JP3327134B2 - Testing method and apparatus for metal materials and thermometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material test for a metal material, and more particularly to a test for determining a deformation characteristic value of a metal material, where and when a crack occurs in a test piece. TECHNICAL FIELD The present invention relates to a test method and apparatus for specifying a deformation characteristic value of a thermometer, and a thermometer used in the test.

[0002]

2. Description of the Related Art As one of the tests for metal materials, there is a test for determining formability.
There are the Erichsen test and the conical cup test specified in the standard. The forming limit of the test material in these tests is evaluated based on the overhang height (forming stroke) up to “the occurrence of cracks generated in the deformed portion” and the magnitude of the applied load.

[0003] The main evaluation method currently used is to stop the testing machine when the inspector visually detects this "cracking", and to measure the applied load and the test piece at this time. The dimensional change is used. In addition, a method of displaying "breakage" on a CRT with a CCD camera or a video camera and observing the CRT screen to determine that a crack has occurred and stopping the testing machine is also adopted. I have.

[0004] The problem of the above-mentioned prior art is that "cracking occurs".
Is visually observed and determined. It is necessary to keep an eye on the surface and cross section of the test piece even at one time, and this operation is very difficult. The same applies to the case of displaying on a CRT with a CCD camera or a video camera for observation. Also, when observing with a camera, this test is essentially a test to evaluate the moldability of the test material, so it is necessary to focus on the target surface of the test specimen and observe it. However, it is difficult to focus the camera, and there is a problem in accurately grasping the moment when “crack occurred”.

[0005] In addition, CR cameras and video cameras use CR.
A method has also been reported in which the screen displayed on T and the operating time of the applied load of the test machine are linked in a time series to determine the moment at which a crack has occurred. Being disturbed by factors such as scratches and dirt,
It includes the problem that the moment when a crack (fine crack) occurs cannot be obtained with accurate accuracy. In particular, when a crack was generated in the cross section of the test piece in the plate thickness direction, the direction of the crack became the same as the streak (irregularity) in the plate thickness direction. Further, when displaying on a CRT by analog processing, the sharpness of the image becomes a problem, and in the case of digital image processing, the level at which the binarization processing (shading processing) is performed becomes a problem.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in a deformation test of a metal material, a crack generation position (position and range) in a test piece, An object of the present invention is to make it possible to accurately specify an occurrence time and a deformation characteristic value when a crack occurs.

[0007]

According to the present invention, there is provided a test method for a metal material, which comprises applying a load to a test piece made of a metal material and obtaining a deformation characteristic value when a crack occurs in the test piece. Measuring and storing a time-series change in the deformation characteristic value when a load is applied to the test piece; and synchronizing with the time-series change in the deformation characteristic value, the temperature of the measurement target surface of the test piece. Measuring and storing a time-series change of the pattern; similarly, synchronizing with the time-series change of the deformation characteristic value, imaging a measurement target surface of the test piece, and storing the captured image; and A step of detecting a crack generated on the measurement target surface of the test piece by the applied load from the captured image, and identifying a crack generation location,
A step of searching for a time-series change in the temperature of the specified location of the crack from the time-series change of the stored temperature pattern, and a singular point of the time-series change in the temperature of the detected location of the crack. Detecting the crack occurrence time and the deformation characteristic value at the time of the crack occurrence by detecting the crack.

[0008] Deformation characteristic values or evaluation values in the deformation test are different depending on the test method. For example, in the conical hole push-out test, the load load and the hole diameter expansion rate at the time of crack generation, and in the Erichsen test, the stroke amount of the punch. , TZP
In the deep drawing test, it is the required maximum drawing force in drawing and the breaking force in overhang, and in the Olsen cup test, it is the moving distance of the test piece surface until breaking.

