A Design Method for Additive Manufacturing Lattice Structures

Abstract

The present invention relates to the field of lattice structure design, and discloses a design method for an additive manufacturing lattice structure. The steps of drawing an envelope line and the following steps in the existing design are changed to drawing the Wv / Es-σ / Es diagram of each structure, and bringing the actual application parameters (energy absorption U and peak stress σ p ) into the diagram to directly obtain the structure type and the strut inclination angle. Then, the rod diameter d can be obtained through two simple equations, completing the design of the structure. This fundamentally avoids the repeated drawing of complex envelope diagrams and the use of complex equations when calculating the rod diameter d subsequently, making the entire lattice structure design process more convenient and having the potential for practical application.

Description

Technical Field

[0001] The present invention relates to the field of lattice structure design, and specifically to a design method for additive manufacturing lattice structures. Background Art

[0002] Due to its lightweight, complex load-bearing, and energy absorption characteristics, lattice structures are considered the most promising porous structures. Many studies have shown that by changing the structural parameters, lattice structures can have excellent energy absorption performance. Therefore, it is extremely valuable to propose a systematic method for lattice structure design. The existing lattice structure design technology is mainly forward design. By pre-analyzing the applied force conditions of the structure and using finite element analysis software (ABAQUS software) to add or subtract materials from the initial structure and perform multiple iterations, the final lattice structure that meets the application requirements can be obtained. This design process is time-consuming and laborious, and due to the complex actual force conditions of the structure and the imperfect pre-analysis of the force conditions, it is very likely that the lattice structure obtained by iteration does not meet the actual application requirements. The prior art proposes a lattice structure design method based on an energy absorption diagram. The specific design steps are as Figure 3 shown. It pre-gives the structure energy absorption U, peak stress σ p , the contact area Ac of the lattice structure under force, and the number of structure layers nl. By calculating the ratio of the peak stress to the Young's modulus, two H values are selected and an envelope line is drawn in the Wv / Es - σ / Es diagram according to the formula in Figure 3 to obtain two intersection values, calculate Wv, and then obtain two new H values; substitute them into the formula in Figure 4 to obtain a new envelope line and intersection points, repeat the above process until the two H values converge; finally, calculate the rod diameter d and the unit lattice density according to the formulas in Figure 5 and Figure 6 to complete the lattice structure design. The prior art method has the drawing of the envelope line in the lattice design process, its equation is complex, the calculation is difficult, and its applicability to different structures is different. In step (6) of Figure 3 , since the previously selected H values are without basis, multiple calculation iterations are required to obtain a unique H value, and the envelope line needs to be redrawn each time, and the process is relatively cumbersome. Finally, in order to obtain the rod diameter d and the unit structure density, very complex equations (the formulas in Figure 6 ) are used, which further increases the calculation difficulty and makes this structure design method almost have no practical application prospects. Summary of the Invention

[0003] The object of the present invention is to overcome the deficiencies of the prior art and provide a design method for additive manufacturing lattice structures to solve the deficiencies of the prior art.

[0004] The object of the present invention is achieved through the following technical solution: A design method for an additive manufacturing lattice structure, comprising the following design steps:

[0005] S1. Input parameters are the structure bottom length L, application required energy absorption Wvmax and specified peak stress σ p ;

[0006] S2. Substitute the input parameters into the relationship diagram composed of the empirical shoulder line equations of various structures established in the previous experiments. Assuming that the parameters Wv / Es is 0.00007 and σ / Es is 0.0002, the structural parameters are represented as a point in the diagram. Using the point-to-line distance formula Calculate the distance between the point and the straight line, and determine which structure should be selected based on the distance. At this point, the required structure type and the inclination angle of the pillars have been determined;

[0007] In step S2, the structural type and the inclination angle are known, that is, the structural deformation mechanism is known to be stretch-dominated or bending-dominated, the inclination angle is greater than 45 degrees for stretch-dominated, and the inclination angle is equal to or less than 45 degrees for bending-dominated;

[0008] When the structure is tension-dominated, the formula is used The relative density of the unit structure is calculated, and the relative density of the structure is the ratio of the volume of the support rod to the volume of the cuboid surrounded by the support rod. From this, the total volume of the support rod can be obtained. The structural type is known, that is, the number and length of the support rods are known. According to the cylinder volume calculation formula, the final required support rod diameter d can be obtained, and the structural design is completed;

