JPH05164631A - Method and apparatus for measuring stress - Google Patents

Abstract

PURPOSE:To measure the tensile stress of wire and the like accurately by arranging transmitting and receiving ultrasonic transducers so as to face the measuring surface of a material to be measured, and computing the stress based on the propagating time of the obtained surface wave of the object. CONSTITUTION:An ultrasonic transceiver 10 is brought into contact with the surface of a wire 4. A time-measurement starting signal is outputted from a time measuring part 55 at a time t1 into a pulser circuit 51. A part of a longitudinal ultrasonic wave B, which is outputted from a piezoelectric element 1B, is absorbed with an absorbing material 1C at the boundary plane between a resin part 1A and the wire 4. The propagation mode of the remaining part is converted, and a lateral surface wave C is obtained. The wave C is propagated on the surface of the wire 4 and converted into the longitudinal ultrasonic wave D at the boundary plane between a resin part 2A and the wire 4. The wave D is received with a piezoelectric element 2B through the resin part 2A and converted into the pulse signal. The wave form of the pulse signal is shaped into the square wave in a comparator 54. The signal is inputted into the time measuring part 55 at a time t2. In the time measuring part 55, the time DELTAt from t1 to t2 is measured. In a computer 56, the net propagating time of the surface wave is computed based on the time DELTAt. The difference between the propagating times caused by the presence or absence of the stress acting on the wire is multiplied by A proportional coefficient and temperature coefficient, and the tensile stress is computed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stress measuring method and apparatus, and more particularly, to measuring tensile stress acting on a thin rod or wire made of metal, resin or other material capable of transmitting ultrasonic waves. The present invention relates to a stress measuring method and a device suitable therefor.

[0002]

BACKGROUND ART Conventionally, the measurement of tensile stress acting on a wire or the like is often performed by human intuition, and the stress acting on the wire or the like is not precisely measured, but in practice, As a method of measuring the stress, there is a method of attaching a strain gauge or the like to the wire and measuring the tensile stress acting on the wire by the output of the strain gauge.

In addition, an ultrasonic stress measuring device as shown in FIG. 4 is used for measuring the axial stress acting on the bolt and the like. The ultrasonic stress measuring device shown in this figure includes a pulsar circuit 51 which receives a time measurement start signal and outputs ultrasonic transducer driving pulses, and a pulsar circuit 5
The pulse output from 1 is electroacoustically converted and output as a longitudinal ultrasonic wave, and this ultrasonic wave is received in the bolt 60, which is a symmetrical object of measurement, after propagating as shown by an arrow E in the figure and reconverted into an electric signal. A transmitting / receiving ultrasonic transducer (ultrasonic sensor) 52, a wide band amplifier 53 for amplifying a received signal from the ultrasonic transducer 52 to a sufficient amplitude, and a square wave pulse for the received signal amplified by the wide band amplifier 53. A comparator 54 that shapes the waveform into
A square wave pulse is input from the comparator 54, and a time measurement unit 55 that measures the time from the time measurement start signal output to the square wave pulse input and an output signal from the time measurement unit 55 are received to perform a predetermined calculation. A computer 56 for calculating the stress acting on the bolt 60 and a temperature sensor 59 for sending a signal according to the detected temperature to the computer 56 via the A / D converter 57 are provided. The computer 56 has a display unit 5 for displaying measurement results.
8 are installed side by side.

Next, the operation of the stress measuring device shown in FIG. 4 when measuring the bolt axial force will be described. Prior to the start of measurement, the temperature sensor 58 is brought into contact with part of the bolt 60, which is a symmetrical object of measurement. When the measurement of the bolt axial force is started in this state, a time measurement start signal is output from the time measurement unit 55 to the pulsar circuit 51 at the time t ₁ , and the pulsar circuit 51 receives the time measurement start signal to input the ultrasonic transducer. Generates drive pulses. This drive pulse is sent to the ultrasonic transducer 52, and the ultrasonic transducer 52 electro-acoustic converts the pulse output from the pulser circuit 51 and outputs it as a longitudinal ultrasonic wave. This longitudinal ultrasonic wave propagates as indicated by reference numeral E in the figure, is input again to the ultrasonic transducer 52, and is converted into an electric signal again. Then, this received signal is converted into a wide band amplifier 5
After being amplified to a sufficient amplitude at 3, the comparator 54 compares it with a predetermined reference voltage to shape it into a square wave pulse, and then inputs it to the time measuring section 55 at time t ₂ . In the time measuring unit 55, the time Δt = t ₂ −t ₁ from t ₁ to t _2.
Is measured and the result is sent to the computer 56.

