JP6167983B2 - Ultrasonic fatigue tester and ultrasonic fatigue test method - Google Patents

Description

  The present invention relates to an ultrasonic fatigue tester and an ultrasonic fatigue test method for performing a fatigue test by resonating a test piece with ultrasonic waves.

  Conventionally, an ultrasonic fatigue test is known in which a test piece is vibrated using ultrasonic waves to evaluate the fatigue life of a metal material or the like. In such an ultrasonic fatigue test, for example, a stress is repeatedly applied to the test piece by causing the test piece to resonate with a 20 kHz sine wave vibration.

  On the other hand, in the ultrasonic fatigue test, since a high frequency repeated load is applied to the test piece, the temperature rise of the test piece due to internal heat generation of the material becomes a problem. For this reason, an ultrasonic fatigue testing machine has been proposed in which the temperature near the test piece is measured during the test, and when the temperature exceeds a predetermined value, liquid nitrogen is sprayed to cool the test piece (patent) Reference 1).

  Moreover, in order to suppress the internal heat generation of the test piece, an ultrasonic fatigue testing machine that performs so-called intermittent operation in which vibration and suspension of applying ultrasonic vibration to the test piece are periodically repeated has been proposed (see Patent Document 2). ).

Japanese Utility Model Publication No. 62-128350 JP 2007-17288 A

  By the way, when performing intermittent operation in the ultrasonic fatigue test, the test piece is subjected to the same number of vibrations in a short time while suppressing the temperature rise of the test piece to be lower than the allowable range according to the material. Therefore, it is necessary to appropriately adjust the vibration time for applying the ultrasonic vibration to the test piece and the pause time for temporarily stopping the vibration for cooling the test piece.

  On the other hand, the amount of heat generated inside the test piece due to ultrasonic vibration varies due to the difference in stress load that vibrates the test piece. Moreover, even if the same stress load is applied to the test piece, the amount of heat generated inside the test piece varies depending on differences in the material and surface treatment of the test piece. Furthermore, in order to suppress the temperature rise of the test piece, when the intermittent operation and cooling by blowing cooling air are combined, the cooling rate of the test piece depends on the direction of cooling air blowing to the test piece and the temperature of the cooling air. fluctuate.

  The ultrasonic fatigue tester described in Patent Document 1 measures the temperature of the test piece, and the temperature of the test piece measures the surface temperature of the test piece, and the temperature inside the test piece. Is not necessarily measured. For this reason, even if the surface temperature of the test piece is lowered, the temperature inside the test piece may still be high.

  Furthermore, in the conventional tests using this type of ultrasonic fatigue tester, intermittent operation is performed according to the period of the excitation time and the downtime determined by the operator through trial and error. The operation for obtaining the optimal timing for stopping the vibration is troublesome for the operator. In addition, the timing for starting and stopping excitation determined by an operator may not always be the optimum timing. The optimum timing here means that the test piece is heated so that the total test time becomes the shortest when the same number of vibrations are applied to the test piece while keeping the heat generation of the test piece lower than the allowable temperature rise in the fatigue test. A state in which time and rest time are set. If the vibration cannot be started and stopped at the optimal timing, the fatigue test itself may fail.

  In addition, the internal temperature of the test piece was substantially measured by estimating the calorific value of the test piece from the elongation of the test piece during the fatigue test by intermittent operation, and whether or not the measured value exceeded the set temperature threshold A method of adjusting the timing of vibration start and vibration stop by using the above method is also conceivable. However, in this case, the vibration time and the pause time may vary due to measurement errors. Furthermore, when a vibration stop signal is given to the drive system due to a time delay from the signal input from the measurement system to the output of the control signal to the drive system that generates ultrasonic waves, for example, the test piece is excited. In the case of a material that generates heat more rapidly, the internal temperature of the test piece may already exceed the threshold value, and the vibration cannot be stopped at the optimum timing.

  As described above, in this type of ultrasonic fatigue testing machine, in consideration of the temperature inside the test piece under test, which varies depending on the type of test piece and the test content, the excitation time and pause time for intermittent operation in advance. It was difficult to set properly.

  The present invention has been made to solve the above-described problems, and provides an ultrasonic fatigue testing machine capable of appropriately setting the excitation time and the downtime in intermittent operation before the test is executed. Objective.

