Method for analyzing near-field release dynamic characteristics of fiber optic cable based on finite element method

Abstract

The application discloses a kind of based on finite element method's optical fiber line package near-field release dynamics characteristic analysis method, specifically: step 1, establish optical fiber line package precision winding digitization model and core cylinder entity model, and the assembly model is obtained by assembling optical fiber line package and core cylinder;Step 2, establish optical fiber line package line guide optical fiber equivalent physical model and obtain the cohesion physical property parameters of optical fiber line package;Step 3, establish the finite element model of optical fiber line package near-field high-speed release;Step 4, add constraint condition to the finite element model of optical fiber line package near-field high-speed release;Step 5, using the finite element model of optical fiber line package near-field high-speed release added constraint carries out optical fiber line package near-field high-speed release dynamics characteristic analysis.The application solves the problem that existing technology lacks theoretical basis research due to engineering unit, and can only continuously try and error on the basis of process development and experiment to improve product performance and reliability.

Description

Technical Field

[0001] This invention belongs to the technical field of optical fiber guidance methods, and relates to a method for analyzing the near-field release dynamic characteristics of optical fiber coils based on the finite element method. Background Technology

[0002] Wire-guided optical fiber is an important component of fiber-optic guided missiles. The spindle-shaped solid optical fiber bundle, formed by tightly winding the wire-guided optical fiber around the surface of a frustum-shaped core cylinder, is installed at the tail of the missile. As the missile flies, the wire-guided optical fiber is released at high speed and in an orderly manner from the surface of the optical fiber bundle into free space from the tail of the missile. The function of the wire-guided optical fiber is to establish a two-way data transmission channel between the missile and the launch platform.

[0003] During the high-acceleration and high-speed flight of a missile, a high-density fiber optic package contains low-diameter, low-loss optical fibers that are rapidly released from the package surface into free space, exhibiting a helical motion. The velocity of the fiber rapidly decreases, causing it to float in the air. During this high-speed release, tension, friction, gravity, adhesive force, bending shear force, torsional shear force, compressive drag, and inertial force are suddenly applied to the ultrafine fiber. These forces collectively cause the fiber to be released at high speed from the package surface, potentially increasing transmission loss and even causing breakage. Therefore, a near-field high-speed release dynamics analysis considering the forces acting on the fiber in the fiber optic package system is essential. However, fiber optic packages possess unique characteristics, including distinctive fiber materials, special winding requirements, complex structures, numerous contacts, adhesive coatings between fibers, high release speeds, and numerous and complex loads. Therefore, analyzing the dynamics of the high-speed release of the fiber from the package surface into free space presents significant challenges.

[0004] Currently, there is very little research on the dynamic characteristics of linearly guided optical fibers being released at high speed from the surface of the fiber optic coil into free space. Due to the long-term lack of theoretical research, engineering units can only improve product performance and reliability through trial and error based on a large number of process developments and experiments. This not only results in high development costs and low efficiency, but also leads to certain deviations between experimental results and actual conditions due to the inconsistency between ground experimental conditions and actual launch environments. Summary of the Invention

[0005] The purpose of this invention is to provide a method for analyzing the near-field release dynamics of optical fiber coils based on the finite element method. This method solves the problem in the existing technology where engineering units, lacking theoretical research, can only improve product performance and reliability through trial and error based on process development and experimentation.

[0006] The technical solution adopted in this invention is a method for analyzing the near-field release dynamics of optical fiber coils based on the finite element method, which is implemented according to the following steps:

[0007] Step 1: Establish a digital model of the fiber optic coil precision winding and a physical model of the core cylinder, and assemble the fiber optic coil and the core cylinder to obtain an assembly model;

[0008] Step 2: Establish an equivalent physical model of the fiber optic cable and obtain the cohesive properties of the fiber optic cable.

[0009] Step 3: Based on the digital model of the precise winding of the optical fiber coil established in Step 1 and the equivalent physical model of the optical fiber coil conductor established in Step 2, establish a finite element model of the near-field high-speed release of the optical fiber coil.

[0010] Step 4: Add constraints to the finite element model of near-field high-speed release of the optical fiber coil established in Step 3.

[0011] Step 5: Analyze the dynamic characteristics of near-field high-speed release of the fiber optic coil using a constrained finite element model.

[0012] The invention is further characterized in that,

[0013] Step 1 is as follows:

[0014] Step 1.1: Model the conventional fiber curve and the core tube solid model;

[0015] Step 1.2: Model the first-floor same-layer cross-turn curve;

[0016] Step 1.3: Model the cross-turn curves of non-first-floor same-layer curves;

[0017] Step 1.4: Establish the model of the cross-layer unwinding curve segment;

[0018] Step 1.5: Merge the models established in steps 1.1-1.4 into a complete digital model of precision winding of optical fiber coil, and assemble the optical fiber coil and core tube to obtain an assembly model.