By the way, since the time t _e required for the electric signal to propagate through the electric circuit is included as an error in the Δt, the net ultrasonic wave propagation time Δt _u is subtracted from the error. Need to ask.

Δt _u = Δt−t _e = t ₂ −t ₁ −t _e ………………

Further, when the stress is measured using ultrasonic waves, the propagation time of ultrasonic waves changes due to both the acoustic elasticity effect and the longitudinal strain in the stress direction of the object to be measured, and this change amount is the stress. It is known to be proportional to. Therefore, if the difference Δt _ud between the propagation time Δt _{ub of the} ultrasonic wave when no stress is applied and the propagation time Δt _{ua of the} ultrasonic wave when the stress is applied, this Δt _ud is proportional to the stress. Therefore, Δt
_The stress u can be obtained by multiplying _ud by a proportional coefficient k previously obtained by experiments or the like.

U = k · Δt _ud = k (Δt _ua −Δt _ub ) ...

Since the proportional coefficient k in the above equation is affected by temperature, it can be expressed as in the following equation by using the temperature coefficient α obtained in advance by experiment.

K = k ₂₅ {1 + α (T-25)} ………………

Here, T is the temperature [° C.] of the object to be measured, k
₂₅ is a proportional coefficient at 25 ° C.

From the above, the stress u is finally calculated by the following equation.

U = k (Δt _ua −Δt _ub ) = k ₂₅ {1 + α (T-25)} (Δt _ua −Δt _ub ) ...

Therefore, in the computer 56, Δt _ub is obtained by an equation in advance in a state where no stress acts on the bolt 60, and this is stored in the memory, and Δt = t ₂ at the time of stress measurement.
When −t ₁ is sent from the time measuring unit 55, Δt _ua is obtained by an equation, and finally the axial force acting on the bolt 60 is calculated by the equation, and the result is sent to the display unit 58.

When a separate ultrasonic transducer dedicated to reception is provided, a changeover switch is provided at point A in FIG. 4, and an ultrasonic transducer dedicated to reception is connected to the changeover switch, and the ultrasonic wave is changed by the changeover switch. The same measurement can be performed by disconnecting the transducer 52 from the wide band amplifier 53 and connecting the output of a newly provided ultrasonic transducer exclusively for reception to the wide band amplifier 53.

[0016]

In the strain gauge system described above, the strain gauge has to be adhered to an object to be measured such as a wire by using an adhesive, which is inconvenient and troublesome. It was Further, in the above-described ultrasonic method, when the measurement object is a bolt or the like, it is sufficient to bring the ultrasonic transducer into contact with the measurement object via a couplant agent (water, oil, glycerin, etc.), Although stress can be easily measured, it is virtually impossible to attach an ultrasonic transducer to the end face of the wire under stress when trying to measure the tensile stress of the wire. There is a problem that the tensile stress of the wire or the like cannot be measured using the transducer.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art, and an object thereof is a stress measuring method capable of easily and accurately measuring the tensile stress of a wire or the like by using ultrasonic waves. And to provide the device.

[0018]

In order to achieve the above object, in a stress measuring method according to the present invention, a side surface of an object to be measured at a predetermined incident angle of a critical angle or more from a piezoelectric element constituting a transmitting ultrasonic transducer. Longitudinal wave ultrasonic wave is output through the resin part to generate a surface wave by converting the propagation mode of the ultrasonic wave at the boundary surface between the resin part and the measurement object, and this surface wave is generated on the side surface of the measurement object. After propagating along the surface in the axial direction, the ultrasonic wave on the boundary surface of the object to be measured and the resin portion constituting the ultrasonic transducer on the receiving side, which is arranged at a predetermined distance from the ultrasonic transducer on the transmitting side, in the propagation direction of the surface wave. The sound wave propagation mode is reconverted into longitudinal ultrasonic waves, and the longitudinal ultrasonic waves are received by the piezoelectric element via the resin section. Piezoelectric element receives longitudinal ultrasonic waves The ultrasonic wave propagation time of up to measurement,
From the measured ultrasonic wave propagation time, the ultrasonic wave propagates in a known electric circuit, the ultrasonic wave propagation time at a known reference temperature, and longitudinal ultrasonic waves in the resin portion whose temperature is corrected based on the temperature characteristics. The propagation time of the surface wave is calculated by subtracting the total propagation time of the surface wave and the propagation time of the surface wave. Then, the stress of the measured symmetric object is calculated by multiplying the difference between the two propagation times by a predetermined proportional coefficient that has been temperature-corrected by temperature counting previously obtained by an experiment or the like.

