The invention discloses a bolt joint part looseness detecting method and
system based on a nonlinear shock excitation feature. The method comprises the following steps: carrying out simulated
modal analysis on a three-dimensional model of a test piece, and determining the arrangement positions of a
vibration exciter and a sensor of a local part of a bolt joint part; arranging the vibration exciterand the sensor according to the determined arrangement positions of the
vibration exciter and the sensor, and determining a vibration excitement parameter of the vibrator
exciter according to the simulated
modal analysis result of the three-dimensional model; maintaining the vibration excitement parameter unchanged, carrying out preliminary experiment on the same kind of test pieces to obtain a corresponding relation between a bolt pretightening force and a high
harmonic scaling factor, and generating a relation data base; and carrying out test on a test piece to be tested to obtain a high
harmonic scaling factor, querying the relation data base, determining the bolt pretightening force of the test piece to be tested, and judging whether the bolt joint part of the test piece to be testedis loosen or not according to the bolt pretightening force of the test piece to be tested. The method has the advantages of wide applicability, flexibility and convenience in use, high sensitivity andthe like, implements nondestructive detection, and is suitable for actual production.