[0019] When performing conventional fiber curve modeling and core cylinder solid modeling in step 1.1, it is necessary to determine the basic parameters of the fiber coil and fiber geometry, including: the large end diameter D of the fiber coil core. b Fiber optic cable core tube taper α, fiber optic cable core tube height L b Fiber diameter d, fiber winding pitch d s Number of unwound turns (M) at the large end of the fiber optic core tube fb Number of unwound turns (M) at the small end of the fiber optic core tube fs M, the total number of turns in the first layer of the fiber optic cable bThe total number of layers N in the fiber optic cable and the total length L of the optical fiber in the fiber optic cable;

[0020] The solid model of the core cylinder is established based on the parameters of the core cylinder;

[0021] Step 1.1, conventional fiber curve modeling, includes curves with no bottom tube winding and curves with a bottom tube winding, each with a corresponding curve equation.

[0022] Step 1.2 The first-layer same-layer cross-turn curve is a standard multi-segment circular arc curve, and there is a corresponding curve equation;

[0023] In step 1.3, there are corresponding curve equations for the non-first-layer same-layer cross-turn curves;

[0024] The cross-layer unwinding curve segment in step 1.4 has a corresponding curve equation.

[0025] The total length L of the optical fiber in the optical fiber bundle in step 1.1 is calculated according to the following formula:

[0026]

[0027] Among them, M n r is the number of turns in the nth layer of the optical fiber sheath. nm Let r be the winding radius of the m-th turn of the n-th layer in the fiber optic cable. b Let t be the radius of the large end of the fiber optic core, Δ be the superposition increment of the fiber optic core, and t be the radius of the large end of the core. nb d is the number of turns of the nth layer unwound from the first layer on the back side of the fiber optic cable. sy For the vertical increment of the same layer of fiber in the fiber optic cable;

[0028] The number of turns M in the nth layer of the optical fiber sheath n Calculate according to formula (2):

[0029] M n =M b -(n-1)(M fb +M fs (2)

[0030] The fiber optic packet superposition increment Δ is calculated according to formula (3):

[0031] Δ=dcos60° (3)

[0032] The number of turns t of the nth layer unwound from the first layer on the back side of the fiber optic cable. nb Calculate according to formula (4):

[0033] t nb = (n-1)M fs (4)

[0034] Fiber optic cable in the same layer of fiber vertical increment dsy Calculate according to formula (5):

[0035] d sy =d s sinα (5).

[0036] Step 2 is implemented as follows:

[0037] Step 2.1: Determine the basic physical properties of the optical fiber structure, including: fiber diameter d and fiber core diameter d0. g Fiber core elastic modulus E g Fiber core shear modulus G g Fiber core Poisson ratio u g Elastic modulus E of coating layer k Coating layer shear modulus G k Coating layer Poisson's ratio u k ;

[0038] Step 2.2: Establish an equivalent physical model of the fiber envelope and wire-guided fiber based on the basic physical property parameters of the fiber structure determined in Step 2.1.

[0039] Step 2.3: Based on the special material of the fiber optic cable binder, the effect of the binder in the fiber optic cable is simulated using a bilinear cohesive force model to determine the basic physical property parameters of the binder.

[0040] Step 2.4: Calculate the initial stiffness coefficient of the binder in Type I, Type II and Type III failure and the total relative displacement δ of the interface of the cohesive model of the binder under mixed loading based on the basic physical property parameters of the binder determined in Step 2.3.

[0041] The equivalent physical model of the fiber optic cable in step 2.2 includes the equivalent model of the axial elastic modulus E of the fiber optic cable. θ Equivalent model of radial elastic modulus of linear fiber E r Equivalent model of shear modulus G for linear fiber and equivalent model of axial Poisson's ratio μ for linear fiber θ Equivalent model of radial Poisson ratio for linear optical fiber μ r ;

[0042] Among them, E θ =E g ×C g +E k ×C k (8)

[0043] in, And C g +C k =1, A g A is the cross-sectional area of ​​the fiber core in a linearly guided optical fiber. kThe area of ​​the coating layer on the cross-section of the linear optical fiber is denoted as A, where A is the cross-sectional area of ​​the linear optical fiber.

