JP2006308342A - Device for measuring bolt axial force - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily measure an accurate axial force generated in a bolt. <P>SOLUTION: A search probe 10 transmits an ultrasonic wave to the bolt 14 and receives a reflected wave from the bolt 14. A measuring point detection part 32 detects a measuring point from inside a waveform of the reflected wave. A propagation time measuring part 34 measures the propagation time of the ultrasonic wave in the bolt 14 based on a receiving timing of the detected measuring point. A correction coefficient calculation part 36 calculates the correction coefficient of the propagation time determined by reflecting temperature dependency of the ultrasonic propagation speed in the bolt 14 based on the temperature of the bolt at the measuring time. A propagation time correction part 38 calculates the propagation time after temperature correction based on the measured propagation time and the calculated correction coefficient. Thus, the accurate propagation time subjected to the temperature correction can be measured, and resultantly the axial force of the bolt can be measured more accurately. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bolt axial force measuring device, and more particularly to a device that measures the axial force of a bolt by transmitting and receiving ultrasonic waves.

  As an apparatus for measuring the axial force of a bolt using ultrasonic waves, an ultrasonic bolt axial force measuring apparatus is known (for example, see Patent Document 1). This apparatus is configured to transmit an ultrasonic wave from an ultrasonic probe into a bolt, propagate the ultrasonic wave in the bolt, and receive a reflected wave with the ultrasonic probe. And the time when the ultrasonic wave propagated inside the bolt is measured based on the timing when the reflected wave is acquired.

  Compared to before tightening, after tightening, the bolt is stretched by the tightening axial force, so the propagation path of the ultrasonic wave becomes longer. In addition, if the bolt is tightened and an axial force is applied to the bolt to generate a tensile stress, the ultrasonic wave propagation speed also decreases. That is, the propagation time of the ultrasonic wave propagating in the bolt before and after tightening is different. For this reason, the axial force of a bolt can be measured by using an ultrasonic bolt axial force measuring device and knowing the difference in propagation time before and after tightening.

JP 2001-174343 A JP 2001-264197 A JP-A-4-166732

  In order to accurately measure the axial force of the bolt from the propagation time of the ultrasonic wave, there are several problems to be overcome. For example, the elongation of the bolt and the ultrasonic wave propagation speed when the bolt is tightened also depend on the temperature of the bolt, and the propagation time of the ultrasonic wave propagating in the bolt is also affected by the temperature. Therefore, in order to obtain the axial force from the propagation time of ultrasonic waves, it is necessary to accurately measure the propagation time in consideration of changes due to temperature. Incidentally, Patent Document 3 discloses a technique for incorporating the influence of temperature into correction by performing ultrasonic axial force measurement with a spacer having a known temperature coefficient interposed.

  Further, the reflected wave after propagating through the bolt is received as a pulse-like waveform spreading in the time axis direction. For this reason, a deviation in the time axis direction, that is, a measurement error in propagation time may occur depending on how the measurement point is detected in the waveform of the received reflected wave. Incidentally, in the above-mentioned Patent Document 2, the waveform in the axial force measurement mode and the waveform in the initial value setting mode are displayed in an overlapped manner, so that the measurement point before tightening (measurement peak) and the measurement point after tightening (measurement peak) ) Describes a technique for adjusting so that the waveform portions are the same. However, it is not easy to accurately determine the correspondence between waveforms before and after tightening.

  The present invention has been made in such a background, and an object thereof is to easily measure an accurate axial force generated in a bolt.

  In order to achieve the above object, a bolt axial force measuring device according to a preferred aspect of the present invention is a bolt axial force measuring device that measures the axial force of a bolt based on the propagation time of an ultrasonic wave propagating in the bolt. An ultrasonic transmission / reception unit for transmitting an ultrasonic wave to the bolt and receiving a reflected wave from the bolt, a measurement point detection unit for detecting a measurement point from the waveform of the reflected wave, and a reflected wave obtained a plurality of times Based on the measurement points detected from within each waveform, a propagation time actual measurement unit that actually measures the propagation time of ultrasonic waves in the bolt from the time difference between different measurement points, and the actual measurement bolt measured by the temperature measurement means A correction coefficient calculation unit for calculating a correction coefficient of the propagation time reflecting the temperature dependence of the ultrasonic propagation velocity in the bolt, and the measured propagation time and the calculated correction coefficient. Based on temperature Having a propagation time correction unit that calculates a propagation time after correction, characterized in that.

