JP3518296B2 - Axial stress measurement method and axial stress measurement device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring axial stress applied to a part such as a bolt in the axial direction based on the propagation time of a sound wave propagating in the part.

[0002]

2. Description of the Related Art As a method of fastening two or more parts, a fastening method using bolts is one of the most widely known methods. This fastening force is generated as a reaction force of an axial force that is a force applied in the axial direction of the bolt. Also, the axial force is
Since the axial stress is integrated in a cross section orthogonal to the axial direction, the axial force of the bolt can be measured by obtaining the axial stress. By measuring the bolt axial force, the force with which the bolt is fastening the plurality of parts can be known.

Various methods are known for measuring the axial force or stress of bolts. The most widely used method is to make measurements based on the torque to tighten the bolt. However, although this method is simple, there is a large error due to a large variation in the frictional force between the bolt and the component to be fastened, and in some cases sufficient accuracy cannot be obtained.

As another method, there is known a method of obtaining the bolt axial stress based on the propagation time of a sound wave propagating inside the bolt. When the axial stress is applied, the propagation time is extended because the bolt extends, and also the propagation time is extended when the sonic velocity is reduced due to the stress field due to the axial stress. In this method, the change in the propagation time is used to measure the axial stress of the bolt.

There is also known a method of measuring the axial stress by using the ratio of the sound velocity of the transverse wave and the sound velocity of the longitudinal wave propagating in the bolt. As described above, the speed of sound tends to decrease as the stress of the transmission medium increases, but the rate of decrease, that is, the acoustic elasticity coefficient, differs between longitudinal waves and transverse waves. Therefore, the axial stress of the bolt can be estimated from the ratio of the propagation times of the longitudinal wave and the transverse wave.

[0006]

In the measurement of axial stress using these sound waves, the axial stress distribution is uniform in a cross section orthogonal to the axis, like the axial portion of the bolt, and the axial stress is also present in the axial direction. The axial stress is calculated assuming a stress field that does not change. However, in an actual bolt, the stress distribution at the bolt head, particularly the stress distribution near the shaft, does not have the uniform distribution as described above. Further, the axial stress of the portion of the bolt provided on the bolt that is fitted with another component (hereinafter referred to as the screw fitting portion) becomes smaller toward the tip of the bolt, and the axial stress does not change in the axial direction. The assumption is not valid. Especially when the bolt length is relatively short,
There is a problem that the lengths of the bolt head and the threaded portion fitting portion that make up the entire length become relatively long, the stress distribution and deformation of these portions cannot be ignored, and the measurement error increases.

Further, the measurement is performed on the assumption that the formed stress field is always constant no matter how many times the bolt is tightened, but there is no way to confirm this, and this assumption does not hold. For example, this is an error when performing a measurement with such a high accuracy that this assumption cannot be established.

The present invention has been made in order to solve the above-mentioned problems, and the uneven stress distribution and deformation of the bolt head and the screw fitting portion, and the stress distribution each time an axial force is applied. An object of the present invention is to provide an axial stress measuring method and an axial stress measuring device that measure axial stress in consideration of the fact that the stress is not constant.

[0009]