[0044]

[0045] Where, C = 0.4 × C g -0.025,

[0046] G = (1-C) × G 1 +C×G 2 (10)

[0047] in, G 2 =C g ×G g +C k ×G k ;

[0048]

[0049] in,

[0050]

[0051] The basic physical properties of the adhesive in step 2.3 include: adhesive cohesive strength σ. max and fracture energy G C The binder has a normal elastic modulus E in the interfacial unit. n The elastic modulus E of the binder in the interfacial unit shear direction 1 and 2 s and E t The maximum tensile stress of the binder in the normal direction of the interface element. The maximum stress of the binder in the shear directions 1 and 2 of the interface element and The relative displacement δ of the binder in the shear directions 1 and 2 of the interface element. s and δ t The adhesive exhibits a relative opening displacement δ in the normal direction of the interface element. n ;

[0052] In step 2.4, the initial stiffness coefficient of the binder in type I, type II, and type III failure and the total relative displacement δ of the interface of the cohesive model of the binder under mixed loading are calculated according to formulas (13) and (14), respectively:

[0053]

[0054]

[0055] Step 3 specifically involves:

[0056] The digital model of the fiber optic coil precision winding established in step 1 is imported into the finite element simulation software. Based on the equivalent physical model of the fiber optic coil conductor established in step 2, material properties are assigned to the digital model of the fiber optic coil precision winding imported into the finite element simulation software. A cylindrical coordinate system along the fiber optic coil axis is established to assign material directions, and a mesh is generated. Finally, a finite element model of the fiber optic coil near-field high-speed release is established.

[0057] The constraints in step 4 include: applying contact constraints and adhesive contact constraints to the fiber optic cables, and applying contact constraints to the fiber optic cable and the core.

[0058] Applying contact constraints to the fiber optic cables specifically involves setting the contact properties between the fiber optic cables to: normal hard contact and tangential penalty contact, and setting the contact friction coefficient of the fiber optic cables.

[0059] Applying adhesive contact constraints to the fiber optic cables specifically involves assigning the initial stiffness coefficients of the adhesive obtained in step 2.4 for type I, II, and III failures, the maximum tensile stress of the adhesive obtained in step 2.3 for failures in the interface element normal, interface element shear 1 direction, and interface element shear 2 direction, and the total relative displacement δ of the adhesive interface in the cohesive model under mixed loading as unique attributes.

[0060] Applying contact constraints to the fiber optic cable and the core tube specifically involves:

[0061] The part of the online guide fiber and the core fiber winding surface in contact is set with surface-to-surface contact constraint. The contact attributes are normal hard contact and non-separation contact, tangential penalty contact, and then the friction contact coefficient is set.

[0062] Step 5 specifically involves:

[0063] Step 5.1: In the finite element model of the near-field high-speed release of the fiber optic bundle after adding constraints, establish a coordinate system with the centroid of the fiber optic bundle core as the origin, the core axis direction as the X direction of the rectangular coordinate system, and the Y and Z directions as the radial directions of the core.

[0064] Step 5.2: Based on the actual situation of the near-field high-speed release of the optical fiber package, apply gravity loads in any direction to the optical fiber guide and the core of the optical fiber package respectively.

[0065] Step 5.3: Since the core is fixed during the near-field high-speed release of the optical fiber bundle, all degrees of freedom of the optical fiber bundle core are constrained by a consolidation constraint.

[0066] Step 5.4: Set the acceleration of the fiber optic release end along the core axis according to the actual situation of near-field high-speed release of the fiber optic package. The magnitude of the acceleration is the same as the actual release acceleration. When the speed reaches the maximum release speed of the fiber optic package, the acceleration is stopped and the maximum release speed of the fiber optic package is maintained. The maximum release speed of the fiber optic package is 150m / s.

[0067] Step 5.5, based on steps 5.1-5.4, performs near-field high-speed release dynamics analysis of the optical fiber coil.

[0068] The beneficial effects of this invention are:

[0069] 1. This invention is applicable to various winding structures of optical fiber coils. Based on the geometric parameters of the optical fiber coil, the physical properties of each material, the release boundary conditions and boundary loads, a precise finite element model of near-field high-speed release of the optical fiber coil can be quickly parameterized and established, providing a necessary foundation for simulating the near-field high-speed release characteristics of the optical fiber coil.

[0070] 2. This invention, based on the finite element method, realizes the near-field high-speed release dynamic characteristics analysis of optical fiber coils. It can analyze the stress state of the wire-guided optical fiber during high-speed release, such as the changes in tensile stress, shear stress, curvature, and release attitude during release. This provides a necessary theoretical basis for the development of optical fiber guidance technology, and also provides a reference for the improvement of guidance fiber technology, reducing the manufacturing cost of optical fiber coils. The analysis method is simple and has good engineering application value. It solves the problem in the existing technology that engineering units have long lacked theoretical research and can only improve product performance and reliability through continuous trial and error based on a large number of process developments and experiments. This not only results in high development costs and low efficiency, but also leads to certain deviations between experimental results and actual results due to the inconsistency between ground experimental conditions and actual launch environments.

