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    • 专利摘要:
    Non-destructive method to determine the resistance to the opening of the meshes of a network, comprising the steps of: (a) distancing two knots of the network from each other aligned in the T-direction of the meshes, so that said distancing is produce along said T-direction, allowing the rest of the knots in the network to move freely; (b) measure the distance between said knots and the force applied on them; (c) recording said pair of force and distance measurements; (d) repeating steps (a) to (c) for different degrees of distance between the nodes. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2681921A1
    申请号:ES201700231
    申请日:2017-03-17
    公开日:2018-09-17
    发明作者:Manuel Jesús GONZÁLEZ CASTRO
    申请人:Universidade da Coruna；
    IPC主号:
    专利说明:

     5 10 15 DESCRIPTION NON-DESTRUCTIVE METHOD FOR DETERMINING THE OPENING RESISTANCE OF THE NETWORK FAILURES This disclosure refers to a non-destructive method for determining the resistance to the opening of the meshes of a network. STATE OF THE PREVIOUS TECHNIQUE The nets are mostly used in the manufacture of fishing tackle. In this application, networks with diamond or diamond-shaped meshes predominate, whose T-direction (1) and whose N-direction (2) are represented in Figure 1. These addresses are defined in International Standard ISO 1107. In recent years there is a tendency to use networks with thicker and more robust wires to increase their resistance and durability. These networks have a greater resistance to the opening of meshes, which makes it difficult to open the meshes in the T-direction (figure 2) compared to the opening in the N-direction (figure 3). Experimental studies show that resistance to opening has a great impact on the behavior and structural response of fishing nets. For example, it plays a crucial role in reducing the selectivity observed in fishing tackle made with thicker wire nets. Therefore, it is of great interest to develop theoretical models and test methods to measure the resistance to the opening of meshes, with the aim of being able to predict the behavior of the networks. Theoretical models to describe the resistance to the opening of meshes relate the forces applied on the meshes with the deformations thereof. The article "Bending of twines and fibers under tension", 2002, J Text Inst 93: 1-10 (O'Neill), describes a model in which the threads of the mesh are considered as bi-recessed beams. In this model, the resistance to opening depends on the flexural stiffness of the thread and the geometric properties of the mesh, such as the length of the thread between knots and the angle formed by the threads with the N-direction of the mesh at the junction points with the knots. O'Neill provides two versions of his model: an exact version of great mathematical complexity, and an asymptotic version much simpler than the previous one. The article "Nonlinear Stiffness Models of a Net Twine to Describe Mesh Resistance to 25 Opening of Flexible Net Structures ", 2016, J of Eng for the Maritime Env (de la Prada and González) describes other theoretical models of resistance to the opening of net meshes. These models are approximations of the proposed bi-recessed beam model in (O'Neill, 2002), calculated using the finite element method The first method to measure the resistance to the opening of net meshes was described in the article "Experimental method for quantifying resistance to the opening of netting panels" , 2007, ICES J Mar Sci 64: 1573-1578 (Sala et al.) This method extends a rectangular sample of network in T-direction and N-direction simultaneously, measuring in both directions both the applied forces and the length of the extended sample Next, the flexural stiffness of the thread and the geometric properties of the net sample (length of the thread between nodes, size of the knots and angle of the threads at their ends) are estimated by regr The experimental data obtained using the theoretical model for opening resistance called asymptotic model 15 described in (O'Neill, 2002). This method requires an instrument capable of extending the network sample simultaneously in T-direction and N-address. IT 1395481, 2012 (Buglioni et al) describes an instrument with these characteristics. This instrument is expensive, complex and complicated to handle. 20 Another method was described in the paper "Investigation of methods for the assessment of the flexural stiffness of netting panels", 2011, Proc. of DEMaT'11 Workshop, Split, Croatia (Priour and Cognard). This method is based on measuring the deformation of a rectangular sample of net arranged in cantilever and subjected to bending due to its own weight. 25 Another method was described in patent ES 2546742 A 1, 2016 (González and de la Prada) and in the article "Quantifying mesh resistance to opening of netting panels: experimental method, regression models, and parameter estimation strategies", 2015, ICES J Mar Sci 72: 697-707 (de la Prada and González). In this method the extension of the network sample is carried out in the T-direction of the meshes, leaving free the deformation of the meshes in the N-direction. The flexural stiffness of the wire and the geometric properties of the network can be estimated by analyzing said experimental data. Another method was described in the article "Finite element model for the assessment of the mesh resistance to opening of fishing nets", 2016, Ocean Engineering (Morvan et al). This method proposes a new theoretical model to describe the resistance to opening, based on the finite element method. The introduction of this article contains 35 an analysis of the existing methods to determine the resistance to the opening of meshes. The authors select as the most convenient experimental method the one described in the article (de la Prada and González, 2015), also described in the patent ES 2546742 A 1, 2016 (González and de la Prada). EXPLANATION OF THE INVENTION The present disclosure describes a non-destructive method to determine the resistance to the opening of the meshes of a network, by means of the T-direction spacing of two 10 nodes of the network aligned in said