CN108763709B - Reconstruction ear support topological structure optimization method based on finite element analysis - Google Patents
Reconstruction ear support topological structure optimization method based on finite element analysis Download PDFInfo
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Abstract
A reconstructed ear support topological structure optimization method based on finite element analysis comprises the following steps: s, performing ulceration risk analysis on the pre-carved primary ear support body, and performing optimization adjustment on the primary ear support body according to an ulceration risk analysis result to obtain an optimized ear support body; t, performing burst risk analysis on the ear support optimized body, judging whether the ear support optimized body meets the burst risk requirement, if so, taking the current ear support optimized body as a finished ear support, otherwise, entering the step M; and M, taking the current ear support optimized body as an ear support primary body, and returning to the step S. The method can be used for pre-evaluating the possible burst situation of the ear support in use and carrying out optimization adjustment so as to obtain the finished ear support with small burst probability.
Description
Technical Field
The invention relates to the technical field of 3D plastic digital medicine, in particular to a reconstruction ear support topological structure optimization method based on finite element analysis.
Background
The incidence rate of the small ear deformity is remarkably increased all over the world, the incidence rate in China is recently reported to be 5.18/10000, and compared with the prior art, the incidence rate is greatly increased, more men than women are, most of the men are unilateral, and the incidence rate on the right side is higher than that on the left side. The external auricle is positioned on both sides of the skull, because the external auricle has no specific function, the external auricle is often ignored, but due to the loss of the ears of the patient, besides the wearing of accessories such as glasses, masks and the like, the external auricle is also often jeopardized in appearance, the hearing of the patient can be influenced, the physiological and psychological burden of the patient is increased, and the normal growth and development of the sick children can be influenced particularly.
For the treatment of small ear deformity, the relatively lifelike auricle bracket is usually carved clinically, and then the carved auricle bracket is implanted into the corresponding part.
Because congenital small ear deformity auricle deletion is serious, the residual ear is basically a small skin tag and lacks of an anatomical structure, it is very important to carve a vivid external auricle to help the patient recover confidence. The average size of the normal external auricle of a human body is about 33mmx55mm, the most anterior external auricle is an helix, an external helix and an earlobe, the middle part is an antihelical complex, the bottom layer is an concha cavity complex, and the three-dimensional structure of the high-low and semi-spiral is presented, the local anatomical structures are basically more than 13, including the external helix, the periauricular, the upper and lower crus of antihelical lobe, triangular fossa, concha cavity, cymba concha, tragus and antitragus, and the like, so the external auricle is the most complex three-dimensional structure and the smallest body surface organ of the human body, and the ear reconstruction operation is always a challenge of an orthopedic surgeon, and the difficulty lies in the complexity of the self anatomical structure of the external auricle, the selection of bracket materials and the chirality of postoperative complication treatment.
Although the development for a period of time has greatly developed the fidelity of the structure of the ear support and the selection range of the support material, the complication of the ulceration of the ear support cannot be completely avoided after the operation. The ulceration factors include local overstrain, skin flap blood circulation disorder, local infection, skin flap compression and the like, and the local overstrain is one of the reasons for the ulceration of the ear support. Clinicians have conducted a great deal of research on how to carve a vivid external auricle, but neglect whether the carved structure of the ear support itself has the problems of skin ulceration and support exposure.
Therefore, in view of the deficiencies in the prior art, it is necessary to provide a method for determining the risk of ulceration in advance for an engraved ear support, so as to optimize and adjust the ear support, and avoid the risk of ulceration while achieving fidelity.
Disclosure of Invention
The invention aims to avoid the defects of the prior art and provides a reconstruction ear support topological structure optimization method based on finite element analysis, which can pre-evaluate the situation that the ear support is likely to be broken in use and optimize and adjust the situation so as to obtain a finished ear support with low breaking probability.
The above object of the present invention is achieved by the following technical means.
The provided reconstruction ear support topological structure optimization method based on finite element analysis comprises the following steps:
s, performing ulceration risk analysis on the primary ear support body, judging whether the primary ear support body meets the ulceration risk requirement, and if so, entering the step V; otherwise, entering a step T;
t, optimizing and adjusting the primary body of the ear support according to the analysis result of the ulceration risk to obtain an optimized body of the ear support, and entering the step U;
u, taking the current ear support optimized body as the primary ear support body, returning to the step S,
and V, taking the current primary ear support body as a finished ear support.
