JP2020165875A - Method for measuring size, size measuring device, automatic tension test device, and method for evaluating bearing force - Google Patents

Abstract

To increase the evaluation of a tension test by increasing the accuracy of measuring the size of a test piece.SOLUTION: The parallel part of a test piece 100 is pressed vertically by a pair of indenters 15 while the parallel part of the test piece 100 is being grasped by a pair of grasping devices 14. After that, the grasping of the test piece 100 by the pair of grasping devices 14 is loosened and then the thickness of the test piece is measured by the pair of indenters 15. The stop position of the pair of indenters 15 is determined by an edge sensor 21 and the thickness of the test piece, and the width of the parallel part of the test piece 100 is measured.SELECTED DRAWING: Figure 14

Description

The present invention relates to a tensile test technique for a metallic material. In particular, it is a technique suitable for an automatic tensile test device.

The automatic tensile test device includes, for example, a stocker for setting a test piece, a robot for transporting the test piece, a dimension measuring device for measuring the width and thickness of parallel portions in the test piece, and a testing machine main body for performing a tensile test. And a tensile tester with an automatic extensometer. Then, the characteristic values for evaluation (yield strength, tensile strength, total elongation, etc.) are obtained from the width and thickness of the parallel portion measured by the dimension measuring device and the elongation-load characteristic acquired by the tensile test apparatus. Then, the pass / fail judgment is made by comparing the obtained characteristic value with the pass / fail judgment criterion. In addition, the fracture position is estimated from the fractured pieces after the tensile test.

As a conventional technique relating to an automatic tensile test apparatus, there are, for example, Patent Document 1 and Patent Document 2.
Patent Document 1 discloses a method for efficiently performing a series of operations from supply of a test piece to removal of a measured test piece.
Further, Patent Document 2 has a problem that the test piece cannot be reliably set in the tensile test clamp of the testing machine body unless the test pieces having different shapes are classified into the test piece cases suitable for each shape. On the other hand, a method has been disclosed in which, by using a photosensor as a test piece shape detection mechanism, even one type of test piece case can be reliably set up to a tensile test clamp for test pieces having different shapes. There is.

Further, in Patent Document 3, in a state where the test piece is attached to the chuck portion of the tensile tester, the parallel portion of the test piece is brought into contact with a measuring element from the direction orthogonal to the parallel portion, or is not contacted by wave motion or optical means. The method of measuring with is disclosed.

JP-A-5-240756 JP-A-8-193932 Japanese Unexamined Patent Publication No. 56-4033

The test piece for the tensile test is manufactured by cutting to a predetermined size defined by JIS standards and overseas standards. At this time, the test piece after cutting may be twisted or warped in the longitudinal direction.
In the test piece dimension measuring device in the conventional automatic tensile test device, both ends of the test piece are grasped by a chuck or the like, and the width and thickness of the test piece parallel portion are measured by a pair of measuring rollers. If the test piece has distortion such as twisting or warping, even the amount of distortion will be measured as the size of the test piece, and the measured value will deviate from the dimensional tolerance, the position of the test piece will deviate from the reference point of the sensor, and measurement will not be possible. There was a problem such as.

For this reason, in the past, a test piece having a twist or warp of a predetermined value or more had to be excluded from the dimensional measuring device and measured manually, which was a major factor in lowering the automation rate. ..
If the dimensional tolerance is not deviated, the tensile test is automatically performed, but the width and thickness of the test piece have an error due to the above strain, which causes an error in the test result.

Further, when a test piece having a twist or warp is pulled, the stress-strain curve may not be uniformly deformed and may fluctuate in the proportional portion (elastic region of the rise of the elongation-load characteristic). For test pieces that do not show a yield phenomenon, the system automatically calculates the yield strength from the slope of the proportional part of the stress-strain curve based on the offset method specified in JIS Z2241 or the total elongation method, but it is proportional when fluctuations occur. There is also the problem that the slope of the part cannot be calculated properly, and if the wrong slope line is used, the wrong yield strength is measured and the wrong test value calculated using the wrong proportional part slope is leaked. there were. This has also been a factor in reducing the reliability of automatic tensile tests.

The present invention has been made by paying attention to the above points, and an object of the present invention is to improve the reliability of an automatic tensile test by improving the accuracy of dimensional measurement of a test piece.

In order to solve the problem, the dimension measuring device according to one aspect of the present invention measures the thickness and width of the parallel portion based on the distance between the pair of indenters in contact with the parallel portion of the test piece to be subjected to the tensile test. A dimension measuring device for measuring, which can hold a pair of left and right gripping devices for gripping both ends of a test piece placed on a stand in the longitudinal direction and parallel portions of the test piece from the thickness direction and the width direction. The pair of indenters and the edge sensor including an edge sensor capable of detecting a parallel portion edge of the test piece and a dimensional control unit for controlling the operation of the gripping device and the indenter are provided. It is configured to approach and separate the test pieces supported by the pair of gripping devices, and the dimension control unit grips both ends of the test piece placed on the pedestal with the pair of gripping devices. The test piece support portion that supports the test piece with the thickness direction oriented vertically or horizontally and the parallel portion of the test piece supported by the pair of gripping devices are supported by the pair of indenters in the thickness direction or the width direction. When it is determined that the indenter sandwiching portion to be sandwiched from the indenter and the parallel portion of the test piece supported by the pair of gripping devices are sandwiched by the pair of indenters, the gripping relaxation to ease the gripping of the test piece by the pair of gripping devices is performed. When it is determined that the gripping relaxation section has relaxed the grip of the test piece, the thickness measuring section for determining the thickness with the pair of indenters and the position where the edge of the parallel portion of the test piece is detected by the edge sensor are used as a reference. If it is determined by the indenter position control unit that stops the approach of the pair of indenters and the indenter position control unit that the pair of indenters has stopped based on the thickness of the test piece, the width of the parallel portion is determined by the pair of indenters. The gist is to provide the desired width measurement unit.

