CN112395699A - Preparation method of medical fixing brace based on topology optimization - Google Patents

Abstract

The invention provides a method for preparing a medical fixing brace based on topology optimization, which comprises the following steps: step one, determining the shape of a brace; setting a continuous non-optimization area, and performing three-dimensional modeling; setting a brace to fix constraint and stress distribution, and analyzing the structure; step four, topology optimization design, namely adjusting the model according to an optimization result; step five, setting a mold opening line according to the previously set continuous non-optimized area; sixthly, performing silica gel joint filling treatment according to the fixing requirement of the brace; and step seven, carrying out production and processing according to the design result of the step six. The invention enables the brace to save more than 20% of materials after optimization under the condition of unchanged protection performance, has better air permeability and lighter weight, adopts the surface shape profile data of the object limb, can obtain the data through various devices, has low requirement on hardware equipment, and can meet the design requirement on data precision.

Description

Preparation method of medical fixing brace based on topology optimization

Technical Field

The invention relates to the field of medical instruments, in particular to a method for preparing a medical fixing brace based on topology optimization.

Background

Orthopedic trauma is often accompanied by skin, bone, joint, tendon, nerve and blood vessel damage. In the orthopedic treatment process, the injured part needs to be braked by the external fixator for a long time to tend to be recovered normally. Currently, plaster, polymer bandages, splints are commonly used as external fixation devices. Gypsum has the characteristics of plasticity and water absorption and solidification, but the cavity volume can not be changed after the gypsum is solidified, so if the fracture part is packed too tightly, limb periosteum syndrome, muscle ischemia and necrosis can be caused, and ischemic muscle contracture and even limb gangrene can be generated. In addition, the gypsum has irritation, and the long-term fixation easily causes dry skin, so that scales or crusts are generated. Although comfortable and portable, the polymer bandage has hard edge, rubs skin and has poor shaping, so the polymer bandage cannot be used for the reduction of severe fracture. The splint has poor air permeability and is usually peculiar in smell, the edge of the splint presses the skin, the pain of a patient is caused, and the probability of fracture of joint fixation is high.

With the rapid development of computer science and technology, structural optimization design has become one of the most important means for obtaining lightweight and high-performance structures. Topology optimization is a design method for determining an optimal structural type, and is widely applied to the field of engineering. The structural performance of the product is improved, the topological optimization takes the load as a design variable, the form result of the product is restrained, the initial configuration is not needed, and an unexpected optimization design result can be obtained according to the change of the applied load variable. The method is a brand new design method in the field of morphological design and structural design.

Through mass search, the method for treating the affected limb in the prior art is found to be a preparation method of the variable-density porous metal orthopedic implant based on the topology optimization technology, which is disclosed as CN107563056A, and comprises the following steps: CT scanning to establish a skeleton geometric model and select a microstructure, and taking the conditions of porosity, microstructure aperture size and microstructure wall thickness as constraint conditions of topological optimization; calculating the attribute of the equivalent entity unit by a homogenization method, and calculating the mechanical property of the implant by the equivalent entity unit by adopting a finite element; obtaining density distribution in an implant region by using a density method topological optimization technology, and taking the conditions of porosity, microstructure aperture size and microstructure wall thickness as constraint conditions of topological optimization; constructing a geometric model of the variable density gradient multi-hollow orthopedic implant on the basis of the position information of the finite element node unit; manufacturing the variable density porous metal orthopedic implant by 3D printing process. The invention has low bone resorption, good mechanical property and long service life, and can reduce the probability of performing corrective surgery after the implant is implanted for a period of time. Or the publication number is CN106991720A, which discloses a personalized acetabulum reconstruction steel plate pre-bending method based on finite element analysis operation, comprising the following steps: (1) carrying out three-dimensional reconstruction on the acetabulum model; (2) materializing the acetabulum model; (3) materializing the acetabulum model; (4) preprocessing finite element software; (5) and (4) analyzing, calculating and simulating prebending, and processing and forming a prebending steel plate model through a process to obtain a finished steel plate. According to the personalized acetabulum reconstruction steel plate pre-bending method based on finite element analysis and operation, under the existing internal fixation implant product system, the steel plate pre-bending is simulated by means of finite element analysis and operation through numerical simulation, the design flow is simplified, and the personalized pre-bending digital steel plate according with the illness state of a patient is provided. Or as disclosed in publication No. CN105930617A, a method for designing and forming a stiffness-controllable bone tumor defect repair implant, comprising the steps of: collecting and preprocessing image data; fusing and registering the reverse images and constructing an accurate curved surface materialized restoration body model; designing a microscopic porous scheme, and optimizing a porous design scheme by parallel finite element analysis; and importing the printing material into a 3D printing system for printing and forming. According to the invention, according to the symmetrical characteristics of the structural morphology of the human body, the personalized porous structure, the mechanical optimization design and the 3D printing forming of the defect area reconstruction prosthesis after the bone tumor resection are realized by combining the digital modeling, the finite element analysis and the medical 3D printing technology, so that not only is the reconstruction effect of the personalized anatomical morphology and the design forming efficiency of the prosthesis improved, but also the time and the material cost are reduced, the mechanical characteristics and the bone integration microenvironment after reconstruction are optimized, and the bone growth repair of the bone defect area is facilitated.

