JP2010271305A - Method for evaluation of surface distortion on metal sheet, apparatus for computing evaluation value of surface distortion of metal sheet, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To directly and quantitatively evaluate surface distortions of a metal sheet to be evaluated. <P>SOLUTION: Measurement values of the surface dimensions of the metal sheet 1 acquired by a measuring device 200 are input. An interpolation unit 102 interpolates the measurement values by the measuring device 200 into an orthogonal grid shape. A Gaussian curve calculation unit 103 computes a Gaussian curve through the use of values on orthogonal grid points, that is, measurement values when the measurement values by the measuring device 200 are on the orthogonal grid points and interpolation computation values when the measurement values by the measuring device 200 are not on the orthogonal grid points. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for evaluating surface distortion of a metal plate for evaluating surface distortion of the metal plate, an evaluation value calculation device for the surface distortion of the metal plate, and a program.

  Industrial products whose surfaces are mirror or semi-mirror surfaces, such as automotive exterior panels and painted architectural wall panels after press molding / painting, have surface wavy distortion called “surface distortion”. Even if the amount of distortion is small, the background image appearing on the surface appears to be greatly distorted.

  It has been difficult to quantitatively measure the unevenness of about 10 μm to 100 μm on the target surface having a size of several hundred mm to several m using a distance meter represented by a laser displacement meter. Therefore, from an optical viewpoint, there is known a method for evaluating surface distortion from the degree of distortion using a phenomenon in which a mirror image such as a background stripe pattern appearing on a target surface appears distorted by surface distortion.

  For example, Patent Document 1 discloses a method for measuring a distortion of a mirror-coated panel and a measuring apparatus for projecting a striped image on the surface of the mirror-coated panel and directly evaluating the striped image by visual observation.

  Further, for example, Patent Document 2 uses a phenomenon in which a bright and dark pattern reflected on a mirror surface or half mirror surface of a measurement target surface is distorted by surface distortion, and uses a photographing unit to capture a mirror image of a plurality of light and dark patterns reflected on the measurement target surface. An apparatus and method for measuring surface distortion is disclosed that calculates the amount of surface distortion using the captured image.

Japanese Patent Laid-Open No. 11-153420 JP 2008-224341 A

  However, the method disclosed in Patent Document 1 is a qualitative surface distortion observation method, and has not led to quantification of surface distortion.

  In addition, the technique described in Patent Document 2 quantitatively evaluates the amount of surface distortion using optical means, but there is a problem in investment efficiency because the configuration of the optical device becomes complicated. In addition, since the surface distortion is indirectly evaluated from the optical measurement value, there is a problem that the evaluation accuracy of the surface distortion depends on the accuracy of conversion from the optical measurement to the actual distortion amount.

  This invention is made | formed in view of the above points, and it aims at enabling it to evaluate the surface distortion of the metal plate of evaluation object directly and quantitatively.

ここで、最大主曲率とは、曲率の絶対値が最も大きくなる方向の、曲率の絶対値をいう。
また、本発明の金属板の面歪みの評価方法の他の特徴とするところは、前記測定装置は前記評価対象の金属板の表面を二次元に走査して計測値を取得する点にある。又は、計算対象として有限要素法に基づく成形解析及び除荷解析後の形状データの計算値を用いることもできる。
また、本発明の金属板の面歪みの評価方法の他の特徴とするところは、前記測定装置による計測値又は有限要素法に基づく計算値を直交格子状に補間する手順を有する点にある。
また、本発明の金属板の面歪みの評価方法の他の特徴とするところは、注目格子点上のガウス曲率の計算値をその周囲の格子点上のガウス曲率又は最大主曲率の方向の計算値を用いてフィルタリングする手順を更に有し、前記フィルタリングされたガウス曲率の計算値に基づいて、前記金属板の面歪みを評価する点にある。
本発明の金属板の面歪みの評価値演算装置は、金属板の面歪みを評価するための評価値を求める金属板の面歪みの評価値演算装置であって、測定装置により取得された評価対象の金属板の表面形状の計測値又は有限要素法に基づく成形解析及び除荷解析後の形状データの計算値を入力し、前記入力された値に基づく直交格子点上の値を用いて、下式（１）によりガウス曲率を計算する或いは最大主曲率の方向を計算する構成にしたことを特徴とする。