Further, the dimensional measurement method according to one aspect of the present invention measures the thickness and width of the parallel portion based on the distance between a pair of indenters that abut in the parallel portion of the test piece to be subjected to the tensile test in the measurement direction. According to the method, the thickness of the test piece is such that both ends of the test piece are gripped by a pair of gripping devices, and the test piece is supported with the thickness direction of the parallel portion facing up and down. Later, the parallel portion was sandwiched between the pair of indenters from above and below, and then determined based on the distance between the pair of indenters when the gripping of the test piece by the pair of gripping devices was relaxed, and the width of the test piece was obtained. Is to stop the indenter at the edge detection position of the test piece by the edge sensor and the indenter holding position obtained from the test piece thickness, hold the test piece with the indenter from the width direction of the test piece, and obtain the value based on the distance between the indenters. And.

Further, the automatic tensile test device according to one aspect of the present invention includes a robot hand for transporting a test piece, a dimension measuring device for measuring the width and thickness of parallel portions in the test piece, and a test for measuring the width and thickness. A tensile test device that performs a tensile test on a piece to obtain elongation-load characteristics, and a test piece that has been tested based on the width and thickness obtained by the dimension measuring device and the elongation-load characteristics acquired by the tensile test device. It has an arithmetic device for calculating stress-strain characteristics, and the gist is that the dimension measuring device is the dimension measuring device of one aspect of the present invention.

Further, in the proof stress evaluation method which is one aspect of the present invention, the width and thickness of the parallel portion in the test piece are measured by using the above-mentioned dimension measurement method, and the tensile test of the test piece whose width and thickness are measured is performed to extend the test piece. -Obtain the load characteristics, calculate the stress-strain characteristics from the measured width and thickness and the above elongation-load characteristics, and the Young's modulus calculated from the stress-strain characteristics is the Young's modulus assumed in the test piece tested. The gist is to judge the pass / fail of the test result based on whether or not the rate is within the preset control range.

According to the aspect of the present invention, even if the test piece has distortion such as twisting or warping, the size of the test piece can be measured with high accuracy.
Further, according to the aspect of the present invention, it is possible to eliminate inappropriate test results due to the shape of the test piece by incorporating a mechanism for determining the suitability of the inclined line (Young's modulus), which is important for determining the yield strength. Therefore, it has the effect of increasing the reliability of the automatic tensile test.

It is a top view explaining the structural example of the automatic tensile test apparatus. It is a front view explaining the 1st centering mechanism and the gripping device. It is a front view explaining the 2nd centering mechanism and the gripping device. It is a perspective view which shows the 2nd centering mechanism. It is a top view which shows the relationship between the test piece and the initial value of an indenter. It is a side view which shows a pair of indenters and an edge sensor. It is a figure explaining the structure of the dimension control part. It is a flow figure explaining the process of a thickness measurement control part. It is a process flow diagram explaining the grip relaxation part. It is a flow figure explaining the process of a width measurement control part. It is a figure explaining the process of the indenter position resetting part. It is a figure explaining the structure of a control device. It is a flow chart explaining the process of an evaluation part. It is a conceptual diagram (front view) explaining the thickness measurement. It is a conceptual diagram (front view) explaining the thickness measurement. It is a conceptual diagram (front view) explaining the thickness measurement. It is a conceptual diagram (plan view) for explaining width measurement. It is a figure which shows the example which the Young's modulus (inclination line) is blurred.

Next, an embodiment of the present invention will be described with reference to the drawings. The drawings described below show a preferred example of the present invention, and the present invention is not limited to the drawings. The embodiments of the present invention can be appropriately modified within a range suitable for the gist of the present invention, and all of them are included in the technical scope of the present invention.
As shown in FIG. 1, the automatic tensile test device of the present embodiment includes a stocker 1 for setting a test piece, a robot 2 for transporting the test piece, and a dimension measuring device for measuring the dimensions of parallel portions of the test piece. 3. It is provided with a tensile test device 4 for performing a tensile test and acquiring elongation-load characteristics, and a control device 5.

<Stocker 1>
The stocker 1 is a facility for arranging test pieces to be used for the automatic tensile test of the present application. The test pieces are set in the stocker 1 in the order of testing, either horizontally or stacked. It is preferable to attach the test piece information such as a barcode for reading the information such as the sample identification symbol, the steel type, the nominal thickness, and the assumed Young's modulus into the control device.

<Robot 2>
The robot 2 is composed of a 6-axis robot or the like, and the robot hand grips the test piece placed on the stocker 1 and conveys the test piece to the stand of the dimensional measurement device 3, or measures the test piece after the dimensional measurement. It is a device that is transported from the device 3 to the tensile test device 4 and installed. As the robot 2, a known industrial robot as described in Patent Document 2 may be used.