In summary, most of the methods for treating the affected limb in the prior art are to build a suitable brace, and the building method is not perfect, has a complex structure, and is not beneficial to the wearing and adjustment of the brace.

Disclosure of Invention

The invention provides a method for preparing a medical fixing brace based on topology optimization to solve the problems,

in order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a medical fixing brace based on topology optimization comprises the following steps:

step one, determining the shape of a brace;

setting a continuous non-optimization area, and performing three-dimensional modeling;

setting a brace to fix constraint and stress distribution, and analyzing the structure;

step four, topology optimization design, namely adjusting the model according to an optimization result;

step five, setting a mold opening line according to the previously set continuous non-optimized area;

sixthly, performing silica gel joint filling treatment according to the fixing requirement of the brace;

and step seven, carrying out production and processing according to the design result of the step six.

Preferably, the preparation method comprises the following specific steps:

firstly, setting a fixed point according to the supporting condition of an affected part, surrounding a fixed area in a basic geometric form, and further determining the shape of a brace;

setting continuous non-optimized areas, facilitating subsequent mounting and dismounting, and simultaneously performing three-dimensional modeling to obtain a model;

step three, importing the model obtained in the step two into topology optimization software, setting stress distribution and support constraint of the brace by using the topology optimization software, taking the stress condition of the surface of the brace as an optimization constraint condition, and analyzing the structure of the model;

step four, starting to perform topology optimization calculation, selecting a proper optimization result, and using modeling software to reintegrate the optimization forms;

checking an optimization result, and setting a mold opening line according to a previously set continuous non-optimization area;

and step six, performing silica gel filling and mold reversing aiming at the position of the fixed point, and ensuring the stability of the brace after being worn.

And step seven, performing production processing by taking the design result obtained in the step six as a design scheme.

The beneficial technical effects obtained by the invention are as follows:

1. under the condition that the protection performance of the optimized brace is not changed, the material is saved by more than 20%, the air permeability is better, and the weight is lighter.

2. By adopting the surface form contour data of the object limb, the data can be acquired by various devices, the requirement on hardware equipment is low, the data precision can meet the design requirement, and the implementation and popularization in basic medical institutions are facilitated.

3. Thereby set up better constraint condition and obtain better simpler structure, and this structure is conveniently dressed and is adjusted.

Drawings

The invention will be further understood from the following description in conjunction with the accompanying drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the embodiments. Like reference numerals designate corresponding parts throughout the different views.

Fig. 1 is a schematic flow chart of a method for manufacturing a medical fixing brace based on topology optimization according to an embodiment of the present invention;

FIG. 2 is a schematic illustration of bone features of a scan fixation site according to one embodiment of the present invention;

FIG. 3 is a schematic illustration of bone features of a scan fixation site according to one embodiment of the present invention;

FIG. 4 is a schematic diagram of a force applied to a fixing brace according to an embodiment of the invention;

FIG. 5 is a schematic three-dimensional model of a fixing brace according to an embodiment of the invention;

FIG. 6 is a schematic diagram of a force analysis of a three-dimensional model of a fixing brace according to an embodiment of the invention;

FIG. 7 is a diagram illustrating a result of topology optimization when fifteen percent of filler is fixed on a brace according to one embodiment of the present invention;

FIG. 8 is a diagram illustrating a result of topology optimization when twenty-five percent filler is filled in a fixed brace according to an embodiment of the present invention;

FIG. 9 is a diagram illustrating a fixed brace readjustment model according to one embodiment of the present invention;

FIG. 10 is a schematic view of a mold opening line for mold setup after adjustment of a fixed clamp according to one embodiment of the present invention;

FIG. 11 is a schematic view of mold opening after adjustment of the fixing fixture according to one embodiment of the present invention;

FIG. 12 is a schematic diagram of a finite element analysis of a three-dimensional model of a fixed brace according to an embodiment of the present invention;

FIG. 13 is a schematic diagram of a finite element analysis of a fixed brace adjusted model according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to embodiments thereof; it should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Other systems, methods, and/or features of the present embodiments will become apparent to those skilled in the art upon review of the following detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. Additional features of the disclosed embodiments are described in, and will be apparent from, the detailed description that follows.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. based on the orientation or positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but it is not intended to indicate or imply that the device or component referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and are not to be construed as limiting the present patent, and the specific meaning of the terms described above will be understood by those of ordinary skill in the art according to the specific circumstances.

The invention relates to a method for preparing a medical fixing brace based on topological optimization, which explains the following embodiments according to the description of the attached drawings:

the first embodiment is as follows:

a preparation method of a medical fixing brace based on topology optimization comprises the following steps:

step one, determining the shape of a brace;

setting a continuous non-optimization area, and performing three-dimensional modeling;

setting a brace to fix constraint and stress distribution, and analyzing the structure;

step four, topology optimization design, namely adjusting the model according to an optimization result;

step five, setting a mold opening line according to the previously set continuous non-optimized area;

sixthly, performing silica gel joint filling treatment according to the fixing requirement of the brace;

and step seven, carrying out production and processing according to the design result of the step six.

