A finite element modeling method for reproducible thoracic torsion performance

Abstract

The present application relates to the technical field of vehicle safety evaluation, and particularly relates to a finite element model modeling method capable of reproducing chest cavity torsion performance. The method comprises the following steps: extracting the geometric profile of the chest cavity from a lying posture tomography image, the chest cavity structure comprising a breastbone, thoracic vertebrae and rib structure, correcting the thoracic vertebrae kyphosis angle based on a standing posture X-ray computed tomography image, and reconstructing a three-dimensional geometric model of the chest cavity; establishing a chest cavity finite element model through mesh division and material attribute definition; establishing a spherical hinge between the thoracic vertebrae transverse process and the rib head; assembling the chest cavity finite element model into a whole human body finite element model; and performing parameterized model optimization. The technical scheme can combine real anatomical structure and chest response data under complex collision conditions in multiple directions to establish a high-biometric finite element model capable of reproducing chest cavity torsion performance, so as to more accurately predict chest injury in VRU traffic accidents.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle safety evaluation, and particularly relates to a finite element model modeling method capable of reproducing thoracic twist performance. BACKGROUND

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

[0003] However, in current vehicle safety evaluation procedures, tools such as head impactors, upper leg impactors, and lower leg impactors are mainly used to evaluate the safety of VRUs, and there is a lack of specialized evaluation tools for thoracic injuries. Although the physical dummy of a pedestrian can predict thoracic injuries to some extent, the chest structure is greatly simplified and has high stiffness, which cannot accurately reproduce the complex motion of the thoracic cavity in a pedestrian collision accident. Therefore, it is particularly urgent to develop an evaluation tool that can accurately evaluate thoracic injuries.

[0004] With the rapid development of computer simulation technology, digital models have been widely used in biomechanical research. By constructing a detailed thoracic digital model, the mechanism of thoracic injury can be deeply studied, providing a scientific basis for vehicle safety design. However, existing dummy finite element models are mostly developed based on the response data of frontal or lateral collisions, and cannot fully simulate the response of the thorax under oblique impact. Although the human body finite element model considers the response of frontal and lateral collisions, the simulation under oblique impact still has deficiencies, and it is difficult to accurately reflect the motion response of the thoracic cavity under the combined action of compression and torsion load. SUMMARY

[0005] The purpose of the present application is to provide a finite element model modeling method capable of reproducing thoracic twist performance. This technical solution can combine real anatomical structures and thoracic response data under complex multi-directional collision conditions to establish a high-biometric finite element model capable of reproducing thoracic twist performance, so as to more accurately predict thoracic injuries in VRU traffic accidents.

[0006] To achieve the above-mentioned purpose, the embodiment of the present disclosure provides a finite element model modeling method capable of reproducing the chest cavity torsion performance, comprising: extracting the geometric profile of the chest cavity through a lying posture tomography image, the chest cavity structure including a sternum, a thoracic vertebra and a rib structure, correcting the thoracic vertebra kyphosis angle based on a standing posture X-ray computed tomography image, and reconstructing a chest cavity three-dimensional geometric model; establishing a chest 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 chest cavity finite element model into a whole human body finite element model; and performing parameterized model optimization.

[0007] The beneficial effects of the basic scheme: by combining the lying posture tomography image and the standing posture X-ray computed tomography image, the geometric profile of the chest cavity can be accurately extracted, and then the thoracic vertebra kyphosis angle is measured based on the standing posture X-ray computed tomography image, the geometric model is corrected, so as to ensure that the physiological curve of the thoracic vertebra is closer to the standing posture, so that the chest cavity model established is suitable for pedestrian chest injury research. Similarly, for road vulnerable users (VRU) in different emergency postures, this method can be used to correct the relative position of the chest cavity model.

[0008] A spherical hinge is established between the thoracic vertebra transverse process and the rib head, 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, the dynamic behavior of the chest cavity in the torsion process can be simulated, the complexity of joint response is restored through the ligaments at the rib head joint and the transverse process joint, the elastic modulus value is adjusted to be closer to the real situation, so that the model can more truly reflect the mechanical properties and motion characteristics of the chest cavity, and the functionality of the model is enhanced, so that it can be used for research and analysis of the performance of the chest cavity in complex motion.

[0009] Through parameterized model optimization, an optimization target is set, a mathematical problem is established, an optimization algorithm is combined with a surrogate model to optimize, and the chest cavity finite element model parameters most truly reflecting the compression and torsion performance of the chest cavity are obtained. In addition, the model parameters can be adjusted according to different research needs, so as to generate chest cavity finite element models with different characteristics.

[0010] The technical scheme combines the real anatomical structure and the chest response data of complex multi-directional collision conditions to establish a high-biologic finite element model. The model can more accurately predict the chest injury of VRU (vulnerable road user) in a traffic accident, thereby providing a scientific basis for traffic accident analysis, safety evaluation and injury prevention. Through this method, the need for actual crash tests can be reduced, the cost can be reduced, and the efficiency and safety of research can be improved. In addition, the method has high flexibility and scalability, and can adapt to different research needs and application scenarios.

