CN109446565B

CN109446565B - LS-Dyna-based fly net-target object collision dynamics analysis method

Info

Publication number: CN109446565B
Application number: CN201811113702.5A
Authority: CN
Inventors: 黄攀峰; 余航; 张帆; 孟中杰; 张夷斋; 刘正雄; 董刚奇
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2018-09-25
Filing date: 2018-09-25
Publication date: 2021-06-11
Anticipated expiration: 2038-09-25
Also published as: CN109446565A

Abstract

The invention relates to a flying net-target collision dynamics analysis method based on LS-Dyna, which utilizes nonlinear finite element analysis software ANSYS/LS-Dyna to carry out typical rigid-flexible collision dynamics analysis of a flying net-target, and establishes a flying net-target collision dynamics model in LS-Dyna; performing data processing on the calculation result of LS-Dyna in MATLAB; and analyzing the characteristics of the flying net-target object collision process according to the processed data. Compared with the prior art: compared with the traditional theoretical analysis method, the method is simpler, and the multi-agent can be better controlled for the flying net carried by the multi-agent to complete corresponding tasks. The fly net-target collision dynamics simulation model established through ANSYS/LS-Dyna can also carry out relevant verification on the traditional rigid-flexible collision theory.

Description

LS-Dyna-based fly net-target object collision dynamics analysis method

Technical Field

The invention belongs to the technical field of computer aided engineering, and relates to a flying net-target collision dynamics analysis method based on LS-Dyna.

Background

The collision dynamics problem of the flexible flying net and the rigid target relates to various fields of spaceflight, transportation, construction and the like. In the field of aerospace, a space flying net can be used for capturing space garbage such as a waste spacecraft, and the capturing process is a typical collision process of a flexible flying net and a rigid target; in the transportation field, the flexible flying net carried by the multi-agent can be used for the transportation of valuables in disaster sites, the transportation of large heavy objects by unmanned aerial vehicles and other scenes; in the field of construction, flexible flying nets carried by multiple intelligent agents are used for operations such as overhead transportation and the like.

CAE (computer aided engineering) is widely used in the fields of structures, fluids, electric fields, magnetic fields, acoustic fields, etc. The main idea is the discretization of the structure, namely, each discrete unit is analyzed and calculated by a finite element method, so that an approximate result meeting the engineering precision is obtained to replace a real result. CAE techniques can be used to solve some complex problems that are difficult to calculate using theory.

LS-Dyna is one of CAE software, and is mainly used for nonlinear dynamics problems of collision, explosion, penetration, metal forming and the like of two-dimensional and three-dimensional nonlinear structures. For the problem of collision dynamics of the flexible flying net and the rigid target, theoretical methods are difficult to research, and experimental environments are difficult to realize, so that verification is difficult. When modeling the collision process of the fly net and the target object by using the nonlinear finite element analysis software LS-Dyna, the connecting tether between the nodes of the fly net can be used as a thin rod only subjected to unidirectional axial force, and the LINK167 rope unit in the LS-Dyna has the characteristic. LS-Dyna belongs to software under ANSYS flags, and the traditional interface operation of ANSYS is difficult to draw a topology structure of a fly net, so that the method is carried out based on APDL command streams of ANSYS.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a flynet-target object collision dynamics analysis method based on LS-Dyna, which solves the problems existing in the context of rigid-flexible collision application.

Technical scheme

A flying net-target object collision dynamics analysis method based on LS-Dyna is characterized by comprising the following steps:

step 1, establishing a fly net-target collision dynamics model in LS-Dyna:

1.1) opening LS-Dyna software, selecting an added unit type in a preprocessor toolbar of a main menu, and setting real parameters and material parameters;

1.2) drawing a three-dimensional model of the fly net: selecting creation points in a modeling toolbar of a main menu, wherein the number of the points is 11 x 11, selecting a straight line creation command in the modeling toolbar again, and connecting adjacent points into a straight line to form the appearance of the flying net;

drawing a three-dimensional model of the cutin measuring block: selecting a sphere to be created by using a creating body command in a modeling toolbar of a main menu;

drawing a three-dimensional model of the target: selecting a cylinder to be created by using a creator command in a modeling toolbar of a main menu, wherein the axis is vertical to the plane of an initial node of the fly net;

1.3) carrying out grid division on the angular mass block and the target object: using a shifting command in a modeling toolbar of a main menu, selecting a type of a grid to be divided as a free grid, wherein objects are four corner mass blocks, and grid units are tetrahedrons; using the shifting command again, selecting the type of the grid to be divided as a mapping grid, wherein the object is a target object, and the grid unit is a hexahedron;

1.4) setting the contact type and the solution condition of the flying net-target collision dynamics simulation: selecting an LS-Dyna Option command in a preprocessor toolbar of a main menu, opening a contact definition dialog box, setting the contact type to ANTS, setting the object to be a flying net and a target object, and defining the friction coefficient of the contact;

opening a contact definition dialog box again, setting the contact type as ASSC and the object as four corner mass blocks, and defining the friction coefficient of contact;

selecting an Initial Velocity command in a Solution toolbar of a main menu, setting objects as four corner mass blocks, wherein the speed is 0.5m/s, and the direction points to a target object along a vertical flying net plane;

