JP2016095300A - Fatigue testing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary bending fatigue testing device that can observe/measure the generation and growth behavior of crack and the length of crack in one surface of a test piece made of metal material or the like in a fatigue test by photographing the crack in real time in an excellent emission state.SOLUTION: In a first aspect according to the invention, a test piece is positioned with reference to angular information including initial crack or the like on the rotational direction, then the test piece is equipped to a rotary bending fatigue testing device with reference to coordinate information of the test piece on the axis direction as well, and images regularly taken are analyzed with a PC in real time so that progress of the crack is analyzed on the basis of the observation with imaging by imaging means (such as a camera), with a timing of high-rate emission by a light source (such as an LED) being synchronized with a timing of which the crack as an observation target in one surface of the test piece is rotating and moving into a photographable range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fatigue test apparatus capable of observing and measuring in real time the generation and growth behavior of a crack generated in a rotating bending fatigue test and a tensile compression fatigue test on the surface of a test piece, and the length of the crack.

  When a metal specimen is subjected to a rotating bending fatigue test or tensile / compression fatigue test, not only the stress amplitude and the number of repetitions of rupture (so-called SN characteristics) are detected, but the fatigue that occurs and grows on the surface of the specimen. It is known that more information on fatigue properties can be obtained by observing changes in the crack.

  Conventionally, the observation of the fatigue crack generation, growth, and change of the fatigue crack until the final fracture of such a specimen has generally followed the physical shape change by the replica method. The replica method is a method of observing the shape of a replica that is pasted on the surface of a test piece and the surface shape is copied. Here, the replica method will be exemplified and described. First, when using a film-like acetylose piece as a template material as a replica, immerse it in an organic solvent such as methyl acetate or acetone (hereinafter referred to as “acetone or the like”), and then use a tweezers or the like to remove the test piece. Affix to the crack observation surface. Then, the mixture is left for a predetermined time (usually 1 to 1.5 minutes) and waits for acetone or the like to evaporate from the acetylose pieces, and then peels off the acetylose pieces from the test pieces. Next, affix the double-sided tape to the glass plate prepared in advance on the adhesive surface of the double-sided tape. Observe and take a photo. The series of operations up to this photo shoot was carried out continuously until it was possible to clearly determine that a crack had occurred on the surface of the specimen itself, and the image recording was traced back to the past. The progress of the crack from the beginning can be traced in the form of a replica shape change. Furthermore, by continuously testing the test piece, it is possible to continue to observe until it breaks.

  However, the above replica method requires experience in how to attach a replica produced using a film-like acetylose piece, and bubbles do not intervene when applying to the surface of the test piece, so that the shape of the crack is not reflected. In many cases, it is difficult. Further, in the replica method, it is necessary to interrupt the test for a predetermined time each time because of work such as attaching a replica piece, and there is a demand for observation of crack change without interrupting the test. In addition, for example, in recent years, in a tensile / compression fatigue test, it is difficult to perform real-time measurement with the naked eye because the test speed is increased, for example, the test piece is vibrated with ultrasonic waves.

  Furthermore, especially when using the replica method for observation of fatigue cracks in a rotating bending fatigue test, the specimen is usually cylindrical and the part where the fatigue crack occurs is curved, so it is extremely sticky. It is difficult to attach. In addition, when the test piece was irradiated with light coaxially with the observation axis of the metal microscope and an attempt was made to find the occurrence of a crack, the light hits only the top of the curved surface of the test piece, and the entire fatigue crack Can not be observed. For this reason, there has been a problem that the discovery of cracks requires experience. In addition, when the test piece was irradiated with light coaxially with the observation axis of the metal microscope and an attempt was made to find the occurrence of a crack, the light hits only the top of the curved surface of the test piece, and the entire fatigue crack Can not be observed. For this reason, there has been a problem that the discovery of cracks requires experience.

  On the other hand, it is conceivable to observe the specimen surface in synchronization with the vibration of the tensile / compression fatigue tester and the rotation of the rotating bending fatigue tester without interrupting the test. A stroboscope that can emit light for a very short time is essential. When a xenon lamp is used as the light source, even if a light emission command signal (pulse wave) is input, the change in lamp brightness (light emission) cannot follow the pulse wave. There are also problems such as deviations in the light emission timing and insufficient observation (photographing) due to insufficient brightness.

  Also, in the ultrasonic tension / compression fatigue test that has been developed in recent years in the tensile / compression fatigue test, once the device is started and stopped to observe the cracks in the test piece, the conditions of the fatigue test before and after the start and stop of the fatigue test device are changed. There was also a problem that test results fluctuated and were affected.

  In addition, there is a need to measure the tip strain due to changes in the crack opening in the tensile / compression fatigue test. Currently, only the strain at the static load on the test piece is measured, and the dynamic load during the fatigue test is measured. We cannot measure the distortion.

  The present invention has been created in view of the above problems, and the occurrence and growth behavior of “cracks” on the surface of a specimen such as a metal material in a rotating bending fatigue test or a tensile / compression fatigue test, It is an object of the present invention to provide a fatigue test apparatus capable of observing and measuring the length of "" in real time in a good light emitting state.

  The present invention provides a rotating bending fatigue test apparatus that grips an end of a test piece while applying a load and rotates the shaft. Specifically, the imaging means disposed at a position where the shape change can be observed based on the rotational direction angle information and the axial position information of the initial shape change detected on the surface of the test piece, and the test A light source capable of irradiating the strip for a short time, and changing the shape of the surface of the test strip by the imaging means by emitting the light source for a short time and irradiating the test strip while the test strip is rotating The rupture time of the test piece is predicted by continuously observing the still images and tracking and comparing changes over time.

  According to this rotational fatigue bending test apparatus, the occurrence of a shape change (typically “crack” (hereinafter referred to as “crack”)) on the surface of a specimen such as a metal material in the rotational bending fatigue test, and The growth behavior and the length of the “crack” can be observed and measured by photographing in real time in a good light emission state.

  Further, when the test piece reaches the phase of rotation of the test piece that can image the “crack” on the surface of the test piece with the imaging means, the light emission of the light source and the imaging of the imaging means are synchronized. be able to.

  Further, the light source is an LED stroboscope, the rotational drive source of the test piece is a servo motor, and the rotary bending fatigue apparatus includes a gear that cooperates with the rotation of the servo motor, and around the gear. A magnetic sensor having a magnetoresistive effect element, and the resistance value of the magnetoresistive effect element of the magnetic sensor based on the relationship between the angular position of the magnetic sensor and the position of the teeth constituting the gear. By converting this change into a voltage change and converting this change into a pulse signal, an input signal for LED emission can be generated.

  For example, in order to synchronize the light emission timing of the LED stroboscope, the angle of the circumference of the gear is controlled by a servo motor, and the relationship between the angular position of the rotating magnetic sensor and the position of the teeth constituting the gear, Using the phenomenon that the resistance value of the magnetoresistive effect element embedded in the magnetic sensor changes with the change of the magnetic field, the change of the resistance value of the element is converted into the change of voltage, and the sine waveform is obtained. This is solved by converting the signal into a pulse signal and generating an input signal for LED light emission.

  Further, the light source emits light by subdividing into fine time at a time interval synchronized with the rotation speed of the test piece, and the image pickup device takes a plurality of images obtained by subdividing one point on the test piece in the rolling direction. Then, the shape change of the surface of the test piece may be stereoscopically viewed by comparing the plurality of subdivided images.

