JPS5831539B2 - Tsukarekiyoudonosokuteisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a fatigue strength measuring device, in particular, a test piece that has an appropriate elastic force, and measures how much fatigue strength the test piece has against repeated bending stress, etc. This relates to a measuring device.

Conventional test pieces, such as metal wires and thin plates, which have a suitable elastic force, have a certain elasticity even when they are alone or when other weighted objects are combined with them. It is possible to perform so-called free vibration in relation to
Moreover, depending on the vibration, repeated bending stress (in the case of bending vibration) or torsional stress (in the case of torsional vibration) is generated in the test piece, so it is necessary to maintain the free vibration under some suitable control system. For example, this makes it possible to generate repetitive stress of a constant value on the test piece very easily and regularly, but the present invention further improves and develops this, and in particular, the above-mentioned method. This is a control system for maintaining free vibration, and is constructed so that it can exert the most effective and efficient vibration sustaining action on the test piece targeted by the device.

An example embodying the present invention will be described below.
In the figure, 1 is a test piece, for example, a long and thin metal wire or a thin strip-shaped metal plate.
A steel wire rod with a roughly oval cross section that is used as raw material for knitting needles for hand knitting machines is featured.

Reference numeral 2 denotes a weighted addition that constitutes a vibration system together with the test piece 1, and is made of a ferromagnetic material, for example, iron.

The weighted material 2 is firmly fixed to the lower end of the test piece 1 by inserting the test piece 1 into the insertion hole 3 provided at its center and operating the tightening screw 4.

Reference numeral 5 denotes a frame body of the measuring device, and a strong L-engraved metal fitting 6 is attached to the front surface of the frame body with a pair of mounting screws 7.

Reference numeral 8 denotes a relatively thick support plate which constitutes a test piece support device together with the L-carved metal fitting 6, and the upper thick portion 8a of this support plate 8 is fixed to the carved metal fitting 6 in a cantilevered manner. Because of this, the lower bent end portion 8b can be bent slightly, although it cannot be said that it is easy to bend.

This support plate 8 is provided with a vertically elongated groove 9 in which the upper end of the test piece 1 is inserted in its lower end portion 8b, and the test piece 1 inserted into the groove 9 is inserted into the groove 9. A clamping fastener 10 is fitted for a firm fixation within.

If this fastener 10 is replaced with another fastener 20 having the shape shown in FIGS. 3 and 4, for example, the test piece 1, such as a thin strip-shaped metal plate, can be attached to that plate. It can be firmly attached to the lower end of the support plate 8 according to the change in thickness.

As for the other weight additions 2, if one is selected that is suitable for the test piece 1 at that time, a wide range of measurements can be made.

In this embodiment, when the vibration system consisting of the test piece 1 and the weighted object 2 performs free vibration, the device that generates the assisting force necessary to maintain the free vibration is a Electromagnet SQ installed corresponding to weight addition 2
This electromagnet SQL is intermittently driven by the operation of the control device shown in the block diagram of the electrical circuit in FIG. 5 (FIG. 6 shows its operation waveform diagram).

That is, in the control device, the vibration system is approximately connected to the electromagnet S.
The electromagnet S
It drives the OL, and to further explain each circuit in detail, the DET shown on the left side of FIG. 5 is a detection circuit, and specifically, it is installed near the thickness change of the support plate 8, It is composed of a bridge type strain gauge SG for detecting the bending type of the part and an amplifier AMP1 for amplifying the output from the strain gauge SG.

In addition, although it is common to extract the output for DC unbalance from this strain gauge SG, stability and S/N
For the purpose of improving the ratio, it is also possible to extract the AC unbalanced amount as output using one type of AC chopper.

COM is a comparison circuit for comparing the magnitude of the detection output from the detection circuit DET with a reference level, and the amplifier AMP
2 and a diode D1 for storing the peak value of its output.
．． A half-wave rectifier circuit consisting of a capacitor C1, a comparator DEFI that compares the terminal voltage of this capacitor C1 with a reference level, a variable resistor VRI for setting this reference level, and a transistor TRI connected in parallel to the capacitor C1. It is composed of.

DRV is a drive circuit for driving an electromagnet SQL 7 for applying an auxiliary force that applies an auxiliary force to the vibration system including the test piece 1 to maintain its free vibration, and the output of the comparison circuit COM is It is composed of an amplifier AMP3 for amplifying the signal, a gate transistor TR2 connected in series between the output terminal of the amplifier AMP3 and the electromagnet SQL, and a transistor TR3 connected between the base of the transistor TR2 and the ground.

The bases of these transistors TR2 and TR3 are controlled by the output of a drive period setting circuit GTE to be described later, causing the transistor TR2 to perform a gate function to limit the drive period of the electromagnet SQL by the amplifier AMP3.

