阅读说明：本技术 一种用于车辆碰撞评估的夹层玻璃有限元建模方法 (Laminated glass finite element modeling method for vehicle collision assessment ) 是由 王振 陈瑜 周星栋 龚益玲 郑宁昆 李月 杨秋雨 于 2021-06-21 设计创作，主要内容包括：本发明公开了一种用于车辆碰撞评估的夹层玻璃有限元建模方法,其步骤包括：使用壳单元建立外层界面、内层界面的有限元模型,并均赋以无属性空材料,对厚度定义；使用薄膜单元建立玻璃胶层有限元模型,将其厚度定义为参数,并赋以粘弹性材料；使用壳单元建立外层玻璃、内层玻璃的有限元模型,并均赋以玻璃材料,对厚度定义；建立撞击中心点的应变能密度的有限元失效模型,并定义延迟断裂算法,将临界应变能密度Ec和撞击中心点到玻璃边界的最小距离d定义为参数；当夹层玻璃壳单元最大主应力超过断裂应力σ时,激活延迟断裂算法；当延迟断裂算法获得的平均应变能密度超过临界应变能密度Ec时,夹层玻璃壳单元发生失效。(The invention discloses a sandwich glass finite element modeling method for vehicle collision assessment, which comprises the following steps: establishing a finite element model of an outer layer interface and an inner layer interface by using a shell unit, assigning a non-attribute hollow material to each of the finite element models, and defining the thickness; establishing a finite element model of the glass glue layer by using the film unit, defining the thickness of the finite element model as a parameter, and endowing the finite element model with a viscoelastic material; establishing finite element models of outer layer glass and inner layer glass by using a shell unit, assigning glass materials to the models and defining the thickness of the models; establishing a finite element failure model of the strain energy density of the impact central point, defining a delayed fracture algorithm, and defining a critical strain energy density Ec and a minimum distance d from the impact central point to a glass boundary as parameters; activating a delayed fracture algorithm when the maximum principal stress of the laminated glass shell unit exceeds the fracture stress sigma; when the mean strain energy density obtained by the delayed fracture algorithm exceeds the critical strain energy density Ec, the laminated glass cover cell fails.)

1. A laminated glass finite element modeling method for vehicle crash assessment, comprising the steps of:

establishing an outer layer interface finite element model by using a shell unit, defining the thickness of the outer layer interface finite element model as a parameter, and assigning a non-attribute hollow material;

establishing an outer layer glass finite element model by using a shell unit, defining the thickness of the outer layer glass finite element model as a parameter, and assigning a glass material;

establishing a finite element model of the glass glue layer by using the film unit, defining the thickness of the finite element model as a parameter, and endowing the finite element model with a viscoelastic material;

establishing an inner layer glass finite element model by using a shell unit, defining the thickness of the inner layer glass finite element model as a parameter, and assigning a glass material;

establishing an inner layer interface finite element model by using a shell unit, defining the thickness of the inner layer interface finite element model as a parameter, and assigning a non-attribute hollow material;

establishing a finite element failure model of the strain energy density of the impact central point, and defining a delayed fracture algorithm, wherein the critical strain energy density Ec is defined as a parameter, and the minimum distance d from the impact central point to the glass boundary is defined as a parameter;

activating a delayed fracture algorithm when the maximum principal stress of the laminated glass shell unit exceeds the fracture stress sigma;

when the mean strain energy density calculated by the delayed fracture algorithm exceeds the critical strain energy density Ec, the laminated glass cover cell fails.

2. The laminated glass finite element modeling method of claim 1, wherein the outer layer interface finite element model and the outer layer glass finite element model are connected in a common node manner.

3. The laminated glass finite element modeling method of claim 1, wherein the inner layer interface finite element model and the inner layer glass finite element model are connected in a common node manner.

4. The laminated glass finite element modeling method of claim 1, wherein the outer layer glass finite element model and the glass cement layer finite element model and the inner layer glass finite element model and the glass cement layer finite element model are flexibly connected.

5. The laminated glass finite element modeling method of claim 1, wherein the outer layer glass finite element model and the glass cement layer finite element model and the inner layer glass finite element model and the glass cement layer finite element model are connected by a three-dimensional glue unit.

6. The laminated glass finite element modeling method of claim 1, wherein the delayed fracture algorithm comprises: the average strain energy density E of the laminated glass shell element within a region of radius R centered on the center point of impact is calculated.

7. The laminated glass finite element modeling method of claim 1, wherein the fracture stress σ is a set constant value, and the value range of the fracture stress σ is 0.01-0.1 GPa.

