Finite element model modeling method capable of reproducing chest torsion performance

Abstract

The invention relates to the technical field of vehicle safety evaluation, in particular to a finite element model modeling method capable of reproducing chest torsion performance. Comprising the steps that the geometric contour of a thoracic cavity is extracted through a lying posture tomography image, the thoracic cavity structure comprises a sternum structure, a thoracic vertebra structure and a rib structure, the lobe posterior angle of the thoracic vertebra is corrected based on a standing posture X-ray computed tomography image, and a three-dimensional geometric model of the thoracic cavity is reconstructed; establishing a thoracic cavity finite element model through grid division and material attribute definition; establishing a spherical hinge between the thoracic vertebra transverse process and the rib head; assembling the thoracic cavity finite element model into a whole person element model; and carrying out parameterized model optimization. According to the technical scheme, the real anatomical structure and the chest response data of the multi-direction complex collision working condition can be combined to establish the high-biological fidelity finite element model capable of reproducing the chest torsion performance, so that the chest injury condition in the VRU traffic accident can be predicted more accurately.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle safety assessment, and in particular to a finite element modeling method capable of reproducing thoracic torsion performance. Background Art

[0002] In road traffic, vulnerable road users (VRU), such as pedestrians and cyclists, often face serious physical injuries when they encounter traffic accidents. Statistics show that severe chest injuries account for the second largest proportion of VRU injuries after head injuries, mainly in the form of rib fractures and lung contusions. These chest injuries not only bring great pain to patients, but may also lead to long-term functional impairment and medical burden.

[0003] However, the current vehicle safety assessment procedures mainly rely on tools such as head impactors, upper leg impactors and lower leg impactors to assess the safety of VRUs, and lack dedicated assessment tools for chest injuries. Although pedestrian physical dummies can predict chest injuries to a certain extent, their chest structures are extremely simplified and have high rigidity, and cannot accurately reproduce the complex movement of the chest in pedestrian collision accidents. Therefore, it is particularly urgent to develop an assessment tool that can accurately assess chest injuries.

[0004] With the rapid development of computer simulation technology, digital models have been widely used in biomechanical research. By constructing a sophisticated digital chest model, the mechanism of chest injury can be deeply studied to provide a scientific basis for vehicle safety design. However, most of the existing dummy finite element models are developed based on the response data of frontal collision or side collision, and cannot fully simulate the response of the chest under oblique impact. Although the human finite element model takes into account the response of frontal and side collisions, there are still deficiencies in the simulation under oblique impact, and it is difficult to accurately reflect the chest movement response under the combined action of compression and torsional loads. Summary of the invention

[0005] The purpose of the present invention is to propose a finite element modeling method that can reproduce the chest torsion performance. This technical solution can combine the real anatomical structure and the chest response data of multi-directional complex collision conditions to establish a high bio-fidelity finite element model that can reproduce the chest torsion performance, so as to more accurately predict the chest injuries in VRU traffic accidents.

[0006] To achieve the above-mentioned purpose, the embodiment of the present disclosure provides a finite element modeling method that can reproduce the torsion performance of the thoracic cavity, including: extracting the geometric contour of the thoracic cavity through lying tomography images, the thoracic cavity structure including the sternum, thoracic vertebrae and rib structures, correcting the thoracic kyphosis angle based on standing X-ray computed tomography images, and reconstructing the three-dimensional geometric model of the thoracic cavity; establishing a thorax finite element model through mesh division and material property definition; establishing a ball hinge between the transverse process of the thoracic vertebrae and the rib head; assembling the thorax finite element model into the whole person element model; and performing parameterized model optimization.

[0007] Beneficial effects of the basic scheme: By combining lying tomography images and standing X-ray computed tomography images, the geometric contour of the chest cavity can be accurately extracted, and then the thoracic kyphosis angle is measured based on the standing X-ray computed tomography images to correct the geometric model, thereby ensuring that the physiological curve of the thoracic spine is closer to the standing posture, making the established chest cavity model suitable for pedestrian chest injury research. Similarly, for vulnerable road users (VRU) in different emergency postures, this method can be used to correct the relative position of the chest cavity model.

[0008] A ball hinge is established between the transverse process of the thoracic vertebra and the rib head, and the motion relationship between the ribs and the thoracic vertebra is described by the rotational stiffness in three directions. The complex motion response is simplified, which can simulate the dynamic behavior of the thorax during torsion. The complexity of the joint response is restored through the ligaments at the costal head joint and the costotransverse process joint, and the elastic modulus value is adjusted to make it closer to the actual situation. This allows the model to more realistically reflect the mechanical properties and motion characteristics of the thorax, enhances the functionality of the model, and enables it to be used to study and analyze the performance of the thorax in complex movements.

[0009] Through parametric model optimization, by setting optimization goals, establishing mathematical problems, combining proxy models and optimization algorithms to find the best, we can obtain the chest finite element model parameters with the most realistic anti-thoracic compression and torsion performance. In addition, we can adjust the model parameters according to different research needs to generate chest finite element models with different characteristics.

