Experimental Study And Finite Element Analysis Of Hi-lock Fasteners Key Performance

Hi-lock nuts and bolts are aviation fasteners which have advantages of self-locking, high strength, high fatigue resistance, anti-vibration and easy to install. They are widely used in various aircrafts currently. Domestic factories can't make a mass production of hi-lock fasteners because the core principle has not been mastered. Currently most hi-lock fasteners rely on import, the cost is high and trade relations are sometimes influenced by politics. So the research of hi-lock fasteners is imminent. Aiming at the change of locking torque when one kind of hi-lock nut match with a variety of hi-lock bolts and the relationship between three important parameters of hi-lock fasteners, the experimental research has been done in this paper. In the meantime, the nonlinear finite element analysis about hi-lock screw joint has been done, and the reliability of finite element method is explored as a means to study hi-lock fasteners. The main contents are as follows:(1) After searching and collecting relevant information about screw joint, we researched the formation principle of locking torque based on relevant theory of screw mechanics and obtained the theoretical formula of locking torque. The formula provide a theoretical basis for explanation of experiment results.(2)Through experiment which 40CrNiMoA and Ti-6A1-4V hi-lock bolts match with 302HQ stainless steel, researched changes of locking torque under different materials; through experiment which Ti-6A1-4V hi-lock bolts match with 302HQ stainless steel under different lubrication conditions, researched influence of lubrication on hi-lock fasteners; through experiment which coating aluminum and anodized Ti-6A1-4V hi-lock bolts match with 302HQ stainless steel, researched changes of locking torque under different surface treatment conditions; the relevant conclusions will provide a useful reference for hi-lock assembly;(3)Consider the geometric dimensions of narrowed portion of hi-lock nuts, the relationship between three main properties of hi-lock nuts(locking torque, breaking torque, preload) was speculated based on screw mechanics, and theoretical formula is obtained based on speculation;(4)Through experiment which A286 hi-lock nuts match with hi-lock bolts with and without narrowed portion in M5/M6/M8, the results was obtained to verify the rationality of the speculation;(5)The nonlinear finite element analysis of hi-lock fasteners was done, the stress distribution of hi-lock fasteners was obtained and the preload was calculated. The reliability of nonlinear finite element analysis on hi-lock fasteners was verified compared to experimental results.