Single-input Multiple-ouyput NOFRFs-JS Index Detection Gearbox Case Damage Study

As an important component of a car,the gearbox affects the overall performance of the car,so the damage detection of the box is a key step to verify the product quality.The damage detection and identification of old boxes is a research hotspot in remanufacturing engineering.A nonlinear output frequency response function based on Volterra series theory is proposed to overcome the limitations of the current damage detection methods in remanufacturing engineering(NOFRFs)damage detection method can be used to visually express the damage degree and damaged area of the gearbox body.This paper derived the single input single output(SISO)system with single input multiple output(SIMO)system under the hammer excitation NOFRFs estimation formula,combined with JS divergence(Jensen-Shannon),the concept of two probability distribution of similarity measure,to suggest that JS divergence fatigue damage index based on NOFRFs NJS concept,and gives the NJS corresponding calculation formula,using the Simulink simulation system of one dimension 10 degrees of freedom spring quality,to simulate the vibration system of NJS nonlinear damage detection method for the numerical simulation,Verify the feasibility of the proposed method.The specific process is as follows:by adding nonlinear components to the oscillation system to simulate the damage of parts in the actual service process,and by changing the nonlinear strength of components in the system to simulate the change of different damage degrees in the actual.The simulation results show that the nonlinearity of the system can be judged by the NOFRFs waveform directly observed.Further,a damage index Fe,constructed of NOFRFs combined with JS divergence of building damage index NJS NOFRFs identification results were analyzed,and the analysis results show that by NOFRFs build good damage index Fe can distinguish system nonlinear intensity,while the NJS indicators can better represent the size of the nonlinear system,the greater the damage degree of the system,its NJS value is larger.Under the condition of the same excitation,NJS values at different response points are different,which can be determined according to different positions The nonlinearity of the system is evaluated by the index value of.In order to make the box reach the free boundary condition,the flexible support system is designed for the box.The single input and multiple output hammer test was carried out on the three new and old gearbox bodies provided by remanufacturing company with PULSE Labshop system of B&K Company in Denmark,and the hammer heads of different materials were used to hammer,and the influence of hammer head materials on the data obtained from the hammer test was compared.The damage area with relatively obvious index value was detected and interpolation fitting was carried out in combination with NJS value,and the damage area of the box body was preliminarily evaluated.Finally,ANSYS modeling and simulation are carried out for the box body.Different response points and transient force stress points were set,and a group of cracks with different heights were compared to study the influence of crack height on damage degree.Then the cracks at three different positions with different heights were tested to obtain the numerical value of the potential acceleration of each response point,and the damage of the box was evaluated by combining with NJS index,so as to infer the approximate location of the most serious damage of the box,further evaluate the damage of the box,and complete the visibility expression of the most vulnerable position of the box.