[0009] In the test method of the present invention, the time series change of the deformation characteristic value to be measured, the time series change of the temperature pattern on the surface to be measured, and the time series change of the captured visible image of the surface to be measured are all included. They are measured in synchronization and stored. It is convenient to use an infrared radiation thermometer incorporated in a visible light camera to measure the temperature pattern on the surface to be measured. Then, a load is applied to the test piece, and when the crack grows to a sufficient size and becomes clear, the load is stopped, and the captured image of the surface to be measured from the visible light camera is processed. Identify the location of the crack. As for when the crack occurred, a time-series change in the stored temperature of the measurement target surface is searched.

It is generally known that the relationship between the applied stress and the amount of heat generated by the strain generated inside the material is proportional within the elastic limit, and is expressed by the following equation (1). ΔT = −κ · t · Δα (1) where ΔT: Temperature change κ: Thermoelastic coefficient t: Absolute temperature of test piece Δα: Amount of applied stress That is, the test piece resists an external load. Until it breaks, heat is generated at this point and the temperature continues to rise. However, when the fracture occurs, the test piece loses its elastic resistance, stops heating, and instantaneously lowers its temperature by contact with air when the fracture occurs. By identifying the point where the temperature decreases, the moment when the test piece breaks is grasped. However, depending on the size, that is, the degree of opening of the crack, the temperature of the fractured part gradually decreases, while the temperature of the crack temporarily decreases due to the degree of opening of the crack. Some of them regain heat, so it is first necessary to accurately identify the location of the crack.

In the present invention, the moment when the crack is formed can be identified from a subsequent temperature change (heat history pattern), and the load application is stopped when the crack has grown to a sufficient size. . Therefore, it is possible to accurately specify the location of the crack using the visible light camera. As described above, it is not possible to accurately grasp the moment at which the crack occurs unless the crack generation location (position and range) is first specified. This is because the test piece is deformed while receiving a load and the temperature rises, so that the position where the crack is formed gradually moves. This is because if the temperature history of the moving point is measured individually, the moment at which the crack has occurred cannot be specified. Therefore, in the present invention, a maximum temperature history pattern at a location where a crack has occurred is retrieved from the storage means, and the pattern is searched to detect a point at which the temperature falls (singular point). Only in this way, the moment when the test piece is cracked can be accurately grasped. Therefore, the deformation characteristic value to be obtained can specify the deformation characteristic value at the time of occurrence of a crack from the time-series change of the deformation characteristic value stored in synchronization with the temperature.

The metal material testing device applied to the test method of the present invention includes a load applying device for applying a load to a test piece made of a metal material, and a load meter for measuring and storing a time series change of the load. , A thermometer that measures and stores the time-series change of the temperature pattern of the surface of the test specimen in synchronization with the time-series change of the applied load, and a field of view for the test specimen that is the same as the thermometer. A visible light camera that captures an image of the surface and stores the captured image, and in synchronization with the time-series change of the applied load, from the image of the measurement target surface of the test piece captured and stored by the visible light camera, generation of cracks and An image processing device that identifies the location of the crack and a singular point in the time-series change of the temperature of the identified location of the crack to determine the timing of the occurrence of the crack and the load applied when the crack occurs. Composed of a recognition device.

A load applying device for applying a load to a test piece made of a metal material, a load meter for measuring and storing a time series change of the load, and a load meter for synchronizing with the time change of the load, A thermometer that measures and stores the time-series change of the temperature pattern on the surface to be measured, and a crack after the applied load and temperature rise
And a display device for displaying a time-series change of the temperature pattern at a point where the temperature is lowered by the occurrence of the error on the time axis.

Further, as a thermometer used in the present invention, a visible light camera for capturing an image of a surface to be measured, and a storage device for inputting a captured image from the visible light camera and storing a time-series change of the image. And an image processing device that extracts a plurality of locations where cracks are generated from a time-series change of an image stored in the storage device. A time-series change in temperature at a plurality of locations extracted by the image processing device can be output from a time-series change in the temperature pattern of the measurement target surface measured and stored in synchronization with the image. Further, the thermometer enables an image processed by the image processing apparatus and a time-series change in the temperature pattern of the measurement target surface to be displayed on the same screen.

