Research on path planning of autonomous manganese nodule mining vehicle based on lifting mining system.

Deep-sea manganese nodules are abundant in the ocean, with high exploitation potential and commercial value, and have become mineral resources that coastal countries compete to develop. The pipeline-lifting mining system is the most promising deep-sea mining system at present. A deep-sea mining vehicle is the core equipment of this system. Mining quality and efficiency rely on mining vehicles to a great extent. According to the topographic and geomorphic environmental characteristics of deep-sea manganese nodules at the bottom of the ocean, a new deep-sea mining system based on an autonomous manganese nodule mining vehicle is proposed in this paper. According to the operating environment and functional requirements of the seabed, a new mining method is proposed, and the global traverse path planning research of the autonomous manganese nodule mining vehicle based on this mining method is carried out. The arc round-trip acquisition path planning method is put forward, and the simulation verification shows that the method effectively solves the problems of low efficiency of mining vehicle traversing acquisition and obstacle avoidance.

Underwater Undulating Propulsion Biomimetic Robots: A Review.

The traditional propeller-based propulsion of underwater robots is inefficient and poorly adapted to practice. By contrast, underwater biomimetic robots show better stability and maneuverability in harsh marine environments. This is particularly true of undulating propulsion biomimetic robots. This paper classifies the existing underwater biomimetic robots and outlines their main contributions to the field. The propulsion mechanisms of underwater biomimetic undulating robots are summarized based on theoretical, numerical and experimental studies. Future perspectives on underwater biomimetic undulating robots are also presented, filling the gaps in the existing literature.

The Analysis of Biomimetic Caudal Fin Propulsion Mechanism with CFD.

In nature, fish not only have extraordinary ability of underwater movement but also have high mobility and flexibility. The low energy consumption and high efficiency of fish propulsive method provide a new idea for the research of bionic underwater robot and bionic propulsive technology. In this paper, the swordfish was taken as the research object, and the mechanism of the caudal fin propulsion was preliminarily explored by analyzing the flow field structure generated by the swing of caudal fin. Subsequently, the influence of the phase difference of the heaving and pitching movement, the swing amplitude of caudal fin, and Strouhal number (St number) on the propulsion performance of fish was discussed. The results demonstrated that the fish can obtain a greater propulsion force by optimizing the motion parameters of the caudal fin in a certain range. Lastly, through the mathematical model analysis of the tail of the swordfish, the producing propulsive force principle of the caudal fin and the caudal peduncle was obtained. Hence, the proposed method provided a theoretical basis for the design of a high-efficiency bionic propulsion system.

A Hyper-Elastic Creep Approach and Characterization Analysis for Rubber Vibration Systems.

Rubber materials are extensively utilized for vibration mitigation. Creep is one of the most important physical properties in rubber engineering applications, which may induce failure issues. The purpose of this paper is to provide an engineering approach to evaluate creep performance of rubber systems. Using a combination of hyper-elastic strain energy potential and time-dependent creep damage function, new creep constitutive models were developed. Three different time-decay creep functions were provided and compared. The developed constitutive model was incorporated with finite element analysis by user subroutine and its engineering potential for predicting the creep response of rubber vibration devices was validated. Quasi-static and creep experiments were conducted to verify numerical solutions. The time-dependent, temperature-related, and loading-induced creep behaviors (e.g., stress distribution, creep rate, and creep degree) were explored. Additionally, the time-temperature superposition principle was shown. The present work may enlighten the understanding of the creep mechanism of rubbers and provide a theoretical basis for engineering applications.

Dislocation Evaluation of Fe Twist Grain Boundary Based on Molecular Dynamics.

The grain boundary and dislocation motion characteristics on the atomic scale are significant for the study of material failure mechanisms. In the present work, by theoretical analysis and numerical simulation, the most stable phase of Fe crystal under given conditions is confirmed. Distribution of dislocation potential under different torsion angles is studied for BCC-Fe (001) twist grain boundary. The dislocation motion in Fe (001), Fe (110) and Fe (111) twist grain boundary under tension, compression and shear loading are also investigated.

Damage detection of offshore platforms using acoustic emission analysis.

This paper aims to detect the structure damage in KT type jacket offshore platforms using acoustic emission analysis. Experimental investigation has been implemented to analyze the transmission characteristics, attenuation law, and source localization of the acoustic emission signals. The range of energy attenuation coefficient α and the signal amplitude attenuation law were obtained from experimental data. Hence, the layout of acoustic emission sensors was optimized based on the energy attenuation to achieve online damage monitoring for KT-jacket platforms. In order to validate the performance of the optimized sensor layout, another experimental test was conducted on the designed KT-jacket offshore platform to locate the acoustic emission sources. The test results demonstrate that a positioning error of 8 mm or below can be obtained using the optimized sensor layout, and the number of sensors can be reduced by 80% compared with that of the theoretical layout. As a result, the optimized sensor layout enables efficient and effective damage detection for KT-jacket offshore platforms.