8. A laminated glass finite element modeling method as claimed in claim 1, characterized in that the breaking stress σ is a curve relating to strain rate.

9. A finite element modeling method for laminated glass as defined in claim 6, wherein R ranges from 180 mm to 240 mm.

10. The laminated glass finite element modeling method of claim 1, wherein the critical strain energy density Ec and the minimum distance d from the impact center point to the glass boundary satisfy the following relationship:

when d is more than or equal to 0mm and less than 32mm, Ec is 0.1J/mm;

when d is more than or equal to 32mm and less than 100mm, Ec is d/100 multiplied by 0.32J/mm;

when d is more than or equal to 100mm<At 210mm, Ec is 0.0187 × e^(0.0284×d)J/mm

When d is more than or equal to 210mm, Ec is 7.3J/mm.

Technical Field

The invention relates to a finite element modeling method, in particular to a finite element modeling method for laminated glass.

Background

In recent years, with the modification of the draft of the new pedestrian protection regulations, the protection range of the windshield glass is increased in the regulations, and the 2023CNCAP and cissi 2.0 regulations consider a larger evaluation range of the windshield glass, so that the importance degree of the pedestrian safety protection is gradually increased for each automobile manufacturer.

In general, a front windshield of a vehicle is generally manufactured by using laminated glass, which is a novel composite structure formed by laminating two or more layers of flat glass with one or more layers of transparent high molecular polymer adhesive layers such as PVB interposed therebetween, and when severe impact load is applied, even if the glass is broken, fragments are adhered to the intermediate adhesive layer and do not splash, thereby ensuring the safety of passengers.

In the collision simulation calculation of the automobile pedestrian protection regulation, the traditional modeling method generally uses 3 layers of shell units to establish a front windshield glass model, and simulates the failure of the glass by defining the unit elimination under critical strain, but because of the PVB glue layer in the middle of the front windshield glass, the unit does not disappear even after the glass reaches the failure condition, and a certain supporting force is still applied to the head part which is collided.

Therefore, in the conventional technique, it is difficult to obtain the actual conditions of the crack generation at the time of breakage of the glass panel and the elastic damage (tensor) at the time of breakage by simply simulating the windshield glass by the cell deletion method. In order to more accurately simulate the performance of laminated glass when the laminated glass is impacted by high speed and the acting force on the head of a pedestrian and obtain a more accurate and reliable simulation result, a high-precision model of the front windshield glass of a vehicle needs to be obtained to assist in simulation detection.

Based on the method, the laminated glass finite element modeling method for vehicle collision assessment is expected to be obtained, and the physical properties of the laminated glass in high-speed collision can be accurately simulated by adopting the laminated glass finite element modeling method, so that the operation precision of a model can be greatly improved, and the evaluation of a vehicle in a simulation result is more accurate and reliable.

Disclosure of Invention

The invention aims to provide a laminated glass finite element modeling method for vehicle collision assessment, which can accurately simulate the physical properties of laminated glass in high-speed collision, thereby greatly improving the operation precision of a model and ensuring that the evaluation of a vehicle in a simulation result is more accurate and reliable.

In addition, the sandwich glass finite element modeling method is very favorable for saving the cost of a sample car, can greatly improve the research and development efficiency of the car, and has good popularization and application prospects.

In order to achieve the above object, the present invention proposes a laminated glass finite element modeling method for vehicle collision assessment, which includes the steps of:

establishing an outer layer interface finite element model by using a shell unit, defining the thickness of the outer layer interface finite element model as a parameter, and assigning a non-attribute hollow material;

establishing an outer layer glass finite element model by using a shell unit, defining the thickness of the outer layer glass finite element model as a parameter, and assigning a glass material;

establishing a finite element model of the glass glue layer by using the film unit, defining the thickness of the finite element model as a parameter, and endowing the finite element model with a viscoelastic material;

establishing an inner layer glass finite element model by using a shell unit, defining the thickness of the inner layer glass finite element model as a parameter, and assigning a glass material;

establishing an inner layer interface finite element model by using a shell unit, defining the thickness of the inner layer interface finite element model as a parameter, and assigning a non-attribute hollow material;

establishing a finite element failure model of the strain energy density of the impact central point, and defining a delayed fracture algorithm, wherein the critical strain energy density Ec is defined as a parameter, and the minimum distance d from the impact central point to the glass boundary is defined as a parameter;

activating a delayed fracture algorithm when the maximum principal stress of the laminated glass shell unit exceeds the fracture stress sigma;

when the mean strain energy density calculated by the delayed fracture algorithm exceeds the critical strain energy density Ec, the laminated glass cover cell fails.