  According to the first aspect of the present invention, there is provided an oscillator that outputs an electric signal for generating a high frequency, an ultrasonic vibrator that vibrates in response to the electric signal from the oscillator, a test piece attached to a tip, and the ultrasonic vibration A horn that transmits ultrasonic vibrations from a child to the test piece, and a free end of the test piece that is opposite to an end fixed to the horn; An ultrasonic fatigue testing machine comprising a displacement meter for measurement and a control unit for controlling an output signal from the oscillator, and performing a fatigue test by intermittent operation, wherein the control unit holds the test piece for a predetermined time. Is obtained in a preliminary test in which the operation of stopping the vibration is performed at least once after the vibration is performed, and the temperature of the test piece after the vibration is stopped and when the test piece is vibrated. A storage unit for storing temporal changes; A temperature range setting unit for setting a temperature range allowed as a variation in the temperature of the test piece when the test piece is being vibrated, and a variation in the temperature of the test piece is set in the temperature range setting unit. A time estimation unit that estimates the excitation time and the rest time in the intermittent operation that becomes the temperature range based on the temporal change of the temperature of the test piece stored in the storage unit, and is estimated by the time estimation unit The start and stop of signal output from the oscillator are controlled by the excitation time and pause time.

  According to a second aspect of the present invention, in the first aspect of the invention, the storage unit obtains a change over time of the temperature of the test piece, which is obtained by using temperature measurement data and an equation representing a heat balance. Are stored as relational expressions, and the time estimation unit estimates the excitation time and the downtime in the intermittent operation using the relational expressions.

  According to a third aspect of the present invention, in the first aspect of the present invention, the storage unit is obtained by using temperature measurement data and an equation that assumes that the temperature of the test piece increases monotonically with an excitation time. A heat generation straight line representing a temporal change in the temperature of the test piece is stored as a relational expression, and the time estimation unit estimates an excitation time in intermittent operation using the relational expression.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the end face of the test piece is opposite to the end fixed to the horn. A displacement meter disposed at a position separated by a predetermined distance and measuring the distance to the end face of the test piece, wherein the control unit is configured to use a measurement value measured by the displacement meter as a result of ultrasonic vibration. And a temperature conversion unit for converting the temperature into the temperature of the test piece due to heat generation.

  According to a fifth aspect of the present invention, there is provided an oscillator that outputs an electric signal for generating a high frequency, an ultrasonic vibrator that vibrates in response to the electric signal from the oscillator, a test piece attached to a tip, and the ultrasonic vibration A horn that transmits ultrasonic vibrations from a child to the test piece, and a free end of the test piece that is opposite to an end fixed to the horn; In an ultrasonic material testing machine comprising a displacement meter for measurement and a control unit for controlling an output signal from the oscillator, an ultrasonic fatigue test method for performing a fatigue test by intermittent operation, the test piece being a predetermined test piece A preliminary test step of performing at least one operation of stopping the vibration after being vibrated for a period of time, a storage step for storing temporal changes in the temperature of the test piece acquired in the preliminary test step, and the test piece Vibrated A temperature range setting step for setting a temperature range allowed as a variation in the temperature of the test piece when, and in the temperature range set in the temperature range setting step, the excitation time and the pause time in intermittent operation, A time estimation step for estimating based on a temporal change in the temperature of the test piece stored in the storage step, and a time for setting the excitation time and the downtime estimated in the time estimation step as fatigue test conditions by intermittent operation It includes a setting step, and a test execution step for executing a fatigue test by intermittent operation based on the vibration time and the rest time set in the time setting step.

  According to the first and fifth aspects of the present invention, the temporal change in the temperature of the test piece obtained by the preliminary test is stored, and the excitation in the intermittent operation is performed based on the temporal change in the temperature of the test piece. Since the time and the pause time are estimated, it is possible to appropriately set the excitation time and the pause time before executing the test. Therefore, it is possible to appropriately execute the ultrasonic fatigue test.

  According to the second aspect of the present invention, it is possible to appropriately set the excitation time and the pause time before executing the test by the relational expression stored in the storage unit.

  According to the invention described in claim 3, it is possible to set the excitation time appropriately even when testing a material in which the test piece temperature changes linearly by the relational expression stored in the storage unit. It becomes.

