Stanisław Noga

Modelling and Vibration Analysis of Some Complex Mechanical Systems

Development of modern engineering requires technical equipment which is characterized by high stability and operational dependability. This particularly applies to components and assemblies which are employed in the aviation, pharmaceutical and biotechnological industries, and biomedical devices. Each newly produced assembly must pass a cycle of advanced computations and a set of experimental tests which allow it to be used in engineering structures. In many cases the experimental tests are realized in order to verify the analytical results. For economic reasons, the calculations should be executed by using advanced computation techniques and the experimental investigations should be conducted on specially designed test rigs. Such test rigs are required to satisfy specific requirements to guarantee that experiments can be led with high technical quality, and economic reasons demand that the rigs should operate for a long period of time (Friswell & Mottershead, 1995). One of the essential factors, which could disturb or restrict the functioning of devices (rigs and others), are the vibration of the components or assemblies of these systems. So it is advantageous to conduct numerical computations at the design stage, which could restrict the consequences connected with the structure vibration. The rapid development of computer techniques and analytical systems based on the finite element method (FEM) allows a free vibration analysis of large systems of complex design and geometry to be conducted (De Silva, 2005). Some authors, using FEM techniques, analyzed the free vibration of complex structures, which are used as load – bearing elements of building structures (Ansell, 2005). Free vibration analysis of selected steel bridges is conducted in papers of Chung and Živanovic (Chung & Sotelino, 2006; Živanovic et al., 2007). The bridge FE models that are developed are verified on real objects. Zembaty (Zembaty et al., 2006) studied the influence of damage of the base construction frame on the change in the natural frequencies of the system. The gas turbine blade is a very important part of aviation jet engine. Some authors analyzed the influence of friction contact phenomenon in collaboration regions of blades and disk sectors on the dynamic behaviour of the blades (Allara, 2009; Toufine et al., 1999). Some presented results were verified by experimental tests. Free vibration of the blade are developed by Sinha (Sinha & Turner, 2011) using the thin shell theory. The achieved solution includes the effect of warping of the cross – section of the blade. Membrane systems have wide application in different disciplines of engineering. Jaffrin and Tack in their papers (Jaffrin, 2008; Tack et al., 2006) present practical

Dynamic analysis of the sieve in vibrating screener system

Streszczenie: W artykule przedstawiono analizę drgań własnych sita przesiewacza wibracyjnego, stosowanego do przesiewania naturalnie wilgotnych materiałów urobku skalnego. W analizie wykorzystano metodę analityczną oraz metodę numeryczną. W metodzie analitycznej ruch sita przesiewacza opisany został równaniami różniczkowymi cząstkowymi. Rozwiązanie drgań własnych zostało wyprowadzone metodą rozdzielenia zmiennych. Obliczenia numeryczne wykonano wykorzystując metodę elementów skończonych. Wyznaczone częstości drgań własnych oraz postacie drgań własnych porównano z rozwiązaniem analitycznym. Zaprezentowane zostały uproszczenia modelu numerycznego oraz przeprowadzona została analiza wpływu materiału przesiewanego na częstości drgań własnych sita.

The Experimental Investigation Of The Screen Operation In The Parametric Resonance Conditions

Abstract In this paper the experimental studies of the screen working in the parametric resonance condition are discussed. The investigations are conducted for laboratory parametric resonance screen. The measuring test is performed for four cases of tension force values. The full sheet metal instead of the sieve is used. For each considered case the natural frequency of the plate and the parameter modulation frequency are determined. The achieved results are presented and discussed. It is shown that the highest sieve plate amplitude is obtained when the parameter modulation frequency is two times larger than natural frequency of the sieve plate. This parametric resonance vibration was observed only for tension force equal to 4000 N because of the rotational speed limits of electrical vibratos.