Prediction method for residual curvature of sheet metal straightened by roller type straightener

Abstract

The invention belongs to the technical field of plate straightening, and particularly relates to a method for predicting the residual curvature of a metal plate straightened by a roller type straightening machine. In the calculation process, various influences of technological parameters on the straightening process in the roller type straightening process are comprehensively considered, the straightening residual curvature of the metal plate in the roller type straightening process is predicted, the obtained residual curvature value is basically close to an actual value, and the calculation precision is improved. The method is safe, reliable, accurate in calculation, simple and convenient, the straightening residual curvature of the metal plate under different straightening technological procedures can be accurately predicted, and a product can be better applied to actual production.

Description

Technical Field

[0001] The invention belongs to the technical field of plate straightening, and in particular relates to a method for predicting the residual curvature of a metal plate straightened by a roller straightening machine. Background Art

[0002] During the rolling production process, plate defects such as wave shape, bending and buckling often occur due to various reasons such as uneven plate thickness, temperature changes, improper transportation and improper storage. With the continuous development of science and technology and the continuous saturation of the steel industry, the steel market has higher and higher requirements for product performance and quality. Steel with large output but insufficient additional performance has been difficult to meet the increasingly high living and production needs. Therefore, how to control the plate shape has become a more prominent issue, and good flatness and extremely small internal stress have attracted widespread attention. In actual production, the straightening process is an effective means to improve the flatness of the plate and control residual stress. Plates that meet engineering standards after straightening are widely used in many fields such as aerospace, petrochemical, shipbuilding, water conservancy, and power construction.

[0003] The main purpose of the straightening process is to improve the plate shape and quality. At present, the research on straightening theory mainly focuses on the research of roller system structure, reduction, curvature and residual stress. Among them, the analysis of curvature is the most basic and important in the straightening process. The analysis of other parameters such as straightening force and residual stress must be based on the analysis of curvature. Therefore, in the research of straightening theory, the distribution law of curvature has always been the focus of attention.

[0004] At present, the research on the curvature of the traditional roller straightening process mainly includes experimental method, beam bending method and finite element method. The experimental method can only be used for specific processes at a time, which has great limitations; the beam bending method simplifies the straightening process and is simple to calculate, but it has a certain deviation from the actual straightening process; the finite element method has a large amount of calculation and takes a long time, which cannot meet the actual production needs and is not convenient for engineering application. Therefore, it is necessary to develop a method for predicting the curvature of roller straightening that is short in time, convenient in calculation and has relatively accurate calculation results. Summary of the invention

[0005] In view of the deficiencies in the prior art, an object of the present invention is to provide a method for predicting the residual curvature of a metal sheet straightened by a roller straightening machine.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A method for predicting the residual curvature of a metal sheet straightened by a roller straightening machine comprises the following steps: Step 1: Determine the process parameters for straightening analysis according to the equipment conditions of a certain straightening process and the material properties of the metal sheet; Step 2: In a straightening interval, the metal sheet is divided into two-dimensional grids in the length and thickness directions. units, the thickness direction is divided into units, and from the length direction Start counting from the units; Step 3: Initialize the inverse curvature and calculate the curvature increment in the length direction; Step 4: Set the strain increment of the center line of the plate thickness and calculate the strain in the thickness direction. Stress distribution of the element, through the thickness direction The stress distribution of each unit is calculated. Step 5: According to the convergence condition, determine whether the stress and tensile stress in the cross section are equal. If they are equal, proceed to the first step in the length direction. units, up to the length direction All calculations for each unit are completed; if they are not equal, reset the strain increment of the plate thickness centerline in step 4 and repeat step 4 until they are equal; Step 6: Enter the next straightening interval and repeat steps 2 to 5 until all straightening intervals are calculated to obtain the stress distribution of the metal sheet in all straightening intervals; Step 7: Calculate the integral value of the curvature change in each straightening interval and the double integral value ; Step 8: Calculate the inclination angle and curvature at each straightening roller contact point; Step 9: Calculate the curvature increment in the corresponding length direction according to the curvature at each straightening roller contact point, repeat steps 4 to 8, and obtain the first integral value of the iterative curvature change. and the double integral value ; Step 10: Determine the integral value of the curvature change after iteration and the double integral value Whether the convergence condition is met , If it is satisfied, the curvature calculation result is directly output; if it is not satisfied, the integral value of the curvature change is readjusted and the double integral value , repeat steps 8 to 9 until the convergence condition is met, output the curvature calculation result, and complete the prediction.