  According to the invention described in claim 4, since the temperature conversion unit that converts the measured value of the displacement meter that measures the distance to the end face of the test piece into the temperature of the test piece is provided, the temperature measurement of the test piece by the displacement meter is performed. In addition, it is possible to estimate the excitation time and the downtime in intermittent operation based on the temporal change in the temperature of the test piece. Therefore, the ultrasonic fatigue test can be executed more appropriately.

It is a schematic diagram showing the main composition of the ultrasonic fatigue testing machine concerning this invention. It is a graph which shows an example of the measurement result of the end face gap d during the fatigue test by intermittent operation. It is a flowchart which shows the procedure of a preliminary test. It is a flowchart which shows the procedure of the intermittent operation in a preliminary test. It is a graph which shows the cooling curve C in the downtime b. It is a graph which shows the exothermic curve H1 in the vibration time a. It is a graph which shows exothermic straight line H2 in case test piece temperature changes monotonously in vibration time a. It is a flowchart which shows the procedure of the fatigue test by the ultrasonic fatigue testing machine based on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a main configuration of an ultrasonic fatigue testing machine according to the present invention. FIG. 2 is a graph showing an example of a measurement result of the end face gap d during a fatigue test by intermittent operation. The vertical axis of the graph is the measured value (μm) of the end face gap d, and the horizontal axis is time (seconds).

  This ultrasonic fatigue tester performs a fatigue test by resonating the test piece S with ultrasonic waves. The ultrasonic generator 10, the displacement measuring unit 20, and the overall operation of this ultrasonic fatigue tester are performed. It is comprised from the control part 30 to control.

  The ultrasonic generator 10 includes a vibrating unit 13 including an ultrasonic transducer 11 and a horn 12, and an oscillator 15 that generates a signal for vibrating the ultrasonic transducer 11. The oscillator 15 creates an electrical signal based on the test frequency set in the control unit 30. The ultrasonic transducer 11 is driven by the electrical signal output from the oscillator 15 to generate ultrasonic vibration. The ultrasonic vibration is amplified by the horn 12 and transmitted to the test piece S attached to the tip of the horn 12. That is, when the ultrasonic vibrator 11 is vibrated, a stress is repeatedly applied to the test piece S fixed to the tip of the horn 12.

  The displacement measuring unit 20 measures the displacement of the test piece S connected to the tip of the horn 12, and converts the detected value of the displacement meter 21 from an analog signal to a digital signal and transmits it to the control unit 30. And a container 22. The displacement meter 21 is disposed at a position away from the end surface on the free end side of the test piece S on the side opposite to the side fixed to the horn 12 by a predetermined distance. The displacement meter 21 is an eddy current displacement meter that measures the distance to the end surface of the test piece S in a non-contact manner. The displacement meter 21 may be a non-contact displacement meter of another principle such as a laser displacement meter. In this specification, the distance between the displacement meter 21 measured by the displacement meter 21 and the end surface of the test piece S is referred to as an end surface gap d.

  The value of the end face gap d measured by the displacement meter 21 is input to the control unit 30 via the converter 22. Displacement data (see FIG. 2) indicating the change in the end face gap d is displayed on the display unit 37 as necessary. Note that the amount of change in the end face gap d is also the amount of displacement of the tip (end face) of the test piece S.

  The control unit 30 is configured by a computer including a storage device such as a RAM and a ROM that can store programs and various data, and an arithmetic device such as a CPU. Connected to the control unit 30 are an input unit 36 for accepting an operation by the operator such as a change in test conditions, and a display unit 37 for displaying the test conditions and the displacement of the test piece S under test. The control unit 30 controls on / off of signal output from the oscillator 15 to the ultrasonic transducer 11 based on the set test conditions. Moreover, the control part 30 is provided with the temperature conversion part 31, the temperature range setting part 32, the time estimation part 33, the time setting part 34, and the memory | storage part 35 as main functional structures.