Further, in the finite element modeling method of laminated glass of the present invention, the outer layer interface finite element model and the outer layer glass finite element model are connected in a common node manner.

Further, in the laminated glass finite element modeling method of the present invention, the inner layer interface finite element model and the inner layer glass finite element model are connected in a common node manner.

Further, in the laminated glass finite element modeling method of the present invention, the outer layer glass finite element model and the glass cement layer finite element model, and the inner layer glass finite element model and the glass cement layer finite element model are flexibly connected.

Further, in the method for modeling a finite element of laminated glass of the present invention, the outer layer glass finite element model and the glass cement layer finite element model, and the inner layer glass finite element model and the glass cement layer finite element model are connected by a three-dimensional glue unit.

Further, in the finite element modeling method of laminated glass according to the present invention, the delayed fracture algorithm includes: the average strain energy density E of the laminated glass shell element within a region of radius R centered on the center point of impact is calculated.

Further, in the finite element modeling method of the laminated glass, the fracture stress sigma is a set constant value, and the value range of the fracture stress sigma is 0.01-0.1 GPa.

Further, in the finite element modeling method of laminated glass according to the present invention, the breaking stress σ is a curve relating to a strain rate.

Further, in the finite element modeling method of the laminated glass, the value range of R is 180-240 mm.

Further, in the finite element modeling method of laminated glass according to the present invention, the critical strain energy density Ec and the minimum distance d from the impact center point to the glass boundary satisfy the following relationship:

when d is more than or equal to 0mm and less than 32mm, Ec is 0.1J/mm;

when d is more than or equal to 32mm and less than 100mm, Ec is d/100 multiplied by 0.32J/mm;

when d is more than or equal to 100mm<At 210mm, Ec is 0.0187 × e^(0.0284×d)J/mm；

When d is more than or equal to 210mm, Ec is 7.3J/mm.

Compared with the prior art, the finite element modeling method of the laminated glass for vehicle collision assessment has the following advantages and beneficial effects:

according to the sandwich glass finite element modeling method for vehicle collision assessment, the accuracy of head collision assessment of a vehicle windshield area can be greatly improved through the sandwich glass finite element modeling method, the actual conditions of generation of cracks and elastic damage during breakage of a glass panel are obtained, after the windshield reaches a failure condition, unit disappearance cannot occur immediately, and a certain supporting force is still provided for a collided head, so that the collision response of the constructed sandwich glass collision model is highly consistent with that of a physical model, and the calculation accuracy of the whole vehicle under the pedestrian protection head collision working condition is greatly optimized.

In some preferred embodiments, compared with the traditional finite element modeling method, the sandwich glass finite element modeling method provided by the invention can be used for more accurately obtaining the head injury peak value and the peak occurrence time, and can improve the efficiency and accuracy of finite element calculation of autonomous research and development of vehicles.

In addition, the sandwich glass finite element modeling method for vehicle collision assessment can be suitable for different pedestrian protection laws and regulations, can effectively save the cost of a sample vehicle, can greatly improve the research and development efficiency of the vehicle, and has good popularization and application prospects.

Drawings

Fig. 1 schematically shows a physical model of a laminated glass for collision use according to the present invention.

FIG. 2 schematically shows the inner and outer layer element structures of a laminated glass according to an embodiment of the finite element modeling method of a laminated glass according to the present invention.

FIG. 3 schematically illustrates a flow chart of a laminated glass finite element modeling method according to an embodiment of the present invention.

Fig. 4 schematically shows a comparison of the HIC values for collision damage obtained based on the finite element modeling method for laminated glass according to the present invention, the HIC values for collision damage obtained by the conventional modeling method, and the HIC values obtained by the physical collision test.

Detailed Description

The method for finite element modeling of laminated glass for vehicle crash evaluation according to the present invention will be further explained and illustrated with reference to the drawings and the specific examples, which, however, should not be construed as unduly limiting the technical solution of the present invention.

Fig. 1 schematically shows a physical model of a laminated glass for collision use according to the present invention.

As shown in fig. 1, in the present invention, the laminated glass for crash use according to the present invention may include: an upper toughened glass layer 1, a lower toughened glass layer 2 and a glass glue layer 3. Wherein, the thickness of the upper tempered glass layer 1 can be set as a; the thickness of the lower tempered glass layer may be set to c; the thickness of the glass cement layer may be set to b.

FIG. 2 schematically shows the inner and outer layer element structures of a laminated glass according to an embodiment of the finite element modeling method of a laminated glass according to the present invention.

