A method and system for evaluating the bending performance of a longitudinally sheared girder plate

Abstract

The application provides a longitudinal shear girder plate bending performance evaluation method and system, the method comprises the following steps: obtaining a mechanical response curve of a non-standard tensile sample longitudinal shear characteristic area; determining the failure strain of the longitudinal shear surface by inversely processing the mechanical response curve of the non-standard tensile sample; establishing a bending finite element model, setting boundary conditions and bending angles, and calculating the plastic strain required for the forming of the longitudinal beam; building the relationship between the surface hardness of the longitudinal shear surface and the formability according to the failure strain of the longitudinal shear surface and the plastic strain required for the forming of the longitudinal beam, and evaluating the formability of the longitudinal shear surface through the surface hardness. Based on the longitudinal shear girder plate bending performance evaluation method, the application further provides a longitudinal shear girder plate bending performance evaluation system. The application can consider the plastic flow loss caused by the nonlinear shear of the longitudinal shear surface, quantitatively evaluate the residual plasticity of the surface after the work hardening of the longitudinal shear through the reverse engineering method, effectively evaluate the formability of the subsequent longitudinal beam of the commercial vehicle, reduce the bad part rate of the product, and improve the process control ability.

Description

Technical Field

[0001] This invention belongs to the field of bending performance evaluation technology, and specifically relates to a method and system for evaluating the bending performance of longitudinally sheared beams. Background Technology

[0002] Lightweighting is a crucial way to achieve energy conservation and emission reduction in automobiles. During vehicle operation, in addition to air resistance, rolling resistance, climbing resistance, and acceleration resistance are all directly proportional to the vehicle's mass. Therefore, reducing vehicle mass can effectively reduce fuel consumption and emissions. It can be said that lightweighting is one of the important directions for the development of the automotive industry and a common choice for automakers worldwide.

[0003] The chassis of a commercial vehicle is the main load-bearing component, supporting the weight of the engine, cab, transmission, and cargo. It accounts for 5%-10% of the total vehicle weight, making chassis lightweighting the most effective method for lightweighting commercial vehicles. Domestic commercial vehicle manufacturers primarily achieve chassis lightweighting using high-strength steel plates. The production process for commercial vehicle chassis begins with longitudinal shearing, followed by roll forming into beams. Due to engine assembly requirements, the chassis also undergoes bending to form the final chassis product. The longitudinally sheared surface of the beam plate first undergoes work hardening during shearing, followed by bending. However, higher-strength steel plates inevitably have reduced plasticity, which restricts the longitudinal shearing and bending process during chassis production. This can easily lead to bending cracks in the beams, threatening the vehicle's reliability and durability. Therefore, it is crucial to evaluate and control the bending performance of the longitudinally sheared surface. Currently, most scholars mainly evaluate the formability of metals through DIC non-contact strain measurement. However, this method is cumbersome and complex in terms of sample preparation and product formability evaluation, and its timeliness is poor, affecting the process cycle. Therefore, it is necessary to explore a simpler and more efficient formability evaluation and control method. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method and system for evaluating the bending performance of longitudinally sheared beams. This method allows for strict control of the subsequent formability of materials through simple hardness value testing, and is both concise and efficient.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for evaluating the bending performance of longitudinally sheared large beams includes the following steps:

[0007] Obtain the mechanical response curve of the longitudinal shear characteristic region of the non-standard tensile specimen; inversely compare the mechanical response curve of the non-standard tensile specimen to determine the failure strain of the longitudinal shear surface.

[0008] Establish a bending finite element model, set boundary conditions and bending angle, and calculate the plastic strain required for the forming of the longitudinal beam;

[0009] Based on the failure strain of the longitudinal shear surface and the plastic strain required for the formation of the longitudinal beam, the relationship between the surface hardness and formability of the longitudinal shear surface is established, and the formability of the longitudinal shear surface is evaluated by the surface hardness.

[0010] Furthermore, the method also includes: considering the robustness of the slitting process, introducing a safety factor s for hardness value detection and a hardness value threshold H for incoming inspection. a ;

[0011] Among them, H a =s·H t ;

[0012] The H t This refers to the hardness threshold value corresponding to the forming of the main beam of a commercial vehicle.