Preferably, the step S of analyzing the primary ear support for the risk of ulceration specifically includes:
s1, scanning the primary ear support body to obtain the contour data of the primary ear support body;
s2, importing the entity model of the primary ear support body in the STL format obtained in the step S1 into a geogenic free from and touch X software for surface restoration, and storing the entity model after surface restoration in the STL format;
s3, importing the STL format stored by the entity model after the curved surface is repaired in the step S2 into the Geomagic Wrap software, and selecting the commands as follows in sequence: the method comprises the following steps of (1) accurately curving a surface, automatically curving, constructing a contour line, constructing a surface sheet, constructing a grating, fitting a surface, finally generating a Nurbs curved surface, and exporting and storing the generated Nurbs curved surface in an IGES format;
s4, importing the Nurbs curved surface in the IGES format obtained in the step S3 into HyperMesh14.0 software for establishing a finite element model, and specifically comprising the following steps:
s4.1, opening Hypermesh software, and importing the Nurbs curved surface in the IGES format in the step S3 into the HyperMesh14.0 software;
s4.2, carrying out entity grid division;
s5, importing the three-dimensional finite element ear model containing cartilage and different skin thicknesses obtained in the step S4 into a finite element professional analysis software Abaqus for finite element analysis;
and S6, obtaining stress-strain analysis results of cartilage, skin, cartilage deformation and skin deformation, and judging the rupture risk of the primary body of the ear support according to the finite element stress result.
Preferably, in step S1, the carved primary ear support body is placed on a sterile table, and the sterilized positioning target points are attached to the periphery of the primary ear support body on the sterile table, and a handheld three-dimensional scanner of handscan700 is used to scan the primary ear support body with a precision of 0.03mm and a measurement rate of 480,000 times/second, so as to obtain the profile data of the primary ear support body.
Preferably, step S4.2, the entity grid division is performed, which specifically includes:
a1: carrying out entity mesh division on a Nurbs curved surface which is created after a contour line is constructed in the Geomagic Wrap software; the method comprises the following steps: importing a Nurbs curved surface in an IGES format into Hypermesh software, entering a Geom-2D panel, selecting an automatic gridding subcommand, selecting a surface to be generated, setting the size and the type of a grid, clicking a segmentation command, segmenting, and adjusting a 2D grid with an angle or length-width ratio which is not in conformity with the requirements of the angle and the length-width ratio;
b1: clicking the view grid quality tool, selecting the 2-D command, and checking the 2D grid of step A1;
c1, generating tetrahedral and hexahedral solid grids;
d1: connecting the model suture positions according to an intraoperative collection suture method;
e1: and selecting the stitched entity grids before framing through a face command, clicking to execute a face searching command, offsetting skin thickness by the grid on the surface of the rib to simulate human skin, and clicking a 3D grid generation tool to generate the entity grids with different skin thicknesses.
Preferably, step E1 specifically generates a solid mesh with a skin thickness of 0.5mm, 1mm, 2 mm.
Preferably, step S5 specifically includes:
a2, creating a skin part and a cartilage part, wherein the skin part and the cartilage part are of the types: entity, homogeneous; the materials of the skin part and the cartilage part are respectively selected from skin and costal cartilage;
when the skin and the cartilage are endowed with the attributes respectively, a skin group is created to store the skin grid, then a skin group removing command is selected to remove the previously created skin grid, and after the cartilage is left, different material attributes are endowed to the cartilage and the skin;
b2, selecting an assembly module command, and assembling and determining the skin model and the cartilage model;
c2, selecting step module commands, and then selecting static and single-factor analysis commands;
d2, setting the model tangential behavior to frictionless;
e2, reload boundary conditions;
e21, creating boundary conditions: setting boundary conditions to be simulated according to the fixed positions of the auricular cartilage and the skin of the human body, and enabling six degrees of freedom of the space at the fixed positions to be zero;
e22, giving gravity-9800 mm/s-2；
E23, giving Pressure negative Pressure suction force of 0.02 Mpa;
f2, determining the grid to be divided into entity grids;
g2, entering an analysis working phase.
Preferably, the primary ear support body is an ear support body carved with the ribs of the target object, or a Medpor model or a Nagata model.
Preferably, in the step T, the primary ear support body is optimally adjusted, specifically:
t1, introducing the obtained primary body of the ear support into HyperMesh14.0 software for finite element analysis;
t2, and then optimizing the shape of the primary ear support body in Optistruct software; and obtaining an ideal optimized model.
Preferably, in step T1, the obtained primary ear support is introduced into hypermesh14.0 software for finite element analysis, specifically: after step F2, a static analysis is created by the analysis module, then optimization is started by the OptiStruct software;
step T2, comprising:
t21, performing shape predeformation definition;
t22, creating an optimized response
T23, setting displacement and mass fraction
T24, setting constraint conditions
T25, establishing an objective function
T26, obtaining ideal optimization results.
Preferably, in step T21, the shape pre-deformation definition is performed, specifically:
pre-deformation definition is carried out on the primary body of the ear support and the primary body is used as a design variable for shape optimization;
step T22, creating an optimization response, specifically:
importing the shape designed in the step T21 into a design variable, and setting a lower bound deformation range;
t24, setting constraints, specifically:
set the lower bound to 0.7;
t25, establishing an objective function, specifically:
selecting a target function instruction, setting the flexibility to be minimum, then selecting static analysis, and carrying out Optistruct software calculation;
t26, an optimization solver of OptiStruct software calculates the optimal structural shape of the ear implant to obtain an ideal optimization result.