  In the above configuration, since the propagation time is calculated in consideration of the temperature dependence of the ultrasonic propagation speed, it is possible to easily measure an accurate axial force generated in the bolt.

  Preferably, the correction coefficient calculation unit is based on at least the temperature coefficient of the ultrasonic propagation velocity, the reference temperature of the bolt in a state where no axial force is acting, and the measured temperature of the bolt when the propagation time is actually measured. And calculating the correction coefficient. Preferably, the temperature coefficient of the ultrasonic wave propagation speed is set for each bolt to be measured.

  In order to achieve the above object, a bolt axial force measuring device according to a preferred aspect of the present invention is a bolt axial force measuring device that measures the axial force of a bolt based on the propagation time of ultrasonic waves propagating in the bolt. An ultrasonic transmission / reception unit that transmits an ultrasonic wave to the bolt and receives a reflected wave from the bolt, a measurement point detection unit that detects a measurement point from the waveform of the reflected wave, and a reflected wave obtained a plurality of times A propagation time actual measurement unit that actually measures the propagation time of the ultrasonic wave in the bolt from the time difference between the different measurement points based on the measurement points detected from each of the waveforms, the measurement point detection unit, A measurement point designated based on measurement point designation information stored in advance is detected.

  In the above configuration, the measurement point is designated based on the measurement point designation information stored in advance, and the measurement point is accurately detected. For this reason, the propagation time can be measured more accurately, and as a result, the axial force of the bolt can be measured more accurately.

  Preferably, the measurement point is a point corresponding to a representative point in the waveform of the reflected wave in a state where no axial force is acting. Preferably, the measurement point designation information is display information indicating a position of a point corresponding to the representative point in a waveform of a reflected wave in a state where an axial force is acting, and the display information includes the axial force. It is obtained by tracking the movement of the representative point from a state where it is not acting to a state where an axial force is acting.

  In order to achieve the above object, a bolt axial force measuring method according to a preferred aspect of the present invention is a bolt axial force measuring method for measuring the axial force of a bolt based on the propagation time of an ultrasonic wave propagating in the bolt. , A measurement point detecting step for detecting a measurement point from the waveform of the reflected wave obtained by transmitting and receiving an ultrasonic wave to the bolt, and a measurement detected from each waveform of the reflected wave obtained a plurality of times Based on the point, the propagation time measurement step for actually measuring the propagation time of the ultrasonic wave in the bolt from the time difference between the different measurement points, and the temperature dependence of the ultrasonic wave propagation speed in the bolt based on the temperature of the bolt at the time of the measurement A correction coefficient calculating step for calculating a correction coefficient for the propagation time reflecting the characteristics, and calculating the propagation time after temperature correction based on the actually measured propagation time and the calculated correction coefficient. Having a correction step between 播時, characterized in that.

  In order to achieve the above object, a bolt axial force measuring method according to a preferred aspect of the present invention is a bolt axial force measuring method for measuring the axial force of a bolt based on the propagation time of an ultrasonic wave propagating in the bolt. , A measurement point detecting step for detecting a measurement point from the waveform of the reflected wave obtained by transmitting and receiving an ultrasonic wave to the bolt, and a measurement detected from each waveform of the reflected wave obtained a plurality of times A propagation time actual measurement step for actually measuring the propagation time of the ultrasonic wave in the bolt from the time difference between the different measurement points based on the points, and based on the measurement point designation information stored in advance in the measurement point detection step. In this case, the measurement point specified is detected.

  According to the present invention, it is possible to easily measure an accurate axial force generated in a bolt.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a diagram for explaining a preferred embodiment of the present invention, and FIG. 1 is a functional configuration diagram of a bolt axial force measuring device according to the present invention.

  The bolt axial force measuring device of the present embodiment is configured to transmit an ultrasonic wave into the bolt 14 and propagate the ultrasonic wave within the bolt 14 to receive a reflected wave. Based on the timing at which the reflected wave is acquired, the time during which the ultrasonic wave propagates through the bolt 14 is measured.

  The probe 10 is an ultrasonic probe that transmits and receives ultrasonic waves. The probe 10 transmits an ultrasonic wave to the bolt 14 via the ultrasonic propagation medium 12 and receives a reflected wave from the bolt 14 via the ultrasonic propagation medium 12.