Preferably, the preparation method comprises the following specific steps:

firstly, setting a fixed point according to the supporting condition of an affected part, surrounding a fixed area in a basic geometric form, and further determining the shape of a brace;

setting continuous non-optimized areas, facilitating subsequent mounting and dismounting, and simultaneously performing three-dimensional modeling to obtain a model;

step three, importing the model obtained in the step two into topology optimization software, setting stress distribution and support constraint of the brace by using the topology optimization software, taking the stress condition of the surface of the brace as an optimization constraint condition, and analyzing the structure of the model;

step four, starting to perform topology optimization calculation, selecting a proper optimization result, and using modeling software to reintegrate the optimization forms;

checking an optimization result, and setting a mold opening line according to a previously set continuous non-optimization area;

and step six, performing silica gel filling and mold reversing aiming at the position of the fixed point, and ensuring the stability of the brace after being worn.

And step seven, performing production processing by taking the design result obtained in the step six as a design scheme.

Example two:

a preparation method of a medical fixing brace based on topology optimization comprises the following steps:

step one, determining the shape of a brace;

setting a continuous non-optimization area, and performing three-dimensional modeling;

setting a brace to fix constraint and stress distribution, and analyzing the structure;

step four, topology optimization design, namely adjusting the model according to an optimization result;

step five, setting a mold opening line according to the previously set continuous non-optimized area;

sixthly, performing silica gel joint filling treatment according to the fixing requirement of the brace;

and step seven, carrying out production and processing according to the design result of the step six.

Preferably, the preparation method comprises the following specific steps:

firstly, setting a fixed point according to the supporting condition of an affected part, surrounding a fixed area in a basic geometric form, and further determining the shape of a brace;

setting continuous non-optimized areas, facilitating subsequent mounting and dismounting, and simultaneously performing three-dimensional modeling to obtain a model; the modeling software is software with three-dimensional modeling functions such as evolve, rho, 3Dsmax and the like, and an stp format is derived.

Step three, importing the model obtained in the step two into topology optimization software, setting stress distribution and support constraint of the brace by using the topology optimization software, taking the stress condition of the surface of the brace as an optimization constraint condition, and analyzing the structure of the model; importing the stp format file into topology optimization software, setting stress and support constraint of the brace by using the topology optimization software, taking the stress condition of the surface of the brace as an optimization constraint condition, and analyzing and optimizing the software into optistrct or ansys and the like.

And fourthly, starting topology optimization calculation, selecting a proper optimization result, and using modeling software to reintegrate the optimization forms.

Checking an optimization result, and setting a mold opening line according to a previously set continuous non-optimization area; the modeling software is software with three-dimensional modeling function, such as evolve, rho, 3Dsmax and the like.

And step six, performing silica gel filling and mold reversing aiming at the position of the fixed point, and ensuring the stability of the brace after being worn.

And step seven, performing production processing by taking the design result obtained in the step six as a design scheme. The 3D printing technique may be selected, or other manufacturing techniques may be selected. Under the condition that the protection performance of the optimized brace is not changed, the material is saved by more than 20%, the air permeability is better, and the weight is lighter. Meanwhile, the method can be suitable for various processing modes according to different materials.

Step seven, establishing a model database according to the topology optimization result of the step and quickly selecting corresponding parameters for production design according to the model database, wherein the step seven comprises the following steps: (1) a rapid 3D fixed brace modeling method based on a model database comprises the following steps:

(1-1) defining characteristic line templates of a front view, a rear view, a right view and a top view of the two-dimensional fixed support according to the structural characteristics of the vehicle body; the characteristic lines forming the characteristic line template are cubic Beziers (Beziers) generated by 4 control points, and the number and the numbering sequence of the characteristic lines of the characteristic line template are consistent for different fixed braces and are topologically consistent in shape.

(2) The precise quick matching of the characteristic line model of the actual two-dimensional fixed brace image is given as follows: firstly, extracting an actual two-dimensional fixed brace image by using an image segmentation method, then extracting a characteristic line of the actual two-dimensional fixed brace by using a characteristic extraction operator, and then matching the characteristic line of the actual two-dimensional fixed brace with a characteristic line template of a vehicle type to which the characteristic line belongs by using a shape context method.

(3) And (3) establishing a database by the method (2) for the actual image and the corresponding characteristic line model. The actual image data source comprises pictures or sketches of a two-dimensional vehicle body front view, a rear view, a right view and a top view; the characteristic line model database is a two-dimensional characteristic line model for the exact match of each view of the fixation brace customized for each affected limb. And respectively establishing corresponding three-dimensional curve grid templates according to the category of the fixed brace.

(4) Generating a three-dimensional curve grid by the two-dimensional characteristic line of the right view of the fixed brace: reconstructing a fixed brace 3D curve grid model from a right view of the fixed brace; the reconstruction method is as follows:

(4-1) acquiring a feature line of a right view of the two-dimensional fixed brace through the step (2), and selecting a part of feature line of the right view as a two-dimensional feature line required by reconstructing a 3D curve grid model of the fixed brace by analyzing the corresponding relation of the feature lines among the four views of the front view, the rear view, the right view and the top view;

(4-2) generation of an average 3D deformation model: and respectively establishing a plurality of 3D curve grid models for different fixed braces to generate a 3D grid model library, and carrying out arithmetic averaging on corresponding coordinate values to obtain an average 3D model.