  In addition, according to this rotating bending fatigue test apparatus, a high-frequency current is applied at a constant voltage from both ends of the test piece, the change in the magnitude of the current flowing on the surface is measured, and the time when the current decreases is measured on the surface of the test piece. It may be estimated that the initial shape change has occurred.

  In other words, in this case, the initial shape change of the surface of the test piece is conducted by applying a high-frequency current at a constant voltage from both ends of the test piece, measuring the change in the magnitude of the current flowing on the surface, and initializing when the current decreases. Assuming that a general shape change has occurred, the rotation of the test piece can be interrupted, and the surface of the test piece can be comprehensively inspected to find an initial “crack”.

  Moreover, when the fracture | rupture time of a test piece is estimated, it is preferable to reduce the rotational speed of a test piece.

  By continuously observing the progress of the “crack” that has occurred on the test piece, by predicting the break time, the temperature rise of the test piece due to high-speed rotation with a bending load applied is suppressed. The rotation speed is automatically reduced so as to be equivalent to the test at the test piece rotation speed.

  In addition, discharge light emission and pulsed laser light are also used as the light source for a short time.

  Moreover, it is preferable that the optical axis of the light source and the light receiving device of the imaging means are arranged at the same angle with respect to the test piece.

  With such a configuration, a minute change occurring on the surface of the test piece can be detected as a change in light reflection intensity.

Further, the second aspect of the present invention is a fatigue test apparatus for performing tensile / compression measurement by applying a repeated load in the tension / compression direction to the end of the test piece,
Imaging means disposed at a position where the shape change can be observed based on the position information of the initial shape change detected on the surface of the test piece;
An irradiation source capable of irradiating the test piece with light for a short time (for example, the light source 104 in the present embodiment),
With the test piece repeatedly loaded,
By irradiating the test piece with light from the irradiation source, a still image of the shape change of the surface of the test piece is collected by the imaging means, and the time of breakage of the test piece is determined by tracking, observing and comparing the change over time. Predict.

  According to this fatigue test apparatus, the occurrence of shape change (typically "crack") on the surface of a specimen such as a metal material in a tensile / compression fatigue test, its growth behavior and the length of "crack" A photograph can be taken and observed and measured in real time in a good light emission state.

Specifically, this fatigue test device takes a crack image of the test piece,
Image collecting means (for example, the image collecting device 107 in the present embodiment) for collecting a crack image of the test piece photographed by the imaging means, and vibration means (for example, in the present embodiment) for applying the repeated load to the test piece. The vibrator 102), load control means for transmitting a control signal to the shaker (for example, the load control device 108 in this embodiment), and the image collecting means and the load control means are synchronized. Synchronization control means for controlling (for example, the synchronization control device 109 in the present embodiment).

  Further, the synchronization control means transmits a signal synchronized with a signal for transmitting power to the irradiation source as a signal for controlling the image collecting means, whereby the image collecting apparatus collects a static test piece crack image. be able to.

  In this fatigue test apparatus, the synchronization control apparatus synchronizes the image collection apparatus that collects the crack image of the test piece taken by the imaging means and the load control apparatus that sends a signal for applying an axial load to the vibration means. Thus, the dynamic shape change during the fatigue test can be acquired and measured as a static image. Therefore, it is possible to observe and measure crack generation and growth behavior of the specimen in real time. Furthermore, it is possible to observe and measure the crack tip strain at a specific opening angle of the crack during the fatigue test in real time.

  Further, the vibration means includes a piezoelectric element that vibrates with ultrasonic waves, and receives a signal from the load control means to apply a load to the test piece, or a hydraulic / pneumatic drive or electromagnetic or motor drive actuator. And a method of applying a load to the test piece by receiving a signal from the load control means.

  This fatigue test apparatus can be applied not only to the case where a test piece is vibrated by hydraulic pressure or a motor, but also to an ultrasonic fatigue test apparatus that has been attracting attention as a high-speed fatigue test apparatus in recent years. Therefore, the crack of the test piece can be measured without starting and stopping the fatigue test apparatus, and the conditions of the fatigue test do not fluctuate before and after the start and stop.

  The synchronous control device may include a frequency dividing circuit that divides a signal from the load control device.

  Even when a test piece is vibrated at a high frequency such as an ultrasonic wave, it can be measured after being converted to such an extent that it can correspond to an irradiation source or can collect images.

Furthermore, the image processing means (for example, the image processing apparatus 112 in the present embodiment) for receiving and processing the image data of the test piece from the image collecting means is provided,
The image processing means transmits a positioning signal for positioning the position of a crack in the test piece in the image data,
Positioning means (for example, the positioning device 111 in the present embodiment) that receives the positioning signal and moves the imaging means to an appropriate position may be provided.

  Thereby, the tip position of the crack of the test piece can be monitored, and the position of the imaging means can be adjusted as appropriate to track the crack growth and automatically measure.

  According to the fatigue test apparatus of the present invention, the occurrence of "crack" and the growth behavior and the length of "crack" on the surface of a test piece such as a metal material in a rotational bending fatigue test or a tensile / compression fatigue test are excellent. It is possible to take a photograph in real time and observe and measure it in the light emission state.

It is the schematic which shows the structure of the principal part of the rotation bending fatigue test apparatus based on one Embodiment of this invention. In the rotating bending fatigue test apparatus which concerns on one Embodiment of this invention, it is the schematic for demonstrating the structure which synchronizes rotation of a test piece and pulse light emission, in order to image a crack. 1 is a schematic diagram for explaining a configuration for generating a pulse signal for capturing a crack as a still image in a rotating bending fatigue test apparatus according to an embodiment of the present invention. It is the schematic explaining the structure of the pulse light emission part in the rotation bending fatigue test apparatus which concerns on one Embodiment of this invention, and the schematic which illustrates the test piece imaged by irradiation from a light source. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which illustrates the test piece used by the rotation bending fatigue test apparatus which concerns on one Embodiment of this invention, and a general rotation bending fatigue test. It is the schematic which shows the structure of the principal part of the load application part in the rotation bending fatigue test apparatus which concerns on one Embodiment of this invention. The schematic diagram (schematic diagram) of the principal part of the embodiment of another tensile / compressive fatigue test of the present invention is shown. It is a block diagram which shows the outline | summary of the synchronous control apparatus shown in FIG.

  First, a description will be given of a fatigue test apparatus according to the present invention which is used for a rotary bending fatigue test (hereinafter, also simply referred to as “rotary bending fatigue test apparatus”). This rotating bending fatigue testing device can greatly reduce the time required for the rotating bending fatigue test compared to the normal test method without stopping the rotation of the test piece by using the means roughly divided into the following two. To do. In addition, the occurrence of cracks on the surface of the test piece used in the rotating bending fatigue test, its growth behavior and the length of the "crack" are measured at least after the "crack" occurs in the test piece. Obtain accurate test results equivalent to or better than the normal rotating bending fatigue test method while enabling real-time observation / measurement (hereinafter also referred to simply as “observation”) until fracture occurs. To realize.

  One of the above-described means is a means for capturing a crack that is generated and propagates in a test piece rotating at a high speed (approximately 20000 to 30000 rotations / minute) as a clear still image under a good light emission state. It is. The other one infers the breakage time of the test piece based on the data of the still image picked up as described above, and sets the rotation speed of the test piece to a predetermined rotation time before the breakage of the test piece. It is a means to reduce the speed.