<Tensile test device 4>
The tensile test device 4 includes a tensile tester main body 4A for performing a tensile test and an automatic extensometer 4B for measuring the elongation of a test piece installed in the tensile tester main body 4A.
The test piece whose dimensions have been measured by the dimension measuring device 3 is conveyed to the tensile tester main body 4A by the robot 2 and attached between the upper chuck and the lower chuck of the tensile tester main body 4A. Further, a pair of arms 4Ba of the automatic extensometer 4B are gripped to measure the scoring distance of the test piece. The tensile test device 4 measures the elongation of the parallel portion of the test piece with the automatic extensometer 4B in synchronization with applying a tensile load in the tensile axis direction to the test piece by the tensile tester main body 4A. .. As a result, the tensile test device 4 continuously and continuously measures the measured values (strain amount (ε), load (N)) for the elongation-load characteristic and supplies the measured values to the control device 5. As the tensile test device 4, a known tensile test device may be adopted.

<Dimension measuring device 3>
The dimension measuring device 3 measures the thickness and width of the parallel portion of the test piece. The thickness and width of the parallel portion are the cross-sectional information of the test piece.
As shown in FIGS. 2 to 6, the dimension measuring device 3 of the present embodiment includes a stand 10, a centering mechanism, a pair of left and right gripping devices 14, a pair of indenters 15, an edge sensor 21, and dimensions. It includes a control unit 22.

(Stand 10)
As shown in FIG. 2, the stand 10 is a stand on which the test piece 100 is placed. The height of the stand 10 can be changed between an initial value height position and a shunting position below the initial height position by an elevating mechanism 11 including a cylinder device and the like.
(Centering mechanism)
The centering mechanism is a mechanism for positioning the position of the test piece 100 mounted on the stand 10 at the target mounting position when viewed from a plan view. The centering mechanism includes a first centering mechanism 12 and a second centering mechanism 13.

The first centering mechanism 12 is a mechanism for sandwiching the test piece 100 placed on the pedestal 10 from both sides in the longitudinal direction in synchronization with each other to align the longitudinal position of the test piece 100 with a preset position.
As shown in FIG. 2, the first centering mechanism 12 of the present embodiment has a pair of pressing pads 12a capable of facing each other by sandwiching the test piece 100 mounted on the stand 10 from the longitudinal direction, and a pair thereof. A synchronous displacement mechanism 12b for synchronously approaching and detaching the pressing pads 12a and an elevating mechanism 12c for raising and lowering the pair of pressing pads 12a are provided.

The height of the pair of pressing pads 12a is lower than the centering height position facing the longitudinal end surface of the test piece 100 placed on the stand 10 and the centering height position by the operation of the elevating mechanism 12c. It is possible to switch to the save position (initial position).
Then, when the first centering mechanism 12 receives the operation command from the dimension control unit 22, the elevating mechanism 12c operates and the height of the pair of pressing pads 12a moves to the centering height position. Subsequently, when it is determined that the height of the pair of pressing pads 12a is at the centering height position, the synchronous displacement mechanism 12b is activated, the pair of pressing pads 12a approach each other, and the pair of pressing pads 12a By sandwiching the test piece 100, the test piece 100 is centered in the longitudinal direction, and then the pair of pressing pads 12a are separated again. Subsequently, by the operation of the elevating mechanism 12c, the pair of pressing pads 12a descend toward the shunting position.

The second centering mechanism 13 is a mechanism for sandwiching the test piece 100 placed on the stand 10 in synchronization from both sides in the width direction and aligning the width direction position of the test piece 100 with a preset position.
As shown in FIGS. 3 and 4, the second centering mechanism 13 of the present embodiment has a pair of rods facing each other with the test piece 100 placed on the stand 10 sandwiched from the width direction in a plan view. It is provided with a synchronous displacement mechanism that synchronously approaches and separates the body 13a and the pair of rods 13a, and an elevating mechanism 13c that raises and lowers the pair of rods 13a. The height of the pair of rods 13a is the centering height position facing the test piece 100 placed on the stand 10 from the width direction and the shunting below the centering height position by the operation of the elevating mechanism 13c. It is possible to switch to the position (initial position).

Then, when the second centering mechanism 13 receives the operation command from the dimension control unit 22, the elevating mechanism 13c operates, the height of the pair of rods 13a moves to the centering height position, and the pair is formed. When it is determined that the height of the rods 13a is the centering height position, the paired rods 13a approach each other (see FIG. 5), position the test piece 100 in the width direction, and then pair again. The rod body 13a is separated. Subsequently, by the operation of the elevating mechanism 13c, the pair of rods 13a descends toward the shunting position.

(Gripping device 14)
The pair of left and right gripping devices 14 are devices for gripping both ends of the test piece 100 placed on the stand 10 in the longitudinal direction.
As shown in FIGS. 2 and 3, each of the left and right gripping devices 14 has a pair of gripping portions 14A and 14B capable of sandwiching the end portions of the test piece 100. The pair of grip portions 14A and 14B are supported by the first slider portion 14C in a state where the pair of grip portions 14A and 14B can be approached and detached from each other. The first slider portion 14C has a rotation shaft 14D extending in the lateral direction. The rotating shaft 14D is supported by the vertical portion of the L-shaped frame 14F, and can be rotated by the rotating drive portion 14E. Then, by rotationally displacement around the rotation shaft 14D, the pair of grip portions 14A and 14B are located at the initial position facing each other in the vertical direction and the second position facing each other in the left-right direction rotated by 90 degrees with the longitudinal direction as the rotation axis. Two opposite positions can be taken.

