Research On Bolted-Joint Modeling And Contact Stiffness Identification Method

Bolt connection is affected by many uncertain factors, and is manifested as a complicated nonlinear problem. At present, the model of the bolts connection is described by stiffness and damping factors or equivalent stiffness without damping, and the stiffness factor is one of a key parameter of the joint surfaces. It is indicated that the nonlinear behaviors of connected modeling is represented under condition of alternate load of vibration andthe uncertain factors, so that abve parameter identifications can be realized.So it is important that the identified method of connection parameters should is determined.In this dissertation, the dynamic characteristic of bolt structure being influenced by joint surface, combing FEM and experimental modal analysis with fuzzy theory, the method of the identified parameters is studied, in order that the nonlinear dynamical model is realized. As the result, analysis method of dynamic parameters is provided for forecast and optimized design of structure model. The paper contents are showed as follows:Firstly, the experimental modal analysis has been builded. By signal analysis, and both frequency and analysis bolt structure are completed under the conditions of different number of bolt looseness and bolt pre-tightening torque, can provided data references for the FEM modal analysis and fuzzy inference engine.Secondly, the model parameters of the bolt connection are described by stiffness factor. Both the number of the spring elements and equivalent regiona are determined reasonably, and the equivalent dynamical model of the joining surface is built. By ANSYS softeware, APDL program of FEM is designed. Subsequently, combining FEM modal analysis with experimental modal analysis, the relationship is ansalyzed between the natural frequency and total stiffness, and parameter regionsis is determinedused.Finally, all of the fuzzy concepts, the fuzzy subsets of the natural frequency and the interface total stiffness, the fuzzy logical relationships, and the fuzzy inference engine are determined. As a result, the dentification method of contact stiffness is design.