[0013] Furthermore, the H t The method for determining the hardness is as follows: establish the relationship between the hardness and residual plasticity of different work-hardened sheets, and combine the interpolation method to determine the hardness threshold H that meets the requirements for forming commercial vehicle beams. t .

[0014] Furthermore, the process of obtaining the longitudinal shear mechanical response curve includes: using the longitudinal shear edge of the frame beam as a characteristic region, preparing a non-standard tensile specimen; and obtaining the mechanical response curve of the longitudinal shear characteristic region of the non-standard tensile specimen using a universal tensile testing machine with an extensometer.

[0015] Furthermore, the process of determining the failure strain of the longitudinal shear surface by reverse benchmarking the mechanical response curve of the non-standard tensile specimen includes: using a finite element-assisted reverse engineering method to reverse benchmark the mechanical response curve of the non-standard tensile specimen and determine the failure strain of the longitudinal shear surface.

[0016] Furthermore, the process of using the finite element-assisted reverse engineering method to reverse-engineer the mechanical response curve of a non-standard tensile specimen and determine the failure strain of the longitudinal shear surface includes:

[0017] The Swift constitutive equation and the Hockett-Sherby constitutive equation were fitted to the uniformly stretched portion of the mechanical response curve, respectively. Then, the extensional stress-strain curve was fitted using the Swift-Hockett-Sherby constitutive equation. The fracture displacement of the experiment was used as the basis for the simulated fracture to determine the fracture strain of the longitudinal shear surface.

[0018] Furthermore, the Swift constitutive equation is:

[0019] σ=C·(ε D +ε pl ) m ;

[0020] Where σ is stress; ε DFor elastic strain; ε pl ρ is the plastic strain; C is the first material constant; m is the second material constant;

[0021] The Hockett-Sherby constitutive equation is:

[0022]

[0023] Where, σ Sat For saturation stress; σ i Let be the yield stress, and α be the third material constant.

[0024] The Swift-Hockett-Sherby constitutive equation is:

[0025]

[0026] Furthermore, the method for establishing the bending finite element model is as follows: based on the dimensions of the commercial vehicle longitudinal beam and the bending machine mold, an Abaqus bending finite element model is established; wherein, the material type is set to the defined Swift-Hockett-Sherby constitutive equation and parameters.

[0027] Furthermore, based on the failure strain of the longitudinal shear surface and the plastic strain required for the formation of the longitudinal beam, the relationship between the surface hardness and formability of the longitudinal shear surface is established. When evaluating the formability of the longitudinal shear surface through surface hardness, a non-contact strain gauge is used to determine the displacement required for various percentage plastic strain work hardening degrees. Various plastic strain work hardening shear pre-deformation plates are prepared, and a clamping device is used when preparing work hardened shear pre-deformation plates to ensure that the plates do not buckle.

[0028] This invention also proposes a bending performance evaluation system for longitudinal shear beams, comprising: an acquisition module, a calculation module, and a construction module;

[0029] The acquisition module is used to acquire the mechanical response curve of the longitudinal shear characteristic region of the non-standard tensile specimen; and to determine the failure strain of the longitudinal shear surface by reverse benchmarking the mechanical response curve of the non-standard tensile specimen.

[0030] The calculation module is used to establish a bending finite element model, set boundary conditions and bending angles, and calculate the plastic strain required for the forming of the longitudinal beam.

[0031] The construction module is used to establish the relationship between the surface hardness and formability of the longitudinal shear surface based on the failure strain of the longitudinal shear surface and the plastic strain required for the formation of the longitudinal beam, and to evaluate the formability of the longitudinal shear surface through surface hardness.