  As described above, in the conventional rotational bending fatigue test method, since the crack is observed by the replica method or by visual observation, it is necessary to stop and observe the rotation of the test piece. However, when the rotation of the test piece is stopped during the test, a tensile load is applied to a specific portion in the circumferential direction of the test piece. As a result, damage (stress concentration location) not resulting from the bending fatigue test occurs in the test piece, which may affect the test result, which is not preferable.

  For this reason, the test result under the most desirable test conditions, that is, the rotation speed of the test piece becomes a predetermined speed, after a predetermined load is applied to the test piece, until the test piece breaks or a predetermined number of times. Until the addition of the load is completed, it is difficult to obtain a test result when the test is continuously performed.

  It is also conceivable that an external force other than the predetermined load is erroneously applied to the test piece during the process of stopping the rotation of the test piece. For example, there is also a concern that the test piece rotation should be stopped after removing the load, but the rotation of the test piece is stopped while the load is applied, and accurate test results cannot be obtained. is there.

  With the rotating bending fatigue test apparatus of the present invention, the above-described test under the most desirable test conditions can be performed accurately and efficiently. In addition, it is possible to observe the crack generated on the surface of the test piece and the progress of the crack while the rotation of the test piece is continued.

《Configuration of rotating bending fatigue test equipment》
As a premise for explaining a method such as observation of a crack in the rotating bending fatigue testing apparatus of the present invention described above, the configuration of the rotating bending fatigue testing apparatus 80 of the present invention is the rotating bending fatigue according to one embodiment of the present invention. FIG. 1 which is a schematic diagram illustrating the configuration of a main part of a test apparatus, and a schematic diagram illustrating a rotational bending fatigue test apparatus according to an embodiment of the present invention and a test piece generally used in a rotational bending fatigue test. 5 and FIG. 6 which is a schematic diagram showing the configuration of the main part of the load applying portion in the rotary bending fatigue test apparatus according to one embodiment of the present invention.

  As shown in FIG. 1, the rotary bending fatigue test apparatus 80 includes at least the rotation driving means 10 that generates rotation of the test piece 40 and the rotation spindle 10a of the rotation driving means 10 on one side of the rotation spindle 10a. A gear part 12 fixed to the core, a magnetic sensor 14 rotatably arranged around the gear part 12, and a concentric core with the rotary main shaft 10a, the magnetic sensor 14 being arranged around the gear part 12 A servo motor 16 that is rotatably held at an arbitrary position, and a magnetic sensor 14 that is connected to a rotation shaft (not shown) of the servo motor 16 and carries the magnetic sensor 14. And a sensor support portion 15 that can rotate the arrangement position around the gear portion 12.

  The rotary bending fatigue test apparatus 80 of FIG. 1 also includes at least a chuck portion 18 that grips the test piece 40 on the opposite side of the rotation main shaft 10a of the rotation driving means 10 to the gear portion 12, and a pulse signal. In response to this, light having a short time width (hereinafter also referred to as “pulse light”) at a “crack” on the surface of the test piece 40 or a site where the crack propagates (hereinafter also simply referred to as “crack or the like”). And the imaging means 22 capable of capturing a predetermined position of the test piece 40 as a stationary image.

  The image pickup means 22 includes a photoelectric conversion element (not shown; hereinafter also referred to as “image pickup element”) that can detect light from a crack or the like of the test piece 40 and generate a charge. As the imaging device, for example, a CMOS image sensor, a CCD image sensor, or the like can be used, and thereby, an image of a crack of the test piece 40 and the progress of the crack can be recorded as electronic data.

  The imaging unit 22 includes an interval detection unit 26 that can measure the reception period of two signals. The interval detection means 26 receives a pulse signal for causing the pulse light emitting unit 20 to emit light, and opens and closes a so-called shutter (not shown) included in the imaging means 22 when there is no signal and when a signal is received. To switch at high response speed. As will be described in detail later, by providing this interval detection means 26, the timing of the light emission of the pulse light emitting unit 20 and the image pickup by the image pickup means 22 is adjusted so that the crack of the rotating test piece 40 is optimal for the image pickup. It becomes possible to synchronize with the timing.

  Note that the imaging unit 22 preferably includes an optical enlarging unit 24 that combines the telescope and the microscope shown in FIG. As a result, the periphery of the test piece 40 such as a crack can be enlarged, and the imaging means 22 can selectively enlarge the crack or the like and take an image.

  FIG. 5 illustrates a rotating bending fatigue test apparatus 80 and a test piece 40 that is generally used in a rotating bending fatigue test. FIG. 5A illustrates a crack that is a starting point of a crack in the test piece 40 in advance. FIG. 5 (b) is a schematic view in a top view when the starting point portion 40a is provided, and FIG. 5 (b) is a cross-sectional view taken along the line WW shown in FIG. 5 (a), that is, the rotational axis of the test piece 40 in the rotational bending fatigue test. FIG. 5C is an enlarged view of the region K shown in FIG. 5B and schematically shows an example of the crack starting point portion 40a.

  In the rotating bending fatigue test apparatus 80 of the present invention, the test piece 40 has a crack starting point portion 40a which becomes a crack starting point, and a case where a crack generated and propagates from the crack starting point portion 40a is observed, and during the test. In both the case where the initial crack is generated in the test piece 40 and the crack that propagates from the initial crack is observed, the crack on the surface of the test piece 40, the progress of the crack, and the like are observed. It is possible.

  As will be described in detail later, a case in which the crack starting point portion 40a is provided in advance in the test piece 40 and a case in which an initial crack is generated in the test piece 40 during the test and a crack that propagates from the initial crack is observed. In any case, the imaging means 22 and / or the optical enlarging means 24 and the pulse light emitting part 20 described later can photograph and irradiate the crack starting point part 40a which is the weakest part of the test piece 40 and its periphery. It is arranged.

  The chuck portion 20 is preferably formed integrally from the same member as the main shaft 10a of the rotation driving means 10. As a result, the amount of eccentricity between the axis of the test piece 40 gripped at one end by the chuck portion 20 (rotation axis in this rotating bending fatigue test apparatus 80) and the rotation axis of the main shaft 10a of the rotation driving means 10 is achieved. As a result, a crack or the like of the test piece 40 rotating at approximately 20000 to 30000 rotations / minute can be imaged more clearly, observed, etc. while suppressing blurring.

  Further, as shown in FIG. 1, the rotating bending fatigue test apparatus 80 causes at least the pulse light emitting unit 20 to emit light based on signals from the magnetic sensor 14 and the servo motor 16, and the imaging means 22 performs the test. Pulse light emission control means 28 for generating and outputting a pulse signal Sp for imaging a crack or the like of the piece 40 is provided.

  As will be described in detail later, by using the pulse signal Sp for pulse emission created by the pulse emission control means 28, it is most suitable for imaging the crack or the like on the surface of the test piece 40 with the imaging means 22. An image (still image) of a crack or the like of the test piece 40 rotating at a high speed by synchronizing the timing of reaching a certain phase, the timing of light emission of the pulse light emitting unit 20 and the timing of imaging by the imaging means 22 It becomes possible to shoot as.

  6 is a schematic diagram showing the configuration of the main part of a load loading unit that applies a load to the test piece 40 that can be rotated by the rotation driving means 10 in the rotary bending fatigue test apparatus 80 according to one embodiment of the present invention. As shown in FIG. 4, in the rotating bending fatigue test 80, the load loading portion 32 is disposed at the other end as a free end of the test piece 40 held at one end by the chuck portion 18.

