JP6355980B2 - Strain measuring apparatus and strain measuring method - Google Patents

Description

  The present invention relates to a strain measuring apparatus and a strain measuring method.

  For example, members such as automobile frames and arms are manufactured by pressing a steel plate. In press forming, if the forming conditions are not appropriate, a large strain is generated in the steel sheet, and a crack or a crack may be generated in the greatly distorted portion. For this reason, a steel sheet is press-formed under various forming conditions, and the amount of strain generated in the steel sheet by press forming is measured to determine the appropriateness of the forming conditions.

  A three-dimensional deformation measurement system (trade name: ARGUS) is known as a system for measuring the amount of strain generated in a steel sheet after press forming. In the measurement of the strain amount by this three-dimensional deformation measurement system, lattice points (dots) arranged in a matrix at the same pitch in the row direction and the column direction are printed on the surface of the flat steel plate. Then, the steel plate is press-formed, and the steel plate after the press forming is photographed by a camera, and based on the amount of change in the position of each lattice point before and after press forming, for example, the maximum principal strain around each lattice point and The minimum principal distortion is obtained.

  However, if the contrast between the lattice point and its surroundings is small, such as when the density of the lattice point formed on the surface of the steel plate is low, the lattice point cannot be recognized from the image taken by the camera. It is not possible to obtain the maximum principal strain around the.

  In such a case, the scribed circle test is performed again. In the scribed circle test, a pattern composed of a plurality of perfect circles arranged in a matrix is printed on the surface of a flat steel plate. After the press forming of the steel plate, the major axis and the minor axis of each pattern deformed into an ellipse are measured by a measuring operator manually using a measuring instrument such as a caliper. Then, based on the major axis and minor axis of each pattern, the maximum principal strain and the minimum principal strain at the position of each pattern are obtained.

JP 2007-152407 A

  However, in the scribed circle test, the major axis and the minor axis of all patterns must be manually measured, and the maximum principal strain and the minimum principal strain at each pattern position must be obtained. For this reason, the scribed circle test takes time and effort. In addition to the steel plate used for strain measurement by the three-dimensional deformation measurement system, a new steel plate for the scribed circle test must be prepared, so that a place for storing the steel plate is required.

  The object of the present invention is to obtain the strain amount around the lattice point without performing the scribed circle test when the strain amount around the lattice point cannot be measured by the three-dimensional deformation measurement system. A strain measuring device and a strain measuring method are provided.

  In order to achieve the above object, a strain measuring apparatus according to one aspect of the present invention provides a method for measuring a strain after a metal plate is press-formed with lattice points aligned in a matrix at the same pitch in the row and column directions. A strain measuring device used for measuring strain generated in the metal plate, a measuring unit used for measuring a distance between two points, a display unit for displaying information, and a lattice point 1 Between the reference means and each of the measurement target points set by the setting means. Output means for outputting an instruction for measuring each distance to the display unit, and after output by the output unit, based on the distance and pitch measured using the measurement unit, by the reference point and each of the measurement target points Computing means for computing the amount of distortion in each determined direction.

  In the measurement of the strain amount by the three-dimensional deformation measurement system, lattice points arranged in a matrix at the same pitch in the row direction and the column direction are displayed on the surface of the flat metal plate. When a part of the lattice points is not recognized by the three-dimensional deformation measurement system, the three-dimensional deformation measurement system cannot acquire the distortion amount around the unrecognized lattice points.

  In this case, the strain measurement apparatus can acquire the strain amount around the lattice points that are not recognized by the three-dimensional deformation measurement system. In the strain measuring apparatus, a plurality of measurement target points that define an ellipse centered on a reference point are set. Then, an instruction to measure each distance between the reference point and the plurality of measurement target points is displayed on the display unit. The measurement operator visually recognizes a grid point that has not been recognized by the three-dimensional deformation measurement system, and uses the measurement unit according to the display on the display unit, with the visually recognized grid point as a reference point, and a plurality of measurements. Each distance between the target points is measured in order. When the measurement of each distance is completed, the strain measurement apparatus calculates the strain amount in each direction determined by the reference point, that is, the lattice point that has not been recognized by the three-dimensional deformation measurement system and each of the measurement target points.

  Therefore, if the amount of distortion around the lattice point cannot be acquired because the lattice point is not recognized by the 3D deformation measurement system, the amount of distortion around the lattice point is acquired without performing a scribed circle test. can do.