[0032] The effects described in the invention are merely those of the embodiments, and not all the effects of the invention. One of the above technical solutions has the following advantages or beneficial effects:

[0033] This invention proposes a method and system for evaluating the bending performance of longitudinally sheared beams. The method includes obtaining the mechanical response curves of the characteristic regions of the longitudinal shearing of non-standard tensile specimens; determining the failure strain of the longitudinal shear surface by reverse engineering the mechanical response curves of the non-standard tensile specimens; establishing a bending finite element model, setting boundary conditions and bending angles, and calculating the plastic strain required for beam formation; establishing the relationship between the surface hardness and formability of the longitudinal shear surface based on the failure strain of the longitudinal shear surface and the plastic strain required for beam formation, and evaluating the formability of the longitudinal shear surface through surface hardness. Based on this method for evaluating the bending performance of longitudinally sheared beams, a system for evaluating the bending performance of longitudinally sheared beams is also proposed. This invention can consider the plastic loss caused by nonlinear shearing of the longitudinal shear surface, and uses reverse engineering to quantitatively evaluate the residual plasticity of the surface after longitudinal shearing work hardening, effectively assessing the subsequent formability of commercial vehicle beams, reducing the defect rate of products, and improving process control capabilities.

[0034] This invention evaluates the formability of larger products through material-level testing. It can not only be embedded into the product development system to guide the product forming process more quickly and efficiently, but also reduce the cost of experimental trial and error and avoid wasting human and material resources.

[0035] This invention can strictly control the subsequent formability of materials through simple hardness value testing, which is simple and efficient, and is also applicable to other non-proportional processed products that require subsequent formability evaluation. Attached Figure Description

[0036] Figure 1 This is a flowchart of a method for evaluating the bending performance of a longitudinal shear beam plate according to Embodiment 1 of the present invention;

[0037] Figure 2 This is a schematic diagram of the sampling location of the non-standard uniaxial tensile specimen proposed in Embodiment 1 of the present invention;

[0038] Figure 3 This is a diagram showing the dimensions of the tensile specimen proposed in Embodiment 1 of the present invention;

[0039] Figure 4 The load-displacement curve of the tensile specimen proposed in Example 1 of this invention;

[0040] Figure 5 The determination of the fracture strain of the specimen as proposed in Example 1 of this invention;

[0041] Figure 6 This is the finite element model of the beam bending proposed in Embodiment 1 of the present invention;

[0042] Figure 7 This is a schematic diagram of the bending simulation results proposed in Embodiment 1 of the present invention;

[0043] Figure 8This is a schematic diagram of the shear pre-deformed plates with different work hardening processes proposed in Embodiment 1 of the present invention;

[0044] Figure 9 This illustrates the relationship between hardness and residual plasticity of different work-hardened plates as proposed in Example 1 of this invention.

[0045] Figure 10 This is a schematic diagram of a longitudinal shear beam bending performance evaluation system proposed in Embodiment 2 of the present invention. Detailed Implementation

[0046] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. The following disclosure provides many different embodiments or examples for implementing different structures of the invention. To simplify the disclosure of the invention, components and arrangements of specific examples are described below. Furthermore, reference numerals and / or letters may be repeated in different examples. This repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. It should be noted that the components illustrated in the drawings are not necessarily drawn to scale. Descriptions of well-known components, processing techniques, and processes are omitted in this invention to avoid unnecessarily limiting the invention.

[0047] Example 1

[0048] Embodiment 1 of this invention proposes a method for evaluating the bending performance of longitudinally sheared beams, which assesses the residual formability of the cross-section after longitudinal shearing. This method is beneficial for the quality evaluation of longitudinally sheared beams before they enter the site and reduces the defect rate of products.

[0049] Figure 1 This is a flowchart of a method for evaluating the bending performance of a longitudinal shear beam plate according to Embodiment 1 of the present invention;

[0050] In step S100, the mechanical response curve of the longitudinal shear characteristic region of the non-standard tensile specimen is obtained;

[0051] Using the longitudinal shear surface of the main beam as the characteristic region, non-standard tensile specimens were prepared. The mechanical response curves of the longitudinal shear characteristic region of the non-standard tensile specimens were obtained by using a universal tensile testing machine with an extensometer.

[0052] Embodiment 1 of this invention uses a commercial vehicle frame as an example. The commercial vehicle frame plate has a thickness of 12mm, is made of S600MC material, and has a yield strength of 600MPa. The frame plate is first processed into a frame plate through slitting and roll forming. The method for evaluating and controlling its bending performance is also described.