Further, the stress measuring apparatus of the present invention receives a time measurement start signal and outputs a pulse for ultrasonic transducer driving, and a pulse generating means, and the pulse from this pulse generating means is electroacoustic converted and output as an ultrasonic wave. An ultrasonic transducer on the transmitting side, an ultrasonic transducer on the receiving side which is provided corresponding to the ultrasonic transducer on the transmitting side and receives ultrasonic waves and converts it into a pulse signal, and inputs the pulse signal and outputs the time measurement start signal To the input of the pulse signal, a time measuring unit, a calculating unit that receives an output signal from the time measuring unit and performs a predetermined calculation to calculate the stress acting on the measurement object, and the calculating unit detects the stress. And a temperature sensor that sends a signal according to the temperature. Then, both ultrasonic transducers are attached to the resin portion and a fixed attachment angle to the resin portion, and the angle formed by the normal line with respect to the axis orthogonal to the bottom surface of the resin portion is the resin portion and the object to be measured. And a piezoelectric element that coincides with the incident angle of the ultrasonic wave when a surface wave is generated at the boundary surface between and. Further, a temperature sensor is provided on either one of the two ultrasonic transducers. Further, the ultrasonic transducers are arranged at a constant distance so that the bottom surfaces of the respective resin parts are located on the same plane, and the normal lines of the respective piezoelectric elements intersect at one point,
It is integrated by the frame. With such a configuration, the above-described object is to be achieved.

[0020]

In the stress measuring method according to the present invention, the ultrasonic transducers on the transmitting side and the receiving side are arranged facing each other on the side surface of the measuring object such as a wire with a constant distance therebetween, and the temperature sensor is measured. By simply contacting the surface of the object, the computer calculates the net propagation time of the surface wave from the propagation time of the ultrasonic wave, and the propagation time of this surface wave is used to calculate the stress acting on the measurement object. Moreover, the temperature can be corrected based on the temperature detected by the temperature sensor, and the accurate stress can be calculated.

Further, in the stress measuring apparatus of the present invention, the ultrasonic transducers on the transmitting side and the receiving side, which are integrated by the frame, are arranged so that the bottom surfaces of the respective resin portions are in contact with the side surfaces of the object to be measured, and the measurement is performed. Starts at time t ₁
A time measurement start signal is output from the time measurement unit to the pulser circuit, and the pulser circuit generates an ultrasonic transducer driving pulse by inputting the time measurement start signal. This ultrasonic transducer driving pulse is sent to the transmitting ultrasonic transducer, and in the transmitting ultrasonic transducer, the pulse output from the pulser circuit is electroacoustically converted by the piezoelectric element and output as a longitudinal ultrasonic wave. Then, the output longitudinal ultrasonic wave propagates toward the measurement object via the resin portion, the propagation mode is converted at the boundary surface between the resin portion and the measurement object, and a surface wave is generated. After this surface wave propagates along the surface of the measurement object, the propagation mode is converted again at the boundary surface between the resin portion that constitutes the reception side transducer and the measurement object to become a longitudinal ultrasonic wave. It is received by the piezoelectric element via the resin portion and converted into an electric signal. This electric signal is time t
Input into the time measurement section in ₂ . The time measuring unit measures the time Δt from t ₁ to t ₂ and sends the result to the calculating means. The calculation means performs a predetermined calculation based on this time Δt to calculate the stress acting on the measurement object. When calculating this stress, the calculation means performs a predetermined temperature correction based on the temperature detected by the temperature sensor to calculate an accurate stress.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to FIGS. Here, the same reference numerals will be given to the same or equivalent components as those of the conventional example of FIG. 4 described above, and the description thereof will be simplified or omitted.

