Small deformation contact nonlinear simulation method

Abstract

The invention discloses a small-deformation contact nonlinear simulation method, which belongs to the technical field of contact nonlinear simulation, and comprises the following steps: S1, carrying out contact simulation at a contact interface by adopting a friction spring; s2, setting a nonlinear analysis working condition in finite element analysis software; and S3, performing small deformation contact nonlinear simulation and calculation on the structure. According to the small-deformation contact nonlinear simulation method, important references are provided for accurate calculation and design, material saving, energy consumption reduction, production efficiency improvement and the like of structures such as modular units and beams, laying of tunnel linings and the like, the application mode of the small-deformation contact nonlinear simulation method can be embedded into a program to form automatic options, and digital twinning is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of contact non - linear simulation, and in particular to a small - deformation contact non - linear simulation method. Background Art

[0002] In the prior art, when a beam is placed on the ground, and when pre - fabricated component units such as tunnel linings and disassembled modular box - type houses are assembled and spliced, they are all connections between different interfaces, and there is a possibility of disconnection and sliding between the contact interfaces. In finite - element simulation, hinge joints or rigid joints are often used to handle such boundary conditions, such as the contact simulation between a structure and the ground, the connection simulation between linings, and the contact simulation between modular units. In traditional contact simulation, contact relationships are often established between the nodes on the structural surface and the projection points of these nodes on the corresponding contact interfaces. As the contact disconnects and slips, the points on the structural surface need to find corresponding nodes on the corresponding contact interfaces one by one. When contact disconnects or slips, the points on the structural surface need to re - establish contact relationships with the points 1 - 7 on the corresponding contact interfaces in sequence, as Figure 15 shown, resulting in a large amount of calculation, and requiring that the mesh division of the corresponding contact interface should be relatively dense, otherwise there will be a situation where the points on the structural surface do not correspond to the corresponding contact interface; the corresponding contact interface needs to be continuous. However, the actual working condition of the interface connection is between hinged and rigid, which is a semi - rigid effect, resulting in the calculation results not conforming to the actual situation, affecting the calculation accuracy, causing a large gap between the designed performance of the structure and the actual service condition, resulting in waste of materials or potential safety hazards. Therefore, it is necessary to simulate the real boundary conditions of the structure and then accurately evaluate the mechanical properties of the structure. Summary of the Invention

[0003] The object of the present invention is to provide a small - deformation contact non - linear simulation method, which provides an important reference for the accurate calculation and design, material saving, energy consumption reduction, production efficiency improvement, etc. of structures such as modular units, beam placement, and tunnel linings. Its application method can be embedded in a program to form an automated option to achieve digital twin.

[0004] To achieve the above object, the present invention provides a small - deformation contact non - linear simulation method, including the following steps: S1. Use friction springs for contact simulation at the contact interface; S2. Set non - linear analysis conditions in finite - element analysis software; S3. Conduct small - deformation contact non - linear simulation and calculation on the structure.

[0005] Preferably, in S1, friction springs are used for simulation, and the normal direction of the contact interface is allowed to disconnect, and the tangential direction is allowed to slide.

[0006] Preferably, the normal setting of the contact interface in S1 includes the following three cases: the structure contacts the ground; structures contact each other; the normal of the contact interface disengages.

[0007] Preferably, when the structure contacts the ground, the normal stiffness of the contact interface takes the vertical stiffness of the spring per unit area as 10 6 kN / mm / m 2 ; when structures contact each other, the normal stiffness of the contact interface is considered according to the elastic modulus of the material and the measured value; when the normal of the contact interface disengages, the normal stiffness is reduced according to the structure material and the measured value. After the contact interface starts to disengage, the normal stiffness of the contact interface takes the reduced stiffness.

[0008] Preferably, the tangential setting of the contact interface in S1 includes: when the structure contacts the ground and when structures contact each other, the tangential stiffness between the contact interfaces is small, and the value needs to be determined according to the friction coefficient and the measured value; when the contact interface slides tangentially, the tangential stiffness decreases, and the tangential stiffness is reduced according to the structure material and the measured value. After the contact interface starts to slide, the tangential stiffness of the contact interface takes the reduced stiffness.

[0009] Preferably, in S2, since the contact interface allows disengagement and sliding, nonlinear analysis needs to be considered. Since the deformation at the contact interface is small deformation, the stiffness of the structure cannot be reformed according to the deformation of the structure, that is, geometric nonlinearity is not considered.

[0010] Therefore, the present invention adopts the above-mentioned small deformation contact nonlinear simulation method, which provides an important reference for the accurate calculation and design of structures such as modular units, beam supports, and tunnel linings, saving materials, reducing energy consumption, and improving production efficiency. Its application method can be embedded in the program to form an automatic option to achieve digital twin.