  The probe 10 is connected to an ultrasonic pulsar receiver 20 and transmits ultrasonic waves based on a transmission signal supplied from a transmission / reception unit 22 in the ultrasonic pulsar receiver 20. Further, the probe 10 outputs a reception signal corresponding to the received reflected wave to the transmission / reception unit 22. The received signal is converted from the transmission / reception unit 22 into a digital signal by the analog / digital conversion unit (A / D conversion unit) 24 and transmitted to the axial force measurement unit 30.

  The axial force measurement unit 30 measures the time that the ultrasonic wave has propagated through the bolt 14 based on the reception signal transmitted from the ultrasonic pulser receiver 20. Then, the axial force of the bolt 14 is measured from the measured propagation time. Therefore, the principle of bolt axial force measurement in the present embodiment will be described before describing the function of each part in the axial force measuring unit 30.

  FIG. 2 is a diagram for explaining the principle of measuring the propagation time of ultrasonic waves in a bolt. FIG. 2A shows an ultrasonic wave (transmission waveform) transmitted into the bolt and a reflected wave (reflection waveform) received from the bolt with the horizontal axis as a time axis. FIG. 2B schematically shows an ultrasonic wave propagating through the bolt 14.

  When an impulse-like ultrasonic wave, that is, a transmission waveform shown in FIG. 2A is transmitted from the probe 10 to the bolt 14 via the ultrasonic propagation medium 12, the transmitted ultrasonic wave is transmitted into the bolt 14. Is reflected at the front end side of the bolt 14 (the end opposite to the end on the head side where the probe 10 is disposed) and returns to the head side of the bolt 14. At this time, the reflected wave received by the probe 10 through the ultrasonic wave propagation medium 12 is the reflected waveform (one reciprocation) in FIG. Further, the propagation path at this time is the propagation path (one round trip) in FIG.

  The ultrasonic wave that reciprocates once in the bolt 14 and returns to the head side is further reflected on the head side, returns to the tip side of the bolt 14, and then returns to the head side again. At this time, the reflected wave received by the probe 10 through the ultrasonic wave propagation medium 12 is the reflected waveform (two reciprocations) in FIG. Further, the propagation path at this time is the propagation path (two reciprocations) in FIG.

  In this embodiment, as shown in FIG. 2A, the time difference between the reflected waveform (2 reciprocations) and the reflected waveform (1 reciprocation) is measured as the propagation time of the ultrasonic wave in the bolt 14. This is due to the following reason.

  When the propagation time is measured as a time difference between the transmission waveform and the reflected waveform (one round trip), the thickness of the ultrasonic propagation medium 12 is included in the propagation path for one round trip (in FIG. 2B). Propagation path (1 round trip)). This change in the thickness of the ultrasonic propagation medium 12 may cause a measurement error. For this reason, in this embodiment, the time difference between the reflected waveform (2 reciprocations) and the reflected waveform (1 reciprocation) is taken. As a result, only the propagation time of the propagation path (bolt alone) in FIG. 2B is measured.

In this embodiment, the difference in propagation time before and after the bolt 14 is tightened is measured. The relationship of the following formula is established among the propagation time of ultrasonic waves (ultrasonic propagation time) in the bolt 14, the propagation path of ultrasonic waves (ultrasonic propagation path length), and the ultrasonic propagation velocity.

  After tightening, the bolt 14 is stretched by the tightening axial force after tightening, so that the ultrasonic propagation path becomes longer. Further, when an axial force is applied to the bolt 14 and a tensile stress is generated, the ultrasonic wave propagation speed is also reduced. That is, the propagation time of the ultrasonic wave propagating through the bolt 14 changes before and after tightening. For this reason, if the relationship between the propagation time difference before and after tightening the bolt 14 and the axial force of the bolt 14 is known in advance, the axial force can be derived from the propagation time difference.

  FIG. 3 is a diagram for explaining the principle of deriving the axial force from the propagation time difference. FIG. 3A shows a calibration curve for deriving the axial force from the propagation time difference. In FIG. 3A, the horizontal axis represents the propagation time difference (or propagation time), and the vertical axis represents the axial force.