FIG. 3 schematically illustrates a flow chart of a laminated glass finite element modeling method according to an embodiment of the present invention.

As shown in fig. 2 and 3, in the present embodiment, the finite element modeling of the laminated glass according to the present invention can be performed by the following steps:

s1: and importing the three-dimensional CAD model of the automobile front windshield glass into finite element software, and geometrically cleaning the three-dimensional model of the front windshield glass.

It should be noted that, in the above step S1, the structure of the front windshield may refer to the physical model of the laminated glass shown in fig. 1, and both structures are the same, and the front windshield may also include: the glass-reinforced plastic composite material comprises an upper toughened glass layer 1 with the thickness of a, a lower toughened glass layer 2 with the thickness of c and a glass glue layer 3 with the thickness of b.

S2: establishing a finite element model of the automobile front windshield glass in the finite element preprocessing software, wherein the finite element model can comprise the following operations:

extracting a neutral plane of an upper toughened glass layer 1 in the front windshield glass, establishing an outer layer interface 4 finite element model by using a shell unit, defining the thickness of the outer layer interface as a parameter t1, and assigning a non-attribute hollow material, wherein t1 is 0.1 mm;

extracting a neutral plane of an upper toughened glass layer 1 in the front windshield glass, establishing a finite element model of an outer layer glass 5 by using a shell unit, defining the thickness of the outer layer glass as a parameter t2, and assigning a glass material, wherein t2 is a;

extracting a neutral plane of a glass adhesive layer 3 in the front windshield glass, establishing a finite element model of the glass adhesive layer 6 by using a film unit, defining the thickness of the finite element model as a parameter t3, and assigning a viscoelastic material, wherein t3 is b;

extracting a neutral plane of a lower toughened glass layer 2 in the front windshield glass, establishing a finite element model of the inner layer glass 7 by using a shell unit, defining the thickness of the inner layer glass as a parameter t4, and assigning a glass material, wherein t4 is c;

extracting a neutral plane of a lower toughened glass layer 2 in the front windshield, establishing an inner layer interface 8 finite element model by using a shell unit, defining the thickness of the inner layer interface as a parameter t5, and assigning a non-attribute hollow material, wherein t5 is 0.1 mm;

defining a connection mode between layers of a finite element model of the automobile front windshield glass, and connecting the finite element model of the outer interface 4 and the finite element model of the outer glass 5 in a mode of common nodes; the inner layer glass 7 finite element model and the inner layer interface 8 finite element model are connected in a mode of common nodes.

In the invention, the outer layer glass 5 finite element model and the glass glue layer 6 finite element model as well as the inner layer glass 7 finite element model and the glass glue layer 6 finite element model can be flexibly connected; of course, in certain other embodiments, they may also be connected by a three-dimensional glue unit.

It should be noted that in other embodiments, it may be preferable to control the finite element meshes of the finite element model of the outer layer glass 5, the finite element model of the glass cement layer 6 and the finite element model of the inner layer glass 7 to be in one-to-one correspondence.

In order to achieve the purpose, the outer layer glass 5 finite element model can be biased through a grid biasing function to establish a glass glue layer 6 finite element model, the biasing distance can be controlled to be a/2+ b/2, the thickness of the glass glue layer 6 finite element model is defined to be t3, and the glass glue layer 6 finite element model is endowed with a nonlinear viscoelastic film material, wherein t3 is b; correspondingly, through the grid offset function, the finite element model of the outer layer glass 5 can be offset to establish a finite element model of the inner layer glass 7, the offset distance can be controlled to be a/2+ b + c/2, the thickness of the finite element model of the inner layer glass 7 is defined as t4, and the finite element model is endowed with a glass material, wherein t4 is c.

S3: establishing a finite element failure model of the strain energy density of the impact center points C1, C2, … Cn, defining a non-local averaging option, specifying a spatial averaging process of the cell internal energy, wherein the average strain energy density E of the laminated glass envelope cell can be represented by the following formula:

in the above formula (1), W is a single groupElementary strain energy, V denotes the cell volume, σ_ijIs unit stress,. epsilon_ijIs unit strain, d ε_ijIs the increase in cell strain.