[0015]

FIG. 1 is a block diagram of a test apparatus according to the present invention. Here, a case of a conical hole push-out test is shown as an example. In FIG. 1, reference numeral 1 denotes a forming tester, which includes a punch 11, a die 12, a presser foot 13, and a load applying device 14 for applying a load to the test piece 2, and a load meter 15 for measuring a time series change of the load. ing. The time series data of the change in the load applied by the load meter 15 is stored in the load memory 16.

Reference numeral 3 denotes a visible light and infrared camera, which includes a visible light detector and an infrared detector (not shown). The light condensed by the condenser lens is separated into two directions by a half mirror. It is configured to collect light.
The camera 3 is aimed at a surface to be measured which is considered to have a high crack generation of the test piece 2, that is, an upper conical surface 21 provided with a hole 22 here, and the camera 2 is detected by the visible light detector. The time-series image data of the upper conical surface 21 is stored in the visible light image memory 31. On the other hand, two-dimensional time-series temperature data of the upper conical surface 21 measured by the two-dimensional infrared radiation thermometer 32 is stored in the temperature memory 33.

Reference numeral 4 denotes an image processing device which performs a binarization process or the like on the time-series image data sent from the visible light image memory 31 to specify the occurrence of cracks and their locations, and to determine the diameter of the hole 22. Calculation unit for the enlargement ratio (not shown)
Is calculated. Reference numeral 5 denotes a crack recognizing device which takes out the time series load data of the load memory 16 and the time series temperature data of the temperature memory 33 in synchronization with each other and detects a singular point of the time series temperature data, thereby generating a crack generation time and crack generation. This is to determine the applied load at the time.

Reference numeral 6 denotes a display device, which is an image processed by the image processing device 4, time-series image data in the visible light image memory 31, time-series temperature data in the temperature memory 33, time-series load data in the load memory 16, and crack recognition. The crack generation time specified by the device 5, the data of the applied load at the time of the crack generation, and the like are displayed. Further, the captured image and the time-series temperature data are displayed on the same screen.

The operation of the test apparatus of the present invention configured as described above will be described. A test piece 2 made of a metal material is sandwiched between a die 12 and a presser foot 13 as shown in FIG.
The punch 11 is raised and the hole 22 of the test piece 2 is expanded. The load applied to the test piece 2 by the load applying device 14 is measured by the load meter 15, and the upper conical surface 21 of the test piece 2 is imaged by the visible light and infrared camera 3. Measurement start signal is load memory 16, visible light image memory 31
And time-series load data from the load cell 15, time-series image data from the camera 3, and time-series temperature data from the two-dimensional infrared radiation thermometer 32, all of which are synchronized and stored in the memories 16, 3
1 and 33. In addition, by continuously increasing the applied load at a constant speed, it becomes easy to detect a singular point of a time-series change in temperature due to crack generation.

The image processing device 4 includes the visible light image memory 3.
The time series image data sent from 1 is binarized,
In addition, the enlargement ratio of the hole diameter is calculated. Then, when a crack (crack) of a sufficient size occurs in the test piece 2, the image processing device 4 specifies the occurrence and location of the crack, and transmits the identified location of the crack to the temperature memory 33, A stop signal is sent to the load applying device 14 to stop the load application. Further, the captured image of the upper conical surface 21 of the test piece 2 and the time-series temperature data are displayed on the display device 6 on the same screen.