  When obtaining the calibration curve, a measuring instrument that can directly measure the axial force of the bolt, such as a load cell, is used. Then, the ultrasonic wave propagation time in a state where no axial force is applied to the bolt and the ultrasonic wave propagation time in a state where a predetermined axial force measured by a load cell or the like is applied are measured. For example, a total of n + 1 measurements of the propagation time when the axial force is 0 and the measurement of the propagation time at n known axial force values are performed. Then, the difference between the propagation time when the axial force is 0 and the propagation time at a known axial force value is taken as the propagation time difference on the horizontal axis, and the axial force value at that time is taken on the vertical axis. N + 1 measurement result points are obtained. A calibration curve is formed as a curve connecting these n + 1 measurement result points.

In addition, it is good also as a calibration curve which made propagation time and axial force correspond by making propagation time in the case of axial force 0 into the origin of the horizontal axis of a calibration curve. For example, in FIG. 3A, the propagation time difference ΔT ₁ is the difference between the propagation time T ₀ when the axial force is ₀ and the propagation time T _1,1 when the axial force is acting. The axial force at the propagation time difference ΔT ₁ is F ₁ . On the other hand, the propagation time T _1,1 and the axial force F ₁ can be directly associated by setting the propagation time when the axial force is 0 as the origin of the horizontal axis of the calibration curve.

And by using the bolt axial force measuring device of this embodiment, axial force can be calculated | required based on the propagation time difference from the calibration curve shown in FIG. That is, as shown in FIG. 3B, by applying the propagation time difference ΔT (= T ₁ −T ₀ ) measured by the bolt axial force measuring device to the calibration curve obtained in advance, the propagation time difference ΔT is calculated. The axial force F corresponding to the propagation time difference can be obtained. Of course, if the horizontal axis of the calibration curve is the propagation time, the axial force can also be obtained from the propagation time T ₁ .

  In the present embodiment, the bolt axial force is measured based on the principle described with reference to FIGS.

  Returning to FIG. 1, the function of each part in the axial force measurement unit 30 will be described. The measurement point detector 32 detects a measurement point from the reflected wave waveform acquired by the ultrasonic pulsar receiver 20. That is, since the reflected wave is received as a pulse-like waveform spreading in the time axis direction (see FIG. 2A), the measurement point is detected from the reflected waveform. For example, a peak point (predetermined extreme point) in the reflected waveform is detected as a measurement point. In the present embodiment, a measurement point designated based on measurement point designation information stored in advance is detected. The method for detecting the measurement point will be described in detail later with reference to FIGS.

  The propagation time actual measurement unit 34 actually measures the ultrasonic propagation time in the bolt 14 based on the reception timing of the measurement point detected by the measurement point detection unit 32. That is, as described with reference to FIG. 2 (A), these two points are obtained from the reception timing of the measurement point detected from the reflection waveform (one reciprocation) and the measurement point detected from the reflection waveform (two reciprocations). Measure the propagation time, which is the time between measurement points.

  In the present embodiment, the axial force of the bolt 14 is measured from the propagation time of the ultrasonic wave propagating through the bolt 14. Therefore, in order to accurately measure the axial force of the bolt 14, it is necessary to accurately measure the propagation time. However, this propagation time is affected by the temperature of the bolt 14. That is, since the elongation of the bolt 14 and the ultrasonic propagation speed when the bolt 14 is tightened also depend on the temperature of the bolt 14, the propagation time of the ultrasonic wave propagating through the bolt 14 is affected by the temperature. End up. Therefore, in this embodiment, the propagation time is corrected to reflect the temperature dependence.

  The correction coefficient calculator 36 calculates a propagation time correction coefficient reflecting the temperature dependence. As shown in Equation 1, the propagation time (ultrasonic propagation time) is determined by the ultrasonic propagation path (ultrasonic propagation path length) and the ultrasonic propagation velocity. Therefore, when considering the temperature dependence of the propagation time, both the temperature dependence of the ultrasonic propagation path length, that is, the temperature dependence of the length of the bolt 14 and the temperature dependence of the ultrasonic propagation speed are considered. There is a need.

FIG. 4 is a diagram for explaining the temperature dependence of the ultrasonic propagation velocity and the temperature dependence of the bolt length. FIG. 4A is a graph showing the temperature dependence of the ultrasonic propagation speed, where the horizontal axis indicates the bolt temperature and the vertical axis indicates the ultrasonic propagation speed within the bolt. As shown in FIG. 4 (A), when the temperature in the bolt is high, the ultrasonic wave propagation speed decreases. The temperature coefficient α _t of sound speed indicates the degree of decrease in propagation velocity with respect to temperature rise.