In order to solve the above-mentioned problems, a method of measuring axial stress according to the present invention is designed so that the axial stress applied in the axial direction of the component is determined by the sound waves transmitted through the component. A method for measuring axial stress based on the propagation time between points, where the axial stress and the transverse or longitudinal wave propagation time of the acoustic wave before and after the axial stress are applied to the same type of component as the measurement target Difference between the propagation time and the step of obtaining the axial stress function, and the axial stress, and the propagation time of the transverse and longitudinal waves of the acoustic wave when the axial stress is applied in the same type of parts to be measured. From the step of obtaining the propagation time ratio-axis stress function indicating the relationship with the ratio, and from the difference in the propagation time of the transverse or longitudinal waves of the acoustic wave before and after the axial stress is actually applied to the measurement target component, the propagation time difference-axis Calculate time difference axial stress based on stress function And a step of calculating the propagation time ratio axial stress based on the propagation time ratio-axial stress function from the ratio of the propagation time of the transverse wave and the longitudinal wave of the sound wave when the axial stress is actually applied to the measurement target component. And, based on the propagation time difference axial stress, a step of calculating a modified propagation time difference axial stress which is the axial stress when the equivalent stress length ratio, which is the ratio of the equivalent stress length to the axial length of the component, is changed, Based on the propagation time ratio axial stress, a step of calculating a modified propagation time ratio axial stress that is an axial stress when the equivalent stress length ratio is changed, a step of calculating the modified propagation time difference axial stress, and the modified propagation time In the step of calculating the specific axial stress, the equivalent axial stress length ratio is sequentially changed, and when the difference between the modified propagation time difference axial stress and the modified propagation time ratio axial stress is substantially minimized, these modified stresses are corrected. It has a step of calculating the actual axial stress on the basis of the axial stress, the.

The equivalent stress length is the actual axial stress,
That is, it means the "certain axial length" when the elongation of the component due to the non-uniform axial stress and the elongation of the component when uniform axial stress is applied at a certain axial length match.

As described above, the axial stress measuring method according to the present invention obtains the axial force by two different methods. That is, the propagation time difference axial stress and the propagation time ratio axial stress are obtained. Since the axial stress is measured with respect to the same measurement object, these axial stresses should be the same, regardless of the measuring / calculating method. In this method, the reason why this does not match is that the equivalent stress length or its ratio is different from that when the relationship between the propagation time difference and the axial stress and the propagation time ratio and the axial stress is obtained. Suppose there is. Then, if the two axial stresses do not match, the equivalent stress length ratio is changed to calculate the two axial stresses again, and the equivalent stress length ratio when these match is the actual equivalent stress of the measurement target. It is assumed to be a length ratio, and the axial stress at this time is the actual axial stress. In reality, there are cases where the two axial stresses do not match due to other error factors, so the arithmetic mean of these two axial stresses when the difference between the two axial stresses is the minimum is calculated as the actual axial stress. .

Further, according to another aspect of the present invention, an axial stress measuring device determines an axial stress applied in the axial direction of a component based on a propagation time of a sound wave propagating in the component between predetermined points of the component. An axial stress measuring device for measuring, a transmitting means for transmitting a sound wave to the component, a receiving means for receiving the transmitted sound wave by separating the transverse wave and the longitudinal wave of the sound wave from the component, and the sound wave Propagation time measuring means for measuring the propagation time from transmission to reception, storage means for storing various functions of the same kind of component as the component to be measured, the stored various functions and the measured And a calculation means for calculating the axial stress of the measurement target component based on the propagation time of the sound wave.

The storage means stores the relationship between the axial stress and the difference in the propagation time of the transverse wave or the longitudinal wave of the acoustic wave before and after the axial stress is applied-the axial stress function, the axial stress, and the axial stress. Propagation time ratio showing the relationship between the transverse and longitudinal wave propagation times of a sound wave-the axial stress function, and the equivalent stress length ratio and sound wave, which is the ratio of the equivalent stress length to the axial length of the component. And a propagation time difference function, which is a relationship of the propagation time difference between the transverse wave and the longitudinal wave.

Further, the calculation means calculates the propagation time difference axial stress based on the propagation time difference-axial stress function from the difference in the propagation time of the transverse wave or longitudinal wave of the acoustic wave before and after the axial stress is actually applied to the component to be measured. Calculated, from the ratio of the propagation time of the transverse wave and the longitudinal wave of the sound wave when the axial stress is actually applied to the measurement target component, the propagation time ratio-calculating the propagation time ratio axial stress based on the axial stress function, Based on the propagation time difference axial stress and the propagation time difference function, calculate the modified propagation time difference axial stress which is the axial stress when the equivalent stress length ratio is changed, and based on the propagation time ratio axial stress and the propagation time difference function, the equivalent The modified propagation time ratio axial stress, which is the axial stress when the stress length ratio is changed, is calculated, and the equivalent axial stress length ratio is sequentially changed in the calculation of the modified propagation time difference axial stress and the modified propagation time ratio axial stress. The above When the difference between the positive propagation time Sajiku stress the modified propagation time ratio axis stress is substantially minimized, and calculates the actual axial stress based on these modified axial stress.