[0053] Using the longitudinal shear edge of the frame beam as the characteristic region, non-standard tensile specimens were prepared using an electrical discharge wire cutting machine. Figure 2 As shown, Figure 2This is a schematic diagram of the sampling location for the non-standard uniaxial tensile specimen proposed in Embodiment 1 of the present invention; specimen dimensions. Figure 3 As shown, Figure 3 This is a diagram showing the dimensions of the tensile specimen proposed in Embodiment 1 of the present invention. The thickness of the uniformly stretched section of the specimen ranges from 1.2 to 1.5 mm. The specimen is clamped at both ends using a universal tensile testing machine. An extensometer is installed on the uniformly stretched section of the non-standard specimen, and the specimen is stretched at a speed of 3 mm / min. The load-displacement curve of the specimen is recorded, and the mechanical response curve of the longitudinal shear characteristic region of the non-standard tensile specimen is obtained as shown below. Figure 4 As shown, Figure 4 This is the load-displacement curve of the tensile specimen proposed in Example 1 of the present invention.

[0054] In step S101, the failure strain of the longitudinal shear surface is determined by reverse benchmarking the mechanical response curve of the non-standard tensile specimen.

[0055] Using the finite element-assisted reverse engineering method, the mechanical response curves of non-standard tensile specimens are reverse-referenced to determine the failure strain of the longitudinal shear surface.

[0056] A simulation model of a non-standard tensile specimen was built using Abaqus finite element software, with boundary conditions consistent with those of the tensile test. The Swift constitutive equation and the Hockett-Sherby constitutive equation were fitted to the uniformly stretched portion of the mechanical response curve from step one, respectively. Finally, the Swift-Hockett-Sherby constitutive equation was used to fit the epitaxial stress-strain curve.

[0057] The Swift constitutive equation is:

[0058] σ=C·(ε D +ε pl ) m ;

[0059] Where σ is stress; ε D For elastic strain; δ pl ρ is the plastic strain; C is the first material constant; m is the second material constant;

[0060] The Hockett-Sherby constitutive equation is:

[0061]

[0062] Where, σ Sa t is the saturation stress; σ i Let be the yield stress, and α be the third material constant.

[0063] The Swift-Hockett-Sherby constitutive equation is:

[0064]

[0065] The final determined parameters are C = 1030, m = 0.204, and σ. Sat =750, α=0.26.

[0066] Using reverse engineering, a finite element model identical to the specimen was constructed with a mesh size of 0.2 mm and boundary conditions consistent with the experiment. By adjusting α = 0.72, the mechanical response curve of the non-standard tensile specimen was reverse-engineered. Figure 5 The fracture strain of the specimen proposed in Example 1 of this invention is shown. Using the fracture displacement from the experiment as the basis for simulated fracture, the fracture strain on the longitudinal shear surface is determined to be 25.4%.

[0067] In step S102, a bending finite element model is established, boundary conditions and bending angle are set, and the plastic strain required for the forming of the longitudinal beam is calculated.

[0068] Based on the dimensions of the commercial vehicle's longitudinal beams and the bending machine molds, an Abaqus bending finite element model was established as follows: Figure 6 As shown, Figure 6 This is the finite element model of the beam bending proposed in Embodiment 1 of the present invention;

[0069] Based on the dimensions of the longitudinal beam of the commercial vehicle and the bending machine mold, an Abaqus bending finite element model was established; the material type was set to the defined Swift-Hockett-Sherby constitutive equations and parameters.

[0070] Set boundary conditions and a bending angle of 10.5°. Figure 7 This is a schematic diagram of the bending simulation results proposed in Embodiment 1 of the present invention; the equivalent plastic strain is 12.6%. This indicates that the longitudinal shear formability can meet the requirements of bending formability.

[0071] In step S103, the relationship between the surface hardness and formability of the longitudinal shear surface is established based on the failure strain of the longitudinal shear surface and the plastic strain required for the formation of the longitudinal beam, and the formability of the longitudinal shear surface is evaluated by the surface hardness.

[0072] The displacement required for various percentage plastic strain work hardening degrees is determined by using a non-contact strain gauge. Shear pre-deformation plates with various plastic strain work hardening are prepared, and a clamping device is used to ensure that the plates do not buckle during the preparation of work hardened shear pre-deformation plates.