FIG. 1 shows the configuration of an embodiment of the present invention. In the embodiment of FIG. 1, an ultrasonic transducer for transmission / reception (hereinafter, abbreviated as “transducer”) 52 in the related art shown in FIG. 4 is used.
It is characterized in that a transmitting side transducer 1 and a receiving side transducer 2 are provided instead. These transmitting side transducer 1 and receiving side transducer 2
Actually, as shown in FIG. 2, the resin parts 1A and 2A and the resin parts 1A and 2A are
The piezoelectric elements 1B and 2B are attached so as to form a constant angle θ (which will be described later) with respect to the axis orthogonal to the bottom surface of A. A temperature sensor 59 is integrally fixed to the left end portion of the bottom surface of the resin portion 1A on the transmission side in FIG. 2 (this portion is a portion where ultrasonic waves generated in the piezoelectric element 1B do not propagate). There is. And both transducers 1 and 2 are
The bottom surfaces of the respective resin portions 1A and 2A are arranged at a constant distance so as to be located on the same plane, and the normal lines of the respective piezoelectric elements 1B and 2B are arranged so as to face each other at a point O. Further, a special ultrasonic wave transmitter / receiver 10 is configured by being integrated with the frame 3 shown in FIG. An elongated hole-shaped cutout 3A is formed in the center of the frame 3, and the entire ultrasonic wave transmitter / receiver 10 can be easily carried by putting a finger on the cutout 3A. In FIG. 2, reference numeral 4 represents a wire as a measurement object, and reference numerals 1C and 2C are sound absorptions for absorbing extra longitudinal ultrasonic waves reflected at the boundary surface between the resin portions 1A and 2A and the wire 4. Indicates the material. In FIG. 1, the configuration of the other parts is almost the same as the conventional example of FIG.

In FIG. 2, when a longitudinal ultrasonic wave is output from the piezoelectric element 1B on the transmission side (see reference numeral B in FIG. 2), this longitudinal ultrasonic wave propagates in the resin portion 1A and becomes a wire 4. At the boundary surface of, the reflection, refraction, and conversion of the ultrasonic propagation mode are performed.

Here, the operating characteristics of ultrasonic waves at the general interface between the substance X and the substance Y will be described with reference to FIG. When an ultrasonic wave is incident on the interface between the substance X and the substance Y at a certain incident angle θ _i , a part of the ultrasonic wave is reflected at the interface at the reflection angle θ _r , and the rest propagates to the substance Y at the refraction angle θ _t . At this time, the reflection angle θ _r and the refraction angle θ _{t with} respect to the incident angle θ _i satisfy the following equations with the sound velocities C _i , C _r and C _t of the ultrasonic waves according to Snell's law. To do.

Sin θ _i / C _i = sin θ _r / C _r = sin θ _t / C _t

Here, when the sound velocity C _t of the substance Y is higher than the sound velocity C _{i of the} substance X, the incident angle θ satisfying the relation of the following equation:
_i always exists.

Sin θ _i = C _i / C _t · sin θ _t = C _i / C _t ……………

That is, sin θ _t = 1 [θ _t = 90 degrees (d
eg _i )] exists, and when θ _i is more than this, the transmission wave to the substance Y is not generated, and this θ _i is called a critical angle. Here, if polystyrene is used as the substance X and resin is used as the substance Y, and aluminum or steel is used as the substance Y, the sonic velocity is 2340 m /
s, 6300 m / s, 5900 m / s, the critical angles of the respective materials are θ _CAl = 21.80 deg,
θ _CFe = 23.37 deg. At an incident angle larger than this, longitudinal waves are not generated in the substance Y, and only transverse waves are generated.

Next, by further increasing θ _{i so} that the transverse wave (surface wave) generated has a refraction angle of 90 deg, a surface wave (see symbol C in FIG. 2) is obtained. Here, the speed of sound of surface waves of mild steel and aluminum is 2 respectively.
Since the material X is 980 m / s and 2975 m / s, if the substance X is polystyrene, which is a resin material, the incident angle θ _i = s
in ⁻¹ (2340/2980) ≈ sin ⁻¹ (2340 /
When 2975) ≈51 deg, a surface wave is generated. Therefore, also in the present embodiment, assuming that the wire 4 is made of steel and the resin portions 1A and 2A are made of polystyrene, the attachment angle of the piezoelectric elements 1B and 2B described above (the piezoelectric elements 1B and 2B are Normal parts are resin parts 1A, 2A
Angle is 50d.
It is preset to eg. (When using other materials, the mounting angle of the piezoelectric element may be determined according to the sound velocity of each material.)