本発明のプログラムは、金属板の面歪みを評価するための評価値を求めるためのプログラムであって、測定装置により取得された評価対象の金属板の表面形状の計測値又は有限要素法に基づく成形解析及び除荷解析後の形状データの計算値を入力し、前記入力された計測値に基づく直交格子点上の値を用いて、下式（１）によりガウス曲率を計算する或いは最大主曲率の方向を計算する処理をコンピュータに実行させる。

The method for evaluating surface strain of a metal plate according to the present invention is a method for evaluating surface strain of a metal plate for evaluating the surface strain of the metal plate, the surface shape of the metal plate to be evaluated is measured by a measuring device, and the measurement is performed. Using the values on the orthogonal grid points based on the measured values by the device, the Gaussian curvature is calculated by the following formula (1) or the direction of the maximum principal curvature is calculated to evaluate the surface distortion of the metal plate. And

Here, the maximum principal curvature means the absolute value of the curvature in the direction in which the absolute value of the curvature is the largest.
Another feature of the method for evaluating surface distortion of a metal plate according to the present invention is that the measuring device scans the surface of the metal plate to be evaluated two-dimensionally to obtain a measurement value. Or the calculation value of the shape data after the shaping | molding analysis and unloading analysis based on a finite element method can also be used as calculation object.
Another feature of the method for evaluating surface strain of a metal plate according to the present invention is that it has a procedure for interpolating measurement values obtained by the measuring device or calculation values based on a finite element method in an orthogonal lattice pattern.
Another feature of the method for evaluating the surface strain of the metal plate according to the present invention is that the calculated value of the Gaussian curvature on the target lattice point is calculated as the Gaussian curvature or the maximum principal curvature direction on the surrounding lattice points. The method further includes a step of filtering using a value, and evaluating the surface distortion of the metal plate based on the calculated value of the filtered Gaussian curvature.
An evaluation value calculation device for surface distortion of a metal plate according to the present invention is an evaluation value calculation device for surface distortion of a metal plate for obtaining an evaluation value for evaluating the surface distortion of the metal plate, and the evaluation obtained by the measurement device Enter the measured value of the surface shape of the target metal plate or the calculated value of the shape data after the forming analysis and unloading analysis based on the finite element method, and using the value on the orthogonal grid point based on the input value, It is characterized in that the Gaussian curvature is calculated by the following equation (1) or the direction of the maximum principal curvature is calculated.

The program of the present invention is a program for obtaining an evaluation value for evaluating the surface distortion of a metal plate, and is based on a measurement value of a surface shape of a metal plate to be evaluated acquired by a measuring device or a finite element method. The calculation value of the shape data after the forming analysis and the unloading analysis is input, and the Gauss curvature is calculated by the following formula (1) using the value on the orthogonal lattice point based on the input measurement value, or the maximum principal curvature Causes the computer to execute the process of calculating the direction of the.

  According to the present invention, the surface shape of the metal plate to be evaluated is measured, and the surface distortion of the metal plate is directly quantified by calculating the Gaussian curvature or the maximum principal curvature direction using the values on the orthogonal lattice points. Can be evaluated.