On the other hand, FIG. 4B is a graph showing the temperature dependence of the bolt length, in which the horizontal axis indicates the temperature of the bolt and the vertical axis indicates the bolt length. As shown in FIG. 4B, when the temperature in the bolt is high, the bolt becomes long. The linear expansion coefficient α _L indicates the degree of increase in the bolt length with respect to the temperature rise.

In consideration of the temperature dependence of the ultrasonic propagation velocity and the temperature dependence of the bolt length, the following equation is used between the propagation time at the reference temperature t ₀ and the propagation time at the measurement temperature t _1. The relationship of the propagation time ratio shown in FIG.

Returning to FIG. 1, the correction coefficient calculation unit 36 calculates the propagation time ratio expressed by Equation 2 as the correction coefficient β. Incidentally, in Equation 2, the linear expansion coefficient α _L of the bolt, the temperature coefficient α _{t of} the sound speed, the stress coefficient α _{V of the} sound speed, the equivalent cross-sectional area A _e of the bolt, and the ultrasonic wave propagation velocity v ₀ at the reference temperature are: This is an element that depends on the bolt to be measured, and can be obtained by measurement or theoretical calculation before the axial force measurement. Further, the reference temperature t ₀ and the measurement temperature t ₁ are measured by the temperature sensor 52 at the time of measuring the axial force, and transmitted to the correction coefficient calculation unit 36 via the temperature measurement unit 50. Therefore, the propagation time ratio (correction coefficient β) can be obtained from the bolt axial force F by Equation 2.

  For example, a value obtained from a calibration curve based on the propagation time actually measured in the propagation time actual measurement unit 34 is used as the bolt axial force (the axial force F to be substituted into Equation 2) when obtaining the correction coefficient β. That is, the axial force is derived from the difference between the propagation time before the axial force action measured by the propagation time measuring unit 34 and the propagation time at the axial force action using the calibration curve according to the principle described in FIG. The correction coefficient β is obtained using this axial force (value before temperature correction).

  In this embodiment, as will be described later, the axial force after temperature correction is accurately derived using the propagation time corrected by the correction coefficient β. For this reason, the axial force F to be substituted into Equation 2 may be slightly changed, and the sequential calculation may be performed so that the axial force F to be substituted into Equation 2 and the finally obtained axial force after temperature correction coincide with each other.

By the way, for the elements that depend on bolts in Equation 2, the values obtained for each bolt are stored in the storage unit 44 and the like, and the user can select a desired numerical value according to the measured bolts. May be. For example, numerical values of elements (α _L , α _t , α _V, etc.) corresponding to each of the plurality of bolts are stored in the storage unit 44, and these numerical values are displayed on the display unit 42 to be selected by the user. Also good.

  The propagation time correction unit 38 calculates the propagation time after temperature correction based on the propagation time actually measured by the propagation time actual measurement unit 34 and the correction coefficient β calculated by the correction coefficient calculation unit 36.

In order to measure the axial force of the bolt 14, first, the ultrasonic propagation time T ₀ of the bolt 14 is measured in the propagation time measuring unit 34 in a state where the axial force is not acting, and the bolt temperature t ₀ at that time is the temperature. It is measured by the measurement unit 50. Thereafter, the bolt 14 is tightened to the measurement state and an axial force is applied. Then, the ultrasonic wave propagation time T ₁ of the bolt 14 is actually measured in the propagation time actual measurement unit 34 while the axial force is acting, and the bolt temperature t ₁ at that time is measured in the temperature measurement unit 50. When there is a temperature difference between the temperature t ₀ is a reference temperature and the temperature t ₁ is the measurement when the temperature is the propagation time ratio based on the number 2 in the correction coefficient calculation unit 36 (correction coefficient beta) is Calculated.

The propagation time correcting unit 38 is based on the ultrasonic propagation time T ₁ measured by the propagation time measuring unit 34 and the correction coefficient β calculated by the correction coefficient calculating unit 36, and the ultrasonic propagation time βT after temperature correction. ₁ is calculated. That is, the change in the propagation time due to the temperature change is removed by multiplying the correction coefficient β. Then, the propagation time correction unit 38 calculates ΔT = βT ₁ −T ₀ as the ultrasonic propagation time difference after temperature correction.