  The load applying unit 32 includes an adapter 32a for rotatably connecting the other end of the test piece 40 as the free end of the test piece 40 rotated by the rotation driving means 10, and a vertically downward direction to the test piece 40. The weight portion 32c as a weight that acts on the weight of the self-weight, and a suspension portion 32b for connecting the adapter 32a and the weight portion 32c. The weighting unit 32c performs additional setting of the load depending on the shape of the test piece 40 and the evaluation conditions.

<< Configuration and Method for Synchronizing Timing of Pulse Emission and Imaging with Rotation of Specimen >>
In the rotating bending fatigue test apparatus 80 of the present invention, as described above, the timing at which the crack on the surface of the test piece 40 and the part where the crack progresses reaches the optimum phase for imaging by the imaging means 22. In addition, by synchronizing the timing at which the pulse light emitting unit 20 emits light and the timing at which the imaging means 22 captures images, it is possible to capture a crack or the like on the surface of the test piece 40 rotating at a high speed as a still image. To do.

  Regarding the configuration and method for realizing this synchronization, in FIG. 1 and the rotating bending fatigue test apparatus according to one embodiment of the present invention, the rotation of the test piece and the pulse light emission for imaging the crack are performed. FIG. 2, which is a schematic diagram for explaining the configuration to be synchronized, and the configuration for generating a pulse signal for imaging a crack as a still image in the rotating bending fatigue test apparatus according to an embodiment of the present invention. This will be described in detail with reference to FIG.

  FIG. 2 is a diagram for explaining a configuration in which rotation of a test piece and pulse emission are synchronized in order to image a crack in the rotating bending fatigue test apparatus 80 according to the embodiment of the present invention shown in FIG. FIG. FIG. 2A shows a case in which a crack starting point portion 40a, which becomes a crack starting point, is provided in the test piece 40 in advance, and after confirming an initial crack generated in the test piece during the test, In this case, the rotation of the component used for fixed point observation after the position of the crack starting point 40a is detected is set as the crack starting point 40a and the observation is continued. It is the schematic which shows an example of the relative position in a direction.

  Until the crack generated in the test piece 40 is detected, the magnetic sensor 14 shown in FIG. 2A rotates around the gear portion 12 by driving a servo motor (shown as 16 in FIG. 1) (not shown). Moved. Further, after the position of the crack starting point 40a is detected, the magnetic sensor 14 shown in FIG. 2A is supported and fixed by a servo motor (not shown).

  Taking as an example the case where the crack starting point portion 40a is provided in advance on the test piece 40, the imaging means 22 images a crack or the like on the surface of the test piece 40 in order to image the crack of the test piece 40 as a still image. A configuration and a method for synchronizing the timing at which the pulse light emitting unit 20 emits light with the timing at which the imaging unit 22 captures the image will be described below. A configuration for detecting an initial crack generated in the test piece 40 in a state where the test piece 40 is rotated will be described in detail later.

  In FIG. 2A, the gear portion 12 fixed to the main shaft 10a of the rotation driving means 10 has convex portions A to I formed at equal pitches on the outer periphery thereof. Further, the magnetic sensor 14 is located at a position where the rotation of the gear portion 12 can be detected from a change in the magnetic field generated between the convex portions A to I (hereinafter also simply referred to as “convex portion A etc.”). It is carried on the rotating shaft of the servo motor 16 via the sensor support 15 shown in FIG.

  In the rotating bending fatigue test apparatus 80 of the present invention shown in FIG. 1, when the test piece 40 has a crack starting point portion 40a that becomes a crack starting point in advance, the servo motor 16 is not driven as described above, and magnetic The sensor 14 is fixed at a predetermined position by the servo motor 16 via the sensor support portion 16.

  When the rotation driving means 10 shown in FIG. 1 is driven and the rotation main shaft 10a rotates, the gear portion 12 fixed to one end of the rotation main shaft 10a (the left direction in FIG. 1) also rotates at the same speed. The rotation speed of the rotating gear unit 12 is detected by the magnetic sensor 14 in a fixed state and is input to the pulse light emission control unit 24, and a signal for light emission of the pulse light emission unit 20 is generated.

  FIG. 3A is a schematic diagram schematically showing a change in the magnetic field generated between the gear unit 12 rotating in the counterclockwise direction (the direction of the white arrow) on the paper surface and the magnetic sensor 14 in the fixed state. FIG. 3B shows a so-called magnetoelectric conversion element (not shown; hereinafter also referred to as “magnetoresistance effect element”), which is incorporated in the magnetic sensor 14 and detects the unevenness of the gear portion 12. FIG. 4 is a chart schematically showing how a voltage value generated by the magnetoresistive element changes as the magnetic field shown in FIG.

  The generation process of the signal for light emission will be described in detail with reference to FIGS. 3 (a) and 3 (b). As shown in FIG. 3A, the magnetic field generated between the gear portion 12 and the magnetic sensor 14 as the gear portion 12 rotates from time T1 to time T4 is indicated by a solid arrow in the figure. To change.

  As the magnetic field changes, the resistance value of the magnetoresistive effect element built in the magnetic sensor 14 also changes, and the voltage value V output from the magnetoresistive effect element also varies with time as shown in FIG. It changes from T1 to T4. This output voltage value V is input from the magnetic sensor 14 shown in FIG. 1 to the pulse light emission control means 28, converted into a pulse signal by a processing circuit (not shown), and the pulse light emission of the pulse light emission unit 20 and the imaging means. The pulse signal Sp for imaging by 22 is generated.

  This pulse signal Sp is sent from the pulse emission control means 28 in accordance with the timing at which the phase in the rotation direction of the crack starting point portion 40a of the test piece 40 reaches the optimum phase for imaging by the imaging means 22. It is transmitted to at least the pulse light emitting unit 20 shown in FIG. 1 and the interval detection means 26 provided in the imaging means 22.

  With reference to FIG. 1 and FIG. 2A, a method of synchronizing the timing of pulse emission and imaging with the rotation of the test piece 40 by the pulse signal Sp will be described in detail. As described above, the test piece 40 having the crack starting point portion 40 a and the gear portion 12 are connected via the chuck portion 18 shown in FIG. 1 and the rotation main shaft 10 a of the rotation driving means 10. In other words, the test piece 40 and the gear portion 12 are rotated while maintaining the same phase by the rotational drive of the rotational drive means 10.

  At this time, as shown in FIG. 2A, at the timing when the magnetic sensor 14 detects the convex portion A of the gear portion 12, the position of the test piece 40 in the rolling direction of the crack starting point portion 40a, and the gear portion. The test piece 40 is gripped in advance by the chuck portion 18 so that the surface in the rolling direction of the 12 convex portions B (the left side surface of the convex portion B in FIG. 2A) has the same phase.

  In addition, as illustrated in FIG. 2A, the imaging unit 22 and / or the optical enlarging unit 24 are arranged in advance so as to be able to image the same phase as the surface of the convex portion B in the rolling direction. The pulse light emitting unit 20 is also arranged in advance so as to be able to irradiate the same phase as the surface of the convex portion B in the rolling direction.

