The article touches upon the problem of physical modeling of fishing twisted filamentary materials, in particular, the justification of the rules of similarity of relative longitudinal, bending and torsional stiffness of filamentary parts. The formulation of the problem is associated with the difficulties of conducting full-scale experiments for designing new fishing gear, as well as with the lack of systematic experiments on measuring the stiffness of synthetic cordage. In connection with this, it becomes necessary to conduct model experiments related to physical modeling of dynamic processes occurring with the cordage under load. There has been calculated the coefficient of proportionality of bending stiffness that determines the ability of filamentary parts and cordage to resist bending. There have been given the formulas that determine the combination of the ratio of bending stiffness to longitudinal stiffness and the dimensionless combination of the ratio of bend-ing stiffness to torsional stiffness. The study allows to predict the behavior and basic properties (di-ameter, density, strength, elongation, etc.) of modern synthetic filamentous fishing gear at the stage of their creation (design).
The article considers the problems of physical modeling of twisted filamentary parts of fishing gear and the similitude rules of bending stiffness of filamentary gear parts (FP). The problems are caused firstly by the scope, high costs and complexity of engineering structures in commercial fishery, and thus it was impossible to use them in full-scale testing. Secondly, the lack of systematic experiments prevented from measuring the bending stiffness of synthetic rope parts of fishing gear (SRP). Thus, it becomes necessary to conduct model experiments related to physical modeling of dynamic processes occurring in twisted fishing gear, as well as to carry out a detailed study of the theory of similarity. An attempt to evaluate the bending stiffness of a full-scale object made of polyamide (diameter = 10 mm, the object length and pin diameter were found using large-scale physical characteristics) based on the analysis of experimental data on bending stiffness of synthetic filamentous gear parts made of polyamide with different diameter and length (length = 0.08; 0.10; 0.12; 0.16; 0.20, 0.24 m and diameter = 1.10; 2.0; 3.10; 4.0; 5.0, 6.0 mm) defined on the pins with diameter = 2.0, 10.0 and 30.0 mm. The obtained data will help to prove the correctness of using the theory of dynamic similarity in the course of justification of similarity rules of bending stiffness of the large-diameter cordage and to determine the basic physical and mechanical properties necessary for modeling industrial fishing gear.
The article focuses on the problem of physical modeling of the physical and mechanical properties of fishing twisted filamentary materials, in particular, the most important one – the breaking load. The problems arise because of conducting full-scale experiments, particularly when the ropes of large diameter are used to build the rope parts of fishing gear. The solution to the problem of determining the breaking load on filamentary parts can be found by using specialized tensile testing machines and modern software, which is an effective tool for predicting the reliability and a resource of a gear part operating in difficult conditions of dynamic and shock loads. However, de-signing of fishing gear must begin with large-scale modeling, which will help to correctly calculate the physical and mechanical properties of the designed object using the well-known parameters of the full-scale material. The similarity rules of breaking load of fishing twisted filamentary gear used for the construction of industrial fishing tools will make it possible to model new elements of these tools without conducting full-scale experiments. At the same time, they will already contain solutions to problems associated with studying the dynamic processes, deformation, fracture, as well as the prediction of reliability and resource of the material. The technique proposed based on determining the scale of similarity of filamentary gear made of polyamide fibers, will help to simu-late various net and rope elements from filaments gear of various sizes and structures, instead of conducting energy-intensive experimental studies on ropes of large diameter.
An important task of mechanics of synthetic fishing twisted rope and string products and braided cords is to create a fundamental basis for describing their fracture processes during deformation in operation, i.e. to develop a framework for fracture mechanics (building models and algorithms for calculating structures and technological processes at large plastic deformations, taking into account fracture). There is considered the necessity of developing and introducing the simple and at the same time effective criteria of destruction, allowing to estimate reliably the conditions of safe operation of twisted rope and string products, threaded products and braided cords and especially the structures of industrial fishing gear. Determination of stress concentrations, is an obvious task in connection with the creation of new fishing trawls, purse seines and grips with complex shape-changing geometry. This problem is actual for many branches of industry, including transport and machine-building, where at the designing stage it is necessary to take into account possible emergency situations caused by intensive dynamic effects in twisted rope and string, threaded products and braided cords. Components and structures of twisted rope and string products, threaded products and braided cords should withstand the specified loads in a wide range of loading rates. In particular, the theory allows to solve nonlinear problems, taking into account changes in geometry of deformable twisted rope and string products, threaded products and braided cords, as well as to obtain analytical solutions of various problems.
The force performance of trawl systems directly depends on the work performed by these forces.The mechanical work of a trawl system is a physical quantity that depends on the vectors of force (hydrodynamic, tension, compression, etc.) and displacement. Thermodynamic work is the amount of energy transmitted or received by the trawl system by changing its external parameters. There is also the work of the forces of the electrostatic field when the charge moves from one point of the field to another. Equations are obtained for ideal flexible steel ropes and rope-rope products, characterizing the direct proportionality of the ratio of the productivity of forces that are directed perpendicular to each other and depend on the Poisson's ratio and the constructive elongation of ideal flexible steel ropes and cordage products. The ratio of the capacities of the forces or the ratio of the moduli of elasticity in the transverse and longitudinal directions, which arise when steel ropes and rope-rope products are stretched, are inversely proportional to the square of the coefficient k connecting the elongation λ, Poisson's ratio μ and the relative elongation ε at a constant volume of the product and its mass. There has been described an example of stretching perfectly flexible steel ropes and cordage. Such constructive parameters as lay, the number of strands, wire and fiber thickness, type of weaving were not taken into account.
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