It is a figure which shows the function structure of the evaluation value calculating apparatus of the surface distortion of the metal plate which concerns on 1st Embodiment. It is a figure for demonstrating the shape difference identified by the code | symbol of Gaussian curvature. It is a figure for demonstrating the measuring method of the metal plate of evaluation object, and its surface shape. It is a figure for demonstrating the outline | summary of interpolation. It is a figure for demonstrating the outline | summary of interpolation. It is a figure for demonstrating the outline | summary of filtering. It is a figure which shows an example of the weighting coefficient used for filtering. It is a contour figure of the gauss curvature computed by the method of a 1st embodiment. It is a contour figure of the gauss curvature computed by the method of a 1st embodiment. It is a figure for demonstrating the inspection range. It is a characteristic view which shows the relationship between the sum total of the absolute value of the Gauss curvature calculated by the method of 1st Embodiment, and the sensory evaluation rank of the surface distortion by a skilled worker. The characteristic which shows the relationship between the sum total of the absolute value of the Gaussian curvature calculated for the shape data after forming analysis and unloading analysis based on the finite element method by the technique of the first embodiment, and the sensory evaluation rank of the surface distortion by the skilled worker FIG. It is a figure which shows the function structure of the evaluation value calculating apparatus of the surface distortion of the metal plate which concerns on 2nd Embodiment. It is a characteristic view which shows the relationship between the absolute value of the change of the largest principal curvature direction calculated with the method of 2nd Embodiment, and the sensory evaluation rank of the surface distortion by a skilled worker. The relationship between the absolute value of the change in the maximum principal curvature direction calculated for the shape data after the forming analysis and unloading analysis based on the finite element method by the method of the second embodiment and the sensory evaluation rank of the surface distortion by the skilled worker FIG.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
(First embodiment)
The first embodiment of the present invention is intended to evaluate the surface distortion of a metal plate by measuring the surface shape of the metal plate to be evaluated and calculating the Gaussian curvature. The Gaussian curvature K can be calculated by the following equation (1). Depending on the sign of the Gaussian curvature K, as shown in FIGS. 2 (a), (b) and (c), an elliptical shape (K> 0), free It is divided into a physical type (K = 0) and a hyperbolic type (K <0), and a shape difference can be identified.

  FIG. 1 is a diagram showing a functional configuration of an evaluation value calculation device for surface distortion of a metal plate according to a first embodiment to which the present invention is applied. In this embodiment, as shown in FIG. 3, an automobile door panel (steel plate) in which an embossed portion (concave portion) 1 a for a door handle is formed is a metal plate 1 to be evaluated. In such a metal plate 1, surface distortion tends to occur particularly around the embossed portion 1a.

  Reference numeral 101 denotes an input unit that inputs a measurement value of the surface shape of the metal plate 1 acquired by the measuring apparatus 200. Although the measuring device 200 is assumed to be a contact type three-dimensional shape measuring device, a non-contact type three-dimensional shape measuring device using laser light or the like may be used. The measuring device 200 scans the surface of the metal plate 1 two-dimensionally and acquires a measurement value. Specifically, as shown by the arrows in FIG. 3, the surface shape of the metal plate 1 is measured at a constant pitch in the u direction at one v direction position, and this is repeated while shifting the v direction position.

  An interpolation unit 102 interpolates the measurement values obtained by the measuring apparatus 200 in an orthogonal lattice shape. In order to calculate the Gaussian curvature by the equation (1), as shown in FIG. 4D, the shape data needs to be arranged on the orthogonal lattice points on the two-dimensional surface of the uv axis. However, in actuality, there may be a deviation from the orthogonal lattice points due to the positional accuracy of the measuring apparatus 200. For example, FIG. 4B shows a state where the measurement position in the u direction is shifted from the orthogonal lattice point. Therefore, as shown in FIGS. 4C and 5, linear interpolation is performed between the measurement positions, and interpolation is performed so that all shape data are arranged on the orthogonal lattice points. In FIG. 4C, the dotted line indicates the position of the orthogonal lattice point, the gray circle indicates the actual measurement value, and the ● indicates the interpolation calculation value.

Reference numeral 103 denotes a Gaussian curvature calculation unit, which interpolates if the value on the orthogonal grid point, that is, the measurement value by the measurement device 200 is on the orthogonal grid point, and the measurement value by the measurement device 200 is not on the orthogonal grid point. Using the calculated value, the Gaussian curvature is calculated by Equation (1). The expression (1) ′ represents Gaussian curvatures K (i, j) ˜ (for example, the notation of K˜ is given by “˜” on K) at the coordinate point (u _i , u _j ). F˜ is a value on an orthogonal grid point (interpolation calculation if the measured value by the measuring device 200 is on the orthogonal grid point, and if the measured value by the measuring device 200 is not on the orthogonal grid point) Value).

