Study On Influence Of Dynamic Response Of Bending Machine’s Gear System On Gear Bending Fatigue And Machining Stability

Bending machine is an important equipment for manufacture. Machine components’working status has a certain influence on its life and processing accuracy. As the directdrive device of lower roller, the second-stage gear drive’s dynamic response has greatinfluence on gear’s fatigue life and bending machine’s processing accuracy. Inconventional gear transmission dynamics, nonlinear dynamic characteristics are usuallylinearized, but it will induce big error between real-world status and responsescalculated from the equations. So for the results closer to the real status, severalnonlinear dynamic characteristics are included in dynamic equations in this dissertation,and the influence on gear’s bending fatigue and processing accuracy are estimated basedon dynamic response.First of all, considering the nonlinear meshing stiffness, meshing damping, teethsurface sliding and no-load transmission error, dynamic equations of gear transmissionare established based on vibration theory. Then, each nonlinear parameter is transformedinto Fourier equation because of its periodic variation. After that, stable solutions ofgear drive system are calculated based on harmonic balance method. Results show thatmeshing stiffness and meshing damping are involved into system’s dynamic equationsas time-vary parameters, meanwhile teeth surface sliding friction and no-loadtransmission error are involved into system’s dynamic equations as time-vary excitation.Next, the influence of two important parameters---rotation speed and teeth surfacesliding friction coefficient on bending stress and strain of tooth root are analysed, thenthe influence of these two parameters on crack initialization life and propagation life oftooth root are estimated based on Manson-Coffin theorem and Fracture Mechanicsrespectively. Results show that rotation speed has smaller impact on bending fatigue lifeof tooth root compared with teeth surface sliding friction coefficient because rotationspeed is low.Lastly, influences of dynamic response on steel-plate feed stability and contact point’sposition between lower roller and steel-plate are anlysed, in which consideringfluctuation of response and unsynchronized rotation of two lower rollers. Results showthat unsynchronized rotation speed of two lower rollers has a great influence onsteel-plate feed stability and contact point’s position between lower roller andsteel-plate.