[0010] This technical solution establishes a finite element model with high bio-fidelity by combining the real anatomical structure and chest response data of multi-directional complex collision conditions. This model can more accurately predict the chest injuries of VRU (vulnerable road users) in traffic accidents, thus providing a scientific basis for traffic accident analysis, safety assessment and injury prevention. This method can reduce the need for actual collision testing, reduce costs, and improve the efficiency and safety of research. In addition, this method is highly flexible and scalable, and can adapt to different research needs and application scenarios.

[0011] As an implementable preferred solution, the thoracic kyphosis angle is corrected based on standing X-ray computed tomography images, including the following: The thoracic spine includes T1 to T12. The angle between the upper end plate of the T1 thoracic spine and the lower end plate of the T12 thoracic spine in the initial geometric model is measured to obtain the thoracic kyphosis angle. , measuring the target thoracic kyphosis angle based on standing X-ray computed tomography images , the adjustment amount of the thoracic kyphosis angle is averaged to each thoracic vertebra, and the calculation formula of the adjustment amount of the adjacent thoracic kyphosis angle is as follows,

[0012] in, yes and The adjustment of the kyphosis angle of two adjacent thoracic vertebrae, is the thoracic kyphosis angle of the upper end plate of the T1 thoracic vertebra and the lower end plate of the T12 thoracic vertebra in the geometric model, It is the thoracic kyphosis angle of the upper end plate of the T1 thoracic vertebra and the lower end plate of the T12 thoracic vertebra in X-ray computed tomography images (X-ray). is the jth thoracic vertebra from top to bottom, and is the upper thoracic vertebra among the adjacent thoracic vertebrae. It is the lower thoracic vertebra among the adjacent thoracic vertebrae.

[0013] As an implementable preferred solution, the thoracic vertebra T6 or T7 is taken as a reference and remains stationary, and the other thoracic vertebrae are gradually rotated to both ends, so that the kyphosis angle of each thoracic vertebra is adjusted according to the adjustment amount; The adjusted geometric surface is smoothed and symmetrically processed. The smoothing is achieved by fitting curves or surfaces. The symmetrical processing is to symmetrically adjust the ribs and thoracic vertebrae on the left and right sides according to the symmetry of the human body.

[0014] As an implementable preferred solution, grid division includes the following contents: The internal cancellous bones of the sternum and ribs were simulated using eight-node hexahedral elements, the internal cancellous bones of the thoracic vertebrae were simulated using four-node tetrahedral elements, the cortical bones on the surface of the sternum, thoracic vertebrae and ribs were simulated using shell elements, and the cortical bones and cancellous bones were connected by common nodes; Two layers of eight-node hexahedral units are established between adjacent thoracic vertebrae to simulate the intervertebral disc. The inner 50% to 60% of the intervertebral disc is used as the nucleus pulposus, and the remaining outer area is used as the annulus fibrosus. The inner 50% to 60% of the intervertebral disc is used as the nucleus pulposus, and the remaining outer area is used as the annulus fibrosus. A layer of shell units is established on the outer surface of the annulus fibrosus for contact setting. Oblique beam units are established to simulate the direction of fibers inside the annulus fibrosus.

[0015] The costal cartilage between the sternum and the ribs is simulated using eight-node hexahedral elements, and a layer of shell elements is established on the surface of the costal cartilage to simulate the costal cartilage membrane. The thoracic vertebral ligaments, ligaments at the costocapitellar joints and ligaments at the costotransverse joints were simulated using four-node shell elements.

[0016] As an implementable preferred solution, the material property definition includes the following: The cancellous bone and costal cartilage are endowed with elastic-viscoplastic materials combining continuous injury mechanics, the cortical bone is endowed with isotropic elastic-plastic materials, the intervertebral disc is endowed with highly compressible foam materials, the costal cartilage membrane is endowed with hollow materials, and the ligaments are endowed with fabric materials.

[0017] As an implementable preferred solution, a ball hinge is established between the transverse process of the thoracic vertebra and the rib head, including the following: The local shell elements of the thoracic transverse process and the left and right rib heads are transformed into rigid bodies; a node is established at the center of the line segment connecting the costal head joint center and the costal transverse process joint center, and this node is set as the origin of the local coordinate system; based on the local coordinate system, a spherical hinge is established between the thoracic transverse process and the rib head, and the rotational stiffness S in three directions is defined X , S Y , S Z .

[0018] As an implementable preferred solution, the thorax finite element model is assembled into the whole person element model, including the following contents: The intercostal muscles are simulated by filling the adjacent ribs of the thoracic model with eight-node hexahedral units; a layer of shell units is established on the inner and outer surfaces for contact settings; the upper and lower thoracic vertebrae of the thoracic model are connected to the intervertebral discs of the cervical vertebrae and lumbar vertebrae respectively through binding contact; the automatic surface-to-surface contact between the inside of the thoracic cavity and the internal organs is defined; all the shell units of the thoracic model are added to the automatic single-surface contact of the whole human model; all the shell units of the thoracic model are added to the automatic single-surface contact of the whole human model; a one-dimensional unit is established between the thoracic bones and the surrounding muscles and soft tissues to simulate the connection relationship between the thoracic bones and the surrounding muscles and soft tissues.