[0009] When the structure is bending dominated, the formula is used Calculation is performed. Since the structure type is known, that is, the height H of the structure is constant, the platform stress σ m (for σ p ) is known, b is a geometric constant related to the structure. Through previous experiments, the b value of each structure is known, from which the required pillar rod diameter can be directly obtained. The structure type, pillar rod diameter and overall size required for the lattice design have been fully obtained;

[0010] Among them, σ pe is the peak stress of the elastic section of the structural stress-strain curve, σ s is the yield stress of the base material, C is a geometric constant related to the structure. According to previous experiments, the C value corresponding to each structure has been calculated, σ m is the platform stress, b is the geometric constant related to the structure, and H is the height of the unit structure.

[0011] A design method for an additive manufacturing lattice structure includes the following design steps:

[0012] S1. Input parameters are the structure bottom length L, the specified peak stress σp and the total structural energy absorption U;

[0013] S2. Substitute the peak stress σ of the input parameter p into the shoulder line equation of each structure established in the previous experiment to obtain the energy absorption Wvmax corresponding to each structure. Then substitute it into the formula U = Wvmax * H * Ac * n. Since H, the structural height, is known, the total energy absorption value U1 corresponding to the structure can be obtained. Compare U1 with the input parameter U, and select the structure with the smallest |U1 - U| as the adapted structure type;

[0014] In step S2, the structure type and inclination angle are known, that is, the structural deformation mechanism is known to be tension-dominated or bending-dominated. When the inclination angle is greater than 45 degrees, it is tension-dominated, and when the inclination angle is equal to or less than 45 degrees, it is bending-dominated;

[0015] When the structure is tension-dominated, use the formula to calculate the relative density of the unit structure. The structural relative density is the ratio of the volume of the strut to the volume of the cuboid enclosed by the strut. Thus, the total volume of the struts can be obtained, and the structure type is known, that is, the number and length of the struts are known. According to the cylindrical volume calculation formula, the required strut rod diameter d can be finally obtained, and the structural design is completed;

[0016] When the structure is bending-dominated, use the formula for calculation. Since the structure type is known, that is, the height H of the structure is constant, the platform stress σ m (being σ p ) is known, and b is a geometric constant related to the structure. Through previous experiments, the b value of each structure is known. Thus, the required strut rod diameter can be directly obtained, and the structure type, strut rod diameter, and overall dimensions required for the lattice design have all been obtained;

[0017] Among them, U is the total structural energy absorption, Wvmax is the maximum energy absorption of the structure, H is the height of the unit structure, Ac is the structural stress-bearing area, and n is the number of structural layers.

[0018] The beneficial effects of the present invention are:

[0019] The complex equations and cumbersome processes of the existing design methods are improved. The pre-experimental data is integrated and processed as a database. In the subsequent lattice structure design, after inputting relevant limit parameters, by calling the structure shoulder line equations in the database and performing fitness determination, the structure with the highest fitness is selected as the predetermined structure. Subsequently, according to the deformation mechanism (tensile-dominated or bending-dominated) of the predetermined structure, different formulas are selected to calculate the strut rod diameter d. Thus, the entire lattice design process removes complex formulas and cumbersome iteration processes, achieving a considerable degree of simplification, making it have certain engineering application value to a certain extent and providing a design basis for the matching of structural lightweight and structural strength in engineering design. Brief Description of the Drawings

[0020] Figure 1 It is a design method step diagram of a design method for an additive manufacturing lattice structure of the present invention;

[0021] Figure 2 It is a relationship diagram composed of various structure shoulder line equations in a design method for an additive manufacturing lattice structure of the present invention;

[0022] Figure 3 It is a design step diagram of the prior art;

[0023] Figure 4 It is Formula 1 used in the prior art;

[0024] Figure 5 It is Formula 2 used in the prior art;

[0025] Figure 6 It is Formula 3 used in the prior art; Detailed Description of the Preferred Embodiments

[0026] The technical solution of the present invention will be further described in detail below with reference to the drawings, but the protection scope of the present invention is not limited to the following description.