[0007] Furthermore, the process parameters in step 1 include the number of straightening rollers , straightening roller diameter , straightening roller pitch , straightening roller pressure , metal sheet yield stress , elastic modulus , Poisson's ratio , Metal sheet thickness , initial curvature and initial residual stress , where the initial residual stress .

[0008] Furthermore, the specific process of step 3 is as follows: Step 3.1: Initialize Roller bending rate , specifically: ; Step 3.2: According to Roller bending rate Calculate the curvature increment along the length direction , specifically: ; in, is the curvature change between the two rollers, For the The reverse curvature of the roller.

[0009] Furthermore, the specific process of step 4 is as follows: Step 4.1: According to the curvature increment in the length direction Set the strain increment at the center line of the plate thickness , specifically: ; in, Indicates the thickness direction Unit in The stress distribution in the direction, Indicates the thickness direction Unit in The plate thickness centerline offset in the direction, Indicates the thickness direction The distance from the element to the center line of the plate thickness; Step 4.2: Calculate the thickness direction Unit in Strain increment in the direction , specifically: ; Step 4.3: Calculate the thickness direction Unit in direction, Stress increment in the direction , , specifically: , within the elastic range: ; ; , within the plastic range: ; ; ; Step 4.4: Calculate the thickness direction Unit in direction, Stress distribution in the direction , , specifically: ; ; Step 4.5: Repeat steps 4.2 to 4.4 until the thickness direction The stress distribution of each unit is calculated.

[0010] Furthermore, the convergence condition in step 5 is: ; in, Represents the tensile stress in the cross section.

[0011] Furthermore, the specific process of step 7 is as follows: Step 7.1: Calculate the unit width bending moment of each straightening interval according to the obtained stress distribution, specifically: ; in, Indicates the length direction within the straightening interval Bending moment per unit width of each unit; Step 7.2: Calculate the integral value of the curvature change of each straightening interval based on the unit width bending moment of each straightening interval and the double integral value , specifically: ; ; in, , Respectively represent Roller contact point and The value of the bending moment per unit width at the roller contact point, , , , , , , , They represent the first and , , , , 、 , The value of the bending moment per unit width of the element.

[0012] Furthermore, the specific process of step 8 is as follows: Step 8.1: Calculate the initial inclination angle of the first roller contact point in the first straightening section , specifically: ; ; ; ; ; ; ; in, Indicates the amount of pressure applied by the first roller. represents the reverse bending rate of the first roller; Step 8.2: Calculate the inclination angle at each straightening roller contact point, specifically: When the first roll in the straightening section is the upper roll: ; in, , Indicates The contact angle of the roller, Indicates The contact inclination angle of the roller; When the first roll in the straightening section is the lower roll: ; Step 8.3: Calculate the curvature at each straightening roll contact point , specifically: When the first roll in the straightening section is the upper roll: ; When the first roll in the straightening section is the lower roll: .

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention predicts the residual curvature of the straightening of the metal sheet during the roller straightening process, and the residual curvature value obtained is basically close to the actual value. In the calculation process, the various effects of the process parameters on the straightening process during the roller straightening process are comprehensively considered to improve the calculation accuracy. The method of the present invention is safe and reliable, accurate in calculation, simple and convenient, and short in time. It can accurately predict the residual curvature of the straightening of the metal sheet under different straightening process regulations, so that the product can be better applied to actual production. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of the nine-roller straightening provided by the present invention; Figure 2 This is a schematic diagram of dividing a metal sheet into units according to the present invention; Figure 3 This is a comparison chart of the predicted value of the straightening curvature of the present invention and the actual value at a certain site.

