Regenerative self-excited vibrations (chatter) often occur in boring operation due to low stiffness of a slender cantilever holder of a tool. These vibrations lead to significant defects of a machined surface and cutting tool damages. The new chatter suppression method is proposed in the paper. Displacement signal measured in the direction which is orthogonal to machined surface is used for generating a control action in the feed direction. Linear proportional control law is applied. Mathematical model of boring process dynamics with control has been developed for validation of the proposed method efficiency and searching better values of feedback gain.
A turbofan nonlinear dynamic model is described in the paper. It has been developed for the computation of loads in the engine frame after fan blade-out (FBO) event. The model includes reduced dynamic finite element models of rotors and casings and also nonlinear elements for simulation of "rotor-casing" contact interactions. Thorough attention has been paid to mounts modeling with possible mechanisms taken into account. The engine dynamic behavior during its rotors deceleration to the autorotation mode after the FBO event has been simulated for the following two forward mount arrangement variants: fastening to the inner part of the intermediate casing; fastening to the outer part of the intermediate casing. The effect of load reduction device (LRD)-special elements which are introduced to fan supports, destroyed under certain force and don't transfer improper loads to the engine casing system after the FBO event, has been studied. The analysis of maximum loads on engine mounts has been performed for the two listed design variants for both cases: with and without an LRD in fan supports.
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A dynamic model of the milling process has been proposed that considers deformation of the cutting tool during machine operation. Methods intended for analysis, algorithms, and software have been developed using the finite element method and the static condensation method to reduce the model. The proposed algorithm enables one to take into consider the deformation of the milling cutter under the action of cutting forces, as well as the latter's effect on the formation of the cut layer and the geometry of the resulting surface.
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