JP6657495B2 - Fatigue test equipment - Google Patents

Description

The present invention, in the surface of the test piece, generation of Ki occurring rotating bending fatigue test and tensile compression fatigue test Crack and or growth behavior, can relate the length of the crack in the fatigue test equipment capable of observing and measuring in real time.

  When performing a rotating bending fatigue test or a tensile / compression fatigue test on a test piece of a metal material, not only is the stress amplitude and the number of repetitions of fracture (so-called SN characteristics) detected, but the "fatigue" It is known that more information about fatigue properties can be obtained by also observing changes in "cracks".

  Heretofore, in the observation of fatigue crack initiation, growth, and changes in fatigue cracks until the final fracture of such a test piece, it was common to follow the physical shape change by a replica method. The replica method is a method of observing the shape of a replica that has been pasted on the surface of a test piece to copy the surface shape. Here, the replica method will be described by way of example. First, when using a film-shaped acetylose piece as a replica material as a replica, this is immersed in an organic solvent such as methyl acetate or acetone (hereinafter, referred to as "acetone or the like"). Paste on the crack observation surface. Then, the sample is left for a predetermined time (usually 1 to 1.5 minutes), and after the acetone or the like is volatilized from the acetylose piece, the acetylose piece is peeled from the test piece. Next, on the adhesive surface of the double-sided tape of the fixed base where the double-sided tape was pasted on the glass plate prepared in advance, it was stuck on the replica side with the contact side with the test piece facing up, and then the replica was optical microscope Observe and photograph with. A series of operations leading to this photographing is continuously performed until it is possible to clearly determine that a crack has occurred on the surface of the test piece itself, and the image record is traced back to the past. The progress from the initial stage of crack initiation can be tracked in the form of a replica shape change. Further, by continuously testing the test piece, it is possible to continuously observe the test piece until it breaks.

  However, the above-mentioned replica method requires experience in the method of attaching a replica prepared using a film-like acetylose piece, and bubbles are interposed when the replica is attached to the surface of the test piece, and the shape of the crack is not reflected. In many cases, there are difficulties. In addition, in the replica method, it is necessary to suspend the test for a predetermined time for each operation such as attaching a replica piece, and there is a demand for observing a crack change without interrupting the test. Further, for example, in recent years, in a tensile / compression fatigue test, the test speed has been increased, for example, by vibrating a test piece with an ultrasonic wave, so that it is difficult to perform real-time measurement by visual observation.

Furthermore, especially when the replica method is used to observe fatigue cracks in the rotating bending fatigue test, the specimens are usually cylindrical, and the parts where fatigue cracks occur are curved, so they are extremely sticky. put not difficulty. For this reason, the discovery of the crack there is a problem that requires experience. When the specimen was irradiated with light coaxially with the observation axis of the metallurgical microscope to detect the occurrence of cracks, the light hit only the top of the curved surface of the specimen, and the entire fatigue crack was Can not be observed. For this reason, there was a problem that discovery of a crack required experience.

  On the other hand, it is conceivable to observe the specimen surface in synchronization with the vibration of the tensile / compression fatigue tester or the rotation of the rotary bending fatigue tester without interrupting the test. It is necessary to use a stroboscope that can emit light for an extremely short time. 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. In addition, there is also a problem that the light emission timing is shifted and the luminance is insufficient, so that good observation (photographing) cannot be performed.

  In addition, in the ultrasonic tensile / compression fatigue test developed in recent years in the tensile / compression fatigue test, once the device is started and stopped to observe the crack of 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 the problem that the test results changed and were affected.

  Furthermore, in the tensile / compression fatigue test, there is a demand to measure the tip strain due to the change in the crack opening.Currently, only the strain due to the static load on the test specimen is measured. Has not been measured.

  The present invention has been made in view of the above-described problems, and has been described in terms of the occurrence and growth behavior of "cracks" on the surface of a test piece such as a metal material in a rotational 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 photographing and observing and measuring the length in real time in a good light emitting state.

  The present invention provides a rotary bending fatigue test apparatus in which a load is applied to a test piece to grip an end thereof and rotate the shaft. Specifically, an imaging means arranged at a position where the shape change can be observed based on the rotational angle information and the axial position information of the initial shape change detected on the surface of the test piece; A light source capable of irradiating the test piece for a short time, and in a state where the test piece is rotating, the light source emits light for a short time to irradiate the test piece, thereby changing the shape of the surface of the test piece by the imaging means. Of the test piece is predicted by continuously observing the still images of the above and tracking and comparing the changes over time.

  According to this rotary fatigue bending test apparatus, the shape change (typically, "crack" (hereinafter, referred to as "crack")) on the surface of a test piece such as a metal material in the rotary bending fatigue test is performed. The growth behavior and the length of the "crack" can be observed and measured by photographing in real time in a good light emitting state.

  Further, when the test piece reaches a phase of rotation of the test piece which can image a “crack” on the surface of the test piece by 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 rotation drive source of the test piece is a servomotor, and the rotary bending fatigue device includes a gear cooperating with the rotation of the servomotor, and a gear around the gear. And a magnetic sensor having a magnetoresistive element, wherein the resistance value of the magnetoresistive element of the magnetic sensor is based on a relationship between an angular position of the magnetic sensor and a position of a tooth forming the gear. Is converted into a voltage change, and the change is converted into a pulse signal, whereby an input signal for LED light emission can be generated.

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

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

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

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

  Further, it is preferable to reduce the rotation speed of the test piece when the break time of the test piece is predicted.

  By continuously observing the progress of `` cracks '' generated on the test piece, by predicting the rupture time, the temperature rise of the test piece due to high speed rotation with the bending load added is suppressed, and 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 as the short-time light source.