[0071] 3. This invention realizes the near-field high-speed release dynamic characteristics analysis of optical fiber coils based on the finite element method. It can truly reflect the anisotropic characteristics that are common in wire-guided optical fibers and analyze the influence of various physical properties and release boundary conditions on the near-field high-speed release of optical fiber coils. For example, it can analyze the influence of different anisotropic parameters, different binder parameters, different friction coefficients, different release speeds, and different optical fiber coil winding structures on the near-field high-speed release mechanical characteristics of optical fiber coils, providing a necessary basis for determining the favorable factors for optimal high-speed release of optical fiber coils. Attached Figure Description

[0072] Figure 1 This is a flowchart of the fiber optic coil near-field release dynamics analysis method based on the finite element method of the present invention;

[0073] Figure 2This is a schematic diagram of establishing a digital model of precise winding of an optical fiber coil in the near-field release dynamics analysis method of the optical fiber coil based on the finite element method of the present invention.

[0074] Figure 3 This is the trajectory diagram of the core tube with a taper of 1° and a release time of 0.024815s in the xz plane in Embodiment 3 of the present invention;

[0075] Figure 4 This is a trajectory diagram of the core tube with a taper of 1° and a release time of 0.024815s in the xy plane in Embodiment 3 of the present invention;

[0076] Figure 5 This is a diagram showing the principal stress distribution along the axial release length of the mandrel in Embodiment 3 of the present invention, where the mandrel taper is 1° and the release time is 0.024815s.

[0077] Figure 6 This is a shear force distribution diagram along the axial release length of the mandrel in Embodiment 3 of the present invention, where the mandrel taper is 1° and the release time is 0.024815s.

[0078] Figure 7 This is a curve showing the curvature distribution of the release length along the mandrel axis in Embodiment 3 of the present invention, where the mandrel taper is 1° and the release time is 0.024815s. Detailed Implementation

[0079] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0080] Example 1

[0081] The method for analyzing the near-field release dynamics of optical fiber coils based on the finite element method is implemented according to the following steps:

[0082] Step 1: Establish a digital model of the fiber optic coil precision winding and a physical model of the core tube, and assemble the fiber optic coil and core tube to obtain an assembly model; specifically:

[0083] Step 1.1: Model the conventional fiber curve and the core solid model; specifically, determine the basic parameters of the fiber coil and fiber geometry, including: the large end diameter D of the fiber coil core. b Fiber optic cable core tube taper α, fiber optic cable core tube height L b Fiber diameter d, fiber winding pitch d s Number of unwound turns (M) at the large end of the fiber optic core tube fb Number of unwound turns (M) at the small end of the fiber optic core tube fs M, the total number of turns in the first layer of the fiber optic cable b The total number of layers N in the fiber optic cable bundle, and the total length L of the optical fibers in the fiber optic cable bundle; the total length L of the optical fibers in the fiber optic cable bundle is calculated according to the following formula:

[0084]

[0085] Among them, M n r is the number of turns in the nth layer of the optical fiber sheath. nm Let r be the winding radius of the m-th turn of the n-th layer in the fiber optic cable. b Let t be the radius of the large end of the fiber optic core, Δ be the superposition increment of the fiber optic core, and t be the radius of the large end of the core. nb d is the number of turns of the nth layer unwound from the first layer on the back side of the fiber optic cable. sy For the vertical increment of the same layer of fiber in the fiber optic cable;

[0086] The number of turns M in the nth layer of the optical fiber sheath n Calculate according to formula (2):

[0087] M n =M b -(n-1)(M fb +M fs (2)

[0088] The fiber optic packet superposition increment Δ is calculated according to formula (3):

[0089] Δ=dcos60° (3)

[0090] The number of turns t of the nth layer unwound from the first layer on the back side of the fiber optic cable. nb Calculate according to formula (4):

[0091] t nb = (n-1)M f s (4)

[0092] Fiber optic cable in the same layer of fiber vertical increment d sy Calculate according to formula (5):

[0093] d sy =d s sinα (5);

[0094] In step 1.1, the core tube solid model is established based on the core tube parameters; in step 1.1, the conventional fiber curve modeling includes curves with and without a slight bottom tube winding and curves with a slight bottom tube winding, each with a corresponding curve equation.

[0095] Step 1.2: Model the first-floor same-layer cross-turn curve; the first-floor same-layer cross-turn curve is a standard multi-segment circular arc curve with a corresponding curve equation.

[0096] Step 1.3: Model the non-first-floor same-layer cross-turn curves; the non-first-floor same-layer cross-turn curves have corresponding curve equations;

[0097] Step 1.4: Establish the model of the cross-layer unwinding curve segment. The cross-layer unwinding curve segment has a corresponding curve equation.