(4-3) generating a three-dimensional characteristic line grid by the characteristic line of the right view of the two-dimensional fixed support: and (4) fixing the coordinates in the x and y directions of the feature line of the right view of the two-dimensional fixed support as rigid constraint by using the average 3D deformation model obtained in the step (4-2), and obtaining the parameters of all the 3D feature lines by using sparse reconstruction based on a statistical method.

(4-4) post-processing of the 3D characteristic line: and (3) iteratively adjusting and optimizing continuity relation between two connected characteristic lines including C0, C1 and the like by analyzing the structure of the fixed brace through an algorithm.

(4-5) rapidly generating a three-dimensional curved surface model of the vehicle body: according to the characteristics of the number of doors, the number of windows on one side and the like, the fixed supports are classified, and 6 templates are established. And constructing a plurality of fixed brace 3D models, and finally defining the curve required by the three-dimensional fixed brace as 106 characteristic lines. Defining a main characteristic line according to a molded surface enclosed into the fixed brace, and dividing the curved surface of the fixed brace into three types according to a generation mode of the curved surface of the fixed brace: a quadrilateral curve mesh surface (TCM), an N-edge surface (NSS) and an edge constraint clipping surface (TS). And combining and defining different characteristic lines according to the structure of the fixed support to form a corresponding curved surface generation method, thereby realizing the purpose of changing the existing curve mesh of the affected limb to the model of the 3D curved surface of the fixed support, and storing the output model of the 3D curved surface of the fixed support into a database. Meanwhile, industrial model data in formats of step, prt, igs and the like are generated correspondingly, and design intention is better represented.

2. Model structure optimization for 3D printing

In this embodiment, the method for topology optimization using variable thickness includes the following specific steps:

(2-1) performing triangular mesh planing on the three-dimensional curved surface model of the fixed brace obtained in the step (1) to obtain a model Fout, inward biasing the Fout to obtain a model Fin with the thickness T being 2.5mm, and then stitching the boundary of Fin and Fout to obtain a closed triangular mesh M.

And (2-2) extracting a middle plane Fm of the M, applying uniform force F on the top of the model, and simultaneously restraining the node freedom degree of the fixed support. And establishing an equal-thickness finite element model with the thickness T being 2.5mm, carrying out finite element solution calculation to obtain the maximum stress value sigma max of the equal-thickness model, and determining the strength constraint condition of the model in variable-thickness topological optimization according to the result, wherein sigma is less than or equal to sigma max.

(2-3) establishing a variable thickness optimization model for the middle plane Fm, and taking the minimum quality of Fm as an optimization target; each unit thickness t of Fm is a design variable, and t belongs to [1,2.5 ]; and (3) performing variable thickness optimization solving calculation on the middle surface Fm by taking the strength sigma less than or equal to the sigma max as a model constraint condition to obtain the optimal unit thickness distribution result of the middle surface Fm meeting the constraint condition, and extracting the thickness value corresponding to each node.

3. The solid modeling facing 3D printing comprises the following specific processes:

(3-1) inputting an equal-thickness closed grid model M;

and (3-2) calculating a normal vector of a unit adjacent to each node of the M inner surface Fin, calculating a unit vector of each node on the M inner surface Fin according to an area weight method, and obtaining the thickness value of each node of Fin by utilizing the node mapping relation between Fm and the inner surface of M, namely Fin.

And (3-3) according to the thickness value and the unit vector corresponding to each node of the inner surface Fin of the model, biasing the inner surface of M, namely Fin, towards the outer surface direction to obtain a printable variable-thickness fixed brace structure model and converting the variable-thickness fixed brace structure model into an STL format for storage.

(4) Creation of support structures

Printing with FDM type 3D printer, the concrete flow of bearing structure generation is as follows:

(4-1) selecting a model printing Direction

In order to maintain the aesthetic appearance of the surface of the mounting brace, the mounting brace is selected to be laterally positioned in the printing direction of the mold, taking into account the poor surface quality of the contact portion of the support structure with the mold.

(4-2) detection of model overhang

The critical angle was set to 45 degrees and all the support points P of the overhanging portion of the model were calculated.

(4-3) generating a support Structure

P is a point set which needs to be supported by a supporting structure; s is an intersection set combined by the supporting structures; the printing model is m; c is a cone set corresponding to the point P, wherein the vertex angle of the cone is 70 degrees.

The specific flow of the tree-shaped support structure is as follows;

a) calculating the intersection H of the cone ci belonging to the point pi belonging to the p, the other cones in the models m and C and the printing bottom plate;

b) in H, selecting a point s closest to the point pi and a cone cj corresponding to the intersection point s, if the intersection point s exceeds the range of m, removing corresponding pi and ci from P and C, and continuing to perform the step a;

c) inserting a point s, the point s becomes a new suspension point in the P, and two support rods (from pi point and pj point corresponding to cj) are intersected at a point s;

d) making a cone at point s, removing point pi and the corresponding ci;

e) and (4) taking a new point P from P, repeating the steps (a-d) until P is an empty set after the K-th cycle, and finishing the whole process.