The program for causing a computer to execute at least part of the procedure of the axial force measuring method can be recorded in a computer-readable recording medium.

Further, as a recording medium suitable for carrying out the present invention, an axial stress applied to a component and a difference in propagation time of a transverse wave or a longitudinal wave of a sound wave between predetermined points of the component before and after the axial stress is applied. Time difference indicating the relationship between the axial stress function and the procedure for reading the axial stress function from memory, and the relationship between the axial stress and the ratio of the propagation time of the transverse wave to the longitudinal wave of the acoustic wave when the axial stress is applied. A procedure for reading the function from the memory, and a procedure for reading the propagation time difference function, which is the relationship between the equivalent stress length ratio, which is the ratio of the equivalent stress length to the axial length of the part, and the propagation time difference between the transverse and longitudinal waves of the sound wave, From the difference in the propagation time of the transverse wave or longitudinal wave of the acoustic wave before and after the axial stress is actually applied to the measurement target component, the procedure for calculating the propagation time difference axial stress based on the propagation time difference-axial stress function, and the actual measurement target component Axial stress is applied to From the ratio of the propagation time of the transverse wave and the longitudinal wave of the sound wave at the time, the procedure of calculating the propagation time ratio-axial stress based on the propagation time ratio-axial stress function, based on the propagation time difference axial stress and the propagation time difference function. , A procedure for calculating a modified propagation time difference axial stress that is the axial stress when the equivalent stress length ratio is changed, and based on the propagation time ratio axial stress and the propagation time difference function, when changing the equivalent stress length ratio In the procedure of calculating the modified propagation time ratio axial stress which is the axial stress, and in the modified propagation time difference axial stress and the modified propagation time ratio axial stress calculation, the equivalent axial stress length ratio is sequentially changed to A program for causing a computer to execute a procedure for calculating an actual axial stress based on the corrected axial stress when the difference between the stress and the corrected propagation time ratio axial stress is substantially minimum. It can be prepared a computer readable recording medium recording.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings. Figure 1
It is a block diagram which shows the outline of the apparatus of this embodiment. The measurement target is a hexagon bolt 14 (hereinafter simply referred to as bolt 14) that fastens the two components 10 and 12. An ultrasonic probe 16 that transmits a sound wave into the bolt 14 and receives a sound wave from the bolt 14 is arranged on the top of the bolt 14. In the present embodiment, the transmitted and received sound waves are generally ultrasonic waves of about 5 to 20 MHz. The ultrasonic transducer 16 is capable of generating transverse and longitudinal ultrasonic waves inside the bolt 14 and receiving them.
Any known probe can be used. Particularly, it is preferable to have a structure capable of simultaneously transmitting and receiving the transverse wave and the longitudinal wave. Further, when the bolt is warped, the propagation paths on the outside and inside of the warp are different, so it is preferable to arrange the transversal wave and longitudinal wave transmitter / receivers of the ultrasonic transducer so as to cancel them. For such an arrangement, for example, there is a method of arranging a transversal wave transmission / reception unit in the center and an annular longitudinal wave transmission / reception unit in the periphery thereof. In addition, transverse wave / longitudinal wave transmitter / receivers can be alternately arranged in each sector-shaped portion obtained by dividing a circle by a plurality of diameters. The transmission of ultrasonic waves is executed by a transmission signal transmitted from the transmission circuit 20 controlled by the transmission / reception control unit 18. In addition, the receiving circuit 22 uses the bolt 14
Receives the reflected wave reflected at the tip of the. Based on the time when the reflected wave is received and the time when the transmission control of the transmission / reception control unit 18 is performed, the time (propagation time) in which the ultrasonic wave reciprocates the entire length of the bolt 14 is calculated for each of the transverse wave and the longitudinal wave.
Is calculated.

