| Airframe rolling bearings are the key basic components for supporting and maintaining the rotation of aircraft mechanical equipment.The performances of the bearings directly affect the safety and reliability of the aircraft during operation.To a large extent,the performances of rolling bearings depend on the characteristics of the bearing material.The gradient distribution of the hardness and residual stress of the bearing rings directly affect their service life,and these distribution characteristics are closely related to the quenching process of the rings raceway.The induction quenching process has many advantages,such as stable heating,high efficiency,selective heating of the parts that need to be heated,energy saving,environmental protection and so on,to meet the quenching requirements of bearing rings.However,induction quenching is a complex process involving multi-field coupling of electromagnetic,heat transfer,phase transition,and stress and strain.Traditional research methods cannot accurately and efficiently evaluate the entire quenching process,and numerical simulation research methods can intuitively reflect the changes in structure and performance during quenching.Therefore,in order to obtain good physical properties of the airframe rolling bearing rings,it is very necessary to use numerical simulation methods to study the simulation of structure and performance regulation of the induction hardening.This article takes the rings of a certain type of the airframe rolling bearing(double row spherical roller bearing)as the research object,and the mathematical model of high nitrogen steel 30Cr15Mo1N material was established by JMat Pro which is a simulation software of material performances and experiments.And considering the structure of the inner and outer ring of the rolling bearing,the numerical simulation model of the induction hardening process of the bearing rings of the airframe rolling bearing was established through the DEFORM finite element analysis software.The induction hardening method of segmented current density was used to analyze the characteristics of the induction hardening of the bearing inner ring.The research results show that:the induction heating current density is set in sections,which can make the inner ring raceway surface with different distances from the coil uniformly heated.And the temperature at the sharp corner will change suddenly.The higher the current density,the higher the heating efficiency.So where the distance between the workpiece and the coil is large,the current density should be appropriately increased.After quenching,the residual austenite content of the raceway surface is about 6.97%,the martensite content is about 92.3%,the surface hardness is about 60.9HRC,and the raceway hardened layer is about 2.97mm.After cryogenic treatment,the residual austenite content decreased to 1.27%,the martensite content increased to 96.9%,and the hardness was 62.8HRC.The residual stress is distributed symmetrically along the radial plane of the center of the inner ring,and the residual stress of the subsurface layer is the largest,with the depth of about 2 mm and the value of about 190MPa.The induction hardening characteristics of the outer ring were analyzed using conventional induction hardening.The research results show that:at the high-frequency current frequency,the depth of the hardened layer and the residual stress of the outer ring raceway increase with the increase of the current frequency and current density,and decrease with the increase of the coil speed.The quadratic response surface can fit the simulation results of the outer ring induction hardening well.For the depth of the hardened layer,the significance of each factor is the current frequency,current density,and coil speed.For the residual stress,the significance of the factors is the coil speed and current density,current frequency.The optimal process parameters are a coil speed of 0.049r/min,a current frequency of 246k Hz and a current density of6.5×10~7A/m~2.After quenching,the depth of the hardened layer in the center of the raceway,the depth of the hardened layer in the groove of the seal ring and the residual stress of the subsurface layer in the center of the raceway are 1.609mm,0.595mm and146MPa respectively,and the residual austenite content of the raceway surface is about8.53%,the martensite content is about 89.61%,and the surface hardness is about60.4HRC.After cryogenic treatment,the depth of the hardened layer in the center of the raceway,the depth of the hardened layer in the groove of the seal ring and the residual stress of the subsurface layer in the center of the raceway are 1.642mm and0.608mm and 120MPa respectively,and the residual austenite content on the surface of the raceway is about 1.43%,martensite content is about 95.91%,surface hardness is about 62.5HRC.The induction hardening testes of the bearing rings were carried out according to the technological parameters of numerical simulation,and the performance of the bearing rings after the testes were compared with the simulation results.The research results show that the error between the simulation results and the test results is within13%,which proves that the research results of this paper are reliable and correct.In this paper,the numerical simulation study of the induction hardening process of the airframe rolling bearing rings is carried out.The different quenching methods are used to numerically simulate the induction hardening of the bearing inner ring and outer ring.And the correctness of the numerical simulation is verified by experiments.The segment setting of current density of induction hardening is suitable for the surface hardening of small and complex parts,and the profile quenching is suitable for the surface hardening of more regular parts.For different geometric shapes,different quenching methods can be used to obtain a uniform quenching structure.These studies have certain guiding significance for the development of induction hardening process for rolling bearing rings of this type of the airframe rolling bearing. |
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