[0011] As an implementable preferred solution, the kyphosis angle of the thoracic vertebrae is corrected based on the standing X-ray computed tomography image, including the following contents:

[0012] The thoracic vertebrae include T1 to T12, the included angle between the upper end plate of the T1 thoracic vertebra and the lower end plate of the T12 thoracic vertebra in the initial geometric model is measured to obtain the kyphosis angle of the thoracic vertebrae The kyphosis angle of the target thoracic vertebrae is measured based on the standing X-ray computed tomography image The adjustment amount of the kyphosis angle of the thoracic vertebrae is averaged to each thoracic vertebra, and the calculation formula of the adjustment amount of the adjacent thoracic vertebrae is as follows,

[0013]

[0014] Wherein, is and the adjustment amount of the kyphosis angle of two adjacent thoracic vertebrae, is the kyphosis angle of the thoracic vertebrae of the T1 thoracic vertebra upper end plate and the T12 thoracic vertebra lower end plate in the geometric model, is the kyphosis angle of the T1 thoracic vertebra upper end plate and the T12 thoracic vertebra lower end plate in the X-ray computed tomography image (X-ray), is the jth thoracic vertebra counted from top to bottom, and is the upper thoracic vertebra among the adjacent thoracic vertebrae, is the lower thoracic vertebra among the adjacent thoracic vertebrae.

[0015] As an implementable preferred solution, the thoracic vertebrae of T6 or T7 are taken as the reference 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;

[0016] The adjusted geometric surface is smoothed and symmetrized, the smoothing is realized by fitting a curve or a surface, and the symmetry is adjusted according to the symmetry of the human body to adjust the ribs and thoracic vertebrae on the left and right sides.

[0017] As an implementable preferred solution, the mesh division includes the following contents:

[0018] The interior cancellous bone of the sternum and the ribs is simulated by eight-node hexahedral elements, the interior cancellous bone of the thoracic vertebrae is simulated by four-node tetrahedral elements, the cortical bone on the surface of the sternum, the thoracic vertebrae and the ribs is simulated by shell elements, and the cortical bone and the cancellous bone are connected by shared nodes;

[0019] Two layers of eight-node hexahedral elements are established between adjacent thoracic vertebrae to simulate the intervertebral disc, 50% to 60% of the interior region of the intervertebral disc is used as the nucleus pulposus, and the remaining external region is used as the annulus fibrosus, 50% to 60% of the interior region of the intervertebral disc is used as the nucleus pulposus, and the remaining external region is used as the annulus fibrosus; a layer of empty shell elements is established on the outer surface of the annulus fibrosus for contact setting; diagonal beam elements are established to simulate the direction of the fibers in the annulus fibrosus.

[0020] The costal cartilage between the sternum and the ribs is simulated by 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

[0021] The thoracic vertebral ligament, the costal head joint ligament and the costal transverse process joint ligament are simulated by four-node shell elements.

[0022] As an implementable preferred solution, the material attribute definition includes the following:

[0023] The cancellous bone and the costal cartilage are endowed with an elastic-viscoplastic material combined with continuous damage mechanics, the cortical bone is endowed with an isotropic elastic-plastic material, the intervertebral disc is endowed with a highly compressible foam material, the costal cartilage membrane is endowed with an empty material, and the ligament is endowed with a fabric material.

[0024] As an implementable preferred solution, the spherical hinge is established between the thoracic transverse process and the rib head, including the following:

[0025] The local shell elements of the thoracic transverse process and the left and right rib heads are converted into rigid bodies; a node is established at the center of the line segment connecting the center of the costal head joint and the center of the costal transverse process joint, and the 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 X , S Y , S Z .

[0026] As an implementable preferred solution, the thoracic cavity finite element model is assembled into a whole human finite element model, including the following:

[0027] The eight-node hexahedral elements are filled between the adjacent ribs of the thoracic cavity model to simulate the intercostal muscles; a layer of shell elements is established on the inner and outer surfaces for contact setting; the upper and lower thoracic vertebrae of the thoracic cavity model are connected with the intervertebral discs of the cervical vertebrae and the lumbar vertebrae through binding contact, respectively; the automatic surface-to-surface contact between the thoracic cavity and the internal organs is defined; all the shell elements of the thoracic cavity model are added to the automatic single-surface contact of the whole human model; all the shell elements of the thoracic cavity model are added to the automatic single-surface contact of the whole human model; one-dimensional elements are established between the thoracic cavity bones and the surrounding muscles and soft tissues to simulate the connection relationship between the thoracic cavity bones and the surrounding muscles and soft tissues.