  In the state described above, the pulse light emission control unit 28 shown in FIG. 1 outputs the pulse signal Sp, and the pulse light emission unit 20 is received by the pulse light emission unit 20 and the interval detection unit 26 included in the imaging unit 22. Emits light, irradiates the crack starting point portion 40a of the test piece 40 and a range where the crack propagates, and the light reflected by the surface of the test piece 40 including the crack and the like is included in the imaging means 22. Reflected in the direction of the image sensor.

  Further, as described above, the shutter (not shown) of the imaging unit 22 is switched from the closed state to the open state by the interval detection unit 26 that has received the pulse signal Sp, and the light reflected by the crack or the like is The image pickup device 22 reaches the image pickup device.

  As described above, the pulse light from the pulse light emitting unit 20 is applied to the crack or the like on the surface of the rotating test piece 40 in synchronism with the timing when the optimum phase for imaging by the imaging unit 22 is reached. The shutter is opened substantially simultaneously with the irradiation of the pulsed light, and the light reflected by the crack or the like arrives at the imaging device provided in the imaging means 22. As a result, it is possible to clearly capture the crack and the like of the test piece 40 rotating at a high speed as a still image.

  In addition, the pulse light emission part 20 is comprised by the light source which can light-emit at high response speed in response to the pulse signal Sp for pulse light emission. As the light source for pulsed light emission, for example, a light emitting diode, discharge light emission, or laser light is preferably used. Thereby, the response to the pulse signal Sp as the light emission command signal is good, and it is possible to obtain a luminance sufficient for imaging by light emission for an extremely short time.

  When observing a “crack” by a conventional method, for example, the replica method described above, it is necessary to temporarily stop the rotation of the test piece 40. When the crack progresses and the rotation of the test piece 40 is stopped immediately before the test piece 40 breaks, the load of the load applying portion 32 is applied to the test piece 40, and the crack progresses rapidly or reaches the break. There are concerns. For this reason, it is generally very difficult to observe the growth of a crack immediately before the test piece 40 breaks.

  According to the rotating bending fatigue test apparatus 80 of the present invention, as described above, the test piece 40 is tested by synchronizing the timing of the pulse light emission by the pulse light emitting unit 20 and the image pickup by the image pickup means 22 with the rotation of the test piece 40. It is possible to capture the crack or the like as a still image without stopping the rotation of the test piece 40 inside. As a result, it is possible to achieve real-time observation and measurement of crack generation, crack growth and growth behavior immediately before the test piece 40 breaks, and crack length.

《Configuration and method for detecting initial cracks in test specimens》
In the rotating bending fatigue test apparatus 80 of the present invention, it is possible to detect an initial crack generated in the test piece 40 while the rotation of the test piece 40 is continued. In order to detect this initial crack, the vicinity of the weakest part of the test piece 40 is imaged as a still image over the entire circumference using the method described above. The configuration and method will be described in detail below with reference to FIGS. 2 (a) and 2 (b) and FIG.

  When detecting an initial crack generated in the test piece 40, the gear portion 12 shown in FIG. 2A is driven by a rotation driving means (shown as 16 in FIG. 1) not shown in FIG. Is rotated counterclockwise. Further, as described above, the magnetic sensor 14 is driven by a servo motor (not shown) (shown as 10 in FIG. 1) and rotates in the direction opposite to the rotation direction of the gear unit 12, that is, in the clockwise direction on the paper surface of FIG. It is rotated.

  Generally, the test piece 40 used for the rotational bending fatigue test has a cylindrical shape. Moreover, the weakest part is a position indicated by a line WW in FIG. 5A, and a crack is generated in the weakest part having a circular cross section. For this reason, the imaging means 22 and / or the optical enlargement means 24 (hereinafter also referred to as “imaging means 22 etc.”) shown in FIG. 5A is a predetermined position where the weakest part of the test piece 40 can be photographed. It is arranged. Further, the pulse light emitting unit 20 is disposed at a predetermined position where the weakest part of the test piece 40 can be irradiated.

  Under the above configuration, first, the weakest part of the test piece 40 is imaged with the phase shown in FIG. At this time, the magnetic sensor 14 detects the left end surface of the convex portion A of the gear portion 12 and is positioned at a phase of 1 shown in FIG. Further, the imaging means 22 or the like receives the pulse signal Sp from the magnetic sensor 14, and the phase of the left end surface of the convex portion B of the gear portion 12, for example, the surface of the test piece 40 shown in FIG. The phase indicated as 40a is imaged.

  Next, as shown in FIG. 2B, the magnetic sensor 14 is rotated from the phase 1 shown in FIG. 2B to the phase 2 and has rotated at least one time as the gear portion 12 rotates. The left end surface of the convex portion A is detected. The imaging means 22 and the like receive a pulse signal Sp output from a pulse emission control means (not shown) (not shown in FIG. 1) by this detection, and a phase different from the previously captured phase, for example, FIG. The phase shown as 40b on the surface of the test piece 40 shown in FIG.

  The above-described procedure is repeated, and the magnetic sensor 14 is rotated in the clockwise direction (direction indicated by the black arrow) on the paper surface of FIG. 2B, and the convex portion has the phase 3 and phase 4 shown in FIG. The left end surface of the sheet A is detected, and the output voltage value V for generating the pulse signal Sp is sequentially output to a pulse light emission control means (shown as 28 in FIG. 1).

  Further, the imaging means 22 and the like receive the pulse signal Sp output from the output of the pulse light emission control means, and set the imaging location of the test piece 40 in the counterclockwise direction (the direction of the white arrow in FIG. 2B). ), The different phases of the test piece 40 are sequentially imaged.

  By repeating the above-described procedure, the weakest part of the test piece 40 is imaged over the entire circumference. Image data picked up by the image pickup means 22 and the like are transmitted to and recorded in the computer device 30 provided in the rotational bending fatigue test device 80 described later in detail. In the above description, the method of imaging the entire circumference of the weakest part of the test piece 40 once has been described. However, this imaging is continuously performed at least until an initial crack is detected.

  Image data of still images continuously captured by the imaging means 22 and the like are recorded in the computer apparatus 30 and are sequentially subjected to image analysis in detail by a method described later. Thereby, the detection of the initial fatigue crack which generate | occur | produced in the test piece 40 can be achieved.

  In addition, the phase in which the initial fatigue crack has occurred in the test piece 40 is also detected at the same time by the image analysis by the computer 30 in the above process. Thereby, it is possible to shift to the fixed point observation such as the crack while continuing the test without stopping the rotation of the test piece 40.

  More specifically, when the occurrence and phase of the initial fatigue crack generated in the test piece 40 are detected, the magnetic sensor 14 is fixed at a predetermined position by driving the servo motor 16 and is cracked by the method described above. Only the periphery of the image is continuously imaged. Thereby, without stopping the rotation of the test piece 40, the entire weakest part of the test piece 40 is shifted from the entire circumference observation to the fixed point observation such as a crack, and the progress of the crack is continuously observed. be able to.

  Note that the imaging means 22 and the pulse light emitting unit 20 may be moved in the direction of the rotation axis of the test piece 40 as necessary. Thereby, the imaging position of the imaging means 22 and the irradiation position of the pulse light emitting unit 20 can be made more appropriate, and the crack and the like can be set at the center of the imaging range. As a result, the progress of the crack is clear. It becomes possible to observe by simple still imaging.