  The strain measuring device includes a maximum main strain acquisition unit that acquires the maximum value of the distortion amounts calculated by the calculation unit as a maximum main strain, and a reference point and a maximum main strain acquired by the acquisition unit with respect to the reference point. A second output means for outputting an instruction to measure the distance between the grid points located in a direction perpendicular to the direction to the display section, and after the output by the second output means, measured using the measurement section It may further include a minimum principal distortion acquisition means for acquiring a minimum principal distortion by calculation based on the distance.

  According to this configuration, when the distortion amount in each direction determined by the reference point and each of the measurement target points is calculated, the maximum value of the calculated distortion amounts is acquired as the maximum main distortion. Then, an instruction to measure the distance between the reference point and the lattice point located in the direction orthogonal to the direction of the maximum principal strain with respect to the reference point is displayed on the display unit. When the measurement operator measures the distance according to this display, the minimum principal strain is obtained by calculation based on the measured distance. Therefore, the maximum principal strain and the minimum principal strain around the reference point can be acquired.

  In the strain measurement method according to another aspect of the present invention, the grid points arranged in a matrix at the same pitch in the row direction and the column direction are displayed on the surface of the metal plate, and the press of the metal plate on which the grid points are displayed. After forming, one of the lattice points is used as a reference point, a plurality of lattice points that define an ellipse centered on the reference point are set as measurement target points, and the reference point and the measurement target point are measured using a measuring instrument. Each distance between the individual is manually measured, and the amount of distortion in each direction determined by the reference point and each of the measurement target points is acquired.

  According to this method, since the lattice point is not recognized by the three-dimensional deformation measurement system, when the amount of distortion around the lattice point cannot be acquired, the scribe circle test is not performed and the region around the lattice point is not performed. The amount of distortion can be acquired.

  According to the present invention, when the amount of strain around a lattice point cannot be measured by the three-dimensional deformation measurement system, the amount of strain around the lattice point can be acquired without performing a scribed circle test. As a result, it is possible to reduce the labor and time required for measuring the amount of strain compared to the case where the scribed circle test is performed. Moreover, the place which stores the metal plate for a scribed circle test can be made unnecessary.

It is a front view of the distortion measuring device concerning one embodiment of the present invention. It is a block diagram which shows the principal part of the electrical constitution of a distortion measuring device. It is a flowchart (the 1) which shows the flow of a measurement process. It is a flowchart (the 2) which shows the flow of a measurement process. It is a flowchart (the 3) which shows the flow of a measurement process. It is a flowchart (the 4) which shows the flow of a measurement process. It is a table | surface which shows the relationship between the measurement object point, the angle with respect to a reference direction, and reference | standard length.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a front view of a strain measuring apparatus 1 according to an embodiment of the present invention.

  The strain measuring device 1 is in the form of a digital caliper. That is, the strain measuring device 1 is integrated with the main scale 2, the slider 3 provided so as to be movable along the main scale 2, the jaws 4, 5 provided on the main scale 2 and the slider 3, and the slider 3. And an operation indicator 6 provided in the apparatus.

  The jaws 4 and 5 are made of a transparent material at the tip portion or the entirety thereof. Thus, when the measurement operator makes the tips of the jaws 4 and 5 contact the two points in order to measure the distance between the two points, the two points pass through the tips of the jaws 4 and 5. And can be visually recognized.

  The operation display 6 is provided with a display unit 11 for displaying various information and a plurality of operation buttons operated by a measurement operator. The display part 11 consists of a liquid crystal display, for example. The operation buttons include a power button 12, a plus button 13, a minus button 14, a set button 15, and an escape button 16.

  FIG. 2 is a block diagram showing the main part of the electrical configuration of the strain measuring apparatus 1.

  The strain measurement apparatus 1 further includes a control unit 21 having a configuration including a CPU and a memory, and an encoder 22 for detecting the amount of movement of the slider 3 with respect to the main scale 2.

  An encoder 22 is electrically connected to the control unit 21. When the slider 3 is moved by the measurement operator, a detection signal is input from the encoder 22 to the control unit 21. The control unit 21 acquires the distance between the tips of the jaws 4 and 5 based on the detection signal input from the encoder 22.

  The control unit 21 is connected to each part of the operation display 6, that is, the display unit 11, the power button 12, the plus button 13, the minus button 14, the set button 15, and the escape button 16. When the measurement operator presses the power button 12, the plus button 13, the minus button 14, the set button 15 and the escape button 16, an operation signal is output from a switch (not shown) incorporated therein. An operation signal is input to the control unit 21. The control unit 21 controls the display of the display unit 11 based on the operation signal and the calculation result of the distance between the tips of the jaws 4 and 5.