[0019] As an implementable preferred solution, parameterized model optimization is performed, including the following contents: Extract the boundary conditions of chest head-on collision, side collision and oblique collision; use the constructed whole person finite element model to establish three sets of corresponding basic simulation models according to the boundary conditions; In the simulation model, the rotational stiffness S of the ball hinge in three directions at the costotransverse joint is X , S Y , S Z , Young's modulus E of the ligament at the costotransverse joint TCJ and the Young's modulus E of the ligament at the costal head jointRHJ As the optimization design variables, the vector , as follows:

[0020] The above parameters jointly determine the motion response characteristics of the thorax when subjected to external forces.

[0021] As an implementable preferred solution, parameterized model optimization is performed, including the following contents: The chest compression CC and deflection CD were defined as response indicators; The optimization goal is to simultaneously reduce the errors of the chest compression CCk,test and deflection CDk,test of the simulation model under the three working conditions of head-on collision, side collision and oblique collision relative to the chest compression CCk,PMHS and deflection CDk,PMHS of the biomechanical test, and establish the objective function as follows:

[0022]

[0023] in, represents the root mean square error of the compression, represents the root mean square error of the deflection, Indicates the working condition, Refers to the collision condition. Refers to side impact conditions. Refers to the oblique collision condition. is the design variable, refer to Working conditions The chest compression of the simulation model under variable conditions, refer to The chest compression of the corpse under working conditions, refer to Working conditions The chest deflection of the simulation model under variable conditions, refer to The amount of chest deflection of the corpse under working conditions; The multi-objective optimization problem is formulated as:

[0024] in, is the design variable space.

[0025] As an implementable preferred solution, parameterized model optimization also includes the following: Based on the orthogonal test matrix, the simulation experiment was designed. Through a large number of simulations, abundant data points were collected and the initial data set X was constructed. 0 , at this time the number of outer loops i=0; Based on the training data set, a variety of surrogate models were established, including response surface method, radial basis function, and Gaussian process; the surrogate models were screened through the validation data set, and the surrogate model with the highest fit was selected for subsequent optimization; Solve to get the optimal design variables And the theoretical response results , and bring this design variable into the simulation model for calculation, and extract the corresponding actual response results . Check whether this optimization process converges. If it converges, and the theoretical response result and The relative error is less than 5%, so the parameters of the optimal chest finite element model are If it does not converge, the number of cycles is i=i+1, and the data point ( , ) is added to the dataset to form dataset X i , continue the previous steps to iterate until the convergence condition is met. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of a logical approach to building a finite element model that can reproduce the torsional performance of the thoracic cavity.

[0027] Figure 2 Optimization flow chart for the parametric thorax model.

[0028] Figure 3 This is an axonometric view of the thoracic model.

[0029] Figure 4 It is a side cross-sectional view of the thoracic spine structure.

[0030] Figure 5 This is an oblique axonometric view of the thoracic spine structure.

[0031] Figure 6 Schematic diagram of chest compression and torsion measurement.

[0032] Figure 7 FIG. 4 is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings. It will be understood that the specific embodiments described herein are only partial embodiments of the present invention, which are only used to explain the present application, rather than to limit the present application. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated, and they can be combined with each other to achieve better technical effects. The same reference numerals appearing in the drawings of the following embodiments represent the same features or components, which can be applied to different embodiments.

[0034] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of the present invention should have the common meanings understood by those skilled in the art in the art to which the present invention belongs.

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings: Reference Figure 1 , an embodiment of the present disclosure provides a finite element modeling method that can reproduce the thoracic torsion performance, including the following steps.

[0036] Step S100, performing three-dimensional reconstruction of the chest cavity, includes: Step S101, a lying computed tomography (CT) image of a human body is obtained by a medical imaging device. The CT image has a high resolution and can clearly show the thoracic bone structure such as the sternum, thoracic vertebrae and ribs. The obtained CT image is imported into the medical imaging processing software for image preprocessing, including denoising, contrast enhancement, etc., to improve the accuracy of subsequent pixel segmentation.

[0037] Step S101, pixel segmentation of the lying computed tomography (CT) image is performed using medical image processing software. The geometric contours of the sternum, thoracic vertebrae (T1-T12) and ribs (Rib1-Rib12) are extracted. Medical image processing software, such as Mimics or 3D-Slicer, generally segment different tissues in the image by setting thresholds or using machine learning algorithms, and distinguish different tissues or structures in the image, thereby obtaining a clear bone contour and providing basic data for subsequent geometric model construction.

[0038] Step S1023, since the CT image is taken in a lying position, and the thoracic kyphosis angle of the human body will be different when the human body is standing, the thoracic kyphosis angle is corrected based on the standing X-ray computed tomography image (X-ray).