In the memory 26, when the axial stress and the axial stress are applied, the propagation time difference-axial stress function showing the relationship between the axial stress and the difference in the propagation time of the transverse wave or the longitudinal wave of the acoustic wave before and after the axial stress is applied. Time Ratio-Axial Stress Function, which shows the relationship between the transverse wave and longitudinal wave propagation time ratios, and the equivalent stress length ratio, which is the ratio of the equivalent stress length to the axial length of the bolt, and the transverse wave of sound waves. And a propagation time difference function which is a relationship of the propagation time difference between the longitudinal waves. These functions are obtained in advance by the same kind of bolt 14 as the measurement object, that is, the bolt having the same material and shape.

The propagation time difference-axial stress function is the bolt 1
4 is obtained by measuring the propagation time of the sound wave before the axial force is applied to 4 and the propagation time of the sound wave after the axial force is applied, and calculating the difference between the axial stress and the propagation time at this time. The axial stress and the propagation time difference are calculated for a plurality of values of the axial force, and these approximate lines are defined as the propagation time difference-axial stress function. The propagation time of a sound wave can be measured using either a transverse wave or a longitudinal wave in principle, but in the present embodiment, the change in the sound velocity with respect to the axial stress is large, that is, it is obtained by a longitudinal wave with high measurement accuracy. ing.

The propagation time ratio-axial stress function is the bolt 1
4 is obtained by measuring the propagation time of the transverse wave and the longitudinal wave of the sound wave after the axial force is applied to 4, and calculating the ratio of the axial stress and the propagation time at this time. The axial stress and the propagation time ratio are calculated for a plurality of values of the axial amount, and these approximate lines are defined as the propagation time ratio-axial stress function.

The propagation time difference function is

[Equation 1] Is expressed as The details will be described later.

The calculation unit 28 calculates the axis based on the propagation time of the longitudinal wave before the axial force is applied to the bolt 14, the propagation time of the transverse wave and the longitudinal wave after the axial force is applied, and the above-mentioned plurality of functions. Calculate the force. First, the propagation time difference axial stress is calculated based on the difference between the propagation times of the longitudinal waves before and after the axial force is applied and the propagation time difference axial stress function. Further, the propagation time ratio axial stress is calculated from the ratio of the propagation time of the transverse wave and the longitudinal wave after the axial force is applied and the propagation time ratio-axial stress function. Although the propagation time difference axial stress and the propagation time ratio axial stress are different in the calculation method, they should be originally the same because they are measured for the same object. It is assumed that these do not match because the stress field when the above functions are obtained and the stress field when the actual measurement is performed are different, that is, the equivalent stress length or the ratio thereof is different. Below, the axial stress is calculated. The calculation of the axial stress will be described later in detail.

The transmission / reception control unit 18, the propagation time calculation unit 24, and the calculation unit 28 described above are actually a CPU (central processing unit) 30 that operates based on a predetermined program included in the computer. The above-mentioned program may be stored in an internal memory of a computer or may be stored in a CD-ROM.
(Compact disk-read-only memory) 32 and FD
It can also be stored in an external recording medium such as a (flexible disk). When stored in the above-mentioned external recording medium, a CD-ROM drive 34 for reading the stored information is provided.