  The temperature converter 31 converts displacement data (see FIG. 2) indicating the displacement of the end face gap d of the test piece S into temperature data of the test piece S. In the temperature conversion unit 31, when the displacement of the end face gap d of the test piece S is converted into the internal temperature of the test piece S, a linear expansion coefficient already known for each material is used. The linear expansion coefficient is a rate of change in elongation per unit length due to a temperature increase of 1 ° C. Therefore, the change amount of the internal temperature of the test piece S can be calculated from the change amount of the end face gap d measured by the displacement meter 21 using the length of the test piece S and the linear expansion coefficient, and the end face gap of the test piece S can be calculated. The displacement of d can be converted into a change in the internal temperature of the test piece S. In addition, the value of the length of the test piece S used for calculation of the internal temperature of the test piece S is determined according to the shape of the test piece S and the length of the region where stress is concentrated. Moreover, in this temperature conversion part 31, the internal temperature of the test piece S calculated | required by the calculation using the variation | change_quantity of the end surface gap d equivalent to the displacement amount of the end surface of the test piece S, and a linear expansion coefficient, and its change are required. In response to the value, a numerical value and a graph are displayed on the display unit 37. Here, the end face gap d at the time of conversion into temperature refers to an average end face gap when there is no fluctuation due to ultrasonic vibration.

  The temperature range setting unit 32 includes an upper limit temperature that can be accepted as an internal temperature of the test piece S in a fatigue test in which a repeated load is applied, and a lower limit temperature that serves as a standard for resuming the vibration after the vibration is stopped, that is, The allowable temperature range is set as the fluctuation of the internal temperature. The temperature range is set by the operator via the input unit 36.

  In the temperature range set by the temperature range setting unit 32, the time estimation unit 33 converts the excitation time a and the pause time b in intermittent operation into temporal changes in the internal temperature of the test piece S stored in the storage unit 35. Estimate based on. That is, after starting the excitation by the ultrasonic wave, the time to reach the upper limit temperature of the test piece temperature which is a reference for stopping the vibration (the vibration time a), and after stopping the vibration by the ultrasonic wave, The time (rest time b) until the lower limit temperature of the test piece temperature, which is a reference for resuming excitation, is estimated. In addition, the temporal change of the internal temperature of the test piece S is the relationship between the time from the start of vibration obtained based on the temperature data acquired by the preliminary test and the temperature change of the test piece S, and from the stop of the vibration. The relationship between time and the temperature change of the test piece S is represented.

  The time setting unit 34 sets the vibration time a and the rest time b estimated by the time estimation unit 33 as test conditions in the fatigue test, and sets the total vibration time for realizing the target number of times to be applied to the test piece S. To do. From this total excitation time, the number of sets that repeats the start and stop of vibration is derived.

  The storage unit 35 stores displacement measurement data input to the control unit 30 via the displacement meter 21 and the converter 22 during the test, and changes with time in the internal temperature of the test piece S acquired by a preliminary test described later. Remember.

  When the fatigue test by intermittent operation is executed by the ultrasonic fatigue tester having the above-described configuration, the measured value of the end face gap d detected by the displacement meter 21 is increased in the internal temperature of the test piece S as shown in FIG. Accordingly, during the excitation time a, the end face gap d gradually changes (becomes shorter). On the other hand, during the downtime b, as the internal temperature of the test piece S decreases, the elongation due to heat generation of the test piece S during vibration tends to return to the original value. It changes in a direction that becomes larger (longer) than the value of the end face gap d at the time. When the test piece S is vibrated, the measurement value of the end face gap d measured by the displacement meter 21 becomes a continuous waveform that fluctuates with a large amplitude. When the vibration is stopped, the measurement value of the end face gap d is It becomes a continuous waveform that fluctuates with a small amplitude. In a fatigue test in which the vibration time a and the rest time b are repeated, a continuous waveform having a large amplitude and a small amplitude are centered on a reference end surface gap di that is the distance between the end surface of the specimen S before the test and the displacement meter 21. A continuous waveform appears repeatedly. In FIG. 2, since the period of the waveform indicating the measured value of the end face gap d is extremely short with respect to the horizontal scale, the outer shape (envelope) of the continuous waveform is shown.

  Next, a procedure for executing a fatigue test by intermittent operation using such an ultrasonic fatigue tester will be described. FIG. 3 is a flowchart showing the procedure of the preliminary test. FIG. 4 is a flowchart showing a procedure of intermittent operation in the preliminary test. FIG. 5 is a graph showing a cooling curve C of the test piece temperature during the downtime b, and FIG. 6 is a graph showing an exothermic curve H1 of the test piece temperature during the vibration time a. 5 and 6, the vertical axis represents the test piece temperature (internal temperature of the test piece S), and the horizontal axis represents time (seconds). 5 and 6 also show the outline of the continuous waveform because the period of the waveform is extremely short with respect to the horizontal scale, as in FIG.