[0027] As Figure 1 shown, a design method for an additive manufacturing lattice structure is divided into two design routes according to different input parameters;

[0028] The first design route includes the following design steps:

[0029] S1. The input parameters are the structure bottom length L, the application requirement energy absorption Wvmax, and the specified peak stress σ p ;

[0030] S2. Substitute the input parameters into the relationship diagram composed of various structure empirical shoulder line equations established in the pre-experiment, as Figure 2As shown in the figure, assuming that the parameters Wv / Es is 0.00007 and σ / Es is 0.0002, the structural parameters are represented by 1 point in the figure, and the distance formula between the point and the straight line is used. Calculate the distance between the point and the line, and determine which structure should be selected based on the distance (the smaller the distance, the more the structure meets the application requirements). At this point, the required structure type and support inclination angle have been determined;

[0031] In step S2, the structural type and the inclination angle are known, that is, the structural deformation mechanism is known to be stretch-dominated or bending-dominated, the inclination angle is greater than 45 degrees for stretch-dominated, and the inclination angle is equal to or less than 45 degrees for bending-dominated;

[0032] When the structure is tension-dominated, the formula is used The relative density of the unit structure is calculated, and the relative density of the structure is the ratio of the volume of the support rod to the volume of the cuboid surrounded by the support rod. From this, the total volume of the support rod can be obtained. The structural type is known, that is, the number and length of the support rods are known. According to the cylinder volume calculation formula, the final required support rod diameter d can be obtained, and the structural design is completed;

[0033] When the structure is bending dominated, the formula is used Calculation is performed. Since the structure type is known, that is, the height H of the structure is constant, the platform stress σ m (for σ p ) is known, b is a geometric constant related to the structure. Through previous experiments, the b value of each structure is known, from which the required pillar rod diameter can be directly obtained. The structure type, pillar rod diameter and overall size required for the lattice design have been fully obtained;

[0034] Among them, σ pe is the peak stress of the elastic section of the structural stress-strain curve, σ s is the yield stress of the base material, C is a geometric constant related to the structure. According to previous experiments, the C value corresponding to each structure has been calculated, σ m is the platform stress, b is the geometric constant related to the structure, and H is the height of the unit structure.

[0035] The second design route includes the following design steps:

[0036] S1. Input parameters are the structure bottom length L, the specified peak stress σ p and the total structural energy absorption U;

[0037] S2, input parameter peak stress σ pSubstitute it into the shoulder line equation of each structure established in the previous experiment to obtain the energy absorption Wvmax corresponding to each structure. Then substitute it into the formula U = Wvmax * H * Ac * n. Since H, the height of the structure, is known, the total energy absorption value U1 corresponding to the structure can be obtained. Compare U1 with the input parameter U, and select the structure with the smallest |U1 - U| as the adapted structure type;

[0038] In step S2, the structure type and inclination angle are known, that is, the structure deformation mechanism is known to be tension-dominated or bending-dominated. When the inclination angle is greater than 45 degrees, it is tension-dominated, and when the inclination angle is equal to or less than 45 degrees, it is bending-dominated;

[0039] When the structure is tension-dominated, use the formula to calculate the relative density of the unit structure. The relative density of the structure is the ratio of the volume of the strut to the volume of the cuboid enclosed by the strut. Thus, the total volume of the strut can be obtained, and the structure type is known, that is, the number and length of the struts are known. According to the cylinder volume calculation formula, the required strut diameter d can be obtained, and the structure design is completed;

[0040] When the structure is bending-dominated, use the formula for calculation. Since the structure type is known, that is, the height H of the structure is constant, the platform stress σ m (which is σ p ) is known, and b is a geometric constant related to the structure. Through previous experiments, the b value of each structure is known. Thus, the required strut diameter can be directly obtained, and the structure type, strut diameter, and overall dimensions required for the lattice design have all been obtained;

[0041] Among them, U is the total energy absorption of the structure, Wvmax is the maximum energy absorption of the structure, H is the height of the unit structure, Ac is the force-bearing area of the structure, and n is the number of layers of the structure.

[0042] In summary, integrate all the data related to the structure obtained from the previous experiment (stress-strain, energy absorption, structure size, etc.) into a database. Through preliminary processing of the input limited parameters and substituting the processed data into the structure shoulder line equation in the database, the fitness of a specific structure to the input parameters can be obtained, and thus the structure type that best matches the application requirements can be selected.