[0039] The angle between the upper endplate of the T1 thoracic vertebra and the lower endplate of the T12 thoracic vertebra in the initial geometric model was measured to obtain the thoracic kyphosis angle. , based on standing X-ray computed tomography (X-ray) images to measure the target thoracic kyphosis angle , the adjustment amount of the thoracic kyphosis angle is averaged to each thoracic vertebra, and the calculation formula of the adjustment amount of the adjacent thoracic kyphosis angle is as follows,

[0040] in, yes and The adjustment of the kyphosis angle of two adjacent thoracic vertebrae, is the thoracic kyphosis angle of the upper end plate of the T1 thoracic vertebra and the lower end plate of the T12 thoracic vertebra in the geometric model, It is the thoracic kyphosis angle of the upper end plate of the T1 thoracic vertebra and the lower end plate of the T12 thoracic vertebra in X-ray computed tomography images (X-ray). is the jth thoracic vertebra from top to bottom, and is the upper thoracic vertebra among the adjacent thoracic vertebrae. It is the lower thoracic vertebra among the adjacent thoracic vertebrae.

[0041] Step S104, taking the T6 (or T7) thoracic vertebra as the reference and keeping it fixed, gradually rotate the other thoracic vertebrae to both ends, so that the kyphosis angle of each thoracic vertebra is adjusted according to the adjustment amount. Then, slightly translate along the axial direction of the thoracic vertebra to ensure that the center distance between the adjacent end plates of the adjacent thoracic vertebrae before and after the adjustment remains unchanged, and check whether it is within the range of 2 to 4 mm.

[0042] Step S105, smoothing and symmetric processing are performed on the adjusted geometric surface to eliminate the geometric errors generated during the image segmentation and correction process. Smoothing can be achieved by fitting curves or surfaces to make the geometric model smoother; symmetric processing is to symmetrically adjust the ribs and thoracic vertebrae on both sides according to the symmetry of the human body to ensure the accuracy of the geometric model, and finally obtain a high-quality thoracic bone geometric model that meets the physiological flexion.

[0043] Step S200, meshing the thoracic skeleton model to obtain a thoracic finite element model, specifically includes: Step S201, meshing of the sternum and ribs, including: In step S201 - 1 , the internal cancellous bone of the sternum and ribs is simulated using eight-node hexahedron elements (HexahedronElement) to better capture the mechanical properties of the cancellous bone, such as compressibility and toughness.

[0044] In step S202-2, the surface cortical bones of the sternum and ribs are simulated using shell elements. Shell elements can accurately describe the thin shell structure of the cortical bones while reducing the amount of calculation. The thickness of the cortical bones is defined by the node thickness to ensure the accuracy of the model.

[0045] Step S202-3: The cortical bone and the cancellous bone are connected by a common node to ensure the mechanical continuity of the two.

[0046] Step S202, thoracic vertebrae mesh division, includes: Step S202-1, the internal cancellous bone of the T1-T12 thoracic vertebrae is simulated using a four-node tetrahedron element (TetrahedronElement). The tetrahedron element can flexibly adapt to complex geometric shapes and is suitable for simulating the internal cancellous bone of the thoracic vertebrae.

[0047] Step S202-2: The cortical bone on the surface of the thoracic vertebra is simulated using shell elements, which is consistent with the processing method of the sternum and ribs.

[0048] Step S203, intervertebral disc mesh division, includes: Step S203-1: Two layers of eight-node hexahedral units are established between adjacent thoracic vertebrae to simulate the intervertebral disc. The inner 50% to 60% area of ​​the intervertebral disc is used as the nucleus pulposus, and the remaining outer area is used as the annulus fibrosus, so as to accurately reflect the mechanical properties and structural characteristics of the intervertebral disc.

[0049] Step S203-2, a layer of hollow shell elements is established on the outer surface of the annulus fibrosus for contact setting, to ensure that the intervertebral disc can correctly interact with other structures during collision simulation.

[0050] Step S203-3, establishing an oblique beam unit to simulate the orientation of fibers inside the annulus fibrosus, so as to capture the mechanical response of the intervertebral disc under complex loads.

[0051] Step S204, meshing of the costal cartilage. The costal cartilage between the sternum and the ribs is simulated using eight-node hexahedral elements, and a layer of shell elements is established on the surface of the costal cartilage to simulate the costal cartilage membrane to ensure the integrity of the model.

[0052] Step S205, ligament mesh division, including: thoracic ligaments (including yellow ligament, supraspinal ligament, interspinous ligament, anterior longitudinal ligament, posterior longitudinal ligament, intertransverse ligament), ligaments at the costocranial joints (i.e. radial ligaments) and costotransverse joint ligaments (including superior costotransverse ligament and lateral costotransverse ligament) are all simulated using four-node shell elements to accurately reflect the mechanical properties and structural characteristics of the ligaments.

[0053] Step S206, assign corresponding material properties according to the actual mechanical properties of the ligament. In this embodiment, the cancellous bone and the costal cartilage are assigned with the elastic-viscoplastic material combined with continuous damage mechanics (MAT_DAMAGE_2), the cortical bone is assigned with the isotropic elastic-plastic material (MAT_PLASTICITY_WITH_DAMAGE), the intervertebral disc is assigned with the highly compressible foam material (MAT_FU_CHANG_FOAM), the costal perichondrium is assigned with the empty material (MAT_NULL), and the ligament is assigned with the fabric material (*MAT_FABRIC).