According to the reconstruction ear support topological structure optimization method based on finite element analysis, disclosed by the invention, the risk of ear support breakage is judged by judging the support exposed stress-strain simulation analysis on the morphological structure of the primary ear support, so that a reference direction is provided for ear support optimization. The method of the invention, in addition to enabling aesthetic improvements, facilitates its morphological structural analysis from the biomechanical direction. The method establishes different skin thicknesses and negative pressure attractions, can be used for pre-judging the ulceration risk of the ear support by different ear supports carved by different doctors, different skin thicknesses and different negative pressure attractions, and performs optimization adjustment to obtain the finished ear support with low ulceration probability.
Drawings
The technical solution of the present invention is further described with reference to the accompanying drawings, but the contents in the drawings are not to be construed as limiting the present invention.
Fig. 1 is a schematic structural view of a pre-engraved primary ear mount body according to embodiment 2 of the present invention.
Fig. 2 is an original image acquired by a scanner.
FIG. 3 is an image after surface remediation by geographic FreeFrom & touch X software.
FIG. 4 is the solid mesh image generated after step C1;
FIG. 5 is an image generated after step D1 is performed;
FIG. 6 is a cross-sectional view of one thickness of skin produced;
FIG. 7 is a schematic illustration of the creation of a boundary condition at step E21;
FIG. 8 is an analysis of cartilage stress and skin stress for different thicknesses of skin;
FIG. 9 is an analysis of cartilage deformation and skin deformation for different thicknesses of skin;
fig. 10 is a schematic view of an ear mount model before and after optimization.
FIG. 11 is an analysis of cartilage deformation and skin deformation for an ear support optimization volume analysis for different thicknesses of skin;
FIG. 12 is a comparison of displacement between skin and an implanted ear support before and after optimization for different thicknesses of skin;
fig. 13 is an original image acquired by a scanner in embodiment 3.
FIG. 14 is an image after surface remediation by geographic FreeFrom & touch X software in example 3.
FIG. 15 is a solid mesh image generated after step C21 in example 3;
FIG. 16 is a graph of the analysis of cartilage stress and skin stress for different thicknesses of skin in example 3;
fig. 17 is an analysis graph of cartilage deformation and skin deformation for different thicknesses of skin in example 3.
Detailed Description
The technical solution of the present invention is further illustrated by the following examples.
Example 1.
A reconstructed ear support topological structure optimization method based on finite element analysis comprises the following steps:
s, performing ulceration risk analysis on the primary ear support body, judging whether the primary ear support body meets the ulceration risk requirement, and if so, entering the step V; otherwise, entering a step T;
t, optimizing and adjusting the primary body of the ear support according to the analysis result of the ulceration risk to obtain an optimized body of the ear support, and entering the step U;
u, taking the current ear support optimized body as the primary ear support body, returning to the step S,
and V, taking the current primary ear support body as a finished ear support.
Wherein, carry out the risk analysis of ulceration to the primary body of ear support in step S, specifically include:
s1, scanning the primary ear support body to obtain the contour data of the primary ear support body;
s2, importing the entity model of the primary ear support body in the STL format obtained in the step S1 into a geogenic free from and touch X software for surface restoration, and storing the entity model after surface restoration in the STL format;
s3, importing the STL format stored by the entity model after the curved surface is repaired in the step S2 into the Geomagic Wrap software, and selecting the commands as follows in sequence: the method comprises the following steps of (1) accurately curving a surface, automatically curving, constructing a contour line, constructing a surface sheet, constructing a grating, fitting a surface, finally generating a Nurbs curved surface, and exporting and storing the generated Nurbs curved surface in an IGES format;
s4, importing the Nurbs curved surface in the IGES format obtained in the step S3 into HyperMesh14.0 software for establishing a finite element model, and specifically comprising the following steps:
s4.1, opening Hypermesh software, and importing the Nurbs curved surface in the IGES format in the step S3 into the HyperMesh14.0 software;
s4.2, carrying out entity grid division;
s5, importing the three-dimensional finite element ear model containing cartilage and different skin thicknesses obtained in the step S4 into a finite element professional analysis software Abaqus for finite element analysis;
and S6, obtaining stress-strain analysis results of cartilage, skin, cartilage deformation and skin deformation, and judging the rupture risk of the primary body of the ear support according to the finite element stress result.
Specifically, in step S1, the carved primary ear support body is placed on a sterile table, and the sterilized positioning target points are attached to the periphery of the primary ear support body on the sterile table, and a hand-held three-dimensional scanner of handscan700 is used to scan the primary ear support body with a precision of 0.03mm and a measurement rate of 480,000 times/second, so as to obtain the profile data of the primary ear support body.
