CN116118196A - A continuous fiber 3D printing path design method based on the force flow tube load path - Google Patents

Abstract

The invention relates to a continuous fiber 3D printing path design method based on a force flow pipe load path, which comprises the following steps: constructing a force flow tube load path generation model according to finite element analysis results under the actual working conditions of the parts; dividing a part stress area according to the characteristics and distribution of the load path curve of the force flow pipe; according to the force flow pipe characteristics of each stress area, combining the main stress track line to determine a printing path and materials required for printing; and (3) carrying out manufacturing-oriented path optimization by combining an extrusion printing process according to the initially planned printing path. Compared with the prior art, the invention lays the continuous fiber with excellent axial stretching property in the main pulling area according to the load path of the force flow pipe, compactly fills the stress concentration part with the thermoplastic matrix material, optimizes the matrix material distribution of the light load area and the shearing force area, can effectively improve the integral strength and rigidity of the part, and realizes the light weight of the part on the premise of meeting the application geometric requirement.

Description

A continuous fiber 3D printing path design method based on the force flow tube load path

technical field

The invention relates to the technical field of 3D printing, in particular to a continuous fiber 3D printing path design method based on the force flow tube load path.

Background technique

Traditional 3D printing technology uses thermoplastic or thermosetting resin, gypsum, inorganic powder, etc. as printing materials, and the strength and rigidity of printed molded parts are not high, which cannot meet its use in the industrial field. However, high-performance fiber-reinforced polymer composites are favored in the current research and industrial fields. Among them, continuous fiber composites, as reinforcements, mainly play a role in bearing loads in structural parts of thermoplastic polymer materials. In 3D printing, fiber Paths are very designable.

However, at present, the reinforcing fibers inside the parts designed by 3D printing methods mostly use "unidirectional filling" and "helical filling", or are arranged in a direction parallel to the contour curve based on the structure after topology optimization. This method is difficult to achieve light weight of parts on the premise of meeting the geometric requirements of the application, and it is impossible to realize that the fiber reinforced body can bear the load transmission well in the main load direction, which makes the parts prone to fracture at the place where the load is applied.

Contents of the invention

The purpose of the present invention is to provide a continuous fiber 3D printing path design method based on the force flow tube load path in order to overcome the above-mentioned defects in the prior art, which can realize the integrated design of lightweight structure and enhanced mechanical properties, and improve the overall performance of parts. The strength and rigidity of the parts can be reduced under the premise of meeting the geometric requirements of the application.

The purpose of the present invention can be achieved through the following technical solutions: a continuous fiber 3D printing path design method based on the force flow tube load path, comprising the following steps:

S1. According to the finite element analysis results under the actual working conditions of the parts, build a force flow tube load path generation model;

S2. According to the characteristics and distribution of the force flow tube load path curve, divide the stress area of the part;

S3. According to the characteristics of the force flow tube in each stress area, combined with the main stress trajectory, determine the printing path and printing required materials;

S4. Based on the printing path obtained in step S3, combined with the extrusion printing process, the manufacturing-oriented path optimization is performed.

Further, the step S1 specifically includes the following steps:

S11. Establish the two-dimensional plane geometry corresponding to the part, set the load direction and constraint boundary of the part's force application point, and obtain the stress distribution state through finite element analysis;

S12. Calculate the direction of the force flow tube at each node, and draw a visual graph of the force flow tube.

Further, after the finite element analysis in the step S11, the node coordinates (x, y) and the normal stress σ _x and the shear stress τ _xy corresponding to each point are obtained.

Further, the step S12 specifically calculates the direction of the force flow tube of each node through the following formula:

tan θ=τ _xy /σ _x .

Further, the part stress area divided in the step S2 includes the main tension area, the shear area, the closed loop area, the light load area and the stress concentration area.

Further, the main tensile region is used to bear the tensile force from the load application point on the right side to the fixed constraint boundary on the left side, which basically coincides with the main tensile stress trajectory drawn based on the first principal stress;

The lower part of the shear region is a semi-elliptical region connected to the fixed constraint boundary, and the internal stress has a transition from tensile stress to shear stress and then to compressive stress;

The closed-loop area includes 4 local small ring-shaped areas, which play a role in carrying the transition from tensile stress to compressive stress around the hole;

the upper annular region of said lightly loaded region touches only the free boundary;

In the stress concentration area, the part where the flow tubes are densely packed is consistent with the stress concentration area.