S4: because the front windshield glass boundary is fixed on the vehicle body structure through glue, the unit close to the front windshield glass boundary has higher cracking risk than other units at the moment of high-speed impact; thus, it can be defined that the critical strain energy density Ec of the impact center points C1, C2, … Cn and the minimum distance d of the impact center points C1, C2, … Cn to the glass boundary satisfy the following relationship:

when d is more than or equal to 0mm and less than 32mm, Ec is 0.1J/mm;

when d is more than or equal to 32mm and less than 100mm, Ec is d/100 multiplied by 0.32J/mm;

when d is more than or equal to 100mm<At 210mm, Ec is 0.0187 × e^(0.0284×d)J/mm；

When d is more than or equal to 210mm, Ec is 7.3J/mm.

S5: defining the impact center point C1, C2, … Cn delayed fracture algorithm: the average strain energy density E of the laminated glass shell element within a region of radius R centered at the impact point C1, C2, … Cn was calculated. Activating a delayed fracture algorithm when the maximum principal stress of the laminated glass shell unit exceeds the fracture stress sigma; when the mean strain energy density E calculated by the delayed fracture algorithm exceeds the critical strain energy density Ec, the laminated glass cover cell fails.

In the present embodiment, the radius R has a value range of 180 to 240 mm; the fracture stress sigma is a set constant value, and the value range of the fracture stress sigma can be controlled to be 0.01-0.1 GPa.

S6: the method comprises the steps of establishing a collision model for pedestrian protection collision of an automobile, wherein the collision model comprises a front windshield three-dimensional finite element model established by the sandwich glass finite element modeling method, an automobile body three-dimensional finite element model, an engine front cover finite element model and an instrument desk finite element model.

S7: the assembly model used for protecting the pedestrian of the automobile from collision is defined, the connection between each component and the automobile body is defined, the assembly model comprises a front windshield glass and the automobile body which are connected through a glue unit, an engine front cover and the automobile body are connected through a spherical hinge unit, and an instrument desk and the automobile body are connected through a bolt.

S8: the method comprises the following steps of establishing constraint and loading of an automobile pedestrian protection collision model, wherein the constraint and loading comprises the following steps: defining the impact point position of the impact head model, defining the boundary fixing constraint of the automobile body and defining the internal contact among all parts.

Therefore, the finite element modeling method can greatly improve the accuracy of the head collision simulation of the vehicle windshield glass area, and can greatly improve the defect that the surface damage of the glass, the crack or the elastic damage during the fracture are difficult to accurately reflect when the failure simulation is carried out by using a unit deletion method in the prior art.

The finite element modeling method of the laminated glass can greatly improve the accuracy of head collision assessment of a vehicle windshield area, and obtain the real conditions of crack generation when a glass panel is damaged and elastic damage when the glass panel is broken. Compared with the traditional finite element modeling method, the finite element modeling method for the laminated glass can obviously improve the efficiency and the accuracy of finite element calculation of autonomous research and development of vehicles.

FIG. 4 schematically shows a comparison of impact injury HIC values obtained for a crash head using a finite element modeling method of laminated glass according to the present invention in one embodiment, impact injury HIC values obtained for a crash head using a conventional modeling method, and impact injury HIC values obtained for a physical crash test.

Curve a in fig. 4 represents the crash damage HIC (head damage index) curve obtained using the finite element modeling method for laminated glass according to the present invention; the curve B represents an HIC curve obtained by a physical collision test; the C-curve represents the crash damage HIC-curve obtained using the conventional modeling method described in the background of the present application.

The collision damage HIC can be obtained by the following formula (2), which is a dimensionless number:

in the above formula (2), g represents the gravitational acceleration, a represents the resultant acceleration of the center of mass of the head during the collision, and t2-t1 represents the time interval during which the HIC reaches the maximum value, wherein the maximum interval may be controlled to be 15 ms.

As can be seen from fig. 4, the head injury HIC curve obtained by fitting the finite element modeling method for laminated glass according to the present invention can significantly improve the head injury peak value and the peak value occurrence time, greatly improve the accuracy of pedestrian head protection collision simulation, and can be applied to different pedestrian protection regulations, which is very beneficial to saving the cost of a sample car, so that the head collision model can more accurately and effectively give a simulation prediction in the working condition of the whole car, shorten the period of experimental verification, greatly save the cost of the whole car experiment, improve the car research and development efficiency, and have good popularization and application prospects.

It should be noted that the combination of the features in the present application is not limited to the combination described in the claims of the present application or the combination described in the embodiments, and all the features described in the present application may be freely combined or combined in any manner unless contradicted by each other.

It should also be noted that the above-mentioned embodiments are only specific embodiments of the present invention. It is apparent that the present invention is not limited to the above embodiments and similar changes or modifications can be easily made by those skilled in the art from the disclosure of the present invention and shall fall within the scope of the present invention.