Step S4.2, entity grid division is carried out, and the method specifically comprises the following steps:
a1: carrying out entity mesh division on a Nurbs curved surface which is created after a contour line is constructed in the Geomagic Wrap software; the method comprises the following steps: importing a Nurbs curved surface in an IGES format into Hypermesh software, entering a Geom-2D panel, selecting an automatic gridding subcommand, selecting a surface to be generated, setting the size and the type of a grid, clicking a segmentation command, segmenting, and adjusting a 2D grid with an angle or length-width ratio which is not in conformity with the requirements of the angle and the length-width ratio;
b1: clicking the view grid quality tool, selecting the 2-D command, and checking the 2D grid of step A1;
c1, generating tetrahedral and hexahedral solid grids;
d1: connecting the model suture positions according to an intraoperative collection suture method;
e1: and selecting the stitched entity grids before framing through a face command, clicking to execute a face searching command, offsetting skin thickness by the grid on the surface of the rib to simulate human skin, and clicking a 3D grid generation tool to generate the entity grids with different skin thicknesses.
Step S5 specifically includes:
a2, creating a skin part and a cartilage part, wherein the skin part and the cartilage part are of the types: entity, homogeneous; the materials of the skin part and the cartilage part are respectively selected from skin and costal cartilage;
when the skin and the cartilage are endowed with the attributes respectively, a skin group is created to store the skin grid, then a skin group removing command is selected to remove the previously created skin grid, and after the cartilage is left, different material attributes are endowed to the cartilage and the skin;
b2, selecting an assembly module command, and assembling and determining the skin model and the cartilage model;
c2, selecting step module commands, and then selecting static and single-factor analysis commands;
d2, setting the model tangential behavior to frictionless;
e2, reload boundary conditions;
e21, creating boundary conditions: setting boundary conditions to be simulated according to the fixed positions of the auricular cartilage and the skin of the human body, and enabling six degrees of freedom of the space at the fixed positions to be zero;
e22, giving gravity-9800 mm/s-2；
E23, giving Pressure negative Pressure suction force of 0.02 Mpa;
f2, determining the grid to be divided into entity grids;
g2, entering an analysis working phase.
The primary ear support body can be an ear support body carved with the ribs of the target object, or a Medpor model or a Nagata model.
Wherein, in step T, optimize the adjustment to the ear support is first physically, specifically is:
t1, introducing the obtained primary body of the ear support into HyperMesh14.0 software for finite element analysis;
t2, and then optimizing the shape of the primary ear support body in Optistruct software; and obtaining an ideal optimized model.
The detailed steps are as follows:
step T1, introducing the obtained primary ear support body into HyperMesh14.0 software for finite element analysis, specifically: after step F2, a static analysis is created by the analysis module, then optimization is started by the OptiStruct software;
step T2, comprising:
t21, performing shape predeformation definition;
t22, creating an optimized response
T23, setting displacement and mass fraction
T24, setting constraint conditions
T25, establishing an objective function
T26, obtaining ideal optimization results.
In step T21, the shape pre-deformation definition is specifically:
pre-deformation definition is carried out on the primary body of the ear support and the primary body is used as a design variable for shape optimization;
step T22, creating an optimization response, specifically:
importing the shape designed in the step T21 into a design variable, and setting a lower bound deformation range;
t24, setting constraints, specifically:
set the lower bound to 0.7;
t25, establishing an objective function, specifically:
selecting a target function instruction, setting the flexibility to be minimum, then selecting static analysis, and carrying out Optistruct software calculation;
t26, an optimization solver of OptiStruct software calculates the optimal structural shape of the ear implant to obtain an ideal optimization result.
It should be noted that the primary ear support body of the present invention may be an ear support body carved with the ribs of the target object, or a Medpor model or a Nagata model.
According to the reconstruction ear support topological structure optimization method based on finite element analysis, disclosed by the invention, the risk of ear support collapse is judged by judging the support exposed stress-strain simulation analysis on the morphological structure of the primary ear support, so that a reference direction is provided for ear support optimization, and the optimization is carried out on the basis of the collapse risk. The method of the invention, in addition to enabling aesthetic improvements, facilitates its morphological structural analysis from the biomechanical direction. The method establishes different skin thicknesses and negative pressure attractions, can be used for pre-judging the ulceration risk of the ear support by different ear supports carved by different doctors, different skin thicknesses and different negative pressure attractions, and performs optimization adjustment to obtain the finished ear support with low ulceration probability.
Example 2.
The method of the present invention is further illustrated by the application of a clinical sculpted ear mount model.
The ear support model of the embodiment is designed for congenital male 7-year-old infant, congenital right auricle deformity, wherein the remaining auricle is in a cumulus shape, and the graduation type of the auricle deformity is three degrees. The primary body of the ear support has been specifically carved for its outer ear repair as shown in fig. 1, but the risk of ulceration is unknown. The method of the invention is adopted to optimize and improve the primary body of the ear support.
The specific process is as follows:
and S, carrying out ulceration risk analysis on the primary body of the ear support, and judging whether the primary body of the ear support meets the ulceration risk requirement.