[0098] Step 1.5: Merge the models established in steps 1.1-1.4 into a complete digital model of precision winding of optical fiber coil, and assemble the optical fiber coil and core tube to obtain an assembly model;

[0099] Step 2: Establish an equivalent physical model of the fiber optic cable and obtain the cohesive properties of the fiber optic cable; specifically, follow these steps:

[0100] Step 2.1: Determine the basic physical properties of the optical fiber structure, including: fiber diameter d and fiber core diameter d0. g Fiber core elastic modulus E g Fiber core shear modulus G g Fiber core Poisson ratio u g Elastic modulus E of coating layer k Coating layer shear modulus G k Coating layer Poisson's ratio u k ;

[0101] Step 2.2: Establish an equivalent physical model of the fiber optic coil and wire-guided fiber based on the basic physical property parameters of the fiber structure determined in Step 2.1; the equivalent physical model of the fiber optic coil and wire-guided fiber includes the equivalent model of the axial elastic modulus E of the wire-guided fiber. θ Equivalent model of radial elastic modulus of linear fiber E r Equivalent model of shear modulus G for linear fiber and equivalent model of axial Poisson's ratio μ for linear fiber θ Equivalent model of radial Poisson ratio for linear optical fiber μ r ;

[0102] Among them, E θ =E g ×C g +E k ×C k (8)

[0103] in, And C g +C k =1, A g A is the cross-sectional area of ​​the fiber core in a linearly guided optical fiber. k The area of ​​the coating layer on the cross-section of the linear optical fiber is denoted as A, where A is the cross-sectional area of ​​the linear optical fiber.

[0104]

[0105] Where, C = 0.4 × C g -0.025,

[0106] G = (1-C) × G 1 +C×G 2 (10)

[0107] in, G 2 =C g ×G g +C k ×G k ;

[0108]

[0109] in,

[0110]

[0111] Step 2.3: Based on the special material of the fiber optic cable binder, the effect of the binder in the fiber optic cable is simulated using a bilinear cohesive force model to determine the basic physical properties of the binder, including: the cohesive strength σ of the binder. max and fracture energy G C The binder has a normal elastic modulus E in the interfacial unit. n The elastic modulus E of the binder in the interfacial unit shear direction 1 and 2 s and E t The maximum tensile stress of the binder in the normal direction of the interface element. The maximum stress of the binder in the shear directions 1 and 2 of the interface element and The relative displacement δ of the binder in the shear directions 1 and 2 of the interface element. s and δ t The adhesive exhibits a relative opening displacement δ in the normal direction of the interface element. n ;

[0112] Step 2.4: Calculate the initial stiffness coefficient of the binder in Type I, Type II, and Type III failures and the total relative displacement δ of the cohesive model interface of the binder under mixed loading based on the basic physical property parameters of the binder determined in Step 2.3, respectively, according to formulas (13) and (14):

[0113]

[0114]

[0115] Step 3: Based on the digital model of the precise winding of the optical fiber coil established in Step 1 and the equivalent physical model of the optical fiber coil conductor established in Step 2, establish a finite element model for the near-field high-speed release of the optical fiber coil; specifically:

[0116] The digital model of the fiber optic coil precision winding established in step 1 is imported into the finite element simulation software. Based on the equivalent physical model of the fiber optic coil conductor fiber established in step 2, the digital model of the fiber optic coil precision winding imported into the finite element simulation software is given material properties. A cylindrical coordinate system along the fiber optic coil axis is established to assign material directions, and the mesh is divided. Finally, a finite element model of the fiber optic coil near-field high-speed release is established.

[0117] Step 4: Add constraints to the finite element model of near-field high-speed release of the optical fiber bundle established in Step 3; the constraints include: applying contact constraints and adhesive contact constraints to the conductor fibers, and applying contact constraints to the conductor fibers and the core.

[0118] Applying contact constraints to the fiber optic cables specifically involves setting the contact properties between the fiber optic cables to: normal hard contact and tangential penalty contact, and setting the contact friction coefficient of the fiber optic cables.

[0119] Applying adhesive contact constraints to the fiber optic cables specifically involves assigning the initial stiffness coefficients of the adhesive obtained in step 2.4 for type I, II, and III failures, the maximum tensile stress of the adhesive obtained in step 2.3 for failures in the interface element normal, interface element shear 1 direction, and interface element shear 2 direction, and the total relative displacement δ of the adhesive interface in the cohesive model under mixed loading as unique attributes.

[0120] Applying contact constraints to the fiber optic cable and the core tube specifically involves:

[0121] The part of the online guide fiber and the core fiber winding surface in contact is set with surface-to-surface contact constraint. The contact attributes are normal hard contact and non-separation contact, tangential penalty contact, and then the friction contact coefficient is set.

[0122] Step 5: Analyze the dynamic characteristics of near-field high-speed release of the fiber optic coil using a constrained finite element model. Specifically:

[0123] Step 5.1: In the finite element model of the near-field high-speed release of the fiber optic bundle after adding constraints, establish a coordinate system with the centroid of the fiber optic bundle core as the origin, the core axis direction as the X direction of the rectangular coordinate system, and the Y and Z directions as the radial directions of the core.