Next, the method of calculating the axial force will be described in detail.
FIG. 2 shows a bolt 1 that is axially loaded and extends axially.
Four models are shown. The bolt 14 has a head 40
And a shaft portion 42 following the shaft portion 42, and a threaded portion 44 that is threaded around the shaft portion 42. The component 12 is screwed to the screw portion 44. The stress field within the bolt 14 is not actually uniform. That is, in the portion where the shaft diameter changes abruptly, such as in the vicinity of the joint between the bolt head 40 and the shaft 42, particularly in the head 40, complicated deformation occurs and the stress field also becomes complicated. Further, the axial stress of the portion that is screwed to the component 12 becomes smaller toward the tip. In the present embodiment, such a complicated stress field is formed as a uniform stress field, that is, a stress field in which only a uniform axial stress acts on a cylindrical portion having an equivalent stress length Le and an equivalent cross-sectional area Ae. Treat it as The equivalent stress length is the length of the cylindrical portion determined so that the elongation of the bolt due to the actually applied axial force and the elongation of the bolt due to the uniform stress field match. Further, hereinafter, the value obtained by dividing the equivalent stress length ratio, which is the equivalent stress length Le with respect to the bolt length L, by β and the axial force F by the equivalent cross-sectional area Ae, is the average axial stress σ, that is,

[Equation 2] β = Le / L (1) σ = F / Ae (2) As described below.

It is known that the speed of sound changes depending on the stress of the sound transmission medium, and the sonic speeds V _S and _VL of the transverse and longitudinal waves at the stress σ are the values when the stress is 0 (no load). Using longitudinal / transverse wave sound velocities V _S0 and V _L0 and sound elastic coefficients α _S and α _L ,

(3) V _S = V _S0 (1-α _S σ) (3) V _L = V _L0 (1-α _L σ) (4) Note that, hereinafter, when the equations of the transverse wave and the longitudinal wave are the same, the subscripts " _S " and " _L " will be omitted.

Also, a minute portion d of the equivalent stress length of the bolt
Since x is an elongation that is loaded with an axial stress, the sound wave propagation time of this portion is

[Equation 4] Is expressed as From the above, the time it takes for the ultrasonic waves to reciprocate over the entire length of the bolt is calculated by combining the propagation time of the unstressed part (L-Le)

[Equation 5] Is expressed as Furthermore, the change due to the axial force being applied, that is, the difference ΔT in the propagation time of the sound wave before and after the axial force is applied.
Is

[Equation 6] It is represented by. From equations (6) and (7), in this model, the equivalent stress length ratio β, the propagation time T and the propagation time ΔT
It can be seen that has a linear relationship with.

First, in a bolt of the same type as the bolt for actually measuring the axial force, the relationship between the axial stress and the difference in sound wave propagation time before and after the axial stress is applied is determined. The propagation time difference ΔT is obtained for a plurality of values of the axial stress σ, and the graph is shown by taking the axial stress σ on the horizontal axis and the propagation time difference ΔT on the vertical axis. If an approximate line is obtained, the solid line graph of FIG. Obtainable. The function represented by this solid line is the propagation time difference-axial stress function.

Further, in a bolt of the same type as the bolt for actually measuring the axial force, the relationship between the axial stress and the ratio of the propagation time of the transverse wave to the longitudinal wave of the sound wave when the axial stress is applied is obtained.
If the propagation time ratio T _S / T _L is calculated for a plurality of values of the axial stress σ, the horizontal axis represents the axial stress σ, and the vertical axis represents the propagation time ratio T _S / T _L. The solid line graph of FIG. 3B can be obtained. The function represented by this solid line is the propagation time ratio-axial stress function.

Next, ultrasonic waves are transmitted and received to measure the propagation time in a state where no axial force is applied to the bolt 14 to be measured, that is, in a state of no load. From this propagation time, the difference between the length of the bolt when the graphs of FIGS. 3A and 3B are created and the length of the bolt 14 to be measured can be known. Next, the bolt 14 is tightened, ultrasonic waves are transmitted / received under a state where an axial force is applied, that is, a load state, and the propagation time is measured. Difference in propagation time before and after bolt tightening Δ
The axial stress (transmission time difference axial stress) σ _D is calculated from T _M and the propagation time difference-axial stress function of FIG. In addition, the ratio of the propagation time of the transverse wave and the longitudinal wave of the sound wave after tightening the bolt T _S / T
_The axial stress (propagation time ratio axial stress) σ _R is calculated from _L and the propagation time ratio-axial stress function of FIG. At this time, in order to eliminate the influence of the error due to the individual difference in the length of the bolt, the correction is performed from the propagation time in the unloaded state.