(5) 3D printing forming

Taking the FDM type 3D printer as an example, the printing process is as follows:

(5-1) parameter setting: the printing precision is 0.2 mm; the printing temperature is 230 ℃; the printing speed is generally less than 100mm/min, and the feeding speed is 100 mm/min;

(5-2) print path generation, converting the STL into a printer-recognized path format x3g format;

(5-3) printing on line;

and (5-4) post-processing the model, and removing the supporting structure to obtain the fixed brace physical model.

Example three:

a preparation method of a medical fixing brace based on topology optimization comprises the following steps:

step one, determining the shape of a brace;

setting a continuous non-optimization area, and performing three-dimensional modeling;

setting a brace to fix constraint and stress distribution, and analyzing the structure;

step four, topology optimization design, namely adjusting the model according to an optimization result;

step five, setting a mold opening line according to the previously set continuous non-optimized area;

sixthly, performing silica gel joint filling treatment according to the fixing requirement of the brace;

and step seven, carrying out production and processing according to the design result of the step six.

Preferably, the preparation method comprises the following specific steps:

firstly, setting a fixed point according to the supporting condition of an affected part, surrounding a fixed area in a basic geometric form, and further determining the shape of a brace;

setting continuous non-optimized areas, facilitating subsequent mounting and dismounting, and simultaneously performing three-dimensional modeling to obtain a model; the modeling software is software with three-dimensional modeling functions such as evolve, rho, 3Dsmax and the like, and an stp format is derived.

And step three, importing the stp format file into finite element analysis software, wherein the analysis software is optistrct, ansys, inspire and the like, simulating the stress state of the product, simulating material properties, carrying out simulation stress analysis, adjusting the wall thickness of the product according to the stress result, and ensuring that the product cannot yield under the simulated stress state.

Importing the model with the determined wall thickness into topology optimization software, setting stress distribution and support constraint of the brace by using the topology optimization software, taking the stress condition of the surface of the brace as an optimization constraint condition, and analyzing the structure of the model; importing the stp format file into topology optimization software, setting stress and support constraint of the brace by using the topology optimization software, taking the stress condition of the surface of the brace as an optimization constraint condition, and analyzing and optimizing the software into optistrct or ansys and the like.

And fourthly, starting topology optimization calculation, selecting a proper optimization result, and using modeling software to reintegrate the optimization forms.

Checking an optimization result, and setting a mold opening line according to a previously set continuous non-optimization area; the modeling software is software with three-dimensional modeling function, such as evolve, rho, 3Dsmax and the like.

And step six, performing silica gel filling and mold reversing aiming at the position of the fixed point, and ensuring the stability of the brace after being worn.

And step seven, importing the adjusted modeling stp format file into finite element analysis software, wherein the analysis software is optistrct, ansys, inspire and the like, simulating the stress state of the product, simulating material properties, carrying out simulation stress analysis, adjusting the wall thickness of the product according to the stress result, ensuring that the product does not yield (repeating the operation in the step three) in the simulated stress state of the product, and carrying out safety verification.

And step eight, performing production processing by taking the design result obtained in the step six as a design scheme. The 3D printing technique may be selected, or other manufacturing techniques may be selected. Under the condition that the protection performance of the optimized brace is not changed, the material is saved by more than 20%, the air permeability is better, and the weight is lighter. Meanwhile, the method can be suitable for various processing modes according to different materials.

Wherein the fourth step specifically comprises the steps of,

step 4.1, taking the initial finite element analysis result obtained in the step three as an initial value, and entering step 4.2;

step 4.2, importing the initial value into topology optimization software, setting constraint parameters, performing optimization design iterative operation based on a sensitive algorithm, and reading an ODB file of a finite element analysis result;

step 4.3, adjusting the density distribution and recalculating the design response to obtain a current iteration operation value;

step 4.4, judging whether the strain energy reduction target and the volume constraint are met under the current iteration operation value, and if so, entering step 4.6; if not, entering step 4.5;

step 4.5, taking the current iteration operation value as an initial value, and returning to the step 4.2;

and 4.6, taking the iterative operation value obtained in the step 4.4 as a design result.

The method comprises the following steps of scanning the surface of the object limb, and obtaining point cloud data or a DICOM image data format through a three-dimensional laser scanner or a computer tomography imaging device.

In the second step, the processing of the scanning data is completed in reverse engineering software and medical image processing software, and the types of the scanning data comprise point cloud data obtained by reverse scanning and DICOM format data supported by medical image equipment.

In the second step of this embodiment, surface modification is also performed, and the surface modification is performed by at least one of smoothing, de-characterization, grid redrawing, nail removal, or hole patching, and the specific implementation is determined by the actual situation.

In the third step, the general finite element analysis software is any one of Abaqus, Ansys or Nastran.

The limiting parameters of the third step comprise material parameters, antagonistic load parameter conditions and boundary conditions.

And the constraint parameters of the third step comprise design variables, objective functions, constraint conditions and geometric limitations. Designing variables as volume and strain energy; the objective function is the minimum strain energy; the constraint condition is volume constraint; the geometric constraint is to freeze off the non-design area. And selecting a corresponding sensitivity algorithm to complete a topological optimization iterative operation process by taking the minimum strain energy of the model under the predefined load as an optimization target, and obtaining a design result.