T-direction, leaving free the movement of the rest of knots. Said method has a first phase comprising the following stages: (a) distance two nodes of the network aligned in the T-direction from the meshes, so that said distancing occurs along said T-direction, allowing the rest of the network nodes to move freely; (b) measure the distance between said nodes and the force applied on them; (c) record said pair of force and distance measurements; (d) repeat steps (a) to (c) for different degrees of spacing between the nodes, thus obtaining a set of experimental data that characterize the resistance to the opening of the network. The method may include a second phase of analysis of said experimental data that comprises adjusting a theoretical model of resistance to the opening of meshes to the experimental data, in order to estimate the parameters of the theoretical model. In particular, the method may comprise the following additional step to be carried out following those set forth for the first phase: - based on the set of pairs of force and length measurements previously obtained, estimate the parameters of a theoretical model describing the resistance at the opening of the meshes of the network through mathematical relations between the forces applied to the meshes and the deformations thereof. 35 Once the theoretical model parameters have been estimated, this model can be used to predict the deformation of the net meshes according to the forces acting on them. The existing methods to determine the resistance to the opening of the meshes of a 4network obtain experimental data by applying extensions and / or push-ups on all meshes of a network sample. For this they need actuators and / or fastening means that prescribe the movement of all the meshes of the sample in one or several directions. However, the method described in the present disclosure acts only on two nodes, leaving the movement of the rest of the nodes of the network free. An advantage of the invention is that it is not necessary to cut a network sample in order to perform the test that allows the experimental data to be obtained, but it is possible to perform it directly on the entire network, acting on two of its nodes 10 but without damaging it. This advantage makes it possible to use the method described in the present disclosure to measure the resistance to opening of fishing net meshes that are in use: for example, to verify that their resistance to opening is within an appropriate range of values, or to study how this property varies throughout the life of the network. Another advantage of the invention is that it greatly reduces the size of the instrument necessary to obtain the experimental data. This is because you do not need a structure that holds a network sample by its perimeter. It is enough with a device that gradually distances two knots of the network and measures the distance between them and the applied force. This advantage facilitates the transport of said instrument, for example to carry out 20 on-site tests on nets on board fishing boats. BRIEF DESCRIPTION OF THE DRAWINGS Additional features and advantages of the invention will become clear from the following detailed description of an embodiment thereof, given only by way of non-limiting example, referring to the attached drawings, in which: Figure 1 represents a diamond-shaped mesh at rest, with its T-direction (1) and its N-direction (2); Figure 2 depicts a diamond-shaped mesh extended in the T-direction, showing the effect of the opening resistance; Figure 3 depicts an extended diamond-shaped mesh in the N-direction; Figure 4 represents a network, indicating the T-direction (1) and the N-direction (2) of its meshes and two nodes (3,4) aligned in the T-direction; Figure 5 illustrates an embodiment of the invention in which two nodes aligned in the T-direction are spaced along said direction while leaving the freemovement of the rest of the network nodes; Figure 6 shows the instrument used in an embodiment of the invention; and Figure 7 represents the distance in millimeters between two nodes of the network (vertical axis) versus force in Newtons applied on them (horizontal axis): the circles represent 5 experimental data obtained from a real network and the curve represents the adjustment of a theoretical model obtained through regression analysis of said experimental data. DETAILED EXPOSURE OF EMBODIMENT MODES 10 In a preferred embodiment, the invention provides a non-destructive method for determining the resistance to the opening of the meshes of a network, by the method of obtaining experimental data shown in Figure 5. Figures 4 and 5 show the same network before and during experimental data collection, respectively. The network meshes define two perpendicular directions called T-direction 15 (1) and N-direction (2), as illustrated in Figure 1. These addresses are defined in International Standard ISO 1107. The knots (3 , 4) are aligned in the T-direction. On the nodes (3,4) forces (6,7) of equal magnitude are applied, in the T-direction and in opposite directions, so as to cause the separation of the two knots along the T-direction. In this way, the separation distance (5) between the 20 knots is increased, while the movement of the rest of the network nodes is released. The obtaining of experimental data is carried out by applying different degrees of distance between the nodes (3,4). For each degree of distancing, the force (6.7) applied on said nodes and the distance (5) between nodes associated with that force are measured. In an alternative embodiment, the nodes (3,4) can be moved in the T-direction 25 to generate predetermined distance values (5), and measure the force (6.7) associated with each of said distances. Figure 6 offers another view of the embodiment presented, showing the instrument used to obtain the experimental data. The instrument consists of a linear actuator consisting of a fixed element (8) and a mobile element (9). Said linear actuator is capable of measuring its displacement and the force it exerts. The fixed (8) and mobile (9) elements of the linear actuator have a jaw (10.11) attached to each of them. Each of said jaws (10,11) is placed in contact with