[0054] Step S300, define hinges and construct an adjustable multi-degree-of-freedom thorax model to simulate the joint response of the thorax in complex movements, providing a basis for subsequent whole-person model assembly and parameterized model optimization. Specifically, it includes: Step S301 , transforming the local shell elements of the transverse processes of the thoracic vertebrae T1 to T12 and the left and right rib heads Rib1 to Rib12 into rigid bodies, thereby simplifying the model and improving the calculation efficiency while maintaining the accuracy of the joint movement.

[0055] Step S302, establish a node at the center of the line segment connecting the costal head joint center and the costotransverse process joint center, and set this node as the origin of the local coordinate system. The establishment of the local coordinate system ensures the accuracy and controllability of the joint movement. The direction from the costal head joint center to the costotransverse process joint center is defined as the X-axis of the local coordinate system, and the direction from the upper end plate of the adjacent thoracic vertebral cone to the lower end plate is defined as the Z-axis of the local coordinate system. The Y-axis direction of the local coordinate system is determined according to the right-hand rule.

[0056] Step S303: Based on the local coordinate system, a spherical hinge is established between the transverse process of the thoracic vertebra and the rib head, and the rotational stiffness in three directions (S X , S Y , S Z ), the rotational stiffness parameter describes the relative motion characteristics of the ribs and thoracic vertebrae in different directions, and is the key to simulating the torsion performance of the thorax. Using the same method, a total of 24 ball hinges were established between T1 and the left and right Rib1, T2 and the left and right Rib2, and finally T12 and the left and right Rib12.

[0057] Step S304, combining the established ligaments at the costotransverse joint (including the superior costotransverse ligament, the lateral costotransverse ligament, etc.) to simulate the complex movement of the costotransverse joint. The introduction of the ligament increases the biofidelity of the model and makes the joint response closer to the real situation.

[0058] Step S400, assembling the human model, specifically includes: Step S401, fill the space between adjacent ribs of the chest model with eight-node hexahedral units to simulate intercostal muscles. Intercostal muscles are important muscle tissues that connect adjacent ribs and play an important role in maintaining the stability and shape of the chest. By simulating intercostal muscles, the chest model can produce a more realistic motion response when subjected to external forces.

[0059] Step S402, a layer of shell elements is established on the inner and outer surfaces for contact setting, to ensure that the chest model can generate correct contact force when in contact with other parts (such as internal organs, muscles, etc.), thereby more accurately simulating the motion response of the chest when subjected to external force.

[0060] Step S403, the upper and lower thoracic vertebrae of the thoracic cavity model are connected to the intervertebral discs of the cervical vertebrae and the lumbar vertebrae respectively through binding contact. The binding contact can ensure that the relative position and movement relationship between the thoracic vertebrae and the cervical vertebrae and the lumbar vertebrae conform to the actual situation of human anatomy.

[0061] Step S404, using *Contact_Automatic_Surface_To_Surface to define automatic surface contact between the chest cavity and the internal organs, so as to simulate the interaction force between the chest cavity and the internal organs, so as to more accurately predict the damage of the internal organs when the chest cavity is subjected to external force.

[0062] Step S405, all shell elements of the chest model are added to the automatic single-sided contact of the whole person model, so as to ensure the normal contact simulation between the chest model and the chest muscles, subcutaneous tissue and other structures. This ensures that the motion response of the chest model in the whole person model will not be disturbed by other parts, so as to more accurately predict the motion response and damage of the chest when subjected to external force.

[0063] Step S406, appropriately establish some one-dimensional units between the thoracic bones and the surrounding muscles and soft tissues to strengthen the connection, and construct a whole-person finite element model to further enhance the stability and biorealism of the whole-person model. By adding one-dimensional units, the connection relationship between the thoracic bones and the surrounding muscles and soft tissues can be simulated, thereby more accurately predicting the movement response and damage of the thorax when subjected to external forces.

[0064] Step S500, perform parameterized model optimization to finely adjust the parameters of the thorax finite element model to ensure that it can accurately reproduce the compression and torsion performance of the thorax under various collision conditions, referring to Figure 2 , including: Step S501, based on biomechanical data, the boundary conditions of chest head-on collision, side collision, and oblique collision are extracted. These boundary conditions record in detail the key information such as the impact force, impact direction, and action time of the chest cavity in the actual collision event. Subsequently, using the constructed whole person finite element model, three groups of corresponding basic simulation models are established according to the boundary conditions.

[0065] Step S502: In the simulation model, the rotational stiffness of the ball hinge in three directions at the costotransverse joint (S X , S Y , S Z ), Young's modulus of the ligament at the costotransverse joint (E TCJ ) and the Young's modulus of the ligament at the costal head joint (E RHJ ) as the optimization design variables, forming a vector , as follows:

[0066] The above parameters jointly determine the motion response characteristics of the thorax when subjected to external forces.

[0067] Step S503, chest compression (CC) and deflection (CD) are defined as response indicators. The chest compression is measured by the maximum change of the horizontal line segment (OC) connecting the sternum and the thoracic spine during the simulation process, while the chest deflection is defined by the angle change of the line connecting the sternum and the thoracic spine after the impact force.