1.5) selecting a Write Jobname.k command in a Solution toolbar of a main menu, and exporting a model into a k file which can be identified by an LS-Dyna solver; opening LS-Dyna Solver, selecting a solution file as a generated k file, and starting to solve to finally obtain a 3dplot file;

step 2, carrying out data processing on the calculation result of LS-Dyna in MATLAB:

2.1) importing a 3dplot file generated by an LS-Dyna solver into an LS-prepost, selecting NODEs with the type of NODE in a History toolbar, clicking each NODE of the fly net by a mouse, and storing relevant data such as the position of each NODE and the speed at a central NODE;

2.2) importing the position data of each node into the MATLAB, drawing a space position graph of each node of the flying net and the target at different moments, and connecting each adjacent node to obtain a collision process schematic diagram of the flying net and the target;

2.3) extracting the position data of each node at the diagonal of the fly net, and respectively drawing a position-time image of each node in a certain direction in the same graph;

2.4) importing speed data of a central node in the advancing direction of the flying net in an MATLAB, and drawing a speed-time image;

step 3, analyzing the characteristics of the flying net-target object collision process according to the processed data:

according to the schematic diagram of the flying net-target object collision process obtained in the step 2.2), the net type change of the flying net-target object collision process can be analyzed, and whether the flying net can completely envelop the target object or not can be checked;

according to the position-time image of each node at the diagonal line obtained in the step 2.3), the initial collision time of the flying net-target object and the initial collision time between the horny measuring blocks can be obtained through analysis;

according to the speed-time image of the central node of the flying net obtained in the step 2.4), the first collision time of the central node and the target object, the speed of the collision process and the change trend of the speed can be obtained through analysis.

Advantageous effects

Compared with the prior art, the flying net-target collision dynamics analysis method based on LS-Dyna provided by the invention has the following beneficial effects:

(1) the typical rigid-flexible collision dynamics analysis of the fly net-target object is carried out by utilizing nonlinear finite element analysis software ANSYS/LS-Dyna, compared with the traditional theoretical analysis method, the method is simpler, and as the industry authority software, the ANSYS internal algorithm has higher reliability.

(2) After the collision dynamics modeling of the flying net-target object is completed, the method is favorable for better selecting the conditions for grabbing the target object by the flying net in engineering. The multi-agent can be better controlled for the flying net carried by the multi-agent to complete corresponding tasks.

(3) The fly net-target collision dynamics simulation model established through ANSYS/LS-Dyna can also carry out relevant verification on the traditional rigid-flexible collision theory.

Drawings

FIG. 1: flight network-target object collision dynamics simulation flow chart

FIG. 2: schematic view of flying net structure

FIG. 3: schematic structure of horny mass

FIG. 4: schematic diagram of target structure

FIG. 5: simulation effect diagram of flying net-target object collision process

a: simulating an effect graph of the flying net-target object collision dynamics at the time of 0 s;

b: simulating an effect graph of the flying net-target object collision dynamics at the moment of 3 s;

c: simulating an effect graph of the flying net-target object collision dynamics at the time of 5 s;

d: simulating the effect graph of the flying net-target object collision dynamics at the time of 8 s;

e: simulating an effect graph of the flying net-target object collision dynamics at the time of 12 s;

f: simulating an effect graph of the flying net-target object collision dynamics at the moment of 15 s;

FIG. 6: position simulation result graph of each node of flying net in Y direction

FIG. 7: position simulation result graph of each node of flying net in Z direction

FIG. 8: speed simulation result graph of flying net central node in Y direction

Detailed Description

The invention will now be further described with reference to the following examples and drawings:

1) a fly net-target collision dynamics model was built in LS-Dyna.

As shown in fig. 1, which is a flow chart of a simulation of the flying net-target collision dynamics, the setting of the cell type and the material type is performed first. And (3) opening LS-Dyna software, selecting an added unit type in a preprocessor toolbar of a main menu, setting real parameters, material parameters and the like. The LINK167 unit is selected as the unit type of the flying net, and the SOLID164 unit is selected as the unit type of the corner mass block and the target object of the flying net. Real parameters of the LINK167 unit such as cross-sectional area, initial elongation, etc. are set. The material properties of the fly net, the cuticle mass and the target object, such as elastic modulus, density and poisson's ratio, are set.