And in the third step, the volume fraction is used as a constraint condition of the optimization process and is defined according to the load condition and the light weight of the individual limb part and the strength requirement of the brace. The topology optimization software is unparameterized topology optimization software. The non-parametric topology optimization software is an ATOM module of Tosca software, Optistruct software or Abaqus software. The reverse engineering design software is CAD design software.

And fifthly, importing the initial finite element analysis result obtained in the fourth step into topology optimization software to obtain an STL model of a design result, outputting the STL model to reverse engineering or computer aided design software to perform final re-design of the brace and obtain the brace model after optimized design, outputting the model into a general STL (three-dimensional) printing file format, importing the STL model into 3D printing forming equipment to perform printing forming, and obtaining the personalized external fixation brace.

In the sixth step, the support is redesigned to be at least one of the curved surface drawing shell thickening, the light smoothing of the hollow hole structure and the structural characteristics which are convenient to wear and open and close.

The brace material parameter assignment selects the material parameter corresponding to the final 3D printing forming, and the load boundary condition parameter defines the load physiological data of different limb parts according to the previous biomechanics research literature or laboratory equipment measurement data; the meshing is completed by adopting an automatic meshing function provided by finite element software.

The curved surface shell-pulling thickening function of the invention is to ensure the strength of the brace. The smoothing of the hollowed-out structure is to reduce local stress concentration.

The specific implementation steps of another preferred scheme in the embodiment are as follows:

acquiring limb surface contour data and reconstructing three dimensions:

the lower limb data of the affected side of the object is acquired through a Computer Tomography (CT) device, and the scanning data needs to completely cover the limb range which needs to be fixed by the external fixation brace.

Step two, three-dimensional reconstruction:

the obtained tomographic image is imported into three-dimensional reconstruction software in a DICOM data format for image segmentation processing, and as shown in fig. 2, a limb outer contour three-dimensional model of the achilles tendon injury side is established.

Step three, surface treatment and CAD modeling of the external fixation brace model:

and D, performing surface smoothing, hole filling, curved surface trimming, accurate curved surface construction and other operations on the three-dimensional model of the limb outline established in the step two to obtain a support shell-shaped curved surface model, importing the support shell-shaped curved surface model into CAD (computer-aided design) design software to convert the support shell-shaped curved surface model into a CAD model, and outputting the CAD model into an IGS (input-target system) file format.

Step four, carrying out initialization finite element analysis on the external fixation brace model:

and (4) importing the support IGS model obtained in the third step into general finite element analysis software, and sequentially carrying out finite element modeling pretreatment. Firstly, giving the corresponding material attribute of the later 3D printing of the brace model, and defining the thickness of the shell-shaped model. Secondly, referring to a dorsal extension motion mode of the ankle joint of the lower limb, defining the direction and amplitude of a dorsal extension motion load, and fixing 6 degrees of freedom of the proximal end of the restraint brace; and (4) dividing grids for the shell-shaped brace model, and selecting continuous shell units for simulation. And finally submitting the model to a finite element solver for initial analysis, a modeling process and an initial analysis result.

Step five, the external fixation brace topology optimization design:

according to the initial finite element analysis result of the fourth step, the design goal of brace optimization is defined to minimize the strain energy of the brace (namely, maximize the rigidity) under the volume fraction constraint of the self-defined lightweight design and under the condition of preset load parameters, and a topological optimization model of the external fixation brace is established through a variable density algorithm.

The specific parameter setting comprises the following steps: firstly, defining design variables comprising total strain energy of a brace model and the volume of the brace model; secondly, defining an objective function as minimizing the strain energy of the brace; third, the constraint is defined as a 50% volume constraint fraction; and fourthly, selecting the opening position of the far end and the near end of the brace as a non-design area which does not participate in optimization. After the parameter setting is completed, the calculation result is submitted to a topology optimization solver for iterative solution, and the optimization iterative process and the finally obtained brace topology optimization result are shown in fig. 4.

Step six, model output and 3D printing of the personalized support:

outputting the optimization result obtained in the fifth step in an STL file format, and importing the optimization result into reverse engineering software for CAD redesign. And in the CAD resetting process, the brace is subjected to opening and closing plane cutting, shell drawing thickening and connection structure characteristic design, and finally, the shaping design result and the simulation wearing effect of the brace are output.

And outputting the 3D printed STL file format by using the obtained brace design model, generating a printing support for the brace through general preprocessing software, and finally importing the printing support into 3D printing equipment to complete printing and forming of the brace, thereby obtaining a finished product of the external fixation brace.

Step seven, establishing a model database according to the topology optimization result of the step and quickly selecting corresponding parameters for production design according to the model database, wherein the step seven comprises the following steps: (1) a rapid 3D fixed brace modeling method based on a model database comprises the following steps:

(1-1) defining characteristic line templates of a front view, a rear view, a right view and a top view of the two-dimensional fixed support according to the structural characteristics of the vehicle body; the characteristic lines forming the characteristic line template are cubic Beziers (Beziers) generated by 4 control points, and the number and the numbering sequence of the characteristic lines of the characteristic line template are consistent for different fixed braces and are topologically consistent in shape.