[0043] To further determine the key parameter (strut diameter) in the structure design, different calculation formulas need to be selected according to the selected structure deformation mechanism first. The tension-dominated type is the formula The bending-dominated type is the formula U = Wvmax * H * Ac * n; directly calculate the strut diameter d or the relative density of the structure related to d through the formula, and then calculate the strut diameter d through the strut diameter and volume formula. Finally, complete the entire lattice structure design to obtain a structure that meets the input specified requirements.

[0044] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inner", "front", "center", "both ends", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention; and as is known to those of ordinary skill in the art, the beneficial effects to be achieved by the present invention are only better beneficial effects compared with the current implementation schemes in the prior art under specific circumstances, rather than directly achieving the best use effects in the industry.

[0045] The above are only the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in related fields. And the changes and alterations made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A design method for an additive manufacturing lattice structure, characterized in that It includes the following design steps: S1. The input parameters are the bottom length L of the structure, the required energy absorption Wvmax for application, and the specified peak stress ; S2. Substitute the input parameters into the relationship diagram composed of the empirical shoulder line equations of various structures established in the previous experiments. The structural parameters are expressed as a point, and the point-to-line distance formula is used. , calculate the distance between the point and the straight line, and determine which structure should be selected based on the distance. At this point, the required structure type and the inclination angle of the pillars have been determined; In step S2, the structural type and inclination angle are known, that is, the structural deformation mechanism is known to be tensile-dominated or bending-dominated. When the inclination angle is greater than 45 degrees, it is tensile-dominated, and when the inclination angle is equal to or less than 45 degrees, it is bending-dominated. When the structure is tension-dominated, the formula is used to calculate the relative density of the unit structure. The relative density of the structure is the ratio of the volume of the struts to the volume of the cuboid enclosed by the struts. From this, the total volume of the struts is obtained, and the structure type is known, that is, the number and length of the struts are known. According to the cylindrical volume calculation formula, the required strut diameter d can be finally obtained, and the structure design is completed. When the structure is dominated by bending, the formula is used for calculation. Since the structure type is known, that is, the height H of the structure is constant, the platform stress is known, and b is a geometric constant related to the structure. Through preliminary experiments, the b value of each structure is known. Therefore, the required strut rod diameter can be directly obtained, and the structure type, strut rod diameter, and overall dimensions required for the lattice design have all been obtained; Among them, is the peak stress of the elastic section of the structural stress-strain curve, is the yield stress of the base material, C is a geometric constant related to the structure. According to previous experiments, the C values corresponding to each structure have been calculated, is the platform stress, b is a geometric constant related to the structure, and H is the height of the unit structure.

2. A design method for an additive manufacturing lattice structure, characterized in that, It includes the following design steps: S1. The input parameters are the bottom length L of the structure and the specified peak stress and the total energy absorption U of the structure; S2. Substitute the peak stress of the input parameter into the shoulder line equation of each structure established in the previous experiment to obtain the energy absorption Wvmax corresponding to each structure, and then substitute it into the formula in which H is the known structure height, to obtain the total energy absorption value U1 corresponding to the structure. Compare U1 with the input parameter U, and select the structure with the smallest ∣U1 - U∣ as the adapted structure type; In step S2, the structural type and inclination angle are known, that is, the structural deformation mechanism is known to be tensile-dominated or bending-dominated. When the inclination angle is greater than 45 degrees, it is tensile-dominated, and when the inclination angle is equal to or less than 45 degrees, it is bending-dominated. When the structure is dominated by tension, the formula is used to calculate the relative density of the unit structure. The relative density of the structure is the ratio of the volume of the struts to the volume of the cuboid enclosed by the struts. From this, the total volume of the struts is obtained, and the structure type is known, that is, the number and length of the struts are known. According to the cylindrical volume calculation formula, the required strut diameter d can be obtained finally, and the structure design is completed. When the structure is dominated by bending, the formula is used for calculation. Since the structure type is known, that is, the height H of the structure is constant, and the platform stress is known, and b is a geometric constant related to the structure. Through previous experiments, the b value of each structure is known. Therefore, the required strut rod diameter can be directly obtained, and the structure type, strut rod diameter, and overall dimensions required for the lattice design have all been obtained; Wherein, U is the total energy absorption of the structure, Wvmax is the maximum energy absorption of the structure, H is the height of the unit structure, Ac is the stress-bearing area of the structure, and n is the number of layers of the structure.

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