Further, the step S3 specifically includes the following steps:

S31. Combining with the principal stress trajectory line, further divide the printing design area;

S32. Screening the continuous fiber path according to the force flow tube in the main drawing area;

S33, draw the dense filling of the stress concentration area in the main tension area;

S34, draw the auxiliary trajectory line according to the shear force in the main tension area;

S35. Draw the orthogonal principal stress trajectory line in the shear region and extend it to the model contour;

S36 , reducing the light-loaded area to obtain the final part design style.

Further, the step S32 is specifically to screen the force flow tubes from the loading point to the end of the constraint boundary in the main tension area for 3D printing of continuous fiber materials, which are responsible for bearing the main load from the applied load to the constraint boundary, and it is necessary to ensure the aggregation At the same time, the force flow tubes in other main tension areas and the corresponding orthogonal main compressive stress trajectories are printed according to the thermoplastic matrix material.

Further, the step S33 specifically selects the matrix material for dense filling in the area of stress concentration, and the part involving fiber printing needs to be densely filled for the remaining part to enhance the bonding effect between the fiber and the matrix material.

Further, the step S4 specifically replaces the curved short rods with straight long rods for each grid boundary under the single-layer path, which is conducive to further mechanical simulation verification under the premise of ensuring the reduction degree of the fiber path design scheme And print experiment code generation;

In the printing order, the matrix material is printed first in the same layer to provide support and adhesion walls for fiber printing and improve the printing effect.

Compared with the prior art, the present invention has the following advantages:

1. The present invention applies the theoretical system of force flow tubes and continuous fiber composite materials to 3D printed parts. The continuous fibers that play the main tensile role change the design and manufacturing methods of parts, and provide the possibility for parts to be lightweight and improve mechanical properties , the present invention proposes a continuous fiber filling path design method determined by the load path of the force flow tube, which can realize the fiber reinforced body to well bear the load transmission in the main load direction while optimizing the material distribution of the part. According to the division principle of different areas, the continuous fibers with superior axial tensile properties are laid in the main tension area according to the load path of the force flow tube, and the stress concentration is densely filled with thermoplastic matrix materials, and the light load area and the shear force area are optimized at the same time The distribution of the matrix material can ultimately improve the overall strength and stiffness of the part, and realize the lightweight of the part on the premise of meeting the geometric requirements of the application.

2. The present invention controls the density of the starting point of the fiber at the point of stress concentration by adjusting the printing process of the continuous fiber, and the dense filling can strengthen the bonding effect of the continuous fiber force flow tube, and can prevent the accidental fracture of the part at the place where the load is applied.

3. Arranging continuous carbon fibers according to the design method of the present invention can effectively improve the stress distribution of the structure, and print the matrix material intersecting with the continuous fibers in the same layer first, which can enhance the bonding effect of the fiber composite material and the matrix material. According to this The method proposed by the invention arranges carbon fibers in the design path, which can strengthen the structure, not only improve the calculation efficiency of the whole process, but also effectively optimize the space required for the storage medium of the code file.

4. The traditional main load direction adopts the "through-type" force flow tube printed with continuous fibers, and the "eddy current" force flow tube structure with partial load is the shear force bearing or light load area, which is not suitable for the connection reinforcement structure with the surrounding area. Stability, while the present invention uses the orthogonal principal stress trajectory as the auxiliary line, which can effectively improve the printing stability of the local force flow tube and fully optimize the overall mesoscopic structure of the part.

Description of drawings

Fig. 1 is a schematic flow chart of the method of the present invention;

Fig. 2 is a schematic diagram of the application process of the embodiment;

Fig. 3 a is the schematic diagram of working condition load constraint condition in the embodiment;

Fig. 3b is a schematic diagram of the finite element simulation results in the embodiment;

Figure 4a is a schematic diagram of the area division of the force flow tube load path in the embodiment;

Figure 4b is a schematic diagram of the principal stress trajectory in the embodiment;

Fig. 5 is a schematic diagram of the design process of the continuous fiber printing path in the embodiment;

Figure 6a is a schematic diagram of the curved short rod before the optimization of the printing path details in the embodiment;

Fig. 6b is a schematic diagram of a straight long rod after the printing path details are optimized in the embodiment.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example

As shown in Figure 1, a continuous fiber 3D printing path design method based on the force flow tube load path includes the following steps:

S1. According to the finite element analysis results under the actual working conditions of the parts, build a force flow tube load path generation model;

S2. According to the characteristics and distribution of the force flow tube load path curve, divide the stress area of the part;

S3. According to the characteristics of the force flow tube in each stress area, combined with the main stress trajectory, determine the printing path and printing required materials;

S4. Based on the printing path obtained in step S3, combined with the extrusion printing process, the manufacturing-oriented path optimization is performed.