one of the nodes (3,4) that are to be distanced, so that when the linear actuator 35 moves its moving element (9) away from the fixed (8) ), the distancing of the nodes (3,4) along the T-direction (2) occurs. The linear actuator causes different grades 6of distance between the nodes (3,4), measuring for each of them the distance (5) between said nodes and the force (6,7) exerted on them. The maximum distance between the nodes (3,4) must not be so high as to cause an appreciable elongation of the threads of the meshes. The number of meshes that separate the nodes (3,4) in the T-direction, which is equal to 3 in Figures 4, 5 and 6, is arbitrary. The result of the process of obtaining experimental data comprises a set of pairs of values (F1, L1), (F2, L2) ... composed of the magnitudes F¡ of the forces applied to the two nodes and their corresponding distances L¡ of separation between 10 knots. The particular characteristics of the instrument used to obtain the experimental data, such as dimensions, materials or techniques of action and measurement, will be independent of the object of the invention. In a preferred embodiment, the invention provides a method for measuring the resistance to the opening of meshes of a network, by means of an experimental data analysis method comprising: (a) A set of pairs of values (F1, L1), ( F2, L2) ... composed of the magnitudes F¡20 of the forces applied to the two nodes and their corresponding distances L¡ between these nodes, obtained with the method of obtaining experimental data described above. For illustrative purposes and without limitation, Figure 7 represents by circles a set of 6 pairs of values (F¡, L¡), i = 1 ... 6, obtained in a polyethylene net with a nominal mesh size of 80 mm and a wire diameter of 4 25 mm, in which the two spaced apart knots were separated from each other by 3 meshes, as in Figures 4, 5 and 6; (b) A theoretical model that describes the resistance to the opening of net meshes, relating the forces applied to the meshes with the deformations thereof. Said theoretical model is a function of a certain number of geometric and mechanical parameters of the network. For illustrative purposes and without limitation, the theoretical model parameters can be: number of meshes m of separation between the two spaced nodes, length b of the nodes measured in the T-direction, flexural stiffness The one of the threads of the meshes, length Ltw Ne of the threads of the meshes and angle e between the threads of the meshes and the N-direction measured at the points of insertion of the threads with the knots. 35 An example of such a model is described in the article (O'Neill 2002). As a consequence of the method used to obtain the experimental data, the force in 7N-direction applied on the distanced nodes is null, which allows to express the theoretical model by means of a mathematical relation of type f (m, F, L, b, El, Ltwine, e) = O; (c) A regression method that allows adjusting the mentioned theoretical model (b) to the mentioned experimental data (a) to estimate the parameters b, El, Ltwine Y e of 5 said theoretical model. During the regression analysis it is necessary to calculate with the theoretical model the length L for a given force value F and certain values of the parameters to be estimated. This is done by solving the mathematical equation of the theoretical model. The results of the analysis include estimates of the model parameters. Figure 7 represents with a curve the fit obtained with the exact theoretical model of (O'Neill 2002) from the set of experimental data represented with circles. For this example, the adjustment estimated the flexural stiffness of the wire as El = 126 N / mm2. The particular characteristics of the theoretical model of resistance to the opening of meshes and of the regression analysis method will be independent of the object of the present disclosure. Although only particular embodiments have been represented and described herein, the person skilled in the art will know how to introduce modifications and replace about 20 technical characteristics with equivalent ones, depending on the requirements of each case, without separating from the scope of protection defined by the claims. attached. 8 
    权利要求:
    Claims (5)
    [1]
    CLAIMS 1. Non-destructive method to determine the resistance to opening of the meshes of a net, which comprises the steps of: 5 (a) distancing two nodes of the net aligned in the T-direction of the meshes from each other, in such a way that said distancing occurs along said T-direction, allowing the rest of the nodes of the network to move freely; (b) measure the distance between said nodes and the force applied to them; (c) recording said pair of force and distance measurements; 10 (d) repeat steps (a) to (c) for different degrees of spacing between the two nodes, thus obtaining a set of experimental data that characterizes the resistance to opening of the mesh of the net.
    [2]
    Method according to claim 1, in which the spacing of the two nodes is carried out by applying a force of predetermined magnitude on them.
    [3]
    3. Method according to claim 1, in which the spacing of the two nodes is carried out by imposing a predetermined distance of separation between them. twenty
    [4]
    4. Method according to any of the preceding claims, comprising the following additional step to be carried out after those set out in claim 1: -based on the set of pairs of force and distance measurements previously obtained, estimating the parameters of a model Theoretical that describes the resistance to opening of the meshes of the network through mathematical relationships between the forces applied to the meshes and the deformations of the same.
    [5]
    Method according to claim 4, in which at least one of said parameters is the flexural stiffness of the threads of the net meshes. 9
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    ES2681921B2|2019-01-29|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    ES2546742A1|2014-03-28|2015-09-28|Universidade Da Coruña|Method to determine the resistance to the opening of the meshes of a network |
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