[0028] As an implementable preferred solution, the parameterized model optimization is performed, including the following:

[0029] The boundary conditions of the thoracic collision in the frontal, lateral and oblique directions are extracted; three groups of corresponding basic simulation models are established according to the boundary conditions by using the whole human finite element model that has been constructed;

[0030] In the simulation model, the rotational stiffness S of the spherical hinge in three directions at the costovertebral joint X Y Z the Young's modulus E of the costovertebral ligament TCJ and the Young's modulus E of the costotransverse ligament RHJ as the optimization design variables, constituting a vector , as follows:

[0031]

[0032] The above parameters jointly determine the motion response characteristics of the thorax when subjected to external forces.

[0033] As an implementable preferred scheme, the parameterized model optimization includes the following contents:

[0034] Define the thoracic compression CC and deflection CD as response indicators;

[0035] Take the error of the thoracic compression CCk,test and deflection CDk,test of the simulation model relative to the thoracic compression CCk,PMHS and deflection CDk,PMHS of the biomechanical test under the three working conditions of frontal collision, side collision and oblique collision as the optimization target, and establish the objective function as follows:

[0036]

[0037]

[0038] wherein, RMS error of the compression amount, RMS error of the deflection amount, indicates the working condition, refers to the frontal collision condition, refers to the side collision condition, refers to the oblique collision condition, is the design variable, refers to the thoracic compression amount of the simulation model under the variable condition, refers to the thoracic compression amount of the cadaver under the variable condition, the thoracic deflection amount of the simulation model under the variable condition, refers to the thoracic deflection amount of the cadaver under the

[0039] Express the multi-objective optimization problem as:

[0040] ​​

[0041] wherein, is the design variable space.

[0042] As an implementable preferred solution, the parameterized model optimization further comprises the following:

[0043] Based on the orthogonal test matrix design simulation test, a large number of simulations are performed to collect rich data points and build an initial data set X 0 At this time, the outer loop number i = 0;

[0044] Based on the training data set, a variety of surrogate models are established, including response surface method, radial basis function, and Gaussian process; the surrogate models are screened through the validation data set, and the surrogate model with the highest fitting degree is selected for subsequent optimization;

[0045] The optimal design variable and the theoretical response result are obtained, and the design variable is brought into the simulation model for calculation to extract the corresponding actual response result . Check whether the optimization process converges, if it converges, and the relative error between the theoretical response result and is less than 5%, then the parameters of the optimal chest finite element model are If it does not converge, the loop number is i = i + 1, the data points , are added to the data set to form the data set X i , and the previous steps are continued for iteration until the convergence condition is met. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a logic diagram of a reproducible finite element model modeling method for chest cavity torsion performance.

[0047] Figure 2 is a parameterized chest model optimization flowchart.

[0048] Figure 3 is an axonometric view of the chest model.

[0049] Figure 4 is a side sectional view of the thoracic spine structure.

[0050] Figure 5 is an oblique axonometric view of the thoracic spine structure.

[0051] Figure 6 is a schematic diagram of chest compression and torsion measurement.

[0052] Figure 7A structural schematic diagram of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0053] In order to make the technical solutions of the present application and the advantages thereof clearer, the technical solutions of the present application will be further described in detail below with reference to the drawings. It should be understood that the specific embodiments described herein are only partial embodiments of the present application, and are only used to explain the present application, but not 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 in isolation, 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.

[0054] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of the present application should have the usual meanings understood by those of ordinary skill in the art to which the present application belongs.

[0055] The present application will be further described in detail below with reference to the drawings:

[0056] With reference to Figure 1 The present embodiment provides a finite element model modeling method capable of reproducing thoracic cavity torsion performance, comprising the following steps.

[0057] Step S100, three-dimensional reconstruction is performed on the thoracic cavity, comprising:

[0058] Step S101, a lying posture computed tomography (CT) image of a human body is acquired by a medical imaging device. The CT image has high resolution and can clearly show the thoracic skeletal structures such as the sternum, thoracic vertebrae and ribs. The acquired CT image is imported into a medical image processing software for image preprocessing, including denoising, contrast enhancement, etc., to improve the accuracy of subsequent pixel segmentation.

[0059] Step S101, pixel segmentation is performed on the lying posture computed tomography (CT) image by a 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 segments different tissues in the image by setting a threshold or using machine learning algorithms, etc. to distinguish different tissues or structures in the image, thereby obtaining clear bone contours to provide basic data for subsequent geometric model construction.

[0060] Step S1023, since the CT image is taken in a lying posture, the thoracic vertebrae kyphosis angle will be different in a standing state, therefore, the thoracic vertebrae kyphosis angle is corrected based on a standing posture X-ray computed tomography image (X-ray).

[0061] The thoracic kyphosis angle is obtained by measuring the angle between the planes of the superior end plate of the T1 thoracic vertebra and the inferior end plate of the T12 thoracic vertebra in the initial geometric model. Measurement of the kyphosis angle of the target thoracic vertebra based on standing X-ray computed tomography images. The adjustment amount of the thoracic kyphosis angle is averaged across all thoracic vertebrae. The formula for calculating the adjustment amount of the kyphosis angle of adjacent thoracic vertebrae is as follows.