Specifically, the step S of analyzing the ulceration risk of the pre-carved primary ear stent body specifically includes:
s1, placing the carved primary ear support body of the ear support in the figure 1 on a sterile table, pasting a sterilized positioning target point around the primary ear support body, and scanning by using a hand-held three-dimensional scanner of handscan700 at a precision of 0.03mm and a measurement rate of 480,000 times/second to obtain the contour data of the primary ear support body, as shown in figure 2;
s2, importing the STL-format solid model of the primary ear support obtained in the step S1 into a geographic free from & touch X software for curved surface restoration, and storing the solid model after curved surface restoration into the STL format, wherein the solid model after curved surface restoration is shown in FIG. 3;
s3, importing the STL format stored by the entity model after the curved surface is repaired in the step S2 into the Geomagic Wrap software, and sequentially selecting the commands as follows: the method comprises the following steps of (1) accurately curving a surface, automatically curving, constructing a contour line, constructing a surface sheet, constructing a grating, fitting a surface, finally generating a Nurbs curved surface, and exporting and storing the generated Nurbs curved surface in an IGES format;
s4, importing the Nurbs curved surface in the IGES format obtained in the step S3 into HyperMesh14.0 software for establishing a finite element model, and specifically comprising the following steps:
s4.1, opening Hypermesh software, and importing the Nurbs curved surface in the IGES format in the step S3 into the Hypermesh14.0 software;
s4.2, carrying out entity grid division; the method specifically comprises the following steps:
a1: constructing a contour line in the Geomagic Wrap software and then creating a Nurbs curved surface to divide a surface mesh; the method comprises the following steps: entering a Geom-2D panel, selecting an automesh sub-command, selecting surfs to be generated, setting element size and mesh type, clicking mesh, and adjusting non-conforming 2D grids;
b1: clicking TOOL-check elements to select a 2-D command, and checking the 2D grid drawn in the step A;
c1, clicking 3D-elemeffset and solid map to generate tetrahedral and hexahedral solid grids, as shown in FIG. 4;
d1: connecting the model suture positions by using RIGID according to an intraoperative collection suture method; the method comprises the following steps: clicking 1D-edges, independent-node, dependent-nodes, elem-types to select KINCOUP, selecting nodes according to an intraoperative stitching mode, and finally creating, as shown in FIG. 5;
e1: selecting the entity grids with good edges through a TOOL-faces command, clicking to execute a find faces command, offsetting the skin thickness from the grid on the surface of the rib to simulate the human skin, and clicking 3D-elemeoffset to generate entity grids with different skin thicknesses, wherein as shown in FIG. 6, the entity grids with the skin thicknesses of 0.5mm, 1mm and 2mm can be generated specifically;
s5, importing the three-dimensional finite element ear model containing cartilage and different skin thicknesses obtained in the step S4 into a finite element professional analysis software Abaqus for finite element analysis; the method specifically comprises the following steps:
a2, creating two sections as skin and cartilage respectively, and type as follows: soild, Homogeneous; material selects skin and costal cartilage respectively; when the skin and costal cartilage attributes are respectively given, firstly creating Display groups to store the skin grids, then selecting Remove select to Remove the previously created skin grids, and after cartilage is left, giving different material attributes to the cartilage and the skin;
in this example, the material property settings are shown in table one below.
| Costal cartilage | Skin(s) | |
| Density (g/cm)3) | 1.5 | 1.0 |
| Modulus of elasticity (Mpa) | 14.1 | 0.86 |
| Poisson ratio | 0.4 | 0.4 |
| Ultimate tensile strength | 6.2 | 5.17 |
B2, selecting a Module Module-assembly to enter create-instance, and clicking part-ok;
c2, selecting Module-STEP, and then selecting statics and single factor analysis;
d2, selecting Module-interaction, selecting Create interaction property, creating Contact, setting native viewer as frictionless, and normal viewer as Hard Contact and property;
e2, selecting Module-Load;
e21, creating boundary conditions: setting boundary conditions according to the simulation of the human auricular cartilage and skin fixing position, and enabling U1＝U2＝U3＝UR1＝UR2＝UR3(ii) a As shown in fig. 7;
e22, giving gravity-9800 mm/s-2；
E23, giving Pressure negative Pressure suction force of 0.02 Mpa;
f2, selecting a Module-Mesh, and determining C3D8R: An 8-node linear crack, reduced integration, ourglass control;
g2, selecting a Module Module-Job to enter an analysis stage to obtain the stress-strain analysis results of cartilage, skin, cartilage deformation and skin deformation, wherein the results are shown in fig. 8 and 9; as can be seen from the figure, the stress concentration sites are all skin and cartilage suture sites. According to the strain result graph, the positions where the model deformation occurs are all at the positions of the auricle fracture. The phenomenon is analyzed, the upper edge of the auricle external helix has weak supporting force due to the structure, the displacement between the skin and the cartilage at the position is the largest, and the reverse displacement causes local fatigue strain to cause skin ulceration.
According to the primary ear support collapse risk analysis result, the primary ear support is in collapse risk, so that the primary ear support needs to be optimized, and the step T is carried out.
In the step T, the primary body of the ear support is optimized and adjusted, and the method specifically comprises the following steps:
t1, the obtained primary body of the ear stent is introduced into HyperMesh14.0 software for finite element analysis. The method comprises the following steps: after step F2, a static analysis is created by the analysis module, and then optimization is started by the OptiStruct software.