  Further, it is preferable that the optical axis of the light source and the light receiving device of the imaging unit 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 present invention is a fatigue test apparatus for performing tensile / compression measurement by repeatedly applying a load in a tensile / compressive direction to an end of a test piece,
Imaging means disposed at a position where the shape change can be observed based on the initial shape change position information detected on the surface of the test piece,
An irradiation source (for example, the light source 104 in the present embodiment) capable of irradiating the test piece with light for a short time,
In the state where the load is repeatedly applied to the test piece,
By irradiating the test piece with light from the irradiation source, a static image of the shape change of the surface of the test piece is collected by the imaging means, and the aging time of the test piece is measured by tracking and observing the change over time. Predict.

  According to this fatigue test apparatus, the occurrence of shape change (typically, "crack") on the surface of a test piece such as a metal material in a tensile / compression fatigue test, its growth behavior, and the length of "crack" Real-time photography and observation / measurement can be performed in a good light emitting state.

Specifically, this fatigue test apparatus takes a crack image of a test piece,
An image collecting means (for example, the image collecting apparatus 107 in the present embodiment) for collecting a crack image of the test piece photographed by the imaging means, and a vibration means (for example, in the present embodiment) for applying the repetitive load to the test piece. The exciter 102), a load control unit that transmits a control signal to the exciter (for example, the load control device 108 in the present embodiment), and the image collection unit and the load control unit are synchronized. And a synchronous control unit (for example, the synchronous control device 109 in the present embodiment) for controlling.

  Further, the synchronization control means transmits a signal synchronized with a signal for power transmission to the irradiation source as a signal for controlling the image collection means, so that the image collection device collects a crack image of a static test piece. be able to.

  In the fatigue test apparatus, the synchronization control device synchronizes the image collection device that collects a crack image of the test piece photographed by the imaging unit with the load control device that sends a signal for applying an axial load to the vibration unit. Thus, the dynamic shape change during the fatigue test can be acquired and measured as a static image. Therefore, the crack generation and growth behavior of the test piece can be observed and measured in real time. Further, the strain at the crack tip at a specific opening angle of the crack during the fatigue test can be observed and measured in real time.

  Further, the vibrating means includes a piezoelectric element which vibrates by ultrasonic waves, and applies a load to a test piece in response to a signal from the load control means, or a hydraulic / pneumatic driving, electromagnetic or motor-driven actuator. And a method of receiving a signal from the load control means and applying a load to the test piece.

  The present fatigue test apparatus can be applied not only to a case where a test piece is vibrated by a hydraulic pressure or a motor but also to an ultrasonic fatigue test apparatus which 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 stopping and starting the fatigue test apparatus, and the conditions of the fatigue test do not change before and after the start and stop.

  Further, the synchronization control device may include a frequency dividing circuit that divides a signal from the load control device.

  Even when the test piece is vibrated at a high frequency such as an ultrasonic wave, the test piece can be converted and measured to a degree that can correspond to the irradiation source or can collect an image.

The image processing apparatus further includes an image processing unit (for example, the image processing apparatus 112 according to the present embodiment) that receives the image data of the test piece from the image collection unit and performs image processing.
The image processing means transmits a positioning signal for positioning the position of the crack in the test piece in the image data,
Positioning means (for example, the positioning device 111 in the present embodiment) for receiving the positioning signal and moving the imaging means to an appropriate position may be provided.

  Thus, the position of the tip of the crack in the test piece is monitored, and the position of the imaging means is adjusted as appropriate, so that the crack growth can be tracked and automatically measured.

  According to the fatigue test apparatus of the present invention, the occurrence and growth behavior of a "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, and the length of the "crack", It can observe and measure by taking a picture in real time in the light emitting state.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the structure of the principal part of the rotary bending fatigue test apparatus which concerns on one Embodiment of this invention. FIG. 2 is a schematic view for explaining a configuration in which rotation of a test piece and pulsed light emission are synchronized with each other in order to image a crack in the rotating bending fatigue test apparatus according to one embodiment of the present invention. 3 is a schematic diagram illustrating a configuration for generating a pulse signal for capturing a crack as a still image in the rotary bending fatigue test apparatus according to one embodiment of the present invention. FIG. 1 is a schematic diagram illustrating a configuration of a pulse light emitting unit in a rotary bending fatigue test device according to an embodiment of the present invention, and a schematic diagram illustrating a test piece imaged by irradiation from a light source. 1 is a schematic view illustrating a rotary bending fatigue test apparatus according to an embodiment of the present invention and a test piece used in a general rotary bending fatigue test. It is the schematic which shows the structure of the principal part of the load application part in the rotary bending fatigue test apparatus which concerns on one Embodiment of this invention. A schematic diagram (schematic diagram) of a main part of another embodiment of the tensile / compression fatigue test of the present invention is shown. FIG. 8 is a block diagram illustrating an outline of the synchronization control device illustrated in FIG. 7.

  First, among the fatigue test devices of the present invention, those used for a rotary bending fatigue test will be described (hereinafter, also simply referred to as “rotary bending fatigue test device”). This rotary bending fatigue tester can greatly reduce the time required for the rotary bending fatigue test compared to the normal test method without stopping the rotation of the test piece by using the following two major means. I 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" were determined at least after the "crack" occurred in the test piece. Obtain test results that are equivalent to or more accurate than the normal rotating bending fatigue test method, while enabling real-time observation and measurement (hereinafter simply referred to as “observation etc.”) until fracture occurs To achieve.

  One of the above-mentioned means is a means for capturing a crack generated in a specimen rotating at a high speed (approximately 20,000 to 30,000 revolutions / minute) and propagating as a clear still image under a favorable light emitting state. It is. The other one is to infer the rupture time of the test piece based on the data of the still image captured above, and to set the rotation speed of the test piece to a predetermined rotation speed before the test piece breaks. It is a means to reduce the speed.