[0062]

[0063] in, yes and The adjustment amount of the kyphosis angle between two adjacent thoracic vertebrae. It is the thoracic kyphosis angle of the upper end plate of T1 thoracic vertebra and the lower end plate of T12 thoracic vertebra in the geometric model. It refers to the thoracic kyphosis angle of the superior plateau of the T1 thoracic vertebra and the inferior plateau of the T12 thoracic vertebra in an X-ray computed tomography (CT) image. It is the j-th thoracic vertebra counting from top to bottom, and is the uppermost of the adjacent thoracic vertebrae. It is the lower thoracic vertebra among the adjacent thoracic vertebrae.

[0064] In step S104, using the T6 (or T7) thoracic vertebra as a reference, gradually rotate the other thoracic vertebrae to both ends, adjusting the kyphosis angle of each thoracic vertebra according to the adjustment amount. Then, slightly translate along the thoracic vertebral axis to ensure that the center-to-center distance between adjacent endplates of adjacent thoracic vertebrae remains unchanged before and after adjustment, and check whether it is within the range of 2-4 mm.

[0065] Step S105 involves smoothing and symmetry processing of the adjusted geometric surface to eliminate geometric errors caused by image segmentation and correction. Smoothing can be achieved by fitting curves or surfaces to make the geometric model smoother; symmetry processing involves symmetrically adjusting the ribs and thoracic vertebrae on both sides according to the symmetry of the human body to ensure the accuracy of the geometric model, ultimately obtaining a high-quality thoracic skeleton geometric model that conforms to physiological curvature.

[0066] Step S200 involves meshing the thoracic skeleton model to obtain a finite element model of the thoracic cavity, specifically including:

[0067] Step S201, sternum and rib mesh division, including:

[0068] In step S201-1, the internal cancellous bone of the sternum and ribs is simulated using eight-node hexahedron elements to better capture the mechanical properties of cancellous bone, such as compressibility and toughness.

[0069] Step S202-2, the surface cortex bone of the sternum and the rib is simulated by shell element. Shell element can accurately describe the thin shell structure of the cortex bone, while reducing the amount of calculation. The thickness of the cortex bone is defined by the node thickness, ensuring the accuracy of the model.

[0070] Step S202-3, the connection between the cortex bone and the cancellous bone is realized by shared node, ensuring the mechanical continuity of the two.

[0071] Step S202, the meshing of the thoracic vertebrae, including:

[0072] Step S202-1, the internal cancellous bone of T1-T12 thoracic vertebrae is simulated by tetrahedron element. Tetrahedron element can flexibly adapt to complex geometry, and is suitable for the simulation of the internal cancellous bone of the thoracic vertebrae.

[0073] Step S202-2, the cortex bone on the surface of the thoracic vertebrae is simulated by shell element, which is consistent with the processing method of the sternum and the rib.

[0074] Step S203, the meshing of the intervertebral disc, including:

[0075] Step S203-1, two layers of eight-node hexahedron elements are established between adjacent thoracic vertebrae to simulate the intervertebral disc. The internal 50%-60% area of the intervertebral disc is used as the nucleus pulposus, and the remaining external area is used as the annulus fibrosus, so as to accurately reflect the mechanical properties and structural characteristics of the intervertebral disc.

[0076] Step S203-2, a layer of empty shell element is established on the outer surface of the annulus fibrosus for contact setting, so that the intervertebral disc can correctly interact with other structures when simulating the collision.

[0077] Step S203-3, diagonal beam elements are established to simulate the direction of the fibers in the annulus fibrosus, which is convenient for capturing the mechanical response of the intervertebral disc under complex load.

[0078] Step S204, the meshing of the costal cartilage, the costal cartilage between the sternum and the rib is simulated by eight-node hexahedron element, and a layer of shell element is established on the surface of the costal cartilage to simulate the costal cartilage membrane, ensuring the integrity of the model.

[0079] Step S205, the meshing of the ligament, including: the thoracic ligament (including the yellow ligament, supraspinous ligament, interspinous ligament, anterior longitudinal ligament, posterior longitudinal ligament, intertransverse ligament), the ligament at the costal head joint (i.e. radiate ligament) and the costotransverse ligament (including costotransverse superior ligament, costotransverse lateral ligament) are simulated by four-node shell element, so as to accurately reflect the mechanical properties and structural characteristics of the ligament.

[0080] Step S206, according to the actual mechanical properties of ligament, the corresponding material properties are given. In this embodiment, the cancellous bone and costal cartilage are given the elastic-viscoplastic material (MAT_DAMAGE_2) combined with continuous damage mechanics, the cortical bone is given the isotropic elastic-plastic material (MAT_PLASTICITY_WITH_DAMAGE), the intervertebral disc is given the highly compressible foam material (MAT_FU_CHANG_FOAM), the costal cartilage membrane is given the null material (MAT_NULL), and the ligament is given the fabric material (*MAT_FABRIC).