A second slider portion 14G is provided on the horizontal portion of the L-shaped frame 14F. The second slider portion 14G is set so that the L-shaped frame 14F can move toward and apart from the longitudinal end of the test piece 100 placed on the stand 10.
With this configuration, the pair of left and right gripping devices 14 operate in synchronization with the command from the dimension control unit 22, and the pair of gripping portions 14A and 14B are operated by the second slider portion 14G in the longitudinal direction of the test piece 100. The pair of grips 14A and 14B face each other with the longitudinal end of the test piece 100 in between, and then the first slider 14C approaches and the pair of grips 14A and 14B approach each other. Then, the end portion of the test piece 100 is sandwiched from above and below, and the test piece 100 is gripped in the vertical direction in the thickness direction. At this time, the stand 10 is retracted downward. As a result, the pair of left and right gripping devices 14 can horizontally support the test piece 100.

Further, when the rotation drive unit 14E is operated, the pair of grip portions 14A and 14B are rotated by 90 degrees so as to be in positions facing each other in the left-right direction, and the width directions of the test piece 100 are in positions facing each other in the vertical direction.
(Pair Indenter 15) As shown in FIG. 5, the initial value of the pair of indenters 15 is a position separated in the width direction of the test piece 100 placed on the stand 10 in a plan view.

As shown in FIG. 6, the pair of indenters 15 are arranged so as to face each other in the vertical direction, and are attached to the pair of upper and lower chuck portions 16, respectively. A digital gauge 17 is attached to the upper chuck portion 16 with the shaft facing up and down, and the distance between the pair of indenters 15 can be measured by the digital gauge 17.
The lower chuck portion 16 can be displaced up and down by the elevating mechanism 19, and the distance between the pair of indenters 15 changes due to the displacement of the lower indenter 15 due to the elevating and lowering of the lower chuck portion 16. In addition, the holding pressure when the test piece 100 is held by the pair of indenters 15 can be adjusted. As a result, the pair of indenters 15 have a configuration in which parallel portions of the test piece can be sandwiched from the thickness direction and the width direction.

The pair of chuck portions 16 provided with the pair of indenters 15 are supported by the vertical portions of the L-shaped member 18, and the horizontal portions of the L-shaped member 18 are attached to the XY table 20. The XY table 20 allows the L-shaped member 18, that is, the pair of indenters 15, to move in the direction of approaching and detaching from the test piece 100, and also in the direction along the longitudinal direction of the test piece 100. It is movable. As a result, the pair of indenters 15 are configured to approach and separate the test pieces supported by the pair of gripping devices.

(Edge sensor 21)
An edge sensor 21 is provided on the front side of the upper indenter 15 in the upper chuck portion 16. As a result, the edge sensor 21 is configured to approach and separate the test pieces supported by the pair of gripping devices. The edge sensor 21 of the present embodiment includes, for example, a laser range finder. In the edge sensor 21, the detection direction is set downward, which is the opposite direction of the pair of indenters 15. As a result, when the test piece 100 relatively enters the tips of the pair of chuck portions 16 and the test piece 100 comes to the position of the edge sensor 21 in a plan view, the distance detected by the laser range finder becomes shorter. , The edge of the parallel portion of the test piece 100 can be detected.

(Dimension control unit 22)
As shown in FIG. 7, the dimension control unit 22 includes a thickness measurement control unit 22A and a width measurement control unit 22B. The dimension control unit 22 is composed of a computer program.
(Thickness measurement control unit 22A)
As shown in FIG. 8, the thickness measurement control unit 22A includes a first centering processing unit, a second centering processing unit, a test piece support unit 22Aa, an indenter holding unit 22Ab, a grip relaxation unit 22Ac, and a thickness measuring unit. It has 22 Ad.

Next, the processing of the thickness measurement control unit 22A will be described with reference to FIG.
In step S200, it is determined whether or not the test piece 100 is placed on the stand 10. If it is determined that the vehicle has been placed, the process proceeds to step S201.
In step S201, the first centering processing unit is activated, and the first centering mechanism 12 performs the centering processing in the longitudinal direction of the test piece 100 placed on the stand 10.

Next, in step S202, the second centering processing unit is activated, and the second centering mechanism 13 performs centering processing in the width direction of the test piece 100 placed on the stand 10.
Next, in step S203, the test piece support portion 22Aa is activated.
The test piece support portion 22Aa supplies an operation command to the pair of gripping devices 14 to grip both ends of the test piece 100 placed on the stand 10 by the pair of gripping devices 14, and the pair of gripping devices 14 , The test piece 100 is supported in a state where the thickness direction is directed in the vertical direction. At this time, if it is determined that the pedestal 10 has been gripped, the pedestal 10 is displaced downward.

When it is determined that the parallel portion of the test piece 100 is supported by the pair of gripping devices 14 by the operation of the test piece support portion 22Aa, the process proceeds to step S204 to activate the indenter holding portion 22Ab.
Here, the indenter sandwiching portion 22Ab performs a process of sandwiching the parallel portions of the test pieces supported by the pair of gripping devices with the pair of indenters from the thickness direction or the width direction.
The indenter holding portion 22Ab supplies an operation command to the pair of indenters 15 to move the pair of indenters 15 to positions facing the upper surface side and the lower surface side with the parallel portion of the test piece 100 interposed therebetween. Since the initial position of the indenter 15 and the distance to the test piece 100 are constant, the indenter 15 may be moved by the constant distance. Subsequently, the pair of indenters 15 facing each other in the vertical direction are brought close to each other, and the parallel portion of the test piece 100 supported by the pair of gripping devices 14 is sandwiched by the pair of indenters 15 from above and below with a predetermined sandwiching pressure.