  Reference numeral 104 denotes a filter unit. As shown in FIG. 6, the calculated value K (i, j) of the Gaussian curvature on the target lattice point (i, j) is used as the calculated value of the Gaussian curvature on the surrounding lattice points. Use to filter. As shown in FIG. 6, paying attention to the calculation grid of nine points surrounded by a broken line, using the weight setting as shown in FIG. Correct the calculated value of the Gaussian curvature at the center point. This correction is called filtering, and the influence of noise can be reduced.

  Reference numeral 105 denotes an output unit that outputs a calculated value of the Gaussian curvature filtered by the filter unit 104 as an evaluation value for evaluating the surface distortion of the metal plate. For example, as will be described later, the calculated value of the Gaussian curvature at each part of the metal plate 1 is represented by a contour diagram and output to a display (not shown).

  As shown in FIGS. 2A and 2C, when the Gaussian curvature is larger than 0 or smaller than 0, it is considered that irregularities are formed on the surface of the metal plate 1. Therefore, for example, if a part of the surface of the metal plate 1 is used as an inspection region and the total sum of absolute values of Gaussian curvature is large in the inspection region, it can be evaluated that surface distortion has occurred. In the present embodiment, it is assumed that a person evaluates surface distortion based on the result output from the output unit 105. However, for example, a predetermined threshold value is prepared in advance, and the absolute value of the Gaussian curvature in the inspection region. If the total sum exceeds the threshold value, a function of automatically evaluating that surface distortion has occurred in the inspection region may be provided.

FIGS. 8A and 8B show contour diagrams of the Gaussian curvature calculated by the method of the present embodiment. Fig.8 (a) shows the contour figure of the steel plate which passed the sensory test by a skilled worker, and FIG.8 (b) shows the contour figure of the steel plate which failed. FIG. 8 is originally expressed in red (−8.6 × 10 ⁻⁷ direction in the figure) when the Gaussian curvature is negatively increased and yellow (1.0 × 10 ⁻⁶ direction in the figure) when positively increased. In the middle (orange), there is no surface distortion. The embossed part is not subject to analysis.

  Comparing FIGS. 8A and 8B, it can be seen that the absolute value of the Gaussian curvature around the embossed portion is increased in the rejected steel sheet. It also matches the surface distortion occurrence pointed out by skilled workers in sensory inspection. From these results, it is shown that the Gaussian curvature calculated by applying the present invention is an effective technical index for the evaluation of surface distortion.

  FIGS. 9A to 9F show contour diagrams of Gaussian curvatures of six types of steel plates calculated by the method of the present embodiment. Only the steel plate (1) was a steel plate that passed the sensory inspection by a skilled worker, and the steel plates (2) to (6) were steel plates that were rejected. The steel plate (1) is the steel plate shown in FIG. 8 (a), and the steel plate (6) is the steel plate shown in FIG. 8 (b). When the magnitude of the Gaussian curvature around the embossed part is compared between the accepted steel plate (1) and the rejected steel plates (2) to (6), the Gaussian curvature of the steel plate (1) is the steel plate (2). -It turns out that a small value is clearly shown compared with the Gaussian curvature of a steel plate (6).