  As described above, in the conventional rotating bending fatigue test method, it is necessary to temporarily stop the rotation of the test piece and observe it in order to observe the crack by the replica method or visually. However, when the rotation of the test piece is stopped during the test, a tensile load is applied to a specific location in the circumferential direction of the test piece. As a result, damage (stress concentration portion) not caused by the bending fatigue test occurs on the test piece, which may affect the test result, which is not preferable.

  Therefore, the test result under the most desirable test conditions, that is, the rotation speed of the test piece reaches a predetermined speed, and after applying a predetermined load to the test piece, until the test piece breaks, or a predetermined number of times. Until the application 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 above-mentioned predetermined load is erroneously applied to the test piece, for example, during the step of stopping the rotation of the test piece. For example, there is a concern that the rotation of the test piece should be stopped with the load applied while the rotation of the test piece should be stopped after the load is removed, so that accurate test results cannot be obtained. is there.

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

《Configuration of rotating bending fatigue test equipment》
As a prerequisite for explaining a method for observing a crack or the like in the above-described rotary bending fatigue test apparatus of the present invention, the configuration of the rotary bending fatigue test apparatus 80 of the present invention is changed to a rotary bending fatigue test apparatus according to an embodiment of the present invention. FIG. 1 is a schematic view showing a configuration of a main part of a test apparatus, and FIG. 1 is a schematic view illustrating a rotary bending fatigue test apparatus according to an embodiment of the present invention and a test piece generally used in a rotary bending fatigue test. 5 and FIG. 6 which is a schematic view showing a configuration of a main part of a load applying unit in the rotary bending fatigue test apparatus according to one embodiment of the present invention, will be described in detail.

  As shown in FIG. 1, the rotary bending fatigue test apparatus 80 includes at least a rotation driving unit 10 for generating rotation of the test piece 40, and a rotation spindle 10 a on one side of the rotation spindle 10 a of the rotation driving unit 10. A gear portion 12 fixed to the core, a magnetic sensor 14 rotatably disposed around the gear portion 12, and a magnetic sensor 14 disposed coaxially with the rotating main shaft 10 a to attach the magnetic sensor 14 around the gear portion 12. A servomotor 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 servomotor 16 and carries the magnetic sensor 14. A sensor support portion 15 capable of rotating the arrangement position around the gear portion 12.

  The rotating bending fatigue test apparatus 80 of FIG. 1 also includes at least a chuck section 18 for gripping the test piece 40 on the side opposite to the side on which the gear section 12 of the rotary main shaft 10a of the rotary driving means 10 is provided, and a pulse signal. As a result, light having a short time width (hereinafter, also referred to as “pulse light”) is applied to a “crack” on the surface of the test piece 40 or a site where the crack propagates (hereinafter, also simply referred to as “crack etc.”). And a photographing unit 22 capable of capturing a predetermined position of the test piece 40 as a still image.

  The imaging unit 22 is capable of detecting light from a crack or the like of the test piece 40 and generating an electric charge, and includes, as an example, a photoelectric conversion element (not shown; hereinafter, also referred to as an “imaging element”). As the imaging element, for example, a CMOS image sensor, a CCD image sensor, or the like can be used. With this, it is possible to record an image of a crack or a crack propagation of the test piece 40 as electronic data.

  The imaging unit 22 includes an interval detection unit 26 that can measure a reception cycle of two signals. The interval detecting means 26 receives a pulse signal for causing the above-described pulse light emitting section 20 to emit light, and opens and closes a so-called shutter (not shown) provided in the imaging means 22 when there is no signal and when the signal is received. To switch at high response speed. As will be described in detail later, by providing the interval detecting means 26, the timing of the light emission of the pulse light emitting unit 20 and the imaging by the imaging means 22 can be adjusted so that the crack or the like of the rotating test piece 40 is the optimal phase for the imaging. Can be synchronized with the timing of

  It is preferable that the imaging unit 22 includes an optical magnifying unit 24 shown in FIG. 1 that enables a telescope and a microscope to be combined to magnify the test piece 40 and image it. Thereby, it becomes possible to enlarge the periphery of the crack or the like of the test piece 40 and selectively image the crack or the like by the imaging means 22.

  FIG. 5 illustrates a rotary bending fatigue test apparatus 80 and a test piece 40 generally used in a rotary bending fatigue test. FIG. 5 (a) shows the test piece 40 in advance as a crack starting point. FIG. 5B is a schematic view of a top view when the starting point portion 40a is provided, and FIG. 5B is a view showing the WW section shown in FIG. 5 (c) is an enlarged view of a region K shown in FIG. 5 (b) and schematically shows an example of a crack initiation point portion 40a.

  In the rotating bending fatigue test apparatus 80 of the present invention, the test piece 40 has a crack initiation part 40a serving as a starting point of a crack, and a crack generated and propagated from the crack initiation part 40a is observed. 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 and the growth of the crack are observed. It is possible.

  As will be described in detail later, there are a case where a crack initiation point portion 40a is provided in advance on the test piece 40 and a case where 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 unit 22 and / or the optical enlargement unit 24 and the pulse light emitting unit 20 described below can capture and irradiate the crack initiation point portion 40a, which is the weakest portion of the test piece 40, and its periphery. It is arranged in.

It is desirable that the chuck portion 20 be formed integrally from the same member as the main shaft 10a of the rotary drive means 10. Thus, the axis of the specimen 40 to be held one end thereof to the chuck portion 20 (rotational axis in the rotating bending fatigue test device 80), the eccentricity of the rotational axis of the main shaft 10a of the rotation driving means 10 As a result, a crack or the like of the test piece 40 that rotates at approximately 20,000 to 30,000 revolutions / minute can be more clearly imaged and observed while suppressing blurring.

