Research On Method And Application Of Bending Resonance For Beam-type Components

Beam members are widely used in industrial engineering.Most beam members are subjected to alternating bending stress and are prone to fatigue damage.Due to the limited size of beam members,fatigue testing using traditional low-frequency loading methods is quite time consuming.Increasing the loading frequency and the test efficiency,shortening the test time,and reducing the test cost have become the trend of the bending fatigue test of beam members.The flexural resonance fatigue test of beam members utilizes the resonance loading principle,which can greatly improve the test efficiency.In this paper,based on the principle of bending vibration mechanics of beam members,the inherent properties of beam members are used for loading.With pipes and sleepers as examples,the method for realizing the bending resonance of beam members was explored.Such as,resonance amplification principle,natural frequency adjustment method,design of excitation source,engineering calculation,and design of test equipment(1)The basic principle of bending vibration of beam members is described,and the principle of resonance amplification of free restrained beams and simply supported beams is analyzed.The theoretical analytical solution of the corresponding mode function,natural frequency,and the position of the node is obtained;the method of adjusting the natural frequency of the test piece by increasing the weight at both ends.(2)Based on the study of the excitation source,a new type of eccentric exciter with eccentricity and radial adjustment was designed,and the principle of exciter loading was analyzed and explained.The new exciter can be used in combination to achieve circular force loading,vertical excitation loading,alternating force couplecoupleloading,etc.,which can be applied to many different loading occasions.(3)Aiming at the bending vibration of unconstrained beams,the engineering calculation method of vibration parameters is given,including the method of solving the stress by the curvature radius,and the single-degree-of-freedom vibration model is established to approximate the vibration power and exciting force.The finite element model was used to solve the vibration parameters,and the general law of the natural frequency and the position of the node with the increase of the weight at both ends of the specimen was given.Provides the calculation basis for the design of the parameters of the pipe bending fatigue test device.(4)For the example application of bending resonance of beam members,a bending fatigue test device for the bending of the pipe was designed based on the vibration principle of free restrained beam and a sleeper bending resonance fatigue test device was designed based on the principle of bending vibration of simply supported beams.The finite element analysis was performed on the experimental device to ensure its feasibility of dynamic loading.(5)In order to investigate the feasibility of the method for realizing the bending resonance of beam members and to verify the accuracy of engineering calculations,a number of experiments were conducted using the pipe bending resonance test device as an example.The experimental results show that the fatigue test method based on the bending resonance principle of the beam is feasible,and the error between the engineering calculation result and the experimental result is within 10%.In particular,the error of the finite element algorithm for the natural frequency and node position is within 5%,which verifies that the engineering approximate calculation method is correct.