As described above, the two axial stresses σ _D and σ _R should originally be the same because the measurement objects are the same but the measurement methods are different. These do not match because the stress field when creating FIGS. 3A and 3B does not match the stress field at the time of actual measurement, that is, the equivalent stress length Le or the equivalent stress length ratio β. Is considered to be not equal. When the equivalent stress length ratio β changes, as described above, the propagation time and the propagation time difference change linearly from the equations (6) and (7). Therefore, the propagation time difference −
The axial stress function and the propagation time ratio-axial stress function are shown in FIG.
It changes like the broken line shown in (b). Therefore, assuming the rate of change of the equivalent stress length ratio β with respect to the values when the propagation time difference-axis stress function and the propagation time ratio-axis stress function are calculated, the axis for the hypothesized equivalent stress length ratio β ' The stress (corrected propagation time difference axis stress σ _D ', modified propagation time ratio axis stress σ _R ') can be calculated. These two modified axial stress σ _D ',
sigma _R 'difference _{Δσ (= σ R' -σ D} ') are equivalent stress length ratio β as shown in FIG. 3 (c)' minimum values for .DELTA..sigma _M
Have. It is considered that this minimum value Δσ _M is ideally 0, that is, σ _D '= σ _R ', but in reality, there are other error factors and it does not become 0. Thus, two modified shaft stress σ _D ', σ _R' taking the arithmetic mean of the calculated this as axial stress sigma at that time.

FIG. 4 is a chart showing the flow of the axial force measuring method of this embodiment. As a preparation, a memory stores a propagation time difference-axial stress function, which is measured in advance with a bolt of the same kind as the bolt to be measured and which shows the relationship between the propagation time difference before and after tightening and the axial stress. In addition, a propagation time ratio-axial stress function indicating the relationship between the axial stress and the ratio of the propagation time of the transverse wave and the longitudinal wave of the tightened sound wave is stored in the memory. These functions are the solid lines in FIGS. 3 (a) and 3 (b).

Next, sound waves are transmitted and received with no load applied to the bolt to be actually measured, and the propagation time is measured (S100). Further, the sound waves are transmitted / received in a loaded state with the bolts tightened (S102). Based on these measurements, the difference in propagation time before and after bolt tightening Δ
T _M and the propagation time ratio T _S / T _L of the transverse wave and the longitudinal wave after tightening the bolt are calculated (S104, S106). The axial stress σ _D is calculated from the propagation time difference ΔT _M and the propagation time difference-axial stress function, and the equivalent stress length β is changed to calculate the corrected propagation time difference axial stress σ _D ′ (S108). By changing the equivalent stress length β, the propagation time difference-axial stress function becomes a function as shown by the broken line in FIG. 3A, and even if the propagation time difference ΔT _M is the same, the axial stress depends on the value of the equivalent stress length β. Takes different values. Further, the axial stress σ _R is calculated from the propagation time ratio T _S / _TL and the propagation time ratio-axial stress function, and the equivalent stress length β is changed to modify the modified propagation time ratio axial stress σ _R '
Is calculated (S110). By changing the equivalent stress length β, the propagation time ratio-axial stress function becomes a function as shown by the broken line in FIG. 3B, and even if the propagation time ratios T _S / T _L are the same, the equivalent stress length β The axial stress varies depending on the value.

Then, the difference Δσ between the two axial stresses σ _D 'and σ _R ' determined by different methods is minimized.
By changing the equivalent stress length β in steps S108 and S110, the arithmetic mean of the two axial stresses σ _D ′ and σ _R ′ when the difference Δσ in axial stress is minimized is calculated as the axial stress σ at that time. (S112).

