| The hydraulic stretching method relies on a hydraulic tensioner to tighten the bolts,which may result in a certain rebound phenomenon,causing the final pre tightening force to be unequal to the set tension value,which has a negative impact on the anti loosening and tightening of the bolts,and may even cause the entire bolt to fail.Therefore,studying the rebound phenomenon of tensioner fastening bolts and exploring the influencing factors of reducing rebound is of great significance in the engineering field.This article adopts this method to focus on the phenomenon of bolt rebound,mainly from the mechanical analysis of bolt connections,finite element analysis of bolt tightening,and experimental analysis of bolt tightening,to systematically study the rebound mechanism of tensioner fastening bolts.The main work content and conclusions are as follows:(1)By conducting mechanical research on the connection structure of the tensioner fastening bolts,a mathematical model for bolt rebound deformation is established.The corresponding rebound amount of each component is approximately equal to the bolt rebound amount X.Derive the relationship between the set tension value,bolt rebound amount,and residual preload,providing a theoretical basis for subsequent analysis.(2)Use Solidworks to design the three-dimensional structure of hydraulic stretchers,bolts and nuts,and other components.A new mesh generation method is proposed based on curve equation expressions for complex thread structures.A hexahedral mesh with thread rising angles is established in Hypermesh,and refined mesh models for M16,M20,and M24 are designed based on this method.Then,during the process of tightening the bolts with a hydraulic tensioner,the analysis steps and boundary conditions are determined in Abaqus,and a finite element model is established to achieve multi-stage and full process simulation,achieving a realistic simulation effect.(3)The main factors affecting bolt rebound error include bolt specifications,thickness of the connected parts,temperature changes,changes in elastic modulus,and friction coefficient.Among them,for M16,M20,and M24 bolts,as the set tension value increases,the bolt rebound error gradually decreases and stabilizes at around 30%.For every 20 mm increase in thickness of the connected part,the average rebound rate of the bolt increases by4.69%.An increase in temperature will reduce the residual pre tightening force of the bolt,and the impact of temperature on the connected part is greater than that of the bolt.The rebound error caused by changes in the elastic modulus of the bolt is greater than that of the connected part.Reducing the friction coefficient between the nut and the bolt is beneficial for reducing the rebound error.(4)Determine the testing equipment and build a testing platform for the tightening process of the stretcher,design two sets of test models,M16 and M20,and conduct tightening tests under different tensile loads.Comparing the experimental and simulation results,the two trends are relatively close,verifying the reliability of the simulation model.And it was found that the rebound rate of M16～M24 bolts is about 70% of the set tension value,which is 10% higher than the traditional calculation method for rebound error.During the installation process,use bolts with larger diameters and connected parts as much as possible,which is beneficial for improving the residual preload. |
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