FIG. 11 shows the results of calculating the sum of absolute values of Gaussian curvatures in the upper and lower inspection areas of the embossed portion shown in FIG. 10 and investigating the correspondence relationship with the sensory evaluation rank of surface distortion by a skilled worker. . FIG. 11A shows the result in the inspection region above the embossed portion, and FIG. 11B shows the result in the inspection region below the embossed portion. 11A and 11B, the horizontal axis represents the sum of the absolute values of the Gaussian curvature, and the vertical axis represents the sensory evaluation rank (expressed as a numerical value of 1 to 8, where 1 is acceptable and 2 or more is unacceptable). It can be seen that when the sum of absolute values of Gaussian curvature increases, the sensory evaluation ranking tends to deteriorate, and there is a good correspondence between the two.
Also, a finite element method analysis model is created in the same shape as this embodiment, stress-strain relationships obtained from the six types of steel plates used in the embodiment are input, and forming analysis and springback are performed under the same conditions as in the embodiment. Analysis (unloading analysis) was performed. The analysis of the finite element method was carried out using the commercially available dynamic explicit software PAMSTAMP. In FIG. 12, the sum of absolute values of the Gaussian curvatures in the upper and lower inspection areas of the embossed portion shown in FIG. 10 is calculated for the springback calculation result, and the correspondence relationship with the sensory evaluation rank of surface distortion by a skilled worker is shown. The survey results are shown. FIG. 12A shows the result in the inspection region above the embossed portion, and FIG. 12B shows the result in the inspection region below the embossed portion. 12A and 12B, the horizontal axis represents the sum of the absolute values of the Gaussian curvature, and the vertical axis represents the sensory evaluation rank (expressed as a numerical value of 1 to 8, where 1 is acceptable and 2 or more is unacceptable). Although the absolute value of the Gaussian curvature is slightly different from the horizontal axis in FIG. 11, when the sum of the absolute values of the Gaussian curvature increases, the sensory evaluation rank tends to deteriorate, and there is a good correspondence between the two. I understand.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described. Here, the automobile door panel (steel plate) in which the embossed portion (concave portion) 1a for the door handle shown in FIG.

  FIG. 13 is a diagram showing a functional configuration of an evaluation value calculation device for surface distortion of a metal plate according to a second embodiment to which the present invention is applied. Reference numeral 101 denotes an input unit that inputs a measurement value of the surface shape of the metal plate 1 acquired by the measuring apparatus 200. Although the measuring device 200 is assumed to be a contact type three-dimensional shape measuring device, a non-contact type three-dimensional shape measuring device using a laser beam or the like may be used. The measuring device 200 scans the surface of the metal plate 1 two-dimensionally and acquires a measurement value. Specifically, as shown by the arrows in FIG. 3, the surface shape of the metal plate 1 is measured at a constant pitch in the u direction at one v direction position, and this is repeated while shifting the v direction position.

  An interpolation unit 102 interpolates the measurement values obtained by the measuring apparatus 200 in an orthogonal lattice shape. In order to accurately calculate the direction of the maximum principal curvature at each evaluation point, as shown in FIG. 4D, it is necessary that the shape data be arranged on the orthogonal lattice points on the two-dimensional surface of the uv axis. is there. However, in actuality, there may be a deviation from the orthogonal lattice points due to the positional accuracy of the measuring apparatus 200. For example, FIG. 4B shows a state where the measurement position in the u direction is shifted from the orthogonal lattice point. Therefore, as shown in FIGS. 4C and 5, linear interpolation is performed between the measurement positions, and interpolation is performed so that all shape data are arranged on the orthogonal lattice points. In FIG. 4C, the dotted line indicates the position of the orthogonal lattice point, the gray circle indicates the actual measurement value, and the ● indicates the interpolation calculation value.

  Reference numeral 106 denotes a maximum principal curvature direction calculation unit. If the value on the orthogonal lattice point, that is, the measurement value by the measuring device 200 is on the orthogonal lattice point, the measured value and the measurement value by the measuring device 200 must be on the orthogonal lattice point. For example, the direction θ of the maximum principal curvature is calculated using the interpolation calculation value. The direction of the maximum principal curvature is quantified by an angle θ from the reference u axis in the uv plane shown in FIG.

  Reference numeral 104 denotes a filter unit. As shown in FIG. 6, the calculated value θ in the maximum principal curvature direction on the target lattice point (i, j) is used as the calculated value θ in the maximum principal curvature direction on the surrounding lattice points. Filter. As shown in FIG. 6, paying attention to the calculation grid of 9 points surrounded by a broken line, using the weight setting as shown in FIG. Correct the calculated value of the maximum principal curvature direction at the center point. This correction is called filtering, and the influence of noise can be reduced.