T2, and then optimizing the shape of the primary ear support body in Optistruct software; and obtaining an ideal optimized model.
Step T2, comprising:
step T21, performing shape pre-deformation definition, specifically:
pre-deformation definition is carried out on the primary body of the ear support and the primary body is used as a design variable for shape optimization; the simulation only changes the deformation range of the base, and the external helix and the internal helix are not changed.
Step T22, creating an optimization response, specifically:
the shape designed in step T21 is imported into the design variables, and the lower bound deformation range is set, in this example, the lower bound deformation parameter is set to 1.2.
T23, setting displacement and mass fraction:
the selection module Optimization-responses creates displacement (dis), mass fraction (mass).
T24, setting constraints, specifically: the lower bound is set to 0.7.
T25, establishing an objective function, specifically:
and selecting an objective function instruction, setting the flexibility to be minimum, then selecting static analysis, and carrying out Optistruct software calculation.
T26, the optimization solver of the OptiStruct software, calculates the optimal structural shape of the ear implant, resulting in the ideal optimization result, as shown in fig. 10.
And then, taking the current optimized body of the ear support as a primary body of the ear support, and analyzing the bursting risk according to the step S. Results for cartilage deformation and skin deformation were obtained at different skin thicknesses (2mm, 1mm and 0.5mm), as shown in fig. 11. And comparing the displacement result between the skin and the implanted ear support, as shown in fig. 12, it can be seen from fig. 12 that the displacement between the optimized ear support and the skin is far lower than the result before the optimization, which indicates that the risk of ulceration of the optimized ear support is lower. The optimized ear support can be used as a final ear support model.
According to the reconstruction ear support topological structure optimization method based on finite element analysis, disclosed by the invention, the risk of ear support breakage is judged by judging the support exposed stress-strain simulation analysis on the morphological structure of the primary ear support, so that the optimization of the ear support is optimized by providing a reference direction. The method of the invention, in addition to enabling aesthetic improvements, facilitates its morphological structural analysis from the biomechanical direction. The method establishes different skin thicknesses and negative pressure attractions, can be used for pre-judging the ulceration risk of the ear support by different ear supports carved by different doctors, different skin thicknesses and different negative pressure attractions, and performs optimization adjustment to obtain the finished ear support with low ulceration probability.
Example 3.
The ear support model of the present example is the one in example 2, which is directed to a 7-year-old congenital male infant, which has congenital right-small ear deformity, the remaining ear is in the shape of a cumulus, and the graduation type of the ear deformity is three degrees. The Medpor model is selected for its outer ear repair pertinence. The Medpor model was purchased from the Strker right ear implant, model 8328 and model 8330, from Provisions of Youqin Biotechnology Ltd; the internal structure of the ear implant is confirmed to be basically solid by adopting 64 rows of 128-layer CT scanning, and the external structure is scanned by adopting a Rexcan DS3 blue-light full-automatic three-dimensional scanner to obtain original data. The method provided by the invention is used for analyzing the bursting risk of the primary body of the ear support, and whether optimization and improvement are needed or not is distinguished.
The specific process is as follows:
s, performing ulceration risk analysis on the primary ear support body, and performing optimization adjustment on the primary ear support body according to the ulceration risk analysis result to obtain an optimized ear support body;
specifically, the step S of analyzing the ulceration risk of the pre-carved primary ear stent body specifically includes:
s1, placing the primary body of the Medpor ear support on a sterile table, pasting a sterilized positioning target point around the primary body, scanning by using a hand-held three-dimensional scanner of handscan700 at a precision of 0.03mm and a measurement rate of 480,000 times/second, and acquiring contour data of the primary body of the ear support, as shown in FIG. 13;
s2, importing the entity model of the primary ear support body in STL format obtained in the step S1 into a geographic free from & touch X software for curved surface restoration, and storing the entity model after curved surface restoration in STL format, wherein the entity model after curved surface restoration is shown in FIG. 14;
s3, importing the STL format stored by the entity model after the curved surface is repaired in the step S2 into the Geomagic Wrap software, and selecting a command as follows: the method comprises the steps of accurately curving a surface, automatically curving, constructing a contour line, constructing a surface sheet, constructing a grating, fitting a surface, generating a Nurbs surface, and exporting and storing the Nurbs surface into an IGES format;
s4, importing the IGES format of the step S3 into HyperMesh14.0 software for establishing a finite element model, and specifically comprising the following steps:
s4.1, opening Hypermesh software, and importing the IGES format of the step S3 into the Hypermesh14.0 software;
s4.2, carrying out entity grid division; the method specifically comprises the following steps:
a1: constructing a contour line in the Geomagic Wrap software and then creating a Nurbs curved surface to divide a surface mesh; the method comprises the following steps: entering a Geom-2D panel, selecting an automesh sub-command, selecting surfs to be generated, setting element size and mesh type, clicking mesh, and adjusting non-conforming 2D grids;
b1: clicking TOOL-check elements to select a 2-D command, and checking the 2D grid drawn in the step A;
c1, clicking 3D-elemeffset and solid map to generate tetrahedral and hexahedral solid grids, as shown in FIG. 15;
d1: connecting the model suture positions by using RIGID according to an intraoperative collection suture method; the method comprises the following steps: clicking 1D-edges, independent-node, dependent-nodes and elem-types to select KINCOUP, selecting nodes according to an intraoperative stitching mode, and finally creating;
e1: selecting the entity grids with good edges through a TOOL-faces command, clicking to execute a find faces command, offsetting the skin thickness by the grid on the surface of the rib to simulate the human skin, clicking 3D-elemeoffset to generate the entity grids with different skin thicknesses, and specifically generating the entity grids with the skin thicknesses of 0.5mm, 1mm and 2 mm;
s5, importing the three-dimensional finite element ear model containing cartilage and different skin thicknesses obtained in the step S4 into a finite element professional analysis software Abaqus for finite element analysis; the method specifically comprises the following steps:
a2, creating two sections as skin and cartilage respectively, and type as follows: soild, Homogeneous; material selects skin and costal cartilage respectively; when the skin and costal cartilage attributes are respectively given, firstly creating Display groups to store the skin grids, then selecting Remove select to Remove the previously created skin grids, and after cartilage is left, giving different material attributes to the cartilage and the skin;
in this example, the material property settings are shown in table two below.