At this time, the holding pressure between the pair of indenters 15 is set to 0.2 MPa or more.
The reason is that if the pinching pressure is lower than 0.2 MPa, the pinching of the test piece described later becomes unstable, and the thickness of the test piece cannot be measured accurately. There is no particular upper limit of the pinching pressure as long as the pinching is stable, but the pinching pressure is preferably 0.7 MPa or less in order to reduce the load on the gripping device 14.

Further, the area of the contact surface with the test piece 100, which is the tip of each indenter 15, is 40 mm ² or more and 250 mm ² or less.
In order to improve the thickness measurement accuracy, it is preferable that the tip of the indenter makes point contact with the test piece, but the smaller the contact area, the more unstable the pinching of the test piece described later. Therefore, the area of the contact surface with the test piece 100 is set to 40 mm ² or more and 250 mm ² or less. More preferably, it is 78 mm ² or more and 200 mm ² or less. The shape of the indenter contact surface is preferably a circular shape or an isotropic polygonal shape.

The process proceeds to step S205, which determines that the test piece 100 is sandwiched between the pair of indenters 15, and the grip relaxation unit 22Ac is activated.
In the gripping relaxation unit 22Ac, as shown in FIG. 9, the weight of the test piece 100 is acquired in step S300. The weight of the test piece 100 is obtained, for example, by reading the test piece information such as a bar code provided on the test piece 100.

Next, the process proceeds to step S301 to determine whether or not the weight of the test piece 100 is less than the threshold weight.
If the weight is less than the threshold weight, the process proceeds to step S302, and both of the pair of grips 14A and 14B supporting the test piece 100 are displaced in the direction away from the test piece 100, respectively. When it is determined that the weight of the test piece 100 is equal to or greater than the preset threshold weight, the process proceeds to step S303, and only the upper grip portion 14A of the pair of grip portions 14A and 14B supporting the test piece 100 is displaced upward. This relaxes the grip of the test piece 100.

The gripping relaxation unit 22Ac displaces both of the pair of gripping portions 14A and 14B supporting the test piece 100 in a direction away from the test piece 100, regardless of the weight of the test piece 100, to grip the test piece 100. It may be a relaxed configuration. Further, the grip relaxing portion 22Ac is configured to relax the grip of the test piece 100 by displacing only the upper grip portion 14A of the pair of grip portions 14A and 14B supporting the test piece 100 upward. You may.

When it is determined that the gripping relaxation unit 22Ac has relaxed the grip of the test piece 100, the process proceeds to step S206 to activate the thickness measuring unit 22Ad.
The thickness measuring unit 22Ad measures the distance between the pair of indenters 15 as the thickness of the test piece 100, and stores it in the thickness measuring control unit.
Here, by repeating the processes of steps S204 to S206 while shifting the measurement position in the parallel portion in the length direction, the thickness of the parallel portion at a plurality of locations can be measured. When measuring the thickness of multiple points, the average value is calculated and used as the thickness of the test piece.

Next, the process proceeds to step S207 to start the re-support processing unit.
In the re-support processing unit, an operation command is supplied to the pair of gripping devices 14, and both ends of the test piece 100 placed on the stand 10 are gripped by the pair of gripping devices 14.
Next, the process proceeds to step S208 to start the indenter return processing unit.
The indenter return processing unit releases the sandwiched state by separating the pair of indenters 15 from each other, and laterally moves the indenter 15 to the initial position.

(Width measurement control unit 22B)
Next, the process of the width measurement control unit 22B will be described with reference to FIG.
As shown in FIG. 10, the width measurement control unit 22B includes a test piece rotational displacement unit 22Ba, an indenter position resetting unit 22Bb, and a width measurement unit 22Bc.
The processing of the width measurement control unit 22B operates when the processing of the thickness measurement control unit 22A is completed.

First, in step S400, the test piece rotational displacement portion 22Ba is activated.
The test piece rotational displacement portion 22Ba supplies an operation command for rotational displacement to the pair of gripping devices 14, causes the pair of grip portions 14A and 14B to be rotationally displaced by 90 degrees, and the pair of grip portions 14A and 14B face each other on the left and right sides. Set to the desired position. In this state, the width direction of the gripped test piece 100 faces up and down.

Next, in step S401, the indenter position resetting unit 22Bb is activated. The indenter position resetting unit 22Bb constitutes an indenter position control unit that stops the approach of a pair of indenters based on the distance obtained from the thickness of the test piece, based on the position where the edge of the parallel portion of the test piece is detected by the edge sensor. To do. As shown in FIG. 11, the indenter position resetting unit 22Bb first starts forward movement of the indenter 15 toward the test piece 100 in step S500.

Then, it is determined in a predetermined sampling cycle whether or not the edge sensor 21 has detected the edge of the test piece 100 (step S501), and if it is determined that the edge is detected, after the advance time determined based on the test piece thickness elapses, The advance of the indenter 15 is stopped (step S502). Here, as the test piece thickness, the test piece thickness set in advance as the test piece information can be used, but the test piece thickness obtained in the above steps S204 to S206 can also be used. The advancing time is the time required to advance the distance from the edge to the position where the test piece can be opposed (for example, 1/2 position in the thickness direction), which is obtained from the thickness of the test piece and the moving speed of the indenter.