[0073] In this application, the displacement required for 60%, 70%, 80%, 90%, and 100% plastic strain work hardening is determined using a DIC non-contact strain gauge. Figure 7 The template shown is stretched to the corresponding displacement to prepare five types of plastic strain work hardening shear pre-deformation. During the preparation process, a clamping device is used to ensure that the plate does not buckle.

[0074] Uniaxial tensile specimens and hardness test specimens were prepared on pre-deformed plates. Figure 8 This is a schematic diagram of shear pre-deformed plates with different work hardening processes proposed in Embodiment 1 of the present invention.

[0075] The hardness and mechanical response of the plates after different work hardening processes were tested.

[0076] The relationship between hardness and residual plasticity of different work-hardened sheet materials was established, and the hardness threshold H corresponding to the forming of commercial vehicle beams was determined by interpolation. t ; Figure 9 This invention relates to the relationship between hardness and residual plasticity of different work-hardened sheet materials as proposed in Embodiment 1; and uses interpolation to determine the hardness threshold H corresponding to the forming of commercial vehicle beams. t =407.

[0077] To consider the robustness of the slitting process, a safety factor s for hardness testing and a hardness threshold H for incoming inspection are introduced. a ;

[0078] Among them, H a =s·H t H t This refers to the hardness threshold value corresponding to the forming of the main beam of a commercial vehicle.

[0079] H in this application a =386.

[0080] The safety factor s is recommended to be between 0.85 and 0.95. When the surface hardness value of the longitudinal shear is below 386, the longitudinal shear surface can meet the bending formability requirements.

[0081] The longitudinal shearing beam plate bending performance evaluation method proposed in Embodiment 1 of this invention can take into account the plastic loss caused by nonlinear shearing of the longitudinal shearing surface. By using reverse engineering, it can quantitatively evaluate the residual plasticity of the surface after longitudinal shearing work hardening, effectively evaluate the subsequent formability of commercial vehicle beams, reduce the defect rate of products, and improve process control capabilities.

[0082] The longitudinal shearing beam plate bending performance evaluation method proposed in Embodiment 1 of this invention evaluates the formability of larger products through material-level testing. This method can not only be embedded into the product development system to guide the product forming process more quickly and efficiently, but also reduce the cost of experimental trial and error and avoid wasting human and material resources.

[0083] The method for evaluating the bending performance of longitudinally sheared beams proposed in Embodiment 1 of this invention can strictly control the subsequent formability of materials through simple hardness value testing. It is simple and efficient, and is also applicable to other products that require subsequent formability evaluation after non-proportional processing.

[0084] Example 2

[0085] Based on the method for evaluating the bending performance of longitudinally sheared girder plates proposed in Embodiment 1 of the present invention, Embodiment 2 of the present invention also proposes a system for evaluating the bending performance of longitudinally sheared girder plates. Figure 10 This is a schematic diagram of a longitudinal shear beam bending performance evaluation system proposed in Embodiment 2 of the present invention, including: an acquisition module, a calculation module, and a construction module;

[0086] The acquisition module is used to acquire the mechanical response curve of the longitudinal shear characteristic region of the non-standard tensile specimen; the failure strain of the longitudinal shear surface is determined by inversely comparing the mechanical response curve of the non-standard tensile specimen.

[0087] The calculation module is used to build a bending finite element model, set boundary conditions and bending angles, and calculate the plastic strain required for the forming of the longitudinal beam;

[0088] The module is used to establish the relationship between the surface hardness and formability of the longitudinal shear surface based on the failure strain of the longitudinal shear surface and the plastic strain required for the formation of the longitudinal beam, and to evaluate the formability of the longitudinal shear surface through surface hardness.

[0089] In the acquisition module, non-standard tensile specimens are prepared using the longitudinal shear edge of the wing surface of the frame beam as the characteristic region; the mechanical response curves of the longitudinal shear characteristic region of the non-standard tensile specimens are obtained by using a universal tensile testing machine with an extensometer.

[0090] Using the finite element-assisted reverse engineering method, the mechanical response curves of non-standard tensile specimens are reverse-referenced to determine the failure strain of the longitudinal shear surface.