  3A, 3B, 3C, and 3D are flowcharts showing the flow of the measurement process. FIG. 4 is a table showing the relationship between the measurement target point, the angle with respect to the reference direction, and the reference length.

  The strain measuring device 1 is used for acquiring the amount of strain generated in a metal plate after press forming of the metal plate.

  Specifically, in the measurement of the amount of strain by a three-dimensional measurement system, after dots (lattice points) arranged in a matrix at the same pitch in the row and column directions are printed on the surface of a flat metal plate A metal plate is press-molded. Then, the metal plate after press forming is photographed by a camera, and the amount of strain around each dot is obtained based on the amount of change in the position of each dot before and after press forming, and the maximum main strain and minimum main strain are obtained. Is done. At this time, if the contrast difference between the dots and the surrounding area is small, such as the density of the dots formed on the surface of the metal plate is small, the dots are not recognized from the image taken by the camera, and the dots are not recognized around the unrecognized dots. The amount of distortion cannot be acquired. The strain measuring apparatus 1 is used to acquire the amount of distortion around the dots that have not been recognized by the three-dimensional deformation measurement system, and hence the maximum principal distortion and the minimum principal distortion.

  When the strain measuring apparatus 1 is used, the measurement operator pushes the power button 12 to turn on the strain measuring apparatus 1. When the power is turned on, the measurement process shown in FIGS. 3A to 3B is executed by the control unit 21.

  In the measurement process, first, a screen (pitch input screen) for requesting input of the pitch of dots printed in a flat state on a metal plate to be measured is output to the display unit 11 (step S1). In response to the request, the measurement operator can input the pitch by pressing the plus button 13, the minus button 14, and the set button 15.

  For example, when the plus button 13 is pressed once, the dimension value displayed on the display unit 11 is increased by 1 mm, and when the minus button 14 is pressed once, the dimension value displayed on the display unit 11 is increased. Decreases in 1 mm increments. When the set button 15 is pressed while a dimension value equal to the dot pitch is displayed on the display unit 11, the dimension value is input as the pitch. Note that the escape button 16 is pressed when canceling various inputs or returning one screen displayed on the display unit 11.

  After the pitch input screen is displayed, it is repeatedly determined whether or not a pitch has been input (step S2). When the pitch is input (YES in step S2), the input pitch (dimension value) is stored in the memory as the pitch P (step S3).

  Next, dots arranged in a matrix at the same pitch P in the row direction and the column direction are virtually set. Then, with one of the dots as a reference point, a plurality of dots that define an ellipse centered on the reference point are set as measurement target points (step S4). Specifically, as shown in FIG. 4, the dot closest to the reference point in a predetermined reference direction (angle 0 °) is set as the first measurement target point, and the reference direction and the angle from the reference point The dot closest to the direction intersecting at 45 ° is set as the second measurement target point, and the dot closest to the direction intersecting the reference direction at an angle of 26.5 ° from the reference point is set as the third measurement target point. The dot that is set and is closest to the direction intersecting the reference direction at an angle of 63.4 ° from the reference point is set as the fourth measurement target point.

  After setting the measurement target point, the display unit 11 is instructed to measure the distance between the reference point and the first measurement target point and guides the measurement to the display unit 11 (step S5).

  The measurement operator moves the slider 3 to adjust the distance between the tips of the jaws 4 and 5 while bringing the tips of the jaws 4 and 5 into contact with the reference point and the first measurement target point, respectively. 15 is pushed. In response to the pressing operation of the set button 15, the distance between the tips of the jaws 4 and 5 is acquired based on the detection signal input from the encoder 22, and the acquired distance is input as the first measurement value. The

  When the first measurement value is input (YES in step S6), the first measurement value is stored in the memory as the measurement value X (step S7).

  Then, the measured value X is divided by the reference length “3P / 2” (P: pitch) to calculate the distortion amount a (step S8).

  Thereafter, the strain amount a is stored in the memory as the maximum principal strain α, and in association with this, information for specifying the first measurement target point is stored in the memory as the measurement position data β, and “display A” is specified. Information is stored in the memory as display instruction data γ (step S9).

  Thus, the first measurement is completed, and then the second measurement is started.

  In the second measurement, measurement of the distance between the reference point and the second measurement target point is instructed, and “display B” for guiding the measurement is output to the display unit 11 (step S10).