Watch two
| Medpor | Skin(s) | |
| Density (g/cm)3) | 0.565 | 1.0 |
| Modulus of elasticity (Mpa) | 72.0 | 0.87 |
| Poisson ratio | 0.4 | 0.4 |
| Ultimate tensile strength | 4.4 | 5.18 |
B2, selecting a Module Module-assembly to enter create-instance, and clicking part-ok;
c2, selecting Module-STEP, and then selecting statics and single factor analysis;
d2, selecting Module-interaction, selecting Create interaction property, creating Contact, setting native viewer as frictionless, and normal viewer as Hard Contact and property;
e2, selecting Module-Load;
e21, creating boundary conditions: setting boundary conditions according to the simulation of the human auricular cartilage and skin fixing position, and enabling U1＝U2＝U3＝UR1＝UR2＝UR3；
E22, giving gravity-9800 mm/s-2；
E23, giving Pressure negative Pressure suction force of 0.02 Mpa;
f2, selecting a Module-Mesh, and determining C3D8R: An 8-node linear crack, reduced integration, ourglass control;
g2, selecting a Module Module-Job to enter an analysis stage, and obtaining the stress-strain analysis results of cartilage, skin, cartilage deformation and skin deformation, wherein the results are shown in figures 16 and 17; as can be seen from the figure, the stress concentration sites are all skin and cartilage suture sites. According to the strain result graph, the positions where the model deformation occurs are all at the positions of the auricle fracture. The phenomenon is analyzed, the upper edge of the auricle external helix has weaker supporting force due to the structure, the displacement between the skin and the cartilage at the position is the largest, and the reverse displacement causes local fatigue strain to cause skin ulceration;
s6, judging the bursting risk of the primary body of the ear support according to the finite element stress result; and optimizing and adjusting the primary body of the ear support according to the bursting risk analysis result, and correspondingly adjusting the position which is easy to burst to obtain the optimized body of the ear support.
According to the reconstruction ear support topological structure optimization method based on finite element analysis, disclosed by the invention, the risk of ear support breakage is judged by judging the support exposed stress-strain simulation analysis on the morphological structure of the primary ear support, so that a reference direction is provided for ear support optimization. The method of the invention, in addition to enabling aesthetic improvements, facilitates its morphological structural analysis from the biomechanical direction. The method establishes different skin thicknesses and negative pressure attractions, can be used for pre-judging the ulceration risk of the ear support by different ear supports carved by different doctors, different skin thicknesses and different negative pressure attractions, and performs optimization adjustment to obtain the finished ear support with low ulceration probability.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (5)
1. A reconstruction ear support topological structure optimization method based on finite element analysis is characterized by comprising the following steps:
s, performing ulceration risk analysis on the primary ear support body, judging whether the primary ear support body meets the ulceration risk requirement, and if so, entering the step V; otherwise, entering a step T;
and step S, performing ulceration risk analysis on the primary ear support body, and specifically comprising the following steps:
s1, scanning the primary ear support body to obtain the contour data of the primary ear support body;
s2, importing the entity model of the primary ear support body in the STL format obtained in the step S1 into a geogenic free from and touch X software for surface restoration, and storing the entity model after surface restoration in the STL format;
s3, importing the STL format stored by the entity model after the curved surface is repaired in the step S2 into the Geomagic Wrap software, and selecting the commands as follows in sequence: the method comprises the following steps of (1) accurately curving a surface, automatically curving, constructing a contour line, constructing a surface sheet, constructing a grating, fitting a surface, finally generating a Nurbs curved surface, and exporting and storing the generated Nurbs curved surface in an IGES format;
s4, importing the Nurbs curved surface in the IGES format obtained in the step S3 into HyperMesh14.0 software for establishing a finite element model, and specifically comprising the following steps:
s4.1, opening Hypermesh software, and importing the Nurbs curved surface in the IGES format in the step S3 into the HyperMesh14.0 software;
s4.2, carrying out entity grid division;
s5, importing the three-dimensional finite element ear model containing cartilage and different skin thicknesses obtained in the step S4 into a finite element professional analysis software Abaqus for finite element analysis;
step S5 specifically includes:
a2, creating a skin part and a cartilage part, wherein the skin part and the cartilage part are of the types: entity, homogeneous; the materials of the skin part and the cartilage part are respectively selected from skin and costal cartilage;
when the skin and the cartilage are endowed with the attributes respectively, a skin group is created to store the skin grid, then a skin group removing command is selected to remove the previously created skin grid, and after the cartilage is left, different material attributes are endowed to the cartilage and the skin;