  First, in this ultrasonic fatigue tester, a preliminary test is performed before the fatigue test is performed. A test piece S is attached to the horn 12, and a reference end face gap di serving as a reference for obtaining the amount of change in the end face gap d is measured and determined before starting vibration (step S11).

  Next, intermittent operation in the preliminary test is executed (step S12). In the preliminary test, arbitrary times are set in advance as the vibration time a and the pause time b, and the test piece S is vibrated (step S21). The measured value of the end face gap d detected by the displacement meter 21 during vibration is converted into the internal temperature of the test piece S by the action of the temperature conversion unit 31 (step S22).

  When the set excitation time a elapses (step S23), the excitation is stopped (step S24). When the pause time b has elapsed (step S25) and the required number of times has not been reached (step S26), the operations of steps S21 to S25 are repeatedly executed. In the preliminary test, at least vibration and stop may be performed once (one set). Here, one set means that the vibration is started and stopped once.

  Next, the relationship between the vibration time a acquired by the preliminary test and the change in the internal temperature of the test piece S, and the relationship between the pause time b after stopping the vibration and the change in the internal temperature of the test piece S are as follows. It is obtained and stored in the storage unit 35 (step S13: storage step). Then, the preliminary test is completed.

  Once the test piece S is vibrated, the value of the end face gap d fluctuates. Therefore, the internal temperature of the test piece S calculated based on the measured value of the displacement meter 21 is a continuous waveform with a short cycle. However, since the temperature of the actual test piece does not change in a short cycle in view of thermal inertia, it is appropriate to consider the following when calculating the temperature. The relationship between the vibration time a acquired by the preliminary test and the change in the internal temperature of the test piece S, and the relationship between the pause time b after stopping the vibration and the change in the internal temperature of the test piece S are shown in FIG. And as shown in FIG. 7, it can represent with the approximated curve of the measurement data of the temperature which appears as a continuation of a waveform with a short period.

  The graph shown in FIG. 5 shows a case where the test piece temperature shows a curvilinear temperature change during the downtime b. When the test piece S is cooled and the internal temperature of the test piece S decreases to the outside air temperature, the estimated cooling curve C is estimated using, for example, the following equation (1) representing the heat balance. The

C _p V is the heat capacity, T is the test piece temperature, t is the elapsed time, T ₀ is the outside air cooling temperature, h is the test piece-outside air transfer coefficient, and A is the test piece surface area. From the temperature measurement data obtained in the preliminary test, the coefficient C _p V / hA can be obtained using the least square method. Thus, the cooling curve C is stored in the storage unit 35 as a relational expression representing the relationship between the downtime b and the change in the internal temperature of the test piece S. Using the relational expression stored in the storage unit 35, it is possible to calculate the time from when the vibration is stopped until the lower limit of the test piece temperature, which is a reference for resuming the vibration, that is, the rest time b is calculated. .

  The graph shown in FIG. 6 shows a case where the test piece temperature shows a curvilinear temperature change during the excitation time a. As in the case of the cooling curve C shown in FIG. 5, the heat generation curve H <b> 1 is estimated using (2) below, which represents the heat balance, for example.

C _p V is the heat capacity, T is the test piece temperature, t is the elapsed time, T ₁ is the outside air cooling temperature, T ₂ is the internal heat generation temperature, h ₁ is the test piece-outside air transfer coefficient, h ₂ is the test piece internal transfer coefficient, A is the specimen surface area. The coefficient C _p V / h ₂ A can be obtained using the least square method from the temperature measurement data obtained in the preliminary test. The coefficient C _p V ₁ / h ₁ A is the same as C _p V / hA obtained from the cooling curve C. Thus, the heat generation curve H1 is stored in the storage unit 35 as a relational expression representing the relationship between the vibration time a and the change in the internal temperature of the test piece S. Therefore, it is possible to calculate the time required to reach the upper limit value of the test piece temperature serving as a reference for stopping the vibration, that is, the vibration time a.