Next, the operation in the case of measuring the tensile stress in the axial direction of the wire 4 by using the apparatus of this embodiment constructed as described above will be described.

First, the operator (measuring person) brings the frame 3 portion of the ultrasonic wave transmitter / receiver 10 into contact with the surface of the holding wire 4 as described above (see FIG. 2) prior to the measurement. Then, the measurement is started, and at time t ₁ , the time measuring unit 5
When the time measurement start signal is output from 5 to the pulser circuit 51 as the pulse generating means, the piezoelectric element 1B of the transmitting side transducer 1 is subjected to the longitudinal ultrasonic wave in the same manner as described in the section of the conventional example. (See reference numeral B in FIG. 2) is output. Then, the outputted longitudinal ultrasonic wave propagates through the resin portion 1A, and then, at the boundary surface with the wire 4, a part of the ultrasonic wave is reflected and absorbed by the sound absorbing material 1C, and the rest is converted into a propagation mode by a transverse wave. It becomes a certain surface wave (see symbol C in FIG. 2).
Then, after the surface wave propagates along the surface of the wire 4 in the direction of arrow F in FIG. 2, the propagation mode is reconverted at the boundary surface between the resin portion 2A on the receiving side and the wire 4 and the longitudinal ultrasonic wave (FIG. 2 (reference numeral D in FIG. 2) is received by the piezoelectric element 2B via the resin portion 2A of the receiving side transducer 2 and converted into a pulse signal. This pulse signal is shaped into a square wave by the comparator 54 and input to the time measuring unit 55 at time t ₂ . The time measuring unit 55 measures the time Δt from t ₁ to t ₂ and sends the result to the computer 56 as a calculation means. In the computer 56, this time Δt
Based on, the following equation is calculated to calculate the net propagation time of the surface wave.

[0033] _{Δt u = Δt-t e -t} p = t 2 -t 1 -t e -t p ..................

Here, t _p is the propagation time of the longitudinal ultrasonic wave in the resin whose temperature is corrected, and in the computer 56,
The propagation time of the longitudinal ultrasonic wave in the resin at the reference temperature previously obtained in the experiment or the like and its temperature characteristic are stored in the memory as a map, and based on this, t _p of the temperature detected by the temperature sensor 59 is determined. Calculate the value. Note that the value of t _p may be calculated using an approximate expression indicating the temperature characteristic instead of the map.

Then, in the computer 56, similarly to the conventional example, the propagation time Δt _ub of the surface wave when the stress is not applied to the wire 4 and the propagation time Δt _ua of the surface wave when the stress is applied are calculated by the formulas. However, it is obtained in advance by experiments,
Calculating proportional coefficient k in the equation mentioned above is stored in the memory, the proportionality factor k ₂₅ at 25 ° C. in the formulas corresponding thereto, the temperature coefficient alpha, the equations described above with reference to tensile stress u acting on the wire 4 Then, the result is output to the display unit 58.

Also in the case of this embodiment, in the computer 56, Δt _ub is obtained by an equation in advance in a state where no stress acts on the wire 4, and this is stored in the memory, and Δt = t ₂ −t ₁ is obtained when the stress is measured. It is the same as in the case of the conventional example that Δt _ua is obtained by the equation when it is sent from the time measuring unit 55, and finally the axial tensile stress u acting on the wire 4 is calculated by the equation. ..

As described above, according to this embodiment,
The ultrasonic wave transducer 10 shown in FIG. 2 in which the transducer 1 on the transmission side, the transducer 2 on the reception side, and the temperature sensor 59 are integrated is held by hand and brought into contact with the side surface of the wire 4, and Since the tensile stress acting on the wire 4 can be easily measured and the propagation velocity of the surface wave is half or less than that of the longitudinal wave,
If the propagation time is long and the time measurement resolution is the same, the resolution of stress measurement is improved as compared with the case of measuring bolt axial force using longitudinal ultrasonic waves.