[0015] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. Example

[0016] The straightening equipment used in this embodiment is a nine-roll straightening machine (see Figure 1 ), the upper rollers of the straightening machine are tilted and pressed down, while the lower rollers are fixed. As long as the pressing amount of the head and tail rollers of the upper rollers is set, the pressing amount of the entire roller system can be determined according to the linear decrease. In each straightening interval, the straightening movement direction is defined as positive, the vertical downward direction is positive, the downward convex deformation curvature is positive, and the bending moment is positive. The specific implementation method of this embodiment is described as follows.

[0017] Step 1: Determine the process parameters for straightening analysis according to the equipment conditions of a certain straightening process and the material properties of the metal sheet, where the process parameters include the number of straightening rollers , straightening roller diameter , straightening roller pitch , straightening roller entrance pressure , straightening roller outlet pressure , The first roller of the straightening roller presses down , yield stress of metal sheet , elastic modulus , Poisson's ratio , Metal sheet thickness , initial curvature and initial residual stress .

[0018] Step 2: In a straightening interval, the metal sheet is divided into two-dimensional grids in the length and thickness directions, such as Figure 2 As shown, the length direction is divided into units, the thickness direction is divided into units, and the calculation starts from the first unit in the length direction and the first unit in the thickness direction of the first straightening interval.

[0019] Step 3: Initialize the inverse curvature and calculate the curvature increment in the length direction , the specific process is as follows: Step 3.1: Initialize the reverse bending rate of the first and second rollers , , specifically: ; ; Step 3.2: According to the reverse bending rate of the first roller and the second roller , Calculate the curvature increment along the length direction , specifically: .

[0020] Step 4: Set the strain increment of the center line of the plate thickness and calculate the strain in the thickness direction. Stress distribution of the element, through the thickness direction The stress distribution of each unit is calculated; the specific process is as follows: Step 4.1: According to the curvature increment in the length direction Set the strain increment at the center line of the plate thickness , specifically: ; in, Indicates the thickness direction Unit in The stress distribution in the direction, Indicates the thickness direction Unit in The plate thickness centerline offset in the direction, Indicates the thickness direction The distance from the element to the center line of the plate thickness; This embodiment sets ; Step 4.2: Calculate the thickness direction Unit in Strain increment in the direction , specifically: ; In this embodiment, the first unit in the thickness direction is calculated. The strain increment in the direction is For example, the solution is: ; Step 4.3: Calculate the thickness direction Unit in direction, Stress increment in the direction , , specifically: , within the elastic range: ; ; , within the plastic range: ; ; ; In this embodiment, the first unit in the thickness direction is calculated. direction, Stress increment in the direction , For example, the solution is: ; ; Step 4.4: Calculate the thickness direction Unit in direction, Stress distribution in the direction , , specifically: ; ; In this embodiment, the first unit in the thickness direction is calculated. direction, Stress distribution in the direction , For example, the solution is: ; ; Step 4.5: Repeat steps 4.2 to 4.4 until the thickness direction units (i.e. ) has been completely calculated.

[0021] Step 5: According to the convergence condition, determine whether the stress and tensile stress in the cross section are equal. If they are equal, enter the second unit in the length direction until the length direction All calculations for each unit are completed; if they are not equal, reset the strain increment of the center line of the plate thickness in step 4 and repeat step 4 until they are equal; because the tension of the plate remains unchanged during the straightening process, the convergence conditions for judging the stress and tensile stress in the cross section are: ; in, Represents the tensile stress in the cross section.

[0022] Step 6: Enter the next straightening interval and repeat steps 2 to 5 until all straightening intervals are calculated to obtain the stress distribution of the metal sheet in all straightening intervals.