(2) The precise quick matching of the characteristic line model of the actual two-dimensional fixed brace image is given as follows: firstly, extracting an actual two-dimensional fixed brace image by using an image segmentation method, then extracting a characteristic line of the actual two-dimensional fixed brace by using a characteristic extraction operator, and then matching the characteristic line of the actual two-dimensional fixed brace with a characteristic line template of a vehicle type to which the characteristic line belongs by using a shape context method.

(3) And (3) establishing a database by the method (2) for the actual image and the corresponding characteristic line model. The actual image data source comprises pictures or sketches of a two-dimensional vehicle body front view, a rear view, a right view and a top view; the characteristic line model database is a two-dimensional characteristic line model for the exact match of each view of the fixation brace customized for each affected limb. And respectively establishing corresponding three-dimensional curve grid templates according to the category of the fixed brace.

(4) Generating a three-dimensional curve grid by the two-dimensional characteristic line of the right view of the fixed brace: reconstructing a fixed brace 3D curve grid model from a right view of the fixed brace; the reconstruction method is as follows:

(4-1) acquiring a feature line of a right view of the two-dimensional fixed brace through the step (2), and selecting a part of feature line of the right view as a two-dimensional feature line required by reconstructing a 3D curve grid model of the fixed brace by analyzing the corresponding relation of the feature lines among the four views of the front view, the rear view, the right view and the top view;

(4-2) generation of an average 3D deformation model: and respectively establishing a plurality of 3D curve grid models for different fixed braces to generate a 3D grid model library, and carrying out arithmetic averaging on corresponding coordinate values to obtain an average 3D model.

(4-3) generating a three-dimensional characteristic line grid by the characteristic line of the right view of the two-dimensional fixed support: and (4) fixing the coordinates in the x and y directions of the feature line of the right view of the two-dimensional fixed support as rigid constraint by using the average 3D deformation model obtained in the step (4-2), and obtaining the parameters of all the 3D feature lines by using sparse reconstruction based on a statistical method.

(4-4) post-processing of the 3D characteristic line: and (3) iteratively adjusting and optimizing continuity relation between two connected characteristic lines including C0, C1 and the like by analyzing the structure of the fixed brace through an algorithm.

(4-5) rapidly generating a three-dimensional curved surface model of the vehicle body: according to the characteristics of the number of doors, the number of windows on one side and the like, the fixed supports are classified, and 6 templates are established. And constructing a plurality of fixed brace 3D models, and finally defining the curve required by the three-dimensional fixed brace as 106 characteristic lines. Defining a main characteristic line according to a molded surface enclosed into the fixed brace, and dividing the curved surface of the fixed brace into three types according to a generation mode of the curved surface of the fixed brace: a quadrilateral curve mesh surface (TCM), an N-edge surface (NSS) and an edge constraint clipping surface (TS). And combining and defining different characteristic lines according to the structure of the fixed support to form a corresponding curved surface generation method, thereby realizing the purpose of changing the existing curve mesh of the affected limb to the model of the 3D curved surface of the fixed support, and storing the output model of the 3D curved surface of the fixed support into a database. Meanwhile, industrial model data in formats of step, prt, igs and the like are generated correspondingly, and design intention is better represented.

2. Model structure optimization for 3D printing

In this embodiment, the method for topology optimization using variable thickness includes the following specific steps:

(2-1) performing triangular mesh planing on the three-dimensional curved surface model of the fixed brace obtained in the step (1) to obtain a model Fout, inward biasing the Fout to obtain a model Fin with the thickness T being 2.5mm, and then stitching the boundary of Fin and Fout to obtain a closed triangular mesh M.

And (2-2) extracting a middle plane Fm of the M, applying uniform force F on the top of the model, and simultaneously restraining the node freedom degree of the fixed support. And establishing an equal-thickness finite element model with the thickness T being 2.5mm, carrying out finite element solution calculation to obtain the maximum stress value sigma max of the equal-thickness model, and determining the strength constraint condition of the model in variable-thickness topological optimization according to the result, wherein sigma is less than or equal to sigma max.

(2-3) establishing a variable thickness optimization model for the middle plane Fm, and taking the minimum quality of Fm as an optimization target; each unit thickness t of Fm is a design variable, and t belongs to [1,2.5 ]; and (3) performing variable thickness optimization solving calculation on the middle surface Fm by taking the strength sigma less than or equal to the sigma max as a model constraint condition to obtain the optimal unit thickness distribution result of the middle surface Fm meeting the constraint condition, and extracting the thickness value corresponding to each node.

3. The solid modeling facing 3D printing comprises the following specific processes:

(3-1) inputting an equal-thickness closed grid model M;

and (3-2) calculating a normal vector of a unit adjacent to each node of the M inner surface Fin, calculating a unit vector of each node on the M inner surface Fin according to an area weight method, and obtaining the thickness value of each node of Fin by utilizing the node mapping relation between Fm and the inner surface of M, namely Fin.

And (3-3) according to the thickness value and the unit vector corresponding to each node of the inner surface Fin of the model, biasing the inner surface of M, namely Fin, towards the outer surface direction to obtain a printable variable-thickness fixed brace structure model and converting the variable-thickness fixed brace structure model into an STL format for storage.