[0124] Step 5.2: Based on the actual situation of the near-field high-speed release of the optical fiber package, apply gravity loads in any direction to the optical fiber guide and the core of the optical fiber package respectively.

[0125] Step 5.3: Since the core is fixed during the near-field high-speed release of the optical fiber bundle, all degrees of freedom of the optical fiber bundle core are constrained by a consolidation constraint.

[0126] Step 5.4: Set the acceleration of the fiber optic release end along the core axis according to the actual situation of near-field high-speed release of the fiber optic package. The magnitude of the acceleration is the same as the actual release acceleration. When the speed reaches the maximum release speed of the fiber optic package, the acceleration is stopped and the maximum release speed of the fiber optic package is maintained. The maximum release speed of the fiber optic package is 150m / s.

[0127] Step 5.5, based on steps 5.1-5.4, performs near-field high-speed release dynamics analysis of the optical fiber coil.

[0128] Example 2

[0129] Based on Example 1, the curve equation for the bottom cylinder winding without a slight bend in step 1.1 is specifically as follows:

[0130]

[0131] Where z is the z-plane where the fiber curve is located, r is the winding radius of the fiber curve, r0 is the radius of the winding bottom cylinder, and θ is the range of the arc angle;

[0132] The specific equation for the curve with slight bottom winding is as follows:

[0133]

[0134] Where z is the z-plane where the fiber curve is located, r is the winding radius of the fiber curve, θ is the arc angle range, k is the slope of the generatrix of the cone, and b is the z-coordinate value of the cone vertex of the cone where the arc is located.

[0135] The first-floor, same-layer, cross-turn curve is a standard multi-segment circular arc curve, and its equation is as follows:

[0136]

[0137] Where z is the z-plane where the fiber curve is located, ρ is the radius of any section of the cone perpendicular to the axis of the cone, θ is the range of the arc angle, k is the slope of the generatrix of the cone, and b is the z-coordinate value of the cone vertex of the cone where the arc is located.

[0138] Based on the coordinates of points p1 and p2 across the same level and z' p1 =z' p2 =0, obtain parameters A and ω. B; Δ = dcos60°;

[0139] The equation for the non-first-floor, same-floor, cross-turn curve is as follows:

[0140] The curve of the first layer's inter-turn curve is shifted radially outward by Δ along the conical surface to obtain the curve:

[0141]

[0142] The curve in formula (7) is shifted from the two endpoints to the middle. The two new endpoints after the shift are connected to the initial endpoints respectively. The three curve segments are merged to form the cross-turn curve, which is the cross-turn curve of the non-first layer same layer that is sought.

[0143] The curve equation for the cross-layer unwinding curve segment is as follows:

[0144] The curve equation of the cross-layer unwinding curve segment is obtained according to the method described in Chinese Patent "A Cross-Layer Unwinding Method of a Digital Model of Precision Winding of Optical Fiber Bundle" (Publication No.: CN114170372A, Publication Date: 2022-03-11).

[0145] Step 1.5: Merge the models established in steps 1.1-1.4 into a complete digital model of precision winding of optical fiber coil, and assemble the optical fiber coil and core tube to obtain an assembly model.

[0146] The optical fiber sheath geometry parameters used in this embodiment are shown in Table 1:

[0147] Table 1

[0148]

[0149] This embodiment uses the 3D modeling software Pro / E to create a digital model of the precision winding of the optical fiber coil and a physical model of the core cylinder. Based on the positional relationship between the conductor fiber and the core cylinder in the wound optical fiber coil, the assembly of the conductor fiber and the core cylinder is completed in Pro / E. The segmentation of the optical fiber coil and its segment modeling are as follows: Figure 2 As shown.

[0150] The physical properties of the fiber optic cable in this embodiment are shown in Table 2:

[0151] Table 2

[0152] name Fiber core Coating layer Aluminum core tube Elastic modulus (GPa) 72 72.2 0.87 Poisson's ratio 0.34 0.17 0.38 Shear modulus (GPa) 30.85 0.32 0.98

[0153] Taking an optical fiber with a cross-section where the silica fiber and the coating each occupy half the area as an example, the silica fiber occupies 1 / 4 of the total area, and the coating occupies 3 / 4, i.e., C g =1 / 4, C k =3 / 4, substituting the above parameters into formulas (9)-(12), the equivalent physical property parameters of the fiber in step 2.2 are shown in Table 3:

[0154] Table 3

[0155]

[0156] In this embodiment, the frictional contact coefficient in step 4 is obtained based on experimental measurements.