The axial force calculation unit 40 applies the ultrasonic propagation time difference (ΔT = βT ₁ −T ₀ ) after temperature correction calculated by the propagation time correction unit 38 to the calibration curve, that is, as illustrated in FIG. The axial force is derived from the principle. The derived axial force is displayed on the display unit 42, for example. Alternatively, the derived axial force may be stored in the storage unit 44.

  Thus, in this embodiment, since the axial force is derived using the ultrasonic propagation time difference after temperature correction, the accuracy of axial force measurement is improved.

  Furthermore, in this embodiment, when the measurement point is detected from the waveform of the reflected wave in the measurement point detection unit 32, the measurement point designated based on the measurement point designation information stored in advance is detected. The detection accuracy is improved.

  As described with reference to FIG. 2A, since the reflected wave obtained from the bolt 14 is received as a pulse-like waveform spreading in the time axis direction, the propagation time is measured from the reflected waveform. It is necessary to detect a measurement point for this purpose. Further, in order to measure the axial force of the bolt 14, it is necessary to compare the propagation time in a state where the axial force is not applied and the propagation time in a state where the axial force is applied. Therefore, the measurement point (representative point) in the reflected waveform in a state where axial force is not applied and the measurement point corresponding to the representative point in the reflected waveform in a state where axial force is applied are accurately determined. It needs to be detected. However, since the reflected waveform in the state where the axial force is acting changes according to the axial force, it is not easy to detect an accurate measurement point.

FIG. 5 is a diagram for explaining how the reflected waveform changes according to the axial force. FIGS. 5A to 5D show the axial force from 0 to F ₃ , respectively. The reflected waveform is shown. Each reflected waveform corresponds to the waveform shown in FIG. That is, each of the reflected waveforms in FIGS. 5A to 5D shows a transmission waveform, a reflected waveform (one round trip), and a reflected waveform (two round trips) in order from the left. The reflected waveform when the axial force is F ₃ is also shown in (d ′).

The propagation time at the axial force 0 is the period T ₀ in (a). This period T ₀ is obtained by using representative points (peak points: predetermined extreme points) of the reflected waveform (one round trip) and the reflected waveform (two round trips) as measurement points.

  Then, when measuring the axial force, if the reflected waveform (d ′) is obtained in the state where the axial force is applied, it is necessary to obtain the propagation time from the waveform (d ′). However, when the waveform of (a) and the waveform of (d ′) are compared, as a result of the reflection waveform changing due to the axial force, the point corresponding to the representative point S in the waveform of (a) is the waveform of (d ′). It is difficult to determine whether the point is A point or B point. That is, it is difficult to detect the measurement points corresponding to each other only from the comparison of the two waveforms of the state where the axial force is not applied and the measurement state where the axial force is applied.

  Therefore, in the present embodiment, measurement point designation information for designating a measurement point in a state where an axial force is acting is stored in the storage unit 44. As the measurement point designation information, for example, the image data of each reflected waveform shown in FIGS. 5A to 5D is stored. In other words, prior to measuring the axial force based on the propagation time, for example, when obtaining a calibration curve, measure the axial force directly with a load cell, etc., and gradually increase the axial force from a state where the axial force is not acting. The reflection waveform is confirmed for each axial force value when the action is strengthened, and the movement of the point corresponding to the representative point S in the waveform of FIG.

  For example, in FIG. 5, for each stage in which the axial force gradually increases in the order from (b) to (d), a point corresponding to the representative point S in the waveform of (a) is tracked, and (b) to (d ), Markers (circles in the figure) are attached in the vicinity of the corresponding points. Image data of the waveform with the marker is stored in the storage unit 44.

  Then, when measuring the axial force based on the propagation time, an image corresponding to the image data stored in the storage unit 44 is displayed on the display unit 42. The user (measurer) designates a measurement point based on the displayed image. The measurement point detector 32 detects a measurement point designated by the user from the waveform. As a result, for example, even when the reflection waveform (d ′) is obtained in the state where the axial force is applied, the representative point S is obtained from the correspondence with the waveform (d) stored as the measurement point designation information. It can be known that the point corresponding to is B point.