[0091] The process of determining the failure strain on the longitudinal shear plane by reverse-calibrating the mechanical response curve of a non-standard tensile specimen includes:

[0092] The Swift constitutive equation and the Hockett-Sherby constitutive equation were fitted to the uniformly stretched portion of the mechanical response curve, respectively. Then, the extensional stress-strain curve was fitted using the Swift-Hockett-Sherby constitutive equation. The fracture displacement of the experiment was used as the basis for the simulated fracture to determine the fracture strain of the longitudinal shear surface.

[0093] The Swift constitutive equation is:

[0094] σ=C·(ε D +ε pl ) m ;

[0095] Where σ is stress; ε D For elastic strain; ε pl ρ is the plastic strain; C is the first material constant; m is the second material constant;

[0096] The Hockett-Sherby constitutive equation is:

[0097]

[0098] Where, σ Sat For saturation stress; σ i Let be the yield stress, and α be the third material constant.

[0099] The Swift-Hockett-Sherby constitutive equation is:

[0100]

[0101] Based on the dimensions of the longitudinal beam of the commercial vehicle and the bending machine mold, an Abaqus bending finite element model was established; the material type was set to the defined Swift-Hockett-Sherby constitutive equations and parameters.

[0102] In the calculation module, an Abaqus bending finite element model is established based on the dimensions of the commercial vehicle longitudinal beam and the bending machine mold; the material type is set to the defined Swift-Hockett-Sherby constitutive equation and parameters.

[0103] In the module construction, considering the robustness of the slitting process, a safety factor s for hardness testing and a hardness threshold H for incoming inspection are introduced. a ;

[0104] Among them, H a =s·H t ;

[0105] The H t This refers to the hardness threshold value corresponding to the forming of the main beam of a commercial vehicle.

[0106] H t The method for determining the hardness is as follows: establish the relationship between the hardness and residual plasticity of different work-hardened sheets, and combine the interpolation method to determine the hardness threshold H that meets the requirements for forming commercial vehicle beams. t .

[0107] The longitudinal shearing beam plate bending performance evaluation system proposed in Embodiment 2 of this invention can take into account the plastic loss caused by nonlinear shearing of the longitudinal shearing surface. By using reverse engineering, it can quantitatively evaluate the residual plasticity of the surface after longitudinal shearing work hardening, effectively evaluate the subsequent formability of commercial vehicle beams, reduce the defect rate of products, and improve process control capabilities.

[0108] The longitudinal shearing beam plate bending performance evaluation system proposed in Embodiment 2 of this invention evaluates the formability of larger products through material-level testing. It can not only be embedded into the product development system to guide the product forming process more quickly and efficiently, but also reduce the cost of experimental trial and error and avoid wasting human and material resources.

[0109] The longitudinal shearing beam plate bending performance evaluation system proposed in Embodiment 2 of this invention can strictly control the subsequent formability of materials through simple hardness value testing. It is simple and efficient, and is also applicable to other non-proportional processed products that require subsequent formability evaluation.

[0110] The description of the relevant parts of the longitudinal shearing beam plate bending performance evaluation system provided in Embodiment 2 of this application can be found in the detailed description of the corresponding parts of the longitudinal shearing beam plate bending performance evaluation method provided in Embodiment 1 of this application, and will not be repeated here.

[0111] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that the elements inherent in a process, method, article, or apparatus that includes a list of elements are included. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Additionally, portions of the technical solutions provided in the embodiments of this application that are consistent with the implementation principles of corresponding technical solutions in the prior art have not been described in detail to avoid excessive elaboration.

[0112] While specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art can make other modifications or variations based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for evaluating the bending performance of longitudinally sheared large beams, characterized in that, Includes the following steps: Obtain the mechanical response curve of the longitudinal shear characteristic region of the non-standard tensile specimen; inversely compare the mechanical response curve of the non-standard tensile specimen to determine the failure strain of the longitudinal shear surface. Establish a bending finite element model, set boundary conditions and bending angle, and calculate the plastic strain required for the forming of the longitudinal beam; Based on the failure strain of the longitudinal shear surface and the plastic strain required for the formation of the longitudinal beam, the relationship between the surface hardness and formability of the longitudinal shear surface is established, and the formability of the longitudinal shear surface is evaluated by the surface hardness. The method further includes: considering the robustness of the slitting process, introducing a safety factor for hardness value detection. Hardness threshold values ​​for incoming inspection applications ; in, ; The The threshold value for the hardness value corresponding to the forming of the commercial vehicle beam; The The determination method is as follows: establish the relationship between the hardness and residual plasticity of different work-hardened sheet materials, and combine the interpolation method to determine the hardness threshold value corresponding to the forming of commercial vehicle beams. .

