Sources of nonlinearities, chatter generation and suppression in metal cutting

The mechanics of chip formation has been revisited in order to understand functional relationships between the process and the technological parameters. This has led to the necessity of considering the chip-formation process as highly nonlinear, with complex interrelations between its dynamics and thermodynamics. In this paper a critical review of the state of the art of modelling and the experimental investigations is outlined with a view to how the nonlinear dynamics perception can help to capture the major phenomena causing instabilities (chatter) in machining operations. The paper is concluded with a case study, where stability of a milling process is investigated in detail, using an analytical model which results in an explicit relation for the stability limit. The model is very practical for the generation of the stability lobe diagrams, which is time consuming when using numerical methods. The extension of the model to the stability analysis of variable pitch cutting tools is also given. The application and verification of the method are demonstrated by several examples

Niewymierne funkcje eliptyczne i rozwiązania analityczne dla oscylatora typu SD

The smooth and discontinuous (SD) oscillator is a strongly nonlinear system with an irrational restoring force proposed in P.R.E (2006), which leads to barriers for the conventional methods to investigate the dynamical behaviour directly. In this paper, two kinds of irrational elliptic functions and a kind of hyperbolic functions are defined in the real domain to formulate the analytical solutions of the system. The properties of the functions are obtained including differentiability, periodicity and parity. As the application of the defined irrational functions, the chaotic thresholds of the oscillator are also depicted by using the Melnikov method. Numerical analysis shows the efficiency of the proposed procedure.Oscylator typu gładkiego i nieciągłego (smooth and discontinuous— SD) jest silnie nieliniowym układem mechanicznym z niewymierną siłą restytucyjną opisaną przez P.R.E. w 2006 r. Jej charakter stanowi barierę dla konwencjonalnych metod badania dynamiki oscylatorów SD w sposób bezpośredni. W pracy zdefiniowano dwa rodzaje niewymiernych funkcji eliptycznych i jeden typ hiperbolicznych w dziedzinie liczb rzeczywistych do wyznaczenia rozwiązań analitycznych rozważanego układu. Właściwości tych funkcji obejmują różniczkowalność, okresowość i parzystość. Tak sformułowanych funkcji, jako przykład ich zastosowania, uzyto do określenia zakresów występowania drgań chaotycznych oscylatora przy wykorzystaniu metody Mielnikowa. Symulacje numeryczne potwierdziły efektywność zaproponowanej metody

The design and evaluation of a master of science program in anatomical sciences at Queen's University Canada

The purpose of this study was to describe the design and evolution of a unique and successful Master of Science program in anatomical sciences at one Canadian post-secondary institution and to evaluate its long-term impact on student learning. This program prepares students to teach anatomy and design curricula in the anatomical sciences and is structured around three pillars of competency—content (disciplinary knowledge and transferable skills), pedagogy, and inquiry. Graduates of the program from the last ten years were surveyed, to better understand the knowledge, skills, and habits of mind they have adopted and implemented since completion. Interest was taken in identifying aspects of the program that students found particularly beneficial and areas that needed to be further developed. Based on the findings, this program has been a highly valuable experience for the graduates especially in helping them develop transferable skills, and grow as individuals. The hope is that other institutions that have similar programs in place or are considering developing them would benefit from this description of the program design and the sharing of the lessons learned