[0081] Step S300, hinge definition is performed, and an adjustable multi-degree-of-freedom chest model is constructed to simulate the joint response of the chest in complex motion, thereby providing a basis for subsequent whole-person model assembly and parameterized model optimization. Specifically, the following steps are included:

[0082] Step S301, local shell elements of T1-T12 thoracic vertebrae transverse processes and left and right Rib1-Rib12 rib heads are converted into rigid bodies, so as to simplify the model and improve the calculation efficiency, while the accuracy of joint motion is maintained.

[0083] Step S302, a node is established at the center of a line segment connecting the center of the costal head joint and the center of the transverse costal joint, and the node is set as the origin of the local coordinate system. The establishment of the local coordinate system ensures the accuracy and controllability of the joint motion. The direction from the center of the costal head joint to the center of the transverse costal joint is defined as the X-axis of the local coordinate system, and the direction from the upper end plate to the lower end plate of the adjacent thoracic vertebrae cone is defined as the Z-axis of the local coordinate system. The direction of the Y-axis of the local coordinate system is determined according to the right-hand rule.

[0084] Step S303, based on the local coordinate system, a spherical hinge is established between the thoracic vertebrae transverse process and the rib head, and three-direction rotational stiffness (S X , S Y , S Z ) are defined. The rotational stiffness parameters describe the relative motion characteristics of the ribs and thoracic vertebrae in different directions, and are the key to simulate the torsion performance of the chest. The same method is used to establish 24 spherical hinges between T1 and left and right Rib1, T2 and left and right Rib2, and T12 and left and right Rib12.

[0085] Step S304, the established ligaments at the transverse costal joints (including the superior transverse costal ligament, the lateral transverse costal ligament, etc.) are combined to simulate the complex motion of the transverse costal joints. The introduction of the ligaments increases the biological fidelity of the model, and makes the joint response closer to the real situation.

[0086] Step S400, whole-person model assembly, specifically including:

[0087] Step S401, fill the space between adjacent ribs of the thoracic model with eight-node hexahedral elements to simulate the intercostal muscles. The intercostal muscles are important muscle tissue connecting adjacent ribs, which plays an important role in maintaining the stability and shape of the thoracic cavity. By simulating the intercostal muscles, the thoracic model can produce a more realistic motion response when subjected to external forces.

[0088] Step S402, establish a layer of shell elements on the inner and outer surfaces for contact setting, to ensure that the thoracic 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 thoracic cavity when subjected to external forces.

[0089] Step S403, connect the thoracic model upper and lower thoracic vertebrae to the intervertebral discs of the cervical and lumbar vertebrae through binding contact, respectively. Through binding contact, the relative position and motion relationship between the thoracic vertebrae and the cervical and lumbar vertebrae can be ensured to conform to the actual situation of human anatomy.

[0090] Step S404, define the automatic surface-to-surface contact between the thoracic cavity and internal organs using Contact_Automatic_Surface_To_Surface to simulate the interaction force between the thoracic cavity and internal organs, thereby more accurately predicting the damage to internal organs when the thoracic cavity is subjected to external forces.

[0091] Step S405, add all shell elements of the thoracic model to the automatic single surface contact of the whole human model, thereby ensuring the normal contact simulation of the thoracic model with the chest muscles, subcutaneous tissue and other structures. This ensures that the motion response of the thoracic model in the whole human model will not be disturbed by other parts, thereby more accurately predicting the motion response and damage of the thoracic cavity when subjected to external forces.

[0092] Step S406, appropriately establish some one-dimensional elements between the thoracic skeleton and surrounding muscles, soft tissues to strengthen the connection, build a whole human finite element model, in order to further enhance the stability and biological fidelity of the whole human model. By adding one-dimensional elements, the connection relationship between the thoracic skeleton and surrounding muscles, soft tissues can be simulated, thereby more accurately predicting the motion response and damage of the thoracic cavity when subjected to external forces.

[0093] Step S500, perform parameterized model optimization to finely adjust the parameters of the thoracic finite element model, to ensure that it can accurately reproduce the compression and torsion performance of the thoracic cavity under various collision conditions, refer to Figure 2 , specifically including:

[0094] Step S501, based on biomechanical data, the boundary conditions of frontal, lateral and oblique impact of the chest are extracted. These boundary conditions record the key information of the impact force, impact direction and action time of the chest in the actual impact event. Then, three groups of basic simulation models are established according to the boundary conditions by using the whole human finite element model constructed.

[0095] Step S502, in the simulation model, the three-direction rotational stiffness (S X , S Y , S Z ) of the ball hinge at the costovertebral joint, the Young's modulus (E TCJ ) of the ligament at the costovertebral joint and the Young's modulus (E RHJ ) of the ligament at the costocentral joint are taken as the optimization design variables to form a vector , as follows:

[0096]

[0097] The above parameters jointly determine the motion response characteristics of the chest when subjected to external force.