(4) Creation of support structures

Printing with FDM type 3D printer, the concrete flow of bearing structure generation is as follows:

(4-1) selecting a model printing Direction

In order to maintain the aesthetic appearance of the surface of the mounting brace, the mounting brace is selected to be laterally positioned in the printing direction of the mold, taking into account the poor surface quality of the contact portion of the support structure with the mold.

(4-2) detection of model overhang

The critical angle was set to 45 degrees and all the support points P of the overhanging portion of the model were calculated.

(4-3) generating a support Structure

P is a point set which needs to be supported by a supporting structure; s is an intersection set combined by the supporting structures; the printing model is m; c is a cone set corresponding to the point P, wherein the vertex angle of the cone is 70 degrees.

The specific flow of the tree-shaped support structure is as follows;

a) calculating the intersection H of the cone ci belonging to the point pi belonging to the p, the other cones in the models m and C and the printing bottom plate;

b) in H, selecting a point s closest to the point pi and a cone cj corresponding to the intersection point s, if the intersection point s exceeds the range of m, removing corresponding pi and ci from P and C, and continuing to perform the step a;

c) inserting a point s, the point s becomes a new suspension point in the P, and two support rods (from pi point and pj point corresponding to cj) are intersected at a point s;

d) making a cone at point s, removing point pi and the corresponding ci;

e) and (4) taking a new point P from P, repeating the steps (a-d) until P is an empty set after the K-th cycle, and finishing the whole process.

(5) 3D printing forming

Taking the FDM type 3D printer as an example, the printing process is as follows:

(5-1) parameter setting: the printing precision is 0.2 mm; the printing temperature is 230 ℃; the printing speed is generally less than 100mm/min, and the feeding speed is 100 mm/min;

(5-2) print path generation, converting the STL into a printer-recognized path format x3g format;

(5-3) printing on line;

and (5-4) post-processing the model, and removing the supporting structure to obtain the fixed brace physical model.

In conclusion, the invention provides a medical fixed brace preparation method based on topology optimization, the optimized brace saves more than 20% of materials under the condition of unchanged protection performance, has better air permeability and lighter weight, adopts surface shape profile data of a target limb, can be obtained by various devices, has low requirement on hardware devices, can meet the design requirement on data precision, is beneficial to implementation and popularization in basic medical institutions, sets better constraint conditions so as to obtain a better and simpler structure, and is convenient to wear and adjust.

Although the invention has been described above with reference to various embodiments, it should be understood that many changes and modifications may be made without departing from the scope of the invention. That is, the methods, systems, and devices discussed above are examples. Various configurations may omit, substitute, or add various procedures or components as appropriate. For example, in alternative configurations, the methods may be performed in an order different than that described, and/or various components may be added, omitted, and/or combined. Moreover, features described with respect to certain configurations may be combined in various other configurations, as different aspects and elements of the configurations may be combined in a similar manner. Further, elements therein may be updated as technology evolves, i.e., many elements are examples and do not limit the scope of the disclosure or claims.

Specific details are given in the description to provide a thorough understanding of the exemplary configurations including implementations. However, configurations may be practiced without these specific details, e.g., well-known circuits, processes, algorithms, structures, and techniques have been shown without unnecessary detail in order to avoid obscuring the configurations. This description provides example configurations only, and does not limit the scope, applicability, or configuration of the claims. Rather, the foregoing description of the configurations will provide those skilled in the art with an enabling description for implementing the described techniques. Various changes may be made in the function and arrangement of elements without departing from the spirit or scope of the disclosure.

It is intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention. The above examples are to be construed as merely illustrative and not limitative of the remainder of the disclosure. After reading the description of the invention, the skilled person can make various changes or modifications to the invention, and these equivalent changes and modifications also fall into the scope of the invention defined by the claims.

Claims (2)

1. A preparation method of a medical fixing brace based on topology optimization is characterized by comprising the following steps:

step one, determining the shape of a brace;

setting a continuous non-optimization area, and performing three-dimensional modeling;

setting a brace to fix constraint and stress distribution, and analyzing the structure;

step four, topology optimization design, namely adjusting the model according to an optimization result;

step five, setting a mold opening line according to the previously set continuous non-optimized area;

sixthly, performing silica gel joint filling treatment according to the fixing requirement of the brace;

and step seven, carrying out production and processing according to the design result of the step six.

2. The method for preparing a medical fixing brace based on topology optimization according to claim 1, wherein the method comprises the following steps:

firstly, setting a fixed point according to the supporting condition of an affected part, surrounding a fixed area in a basic geometric form, and further determining the shape of a brace;

setting continuous non-optimized areas, facilitating subsequent mounting and dismounting, and simultaneously performing three-dimensional modeling to obtain a model;

step three, importing the model obtained in the step two into topology optimization software, setting stress distribution and support constraint of the brace by using the topology optimization software, taking the stress condition of the surface of the brace as an optimization constraint condition, and analyzing the structure of the model;

step four, starting to perform topology optimization calculation, selecting a proper optimization result, and using modeling software to reintegrate the optimization forms;

checking an optimization result, and setting a mold opening line according to a previously set continuous non-optimization area;

and step six, performing silica gel filling and mold reversing aiming at the position of the fixed point, and ensuring the stability of the brace after being worn.

And step seven, performing production processing by taking the design result obtained in the step six as a design scheme.

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