China
Africa
Explore chapters and articles related to this topic
Machines with Variable Mass
Published in L. Cveticanin, Dynamics of Machines with Variable Mass, 2022
The expression “variable mass system” as used in the context of this book, refers to mechanical systems that lose and/or gain mass while in motion. Examples of such devices abound in contemporary engineering literature (Artobolevskij [1]–[4], Bogolubov [1], Entus [1], Bessonov [1], Ganlin [1], Strzalko & Grabski [1], Cveticanin & Janovic [1]). They include complex systems such as aircraft, rockets, automobiles, moving robots picking up or lifting objects, as well as simpler systems such as transportation machines, mining machines, excavators, vibrating machines used as conveyors, separators, machines for segregation, rolling mills, metallurgical machines, casting machines, agricultural machines, centrifuges, measuring mechanisms, etc. In these mechanisms, the mass of elements and the position of their centre of mass and moment of inertia vary during addition or removal of the material. Variable mass systems can be divided into two classes: those with continuous mass variation and those with discrete mass variation. The focus of the study presented here is on systems with continuously varying mass, with the additional restriction that such systems include a solid main frame and mass variation is a consequence of the motion of the particles which are added to and/or separated from the solid body. It is not an easy task to describe mass variation. Often it is a regularly increasing or decreasing time function, i.e., the mass is being increased or decreased in time. Periodical mass variation is unusual in working machines and mechanisms and will not be considered in this book.
Determination of blasting load history in boreholes based on a variable-mass thermodynamic system
Published in European Journal of Environmental and Civil Engineering, 2022
Kaiwen Song, Xinping Li, Yi Luo, Junhong Huang, Tingting Liu
Figure 9 shows the time history of blasting load on difference key points by both analytical solution and numerical simulation. As shown in Eqs. (25) and (26), the load spacial distribution is not considered in the theory of double exponential function and triangle load, so only the variable-mass system theory is compared with the FSI methods here. The borehole bottom (x = 0), x = 1/3L and x = 2/3L from the borehole bottom are selected as the key points. Considering the randomness caused by element meshing and minimum calculation step in numerical simulation, the results of the FSI and the variable-mass system theory have high consistency. The maximum deviation on the three key points are only 4.9%, 3.8% and 6.1% separately.
Development of a new tuned vibration absorber based on one degree-of-freedom of translational motion
Published in Cogent Engineering, 2021
Abobakr Almashhor, Saeed A. Asiri
In this study, an SDOF TVA has been developed by adding the variable mass system, using the circulation fluid system to change the mass as per the system required. A model graph was extracted using MATLAB software. It was shown from the graphs that by increasing or decreasing the force-frequency, a low peak was developed in the resonance graph. Therefore, to attenuate the vibration, the frequency ratio must fall in that low peak. In particular, reducing the force-frequency will reduce the absorber frequency and require adding fluid to absorber mass. The size of the tank (absorber mass) can be obtained by the less force-frequency when applied to the system. The tank weight (empty) should be applied based on the maximum force.