  In addition, the movement of the test piece 40 in the direction of the rotation axis of the imaging means 22 and the pulse light emitting unit 20 described above may be manually performed, for example, electrically performed by combining a motor (not shown) and a ball screw. Also good. Moreover, it is also possible to automatically move to the optimal position for imaging the initial fatigue crack detected by the computer 30 using the data analyzed by the computer 30 for this movement.

《Configuration of pulsed light emitting part for irradiating the specimen of rotating bending fatigue test》
In the rotating bending fatigue test apparatus 80 of the present invention, at least two pulse light emitting sections 20 are arranged in the outer circumferential direction of the test piece 40 with respect to the observation axis (imaging direction) of the imaging means 22 and / or the optical magnification means 24, respectively. It is desirable to arrange them with substantially the same angle. Hereinafter, the configuration will be described in detail with reference to the drawings.

  The rotational bending fatigue test apparatus 80 of the present invention and the test piece 40 generally used for the rotational bending fatigue test have a cylindrical shape. Further, as described above, the weakest portion is a position indicated by a line WW in FIG. 5A, and a crack is generated in the weakest portion having a circular cross section.

  For this reason, in the rotating bending fatigue test apparatus according to the embodiment of the present invention, the observation means of the imaging means 22 and / or the optical magnification means 24 shown in FIG. (Imaging direction) When a light source is arranged on the same axis as S and irradiated with pulsed light, reflected light from only a part of the test piece 40 reaches the imaging element included in the imaging means 22.

  4C and 4D, which are schematic diagrams illustrating a light source in the rotating bending fatigue test apparatus according to the embodiment of the invention, that is, a test piece imaged by irradiation from the pulse light emitting unit 20. As illustrated in FIG. 4D, only a part of the surface of the test piece 40 is imaged. For this reason, when the crack propagates beyond the light irradiation range of the light source, it is difficult to observe the entire “crack” that is generated and propagated by the rotating bending fatigue test from the still image captured by the imaging means 22. It becomes.

  As shown in FIG. 4A, the pulse light emitting unit 20 in the rotating bending fatigue test apparatus 80 according to the embodiment of the present invention includes two pulse light emitting units 20, an imaging unit 22, and / or an optical magnifying unit 24. With respect to the arrangement direction S, the test pieces 40 are arranged so as to be inclined at substantially the same angle W in the outer peripheral direction of the test piece 40.

  In this embodiment, as shown in the photograph of the pulse light emitting unit 20 viewed from the direction of the arrow R shown in FIGS. 4A and 4A, the light emitting diode 20a as the light source is transferred to the test piece 40. 4 rows in the circumferential direction and 3 rows in the direction of the rotation axis are arranged as the pulse light emitting section 20, which are arranged at positions inclined by substantially the same angle W in the rolling direction of the test piece 40. ing.

  As described above, as illustrated in FIG. 4C, the light from the pulse light emitting unit 20 is evenly distributed to a range sufficient to observe the entire “crack” generated and propagated in the test piece 40 by the rotating bending fatigue test. In addition, it is possible to irradiate with a sufficient amount of light for observation. As a result, it is possible to capture the occurrence of cracks, growth behavior, crack length, etc. on the surface of the test piece 40 as a clear still image, and to observe and measure in real time.

  In the present embodiment, the light source is the light emitting diode 20a, but the type of the light source is not limited to this. As described above, the light source may be any light source as long as it has good responsiveness to the pulse signal Sp as the light emission command signal and can obtain sufficient luminance for imaging by light emission for a very short time. Laser light or the like can be used. Moreover, you may combine the kind of light source.

  In addition, by the above-described method, it is also possible to observe a crack or the like in a three-dimensional manner from two still images such as a crack or the like that have been imaged at intervals. The principle is based on so-called stereoscopic vision. For example, the parallel method, the crossing method, etc. are used, and image processing is performed by a computer or the like, so that two still images are taken with a time interval and images of the crack location. From the image, 2.5D data of a three-dimensional image such as a crack can be created and displayed on a screen (not shown).

<< Structure and method for reducing the rotation speed of the test piece before the test piece breaks >>
Further, the rotating bending fatigue test apparatus 80 of the present invention continuously captures the occurrence and progress of cracks in the test piece 40 in real time, automatically predicts the fracture time of the test piece 40, and the result thereof. Based on the above, it is possible to reduce the rotation speed of the test piece 40 to a predetermined rotation speed before the test piece 40 breaks. Hereinafter, the configuration and method will be described with reference to the drawings.

  As shown in FIG. 1, the rotating bending fatigue test apparatus 80 includes a computer apparatus 30 that records a still image captured by the imaging unit 22 and that can analyze the still image. With the configuration described above, still image data picked up by the image pickup means 22 is stored and recorded in the computer device 30.

  By comparing and analyzing still images such as cracks that have been accumulated and recorded over time, the generation of cracks and the size of cracks, specifically the length and / or width, progress. The speed can be measured in real time. The image analysis means can be implemented by appropriately using the configuration disclosed in the prior art document (Patent Document: Japanese Patent Laid-Open No. 5-256632), and detailed description thereof is omitted. .

  Briefly explaining the configuration of the above prior art document, in the metal member damage inspection apparatus for automatically determining the remaining life of the metal member, a metal member (corresponding to the test piece 40 of the present invention) is set in the inspection apparatus, An image of an optical microscope is picked up by a video camera and processed by an image processing device. The computer (corresponding to the computer apparatus 30 of the present invention) determines whether or not a crack has occurred as a damage to the shaft based on the image-processed data. When this computer recognizes a crack, it determines the shape of the crack by connecting it to another crack, combining it, etc., analyzes the crack distribution, and analyzes the crack distribution. The maximum length is calculated.

  In general, it is known that a crack generated in a test piece in a material fatigue test progresses at an accelerated rate as the test piece approaches. The computer apparatus 30 included in the rotating bending fatigue test apparatus 80 of the present invention previously stores the crack length data (hereinafter referred to as an index of the fracture time) for at least the material of the test piece 40 to be subjected to the rotating bending fatigue test. , Also referred to as “breaking time prediction data”).

  The fracture time of the test piece 40 is automatically predicted by comparing the fracture time prediction data with the maximum crack length obtained as a result of image analysis by the above-mentioned means by the computer 30 as needed. It becomes possible.

  The rotary bending fatigue test apparatus 80 of the present invention shown in FIG. 1 is based on the predicted breaking time of the test piece 40 described above, and the rotational driving means 10 that rotationally drives the test piece 40, that is, the test piece 40. The load is determined from a rotational speed of approximately 20000 to 30000 revolutions / minute to a predetermined rotational speed, for example, the Japanese Industrial Standard (JIS) standard number “JIS Z 2274” and the name “Rotating Bending Fatigue Testing Method for Metallic Materials”. The rotation speed is reduced to a rotation speed corresponding to “1000 to 5000 times per minute”, which is a repetition speed of.

  As described above, in the rotating bending fatigue test apparatus 80, the test piece 40 is rotated at a high speed of approximately 20000 to 30000 rotations / minute in a state where a bending load is applied to the test piece 40 in order to accelerate the test. For this reason, the temperature of the test piece 40 rises due to friction between molecules constituting the test piece 40 or the like. In particular, when the crack progresses and the fracture time approaches, the speed of the test piece 40 at which the crack progresses increases, and the cross-sectional area of the test piece 40 near the crack decreases. For this reason, the load (stress) concentrates in the vicinity of the crack of the test piece 40, and the temperature increase gradient becomes steeper.

