| Hub bolts are the key fasteners of helicopter rotor system,and the fatigue life of hub bolts is one of the important factors affecting helicopter flight safety.Rolling strengthening is an important process to improve the fatigue life of hub bolts.Traditional rolling strengthening adopts manual machine rolling,which has some problems such as low rolling precision,poor consistency and low efficiency.Aiming at the rolling strengthening requirements of the characteristic parts of hub bolts,this paper studied the key technologies of hub bolt rolling pressure and support force control,precision tool setting,and designed and developed hub bolt rolling equipment.The main research contents are as follows:(1)A scheme for on-line measurement of rolling pressure and supporting force using high-precision force sensor was developed,and a mechanical structure was designed for online measurement of rolling pressure and supporting force The hub bolts rolling pressure and rolling strengthening support of force control technology,frequency domain is established within the system based on PID loop feedback inner loop position control and force signal of the rolling pressure and support impedance control model,write the position based on impedance control Lab VIEW program,realized the hub bolt support at the actual rolling pressure and rolling process of expectations trace.(2)The dynamic function and design requirements of hub bolt rolling equipment are analyzed and the horizontal overall layout and structure composition of hub bolt rolling equipment are determined according to the requirements of R Angle of hub bolt root,cutter back groove and rolling strengthening of thread tooth bottom of different specifications.A fully automatic hub bolt rolling equipment has been invented,which integrates rolling pressure measurement and control,digitization of material on the machine,accurate tool setting and automatic tool rolling.According to the motion control requirements of hub bolt rolling equipment,the overall design scheme of control system and water-gas system is determined,and the design parameters of hub bolt rolling equipment are formulated.(3)To solve the problem of surface feature difference in different rolling parts,a series of special tools for bolt root R Angle,cutter back groove and thread tooth bottom were developed,and a machining trajectory optimization method was proposed to adapt to complex curves by converting the tool point of feature curve.The X-and Z-direction tool-setting formulas of hub bolts with different sizes were derived,and the precision tool-setting strategies of rolling wheel and rolling part were studied.The 3d models of spindle rotation unit and tool feed support unit of hub bolt rolling equipment were drawn,and the specific working forms and motor parameters of each unit were determined.(4)The hub bolt rolling equipment was manufactured,and the performance of the hub bolt rolling equipment was tested and analyzed.After testing,the maximum error of tool setting accuracy is 8μm,which meets the requirements of precision tool setting.The accuracy test scheme of in-position rolling pressure and support force measurement is developed,and the error compensation mathematical model of rolling pressure and support force output by modified force sensor is established.The feasibility test of 300 M steel hub bolt rolling strengthening was carried out.The surface roughness before rolling was Sa1.16μm,and the surface roughness after rolling was Sa0.258μm,which increased 77.76%,verifying the feasibility of the hub bolt rolling equipment.In this paper,the hub bolt rolling equipment is designed and developed,and the hub bolt rolling pressure and support force control,precision tool setting and other key technologies are studied and applied in enterprises.The results are of great significance to improve the manufacturing level and anti-fatigue performance of helicopter hub bolts. |
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