  Further, as shown in FIG. 1, the rotating bending fatigue test apparatus 80 causes at least the pulse light emitting section 20 to emit light based on signals from the magnetic sensor 14 and the servomotor 16, and performs a test by the imaging means 22. The 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 later in detail, the use of the pulse signal Sp for pulse emission generated by the pulse emission control unit 28 makes it possible to optimally image cracks and the like on the surface of the test piece 40 with the imaging unit 22. Synchronizing the timing at which the phase reaches a proper phase, the timing at which the pulse light emitting section 20 emits light, and the timing at which the image is taken by the imaging means 22, images cracks and the like of the test piece 40 rotating at high speed (still image) It becomes possible to shoot as.

  FIG. 6 is a schematic diagram illustrating a configuration of a main part of a load applying unit that applies a load to the test piece 40 rotatable by the rotation driving unit 10 in the rotating bending fatigue test apparatus 80 according to the embodiment of the present invention. As shown in (1), in the rotating bending fatigue test 80, a load applying part 32 is disposed at the other end as a free end of the test piece 40 one end of which is gripped by the chuck part 18.

  The load applying part 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. And a suspension 32b for connecting the adapter 32a and the weight 32c. The weighting section 32c performs additional setting of the load according to the shape of the test piece 40 and the evaluation conditions.

<< Configuration and method for synchronizing pulse emission and imaging timing with rotation of test piece >>
In the rotary bending fatigue test apparatus 80 according to the present invention, as described above, the timing at which the crack on the surface of the test piece 40 or the portion where the crack propagates reaches the optimal phase for imaging by the imaging unit 22. In addition, by synchronizing the timing at which the pulse light emitting section 20 emits light with the timing of imaging by the imaging means 22, it becomes possible to capture a crack or the like on the surface of the test piece 40 rotating at high speed as a still image. I do.

  Regarding the configuration for realizing this synchronization and its method, FIG. 1 shows the rotation of a test piece and the pulse emission in order to image a crack in the rotary bending fatigue test apparatus according to one embodiment of the present invention. FIG. 2 which is a schematic diagram for explaining a configuration for synchronizing, and a configuration for generating a pulse signal for capturing a crack as a still image in a rotary 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 view for explaining a configuration for synchronizing rotation of a test piece and pulse emission 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. It is a schematic diagram. FIG. 2A shows a case where a crack initiation point portion 40a serving as a crack initiation point is provided in advance on the test piece 40, and an initial crack generated in the test piece during the test is confirmed. Is set as the crack origin 40a, and the observation is continued. In other words, the rotation of the component used for the fixed point observation after the position of the crack origin 40a is detected. 5 is a schematic diagram illustrating an example of a relative position in a direction.

  Until a 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 not-shown servo motor (shown as 16 in FIG. 1). Be moved. After the position of the crack initiation point 40a is detected, the magnetic sensor 14 shown in FIG. 2A is fixed by being supported by a servo motor (not shown).

  For example, in the case where the crack initiation point portion 40a is provided in advance on the test piece 40, in order to image the crack of the test piece 40 as a still image, a crack or the like on the surface of the test piece 40 is imaged by the imaging means 22. The configuration and method for synchronizing the timing at which the pulse light emitting unit 20 emits light with the timing of imaging by the imaging unit 22 at the timing when the optimal phase is reached will be described below. A configuration for detecting an initial crack generated in the test piece 40 while the test piece 40 is rotated will be described later in detail.

  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 on the outer periphery thereof at an equal pitch. In addition, the magnetic sensor 14 moves the rotation of the gear portion 12 to a position where the rotation of the gear portion 12 can be detected from a change in a magnetic field generated between the convex portions A to I (hereinafter, also simply referred to as “convex portion A or the like”). Are carried on the rotating shaft of a servomotor 16 via a sensor support 15 shown in FIG.

  In the rotary 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 which is a crack starting point in advance, as described above, the servomotor 16 is not driven, and The sensor 14 is fixed at a predetermined position by a servomotor 16 via a sensor support 16.

  When the rotation drive means 10 shown in FIG. 1 is driven and its rotary main shaft 10a rotates, the gear portion 12 fixed to one end (leftward in FIG. 1) of the rotary main shaft 10a 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 to generate a signal for light emission of the pulse light emission unit 20.

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

  The process of generating the signal for light emission will be described in detail with reference to FIGS. 3 (a) and 3 (b). As shown in FIG. 3A, a 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 as shown by a solid arrow in the drawing. Changes to

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

  The pulse signal Sp is sent from the pulse emission control unit 28 in accordance with the timing at which the phase in the rotation direction of the crack initiation point portion 40 a of the test piece 40 reaches the optimal phase for imaging by the imaging unit 22. The signal is transmitted to at least the pulse light emitting unit 20 shown in FIG.

  With reference to FIGS. 1 and 2A, a method of synchronizing the timing of pulse emission and imaging with the rotation of the test piece 40 using the pulse signal Sp will be described in detail. As described above, the test piece 40 having the crack initiation point portion 40a and the gear portion 12 are connected via the chuck portion 18 shown in FIG. In other words, the test piece 40 and the gear portion 12 are rotated while maintaining the same phase by the rotation drive of the rotation 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 initiation point portion 40a and the gear portion The test piece 40 is gripped by the chuck portion 18 in advance so that the surface in the rolling direction of the 12 convex portions B (the left side surface of the convex portion B on the paper surface of FIG. 2A) has the same phase.