[0011] Next, through the drawings and embodiments, the technical solutions of the present invention will be further described in detail. Description of the Drawings

[0012] Figure 1 is a model diagram of an I-beam of a small deformation contact nonlinear simulation method of the present invention; Figure 2 is a model diagram of the connection unit of Damper-Friction Spring at the contact position between the I-beam and the support of a small deformation contact nonlinear simulation method of the present invention; Figure 3 is a deformation model diagram of the contact position between the I-beam and the support of a small deformation contact nonlinear simulation method of the present invention; Figure 4 is the axial force diagram of the connection unit when geometric nonlinearity is not considered in a small deformation contact nonlinear simulation method of the present invention; Figure 5It is the axial force diagram of the connecting unit when considering large deformations in a small deformation contact nonlinear simulation method of the present invention; Figure 6 It is the axial force diagram of the connecting unit when using the Damper-Friction Spring connecting unit in a small deformation contact nonlinear simulation method of the present invention; Figure 7 It is the axial force diagram of the connecting unit when using a linear connecting unit in a small deformation contact nonlinear simulation method of the present invention; Figure 8 It is the reaction force diagram of the support when using a fixed support in a small deformation contact nonlinear simulation method of the present invention; Figure 9 It is the deformation diagram when using the Damper-Friction Spring connecting unit in a small deformation contact nonlinear simulation method of the present invention; Figure 10 It is the deformation diagram when using a linear connecting unit in a small deformation contact nonlinear simulation method of the present invention; Figure 11 It is the deformation diagram when using a fixed support in a small deformation contact nonlinear simulation method of the present invention; Figure 12 It is the stress diagram when using the Damper-Friction Spring connecting unit in a small deformation contact nonlinear simulation method of the present invention; Figure 13 It is the stress diagram when using a linear connecting unit in a small deformation contact nonlinear simulation method of the present invention; Figure 14 It is the stress diagram when using a fixed support in a small deformation contact nonlinear simulation method of the present invention; Figure 15 It is the diagram of the traditional contact simulation method in a small deformation contact nonlinear simulation method of the present invention. Detailed implementation manners

[0013] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0014] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs.

[0015] Embodiment 1 The present invention provides a small deformation contact nonlinear simulation method, including the following steps: S1. Use a friction spring to perform contact simulation at the contact interface; The simulation is carried out using a friction spring. The normal direction of the contact interface is allowed to separate, and the tangential direction is allowed to slide. The initial displacement is set as a non-linear condition to simulate the non-linear contact of small deformations.

[0016] The normal direction settings of the contact interface include the following three cases: the structure contacts the ground; the structures contact each other; the normal direction of the contact interface separates.

[0017] When the structure contacts the ground, the normal stiffness of the contact interface is very large. It is recommended to take the vertical stiffness of the spring per unit area as 10 6 kN / mm / m 2 , and the theoretical effect can be achieved. When the structures contact each other, the normal stiffness of the contact interface is relatively small, and the value is considered according to the elastic modulus of the material and the measured value. Since the normal direction of the contact interface can separate, the normal stiffness will inevitably decrease after separation. When the normal direction of the contact interface separates, the normal stiffness needs to be reduced according to the structure material and the measured value. After the contact interface starts to separate, the normal stiffness of the contact interface takes the reduced stiffness.

[0018] The tangential settings of the contact interface include: when the structure contacts the ground and when the structures contact each other, the tangential stiffness between the contact interfaces is relatively small, and the value needs to be determined according to the friction coefficient and the measured value; since the tangential direction of the contact interface is allowed to slide, the tangential stiffness will inevitably decrease after sliding. When the contact interface slides tangentially, the tangential stiffness decreases, and the tangential stiffness is reduced according to the structure material and the measured value. After the contact interface starts to slide, the tangential stiffness of the contact interface takes the reduced stiffness.

[0019] S2. Set the non-linear analysis working condition in the finite element analysis software; Since the contact interface is allowed to separate and slide, non-linear analysis needs to be considered. Since the deformation is small deformation, it is not necessary and impossible to reform the stiffness of the structure according to the deformation of the structure, that is, geometric non-linearity is not considered.

[0020] S3. Carry out small deformation contact non-linear simulation and calculation on the structure.

[0021] Embodiment 2 Taking an I-beam as an example, an I-beam is established in SAP2000 and placed on a flat tabletop, as Figure 1 and Figure 2 shown. The clear distance L of the tabletop is 6m, the supporting lengths at both ends are both 0.5m, the flange width of the I-beam is 300mm, the height is 600mm, the plate thickness is 16mm, the material is Q355 steel, and the uniformly distributed surface load within the clear distance is 100kN / m 2 , and the self-weight of the structure is not considered. The friction spring is simulated using the connection unit Damper-Friction Spring, and the element spacing is taken as 100mm, and the connection unit length is taken as 50mm.