[0157] Example 3

[0158] Based on Example 2, this example takes an optical fiber coil with a core tube taper of 1° as the research object. It employs a finite element method (FEM) to analyze the near-field high-speed release dynamics of the optical fiber coil. A finite element model is established with an optical fiber diameter of 0.36 mm, a core tube diameter of 80 mm at the large end, a core tube height of 5.76 mm, a first layer of 16 turns, a total of 3 layers, 2.5 turns unwound at the small end, 1.5 turns unwound at the large end, and a total optical fiber length of 9132 mm. Frictional contact constraints, adhesive contact constraints, and load constraints are applied to simulate the near-field high-speed release process of the optical fiber coil. The analysis of the near-field high-speed release dynamics results is as follows: Figures 3 to 7 As shown, Figure 3 and Figure 4 These represent the trajectories of the fiber optic cable release time of 0.024815 s in the xz and xy planes, respectively. Figure 5 The principal stress distribution along the fiber release length is given by the fiber optic cable release time of 0.024815 s. Figure 6 The shear force distribution along the fiber release length during the fiber bundle release time of 0.024815 s is given. Figure 7 The curvature distribution along the fiber release length is 0.024815s, representing the fiber packet release time.

Claims

1. A method for analyzing the near-field release dynamics of optical fiber coils based on the finite element method, characterized in that, The specific steps are as follows: Step 1: Establish a digital model of the fiber optic coil precision winding and a physical model of the core cylinder, and assemble the fiber optic coil and the core cylinder to obtain an assembly model; Step 2, establish the equivalent physical model of the fiber optic cable and obtain the cohesive properties of the fiber optic cable, which is implemented according to the following steps: Step 2.1: Determine the basic physical properties of the optical fiber structure, including: fiber diameter. Fiber core diameter Fiber core elastic modulus Fiber core shear modulus Poisson's ratio of optical fiber core Elastic modulus of coating layer Coating shear modulus Poisson's ratio of the coating layer ; Step 2.2: Establish an equivalent physical model of the fiber envelope and wire-guided fiber based on the basic physical property parameters of the fiber structure determined in Step 2.

1. Step 2.3: Based on the special material of the fiber optic cable binder, the effect of the binder in the fiber optic cable is simulated using a bilinear cohesive force model to determine the basic physical property parameters of the binder. Step 2.4: Calculate the adhesive's properties based on the basic physical properties determined in Step 2.

3. type, Type and The initial stiffness coefficient and the total relative displacement δ of the interface of the cohesive model under mixed loading in the type failure; Step 3: Based on the digital model of the precise winding of the optical fiber coil established in Step 1 and the equivalent physical model of the optical fiber coil conductor established in Step 2, establish a finite element model of the near-field high-speed release of the optical fiber coil. Step 4: Add constraints to the finite element model of near-field high-speed release of the optical fiber coil established in Step 3. The constraints include: applying contact constraints and adhesive contact constraints to the fiber optic cable and applying contact constraints to the fiber optic cable and the core tube; Applying contact constraints to the fiber optic cables specifically involves setting the contact properties between the fiber optic cables to: normal hard contact and tangential penalty contact, and setting the contact friction coefficient of the fiber optic cables. Applying adhesive contact constraints to the fiber optic cables specifically involves: applying the adhesive obtained in step 2.4 to... type, Type and The initial stiffness coefficient in the type failure and the maximum tensile stress of the binder in the interface element normal, interface element shear 1 direction and 2 direction failure obtained in step 2.3, and the total relative displacement value δ of the interface of the cohesive model of the binder under mixed loading are set as unique attribute assignments; Applying contact constraints to the fiber optic cable and the core tube specifically involves: The part of the online guide fiber and the core fiber winding surface in contact is set with surface-to-surface contact constraint, the contact attribute is normal hard contact and contact does not separate, tangential penalty contact, and then the friction contact coefficient is set; Step 5: Analyze the dynamic characteristics of near-field high-speed release of the fiber optic coil using a constrained finite element model. Specifically: Step 5.1: In the finite element model of the near-field high-speed release of the fiber optic bundle after adding constraints, establish a coordinate system with the centroid of the fiber optic bundle core as the origin, the core axis direction as the X direction of the rectangular coordinate system, and the Y and Z directions as the radial directions of the core. Step 5.2: Based on the actual situation of the near-field high-speed release of the optical fiber package, apply gravity loads in any direction to the optical fiber guide and the core of the optical fiber package respectively. Step 5.3: Since the core is fixed during the near-field high-speed release of the optical fiber bundle, all degrees of freedom of the optical fiber bundle core are constrained by a consolidation constraint. Step 5.4: Based on the actual near-field high-speed release of the fiber optic package, set the acceleration along the core axis of the fiber optic release end. The magnitude of this acceleration should be the same as the actual release acceleration. When the speed reaches the maximum release speed of the fiber optic package, stop accelerating and maintain the maximum release speed. The maximum release speed is... ; Step 5.5, based on steps 5.1-5.4, performs near-field high-speed release dynamics analysis of the optical fiber coil.