  In addition, the imaging unit 22 and / or the optical enlarging unit 24 are also arranged in advance so as to be able to image the same phase as the surface in the rolling direction of the projection B, as illustrated in FIG. The pulse light emitting section 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 above state, the pulse signal Sp is output from the pulse emission control unit 28 shown in FIG. 1 and received by the pulse emission unit 20 and the interval detection unit 26 provided in the imaging unit 22, so that the pulse emission unit 20 Emits light, irradiates the crack initiation point portion 40a of the test piece 40 and the range in which the crack propagates, and the light reflected on the surface of the test piece 40 including the crack and the like is provided in the imaging means 22. The light is reflected in the direction of the image sensor.

  In addition, 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 as described above, and the light reflected by the crack or the like is The light reaches the image pickup device provided in the image pickup means 22.

  As described above, the pulse light is emitted from the pulse light emitting unit 20 to the crack or the like on the surface of the rotating test piece 40 in synchronization with the timing when the optimal phase for imaging by the imaging unit 22 is reached. The shutter is opened almost simultaneously with the irradiation of the pulse light, and the light reflected by the crack or the like reaches the image pickup device provided in the image pickup means 22. As a result, the above-described cracks and the like of the test piece 40 rotating at a high speed can be clearly captured as a still image.

  The pulse light emitting section 20 is configured by a light source capable of receiving a pulse signal Sp for pulse light emission and emitting light at a high response speed. As a light source for pulse light emission, for example, a light emitting diode, discharge light emission, or laser light is desirably used. Thereby, the responsiveness to the pulse signal Sp as the light emission command signal is good, and it is possible to obtain sufficient luminance 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 was necessary to temporarily stop the rotation of the test piece 40. When the rotation of the test piece 40 is stopped just before the test piece 40 breaks due to the growth of the crack, the load of the load applying section 32 is applied to the test piece 40, and the crack rapidly grows or reaches the fracture. Concerns. For this reason, it is generally very difficult to observe crack growth and the like 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 is performed by synchronizing the timing of the pulse emission by the pulse emission unit 20 and the imaging by the imaging unit 22 with the rotation of the test piece 40. The above-mentioned cracks and the like can be captured as a still image without stopping the rotation of the test piece 40 during the test. 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 the 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 test piece 40 continues to rotate. In order to detect the initial crack, the vicinity of the weakest part of the test piece 40 is imaged as a still image over the entire circumference while using the above-described method. Hereinafter, the configuration and method will be described in detail with reference to FIGS. 2A and 2B 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 at. As described above, the magnetic sensor 14 is driven by a servo motor (not shown in FIG. 1) (not shown in FIG. 1) to rotate in the opposite direction to the rotation direction of the gear unit 12, that is, in the clockwise direction on the paper surface of FIG. It is turned.

  In general, the test piece 40 used for the rotating bending fatigue test has a cylindrical shape. In addition, the weakest portion is generally located at 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, the imaging unit 22 and / or the optical magnification unit 24 (hereinafter, also referred to as “imaging unit 22 or the like”) illustrated in FIG. It is arranged in. In addition, the pulse light emitting section 20 is disposed at a predetermined position where the weakest part of the test piece 40 can be irradiated.

  With 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 on the paper surface, and is located at the phase of 1 shown in FIG. Further, the imaging means 22 and the like receive the pulse signal Sp from the magnetic sensor 14 and receive 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 shown as 40a is imaged.

  Next, as shown in FIG. 2B, the magnetic sensor 14 is rotated from the phase of 1 shown in FIG. 2B to the phase of 2, and has been rotated at least once with the rotation of the gear unit 12. The left end surface of the projection A on the paper surface is detected. The imaging means 22 and the like receive the pulse signal Sp output from the pulse emission control means (shown as 28 in FIG. 1) by this detection, and receive a phase different from the previously imaged phase, for example, FIG. Of the surface of the test piece 40 shown in FIG.

  By repeating the above-described procedure, the magnetic sensor 14 is rotated clockwise (in the direction indicated by the black arrow) on the paper of FIG. 2B, and the convex portions are formed in three phases and four phases shown in FIG. The output voltage value V for generating the pulse signal Sp by detecting the left end face of the paper surface of A is sequentially output to a pulse emission control means (shown as 28 in FIG. 1) not shown.

  Further, the imaging unit 22 and the like receive the pulse signal Sp output from the pulse emission control unit output, and change the imaging location of the test piece 40 in a counterclockwise direction (the direction of the white arrow) on the paper of FIG. ), The different phases of the test piece 40 are sequentially imaged.

  By repeating the above procedure, the weakest part of the test piece 40 is imaged over the entire circumference. The image data captured by the imaging unit 22 and the like is transmitted to the computer device 30 included in the rotating bending fatigue test device 80 described later in detail, and is recorded. In the above description, a method of once imaging the entire circumference of the weakest portion of the test piece 40 has been described, but this imaging is continuously performed at least until an initial crack is detected.

  Image data of a still image continuously captured by the imaging unit 22 or the like is recorded in the computer 30 and image analysis is sequentially performed by a method described later in detail. Thereby, detection of the initial fatigue crack generated in the test piece 40 can be achieved.

  The phase at which the initial fatigue crack has occurred in the test piece 40 is simultaneously detected by the image analysis by the computer 30 in the above-described process. Thereby, it is possible to shift to the fixed-point observation of the crack or the like while continuing the test without stopping the rotation of the test piece 40.

  More specifically, when the occurrence and the 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 the drive of the servomotor 16 and is cracked by the method described above. Is continuously imaged. Thereby, without stopping the rotation of the test piece 40, the observation is shifted from the entire circumference observation of the weakest part of the test piece 40 to the fixed point observation of the crack and the like, and the observation of the propagation of the crack is continuously performed. be able to.

  If necessary, the imaging unit 22 and the like, and the pulse light emitting unit 20 may be moved in the rotation axis direction of the test piece 40. This makes it possible to make the imaging position of the imaging unit 22 and the like and the irradiation position of the pulse light emitting unit 20 more appropriate, set the crack and the like at the center of the imaging range, and so on. Observation can be performed by simple still imaging.