[0068] Step S504, taking the error of chest compression (CCk,test) and deflection (CDk,test) of the simulation model under three working conditions of frontal collision, side collision and oblique collision as the optimization goal relative to the chest compression (CCk,PMHS) and deflection (CDk,PMHS) of the biomechanical test as the optimization goal, establish the objective function, as follows:

[0069]

[0070] in, represents the root mean square error of the compression, represents the root mean square error of the deflection, Indicates the working condition, Refers to the collision condition. Refers to side impact conditions. Refers to the oblique collision condition. is the design variable, refer to Working conditions The chest compression of the simulation model under variable conditions, refer to The chest compression of the corpse under working conditions, refer to Working conditions The chest deflection of the simulation model under variable conditions, refer to The amount of chest deflection of the corpse under working conditions.

[0071] The multi-objective optimization problem is formulated as:

[0072] in, is the design variable space. According to the actual situation, , , , This function comprehensively considers the errors under different working conditions and uses the root mean square error as the error metric. In this embodiment, the ligament material parameters and joint rotation stiffness parameters are set as design variables, and the root mean square error between the chest compression and torsion in the frontal collision, rear collision and side collision simulation tests and the response values ​​in the biomechanical test is set as the optimization target.

[0073] Step S505, design simulation experiments based on orthogonal test matrices to ensure that the value range of design variables can be covered as comprehensively as possible within a limited number of simulations. Through a large number of simulations, a wealth of data points are collected and an initial data set X is constructed. 0 , at this time the number of outer loops i=0.

[0074] Based on the training data set, a variety of surrogate models were established, including response surface method, radial basis function, Gaussian process, etc. These surrogate models can approximate the behavior of the simulation model at a low computational cost, thereby greatly accelerating the optimization process. The surrogate models were screened through the validation data set, and the surrogate model with the highest fit was selected for subsequent optimization.

[0075] In this embodiment, the number of loops in the optimization algorithm is set to 200 to ensure that the algorithm has enough iterations to converge to the optimal solution. In each iteration, the algorithm calculates the response of the surrogate model based on the current design variables and adjusts the design variables through the optimization algorithm to minimize the objective function.

[0076] Solve to get the optimal design variables And the theoretical response results , and bring this design variable into the simulation model for calculation, and extract the corresponding actual response results . Check whether this optimization process converges. If it converges, and the theoretical response result and The relative error is less than 5%, so the parameters of the optimal chest finite element model are If it does not converge, the number of cycles is i=i+1, and the data point ( , ) is added to the dataset to form dataset X i , continue the previous steps to iterate until the convergence condition is met.

[0077] Reference Figures 3 to 5 , is a schematic diagram of the structure of the digital thoracic model of the present invention, including: 1-sternum, 2-thoracic vertebrae (201-T1 thoracic vertebrae, 202-T2 thoracic vertebrae, 203-T3 thoracic vertebrae, 204-T4 thoracic vertebrae, 205-T5 thoracic vertebrae, 206-T6 thoracic vertebrae, 207-T7 thoracic vertebrae, 208-T8 thoracic vertebrae, 209-T9 thoracic vertebrae, 210-T10 thoracic vertebrae, 211-T11 thoracic vertebrae, 212-T13 thoracic vertebrae, 213-T14 thoracic vertebrae, 214-T15 thoracic vertebrae, 215-T16 thoracic vertebrae, 216-T17 thoracic vertebrae, 217-T18 thoracic vertebrae, 218-T19 thoracic vertebrae, 220-T20 thoracic vertebrae, 221-T21 2-T12 thoracic vertebra), 3-nucleus pulposus of intervertebral disc, 4-annulus fibrosus of intervertebral disc, 5-left ribs (501-1st rib on the left, 502-2nd rib on the left, 503-3rd rib on the left, 504-4th rib on the left, 505-5th rib on the left, 506-6th rib on the left, 507-7th rib on the left, 508-8th rib on the left, 509-9th rib on the left, 510-10th rib on the left, 511-11th rib on the left, 512-12th rib on the left), 6-left costal cartilage, 7-right ribs (701-1st rib on the right, 702-2nd rib on the right, 703-3rd rib on the right, 704-4th rib on the right, 705-5th rib on the right, 706-6th rib on the right, 707-7th rib on the right, 708-8th rib on the right Ribs, 709-9th rib on the right, 710-10th rib on the right, 711-11th rib on the right, 712-12th rib on the right), 8-right costal cartilage, 9-yellow ligament, 10-supraspinous ligament, 11-interspinous ligament, 12-posterior longitudinal ligament, 13-anterior longitudinal ligament, 14-intertransverse ligament, 15-radial ligament, 16-superior costotransverse ligament, 17-lateral costotransverse ligament.