2. The method for analyzing the near-field release dynamics of optical fiber coils based on the finite element method according to claim 1, characterized in that, Step 1 specifically involves: Step 1.1: Model the conventional fiber curve and construct the core tube solid model; Step 1.2: Model the first-floor same-layer cross-turn curve; Step 1.3: Model the cross-turn curves of non-first-floor same-layer curves; Step 1.4: Establish the model of the cross-layer unwinding curve segment; Step 1.5: Merge the models established in steps 1.1-1.4 into a complete digital model of precision winding of optical fiber coil, and assemble the optical fiber coil and core tube to obtain an assembly model.

3. The method for analyzing the near-field release dynamics of optical fiber coils based on the finite element method according to claim 2, characterized in that, When performing conventional fiber curve modeling and constructing the core cylinder solid model in step 1.1, it is necessary to determine the basic parameters of the fiber coil and fiber geometry, including: the large end diameter of the fiber coil core. Fiber optic cable core tube taper Fiber optic cable core tube height Fiber diameter d, fiber winding pitch Number of unwound turns at the large end of the fiber optic core tube Number of unwound turns at the small end of the fiber optic core tube Total number of turns in the first layer of the fiber optic cable Total number of fiber optic cable layers and the total length of the optical fiber in the optical fiber package. L ; The solid model of the core cylinder is established based on the parameters of the core cylinder; The conventional fiber curve modeling in step 1.1 includes curves with no bottom tube winding and curves with a bottom tube winding, both of which have corresponding curve equations. Step 1.2 states that the first-layer same-layer cross-turn curve is a standard multi-segment circular arc curve with a corresponding curve equation; In step 1.3, there are corresponding curve equations for non-first-layer same-layer cross-turn curves; The cross-layer unwinding curve segment in step 1.4 has a corresponding curve equation.

4. The method for analyzing the near-field release dynamics of optical fiber coils based on the finite element method according to claim 3, characterized in that, The total length of the optical fiber in the optical fiber bundle in step 1.1 L Calculate using the following formula: （1） in, Let n be the number of turns in the nth layer of the optical fiber sheath. Let be the winding radius of the m-th turn of the n-th layer in the optical fiber bundle. The radius of the large end of the fiber optic core tube. This is an increment added to the fiber optic cable. This refers to the number of turns that the nth layer on the back side of the optical fiber coil is unwound from the first layer. For the vertical increment of the same layer of fiber in the fiber optic cable; Number of turns in the nth layer of the fiber optic cable Calculate according to formula (2): （2） Incremental fiber packet superposition Calculate according to formula (3): （3） The number of turns unwound from the first layer to the nth layer on the back side of the fiber optic cable Calculate according to formula (4): （4） Fiber optic cable in the same layer of fiber vertical increment Calculate according to formula (5): （5）。 5. The method for analyzing the near-field release dynamics of optical fiber coils based on the finite element method according to claim 1, characterized in that, The equivalent physical model of the fiber coil in step 2.2 includes the equivalent model of the axial elastic modulus of the fiber coil. Equivalent model of radial elastic modulus of linear fiber Equivalent model of shear modulus of linear optical fiber 1. Equivalent model of axial Poisson ratio of linear fiber Radial Poisson's ratio equivalent model for linear fiber ; in, (8) in, ,and , This represents the core area of ​​the linear optical fiber. The area of ​​the coating layer on the cross-section of the linear optical fiber. The cross-sectional area of ​​the linear optical fiber; （9） in, , , ; （10） in, , ; （11） in, , ; （12）。 6. The method for analyzing the near-field release dynamics of optical fiber coils based on the finite element method according to claim 5, characterized in that, The basic physical properties of the adhesive in step 2.3 include: adhesive cohesive strength. and fracture energy ; Adhesive in the normal elastic modulus of the interfacial unit The elastic modulus of the binder in the interfacial unit shear directions 1 and 2 and The maximum tensile stress of the binder in the normal direction of the interface element. The maximum stress of the binder in the shear directions 1 and 2 of the interface element. and The relative displacement of the binder in the shear directions 1 and 2 of the interface element, respectively. and The binder undergoes relative opening displacement in the normal direction of the interface element. ; In step 2.4, the adhesive is in type, Type and The initial stiffness coefficient and the total relative displacement δ of the interface of the cohesive model under mixed loading in the failure mode are calculated according to formulas (13) and (14), respectively: （13） （14）。 7. The method for analyzing the near-field release dynamics of optical fiber coils based on the finite element method according to claim 6, characterized in that, Step 3 specifically involves: The digital model of the fiber optic coil precision winding established in step 1 is imported into the finite element simulation software. Based on the equivalent physical model of the fiber optic coil conductor established in step 2, material properties are assigned to the digital model of the fiber optic coil precision winding imported into the finite element simulation software. A cylindrical coordinate system along the fiber optic coil axis is established to assign material directions, and a mesh is generated. Finally, a finite element model of the fiber optic coil near-field high-speed release is established.

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