This embodiment applies the above-mentioned technical solution, as shown in Figure 2, mainly including:

(1) Using the node coordinates (x, y) obtained from the finite element analysis under the actual working conditions of the part, and the normal stress σ _x and shear stress τ _xy corresponding to each point, the load path generation model of the force flow tube is constructed. The generation process is as follows :

1) This embodiment takes a square plate with holes as an example, establishes a two-dimensional plane geometry, sets the load direction and constraint boundary of the force point of the part as shown in Figure 3a, and performs finite element analysis to obtain the stress distribution state (as shown in Figure 3b );

并绘制力流管可视化图形；2) According to the formula tanθ= _τxy / _σx, calculate the direction of force flow tube at each node

And draw the visual graphics of force flow tube;

(2) According to the characteristics and distribution of the load path curve of the force flow tube, the stress area of the part is delineated as shown in Figure 4a, which is divided into the main tension area, the shear force area, the closed loop area, the light load area and the stress concentration area. The characteristics of each area as follows:

1) Main tension area: it mainly bears the tension from the load application point on the right side to the fixed constraint boundary on the left side, basically coincides with the main tensile stress trajectory drawn based on the first principal stress;

2) Shear region: the semi-elliptical region where the lower part is connected to the fixed constraint boundary, and the internal stress has a transition from tensile stress to shear stress and then to compressive stress;

3) Closed-loop area: 4 local small ring-shaped areas are similar to the shear force area, and play the role of bearing the transition from tensile stress to compressive stress around the hole;

4) Light load area: the upper annular area only touches the free boundary, and it can be observed from the stress diagram that the stress value in this area is low;

5) Stress concentration area: the dense part of the force flow tube is largely consistent with the stress concentration area, such as the load application point, the periphery of the hole, and the left upper boundary.

(3) According to the characteristics of the force flow tube in each area, compare the main tension/compression stress trajectory in Figure 4b, analyze and set the path design rules and print the required materials, in order to improve the mechanical properties of the parts and the efficient use of materials, the main planning process See Figure 5, the specific process is as follows:

1) In the main tension area, the force flow tube from the loading point to the end of the constraint boundary is screened for 3D printing of continuous fiber materials, which are responsible for bearing the main load from the applied load to the constraint boundary. , other force flow tubes in the main tension area and the corresponding orthogonal main compressive stress trajectory lines are printed according to the thermoplastic matrix material;

2) The area where the stress is concentrated needs to be densely filled with the matrix material. Among them, the part involving fiber printing (such as the area where the load is applied, etc.) needs to be densely filled with the remaining part to enhance the bonding effect between the fiber and the matrix material;

3) The force flow tube in the shear region corresponds to a part of the principal tensile stress trajectory and the principal compressive stress trajectory, respectively, and there is also shear force in the closed-loop region, so the orthogonal principal stress trajectory can be planned;

4) In the light-load area, although the main compressive stress trajectory lines converge here, the stress is relatively small, and there is generally no requirement to reserve the free boundary of the associated part shape. You can choose to remove the printing of this area to reduce unnecessary material waste.

(4) For the printing path obtained from the preliminary planning, the manufacturing-oriented path optimization is carried out in combination with the extrusion printing process. For each grid boundary under the single-layer path, as shown in Figure 6a and Figure 6b, the short curved rods are replaced by straight long rods, which is conducive to further mechanical simulation verification under the premise of ensuring the restoration of the fiber path design scheme And print experiment code generation. And in the printing order, printing the matrix material preferentially in the same layer can provide a supporting adhesion wall for fiber printing and improve the printing effect.

In summary, this technical solution designs the 3D printing path of continuous fiber composite materials based on the load path, which can realize the integrated design of structure lightweight and mechanical performance enhancement, and improve specific strength, specific stiffness, fatigue resistance and other characteristics. Based on the principle of division of different areas, this technical solution lays continuous fibers with superior axial tensile properties in the main tension area according to the load path of the force flow tube, and densely fills the stress concentration with thermoplastic matrix materials, while optimizing the light load area and The distribution of the matrix material in the shear area can effectively improve the overall strength and stiffness of the part, and realize the lightweight of the part on the premise of meeting the geometric requirements of the application.

