Analysis And Design Of Connection Characteristics Of Heavy Bolt

To adapt to the development pace of industry 4.0,the State Council proposed the made in China 2025 in 2015.The manufacturing industry is the mainstay of the national economy,the foundation for building the country,the way to develop the country and the basis for a powerful nation.As one of the core industries of the manufacturing industry,product safety and quality stability of heavy car manufacturing is particularly important.Bolt connection which could be often seen in heavy trucks was taken as the entry point,and focused on the principles of bolt connection failures,stress distribution of bolt connection and protection from bolt connection failures.And the major research contents are as follows:(1)Sales volume of heavy trucks in the past years in China was analyzed,which indicated that heavy truck would be confronted with a great number of replacement in the future 2~3 years and that under the stimulus of GB1589,sales volume of heavy trucks would stay at a high level.From the perspective of meticulous classification,with the rapid development of logistics,express and hazardous articles,proportion of semi-trailer towing vehicle is increasing gradually in the total sales volume and requirements and expectation of users on heavy trucks is also improving,thus improvement of safety and quality of heavy trucks is urgent.And moreover,improvement of bolt connection quality is an important part.(2)The process of bolt connection was analyzed,several common failure modes of bolt connection of heavy trucks was listed and factors which would affect bolt torque were calculated and analyzed,including friction coefficient of bolt,friction coefficient of connected parts,lubrication condition of bolt connection,and axial preload and tightening methods of bolt.In the end,the essay compared the three common assembly methods of bolt in assembly of heavy trucks.(3)Three experiments which respectively verified influence of lubrication condition on tightening torque,influence of tightening methods on tightening torque and influence of tightening methods on torque reduction were designed.The first experiment proved that lubrication condition had a great influence on tightening torque and connection efficiency,thus it should be concerned in the following design of bolt connection;the second experiment proved influence of tightening methods on bolt torque and proved that method of close up,initial tightening and screw down were better by comparing it with the method of continuous screw down.Moreover,the experiment could obtain stress-strain curve of bolt,thus acquiring tighten torque which was suitable for bolt;and the third experiment proved influence of tightening methods on torque reduction after tightening bolt.(4)ABAQUS was used in the essay to analyze stress distribution of bolt under the condition of loading external force of the system constituted by bolts,nuts and connected parts.Meanwhile,on failure positions of bolt after overloading of bolts,the essay discovered that the results were in accordance through finite element analysis and comparison of actual tests.(5)According to conclusions reached through theoretical analysis,experimental verification and finite element software simulation and combining with characteristics of production enterprises of heavy trucks,the essay proposed several suggestions to prevent bolt connection failures.