In addition, the outside air cooling temperatures T ₀ and T ₁ in the expressions (1) and (2) are temperatures around the test piece S when the preliminary test is performed, for example, room temperature, and a case where the outside temperature is constant is assumed. Yes.

  5 and 6 described above show a case where the internal temperature of the test piece S changes in a curve. However, depending on the material, it is proportional to the relationship between the increase in the internal temperature of the test piece S due to vibration and time. Some relationships hold. The graph shown in FIG. 7 is a graph for explaining the relational expression of the temperature change when the internal temperature of the test piece S shows a linear temperature change during the vibration time a. In this graph, the vertical axis represents the test piece temperature, and the horizontal axis represents time (milliseconds). Assuming that the internal temperature due to the heat generation of the test piece S monotonously increases with the vibration time a, the relationship between the vibration time a and the change in the internal temperature of the test piece S is estimated using the following equation (3).

T is the test piece temperature, k (σ) is the temperature rise coefficient, t is the elapsed time, and T ₀ is the initial test piece temperature. The coefficient k can be obtained from the temperature measurement data obtained in the preliminary test. Thereby, the heating straight line H2 is stored in the storage unit 35 as a relational expression representing the relationship between the vibration time a and the change in the internal temperature of the test piece S. Since the temperature rise coefficient k (σ) varies depending on the test stress σ, the range is obtained by acquiring one set of temperature data for each of the lowest stress that causes the temperature rise and the highest stress to be tested. The temperature rise coefficient (corresponding to the proportionality constant) of the stress inside can be interpolated.

  In this embodiment, the relational expression representing the temporal change in the internal temperature of the test piece S based on the measurement data obtained by the preliminary test is derived using the formulas (1) to (3). The relational expression may be obtained using a method for deriving another approximate expression. In the above-described example, the relational expression is obtained using the measurement data of the temperature for one set. However, the relational expression may be obtained using the average value of the measurement data of the temperature for a plurality of sets.

  FIG. 8 is a flowchart showing a procedure of a fatigue test by the ultrasonic fatigue tester according to the present invention.

  First, the test piece S is attached to the horn 12, and a reference end face gap di serving as a reference for obtaining the amount of change in the end face gap d is measured and determined before starting vibration (step S31). Next, a temperature range allowed as a variation in the internal temperature of the test piece S, that is, an upper limit temperature allowable as an internal temperature of the test piece S in a fatigue test in which a repeated load is applied, and the vibration is resumed after the vibration is stopped. A reference lower limit temperature is set in the temperature range setting unit 32 (step S32: temperature range setting step).

  Using the relational expression in which the value of each coefficient is determined by the temperature measurement data obtained by the preliminary test described above, the excitation time a and the rest time b within the set temperature range are estimated by the action of the time estimation unit 33. (Step S33: time estimation step). Each estimated time is set in the time setting unit 34 (step S34: time setting step). Thereafter, a fatigue test by intermittent operation is performed (step S35: test execution step). The fatigue test by intermittent operation is performed until the total of the vibration times a so far reaches the target total vibration time.

  As described above, in the above-described embodiment, since the relational expression obtained from the temperature measurement data obtained by the preliminary test is stored in the storage unit 35, when performing the fatigue test, the temperature range is set before the test is executed. Thus, it is possible to call up the relational expression and automatically set an appropriate excitation time a and pause time b. The preliminary test only needs to be performed once for each type and size of the material to be tested, and a relational expression may be stored in association with the type and size of the material. Thereby, in the fatigue test by intermittent operation, it is possible to set an appropriate vibration time a and rest time b according to the type and size of the material before the test is executed.

  In the above-described embodiment, the control unit 30 includes the temperature conversion unit 31 as a functional configuration, and the configuration in which the measurement value of the displacement meter 21 is converted into the temperature of the test piece S is adopted. However, the configuration is not limited thereto. The temperature data indicating the “temporal change in the temperature of the test piece” in the present invention may be collected by, for example, a temperature measuring device using a thermocouple or the like.