b2, selecting an assembly module command, and assembling and determining the skin model and the cartilage model;
c2, selecting step module commands, and then selecting static and single-factor analysis commands;
d2, setting the model tangential behavior to frictionless;
e2, reload boundary conditions;
e21, creating boundary conditions: setting boundary conditions to be simulated according to the fixed positions of the auricular cartilage and the skin of the human body, and enabling six degrees of freedom of the space at the fixed positions to be zero;
e22, giving gravity-9800 mm/s-2；
E23, giving Pressure negative Pressure suction force of 0.02 Mpa;
f2, determining the grid to be divided into entity grids;
g2, entering an analysis working phase;
s6, obtaining stress-strain analysis results of cartilage, skin, cartilage deformation and skin deformation, and judging the rupture risk of the primary body of the ear support according to the finite element stress result;
t, optimizing and adjusting the primary body of the ear support according to the analysis result of the ulceration risk to obtain an optimized body of the ear support, and entering the step U;
in the step T, the primary body of the ear support is optimized and adjusted, and the method specifically comprises the following steps:
t1, introducing the obtained primary body of the ear support into HyperMesh14.0 software for finite element analysis, specifically: after step F2, a static analysis is created by the analysis module, then optimization is started by the OptiStruct software;
t2, and then optimizing the shape of the primary ear support body in Optistruct software; obtaining the model after the ideal optimization of the model,
step T2, comprising:
t21, performing shape pre-deformation definition, specifically:
pre-deformation definition is carried out on the primary body of the ear support and the primary body is used as a design variable for shape optimization;
t22, creating an optimized response, specifically:
importing the shape designed in the step T21 into a design variable, and setting a lower bound deformation range;
t23, setting displacement and mass fraction;
t24, setting constraints, specifically:
set the lower bound to 0.7;
t25, establishing an objective function, specifically:
selecting a target function instruction, setting the flexibility to be minimum, then selecting static analysis, and carrying out Optistruct software calculation;
t26, calculating the optimal structural shape of the ear implant by an optimization solver of OptiStruct software to obtain an ideal optimization result;
u, taking the current ear support optimized body as the primary ear support body, returning to the step S,
and V, taking the current primary ear support body as a finished ear support.
2. The method for optimizing a topological structure of a reconstructed ear support based on finite element analysis according to claim 1,
step S1 is specifically to place the carved primary ear support body on a sterile table, attach a sterilized positioning target point on the sterile table around the primary ear support body, and scan with a hand-held handscan700 three-dimensional scanner at a measurement rate of 480,000 times/second and a precision of 0.03mm to obtain profile data of the primary ear support body.
3. The method of claim 1 for optimizing a topological structure of a reconstructed ear support based on finite element analysis, wherein the method comprises the following steps: step S4.2, entity grid division is carried out, and the method specifically comprises the following steps:
a1: carrying out entity mesh division on a Nurbs curved surface which is created after a contour line is constructed in the Geomagic Wrap software; the method comprises the following steps: importing a Nurbs curved surface in an IGES format into Hypermesh software, entering a Geom-2D panel, selecting an automatic gridding subcommand, selecting a surface to be generated, setting the size and the type of a grid, clicking a segmentation command, segmenting, and adjusting a 2D grid with an angle or length-width ratio which does not meet the requirement so that the 2D grid meets the requirements of the angle and the length-width ratio;
b1: clicking the view grid quality tool, selecting the 2-D command, and checking the 2D grid of step A1;
c1, generating tetrahedral and hexahedral solid grids;
d1: connecting the model suture positions according to an intraoperative collection suture method;
e1: and selecting the stitched entity grids before framing through a face command, clicking to execute a face searching command, offsetting skin thickness by using the cartilage surface grids to simulate human skin, and clicking a 3D grid generation tool to generate entity grids with different skin thicknesses.
4. The method for optimizing a topological structure of a reconstructed ear support based on Finite Element Analysis (FEA) of claim 3, wherein the step E1 is implemented by generating a solid mesh with skin thickness of 0.5mm, 1mm or 2 mm.
5. The method of claim 1 for optimizing a topological structure of a reconstructed ear support based on finite element analysis, wherein the method comprises the following steps: the primary ear support body is an ear support body carved with costal cartilage of a target object, or a Medpor model or a Nagata model.
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