  When the vicinity of the crack of the test piece 40 becomes high temperature, when the test piece is made of metal, a change in the hardness of the test piece 40 occurs particularly in the vicinity of the “crack”, so-called work hardening or softening occurs. To do. This makes it difficult to obtain accurate test results.

  In the rotating bending fatigue test apparatus 80 of the present invention, the rotational speed of the test piece 40, that is, the rotational speed of the rotary drive means 10 is set at a time point a predetermined time before the predicted fracture time of the test piece 40. For example, the speed is decreased to 1000 to 5000 revolutions / minute. Thereby, the temperature of the test piece 40 in the vicinity of the crack is lowered to the temperature of the test piece in the normal rotational bending fatigue test method. As a result, it is possible to achieve at least a test result equivalent to a normal test method.

  In addition, as a method for determining the predetermined time before the breaking time of the test piece 40 for setting the time for reducing the rotation speed of the rotation driving means 10 as described above, as an example, based on a previous test result. However, the present invention is not limited to this.

  Moreover, it is desirable that the rotating bending fatigue test apparatus 80 of the present invention includes a means for detecting the occurrence of cracks by applying a current to the surface of the test piece 40. For example, a high frequency current is applied at a constant voltage from both ends of the test piece 40 by a voltage generating means (not shown), and a change in the magnitude of the current flowing on the surface of the test piece 40 is measured by an ammeter (not shown). To do.

  When the current value changes, for example, when a minute flaw, that is, an initial “crack” occurs on the surface of the test piece 40, the electrical resistance of the surface of the test piece 40 increases. This is due to the so-called skin effect of high-frequency current, in which the higher the high-frequency current frequency is, the more current flows on the metal surface. Due to this increase in electrical resistance, the amount of current detected by the ammeter is reduced. A case where a decrease in the amount of current is detected can be detected as the occurrence of a crack.

<< Configuration of tensile / compressive fatigue test equipment >>
Next, what is used for the tension / compression fatigue test of the fatigue test apparatus of the present invention will be described with reference to FIGS. 7 to 8 (hereinafter, also simply referred to as “tensile / compression fatigue test”). Even in this tension / compression fatigue test, the crack growth can be measured without stopping the tension / compression of the specimen, and the time required for the tension / compression fatigue test can be greatly shortened compared to the normal test method. . In addition, after the occurrence of cracks on the surface of the test piece used for tensile / compression fatigue tests, the growth behavior and the length of the “crack”, at least after the “crack” occurred in the test piece, the test piece It is possible to observe in real time until fracture occurs, and at the same time, obtain a test result that is equivalent to or more accurate than a normal tensile / compressive fatigue test.

  In the tensile / compression fatigue test, a tensile load (load) is applied to a specified specimen (metal material), a tensile deformation of a specific strain amount is applied, the load (load) is once removed, and the compression load (load) is applied as it is. ) Is applied for compressive deformation, or after applying compressive deformation, tensile deformation is applied. In FIG. 7, the schematic (schematic diagram) of the principal part of the embodiment of the present tensile / compression fatigue test 100 is shown. In the present tensile / compression fatigue test 100, a vibrator 102 (vibration means) that applies a tensile load / compressive load (axial load) to the test piece 101 by using a vertical amplitude is used.

  A fatigue crack 103 that is generated and propagated in the test piece 101 is captured as a clear still image under a good light emission state. In addition, the fracture time of the test piece 103 is estimated based on the captured still image data, and the amplitude speed of the test piece is reduced to a predetermined speed before the test piece 103 breaks. Yes.

  Further, in the tensile / compression fatigue test 100, one end of the test piece 101 is fixed to the vibrator 102 by bolt fastening or the like, and the other end is also fixed to the tensile / compression fatigue test 100 (not shown) (FIG. 7). 100a). The vibration exciter 102 receives a vibration signal generated from the load control device 108 and applies a load or displacement using a hydraulic pressure (not shown) or a piezoelectric element such as a motor or a piezo element (used in an ultrasonic fatigue test described later). It is controlled by a desired pattern (sine wave, rectangular wave, triangular wave, etc.), and a repeated axial load is applied to the test piece 101.

  The load control device 108 transmits a reference signal for synchronization (synchronization signal in the figure) to the synchronization control device 109 in synchronization with the excitation signal to the shaker 102. Upon receiving the synchronization signal from the load control device 108, the synchronization control device 109 controls the synchronization signal (light source synchronization signal in the figure) to the power amplifier 110 and the control signal (see FIG. Middle image collection control signal).

  FIG. 8 is a block diagram showing an overview of the synchronization control device 109. The synchronization control device 109 receives the synchronization signal from the load control device 108 and amplifies the voltage by the voltage conversion circuit 109a. The voltage-amplified signal is shaped into a pulse signal by the pulse shaping circuit 109d, and is divided to a desired frequency by the frequency dividing circuit 109b. Frequency division is a method used when the light source 104 and an image collection device 107 (to be described later) cannot be synchronized as they are, such as when the excitation to the test piece 101 is a high frequency such as an ultrasonic wave. The ultrasonic fatigue test will be described later.

  The pulse signal generated by the frequency dividing circuit 109b is transmitted to the power amplifier 110 by the delay control circuit 109c to the irradiation timing of the light source (irradiation source) 110 and the light source synchronization signal with the pulse peak delayed according to this. At the same time, the delay control circuit 109 c transmits an image collection control signal linked to the light source synchronization signal to the image collection device 107.

  Please refer to FIG. 1 again. Upon receiving the light source synchronization signal from the synchronization control device 109, the power amplifier 110 provides or cuts power to the light source 104. As a result, the light beam 104 irradiates the crack on the surface of the test piece 101 and the site where the crack propagates (hereinafter also simply referred to as “crack”). As the light source 104, an LED, a halogen lamp, a xenon lamp, a metal hydride lamp, or the like is used.

  The imaging unit 105 can capture a predetermined position of the test piece 101 irradiated with light from the light source 104 as a still image. The imaging means 105 detects light from the crack 103 or the like of the test piece 101, and the image collecting device 107 provided with a photoelectric conversion element (imaging element) causes the test piece 101 to crack or propagate the crack. Record the image as electronic data. For example, a CMOS image sensor or a CCD image sensor is used as the image sensor. In addition, the imaging unit 105 includes an optical enlarging unit (lens or the like) 106 that enables the imaging of the test piece 101 by combining a telescope and a microscope. As a result, the periphery of the crack or the like 103 of the test piece 101 is enlarged, and the image collecting device 107 can selectively magnify and image the crack or the like.

  As described above, the image collection device 107 receives the image collection signal linked to the light source synchronization signal to the power amplifier 110 and controls the imaging timing, so that it is possible to perform imaging in accordance with the irradiation of the test piece 101.

  The image data of the test piece 101 collected by the image collection device 107 is transmitted to the image processing device 112. The image processing device 112 receives the image data, and performs image processing such as filtering processing (filtering operation), difference processing, pattern extraction processing, and arithmetic processing on the image data. , Output as raw data. The output data is received and displayed on a display device 113 such as a measurement result display.

  In addition, the image processing apparatus 112 transmits a positioning signal for adjusting the position of the imaging unit 105 to the positioning apparatus 111. The position of the imaging means 105 in the XYZ directions is adjusted by the positioning signal. For example, in the image processing performed by the image processing apparatus 112, when the appropriate imaging position of the crack is shifted, the position of the imaging means 105 is moved (tracked) so that the tip of the crack is positioned at the center of the image. It should be noted that the initial crack 103a is preferably attached to the test piece 101 as the initial crack tip position (tracking origin position). The positioning device 111 is provided with a piezoelectric element such as a piezo element and an actuator, and drives the imaging unit 105 by converting a positioning signal into a force.