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

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

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

  For this reason, in the rotary bending fatigue test apparatus according to one embodiment of the present invention, the observation axis of the imaging unit 22 and / or the optical magnification unit 24 shown in FIG. (Imaging direction) When a light source is disposed coaxially with S and pulsed light is irradiated, reflected light from only a part of the test piece 40 reaches the above-described imaging element provided in the imaging means 22.

  Therefore, FIGS. 4C and 4D are schematic diagrams illustrating test pieces imaged by irradiation from the light source, that is, the pulse light emitting unit 20 in the rotary bending fatigue test apparatus according to one embodiment of the present invention. As illustrated in FIG. 4D, only a part of the surface of the test piece 40 is imaged. For this reason, when the crack has grown to an extent exceeding 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 unit 22. Becomes

  As shown in FIG. 4A, the pulse light emitting unit 20 in the rotary bending fatigue test device 80 according to one embodiment of the present invention includes two pulse light emitting units 20, an imaging unit 22 and / or an optical enlarging unit 24. Are arranged at an angle W which is substantially the same as the outer circumferential direction of the test piece 40 with respect to the disposition direction S.

  In the present embodiment, as shown in FIGS. 4A and 4D, the light emitting diode 20a as a light source is turned around the test piece 40, as shown in the photographic view of the pulsed light emitting section 20 viewed from the direction of the arrow R shown in FIG. The pulse light emitting section 20 is arranged in four rows in the circumferential direction and three rows in the direction of the axis of rotation, and is disposed at a position inclined at substantially the same angle W in the rolling direction of the test piece 40. ing.

  As described above, as shown in FIG. 4 (c), the light from the pulsed light emitting section 20 is uniformly distributed to a range sufficient to observe the entire "crack" generated and propagated on the test piece 40 by the rotating bending fatigue test. In addition, it is possible to irradiate with a light amount sufficient for observation. As a result, the initiation, growth behavior, crack length, and the like of the crack on the surface of the test piece 40 are captured as a clear still image, and observation and measurement in real time can be achieved.

In this 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 that has a good response to the pulse signal Sp as the light emission command signal and can obtain a sufficient luminous intensity for imaging by light emission for an extremely short time. Laser light or the like can be used. Further, the types of light sources may be combined.

  Further, it is also possible to three-dimensionally observe a crack or the like from two still images such as a crack, etc., which are imaged at an interval by the method described above. The principle is based on so-called stereoscopic vision. For example, by using a parallel method, an intersection method, or the like, image processing is performed by a computer or the like, so that two stationary images of a crack location are spaced at a time interval. From the image, 2.5-dimensional data of a three-dimensional image of a crack or the like 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 >>
In addition, the rotating bending fatigue test apparatus 80 of the present invention continuously captures, in real time, the occurrence and propagation of cracks in the test piece 40, and automatically predicts the break time of the test piece 40. As a result, 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 rotary bending fatigue test device 80 includes a computer device 30 that records a still image captured by the imaging unit 22 and that can analyze the still image. With the above-described configuration, data of a still image captured by the imaging unit 22 is stored and recorded in the computer 30.

  By comparing and analyzing the accumulated and recorded still images of the crack and the like with time, the occurrence of the crack and the size of the crack, specifically, the length and / or width evolve. The speed can be measured in real time. The image analysis means can be appropriately implemented using the configuration disclosed in the prior art document (Patent Document: Japanese Patent Application Laid-Open No. 5-256632), and the detailed description is omitted. .

  The configuration of the above-mentioned prior art document will be briefly described. In a metal member damage inspection device that automatically determines the remaining life of a metal member, a metal member (corresponding to the test piece 40 of the present invention) is set in the inspection device, The image of the optical microscope is captured by a video camera and processed by an image processing device. A computer (corresponding to the computer 30 of the present invention) determines whether or not a crack has occurred as damage to the shaft based on the image-processed data. When the computer recognizes the crack, it determines the shape of the crack by connecting and combining the crack with other cracks, analyzes the determined crack distribution, and analyzes the crack. This is to find the maximum length.

  It is generally known that a crack generated in a test piece in a fatigue test of a material accelerates and accelerates as the fracture of the test piece approaches. The computer 30 included in the rotary bending fatigue test apparatus 80 of the present invention previously stores in advance data on the length of a crack, which is an index of the time of fracture, for at least the material of the test piece 40 to be subjected to the rotary bending fatigue test. , "Failure time prediction data").

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

  The rotary bending fatigue test apparatus 80 of the present invention shown in FIG. 1 is based on the rotational speed of the test piece 40, that is, the rotation driving means 10 for rotating the test piece 40, based on the fracture time of the test piece 40 predicted above. From a rotation speed of about 20,000 to 30,000 rotations / minute, a load determined by a predetermined rotation speed, for example, the Japanese Industrial Standards (JIS) standard number "JIS Z 2274" and the name "Rotating Bending Fatigue Test Method for Metallic Materials" Is reduced to a rotation speed corresponding to “1000 to 5000 times per minute” which is a repetition speed of

As described above, the test piece 40 is rotated at a high speed of about 20,000 to 30,000 revolutions / minute with a bending load applied to the test piece 40 in order to accelerate the test, as described above. For this reason, the temperature of the test piece 40 rises due to friction between molecules constituting the test piece 40 and the like. In particular, as the crack propagates and the break time approaches, the speed at which the test piece 40 propagates the crack increases, and the cross-sectional area of the test piece 40 near the crack decreases. For this reason, the load (stress) concentrates on a portion of the test piece 40 where the crack does not reach near the crack , and the temperature rise gradient becomes steeper.