And establishing a geometrical model of the fly net, the cutin measuring block and the target object. As shown in fig. 2, which is a schematic structural diagram of the flying net, the flying net is composed of 11 × 11 nodes and 220 tether units, the distance between each two adjacent nodes is 0.5m, a creation point is selected from a modeling toolbar of a main menu, the number of the creation point is 11 × 11, a straight line creation command in the modeling toolbar is selected again, and the adjacent points are connected into a straight line to form the appearance of the flying net; selecting a sphere to be created by using a creating body command in a modeling toolbar of a main menu, wherein the structure of a cutin measuring block is shown as a schematic diagram in fig. 3, and the cutin measuring block is located at four corners of a flying net and is a sphere with a radius of 0.07 m; using the create body command in the modeling toolbar of the main menu, a cylinder to be created is selected, and the axis is perpendicular to the plane of the initial node of the fly net, as shown in fig. 4, the structure diagram of the target object is shown, and the target object is set to be a cylinder with the axis perpendicular to the plane of the fly net, the height of the cylinder being 2m, and the radius of the cylinder being 1 m.

And meshing the angular mass block and the target object. The fly net is composed of 11 × 11 nodes and LINK167 units, so that the fly net does not need to be subjected to meshing; using a shifting command in a modeling toolbar of a main menu, selecting a type of a grid to be divided as a free grid, wherein objects are four corner mass blocks, and grid units are tetrahedrons; and using the shifting command again, selecting the type of the grid to be divided as a mapping grid, wherein the object is a target object, and the grid unit is a hexahedron.

Application of fly-net-target collision dynamics boundary conditions. The component names of the material 1 node and the material 2 node are TABLE, MASS and AIM respectively. Defining the contact type between the flying net and the target object as ANTS, namely point-to-surface automatic contact; the type of contact between the cuticle masses and the target is defined as ASSC, i.e. automatic single-sided contact. And applying initial speed load to the four corner mass blocks to enable the cutin mass blocks to carry the flying net to collide with the target object.

And leading the preprocessed model into an LS-Dyna solver for solving. And (3) leading the established model into a k file which can be identified by an LS-Dyna solver, loading the k file into the LS-Dyna solver, setting the size of an occupied memory and the number of CPU cores, and finally generating a post-processing file in a 3dplot format.

2) And (4) performing data processing on the calculation result of the LS-Dyna in MATLAB.

As shown in a flight-target collision dynamics simulation flowchart of fig. 1, a file generated by an LS-Dyna solver is imported into an LS-prefix, and relevant data such as the positions of nodes and the speed at a central node are stored and exported.

Importing node position data into the MATLAB, drawing node position images by using plot3 or line3 functions, connecting adjacent nodes by straight lines to form a fly net, drawing a cylindrical model in the MATLAB according to the height of the cylindrical target object, the radius of the bottom surface and the coordinates of the centers of the two bottom surfaces, and outputting the data by setting one frame per second to obtain a collision process schematic diagram of the fly net and the target object.

Position data of nodes at diagonal lines, i.e., nodes 1, 13, 25, 37, 49, 61 are extracted, and position-time images of the nodes are respectively drawn with different line types in the same graph. And importing the speed data of the central node into the MATLAB, and drawing a speed-time image of the flying net central node in the flying net movement direction.

3) And analyzing the characteristics of the flying net-target object collision process according to the processed data.

Fig. 5 is a graph showing the effect of the simulation of the flying net-target collision dynamics at the time points of 0s, 3s, 5s, 8s, 12s and 15 s. Analysis shows that the flying net-target object collides in 5s, the closing area is gradually reduced in the flying net movement process, and the target object can be completely enveloped finally.

As shown in fig. 6, which is a diagram of a simulation result of positions of nodes of the femto in the Y direction, it can be found that the position change of the edge node, i.e., node 1, is the largest, and the central node, i.e., node 61, may oscillate due to the effect of the collision force. Fig. 7 is a graph showing the position simulation result of each node of the flying net in the Z direction, and it can be found that the position of the edge node, i.e. the node 1, has a sudden change in 15s because of the first collision between horny gauge blocks at the moment.

Fig. 8 is a graph showing a speed simulation result of a central node of the flying net, i.e., a node 61, in the Y-axis direction, and it can be seen from the graph that the initial collision of the central node and the target object occurs in 6.4s, the maximum speed in the collision process can reach 2.4m/s, and the speed in the collision process is in a tendency of decreasing oscillation along with the increase of the number of times of collision, because energy loss occurs in the rigid-flexible collision process.

Claims

1. A flying net-target object collision dynamics analysis method based on LS-Dyna is characterized by comprising the following steps:

step 1, establishing a fly net-target collision dynamics model in LS-Dyna:

1.2) drawing a three-dimensional model of the fly net: selecting creation points in a modeling toolbar of a main menu, wherein the number of the points is 11 x 11, the distance between every two adjacent nodes is 0.5m, and selecting a straight line creation command in the modeling toolbar again to connect the adjacent points into a straight line to form the appearance of the flying net; the cutin gauge blocks are positioned at four corners of the flying net and are spheres with the radius of 0.07 m;

2.1) importing a 3dplot file generated by an LS-Dyna solver into an LS-prepost, selecting NODEs with the type of NODE in a History toolbar, clicking each NODE of the fly net by a mouse, and storing the position of each NODE and the speed data at the central NODE;