  As described above, in the present tension / compression fatigue test apparatus 100, the image capturing apparatus 107 that collects the crack image of the test piece 101 photographed by the imaging means 105 by the synchronous control apparatus 109 and the axial load is applied to the test piece 101. The dynamic test piece 101 image during the fatigue test can be acquired and measured as a static image by synchronizing with the load control device 108 of the vibration exciter 102. Therefore, it is possible to observe and measure crack generation and growth behavior of the test piece 101 in real time. Further, the tip position of the crack is monitored by the image processing device 112 and the positioning device 111, and the position of the image pickup means 105 is adjusted to enable tracking and automatic measurement of crack propagation.

As already described, the present tensile / compression fatigue test apparatus can be applied to an ultrasonic tensile / compressive fatigue test that has been developed in recent years. When applied to an ultrasonic fatigue test, a piezoelectric element is used for the vibrator 102, and resonance (around 20,000 times / s) is generated by longitudinal wave vibration of 20 kHz ± 500 Hz, for example. A repeated stress σ (150 to 700 MPa) is applied to the position of the starting crack 103a. Note that the above-described frequency division is, for example, divided by 1/100 by the frequency dividing circuit 109b and formed at around 200 Hz. In addition, although not shown, the test piece 101 may be cooled by blowing air to suppress the strength reduction due to heating.

  As mentioned above, although the embodiment about the fatigue test apparatus of this invention was described, this invention is not limited to this, In the range which does not deviate from the mind and teaching as described in a claim, a description, etc. It will be understood by those skilled in the art that variations and improvements can be obtained.

DESCRIPTION OF SYMBOLS 10 Rotation drive means 10a Rotation main shaft of rotation drive means 12 Gear part 14 Magnetic sensor 15 Sensor support part 16 Servo motor 18 Chuck part 20 Pulse light emission part 22 Image pickup means 24 Optical expansion means 26 Interval detection means 28 Pulse light emission control means 30 Computer apparatus 32 Load-loading part 32a Adapter 32b Hanging part 32c Weighting part 40 Test piece 40a Crack starting point part (initial crack)
80 Rotating Bending Fatigue Testing Equipment 100 Tensile / Compression Fatigue Testing Equipment 101 Specimen 102 Exciter (Excitation Device)
103 crack 103a origin crack 104 light source (irradiation device)
105 Imaging means 106 Optical magnifying means (lens)
Reference Signs List 107 Image collecting device 108 Load control device 109 Synchronization control device 109a Voltage conversion circuit 109b Frequency division circuit 109c Delay control circuit 109d Pulse generation circuit 111 Positioning device 112 Image processing device 113 Display devices A to I Convex portion of gear portion outer periphery V Magnetic sensor Output voltage value of (magnetoresistance effect element) Sp Pulse signal for synchronization of pulse emission and imaging

Claims (15)

A fatigue test device that measures rotational bending fatigue by gripping the end of the test piece with a load and rotating the shaft,
Imaging means disposed at a position where the shape change can be observed based on the angle information in the rotational direction of the initial shape change detected on the surface of the test piece and the position information in the axial direction;
A light source capable of irradiating a test piece for a short time,
While the test piece is rotating, the light source emits light for a short time and irradiates the test piece to continuously observe the still image of the shape change of the surface of the test piece with the imaging means, and track and compare changes over time A fatigue test apparatus characterized by predicting the rupture time of the test piece. The light emission of the light source and the imaging of the imaging means are synchronized when the test piece reaches the phase of rotation of the test piece that can capture the shape change on the surface of the test piece with the imaging means. The fatigue test apparatus according to claim 1. The light source is an LED stroboscope,
The rotational drive source of the test piece is a servo motor,
A gear cooperating with the rotation of the servo motor;
A magnetic sensor disposed around the gear and having a magnetoresistive effect element;
Based on the relationship between the angular position of the magnetic sensor and the position of the teeth constituting the gear, the change in the resistance value of the magnetoresistive element of the magnetic sensor is converted into a voltage change, and this change is converted into a pulse signal. The fatigue test apparatus according to claim 1, wherein an input signal for LED emission is generated. The light source is subdivided into fine time at a time interval synchronized with the rotation speed of the test piece and emits light, and the imaging element is photographed as a plurality of images subdivided in one direction on the test piece in the rolling direction, The bending fatigue test apparatus according to claim 2 or 3, wherein the shape change of the surface of the test piece is stereoscopically viewed by comparing the images. A high-frequency current is applied at a constant voltage from both ends of the test piece, the change in the magnitude of the current flowing on the surface is measured, and it is estimated that the initial shape change of the test piece surface occurred when the current decreased. The fatigue test apparatus according to any one of claims 1 to 3, wherein The fatigue test apparatus according to any one of claims 1 to 5, wherein when the fracture time of the test piece is predicted, the rotation speed of the test piece is decreased. The fatigue test apparatus according to claim 1, wherein the light source is a light emitting diode, discharge light emission, or pulsed laser light. The fatigue test apparatus according to any one of claims 1 to 7, wherein the optical axis of the light source and the light receiving device of the imaging means are arranged at the same angle with respect to the test piece. A fatigue testing device that performs tensile / compression measurement by applying repeated loads in the tension / compression direction to the end of the test piece,
Imaging means disposed at a position where the shape change can be observed based on the position information of the initial shape change detected on the surface of the test piece;
An irradiation source capable of irradiating the test piece with light for a short time;
With the test piece repeatedly loaded,
The test piece is irradiated with light from the irradiation source, a still image of the shape change of the surface of the test piece is collected by the imaging means, and the breaking time of the test piece is predicted by tracking and comparing the change with time. Fatigue testing equipment characterized by The fatigue test apparatus according to claim 9 is:
Take a crack image of the specimen,
Image collecting means for collecting a crack image of a test piece photographed by the imaging means;
Vibration means for applying the repeated load to the test piece;
Load control means for transmitting a control signal to the vibrator,
A fatigue test apparatus comprising: synchronization control means for controlling the image collection means and the load control means to be synchronized. The synchronization control device collects a static test piece crack image by transmitting a signal synchronized with a signal for transmitting power to the irradiation source as a signal for controlling the image collecting means. The fatigue test apparatus according to claim 10. The said excitation means is provided with the piezoelectric element which vibrates with the period in an ultrasonic range, receives the signal from the said load control means, and gives a load to a test piece, The Claim 13 characterized by the above-mentioned. Fatigue test equipment. The said vibration means includes a hydraulic / pneumatic drive or electromagnetic or motor drive actuator, and receives a signal from the load control means to apply a load to the test piece. The fatigue test apparatus described. The fatigue test apparatus according to claim 10, wherein the synchronization control unit includes a frequency dividing circuit that divides a signal from the load control apparatus. The fatigue test apparatus according to any one of claims 10 to 14,
Image processing means for receiving and processing image data of the test piece from the image collecting means,
The image processing means transmits a positioning signal for positioning the position of a crack in the test piece in the image data,
A fatigue testing apparatus comprising positioning means for receiving a positioning signal and moving the imaging means to an appropriate position.