  Reference numeral 105 denotes an output unit that outputs the calculated value in the maximum principal curvature direction filtered by the filter unit 104 as an evaluation value for evaluating the surface distortion of the metal plate. For example, the calculated value of the maximum principal curvature at each part of the metal plate 1 is represented by a contour diagram and output to the display.

  Originally, the outer surface of an automobile door panel or the like is not a flat surface but has a designed design curvature. However, the curvature is a gentle curvature with a radius of curvature of about several thousand to several tens of thousands mm, and there is little or no change in the direction of curvature. Therefore, when the maximum principal curvature direction is evaluated and the change is large, it is considered that irregularities are formed on the surface. For example, if a partial cross section of the surface of the metal plate 1 is an inspection cross section and the absolute value of the change in the maximum principal curvature direction is large in the inspection cross section, it can be evaluated that surface distortion has occurred. In this embodiment, it is assumed that a person evaluates surface distortion based on the result output from the output unit 105. However, for example, a predetermined threshold is prepared in advance, and the maximum principal curvature direction in the inspection cross section is prepared. When the absolute value of the change exceeds a threshold value, a function may be provided that automatically evaluates that surface distortion has occurred in the inspection cross section.

  In FIG. 14, the absolute value of the change in the maximum principal curvature direction in the inspection region of the v = 35 cross section (upper side) and v = −35 cross section (lower side) of the embossed portion shown in FIG. The result of investigating the correspondence with the sensory evaluation ranking of the surface distortion due to. FIG. 14A shows the result in the inspection region above the embossed portion, and FIG. 14B shows the result in the inspection region below the embossed portion. 14 (a) and 14 (b), the horizontal axis represents the absolute value of the change in the maximum principal curvature direction, and the vertical axis represents the sensory evaluation rank (expressed as a numerical value of 1 to 8, 1 is pass, 2 or more is reject). is there. As the absolute value of the change in the maximum principal curvature direction increases, the sensory evaluation ranking tends to deteriorate, and it can be seen that there is a good correspondence between the two.

  Also, a finite element method analysis model is created in the same shape as this embodiment, stress-strain relationships obtained from the six types of steel plates used in the embodiment are input, and forming analysis and springback are performed under the same conditions as in the embodiment. Analysis (unloading analysis) was performed. The analysis of the finite element method was carried out using the commercially available dynamic explicit software PAMSTAMP. FIG. 15 shows the absolute value of the change in the maximum principal curvature direction in the inspection region of the v = 35 cross section (upper side) and v = −35 cross section (lower side) of the embossed portion shown in FIG. The result of investigating the correspondence with the sensory evaluation rank of the surface distortion by skilled workers is shown. FIG. 15A shows the result in the inspection region above the embossed portion, and FIG. 12B shows the result in the inspection region below the embossed portion. In FIGS. 15A and 15B, the horizontal axis indicates the absolute value of the change in the maximum principal curvature direction, and the vertical axis indicates the sensory evaluation rank (expressed as a numerical value of 1 to 8, where 1 is acceptable and 2 or more is unacceptable). is there. Although the absolute value of the change in the maximum principal curvature direction is slightly different compared to the horizontal axis in FIG. 14, when the absolute value of the change in the maximum principal curvature direction is increased, the sensory evaluation ranking tends to be deteriorated and good between the two. It can be seen that there is a corresponding relationship.

  As described above, by using the method to which the present invention is applied, it is possible to quantitatively evaluate the occurrence position and the degree of unevenness of about 10 μm to 100 μm on the target surface having a size of 100 mm to several m. This makes it possible to accurately evaluate the workability of the metal sheet for press work, evaluate the deterioration of the press mold, and inspect the product metal sheet, improve the yield of the product metal sheet, and improve the quality. Contributes to improvement.

  In addition, the evaluation value calculation apparatus of the surface distortion of the metal plate of this invention may be applied to the system comprised from a some apparatus, or may be applied to the apparatus comprised from one apparatus.