  When the temperature of the vicinity of a crack of the test piece 40 becomes high, when the test piece is made of metal, a change in hardness of the test piece 40 is particularly large near a “crack”, and so-called work hardening or work softening occurs. I do. For this reason, it is difficult to obtain an accurate test result.

  In the rotating bending fatigue test apparatus 80 of the present invention, the rotation speed of the test piece 40, that is, the rotation speed of the rotation driving unit 10 is changed at a point in time before the fracture time of the test piece 40 predicted above by a predetermined time. For example, it is reduced to 1000 to 5000 revolutions / minute. Thereby, the temperature near the crack of the test piece 40 is reduced to the temperature of the test piece in the normal rotating bending fatigue test method. As a result, at least a test result equivalent to a normal test method can be obtained.

  In addition, as a method of determining the predetermined time before the rupture time of the test piece 40 for setting the time for reducing the rotation speed of the rotation drive unit 10 described above, for example, based on a previous test result, It is possible, but not limited to.

  Further, it is preferable that the rotating bending fatigue test apparatus 80 of the present invention includes a means for detecting the occurrence of a crack 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 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) or the like. I do.

When the current value changes, for example, when a minute scratch, that is, an initial “crack” occurs on the surface of the test piece 40, the electric 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, the more the current flows on the metal surface. Due to the increase in the electric resistance, the amount of current detected by the ammeter decreases . When the decrease in the amount of current is detected, it is possible to detect the occurrence of a crack.

<< Structure of tensile / compression fatigue test equipment >>
Next, among the fatigue test devices of the present invention, those used for tensile / compression fatigue tests will be described with reference to FIGS. 7 and 8 (hereinafter, also simply referred to as “tensile / compression fatigue tests”). Even in this tensile / compression fatigue test, the growth of "cracks" can be measured without stopping the tension / compression of the test piece, and the time required for the tension / compression fatigue test can be significantly reduced compared to the normal test method. . In addition, the occurrence of cracks on the surface of the test piece used in the tensile / compression fatigue test, the growth behavior and the length of the "crack" were determined at least after the "crack" occurred in the test piece. It is possible to perform real-time observation and the like until fracture occurs, and at the same time, to obtain a test result equivalent to or more accurate than a normal tensile / compression fatigue test.

  In the tensile / compression fatigue test, a tensile load (load) is applied to a predetermined test piece (metal material), a specific amount of tensile deformation is applied, then the load (load) is once removed, and the compressive load (load) is left as it is. ) Is applied for compressive deformation, or after applying compressive deformation, tensile deformation is applied. FIG. 7 shows a schematic diagram (schematic diagram) of a main part of an embodiment of the present tensile / compression fatigue test 100. In the 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 vertically oscillating is used.

  The fatigue crack 103 generated and propagated in the test piece 101 is captured as a clear still image under a favorable light emitting state. In addition, the rupture time of the test piece 103 is estimated based on the data of the captured still image, and at a time point before the test piece 103 breaks, the amplitude speed of the test piece is reduced to a predetermined speed. I have.

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

  The load control device 108 transmits a synchronization reference signal (a synchronization signal in the drawing) to the synchronization control device 109 in synchronization with a vibration signal to the vibration exciter 102. Upon receiving the synchronization signal from the load control device 108, the synchronization control device 109 sends a synchronization signal (a light source synchronization signal in the figure) to the power amplifier 110 and a control signal (see FIG. (The image acquisition control signal).

  FIG. 8 is a block diagram showing an outline 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 a pulse shaping circuit 109d, and is frequency-divided to a desired frequency by a frequency dividing circuit 109b. The frequency division is a technique used when the light source 104 or an image collecting device 107 described later cannot be synchronized as it is, for example, when the vibration applied 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, the irradiation timing of the light source (irradiation source) 110 and a light source synchronization signal whose pulse peak is delayed in accordance with the timing. At the same time, the delay control circuit 109c transmits an image collection control signal linked to the light source synchronization signal to the image collection device 107.

  Referring back to FIG. The power amplifier 110 that has received the light source synchronization signal from the synchronization control device 109 supplies or shuts off power to the light source 104. Thus, the light source 104 irradiates a pulse light from the light source 104 to a crack on the surface of the test piece 101 or a portion where the crack propagates (hereinafter, also simply referred to as a “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 an image collecting device 107 having a photoelectric conversion element (imaging element) causes the test piece 101 to develop a crack or a crack. The image is recorded as electronic data. In addition, as an imaging element, for example, a CMOS image sensor, a CCD image sensor, or the like is used. Further, the imaging unit 105 includes an optical magnifying unit (a lens or the like) 106 that combines a telescope and a microscope to magnify and image the test piece 101. Thereby, the periphery of the crack 103 of the test piece 101 is enlarged, and the image collecting device 107 can selectively enlarge the crack or the like for imaging.

  As described above, since the image collection device 107 receives the image collection signal in synchronization with the light source synchronization signal to the power amplifier 110 and controls the imaging timing, the image collection can be performed 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 (filtering operation), difference processing, pattern extraction, and arithmetic processing on the image data. And output as data such as raw data. Then, the output data is received and displayed on a display device 113 such as a measurement result display.

  Further, the image processing device 112 transmits a positioning signal for adjusting the position of the imaging unit 105 to the positioning device 111. The position of the imaging means 105 in the XYZ directions is adjusted by the positioning signal. For example, when the proper imaging position of the crack is shifted in the image processing by the image processing device 112, the position of the imaging unit 105 is moved (tracked) so that the tip of the crack is located at the center of the image. It is preferable that the starting crack 103a be attached to the test piece 101 as the initial position of the crack tip (tracking origin position). The positioning device 111 includes a piezoelectric element such as a piezo element and an actuator, and converts the positioning signal into a force to drive the imaging unit 105.