FIG. 6 is a diagram for further explaining how the reflected waveform changes in accordance with the axial force. FIGS. 6A to 6D show the axial force from 0 to F ₃ , respectively. The reflected waveform is shown. As in the case of FIG. 5, each reflected waveform corresponds to the waveform of FIG. That is, each of the reflected waveforms in FIGS. 6A to 6D shows a transmission waveform, a reflected waveform (one round trip), and a reflected waveform (two round trips) in order from the left. Further, the reflection waveform when the axial force is F ₃ is also shown in (d ′).

  As shown in FIGS. 6 (a) to 6 (d), the amplitude of each reflected waveform also changes as the axial force changes. Furthermore, as shown in (d), the polarity of the amplitude may change depending on the axial force value as compared with the waveform in the case of other axial force values. As described above, even when the amplitude changes, the points corresponding to the representative point S and the representative point S ′ in the waveform of (a) are determined at each stage where the axial force gradually increases in the order of (b) to (d). Tracking is performed, and markers (circles in the figure) are attached in the vicinity of corresponding points as shown in (b) to (d).

Then, the waveform image data to which the marker is attached is stored in the storage unit 44 and used as measurement point designation information when measuring the axial force based on the propagation time. Thereby, for example, even when the reflection waveform (d ′) is obtained in a state where the axial force is applied, from the correspondence relationship with the waveform (d) stored as the measurement point designation information, (a) It can be seen that the period corresponding to the period T ₀ between the representative point S and the representative point S ′ is the period T ₁ in (d ′).

  As described above, in the present embodiment, when the measurement point is detected from the waveform of the reflected wave in the measurement point detection unit 32, the measurement point designated based on the measurement point designation information stored in advance is detected. Therefore, the detection accuracy of the measurement point is improved.

  Incidentally, the measurement point detected from the reflected waveform when measuring the propagation time may be other than the peak point.

  FIG. 7 is a diagram for explaining the measurement points detected from the reflected waveform, and FIGS. 7A and 7B respectively correspond to the waveform of FIG. That is, the reflected waveforms in FIGS. 7A and 7B show the transmission waveform, the reflected waveform (one round trip), and the reflected waveform (two round trips) in order from the left. In FIG. 7A, an extreme point (peak point) is detected as a measurement point of the reflected waveform. In contrast, in FIG. 7B, the zero cross point, that is, the point at which the waveform changes from positive to negative or the point at which the waveform changes from negative to positive is used as the measurement point of the reflected waveform.

  Thus, the zero cross point may be detected as a measurement point of the reflected waveform. Incidentally, even when the zero cross point is used as the measurement point, as described with reference to FIGS. 5 and 6, the zero cross point ranges from the state where the axial force is not applied to the state where the axial force is applied. By storing the waveform image data to which the marker corresponding to is stored in the storage unit 44, the detection accuracy of the measurement point can be increased.

  Returning to FIG. 1, the control unit 46 controls each unit in the axial force measurement unit 30 and also controls the ultrasonic pulsar receiver 20 and the temperature measurement unit 50 connected to the axial force measurement unit 30. The display unit 42 displays the measured bolt axial force value, the reflected waveform obtained during the axial force measurement, a waveform image as measurement point designation information, and the like.

  The functional configuration of the bolt axial force measuring device according to the present invention has been described above. The function of the axial force measurement unit 30 in FIG. 1 can be realized by a computer, for example. That is, the computer can be caused to function as the axial force measuring unit 30 by causing a computer having a hardware configuration such as a CPU, a memory, and a hard disk to read a program for causing the computer to function as the axial force measuring unit 30. Further, the functions of the ultrasonic pulsar receiver 20 and the axial force measurement unit 30 in FIG. 1 may be configured in one apparatus.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention.

It is a functional lineblock diagram of a bolt axial force measuring device concerning the present invention. It is a figure for demonstrating the measurement principle of the propagation time of the ultrasonic wave in a volt | bolt. It is a figure for demonstrating the principle which derives | leads-out axial force from a propagation time difference. It is a figure for demonstrating the temperature dependence of ultrasonic propagation velocity and the temperature dependence of volt | bolt length. It is a figure for demonstrating a mode that a reflected waveform changes according to axial force. It is a figure for demonstrating further a mode that a reflected waveform changes according to an axial force. It is a figure for demonstrating the measurement point detected from a reflected waveform.