FIG. 2 schematically shows temperature patterns immediately before and at the time of occurrence of a crack (crack). (A) is a temperature pattern immediately before the occurrence of a crack, and (b) is a temperature pattern at the time of the occurrence of a crack. FIG. 3C is a schematic diagram showing a method of specifying a crack generation time based on a temperature history of a two-dimensional pixel in a crack generation direction. In FIGS. 2A and 2B, the hatched portion (red) is a portion having a high temperature. Central circular shaded area 100
Indicates a sharp tip portion of the punch 11, and an outer ring-shaped hatched portion 101 indicates a circumferential edge portion of the hole 22 pushed and spread by the punch 11. From FIG. 2B, almost 1
Cracks occurred at two points A and C in the 80 ° direction. No cracks occurred at points B and D in the direction perpendicular to the straight line connecting A and C. Therefore, a straight line ab is specified for each of the crack occurrence points A and C, and the time-series temperature data of the maximum temperature history stored in the temperature memory 33 is searched from the measurement points a to b. In other words, the position of the crack generation site shifts and moves with the change of the applied load. However, it is considered that the position of the crack has shifted linearly from the direction of the crack detected by the visible light camera, and as shown in FIG. Determine the line segment ab. From the temperature history of each pixel 41 on the line segment ab, the temperature of the pixel showing the maximum temperature among the pixels at each time is determined as the temperature at that time, and the determined temperatures are time-series. A singular point is detected from the time-series temperature pattern and specified as a crack generation time.

FIG. 3 is a graph of the time-series temperature data. The solid line is, for example, the time-series temperature data of the crack occurrence location A, and the broken line is the time-series temperature data of the crack non-incidence location B. In FIG. 3, a crack occurs at point A 78 seconds after the start of measurement. The determination of crack occurrence is determined to be crack occurrence when the following two conditions are satisfied. As shown in FIG. 4, the measured temperature must be continuously or stagnant but continuously decreased by 3 div (div is the unit time of measurement) or more. From that point, the temperature must remain low for a certain period of time. 4A and 4B both satisfy the above two conditions, and the point P at which the temperature first starts to decrease is determined to be the crack generation time. Accordingly, in FIG. 3, point A satisfies the above two conditions, it is determined that a crack has occurred at point A, and there is no point that satisfies all of the above two conditions at point B shown by the broken line. It is determined that no crack has occurred.

The occurrence of cracks described above is described in FIG.
The crack recognizing device 5 captures the time-series temperature data in the temperature memory 33 and the time-series load data in the load memory 16 to detect a point at which the temperature falls, which satisfies the above two conditions. And the load applied at that time and the hole diameter enlargement ratio are determined.

As described above, first, the location of the crack occurrence is specified, and the crack occurrence time and the load load at the time of the crack occurrence and the hole diameter expansion rate as the deformation property values of the test piece material are specified for the location. This enables accurate identification and evaluation of values.

As described above, the deformation characteristic value or the evaluation value differs depending on the test method, and a measuring instrument corresponding to the object to be measured is prepared. For example, when measuring the stroke amount of a punch, a stroke detector such as a linear sensor is attached.

[0026]

As described above, according to the present invention, the time series change of the deformation characteristic value such as the applied load applied to the test piece, the time series change of the image of the measurement target surface, and the time change of the temperature of the measurement target surface Measures and stores all of the series changes in synchronization with each other, first identifies the location of the crack from the image captured by the visible light camera, searches for the stored time-series change in temperature, and searches for the crack occurrence time and crack occurrence Since the deformation characteristic value at the time is determined, it is possible to accurately grasp the moment when the crack is formed, and to accurately determine the deformation characteristic value.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a test apparatus according to the present invention.

FIG. 2 is a schematic diagram showing temperature patterns immediately before and at the time of occurrence of a crack on a measurement target surface, and an explanatory diagram of a method of specifying a crack occurrence time.

FIG. 3 is a graph of time-series temperature data of a crack occurrence location and a crack non-occurrence location.

