Abstract
In this paper, the dynamic model of the rigid space stepped-pipe strings system is derived with Lagrangian method to represent the system dynamic behaviors which enriches the analysis method of longitudinal vibration of stepped-pipe strings. The stepped-pipe strings is constructed of pipes with different diameters and lengths, the physical properties of which mainly depends on the axial force and the depth of deep-sea mining. Based on lumped element method, the heave compensation system with dynamic vibration absorber is designed for longitudinal vibration suppression of the stepped-pipe strings. The analytical solution is obtained by modal analysis method when the mining ship is subjected to sea breeze excitation. The proposed method is easily implementable for rigid space stepped-pipe strings system with complex multi-degree-of-free deep-sea mining dynamic model. Furthermore, the optimal combination of mass ratio, spring coefficient and damping ratio is shown to have a better vibration suppression performance. Finally, numerical simulations on the stepped-pipe strings system with or without dynamic vibration absorbers are provided to demonstrate the effectiveness of the proposed method.
Highlights
With the deceasing of the mineral resources in the land, the exploitation and use of seafloor poly-metallic mineral resources have attracted more and more attention of the global mining industry [1], and the metals in these mineral are essential for various high-tech, green-tech, emerging-tech, and energy applications [2], so the deep-sea mining (DSM) has become an important research subject
Et al indicated that the force more than 3.03xl06N was required to control the longitudinal vibration of the pipe string if the active control was applied on the ship, it is difficult to obtain a lot of power on the ship or the stepped-pipe strings [5]
The heave compensation system of stepped-pipe strings for DSM based on vibration absorber is a complex system, which is composed of several subsystems, each of which has its own natural characteristics
Summary
With the deceasing of the mineral resources in the land, the exploitation and use of seafloor poly-metallic mineral resources have attracted more and more attention of the global mining industry [1], and the metals in these mineral are essential for various high-tech, green-tech, emerging-tech, and energy applications [2], so the deep-sea mining (DSM) has become an important research subject. Computer simulation based design is required to analyze dynamic performance of stepped-pipe strings for the design process.When compared with aforementioned vibration absorbers on the longitudinal vibration of stepped-pipe strings in the DSM system, the dynamic vibration absorber proposed in this paper is different in the following aspects: 1)The Lagrangian equation is used to establish the motion equation of the longitudinal vibration system, which has obvious advantages for the complex coupling stepped-pipe strings system; 2) Analyze the principal vibration mode of stepped-pipe strings under level-6 sea conditions, the deformation characteristics and the main deformation positions are obtained, which provides a basis for the design of the dynamic vibration absorber; 3) attach dynamic vibration absorbers to the stepped pipes with large longitudinal vibration amplitude, and carry out the modal simulation; 4) detailed analytical results are presented to guarantee the dynamic performance improvement of vibration absorber, even in the presence of parameter coupling variation.
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