Stability of Rotating Composite Thin-Walled Boring Bar Under Hygrothermal Environment

The chatter of a boring system with a rotating composite thin-walled cutter bar is investigated in this paper. In the case of carbon nanomaterials (CNTs) considered, the hygrothermal strain is introduced into the visco-elastic constitutive relationship of the composite material, and the kinetic and strain energies of the composite cutter bar are derived based on the Love’s shell theory, and the work done by three forces such as the regenerative cutting force, the process damping force and dissipation force of the Kelvin–Viogt is considered respectively. Subsequently, the partial differential control equations of the composite thin-walled rotating cutter bar is presented based on the extended Hamilton principle. Combining the boundary conditions, the discrete equations are obtained by using the Galerkin method. The modal loss factor of the composite cutter bar is calculated by the energy method, and the critical speed is obtained by utilizing the method of eigenvalue analysis and the natural frequency–speed curve is acquired. The influence of various parameters of the boring system on the stability is explored and the stability lobe diagram (SLD) is predicted by using of the semi-discrete method in the time domain. The results indicated that, under the circumstance of different modes, the hygrothermal effect has a significantly effect on the internal damping of the composite bar embedded-CNTs, and it also causes changes in the natural frequency and critical speed of the composite bar as well as the damping and stability zone in higher rotational speed.