  The object of the present invention can also be achieved by supplying a computer program for realizing the above-described functions to a system or apparatus and executing the computer (CPU or MPU) of the system or apparatus. In this case, the computer program itself Constitutes the present invention. As mentioned above, although this invention was demonstrated with various embodiment, this invention is not limited only to these embodiment, A change etc. are possible within the scope of the present invention.

DESCRIPTION OF SYMBOLS 101 Input part 102 Interpolation part 103 Gaussian curvature calculation part 104 Filter part 105 Output part 106 Maximum principal curvature direction calculation part 200 Measuring apparatus

Claims (10)

A method for evaluating surface strain of a metal plate for evaluating surface strain of the metal plate,
The surface shape of the metal plate to be evaluated is measured by the measuring device, and the Gauss curvature is calculated by the following equation (1) using the values on the orthogonal lattice points based on the measurement values obtained by the measuring device. A method for evaluating surface distortion of a metal plate, characterized by evaluating distortion.

A method for evaluating surface strain of a metal plate for evaluating surface strain of the metal plate,
The surface shape of the metal plate to be evaluated is measured by the measuring device, and the direction of the maximum principal curvature is calculated using the value on the orthogonal lattice point based on the measurement value by the measuring device, thereby evaluating the surface distortion of the metal plate. A method for evaluating the surface distortion of a metal plate.   3. The method for evaluating surface distortion of a metal plate according to claim 1, wherein the measuring device scans the surface of the metal plate to be evaluated two-dimensionally to obtain a measurement value. 4.   The surface of the metal plate according to any one of claims 1 to 3, wherein a value on the orthogonal lattice point uses a calculated value of shape data after forming analysis and unloading analysis based on a finite element method. Distortion evaluation method.   5. The method for evaluating surface distortion of a metal plate according to claim 3, further comprising a step of interpolating the measurement values obtained by the measuring device in an orthogonal lattice shape. Filtering the calculated value of the Gaussian curvature on the grid point of interest using the calculated value of the Gaussian curvature on the surrounding grid points;
6. The method for evaluating the surface distortion of a metal plate according to claim 1, wherein the surface distortion of the metal plate is evaluated based on the calculated value of the filtered Gaussian curvature. An evaluation value calculation device for surface distortion of a metal plate for obtaining an evaluation value for evaluating surface distortion of the metal plate,
Input the measured value of the surface shape of the metal plate to be evaluated acquired by the measuring device or the calculated value of the shape data after forming analysis and unloading analysis based on the finite element method, and the orthogonal lattice point based on the input value An apparatus for calculating an evaluation value of surface distortion of a metal plate, characterized in that a Gaussian curvature is calculated by the following equation (1) using the above value.

An evaluation value calculation device for surface distortion of a metal plate for obtaining an evaluation value for evaluating surface distortion of the metal plate,
Input the measured value of the surface shape of the metal plate to be evaluated acquired by the measuring device or the calculated value of the shape data after forming analysis and unloading analysis based on the finite element method, and the orthogonal lattice point based on the input value An apparatus for calculating an evaluation value of surface distortion of a metal plate, wherein the above value is used to calculate the direction of the maximum principal curvature. A program for obtaining an evaluation value for evaluating the surface distortion of a metal plate,
Input the measured value of the surface shape of the metal plate to be evaluated acquired by the measuring device or the calculated value of the shape data after forming analysis and unloading analysis based on the finite element method, and the orthogonal lattice based on the input measured value A program for causing a computer to execute a process for calculating a Gaussian curvature according to the following equation (1) using a value on a point.

A program for obtaining an evaluation value for evaluating the surface distortion of a metal plate,
Input the measured value of the surface shape of the metal plate to be evaluated acquired by the measuring device or the calculated value of the shape data after forming analysis and unloading analysis based on the finite element method, and the orthogonal lattice based on the input measured value A program for causing a computer to execute a process of calculating the direction of the maximum principal curvature using a value on a point.

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