Next, the process proceeds to step S402 to start the width measuring unit 22Bc. In the width measuring unit 22Bc, the pair of stopped indenters 15 are brought close to the test piece, and the pair of indenters 15 sandwich the test piece 100 from the width direction. This holding pressure may be small.
When the test piece 100 is sandwiched by the indenter 15, the width measuring unit 22Bc measures the distance between the pair of indenters 15 as the width of the test piece 100 and stores it in the width measurement control unit 22B.

Next, the process proceeds to step S403, the indenter return unit is activated, the test piece 100 is released from being pinched by the indenter 15, and the pair of indenters 15 are returned to the initial positions.
Here, by changing the measurement position and repeating steps S401 to S403 a plurality of times, the widths of the parallel portions at a plurality of locations can be measured. When measuring the width of multiple points, the average value is calculated and used as the width of the test piece.

After that, the process proceeds to step S404 to activate the grip release unit.
The grip release portion returns the pedestal 10 that has been shunted downward to the initial position, and releases the grip by the pair of grip devices 14.
Here, when the test piece thickness set in advance is used in step S401, the dimension control unit 22 changes the order of the thickness measurement control steps S203 to S208 and the width measurement control steps S400 to S404 after the second centering process. It can also be carried out.

<Control device 5>
As shown in FIG. 12, the control device 5 includes an elongation-load characteristic acquisition unit 5A, a calculation unit 5B, and an evaluation unit 5C.
The elongation-load characteristic acquisition unit 5A acquires cross-sectional information consisting of the width and thickness of the parallel portion from the dimension measuring device 3, and the characteristic information of the elongation-load characteristic (strain amount ε, tensile load N) from the tensile test device 4. To get.

Then, the calculation unit 5B obtains the cross-sectional area of the parallel portion of the test piece 100 from the width and thickness of the parallel portion, and the tensile load N of each (strain amount ε, tensile load N) which is information on the elongation-load characteristic. Is divided by the cross-sectional area A of the parallel portion and converted into a stress value σ to obtain a plurality of characteristic information consisting of a set of (strain amount ε, stress σ).
The process of the evaluation unit 5C will be described with reference to FIG.

The evaluation unit 5C first estimates the elastic region from the slope Δσ / Δε of the stress-strain characteristic from the calculation unit 5B in step S600, then obtains the slope straight line in step S601, and calculates the Young's modulus from the slope of this straight line. get. The inclination straight line can be obtained, for example, by selecting any two points in the elastic region and as the slope of the straight line connecting the two points. Alternatively, a plurality of points can be arbitrarily selected and can be obtained by linear approximation by the least squares method or the like.

The process of step S601 constitutes the Young's modulus acquisition unit.
Next, in step S602, it is determined whether or not the Young's modulus obtained in step S601 is within the control range set in advance as test piece information. If it is determined that it is within the control range, the process proceeds to step S603, and if it is determined that it is outside the control range, the process proceeds to step S604.
The control range is composed of an upper limit value and a lower limit value of Young's modulus of the steel material constituting the test piece 100. Within this control range, it may be set as a theoretical value, or the Young's modulus obtained in the past may be statistically set.

In step S603, the test result for determining that Young's modulus is within the above control range is determined to be acceptable, and the offset method, onset method, or total elongation method specified in JIS Z2241 is determined from the slope straight line of the stress-strain characteristic. Calculate the yield strength based on. Further, other characteristic values such as tensile strength and total elongation are obtained.
On the other hand, in step S604, if the value of the counter is equal to or less than a predetermined count value (for example, 3), the process proceeds to step S600 and is estimated to be an elastic region from the calculation unit 5B for acquiring the differential value of the stress-strain characteristic. The characteristic information of the combination of the above two is acquired, and the above evaluation is repeated.

On the other hand, if the value of the counter exceeds the predetermined count value in step S604, the process proceeds to step S605, and the evaluation of Young's modulus is rejected (the test piece 100 cannot be adapted). The counter is cleared to zero when the evaluation unit 5C starts up.

(Operation and others)
In the tensile test, it is necessary to process the test piece 100 to a predetermined size, but in reality, the product is subjected to various strains in the manufacturing process, and the test piece 100 is warped in the longitudinal direction after cutting the sample material. Or, a twist may occur around the longitudinal direction. Conventionally, in the test piece 100 having a warp or a twist, the measurement result of the test piece 100 may show an abnormal value. Then, it was necessary to stop the device and remove the test piece 100 from the test device because it was impossible to measure with the conventional automatic tensile test device. If it is removed, the measurement is performed manually, the dimensional measurement value of the test piece 100 is manually input to the testing machine terminal, and then the automatic tensile test is performed, which is a major factor in lowering the automation rate.

In the present embodiment, even when the test piece 100 is twisted and distorted in the longitudinal direction, the pair of indenters 15 are in point contact with the test piece 100 with a force sufficient to support the weight of the test piece 100. If it is possible to measure while gripping with only the indenter, the weight of the test piece 100 that can be supported only by the indenter 15 of the dimension measuring device 3 is verified from the idea that the measurement can be performed correctly without including the measurement error due to twisting. I confirmed it.

That is, in the present embodiment, as shown in FIG. 14A, the test piece 100 is sandwiched between the pair of indenters 15, and then as shown in FIG. 14B, the pair of gripping portions of the pair of gripping devices 14 14A and 14B are displaced up and down, and the thickness is measured with the pair of gripping devices 14 released.
At this time, if the test piece 100 is twisted, the thickness of the test piece is measured by the pair of indenters 15 while the test piece 100 is gripped by the pair of gripping devices 14 (FIG. 14A). As shown in FIG. 16A, since the test piece 100 is sandwiched between the pair of test pieces 100 in an inclined state, the measurement is made larger than the original size.