[0098] Step S503, the chest compression (CC) and the 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 vertebrae during the simulation process, and the chest deflection is defined by the angle change of the line connecting the sternum and the thoracic vertebrae after being subjected to the impact force.

[0099] Step S504, taking the error of the chest compression (CCk,test) and the deflection (CDk,test) of the simulation model under the three working conditions of frontal, lateral and oblique impact relative to the chest compression (CCk,PMHS) and the deflection (CDk,PMHS) of the biomechanical test as the optimization target, the objective function is established, as follows:

[0100]

[0101]

[0102] Wherein, represents the root mean square error of the compression amount, represents the root mean square error of the deflection, represents the working condition, refers to the frontal impact condition, refers to the lateral impact condition, refers to the oblique impact condition, is the design variable, refers to the working condition variable condition of the chest compression of the simulation model, the thoracic compression of the cadaver under the working condition, the thoracic compression of the cadaver under the working condition, the thoracic deflection of the cadaver under the working condition, the thoracic deflection of the cadaver under the working condition the thoracic deflection of the simulation model under the variable condition, the thoracic deflection of the cadaver under the working condition, the thoracic deflection of the cadaver under the working condition.

[0103] The multi-objective optimization problem is expressed as:

[0104]

[0105] wherein, is the design variable space, according to the actual situation, , , ,

[0106] The function comprehensively considers the errors under different working conditions, and adopts the root mean square error as the error measurement standard. In this embodiment, the ligament material parameters and the joint rotation stiffness parameters are set as the design variables, and the root mean square error between the thoracic compression and the torsion in the frontal collision, rear collision and side collision simulation tests and the response value in the biomechanical test is set as the optimization target.

[0107] In step S505, the simulation test is designed based on the orthogonal test matrix to ensure that the value range of the design variable can be as comprehensively covered as possible within a limited number of simulations. Through a large number of simulations, a large number of data points are collected, and an initial data set X is constructed. 0 At this time, the outer loop number i = 0.

[0108] Based on the training data set, a plurality of proxy models are established, including the response surface method, the radial basis function, the Gaussian process, etc. These proxy models can approximate the behavior of the simulation model with lower calculation cost, thereby greatly accelerating the optimization process. Through the verification data set, the proxy model is screened, and the proxy model with the highest fitting degree is selected for subsequent optimization.

[0109] In this embodiment, the number of inner loops of the optimization algorithm is set to 200 to ensure that the algorithm has enough iteration times to converge to the optimal solution. In each iteration, the algorithm will calculate the response of the proxy model according to the current design variable, and adjust the design variable through the optimization algorithm to minimize the objective function.

[0110] The optimal design variable and the theoretical response result are obtained, and the design variable is brought into the simulation model for calculation to extract the corresponding actual response result . It is checked whether the optimization process converges, if it converges, and the theoretical response result and If the relative error is less than 5%, then the parameters of the optimal chest finite element model are: If it does not converge, the number of iterations is i = i + 1, and the data points ( , Add to the dataset to form dataset X i Continue the previous steps iterating until the convergence condition is met.

[0111] Reference Figures 3 to 5 The diagram shows the structure of the digital model of the thoracic cavity of the present invention, including: 1-sternum, 2-thoracic vertebrae (201-T1 thoracic vertebra, 202-T2 thoracic vertebra, 203-T3 thoracic vertebra, 204-T4 thoracic vertebra, 205-T5 thoracic vertebra, 206-T6 thoracic vertebra, 207-T7 thoracic vertebra, 208-T8 thoracic vertebra, 209-T9 thoracic vertebra, 210-T10 thoracic vertebra, 211-T11 thoracic vertebra, 21...). 2-T12 thoracic vertebrae; 3-intervertebral disc nucleus pulposus; 4-intervertebral disc annulus fibrosus; 5-left ribs (501-left 1st rib, 502-left 2nd rib, 503-left 3rd rib, 504-left 4th rib, 505-left 5th rib, 506-left 6th rib, 507-left 7th rib, 508-left 8th rib, 509-left 9th rib, 510-left 10th rib, 511-left 11th rib, 512-left 12th rib); 6-left costal cartilage; 7-right ribs (701-right 1st rib, 702-right 2nd rib, 703-right 3rd rib, 704-right 4th rib, 705-right 5th rib, 706-right 6th rib, 707-right 7th rib, 708-right 8th rib). 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-costal cartilage on the right, 9-ligamentum flavum, 10-supraspinous ligament, 11-interspinous ligament, 12-posterior longitudinal ligament, 13-anterior longitudinal ligament, 14-intertransverse ligament, 15-radial ligament, 16-superior transverse ligament, 17-lateral transverse ligament.