2. The method for evaluating the bending performance of longitudinally sheared beams according to claim 1, characterized in that, The process of obtaining the mechanical response curve of the longitudinal shear characteristic region of the non-standard tensile specimen includes: using the longitudinal shear edge of the wing surface of the frame beam as the characteristic region, preparing a non-standard tensile specimen; and obtaining the mechanical response curve of the longitudinal shear characteristic region of the non-standard tensile specimen using a universal tensile testing machine with an extensometer.

3. The method for evaluating the bending performance of longitudinally sheared beams according to claim 1, characterized in that, The process of determining the failure strain of the longitudinal shear surface by reverse benchmarking the mechanical response curve of the non-standard tensile specimen includes: using the finite element-assisted reverse engineering method to reverse benchmark the mechanical response curve of the non-standard tensile specimen and determine the failure strain of the longitudinal shear surface.

4. The method for evaluating the bending performance of longitudinally sheared beams according to claim 3, characterized in that, The process of using the finite element-assisted reverse engineering method to reverse-engineer the mechanical response curve of a non-standard tensile specimen and determine the failure strain of the longitudinal shear surface includes: The Swift constitutive equation and the Hockett-Sherby constitutive equation were fitted to the uniformly stretched portion of the mechanical response curve, respectively. Then, the extensional stress-strain curve was fitted using the Swift-Hockett-Sherby constitutive equation. The fracture displacement of the experiment was used as the basis for the simulated fracture to determine the fracture strain of the longitudinal shear surface.

5. The method for evaluating the bending performance of longitudinally sheared beams according to claim 4, characterized in that, The Swift constitutive equation is: ； in, For stress; For elastic strain; Plastic strain; It is the first material constant; This is the second material constant; The Hockett-Sherby constitutive equation is: ； in, It is saturated stress; For yield stress, It is the third material constant; The Swift-Hockett-Sherby constitutive equation is: 。 6. The method for evaluating the bending performance of longitudinally sheared beams according to claim 5, characterized in that, The method for establishing the bending finite element model is as follows: Based on the dimensions of the commercial vehicle longitudinal beam and the bending machine mold, an Abaqus bending finite element model is established; wherein, the material type is set to the defined Swift-Hockett-Sherby constitutive equation and parameters.

7. The method for evaluating the bending performance of longitudinally sheared beams according to claim 1, characterized in that, Based on the failure strain of the longitudinal shear surface and the plastic strain required for the formation of the longitudinal beam, the relationship between the surface hardness and formability of the longitudinal shear surface is established. When evaluating the formability of the longitudinal shear surface through surface hardness, a non-contact strain gauge is used to determine the displacement required for various percentage plastic strain work hardening degrees. Various plastic strain work hardening shear pre-deformation plates are prepared. When preparing work hardened shear pre-deformation plates, a clamping device is used to ensure that the plates do not buckle.

8. A system for evaluating the bending performance of longitudinally sheared beams, used to perform the method described in any one of claims 1 to 7, characterized in that, include: Acquisition module, calculation module, and construction module; The acquisition module is used to acquire the mechanical response curve of the longitudinal shear characteristic region of the non-standard tensile specimen; and to determine the failure strain of the longitudinal shear surface by reverse benchmarking the mechanical response curve of the non-standard tensile specimen. The calculation module is used to establish a bending finite element model, set boundary conditions and bending angles, and calculate the plastic strain required for the forming of the longitudinal beam. The construction module is used to establish the relationship between the surface hardness and formability of the longitudinal shear surface based on the failure strain of the longitudinal shear surface and the plastic strain required for the formation of the longitudinal beam, and to evaluate the formability of the longitudinal shear surface through surface hardness.

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