Claims (10)

1. A continuous fiber 3D printing path design method based on force flow tube load path, is characterized in that, comprises the following steps: S1. According to the finite element analysis results under the actual working conditions of the parts, build a force flow tube load path generation model; S2. According to the characteristics and distribution of the force flow tube load path curve, divide the stress area of the part; S3. According to the characteristics of the force flow tube in each stress area, combined with the main stress trajectory, determine the printing path and printing required materials; S4. Based on the printing path obtained in step S3, combined with the extrusion printing process, the manufacturing-oriented path optimization is performed. 2. A method for designing a continuous fiber 3D printing path based on a force flow tube load path according to claim 1, wherein said step S1 specifically comprises the following steps: S11. Establish the two-dimensional plane geometry corresponding to the part, set the load direction and constraint boundary of the part's force application point, and obtain the stress distribution state through finite element analysis; S12. Calculate the direction of the force flow tube at each node, and draw a visual graph of the force flow tube. 3. A method for designing a continuous fiber 3D printing path based on a flow tube load path according to claim 2, characterized in that, after the finite element analysis in the step S11, the node coordinates (x, y) and Corresponding to the normal stress σ _x and shear stress τ _xy of each point. 4. A method for designing a continuous fiber 3D printing path based on the force flow tube load path according to claim 3, wherein the step S12 specifically calculates the direction of each node force flow tube by the following formula: tan θ=τ _xy /σ _x . 5. A method for designing a continuous fiber 3D printing path based on a force flow tube load path according to claim 1, wherein the part stress area divided by the step S2 includes a main tension area, a shear force area, and a closed loop area , light load area and stress concentration area. 6. A method for designing a continuous fiber 3D printing path based on the force flow tube load path according to claim 5, wherein the main tension region is used to carry the fixed constraints from the load application point on the right side to the left side The tensile force at the boundary basically coincides with the principal tensile stress trajectory drawn based on the first principal stress; The lower part of the shear region is a semi-elliptical region connected to the fixed constraint boundary, and the internal stress has a transition from tensile stress to shear stress and then to compressive stress; The closed-loop area includes 4 local small ring-shaped areas, which play a role in carrying the transition from tensile stress to compressive stress around the hole; the upper annular region of said lightly loaded region touches only the free boundary; In the stress concentration area, the part where the flow tubes are densely packed is consistent with the stress concentration area. 7. A method for designing a continuous fiber 3D printing path based on a force flow tube load path according to claim 6, wherein the step S3 specifically comprises the following steps: S31. Combining with the principal stress trajectory line, further divide the printing design area; S32. Screening the continuous fiber path according to the force flow tube in the main drawing area; S33, draw the dense filling of the stress concentration area in the main tension area; S34, draw the auxiliary trajectory line according to the shear force in the main tension area; S35. Draw the orthogonal principal stress trajectory line in the shear region and extend it to the model contour; S36 , reducing the light-loaded area to obtain the final part design style. 8. A continuous fiber 3D printing path design method based on force flow tube load path according to claim 7, characterized in that, the step S32 specifically screens the path from the loading point to the end of the constraint boundary in the main drawing area The force flow tube is used for 3D printing of continuous fiber materials. It is responsible for bearing the main load from the applied load to the constraint boundary. It is necessary to ensure that the fiber spacing at the gathering place does not overlap with each other. At the same time, the force flow tubes and corresponding orthogonal main pressure The stress trajectory lines are printed according to the thermoplastic matrix material. 9. A continuous fiber 3D printing path design method based on the force flow tube load path according to claim 7, characterized in that, the step S33 specifically selects the matrix material for dense filling in the stress concentration area, wherein, For the part involving fiber printing, the remaining part needs to be densely filled to enhance the bonding effect between the fiber and the matrix material. 10. A continuous fiber 3D printing path design method based on force flow tube load path according to claim 1, characterized in that, the step S4 is specifically for each grid boundary under the single-layer path, the curve Short rods are replaced by straight long rods, which is conducive to further mechanical simulation verification and printing experiment code generation under the premise of ensuring the restoration of the fiber path design scheme; In the printing order, the matrix material is printed first in the same layer to provide support and adhesion walls for fiber printing and improve the printing effect.

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