therefore,it is possible to use the guided wave energy change to measure the preload of the rotor assembly.Finally,for the uneven preload force distribution,using the guided wave,a method is proposed to detect the preload distribution of disks,and the method is still applicable when multiple disks are in contact.