  Furthermore, in the ultrasonic fatigue testing machine according to the present invention, it is possible to determine an appropriate excitation time a and rest time b according to the type and size of the material before the test is executed, and start the excitation from the control unit 30. And the output of the signal for instructing to stop the vibration can be controlled without delaying the temperature rise due to the rapid heat generation of the test piece S during vibration. Therefore, it is possible to prevent the internal temperature of the test piece S from exceeding the allowable upper limit temperature during the test and to perform the fatigue test reliably.

DESCRIPTION OF SYMBOLS 10 Ultrasonic generator 11 Ultrasonic vibrator 12 Horn 13 Vibrating part 15 Oscillator 20 Displacement measurement part 21 Displacement meter 22 Converter 30 Control part 31 Temperature conversion part 32 Temperature range setting part 33 Time estimation part 34 Time setting part 35 Storage part 36 Input section 37 Display section S Test piece

Claims (5)

An oscillator that outputs an electrical signal that generates a high frequency; and
An ultrasonic vibrator that vibrates in response to an electrical signal from the oscillator;
A test piece is attached to the tip, and a horn that transmits ultrasonic vibration from the ultrasonic vibrator to the test piece;
A displacement meter disposed on the free end side of the test piece opposite to the end fixed to the horn, and measuring the displacement of the end face of the test piece;
A control unit for controlling an output signal from the oscillator;
An ultrasonic fatigue tester that performs a fatigue test by intermittent operation,
The controller is
Acquired in a preliminary test in which the test piece is vibrated at least once after the test piece is vibrated for a predetermined time, and when the test piece is vibrated and after the vibration is stopped A storage unit for storing temporal changes in the temperature of the test piece;
A temperature range setting unit for setting a temperature range allowed as a variation in temperature of the test piece when the test piece is being vibrated;
Based on the temporal change in the temperature of the test piece stored in the storage unit, the vibration time and the pause time in intermittent operation in which the temperature variation of the test piece becomes the temperature range set in the temperature range setting unit And a time estimation unit for estimating
An ultrasonic fatigue testing machine, wherein start and stop of signal output from the oscillator are controlled by an excitation time and a pause time estimated by the time estimation unit. In the ultrasonic fatigue testing machine according to claim 1,
The storage unit stores, as a relational expression, a cooling curve and a heat generation curve representing a temporal change in the temperature of the test piece obtained using temperature measurement data and an equation representing a heat balance,
The said time estimation part is an ultrasonic fatigue testing machine which estimates the excitation time and rest time in intermittent operation using the said relational expression. In the ultrasonic fatigue testing machine according to claim 1,
The storage unit uses a temperature measurement data and an equation that assumes that the temperature of the test piece monotonously increases with an excitation time, and uses a heat generation straight line representing a temporal change in the temperature of the test piece as a relational expression. Remember,
The said time estimation part is an ultrasonic fatigue testing machine which estimates the vibration time in intermittent operation using the said relational expression. In the ultrasonic fatigue testing machine according to any one of claims 1 to 3,
The said control part is an ultrasonic fatigue testing machine further provided with the temperature conversion part which converts the measured value which the said displacement meter measured into the temperature of the said test piece by the heat_generation | fever of the material resulting from ultrasonic vibration. An oscillator that outputs an electric signal that generates a high frequency, an ultrasonic vibrator that vibrates in response to the electric signal from the oscillator, a test piece is attached to the tip, and the ultrasonic vibration from the ultrasonic vibrator is tested in the test A horn that transmits to the piece, a displacement meter that is disposed on the free end side of the test piece that is opposite to the end fixed to the horn, and that measures the displacement of the end face of the test piece; In an ultrasonic material testing machine comprising a control unit that controls the output signal of
A preliminary test step of performing at least one operation of stopping the excitation after the test piece is vibrated for a predetermined time;
A storage step of storing a temporal change in the temperature of the test piece acquired in the preliminary test step;
A temperature range setting step for setting a temperature range allowed as a variation in temperature of the test piece when the test piece is being vibrated;
In the temperature range set in the temperature range setting step, a time estimation step of estimating the excitation time and the pause time in intermittent operation based on the temporal change of the temperature of the test piece stored in the storage step;
A time setting step for setting the excitation time and the rest time estimated in the time estimation step as fatigue test conditions by intermittent operation;
A test execution step of performing a fatigue test by intermittent operation according to the vibration time and the downtime set in the time setting step;
An ultrasonic fatigue test method comprising:

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