[0022] The Damper-Friction Spring in the connection unit is used for contact connection. When defining the properties, U1 refers to the normal direction of the contact interface, which is the axial direction of the connection unit. U1 stiffness: Due to the nonlinear contact between the structure and the bearing platform surface, the linear analysis stiffness is not considered for the time being. The axial property is defined as only compressive and not tensile. Since the structure contacts the ground in this embodiment, the vertical stiffness should be taken as large enough, approaching rigidity. Temporarily, the axial stiffness of the connection unit per unit area is taken as 10 6 kN / mm / m 2 , and according to the subordinate area of the connection unit, the axial initial stiffness of the connection unit in the nonlinear analysis is calculated; The stiffness when the connection is disengaged should be less than the stiffness at rest. Therefore, the slip stiffness should be less than the initial stiffness, and the value should be determined according to the structure material. Temporarily, it is taken as 1 / 10 of the initial stiffness; the pre-compression displacement is taken as -0.1~-1mm, which is used as an initial condition for the nonlinear analysis. The termination displacement is the displacement when the connection unit starts to take the slip stiffness. When taking 0, it means that the stiffness is taken as the slip stiffness by default during the calculation.

[0023] U2 and U3 refer to the tangential direction of the contact interface, which is the horizontal direction of the connection unit. U2 and U3 stiffness: The shear position is the position where the shear deformation of the connection unit occurs, that is, the intersection point of the connection unit and the structure. The horizontal direction is defined as compressive to simulate tangential friction. Since the axial resultant force is larger than the horizontal resultant force and the shear stiffness is smaller, according to engineering experience, the tangential stiffness of the connection unit per unit area is temporarily taken as 10 4 kN / mm / m 2 ; The stiffness when the connection slips should be less than the stiffness at rest. Therefore, the slip stiffness should be less than the initial stiffness, and the value should be determined according to the structure material. Temporarily, it is taken as 1 / 10 of the initial stiffness; both the pre-compression displacement and the termination displacement are set to 0.

[0024] To consider the contact nonlinearity, the analysis type should be selected as nonlinear. Since the deformation of general structures satisfies the small deformation assumption, large displacements are not selected; when considering geometric nonlinearity, especially large deformations, after the contact interface slides, the axial stiffness of the connection unit remains unchanged, but the normal stiffness of the contact interface decreases significantly, which does not conform to the design situation. As Figure 3 shown, where Figure 3 a in is the U1 direction without considering geometric nonlinearity, Figure 3 b in is the U1 direction considering geometric nonlinearity. And this analysis mainly considers contact nonlinearity, ignores the change of the structural geometric stiffness, and does not need to consider the P-Delta effect. Therefore, the final scheme is to choose not to consider geometric nonlinearity.

[0025] Since the structure is relatively complex, if there are too many steps during the calculation, it will make the calculation time too long but the accuracy cannot be improved. The accuracy and efficiency should be taken into account. It has been verified that in the nonlinear analysis similar to small deformation contact, taking the minimum value as 1 can ensure the accuracy and make the calculation time the shortest.

[0026] The axial force of the connection unit can be reflected by the corresponding support reaction force. The accuracy of the Damper-Friction Spring connection unit and the analysis method settings will be demonstrated from the aspects of support reaction force, deformation, and stress.

[0027] To verify the accuracy of the analysis method settings, while keeping other conditions unchanged, the geometric nonlinearity in the load case is set to not consider geometric nonlinearity and consider the large deformation mode respectively. When not considering geometric nonlinearity, the support reaction force at one end of the beam is as Figure 4 shown, and when considering large deformation, the support reaction force at one end of the beam is as Figure 5 shown. It can be known from symmetry that when considering large deformation, the sum of the support reaction forces is inconsistent with the sum of the external loads, that is, the connection unit fails prematurely and cannot achieve the actual simulation effect. When not considering geometric nonlinearity, the sum of the support reaction forces is consistent with the sum of the external loads. Therefore, geometric nonlinearity should not be considered, verifying the accuracy of the analysis method.

[0028] To verify the accuracy of the Damper-Friction Spring connection unit simulation, the Damper-Friction Spring connection unit, the linear linear connection unit, and the fixed support are used to simulate the contact, and the axial force or support reaction force of the connection unit, the deformation at the contact position, and the stress of the overall structure are comprehensively compared and demonstrated.