  The measurement operator moves the slider 3 to adjust the distance between the tips of the jaws 4 and 5 and brings the tips of the jaws 4 and 5 into contact with the reference point and the second measurement target point, respectively. 15 is pushed. In response to the pressing operation of the set button 15, the distance between the tips of the jaws 4 and 5 is acquired based on the detection signal input from the encoder 22, and the acquired distance is input as the second measured value. The

  When the second measurement value is input (YES in step S11), the second measurement value is stored in the memory as the measurement value X (step S12).

  Then, the measured value X is divided by the reference length “(2√2 + 1) P / 2” to calculate the distortion amount a (step S13).

  Thereafter, the magnitude of the strain amount a and the maximum principal strain α stored in the memory are compared to determine whether or not the strain amount a is larger than the maximum principal strain α (step S14).

  When the strain amount a is larger than the maximum principal strain α (YES in step S14), the maximum principal strain α stored in the memory is updated to the newly calculated strain amount a and the measurement position stored in the memory. The data β is updated to information specifying the second measurement target point, and the display instruction data γ is updated to information specifying “display B” (step S15).

  On the other hand, when the distortion amount a is equal to or less than the maximum principal strain α, the maximum principal strain α, the measurement position data β, and the display instruction data γ stored in the memory are maintained without being updated (Step S15). skip).

  Thus, the second measurement is completed, and then the third measurement is started.

  In the third measurement, measurement of the distance between the reference point and the third measurement target point is instructed, and “display C” for guiding the measurement is output to the display unit 11 (step S16).

  The measurement operator moves the slider 3 and adjusts the distance between the tips of the jaws 4 and 5 while bringing the tips of the jaws 4 and 5 into contact with the reference point and the third measurement target point, respectively. 15 is pushed. In response to the pressing operation of the set button 15, the distance between the tips of the jaws 4 and 5 is acquired based on the detection signal input from the encoder 22, and the acquired distance is input as the third measured value. The

  When the third measurement value is input (YES in step S17), the third measurement value is stored in the memory as the measurement value X (step S18).

  Then, by dividing the measured value X by the reference length “(2√5 + 1) P / 2”, the distortion amount a is calculated (step S19).

  Thereafter, the magnitude of the strain amount a and the maximum principal strain α stored in the memory are compared to determine whether or not the strain amount a is larger than the maximum principal strain α (step S20).

  When the strain amount a is larger than the maximum principal strain α (YES in step S20), the maximum principal strain α stored in the memory is updated to the newly calculated strain amount a and the measurement position stored in the memory. The data β is updated to information specifying the third measurement target point, and the display instruction data γ is updated to information specifying “display C” (step S21).

  On the other hand, when the strain amount a is equal to or less than the maximum principal strain α, the maximum principal strain α, the measurement position data β, and the display instruction data γ stored in the memory are maintained without being updated (in step S21). skip).

  Thus, the third measurement is completed, and then the fourth measurement is started.

  In the fourth measurement, a measurement of the distance between the reference point and the fourth measurement target point is instructed, and “display D” for guiding the measurement is output to the display unit 11 (step S22).

  The measurement operator moves the slider 3 to adjust the distance between the tips of the jaws 4 and 5, and brings the tips of the jaws 4 and 5 into contact with the reference point and the fourth measurement target point, respectively. 15 is pushed. In response to the pressing operation of the set button 15, the distance between the tips of the jaws 4 and 5 is acquired based on the detection signal input from the encoder 22, and the acquired distance is input as the fourth measured value. The

  When the fourth measurement value is input (YES in step S23), the fourth measurement value is stored in the memory as the measurement value X (step S24).

  Then, the measurement value X is divided by the reference length “(2√5 + 1) P / 2” to calculate the distortion amount a (step S25).

  Thereafter, the magnitude of the strain amount a and the maximum principal strain α stored in the memory are compared to determine whether or not the strain amount a is larger than the maximum principal strain α (step S26).

  When the strain amount a is larger than the maximum principal strain α (YES in step S26), the maximum principal strain α stored in the memory is updated to the newly calculated strain amount a and the measurement position stored in the memory. The data β is updated to information specifying the fourth measurement target point, and the display instruction data γ is updated to information specifying “display D” (step S27).

  On the other hand, when the strain amount a is equal to or less than the maximum principal strain α, the maximum principal strain α, the measurement position data β, and the display instruction data γ stored in the memory are maintained without being updated (Step S27). skip).

  This completes the fourth measurement.

  After completion of the fourth measurement, the maximum principal strain α stored in the memory is read, and the maximum principal strain α is output to the display unit 11. Further, the measurement position data β stored in the memory is read, and the measurement target point specified by the measurement position data β is output to the display unit 11 (step S28).