[0112] Reference Figure 6 This diagram illustrates the measurement of thoracic cavity compression and torsion. Point T represents the thoracic vertebrae of the thoracic cavity model, point O represents the midpoint of the line connecting the sternum and thoracic vertebrae in the initial state of the thoracic cavity model, point C represents the point closest to the impact direction in the initial state of the thoracic cavity model, point O' represents the midpoint of the line connecting the sternum and thoracic vertebrae after the thoracic cavity model is subjected to impact force, and point C' represents the position of point C after the thoracic cavity model is subjected to impact force. The change in length of OC, i.e., OC-O'C', is the thoracic cavity compression, and the change in angle of OT, i.e., ∠OTO', is the thoracic cavity torsion.

[0113] The embodiment of the present disclosure further provides a storage medium, which stores a computer program. When the computer program is executed by a processor, all steps of the finite element model modeling method for reproducible thoracic cavity torsion performance can be realized.

[0114] Those skilled in the art can understand that all or part of the process of the finite element model modeling method for reproducible thoracic cavity torsion performance can be completed by a computer program instructing related hardware. The program can be stored in a non-volatile computer readable storage medium. When the program is executed, the process of each embodiment of the finite element model modeling method for reproducible thoracic cavity torsion performance can be included. Any reference to memory, storage, database or other medium used in each embodiment provided by the present application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), 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.

[0115] The embodiment of the present application further provides an electronic device, which comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the finite element model modeling method for reproducible thoracic cavity torsion performance are realized. In the embodiment of the present application, the processor is the control center of the computer system, which can be the processor of a physical machine or the processor of a virtual machine.

[0116] Reference Figure 7The electronic device 500 comprises 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 communication between the components, the communication interface 502 is used for signaling or data communication with other node devices, and the memory 503 stores machine readable instructions executable by the processor 501. When the electronic device 500 runs, the processor 501 communicates with the memory 503 through the bus 504, and the machine readable instructions are executed by the processor 501 to perform the steps of the above reproducible thoracic twist performance finite element model modeling method.

[0117] The above is only an embodiment of the present application, and the common knowledge of specific structures and characteristics in the scheme is not described in detail. The ordinary skilled person in the art knows all the ordinary technical knowledge in the field of the present application before the application date or the priority date, can know all the prior art in the field, and has the ability to apply conventional experimental means before that date. The ordinary skilled person in the art can improve and implement the present scheme based on their own ability under the guidance of the present application. Some typical known structures or known methods should not be an obstacle for the ordinary skilled person in the art to implement the present application. It should be noted that for those skilled in the art, without departing from the structure of the present application, a number of modifications and improvements can be made, which should be considered as the protection scope of the present application. The scope of protection of the present application should be subject to the content of its claims, and the specific embodiments in the specification can be used to explain the content of the claims.

Claims

1. A finite element model modeling method of reproducible thoracic torsion performance, characterized by, Comprise: Extract the geometric profile of the chest cavity from the recumbent tomographic image, the chest cavity structure includes the sternum, thoracic vertebrae and rib structure, correct the kyphosis angle of the thoracic vertebrae based on the standing X-ray computed tomography image, and reconstruct the three-dimensional geometric model of the chest cavity; Establish a chest cavity finite element model by meshing and material attribute definition; Establish a spherical hinge between the transverse process of the thoracic vertebrae and the head of the rib; Assemble the chest cavity finite element model into the whole human finite element model; Perform parameterized model optimization; Perform parameterized model optimization, including the following: Extract the boundary conditions of the chest in frontal impact, side impact and oblique impact; Use the established whole human finite element model to establish three corresponding basic simulation models according to the boundary conditions; In the simulation model, the rotational stiffness S X , S Y , S Z of the spherical hinge in three directions at the costovertebral joint, the Young's modulus E TCJ of the costovertebral ligament, and the Young's modulus E RHJ of the costotransverse ligament are taken as the optimization design variables, constituting a vector , as shown in the following formula: The above parameters jointly determine the motion response characteristics of the chest cavity when subjected to external force; Perform parameterized model optimization, including the following: Define the chest compression CC and deflection CD as response indicators; Take the error of the chest compression CCk,test and deflection CDk,test of the simulation model under the three working conditions of frontal impact, side impact and oblique impact relative to the biomechanical test chest compression CCk,PMHS and deflection CDk,PMHS as the optimization target, and establish the objective function as follows: wherein, a root mean square error of the compression amount, a root mean square error of the deflection amount, a working condition, a frontal crash working condition, a side crash working condition, an oblique crash working condition, a design variable, a chest compression amount of the simulation model under the working condition a chest compression amount of the simulation model under the variable condition, a chest compression amount of the cadaver under the working condition a chest deflection amount of the simulation model under the variable condition, a chest deflection amount of the simulation model under the variable condition, Express the multi-objective optimization problem as: wherein is the design variable space; Perform parameterized model optimization, also including the following: Based on the orthogonal test matrix design simulation test, through a large number of simulation, collected a wealth of data points, and constructed the initial data set X 0 At this time the outer loop i = 0; Based on the training data set, a variety of surrogate models are established, including response surface method, radial basis function and Gaussian process; Through the verification data set, the surrogate model is screened, and the surrogate model with the highest fitting degree is selected for subsequent optimization; Solving the optimal design variables and the theoretical response results , and bring this design variable into the simulation model for calculation, extract the corresponding actual response results ; check if this optimization process converges, if it converges, and the relative error of the theoretical response results and is less than 5%, then the parameters of the optimal chest finite element model are , if it does not converge, the number of cycles is i=i+1, the data points ( , ) are added to the data set to form the data set X i , continue the previous steps for iteration until the convergence condition is met.