FIG. 5 is a diagram showing the effect of the measuring method of this embodiment. The horizontal axis shows the change rate of the equivalent stress length β,
The vertical axis represents the error rate of the calculated axial stress with respect to the actual axial stress obtained by strain measurement or the like. The triangles (Δ) in the figure are data calculated without correction for changing the equivalent stress length, and the solid line is an approximate line of these data. Further, the black circles (●) in the figure are data obtained by changing the equivalent stress length according to the measuring method of the present embodiment, and the alternate long and short dash line is an approximate line of these data. From this result, it can be seen that even if the equivalent stress length β changes in the actual measurement, the effect thereof is small.

In this embodiment, the case where the axial stress at the time of tightening the bolt is measured has been described as an example, but it can be applied to the case where the axial stress of other parts is measured.
Further, in the present embodiment, the propagation time of the sound wave traveling back and forth over the entire length of the bolt was measured. That is, the case where the point of transmitting the sound wave and the point of receiving the sound wave are the same point has been described, but the propagation time from one end of the bolt to the other end may be measured, and the two points that are easy to measure depending on the shape of parts You can take time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a measuring apparatus of this embodiment.

FIG. 2 is a diagram showing a model of a bolt.

FIG. 3 is a diagram for explaining the measuring method of the present embodiment.

FIG. 4 is a flowchart showing a measuring method of the present embodiment.

FIG. 5 is a diagram showing axial stress data measured by the measurement of the present embodiment.

[Explanation of symbols]

14 (hexagonal) bolt, 16 ultrasonic probe (transmission means, reception means), 18 transmission / reception control section, 20 transmission circuit (transmission means), 22 reception circuit (reception means), 24 propagation time calculation section (transmission time measurement) Means), 26 memory (storage means), 28 operation unit (operation means), 32 CD-RO
M (recording medium), 34 CD-ROM drive, β equivalent stress length ratio (= Le / L), σ axis stress, σ _D propagation time difference axis stress, σ _D 'corrected propagation time difference axis stress, σ _R propagation time ratio Axial stress, σ _R 'Modified propagation time ratio axial stress.

Claims (3)