FIG. 4 is an explanatory diagram in a case where it is determined that a crack has occurred based on time-series temperature data.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Forming test machine 2 Test piece 3 Visible light and infrared camera 4 Image processing device 5 Crack recognition device 6 Display device 11 Punch 12 Dice 13 Presser foot 14 Load applying device 15 Load meter 16 Load memory 21 Upper conical surface of a test piece (measurement Target surface) 22 Hole in test piece 31 Visible light image memory 32 Two-dimensional infrared radiation thermometer 33 Temperature memory 41 Two-dimensional pixel

Continuation of the front page (72) Inventor Masakazu Inomata 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) References JP-A-61-23941 (JP, A) JP-A-61-48739 (JP, A) JP-A-9-159590 (JP, A) JP-A-4-1551 (JP, A) JP-A-6-58892 (JP, A) JP-A-5-223716 (JP, A) Kaihei 3-28731 (JP, A) Japanese Utility Model Hei 5-59291 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 3/28 G01B 5/30 G01N 33/20 JICST File (JOIS)

Claims (5)

(57) [Claims] 1. A test method for applying a load to a test piece made of a metal material and obtaining a deformation property value when a crack occurs in the test piece, wherein the deformation property when a load is applied to the test piece. Measuring and storing the time-series change of the value, and measuring and storing the time-series change of the temperature pattern of the measurement target surface of the test piece in synchronization with the time-series change of the deformation characteristic value. A step of taking an image of a measurement target surface of the test piece in synchronization with a time-series change of the deformation characteristic value and storing the taken image; and measuring the test piece by the load from the stored taken image. A step of detecting a crack occurring on the surface and specifying a crack occurrence location; and a step of searching for a time-series change in the temperature of the identified crack occurrence location from the time-series change of the stored temperature pattern. And the search Detecting the singular point of the time series change of the temperature of the generated crack location to determine the crack generation time and the deformation characteristic value at the time of the crack generation. Test method. 2. A load applying device for applying a load to a test piece made of a metal material, a load meter for measuring and storing a time series change of the load, and a load meter for synchronizing with the time series change of the load. A thermometer that measures and stores the time-series change of the temperature pattern of the measurement target surface of the test piece, and the same visual field as the thermometer for the test piece, images the measurement target surface of the test piece, and obtains an image of the image. Visible light camera to be stored, in synchronization with the time series change of the applied load, from the image of the measurement target surface of the test piece imaged and stored by the visible light camera, the occurrence of cracks and the location of the occurrence of the cracks An image processing device for identifying, and a crack recognition device for determining a time when the crack occurs and a load applied when the crack occurs by detecting a singular point in a time series change in temperature of the identified crack occurrence location. Test device for a metallic material characterized by having and. 3. A load application device for applying a load to a test piece made of a metal material, a load meter for measuring and storing a time series change of the load, and a load meter for synchronizing with the time series change of the load. and a thermometer for measuring and storing the time-series change in the temperature pattern of the object surface of the test piece, the temperature is low due to the occurrence of cracks after the applied load and Atsushi Nobori
A display device for displaying a time-series change of the temperature pattern at a lowered point so as to be able to correspond on a time axis. 4. A visible light camera that images a surface to be measured, a storage device that receives a captured image from the visible light camera and stores a time-series change of the image, and an image stored in the storage device. An image processing apparatus for extracting a plurality of locations where cracks have occurred due to the time series change of the visible light camera, the same visual field as the visual field with respect to the measurement target surface of the visible light camera is provided, and the captured image and From the time series change of the temperature pattern of the measurement target surface measured and stored in synchronization,
A thermometer capable of outputting a time-series change in temperature at the plurality of extracted locations. 5. A visible light camera for capturing an image of a measurement target surface, a storage device for receiving a captured image from the visible light camera and storing a time-series change of the image, and an image stored in the storage device. Crack due to time series change of
And an image processing apparatus for extracting a plurality of locations where the occurrence of the measurement object is provided. The same visual field as the visual field with respect to the measurement target surface of the visible light camera is provided, and the measurement target measured and stored in synchronization with the captured image is provided. From the time series change of the surface temperature pattern,
A thermometer capable of outputting a time-series change in temperature at the plurality of extracted locations, wherein the captured image and the time-series change in temperature can be displayed on the same screen.