Considering fluid-solid coupling and free liquid surface effect of the inner and outer cutting fluid, it is proposed a transverse vibration model for BTA deep-hole boring bar system, in order to reveal the effect of the cutting fluid perturbation on the lateral vibration frequency in such system. Consequently, the first order and second order frequency expressions were analyzed under different conditions. The free liquid surface variation can be indicated by the cross section areas on inner and outer fluids and the added mass from boring bar. By way of calculation, the sensitivities of the frequency in the BTA system to the flow rate of cutting fluid and the axial force of the system can be determined, as well as the tendency of the motion transformation. The sensitivity of transverse vibration frequency of BTA deep-hole boring bar to axial force is as follows: in the resonant ridges region, when there is no free liquid surface both in inner and outer cutting fluids, it is the maximum; when both inner and outer cutting fluids have free liquid surface, it is the minimum; in the resonant wings region, the maximum is when inner cutting fluids have free liquid surface, the minimum is when both inner and outer cutting fluids have no free liquid surface.The sensitivity of transverse vibration frequency of BTA deep-hole boring bar to cutting fluid velocity is as follows: in resonance ridges region, the maximum is when inner cutting fluid has free surface, and the minimum is when inner and outer cutting fluid have no free surface; in resonance wings region, the maximum is when inner and outer cutting fluid have no free surface, and the minimum is when inner cutting fluid has free surface. Bending and buckling would occur once the flow rate of cutting fluid and the axial force get up to the critical equivalence in the system. Further, in case of static instability, under higher flow rate, some complicated motions such as coupling flutter with mixed orders mode would occur in the system. The results above can provide some theoretical guides for the practice in BTA boring machining.
Key words
BTA deep-hole processing /
Free liquid surface /
Transverse vibration frequency /
Sensitivity
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References
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