Explanation of symbols

  10 probe, 14 volts, 32 measurement point detector, 34 propagation time actual measurement unit, 36 correction coefficient calculation unit, 38 propagation time correction unit, 40 axial force calculation unit.

Claims (8)

In the bolt axial force measuring device that measures the axial force of the bolt based on the propagation time of the ultrasonic wave propagating in the bolt,
An ultrasonic transmission / reception unit that transmits ultrasonic waves to the bolts and receives reflected waves from the bolts;
A measurement point detector for detecting a measurement point from the waveform of the reflected wave;
Based on the measurement points detected from within each waveform of the reflected wave obtained a plurality of times, a propagation time measurement unit that actually measures the propagation time of the ultrasonic wave in the bolt from the time difference between the different measurement points,
A correction coefficient calculation unit that calculates a correction coefficient of propagation time reflecting the temperature dependence of the ultrasonic propagation velocity in the bolt, based on the temperature of the bolt at the time of actual measurement measured by the temperature measurement unit;
A propagation time correction unit that calculates a propagation time after temperature correction based on the actually measured propagation time and the calculated correction coefficient;
Having
Bolt axial force measuring device characterized by that. The bolt axial force measuring device according to claim 1,
The correction coefficient calculating unit corrects the correction based on at least a temperature coefficient of ultrasonic propagation velocity, a reference temperature of the bolt in a state where no axial force is applied, and a measured temperature of the bolt when the propagation time is actually measured. Calculate the coefficient,
Bolt axial force measuring device characterized by that. The bolt axial force measuring device according to claim 2,
The temperature coefficient of the ultrasonic propagation velocity is set for each bolt to be measured.
Bolt axial force measuring device characterized by that. In the bolt axial force measuring device that measures the axial force of the bolt based on the propagation time of the ultrasonic wave propagating in the bolt,
An ultrasonic transmission / reception unit that transmits ultrasonic waves to the bolts and receives reflected waves from the bolts;
A measurement point detector for detecting a measurement point from the waveform of the reflected wave;
Based on the measurement points detected from within each waveform of the reflected wave obtained a plurality of times, a propagation time measurement unit that actually measures the propagation time of the ultrasonic wave in the bolt from the time difference between the different measurement points,
Have
The measurement point detection unit detects a measurement point designated based on measurement point designation information stored in advance.
Bolt axial force measuring device characterized by that. The bolt axial force measuring device according to claim 4,
The measurement point is a point corresponding to a representative point in the waveform of the reflected wave in a state where no axial force is applied.
Bolt axial force measuring device characterized by that. In the bolt axial force measuring device according to claim 5,
The measurement point designation information is display information indicating the position of the point corresponding to the representative point in the waveform of the reflected wave in a state where the axial force is acting, and this display information is the position where the axial force is acting. Obtained by tracking the movement of the representative point from a state where no axial force is applied to a state where no axial force is applied.
Bolt axial force measuring device characterized by that. In the bolt axial force measuring method for measuring the axial force of the bolt based on the propagation time of the ultrasonic wave propagating in the bolt,
A measurement point detection step for detecting a measurement point from the waveform of the reflected wave obtained by transmitting and receiving ultrasonic waves to and from the bolt;
Based on the measurement points detected from within each waveform of the reflected wave obtained a plurality of times, a propagation time measurement step for actually measuring the propagation time of the ultrasonic wave in the bolt from the time difference between the different measurement points;
Based on the temperature of the bolt at the time of the actual measurement, a correction coefficient calculation step for calculating a correction coefficient of the propagation time reflecting the temperature dependence of the ultrasonic propagation velocity in the bolt;
A propagation time correction step of calculating a propagation time after temperature correction based on the actually measured propagation time and the calculated correction coefficient;
Having
Bolt axial force measuring method characterized by the above. In the bolt axial force measuring method for measuring the axial force of the bolt based on the propagation time of the ultrasonic wave propagating in the bolt,
A measurement point detection step for detecting a measurement point from the waveform of the reflected wave obtained by transmitting and receiving ultrasonic waves to and from the bolt;
Based on the measurement points detected from within each waveform of the reflected wave obtained a plurality of times, a propagation time measurement step for actually measuring the propagation time of the ultrasonic wave in the bolt from the time difference between the different measurement points;
Have
In the measurement point detection step, a measurement point designated based on measurement point designation information stored in advance is detected.
Bolt axial force measuring method characterized by the above.

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