Experimental Study On Friction Characteristics Of Laser Micro-texture High Strength Bolt

Modern mechanical system device,the importance of bolt connection has been can not be ignored.The clamping effect of the thread standard parts is the basis for ensuring the quality of the assembly and the reliability of the equipment.The friction between the threads is the decisive factor of the clamping effect.In the actual assembly,the friction coefficient between the screw pair directly affects the axial clamping force of the bolt.How to control and stabilize the friction coefficient of the thread has been the main research object of the standard parts industry.Therefore,the author combined with their own work,and the company issued the product research and development tasks,conducted a selection,that is,the use of reasonable thread surface strengthening measures to control the friction characteristics of the thread to improve its clamping performance,the topic has important Engineering application value.In recent years,with the deepening of the research on laser surface texture technology,it is considered that the microstructure of friction surface can be improved by active design and can improve the performance of surface lubrication.Moreover,the laser surface texture technology,with its excellent processing performance,that is,no contact processing,processing efficiency,shape and size of precise control,etc.,can be used to control the friction between the thread between the appropriate processing technology.This paper is the first to apply this technology to the preliminary processing of the thread surface processing.In this paper,the high-power internal combustion engine cylinder head and cylinder coupling bolts for the specific application of the object,proposed by the friction part of the laser micro-texture processing,control and stabilize the thread friction coefficient,improve the friction surface of the thread,Bolts can achieve excellent preload and loose performance.The main contents of this paper are as follows:The mechanism of interaction between laser and material and the principle of lubrication and friction reduction of surface micro-texture are briefly introduced.The development of laser micro-texture of the experimental device and the friction characteristics of the test bench to build;The Nd: YAG laser was used to study the laser micro-machining process on the surface of 40 Cr sample by using the special method of laser micromachining.The effects of laser pump current,repetition frequency,pulse number and defocus amount on the processing quality of micro-cavity morphology were investigated.The final process parameters were determined by optimizing the combination.In the German "SCHATZ multi-function bolt fastening analysis system" bench testing machine,the laser micro-texture bolt surface friction characteristics of the comparison,verify the test.The influence of the geometrical parameters(distribution density,depth ratio and so on)on the performance of friction pairs is analyzed emphatically.In the same working condition,the friction coefficient of bolts with non-textured bolts is compared with that of multi-group structure scheme,and the tribological properties of laser micro-texture bolts are verified.The results show that the friction performance of the screw surface treated by the surface micro-texture technology is more obvious,and the friction coefficient is more stable than that of the untreated bolt.Finally,the batch assembly verification is carried out on the high-power engine production line of the Company.The axial clamping force of the micro-texture bolts is monitored in real time.The verification results show that the axial clamping force of the bolt is stable and the expected effect is achieved.Of the clamping performance.