[0029] When using the Damper-Friction Spring connection unit, the axial force of the connection unit is as Figure 6 shown. Only the connection units near the inner side are compressed, and the rest of the connection units are out of work due to tension, which is consistent with the actual situation. When using the linear linear connection unit, the axial force of the connection unit is as Figure 7 shown. The connection units are both in tension and compression, which is inconsistent with the actual situation. When using the fixed support, the support reaction force is as Figure 8 shown, where F1, F2, and F3 represent the x-direction reaction force, y-direction reaction force, and z-direction reaction force of the support reaction force in the finite element analysis software respectively, and the z-direction reaction force is the vertical support reaction force. When the structure is fixedly connected to the ground, the vertical reaction force F3 of the support reaction force has positive and negative values, indicating that there is both tension and compression in the vertical direction at the contact position, which is inconsistent with the actual situation.

[0030] When using the Damper-Friction Spring connection unit, the contact position disengages at the tensile part, and the deformation situation is consistent with the actual situation, as Figure 9 shown. When using the linear linear connection unit and the fixed support, the deformation at the contact position is similar, and there is no disengagement or sliding phenomenon, which is inconsistent with the actual situation, as Figure 10 and Figure 11 shown.

[0031] When the Damper-Friction Spring connection unit is adopted, the stress of the upper flange of the I-beam at the support is close to 0 while that of the lower flange is not 0. There is a difference in stress between the upper and lower flanges, indicating that after adopting the Damper-Friction Spring connection unit, the support is neither a fixed connection nor a hinged connection. The stress situation is as Figure 12 shown. When the linear linear connection unit and the fixed support are adopted, the stresses of the upper and lower flanges at the support are not 0 and are similar in magnitude, indicating that the simulation of the contact by the linear connection unit and the fixed support does not conform to the actual situation. The stress situation is as Figure 13 and Figure 14 shown.

[0032] Therefore, the present invention adopts the above-mentioned small deformation contact nonlinear simulation method, which provides an important reference for the accurate calculation and design of structures such as modular units, beam laying, and tunnel linings, saving materials, reducing energy consumption, and improving production efficiency. Its application method can be embedded in the program to form an automated option to achieve digital twin; after adopting the Damper-Friction Spring connection unit in SAP2000, the points on the structural surface have always established a contact relationship with a certain point on the contact interface, and there is no change in the contact relationship. The mesh division does not need to be too dense, reducing the calculation amount. And not considering the nonlinear deformation makes the normal stiffness of the contact interface remain unchanged before disengagement, which is closer to the actual situation; when the contact interface is a support, multiple points can be used to establish a contact relationship between the contact interface and the structural surface.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A small deformation contact nonlinear simulation method, characterized in that: It includes the following steps: S1. Use a friction spring to simulate the contact at the contact interface; S2. Set the non-linear analysis working conditions in the finite element analysis software; S3. Conduct small deformation contact non-linear simulation and calculation on the structure.

2. The small deformation contact nonlinear simulation method according to claim 1, characterized in that: In S1, a friction spring is used for simulation. The normal direction of the contact interface is allowed to disengage, and the tangential direction is allowed to slide.

3. A small deformation contact nonlinear simulation method according to claim 2, characterized in that: The normal direction settings of the contact interface in S1 include the following three cases: the structure contacts the ground; the structures contact each other; the normal direction of the contact interface disengages.

4. A small deformation contact non-linear simulation method according to claim 3, characterized in that: When the structure contacts the ground, the normal stiffness of the contact interface takes the vertical stiffness of the spring per unit area as 10 6 kN / mm / m 2 ; when the structures contact each other, the normal stiffness of the contact interface is considered and taken according to the elastic modulus of the material and the measured value; when the contact interface is normally disengaged, the normal stiffness is reduced according to the structure material and the measured value. After the contact interface starts to disengage, the normal stiffness of the contact interface takes the reduced stiffness.

5. A small deformation contact nonlinear simulation method according to claim 4, characterized in that: The tangential direction settings of the contact interface in S1 include: when the structure contacts the ground and when the structures contact each other, the tangential stiffness between the contact interfaces is small, and the value needs to be determined according to the friction coefficient and the measured value; when the contact interface slides tangentially, the tangential stiffness decreases, and the tangential stiffness is reduced according to the structure material and the measured value. After the contact interface starts to slide, the tangential stiffness of the contact interface takes the reduced stiffness.

6. A small deformation contact nonlinear simulation method according to claim 5, characterized in that: In S2, since the contact interface is allowed to disengage and slide, non-linear analysis needs to be considered. Since the deformation at the contact interface is small deformation, the stiffness of the structure cannot be reformed according to the deformation of the structure, that is, geometric non-linearity is not considered.

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