(57) [Claims] 1. A method for measuring an axial stress applied in the axial direction of a component based on a propagation time of a sound wave propagating through the component between predetermined points of the component, which is a measurement target. In the same type of parts, the step of obtaining the propagation time difference-axial stress function that shows the relationship between the axial stress and the difference in the propagation time of the transverse or longitudinal waves of the acoustic wave before and after the axial stress is applied, and the part to be measured In the same type of parts, the step of obtaining the propagation time ratio-axial stress function, which shows the relationship between the axial stress and the ratio of the propagation time of the transverse wave and the longitudinal wave of the sound wave when the axial stress is applied, From the difference in the propagation time of the transverse or longitudinal waves of the acoustic wave before and after the axial stress is actually applied, the propagation time difference −
Propagation time difference based on the axial stress function The step of calculating the axial stress, and the ratio of the propagation time of the transverse wave and the longitudinal wave of the acoustic wave when the axial stress is actually applied to the measurement target component, the propagation time ratio-the axial stress function And a step of calculating the propagation time ratio axial stress based on the above, based on the propagation time difference axial stress, is the axial stress when changing the equivalent stress length ratio which is the ratio of the equivalent stress length to the axial length of the component A step of calculating a modified propagation time difference axial stress, a step of calculating a modified propagation time ratio axial stress that is an axial stress when the equivalent stress length ratio is changed based on the propagation time ratio axial stress, and the modified propagation time difference In the step of calculating the axial stress and the step of calculating the modified propagation time ratio axial stress, the equivalent axial stress length ratio is sequentially changed, and the difference between the modified propagation time difference axial stress and the modified propagation time ratio axial stress is Calculating the actual axial stress based on these modified axial stresses when substantially minimized. 2. An axial stress measuring device for measuring axial stress applied in the axial direction of a component based on a propagation time of a sound wave propagating through the component between predetermined points of the component, wherein Transmitting means for transmitting a sound wave, receiving means for receiving the transmitted sound wave by separating the transverse and longitudinal waves of the sound wave from the component, and measuring the propagation time from the transmission of the sound wave to the reception Propagation time measurement means and storage means for storing various functions in the same kind of parts as the measurement target parts, wherein the storage means are the axial stress and the propagation of transverse or longitudinal waves of acoustic waves before and after the axial stress is applied. Propagation time difference-Axial stress function that shows the relationship with time difference, and Propagation time ratio-Axial stress function that shows the relationship between axial stress and the ratio of the propagation time of transverse wave and longitudinal wave of sound wave when axial stress is applied And the equivalent stress for the axial length of the part A storage means for storing the equivalent stress length ratio, which is the ratio of the thickness, and the propagation time difference function, which is the relationship between the propagation time differences of the transverse and longitudinal waves of sound waves, and a calculation means for calculating the axial stress of the measurement target component. The calculation means calculates the propagation time difference from the difference in the propagation time of the transverse wave or longitudinal wave of the acoustic wave before and after the axial stress is actually applied to the measurement target component.
Propagation time difference based on the axial stress function Calculate the axial stress, and from the ratio of the propagation time of the transverse wave and the longitudinal wave of the acoustic wave when the axial stress is actually applied to the measurement target component, based on the propagation time ratio-axial stress function Calculate the propagation time ratio axial stress, based on the propagation time difference axial stress and the propagation time difference function,
Calculate the modified propagation time difference axial stress is the axial stress when the equivalent stress length ratio is changed, based on the propagation time ratio axial stress and the propagation time difference function,
Calculate the modified propagation time ratio axial stress which is the axial stress when the equivalent stress length ratio is changed, and in the calculation of the modified propagation time difference axial stress and the modified propagation time ratio axial stress, the equivalent axial stress length ratio is sequentially change,
And a calculation means for calculating an actual axial stress based on these modified axial stresses when the difference between the modified propagation time difference axial stresses and the modified propagation time ratio axial stresses is substantially minimized. Calculator. 3. A propagation time difference-axial stress function indicating the relationship between the axial stress applied to a part and the difference in the propagation time of a transverse wave or a longitudinal wave of a sound wave between predetermined points of the part before and after the axial stress is applied from a memory. The procedure to read, the procedure to read the axial stress and the ratio of the propagation time of the transverse wave to the longitudinal wave of the sound wave when the axial stress is applied-the procedure to read the axial stress function from the memory, and the axial length of the part Of the equivalent stress length ratio, which is the ratio of the equivalent stress length to the length, and the procedure for reading the propagation time difference function, which is the relationship between the propagation time difference between the transverse and longitudinal waves of a sound wave, and From the difference in the propagation time of the transverse or longitudinal waves of the sound wave, the propagation time difference −
Propagation time difference based on the axial stress function Procedure to calculate the axial stress, and the ratio of the propagation time of the transverse wave and the longitudinal wave of the acoustic wave when the axial stress is actually applied to the measurement target component, the propagation time ratio-axial stress function Based on the procedure to calculate the propagation time ratio axial stress, based on the propagation time difference axial stress and the propagation time difference function,
Based on the procedure of calculating a modified propagation time difference axial stress that is the axial stress when the equivalent stress length ratio is changed, based on the propagation time ratio axial stress and the propagation time difference function,
A procedure for calculating a modified propagation time ratio axial stress that is an axial stress when the equivalent stress length ratio is changed, and an equivalent axial stress length ratio in calculating the modified propagation time difference axial stress and the modified propagation time ratio axial stress. Sequentially changed,
Causing the computer to execute a procedure of calculating an actual axial stress based on the corrected propagation time difference axial stress and the corrected propagation time ratio axial stress when the difference between the corrected propagation time difference axial stress is substantially minimum. A computer-readable recording medium in which a program for recording is recorded.