Investigation On Failure Mechanism Of High Speed Twin-Screw Extruder Spline Shaft

The twin-screw extruder is widely used in the modification,granulating,premix and other production of engineering plastics.The screw shaft is one of the important components of the extruder and it will spend a lot of resource to production,installation and commissioning.Once failure occurs,it will bring serious economic losses and casualties to the business.Therefore,through a series of tests and theoretical work,this paper presented investigations on failure mechanism and effective measures for the screw shaft with high engineering value.The outcomes of the study would be useful information to prevent the similar failure,and ensure intrinsic safety,to promote safety production.This paper takes the twin screw shafts as the research object.Fracture failure mechanism of spline shaft has been investigated,including physical and chemical properties tests,finite element numerical simulation analysis and the characteristic analysis of fatigue.The main contents of this paper are as follows:Firstly,materials of spline shaft were verified on physical and chemical test,including chemical component analysis,mechanical property analysis,metallographic analysis and fracture morphology analysis.Results showed that,the initiation area of fatigue crack located on the root of spline teeth,with several fatigue sources and stress concentration phenomenon.And mechanical properties of spline shaft failed to meet the standard criteria and shrinking percentage was lower than that of the criteria,such as higher hardness on the edge part and low toughness,which cause cracking initiation easily.Secondly,structural stress of spline shaft was under taken with the static analysis module of the ANSYS software.Some comparative analysis with the different forms of screw mandrel and threaded components in the actual operation of the force was implemented.The results showed that,the maximum equivalent stress of the involute spline core is lower than that of the hexagonal mandrel.The maximum equivalent stress is located at the root of the spline teeth,with significant stress concentration phenomenon.In the transition area of the spline shaft,which were the weak part of the structure matching with the existence of local stress concentration.Thirdly,under the tension-compression fatigue test,fatigue strength and together with the function formula of the S-N curve were obtained,which is of great significance for the design of fatigue life and safety life of the screw shaft.Finally,comprehensive analysis on fracture failure causes was implemented with preventive countermeasures.The main reason for the fracture of the spine shaft is the stress concentration of the spline teeth,inequality of mechanical properties,unstable packing and tripping during the production.All factors together led to fatigue fracture of the spine shaft.