[0078] Reference Figure 6 , is a schematic diagram for measuring chest compression and torsion. In the figure, point T represents the thoracic vertebrae of the chest model, point O represents the midpoint of the line connecting the sternum and thoracic vertebrae in the initial state of the chest model, point C represents the closest point along the impact direction in the initial state of the chest model, point O' represents the midpoint of the line connecting the sternum and thoracic vertebrae after the chest model is subjected to impact force, and point C' represents the position of point C after the chest model is subjected to impact force. The length change of OC, i.e. OC-O'C', is the chest compression, and the angle change of OT, i.e. ∠OTO', is the chest torsion.

[0079] The embodiment of the present disclosure also provides a storage medium, in which a computer program is stored. When the computer program is executed by a processor, all steps of the above-mentioned finite element modeling method that can reproduce the thoracic torsion performance can be implemented.

[0080] Those of ordinary skill in the art can understand that all or part of the processes in the finite element modeling method for reproducing thoracic torsion performance can be completed by instructing related hardware through a computer program, and the program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of various embodiments of the finite element modeling method for reproducing thoracic torsion performance. Among them, any reference to memory, storage, database or other media used in the embodiments provided in the present application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0081] The embodiment of the present application also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the finite element modeling method for reproducing the thoracic torsion performance are implemented. In the embodiment of the present application, the processor is the control center of the computer system, which can be a processor of a physical machine or a processor of a virtual machine.

[0082] Reference Figure 7 , the electronic device 500 includes: at least one processor 501, at least one communication interface 502, at least one memory 503 and at least one bus 504. The bus 504 is used to realize the connection and communication between these components, the communication interface 502 is used to communicate signaling or data with other node devices, and the memory 503 stores machine-readable instructions executable by the processor 501. When the electronic device 500 is running, the processor 501 communicates with the memory 503 through the bus 504, and when the machine-readable instructions are called by the processor 501, the steps of the finite element modeling method for reproducing the thoracic torsion performance as described above are executed.

[0083] The above contents are only embodiments of the present invention. The common sense such as the known specific structures and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field to which the invention belongs before the application date or the priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for the ordinary technicians in the relevant field to implement this application. It should be pointed out that for the technicians in this field, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to explain the content of the claims.

Claims

1. A finite element modeling method capable of reproducing thoracic torsion performance, characterized in that: include: The geometric contour of the thorax is extracted from the lying tomography images. The thorax structure includes the sternum, thoracic vertebrae and rib structures. The thoracic kyphosis angle is corrected based on the standing X-ray computed tomography images to reconstruct the 3D geometric model of the thorax. The thorax finite element model is established through meshing and material property definition. A ball hinge is established between the transverse process of the thoracic vertebrae and the rib head. The thorax finite element model is assembled into the whole person element model. Perform parameterized model optimization.

2. A finite element modeling method capable of reproducing thoracic torsion performance according to claim 1, characterized in that: The thoracic kyphosis angle was corrected based on standing X-ray computed tomography images, including the following: The thoracic spine includes T1 to T12. The angle between the upper end plate of the T1 thoracic spine and the lower end plate of the T12 thoracic spine in the initial geometric model is measured to obtain the thoracic kyphosis angle. , measuring the target thoracic kyphosis angle based on standing X-ray computed tomography images , the adjustment amount of the thoracic kyphosis angle is averaged to each thoracic vertebra, and the calculation formula of the adjustment amount of the adjacent thoracic kyphosis angle is as follows, in, yes and The adjustment of the kyphosis angle of two adjacent thoracic vertebrae, is the thoracic kyphosis angle of the upper end plate of the T1 thoracic vertebra and the lower end plate of the T12 thoracic vertebra in the geometric model, It is the thoracic kyphosis angle of the upper end plate of the T1 thoracic vertebra and the lower end plate of the T12 thoracic vertebra in X-ray computed tomography images (X-ray). is the jth thoracic vertebra from top to bottom, and is the upper thoracic vertebra among the adjacent thoracic vertebrae. It is the lower thoracic vertebra among the adjacent thoracic vertebrae.

3. A finite element modeling method capable of reproducing thoracic torsion performance according to claim 2, characterized in that: Take the T6 or T7 thoracic vertebra as the reference and keep it fixed, and gradually rotate the other thoracic vertebrae to both ends, so that the kyphosis angle of each thoracic vertebra is adjusted according to the adjustment amount; The adjusted geometric surface is smoothed and symmetrically processed. The smoothing is achieved by fitting curves or surfaces. The symmetrical processing is to symmetrically adjust the ribs and thoracic vertebrae on the left and right sides according to the symmetry of the human body.

4. A finite element modeling method capable of reproducing thoracic torsion performance according to claim 1, characterized in that: Meshing, including the following: The internal cancellous bones of the sternum and ribs were simulated using eight-node hexahedral elements, the internal cancellous bones of the thoracic vertebrae were simulated using four-node tetrahedral elements, the cortical bones on the surface of the sternum, thoracic vertebrae and ribs were simulated using shell elements, and the cortical bones and cancellous bones were connected by common nodes; Two layers of eight-node hexahedral units are established between adjacent thoracic vertebrae to simulate the intervertebral disc. The inner 50% to 60% of the intervertebral disc is used as the nucleus pulposus, and the remaining outer area is used as the annulus fibrosus. The inner 50% to 60% of the intervertebral disc is used as the nucleus pulposus, and the remaining outer area is used as the annulus fibrosus. A layer of shell units is established on the outer surface of the annulus fibrosus for contact setting. Oblique beam units are established to simulate the direction of fibers inside the annulus fibrosus. The costal cartilage between the sternum and the ribs is simulated using eight-node hexahedral elements, and a layer of shell elements is established on the surface of the costal cartilage to simulate the costal cartilage membrane. The thoracic vertebral ligaments, ligaments at the costocapitellar joints and ligaments at the costotransverse joints were simulated using four-node shell elements.