[0038]

As described above, according to the present invention,
Since surface waves are used for stress measurement, it is possible to easily measure the stress acting on these by using ultrasonic waves by bringing the ultrasonic transducer into contact with the side surface of the measurement object such as a wire. Since the wave propagation speed is half or less than that of longitudinal ultrasonic waves, the stress measurement resolution can be improved if the time measurement resolution is the same. Therefore, it is possible to provide an unprecedented excellent stress measuring method and apparatus capable of easily and accurately measuring the tensile stress of a wire or the like using ultrasonic waves.

The stress measuring method and apparatus according to the present invention are used to measure the tension of a thin rod made of a material such as metal, resin, or other ultrasonic wave that has been difficult to measure stress by ultrasonic waves. Specifically, it can be applied to a very wide range such as the tension of spokes of motorcycles and bicycles, the tension measurement of overhead wires and overhead wires, the tension measurement of racket guts, the tension measurement of wires used in cranes and the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram for explaining the configuration of an ultrasonic transducer including the transmitter transducer and the receiver transducer shown in FIG.

FIG. 3 is a diagram for explaining operating characteristics of ultrasonic waves at a boundary surface between substances X and Y.

FIG. 4 is a block diagram showing a configuration of a conventional stress measuring device used for measuring bolt axial force and the like.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitting side ultrasonic transducer 1A Transmitting side resin part 1B Transmitting side piezoelectric element 2 Receiving side ultrasonic transducer 2A Receiving side resin part 2B Receiving side piezoelectric element 3 Frame 51 Pulser circuit as pulse generating means 55 Time measuring part 56 Computer as computing means 59 Temperature sensor

Claims (2)

[Claims] 1. A longitudinal ultrasonic wave is output from a piezoelectric element forming a transmitting-side ultrasonic transducer to a side surface of an object to be measured through a resin portion at a predetermined incident angle of a critical angle or more, and the resin portion and the object to be measured. The surface wave is generated by converting the propagation mode of the ultrasonic wave at the boundary surface with the object, and the surface wave is propagated in the axial direction along the surface of the side surface of the measurement target, and then the propagation direction of the surface wave is further forward. Longitudinal ultrasonic waves are reconverted by changing the propagation mode of ultrasonic waves at the boundary surface between the resin part and the measurement object that make up the receiving ultrasonic transducers arranged at a predetermined distance from the transmitting ultrasonic transducers. The ultrasonic wave is propagated from the time when the piezoelectric element on the transmission side outputs the longitudinal wave ultrasonic wave to the time when the piezoelectric element on the reception side receives the longitudinal wave ultrasonic wave. Time is measured and this measured ultrasonic wave From the propagation time, the time it takes for the ultrasonic wave to propagate in the known electric circuit and the time for the ultrasonic wave to propagate in the resin portion that has been temperature-corrected based on the propagation time of the ultrasonic wave at a known reference temperature and its temperature characteristics. Obtain the propagation time of the surface wave by subtracting the total time, determine the propagation time of the surface wave for each case when stress does not act on the measurement symmetric object and stress acts by repeating such a procedure, A stress measuring method, characterized in that the stress in the axial direction of the object to be measured is calculated by multiplying the difference between the two propagation times by a predetermined proportional coefficient which has been temperature-corrected by a temperature coefficient previously obtained by an experiment or the like. 2. A pulse generating means for receiving an ultrasonic transducer driving pulse upon receiving a time measurement start signal, a transmission side ultrasonic transducer for electroacoustically converting the pulse from this pulse generating means and outputting it as an ultrasonic wave, The ultrasonic transducer on the receiving side that is provided corresponding to the ultrasonic transducer on the transmitting side and receives the ultrasonic wave and converts it into a pulse signal, and the time from the output of the time measurement start signal to the input of the pulse signal while inputting this pulse signal For measuring the stress, a calculation means for calculating a stress acting on the measurement object by performing a predetermined calculation upon receiving an output signal from the time measurement portion, and sending a signal according to the detected temperature to the calculation means. In a stress measuring device equipped with a temperature sensor, both ultrasonic transducers include a resin portion and the resin portion. When a surface wave is generated at the boundary surface between the resin part and the object to be measured, the angle of the normal line to the axis orthogonal to the bottom surface of the resin part Each of the ultrasonic transducers is provided with the temperature sensor, and the bottom surface of each resin portion is located on the same plane. As described above, the stress measuring device is characterized in that the piezoelectric elements are arranged at a fixed distance and the normals of the respective piezoelectric elements intersect at one point, and are integrated by a frame.