[0023] Step 7: Calculate the integral value of the curvature change in each straightening interval and the double integral value , the specific process is as follows: Step 7.1: Calculate the unit width bending moment of each straightening interval according to the obtained stress distribution, specifically: ; in, Indicates the length direction within the straightening interval Bending moment per unit width of each unit; This embodiment takes the first straightening interval as an example, and the solution is: the unit width bending moment of the first unit in the length direction in the first straightening interval ; Unit width bending moment of the 18th unit in the length direction in the first straightening interval ; Step 7.2: Calculate the integral value of the curvature change of each straightening interval based on the unit width bending moment of each straightening interval and the double integral value , specifically: ; ; in, , Respectively represent Roller contact point and The value of the bending moment per unit width at the roller contact point, , , , , , , , They represent the first and , , , , 、 , The value of the bending moment per unit width of each element; This embodiment takes the first straightening interval as an example, and obtains: the first integral value of the curvature change in the first straightening interval is 1.0651, and the double integral value is 71253.

[0024] Step 8: Calculate the inclination and curvature at each straightening roller contact point. The specific process is as follows: Step 8.1: Calculate the initial inclination angle of the first roller contact point in the first straightening section , specifically: ; ; ; ; ; ; ; in, Indicates the amount of pressure applied by the first roller. represents the reverse bending rate of the first roller; The combined solution of this embodiment is ; Step 8.2: Calculate the inclination angle at each straightening roller contact point, specifically: When the first roll in the straightening section is the upper roll: ; in, , Indicates The contact angle of the roller, Indicates The contact inclination angle of the roller; When the first roll in the straightening section is the lower roll: ; This embodiment takes the first straightening section, where the first roll is the lower roll, as an example, and solves for the inclination angle: ; ; ; ; ; ; ; ; Step 8.3: Calculate the curvature at each straightening roll contact point , specifically: When the first roll in the straightening section is the upper roll: ; When the first roll in the straightening section is the lower roll: ; This embodiment takes the first straightening interval, where the first roll is the lower roll, as an example, and solves for the curvature: ; ; ; ; ; ; ; .

[0025] Step 9: Calculate the curvature increment in the corresponding length direction according to the curvature at each straightening roller contact point, repeat steps 4 to 8, and obtain the first integral value of the iterative curvature change. and the double integral value .

[0026] Step 10: Determine the integral value of the curvature change after iteration and the double integral value Whether the convergence condition is met , :If satisfied, directly output the curvature calculation result; if not satisfied, readjust the single integral value of the curvature change and the double integral value , repeat steps 8 to 9 until the convergence condition is met, output the curvature calculation result, and complete the prediction.

[0027] According to the residual curvature prediction method for straightening metal plates by roller straightening machine proposed by the present invention, the model prediction value of the metal plates used and the actual value of a certain site are statistically analyzed as follows: Figure 3 As shown, by comparing the results, it can be obtained that the residual curvature of the metal plate predicted by the present invention is consistent with the actual value, and the curvature calculation error is within 10%. It can be seen that the residual curvature of the metal plate straightened by the roller straightening machine predicted by the present invention has higher accuracy and can be better applied in actual production.

[0028] The above description is only for better explaining the embodiments of the present invention, and is not intended to limit the present invention. Any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims

1. A method for predicting the residual curvature of a metal sheet straightened by a roller straightening machine, characterized in that: The following steps are involved: Step 1: Determine the process parameters for straightening analysis according to the equipment conditions of a certain straightening process and the material properties of the metal sheet; Step 2: In a straightening interval, the metal sheet is divided into two-dimensional grids in the length and thickness directions. units, the thickness direction is divided into units, and from the length direction Start counting from the units; Step 3: Initialize the inverse curvature and calculate the curvature increment in the length direction; Step 4: Set the strain increment of the center line of the plate thickness and calculate the strain in the thickness direction. Stress distribution of the element, through the thickness direction The stress distribution of each unit has been calculated. Step 5: According to the convergence condition, determine whether the stress and tensile stress in the cross section are equal. If they are equal, proceed to the first step in the length direction. units, up to the length direction All calculations for each unit are completed; if they are not equal, reset the strain increment of the plate thickness centerline in step 4 and repeat step 4 until they are equal; Step 6: Enter the next straightening interval and repeat steps 2 to 5 until all straightening intervals are calculated to obtain the stress distribution of the metal sheet in all straightening intervals; Step 7: Calculate the integral value of the curvature change in each straightening interval and the double integral value ; Step 8: Calculate the inclination angle and curvature at each straightening roller contact point; Step 9: Calculate the curvature increment in the corresponding length direction according to the curvature at each straightening roller contact point, repeat steps 4 to 8, and obtain the first integral value of the iterative curvature change. and the double integral value ; Step 10: Determine the integral value of the curvature change after iteration and the double integral value Whether the convergence condition is met , If it is satisfied, the curvature calculation result is directly output; if it is not satisfied, the integral value of the curvature change is readjusted and the double integral value , repeat steps 8 to 9 until the convergence condition is met, output the curvature calculation result, and complete the prediction.