  As described above, in the tensile / compression fatigue testing apparatus 100, the synchronous control device 109 applies the axial load to the image collecting device 107 that collects the crack image of the test piece 101 photographed by the imaging means 105 and the test piece 101. By synchronizing with the load control device 108 of the vibrator 102 to be performed, the image of the dynamic test piece 101 during the fatigue test can be acquired and measured as a static image. Therefore, the crack generation and growth behavior of the test piece 101 can be observed and measured in real time. Further, the position of the tip of the crack is monitored by the image processing device 112 and the positioning device 111, and the position of the imaging means 105 is adjusted, so that the crack propagation can be tracked and automatically measured.

As described above, the present tensile / compression fatigue test apparatus can also be applied to an ultrasonic tensile / compression fatigue test that has recently been developed. When applied to the ultrasonic fatigue test, a piezo element is used for the vibrator 102, and resonance (around 20,000 times / s) is generated by longitudinal wave vibration of, for example, 20 kHz ± 500 Hz. A stress σ (150 to 700 MPa) is repeatedly applied to the position of the starting crack 103a. Note that the above-described frequency division is performed by, for example, dividing the frequency by 1/100 by the frequency dividing circuit 109b and shaping the frequency around 200 Hz. Further, although not shown, the test piece 101 may be cooled by blowing air to suppress a decrease in strength due to a rise in temperature .

  The embodiment of the fatigue test apparatus according to the present invention has been described above. However, the present invention is not limited to this, and may be modified within the spirit and teaching described in the claims and the specification. It will be understood by those skilled in the art that modifications and improvements of the present invention 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 Imaging means 24 Optical enlargement means 26 Interval detection means 28 Pulse emission control means 30 Computer 32 Load application part 32a Adapter 32b Suspension part 32c Weight part 40 Test piece 40a Crack initiation part (initial crack)
80 Rotary bending fatigue testing device 100 Tensile / compression fatigue testing device 101 Test piece 102 Shaking machine (shaking device)
103 crack 103a origin crack 104 light source (irradiation device)
105 imaging means 106 optical magnification means (lens)
107 Image collecting device 108 Load control device 109 Synchronous control device 109a Voltage conversion circuit 109b Frequency dividing circuit 109c Delay control circuit 109d Pulse generating circuit 111 Positioning device 112 Image processing device 113 Display device A to I Convex part on outer periphery of gear portion V Magnetic sensor (Magnetoresistance effect element) Output voltage value Sp Pulse signal for synchronizing pulse emission and imaging

Claims (5)

A fatigue test apparatus for measuring a rotating bending fatigue by gripping an end portion of the test piece with a load applied thereto and rotating the shaft,
Imaging means disposed at a position where the shape change can be observed based on the angle information in the rotation direction and the axial position information of the initial shape change detected on the surface of the test piece,
A light source that can irradiate the test piece for a short time,
While the test piece is rotating, the light source emits light for a short time to irradiate the test piece, thereby continuously observing a still image of the shape change of the surface of the test piece by the imaging means, and tracking and comparing the change over time. To predict the time of rupture of the test piece ,
A fatigue test apparatus characterized in that, when a fracture time of a test piece is predicted, a rotation speed of the test piece is reduced . A fatigue test apparatus for measuring a rotating bending fatigue by gripping an end portion of the test piece with a load applied thereto and rotating the shaft,
Imaging means disposed at a position where the shape change can be observed based on the angle information in the rotation direction and the axial position information of the initial shape change detected on the surface of the test piece,
A light source that can irradiate the test piece for a short time,
While the test piece is rotating, the light source emits light for a short time to irradiate the test piece, thereby continuously observing a still image of the shape change of the surface of the test piece by the imaging means, and tracking and comparing the change over time. To predict the time of rupture of the test piece ,
When the test piece reaches the phase of rotation of the test piece, which can image the shape change on the surface of the test piece by the imaging means, synchronizes the light emission of the light source with the imaging of the imaging means,
The light source emits light at a time interval synchronized with the rotation speed of the test piece in a minute time, and the image pickup device captures one point on the test piece as a plurality of images obtained by subdividing one point in the circumferential direction, A fatigue test apparatus characterized in that a change in the shape of the surface of the test piece is stereoscopically viewed by comparing the images . A fatigue test apparatus for measuring a rotating bending fatigue by gripping an end portion of the test piece with a load applied thereto and rotating the shaft,
Imaging means disposed at a position where the shape change can be observed based on the angle information in the rotation direction and the axial position information of the initial shape change detected on the surface of the test piece,
A light source that can irradiate the test piece for a short time,
While the test piece is rotating, the light source emits light for a short time to irradiate the test piece, thereby continuously observing a still image of the shape change of the surface of the test piece by the imaging means, and tracking and comparing the change over time. To predict the time of rupture of the test piece,
The light source is an LED stroboscope,
The rotation drive source of the test piece is a servomotor,
A gear cooperating with the rotation of the servomotor;
A magnetic sensor disposed around the gear and having a magnetoresistive effect element,
A change in the resistance value of the magnetoresistive element of the magnetic sensor is converted into a voltage change based on the relationship between the angular position of the magnetic sensor and the position of the teeth forming the gear, and the change is converted into a pulse signal. To generate an input signal for LED emission,
The light source emits light at a time interval synchronized with the rotation speed of the test piece in a minute time, and the imaging device captures a point on the test piece as a plurality of images obtained by subdividing one point in a circumferential direction, A fatigue test apparatus characterized in that a change in the shape 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, and the change in the magnitude of the current flowing through the surface is measured.When the current decreases, it is estimated that the initial shape change of the surface of the test piece has occurred. The fatigue test apparatus according to claim 1, wherein: The fatigue test apparatus according to any one of claims 1 to 4 , wherein an optical axis of the light source and a light receiving device of the imaging unit are arranged at the same angle with respect to a test piece.