An Improved Method of Minimizing Tool Vibration during Boring Holes in Large-Size Structures

The paper presents a thoroughly modified method of solving the problem of vibration suppression when boring large-diameter holes in large-size workpieces. A new approach of adjusting the rotational speed of a boring tool is proposed which concerns the selection of the spindle speed in accordance with the results of the simulation of the cutting process. This streamlined method focuses on phenomenological aspects and involves the identification of a Finite Element Model (FEM) of a rotating boring tool only and validating it with a real object, while dispensing with discrete modelling of a completely rigid workpiece. In addition, vibrations in the boring process in all directions were observed, which implies a geometric nonlinearity of the process model. During the simulation, the values of the Root Mean Square (RMS) of the time plots and the dominant values of the “peaks” in the displacement amplitude spectra were obtained. The effectiveness of the method was demonstrated using a selected mechatronic design technique called Experiment-Aided Virtual Prototyping (E-AVP). It was successfully verified by measuring the roughness of the indicated zone of the workpiece surface. The economic profitability of implementing the method in the production practice of enterprises dealing with mechanical processing is also demonstrated.

Reproducing laboratory earthquakes with a discrete-continuum model

We present a novel numerical model allowing to take the best part of continuum-based and discrete modelling in a single framework. This model is applied to the reproduction of laboratory earthquakes in a high-pressure triaxial cell. It allows to represent most of the relevant phenomena at stake, including elastic stress build-up during loading, fast and slow sliding events, seismic waves emission in the surrounding elastic medium and evolution of fault gouge on the sliding interface. We review here some illustrative results obtained with this model and propose further research avenues.