2. The method for predicting the residual curvature of a metal sheet straightened by a roller straightening machine according to claim 1, characterized in that: The process parameters in step 1 include the number of straightening rollers , straightening roller diameter , straightening roller pitch , straightening roller pressure , metal sheet yield stress , elastic modulus , Poisson's ratio , Metal sheet thickness , initial curvature and initial residual stress , where the initial residual stress .

3. The method for predicting the residual curvature of a metal sheet straightened by a roller straightening machine according to claim 2, characterized in that: The specific process of step 3 is as follows: Step 3.1: Initialize Roller bending rate , specifically: ； Step 3.2: According to Roller bending rate Calculate the curvature increment along the length direction , specifically: ； in, is the curvature change between the two rollers, For the The reverse curvature of the roller.

4. The method for predicting the residual curvature of a metal sheet straightened by a roller straightening machine according to claim 3, characterized in that: The specific process of step 4 is as follows: Step 4.1: According to the curvature increment in the length direction Set the strain increment at the center line of the plate thickness , specifically: ； in, Indicates the thickness direction Unit in The stress distribution in the direction, Indicates the thickness direction Unit in The plate thickness centerline offset in the direction, Indicates the thickness direction The distance from the element to the center line of the plate thickness; Step 4.2: Calculate the thickness direction Unit in Strain increment in the direction , specifically: ； Step 4.3: Calculate the thickness direction Unit in direction, Stress increment in the direction , , specifically: , within the elastic range: ； ； , within the plastic range: ； ； ； Step 4.4: Calculate the thickness direction Unit in direction, Stress distribution in the direction , , specifically: ； ； Step 4.5: Repeat steps 4.2 to 4.4 until the thickness direction The stress distribution of each unit is calculated.

5. The method for predicting the residual curvature of a metal sheet straightened by a roller straightening machine according to claim 4, characterized in that: The convergence condition in step 5 is: ； in, Represents the tensile stress in the cross section.

6. The method for predicting the residual curvature of a metal sheet straightened by a roller straightening machine according to claim 5, characterized in that: The specific process of step 7 is as follows: Step 7.1: Calculate the unit width bending moment of each straightening interval according to the obtained stress distribution, specifically: ； in, Indicates the length direction within the straightening interval Bending moment per unit width of each unit; Step 7.2: Calculate the integral value of the curvature change of each straightening interval based on the unit width bending moment of each straightening interval and the double integral value , specifically: ； ； in, , Respectively represent Roller contact point and The value of the bending moment per unit width at the roller contact point, , , , , , , , They represent the first and , , , , 、 , The value of the bending moment per unit width of the element.

7. The method for predicting the residual curvature of a metal sheet straightened by a roller straightening machine according to claim 6, characterized in that: The specific process of step 8 is as follows: Step 8.1: Calculate the initial inclination angle of the first roller contact point in the first straightening section , specifically: ； ； ； ； ； ； ； in, Indicates the amount of pressure applied by the first roller. represents the reverse bending rate of the first roller; Step 8.2: Calculate the inclination angle at each straightening roller contact point, specifically: When the first roll in the straightening section is the upper roll: ； in, , Indicates The contact angle of the roller, Indicates The contact inclination angle of the roller; When the first roll in the straightening section is the lower roll: ； Step 8.3: Calculate the curvature at each straightening roll contact point , specifically: When the first roll in the straightening section is the upper roll: ； When the first roll in the straightening section is the lower roll: 。

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