Research And Optimization On Mechanical Properties Of Tuna Longline Hooks

This paper reviewed some related literature about materials types,stress, the displacement change, optimization design and testing,mechanics performance testing, finite element analysis of the tuna longline hooks and lifting hooks, etc. The study of the tuna longline hooks material mechanics is relatively rare. The study on the hook simulation, the hook stress analysis, optimization design, economic and social benefits is lacked. This paper suggested that the future study should include(1) the simulation analysis and experiments about tensile, bending,torsion, breaking, the deformation situation of hook;(2) the maximum tensile, bending and torsion load of all kinds of hooks and the distribution of maximum stress and strain;(3) simulating the whole process of hooks fracture;(4) lifting hooks related study methods should be applied to the study of the tuna longline hooks;(5) making full use of mechanic related software, using different ways to simulate hooks shape of space and stress distribution;(6)to understand the economic benefit of the tuna longline hook.Ring hook is replaced by circle hook gradually on tuna longline fisheries in order to reduce sea turtles bycatch and promote eco-friendlydevelopment of the longline fishing gear. Mechanical analysis are carried out on the two kinds of typical tuna hooks(ring hook and circle hook)using finite element analysis method(FEM) by ANSYS. The distribution of equivalent stress, strain and deformation of hook are obtained, and the possible failure condition and the failure type are also analyzed. Intensity examination and optimization design are made on hook structure based on material mechanics theory, comparing with hook’s data obtained in the tensile test. Results showed:(1) Ring hook’s tensile strength is superior to circle hook’s with the same specifications;(2) Hook’s main stress is undertaken by the bend of the hook, and there is a stress Concentration in the hole of hook eye;(3) Increasing the hook circular arc of the bending curvature appropriately and flattening the bends surface, connection of hook eye and shank added with arc transition can avoid stress concentration and enhance the strength of the hook.The hooks’ strain and deformation during the tension test were measured by the optics non- touch deformation measurement system.The hook deformation field was measured by the digital image method.Results of tension test showed that:ring hook and circle hook’s train and deformation during the tension test were measured by the optics non touch deformation measurement system. The hook deformation field was measured by comparing the gray scale of the hook surface image before and after deformation using thedigital image method. Results of tension test showed that: While the tension acted on the circle hook and ring hook was 0-800 N, the highest equivalent strain area of the circle hook and ring hook was in the hook rear bending and rear side of the rear bending, respectively based on the point and field analysis. Result suggested that there was a little difference in the large set deformation and strain between ring hook and circle hook while the tension acted on the hook was the same. the results of point analysis method and audience analysis method have consistency and complementarity. According to the audience analysis, it can visually show the key areas. According to the point analysis, it can get the value of the selected regional points’ displacement and strain. Therefore, the tensile test results should combine the two methods.