On the other hand, when the gripping of the test piece 100 by the pair of gripping devices 14 is relaxed (FIG. 14 (b)) and the pair of indenters 15 sandwich the test piece 100 with a holding pressure equal to or higher than a predetermined pressure, FIG. 16 (b) shows. As described above, at the measurement position of the test piece 100, the posture of the test piece 100 is displaced horizontally with respect to the contact surface of the indenter 15, and the thickness of the test piece can be measured correctly.
If it is not possible to grip with only the pair of indenters 15, as shown in FIG. 15B, the grips 14A and 14B on both sides are supported only by the lower grips 14B, and the upper grips 14A are open and free. It was confirmed that the measurement can be performed without being affected by the twist if the end is in the state of the end. That is, even if the test piece 100 having a weight equal to or greater than a predetermined value is twisted, the thickness can be measured with high accuracy.

Further, when considering the measurement in the width direction of the test piece 100, if the test piece 100 is warped, the parallel portion of the test piece 100 is curved as shown in FIG. In this way, the distance from the initial position of the indenter 15 to the parallel portion of the test piece 100 changes depending on the warp. Therefore, in the method of moving the indenter 15 by a certain distance, the indenter stops in front of or behind the position of the test piece. Therefore, there was a risk that the width could not be measured.

On the other hand, in the present embodiment, the edge sensor 21 is used, and after the edge sensor 21 detects the edge portion of the parallel portion of the test piece 100 on the curved line, the indenter is determined after a predetermined time determined by the test piece thickness and the indenter moving speed. I am trying to stop the advance of 15. Therefore, no matter what kind of warp is formed in the test piece 100, the indenter can stop at the position of the test piece and grip the test piece, so that the width of the test piece 100 can be measured.

Further, by positioning based on the thickness of the test piece 100, the accuracy of the pinching position by the indenter is improved, and the dimensional measurement accuracy is improved.
Also, if the warp and twist are small, the elastic region of the stress-strain curve is not affected and the characteristic value is not affected, but if the warp and twist are large, the elastic region of the stress-strain curve becomes straight. However, since the rising slope fluctuates, the Young's modulus value estimated from the steel grade of the test piece is often not obtained. Therefore, for example, the measurement result of 0.2% offset proof stress (stress value at the position where the slope line in the proportional region of the stress-strain curve is translated by 0.2% in the direction of increasing strain and intersects the stress-strain curve). However, it may become an abnormal value. In the conventional automatic tensile test apparatus, it is necessary to determine the above abnormal value and exclude it from the test result.

Young's modulus is a slope Δσ / Δε obtained from characteristic information (ε, σ) measured at any two measurement points or three or more points in the proportional portion (elastic region) of the stress-strain curve, and is shown in FIG. As described above, when there is fluctuation in the elastic region, the value of Young's modulus differs greatly depending on which combination of measurement points is adopted.
In consideration of such a thing, in the present embodiment, the accuracy of the obtained Young's modulus is improved by performing an aptitude evaluation as to whether or not the obtained Young's modulus is within the control range.

For example, the Young's modulus control range is set in advance from the past test results of various materials, and it is automatically verified whether the Young's modulus obtained from an arbitrarily designated measurement point is within the set control range. If the Young's modulus obtained here is out of the range, check whether the specified measurement point was appropriate on the stress-strain curve as necessary, specify another measurement point again if necessary, and more. We built a mechanism to set an appropriate slope line. As a result, it has become possible to measure the yield strength with higher reliability than before.

As described above, in the present embodiment, the dimensions can be measured correctly even if the actual test piece 100 is twisted or warped, and the suitability of the inclination line (Young's modulus), which is important for determining the proof stress, is appropriate. By determining, more accurate proof stress measurement becomes possible. As a result, it has the effect of increasing the reliability of the test.

3 Dimension measuring device 4 Tension test device 5 Control device 5A Elongation-load characteristic acquisition unit 5B Calculation unit 5C Evaluation unit 10 Stand 12 1st centering mechanism 13 2nd centering mechanism 14 Gripping device 14A, 14B Gripping part 15 Indenter 21 Edge sensor 22 Dimension control unit 22A Thickness measurement control unit 22Aa Test piece support unit 22Ab Indenter holding unit 22Ac Grip relaxation unit 22Ad Thickness measurement unit 22B Width measurement control unit 22Ba Test piece rotation displacement unit 22Bb Indenter position resetting unit (indenter position control unit)
22Bc width measuring unit 100 test piece

Claims (12)