2. The finite element modeling method of reproducible chest twist performance according to claim 1, wherein, Correct the kyphosis angle of the thoracic vertebrae based on the standing X-ray computed tomography image, including the following: The thoracic vertebrae include T1 to T12. An angle between a plane of an upper endplate of a T1 thoracic vertebra and a plane of a lower endplate of a T12 thoracic vertebra in the initial geometric model is measured to obtain a kyphosis angle of the thoracic vertebrae A kyphosis angle of a target thoracic vertebra is measured based on a standing position X-ray computed tomography image An adjustment amount of the kyphosis angle is averaged to each thoracic vertebra. A calculation formula of the adjustment amount of the kyphosis angle of adjacent thoracic vertebrae is as follows, wherein is and the adjustment amount of the two adjacent thoracic kyphosis angles, is the thoracic kyphosis angle of the upper endplate of the T1 thoracic vertebra and the lower endplate of the T12 thoracic vertebra in the geometric model, is the thoracic kyphosis angle of the upper endplate of the T1 thoracic vertebra and the lower endplate of the T12 thoracic vertebra in the X-ray computed tomography image (X-ray), is the jth thoracic vertebra counted from the top, and is the upper thoracic vertebra among the adjacent thoracic vertebrae, is the lower thoracic vertebra among the adjacent thoracic vertebrae.

3. The method of claim 2, wherein, Take the thoracic vertebrae of T6 or T7 as the reference immobile, and gradually rotate the other thoracic vertebrae to the two ends, so that the kyphosis angle of each thoracic vertebrae is adjusted according to the adjustment amount; Smooth the adjusted geometric surface and perform symmetry processing, smooth processing is achieved by fitting curve or surface, and symmetry processing adjusts the ribs and thoracic vertebrae on the left and right sides according to the symmetry of the human body.

4. The method of claim 1, wherein, Meshing, including the following: The internal cancellous bone of the sternum and ribs is simulated by eight-node hexahedral elements, the internal cancellous bone of the thoracic vertebrae is simulated by four-node tetrahedral elements, the cortical bone on the surface of the sternum, thoracic vertebrae and ribs is simulated by shell elements, and the cortical bone and cancellous bone are connected by shared nodes; Two layers of eight-node hexahedral elements are established between adjacent thoracic vertebrae to simulate intervertebral discs, 50% to 60% of the internal area of the intervertebral disc is used as the nucleus pulposus, and the remaining external area is used as the annulus fibrosus; A layer of empty shell elements is established on the outer surface of the annulus fibrosus for contact setting; Diagonal beam elements are established to simulate the direction of the fibers in the annulus fibrosus; The costal cartilage between the sternum and the ribs is simulated by 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 ligament, costal head joint ligament and costal transverse process joint ligament are all simulated by four-node shell elements.

5. The finite element modeling method of claim 1 or 4, wherein, Material attribute definition, including the following: Spongy bone and costal cartilage impart a viscoelastic-plastic material that combines continuous damage mechanics, cortical bone imparts an isotropic elastic-plastic material, intervertebral discs impart a highly compressible foam material, costal cartilage membranes impart an empty material, and ligaments impart a fabric material.

6. The finite element modeling method of reproducible thoracic twist performance according to claim 1, wherein, Establishing a spherical hinge between the transverse processes of the thoracic vertebrae and the costal head, comprising the following: The local shell elements of the thoracic transverse process and the left and right rib head are converted into rigid bodies; a node is established at the center of the line segment connecting the center of the rib head joint and the center of the transverse process joint, and the 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 of three directions is defined X , Y , Z .

7. The method of claim 4, wherein, Assembling the thoracic model into the whole body model, comprising the following: Filling the space between adjacent ribs of the thoracic model with eight-node hexahedral elements to simulate the intercostal muscles; establishing a layer of shell elements on the inner and outer surfaces for contact settings; connecting the upper and lower thoracic discs of the thoracic model to the intervertebral discs of the cervical and lumbar vertebrae, respectively, through binding contacts; defining the automatic surface-to-surface contact between the thoracic model and the internal organs; adding all the shell elements of the thoracic model to the automatic single-surface contact of the whole body model; adding all the shell elements of the thoracic model to the automatic single-surface contact of the whole body model; establishing a one-dimensional element between the thoracic bones and the surrounding muscles and soft tissues to simulate the connection between the thoracic bones and the surrounding muscles and soft tissues.

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