5. A finite element modeling device capable of reproducing thoracic torsion performance according to claim 1 or 4, characterized in that: Material property definition, including the following: The cancellous bone and costal cartilage are endowed with elastic-viscoplastic materials combining continuous injury mechanics, the cortical bone is endowed with isotropic elastic-plastic materials, the intervertebral disc is endowed with highly compressible foam materials, the costal cartilage membrane is endowed with hollow materials, and the ligaments are endowed with fabric materials.

6. A finite element modeling method capable of reproducing thoracic torsion performance according to claim 1, characterized in that: Create a ball hinge between the transverse processes of the thoracic vertebrae and the rib heads, including the following: The local shell elements of the thoracic transverse process and the left and right rib heads are transformed into rigid bodies; a node is established at the center of the line segment connecting the costal head joint center and the costal transverse process joint center, and this node is set as the origin of the local coordinate system; based on the local coordinate system, a spherical hinge is established between the thoracic transverse process and the rib head, and the rotational stiffness S in three directions is defined X , S Y , S Z .

7. A finite element modeling method capable of reproducing thoracic torsion performance according to claim 4, characterized in that: Assemble the thorax finite element model into the whole person metamodel, including the following: The intercostal muscles are simulated by filling the adjacent ribs of the thoracic model with eight-node hexahedral units; a layer of shell units is established on the inner and outer surfaces for contact settings; the upper and lower thoracic vertebrae of the thoracic model are connected to the intervertebral discs of the cervical vertebrae and lumbar vertebrae respectively through binding contact; the automatic surface-to-surface contact between the inside of the thoracic cavity and the internal organs is defined; all the shell units of the thoracic model are added to the automatic single-surface contact of the whole human model; all the shell units of the thoracic model are added to the automatic single-surface contact of the whole human model; a one-dimensional unit is established between the thoracic bones and the surrounding muscles and soft tissues to simulate the connection relationship between the thoracic bones and the surrounding muscles and soft tissues.

8. The finite element modeling method capable of reproducing thoracic torsion performance according to claim 1, characterized in that: Perform parameterized model optimization, including the following: Extract the boundary conditions of chest head-on collision, side collision and oblique collision; use the constructed whole person finite element model to establish three sets of corresponding basic simulation models according to the boundary conditions; In the simulation model, the rotational stiffness S of the ball hinge in three directions at the costotransverse joint is X , S Y , S Z , Young's modulus E of the ligament at the costotransverse joint TCJ and the Young's modulus E of the ligament at the costal head joint RHJ As the optimization design variable, the vector , as follows: The above parameters jointly determine the motion response characteristics of the thorax when subjected to external forces.

9. A finite element modeling method capable of reproducing thoracic torsion performance according to claim 8, characterized in that: Perform parameterized model optimization, including the following: The chest compression CC and deflection CD were defined as response indicators; The optimization goal is to simultaneously reduce the errors of the chest compression CCk,test and deflection CDk,test of the simulation model under the three working conditions of head-on collision, side collision and oblique collision relative to the chest compression CCk,PMHS and deflection CDk,PMHS of the biomechanical test, and establish the objective function as follows: in, represents the root mean square error of the compression, represents the root mean square error of the deflection, Indicates the working condition, Refers to the collision condition. Refers to side impact conditions. Refers to the oblique collision condition. is the design variable, refer to Working conditions The chest compression of the simulation model under variable conditions, refer to The chest compression of the corpse under working conditions, refer to Working conditions The chest deflection of the simulation model under variable conditions, refer to The amount of chest deflection of the corpse under working conditions; The multi-objective optimization problem is formulated as: in, is the design variable space.

10. A finite element modeling method capable of reproducing thoracic torsion performance according to claim 9, characterized in that: Parameterized model optimization also includes the following: Based on the orthogonal test matrix, the simulation experiment was designed. Through a large number of simulations, abundant data points were collected and the initial data set X was constructed. 0 , at this time the number of outer loops i=0; Based on the training data set, a variety of surrogate models were established, including response surface method, radial basis function, and Gaussian process; the surrogate models were screened through the validation data set, and the surrogate model with the highest fit was selected for subsequent optimization; Solve to get the optimal design variables And the theoretical response results , and bring this design variable into the simulation model for calculation to extract the corresponding actual response results . Check whether this optimization process converges. If it converges, and the theoretical response result and The relative error is less than 5%, so the parameters of the optimal chest finite element model are If it does not converge, the number of cycles is i=i+1, and the data point ( , ) is added to the dataset to form dataset X i , continue the previous steps to iterate until the convergence condition is met.

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