Analysis Of Failure Mechanism Of Gun Steel/titanium Alloy Threaded Connectio

The muzzle brake can effectively reduce the recoil force of the gun,but the introduction of the brake will cause slight deflection of the gun barrel and affect the firing accuracy.Therefore,the lightweight requirements should be considered in the design of the muzzle brake.Titanium alloy has the advantages of low density and high specific strength.It has a wide application prospect in the forming and material selection of muzzle brake.The titanium alloy muzzle brake is connected with the gun steel barrel by threaded connection.The failure of threaded connection structure will bring serious consequences and cause major safety accidents.Therefore,the failure mechanism of gun steel / titanium alloy threaded connection structure needs to be analyzed.The load distribution of thread is studied.Through the combination of theoretical calculation and finite element simulation,the effects of profile angle,pitch and thread wall thickness on thread load distribution are studied.The thread connection structure suitable for fatigue testing machine is designed,the thread loosening experiment under axial alternating load is carried out,the thread loosening behavior is analyzed,and the effects of pre tightening torque,alternating load amplitude and alternating load frequency on the degree of thread loosening are studied.The results show that the loosening of thread can be divided into two stages.There are oxidation wear,adhesion wear and abrasive wear on the working surface of thread.Increasing the preload torque and alternating load frequency can reduce the degree of thread loosening,and increasing the amplitude of alternating load will increase the degree of thread loosening.The effects of temperature load peak,holding time and cycle times on thread looseness were studied.The results show that increasing the peak temperature load will reduce the thread looseness first and then increase;Increasing the holding time will make the thread more loose;Increase the number of cycles to reduce the degree of thread looseness;The changes of peak temperature load and cycle times have little effect on the ratio of loosening torque to pre tightening torque;Increasing the holding time will significantly reduce the loosening torque.The effects of different materials,elastic modulus,friction coefficient,peak temperature load,coefficient of thermal expansion and preload on the looseness of threaded connection structure are studied by means of finite element simulation.The results show that the effect of friction coefficient is not obvious;The looseness of the same material is less than that of different materials;The difference of elastic modulus and the increase of preload can reduce the degree of thread looseness;The difference of thermal expansion coefficient and the increase of temperature load peak will increase the degree of thread looseness.The tensile fracture experiment of gun steel / titanium alloy threaded connection structure was carried out,and the effects of pre tightening torque,alternating load amplitude and temperature load peak on the fracture failure of the sample were studied.The results show that the fracture force increases with the increase of preload moment,increases with the increase of alternating load amplitude,and shows a band downward trend with the increase of temperature load peak.The fracture morphology shows the mixing of cleavage fracture and ductile fracture.With the increase of temperature peak load,the fracture form gradually changes from ductile fracture to cleavage fracture.The fatigue fracture experiments were carried out,and the effects of preload torque and alternating load amplitude on the fatigue fracture of the samples were studied.The results show that the fatigue life of the specimen increases with the increase of preload torque and decreases with the increase of alternating load amplitude;The change of fracture morphology is not obvious.