A dimensional measuring device that measures the thickness and width of the parallel portion based on the distance between the pair of indenters that are in contact with the parallel portion of the test piece to be subjected to the tensile test.
A pair of left and right gripping devices that grip both ends of the test piece placed on the pedestal in the longitudinal direction,
A pair of indenters capable of sandwiching the parallel portion of the test piece from the thickness direction and the width direction,
With an edge sensor that can detect the parallel edge of the test piece,
The gripping device and the dimension control unit for controlling the operation of the indenter are provided.
The pair of indenters and the edge sensor are configured to approach and separate the test piece supported by the pair of gripping devices.
The above dimension control unit
A test piece support portion in which both ends of the test piece placed on the stand are gripped by the pair of gripping devices and the test piece is supported in a state where the thickness direction is vertically or horizontally.
An indenter holding portion for holding the parallel portion of the test piece supported by the pair of gripping devices from the thickness direction or the width direction with the pair of indenters.
When it is determined that the parallel portion of the test piece supported by the pair of gripping devices is sandwiched between the pair of indenters, the gripping relaxation portion for relaxing the gripping of the test piece by the pair of gripping devices,
When it is determined that the gripping relaxation unit has relaxed the grip of the test piece, the thickness measuring unit for obtaining the thickness with the pair of indenters and the thickness measuring unit
An indenter position control unit that stops the approach of the pair of indenters based on the thickness of the test piece, based on the position where the edge of the parallel portion of the test piece is detected by the edge sensor.
When the indenter position control unit determines that the pair of indenters has stopped, the width measuring unit for obtaining the width of the parallel portion with the pair of indenters
A dimensional measuring device characterized by comprising. The dimensional measuring device according to claim 1, wherein the gripping relaxation unit relaxes the gripping of the test piece by releasing the support of the test piece by the gripping device. Each of the above gripping devices has a pair of gripping portions capable of sandwiching the end portion of the test piece.
The test piece support portion supports the test piece by sandwiching the end portion of the test piece from above and below with the pair of grip portions.
The dimension according to claim 1, wherein the grip relaxing portion relaxes the grip of the test piece by displacing the upper grip portion of the pair of grip portions that support the test piece upward. measuring device. Each of the above gripping devices has a pair of gripping portions capable of sandwiching the end portion of the test piece.
The test piece support portion supports the test piece by sandwiching the end portion of the test piece from above and below with the pair of grip portions.
When the grip relaxing portion determines that the weight of the test piece to be measured is less than a preset threshold weight, both of the pair of grip portions supporting the test piece are displaced in directions away from the test piece, and the weight of the test piece is measured. When it is determined that the weight is equal to or more than a preset threshold weight, only the upper grip portion of the pair of grip portions supporting the test piece is displaced upward to relax the grip of the test piece. Item 1. The dimension measuring apparatus according to Item 1. A first centering mechanism that synchronizes the test piece placed on the stand from both sides in the longitudinal direction and aligns the longitudinal position of the test piece with a preset position.
A second centering mechanism that synchronizes the test piece placed on the stand from both sides in the width direction and aligns the width direction position of the test piece with a preset position.
The dimension measuring apparatus according to any one of claims 1 to 4, wherein the dimensional measuring apparatus is provided. A robot hand for transporting a test piece, a dimension measuring device for measuring the width and thickness of parallel parts in the test piece, and a tensile test for measuring the width and thickness of the test piece to obtain elongation-load characteristics. It has a test device and a calculation device that calculates the stress-strain characteristics of the test piece tested from the width and thickness obtained by the dimension measuring device and the elongation-load characteristics acquired by the tensile test device.
The automatic tensile test apparatus according to any one of claims 1 to 5, wherein the dimension measuring apparatus is the dimension measuring apparatus. An evaluation unit that obtains the Young's modulus from the stress-strain characteristics calculated by the above arithmetic unit and determines the pass / fail of the test result based on whether or not the Young's modulus is within the control range preset as the Young's modulus expected in the tested test piece. The automatic tensile test apparatus according to claim 6, further comprising. A dimensional measurement method for measuring the thickness and width of a pair of indenters that abut in the parallel portion of a test piece to be subjected to a tensile test in the measurement direction.
The thickness of the test piece is
After gripping both ends of the test piece with a pair of gripping devices and supporting the test piece with the thickness direction of the parallel portion facing up and down, the parallel portion is held from above and below with the pair of indenters. Hold it,
Then, it was determined based on the distance between the pair of indenters when the grip of the test piece was relaxed by the pair of gripping devices.
The width of the test piece is
The feature is that the indenter is stopped at the indenter holding position obtained from the edge detection position of the test piece by the edge sensor and the thickness of the test piece, held by the indenter from the width direction of the test piece, and obtained based on the distance between the indenters. Dimension measurement method to be performed. Each of the above-mentioned gripping devices has a pair of gripping portions capable of sandwiching the end portions of the test piece, and the end portions of the test piece are supported by sandwiching the end portions of the test piece from above and below by the pair of gripping portions.
In the relaxation of gripping the test piece, when the weight of the test piece is less than the preset threshold weight, both of the pair of grips supporting the test piece are displaced in directions away from the test piece, and the test piece is relaxed. When it is determined that the weight of the test piece is equal to or greater than the preset threshold weight, only the upper grip part of the pair of grip parts supporting the test piece is displaced upward to relax the grip of the test piece. The dimensional measurement method according to claim 8. The dimensional measurement method according to claim 8 or 9, wherein the test piece is centered at a preset position in a plan view before the test piece is gripped by the pair of gripping devices. The width and thickness of the parallel portion of the test piece are measured by using the dimensional measurement method according to any one of claims 8 to 10, and a tensile test of the test piece whose width and thickness are measured is performed to achieve elongation. Obtain the load characteristics, calculate the stress-strain characteristics from the measured width and thickness, and the above elongation-load characteristics.
The proof stress is characterized in that the pass / fail of the test result is determined based on whether or not the Young's modulus calculated from the stress-strain characteristic is within the control range preset as the Young's modulus assumed in the test piece tested. Evaluation method. The proof stress evaluation method according to claim 11, wherein the control range is obtained from the test results of each test piece that has been subjected to a tensile test in the past.

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