  The dot closest to the reference point in the direction of the straight line passing through the measurement target point and the reference point output to the display unit 11, that is, the direction orthogonal to the direction of the maximum principal strain α is the fifth measurement target point. Is set. Thereafter, measurement of the distance between the reference point and the fifth measurement target point is instructed, and “display E” for guiding the measurement is output to the display unit 11 (step S29).

  The measurement operator moves the slider 3 to adjust the distance between the tips of the jaws 4 and 5 and brings the tips of the jaws 4 and 5 into contact with the reference point and the fifth measurement target point, respectively. 15 is pushed. In response to the pressing operation of the set button 15, the distance between the tips of the jaws 4 and 5 is acquired based on the detection signal input from the encoder 22, and the acquired distance is input as the fifth measured value. The

  When the fifth measurement value is input (YES in step S30), the fifth measurement value is stored in the memory as the measurement value Y (step S31).

  Then, the minimum principal strain α2 is obtained by calculation by substituting the measured value Y into a predetermined calculation formula f (Y) (step S32).

  Thereafter, the acquired minimum principal strain α2 and the maximum principal strain α stored in the memory are output to the display unit 11 (step S33), and a series of measurement processes is terminated.

  As described above, the distortion measuring apparatus 1 can acquire the distortion amount a around the dots that have not been recognized by the three-dimensional deformation measurement system, and thus can acquire the maximum principal distortion α and the minimum principal distortion α2. .

  Therefore, when the amount of distortion around the dot cannot be acquired because the dot is not recognized by the three-dimensional deformation measurement system, the amount of distortion around the dot can be acquired without performing the scribed circle test. it can.

  As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

  For example, although an example in which four measurement target points are set has been taken, as long as there are a plurality of measurement target points, there may be three points or five or more points.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

1: Strain measuring device 4: Jaw (measurement unit)
5: Joe (measurement part)
11: Display unit 21: Control unit (setting unit, output unit, calculation unit, maximum main strain acquisition unit, second output unit, minimum main strain acquisition unit)

Claims (3)

This is a strain measuring device used to measure strain generated in a metal plate after press forming of the metal plate on which the lattice points aligned in a matrix at the same pitch in the row direction and the column direction are displayed. And
A measurement unit used to measure the distance between two points;
A display for displaying information;
One of the lattice points is used as a reference point, and the lattice point closest to the predetermined reference direction from the reference point is used as a first measurement target point, and intersects the reference direction from the reference point at an angle of 45 °. The lattice point closest to the direction is set as the second measurement target point, and the lattice point closest to the direction intersecting the reference direction at an angle of 26.5 ° from the reference point is set as the third measurement target point. Setting means for setting each of the lattice points closest to a direction intersecting the reference direction at an angle of 63.4 ° from the reference point as a fourth measurement point;
Output means for outputting an instruction to measure each distance between the reference point and each of the measurement target points set by the setting means to the display unit;
A calculation means for calculating a distortion amount in each direction determined by the reference point and each of the measurement target points based on the distance measured using the measurement unit and the pitch after the output by the output means; Including a strain measuring device. Maximum principal distortion acquisition means for acquiring the maximum value of the distortion amounts calculated by the calculation means as the maximum principal distortion;
An instruction to output a distance measurement instruction between the reference point and the lattice point located in a direction orthogonal to the direction of the maximum principal strain acquired by the acquisition unit with respect to the reference point is output to the display unit. Two output means;
2. The minimum principal distortion acquisition unit according to claim 1, further comprising: a minimum principal distortion acquisition unit that acquires a minimum principal distortion by calculation based on a distance measured using the measurement unit after the output by the second output unit. Strain measuring device. Display grid points arranged in a matrix at the same pitch in the row and column directions on the surface of the metal plate,
After press forming the metal plate on which the lattice points are displayed,
One of the lattice points is used as a reference point, and the lattice point closest to the predetermined reference direction from the reference point is used as a first measurement target point, and intersects the reference direction from the reference point at an angle of 45 °. The lattice point closest to the direction is set as the second measurement target point, and the lattice point closest to the direction intersecting the reference direction at an angle of 26.5 ° from the reference point is set as the third measurement target point. As a fourth measurement target point, each of the lattice points closest to the direction intersecting the reference direction at an angle of 63.4 degrees from the reference point ,
Using a measuring device, manually measure each distance between the reference point and each of the measurement target points, to obtain a strain amount in each direction determined by the reference point and each of the measurement target points, Strain measurement method.

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