, the drive period setting circuit GTE includes a comparator DEF2 that compares the detection output from the detection circuit DET with a reference level set by a variable resistor VR2, a monostable multi-by break MM1 triggered by the comparison output, and a monostable multi-by break MM1 that is triggered by the comparison output. A monostable multivibrator MM2 triggered by the output and this multivibrator MM
2, a capacitor C2 for storing the peak value of the sawtooth signal from the oscillator ST, and a capacitor C2 for storing the peak value of the sawtooth signal from the oscillator ST. A transistor TR4 is inserted and connected between an oscillator ST and a capacitor C2 to synchronize with the output of the stable multi-by-break MM1, and two variable transistors whose terminal voltage is applied via an amplifier AMP4. Comparators DEF3 and D that compare the output of the oscillator ST with the reference level set by the resistors VR3 and VH2 and the variable resistors VR3 and VH2, respectively.
EF4 and both comparators DEF3. Monostable multi-bi break M triggered by respective comparison output of DEF4
M3. MM4 and both multi-by-break MM3. MM4
a flip-flop FF that is set and reset by each output, and a comparator DEF that compares the output of the oscillator ST with the reference level set by the variable resistor VR5.
5, and an amplifier AMP5 which amplifies the comparative output and energizes the alarm buzzer BL.

The output of the monostable multi-bibreak MM3 goes to the base of the transistor TR1 of the comparator circuit COM, and the output of the flip-flop FF goes to the base of the transistor TR of the drive circuit DRV.
The output of amplifier AMP5 to the base of transistor TR
3 bases respectively.

IND shown in the lower left of the fifth figure is a display device for counting and displaying the number of repeated vibrations of the vibration system,
A comparator DEF6 that compares the reference level set by the variable resistor VR6 and the detection output of the detection circuit DET, and a monostable multi-bi break M triggered by the output of the comparator DEF6.
M5 and an electromagnetic counter CNT to which the pie break output is supplied via an amplifier AMP6.

In the above configuration, for example, if the test piece 1 is mounted in the state shown in FIG. 1 and the vibration system consisting of the test piece 1 and the weighted object 2 is stopped in a hanging state, this will cause the strain to increase. No distortion signal is detected in the gauge SG, and therefore no signal is sent to the driving period setting circuit GTE.

Therefore, the electromagnet SQL is not driven.

Therefore, when measuring the fatigue strength of the test piece 1,
It is sufficient to press the vibration system in any one of the arrow directions in FIG. 1 and then suddenly release the pressure.

As a result, since the test piece 1 itself has an elastic force, the vibration system has a unique frequency, that is, a spring constant based on the elastic force held in the test piece 1, and a spring constant based on the elastic force held in the test piece 1. Free vibration begins with a natural frequency determined by the mass of the entire vibrating system.

At this time, although the support plate 8 that supported the vibration system is made of a relatively thick material that is difficult to bend, the support plate 8 is supported in a cantilever manner with respect to the frame 5. Therefore, a bending tendency is given in the same direction as the vibration direction, and as a result, a bending bundle is generated, albeit slightly.

Moreover, the support plate 8 is given the same tendency to bend to the right by, for example, a vibration system that vibrates to the right, and
Since a leftwardly vibrating oscillating system also imparts a leftward bending tendency, a bending bundle is generated at the same frequency as that inherent to the oscillating system.

Therefore, the strain generated in the portion of the support plate 8 near the thickness change due to the bending is a frequency specific to the vibration system and changes depending on the magnitude of the vibration amplitude.

That is, the repeated bending stress of the test piece 1 caused by the vibration of the vibration system is related to the magnitude of the vibration amplitude, and is also caused in relation to its period. The strain represents the change in the repeated bending stress of the test piece 1.

This distortion of the support plate 8 is immediately detected by the strain gauge SG as an electrical detection signal (see FIG. 6), and if the signal level is higher than that of the drive period setting circuit GT.
If the level is higher than the level required to operate E, the setting circuit GTE operates and the electromagnet SQL is driven.

That is, the detection signal ■ is detected by the comparator D of the drive period setting circuit GTE.
When input to EF2, it is compared with the reference level and a pulse signal [F] is generated for the detection signal ■ above a certain level.
is output.

This pulse signal [F] is a monostable multi-bibreak MM
It is converted into a pulse signal [F] via I, and a pulse signal 0 is obtained via the next monostable multi-by-break MM2.

These signals [F], [F], and (2) are all obtained once during one cycle of the detection signal (2).

Then, triggered by the signal 0, the sawtooth oscillator ST
A sawtooth wave signal [F] is output from.

Since the rising slope of this signal 0 is constant, the lower the interval of the pulse signal (2), that is, the repetition frequency of the detection signal (2), the higher the peak value of the signal 0 becomes.

The peak value of this sawtooth wave signal 0 is transferred to the capacitor C via the transistor TR4 which is opened and closed by the pulse signal [F].
2, and the voltage level is applied as a DC signal (2) to variable resistors VR3 and VH2, respectively, via an amplifier AMP4.

These variable resistors VR3 and VH2 are for dividing the peak value of the sawtooth wave signal 0, and the division voltage level set by these variable resistors VR3 and VH2, respectively, and the sawtooth wave signal [F] By comparing these, the comparative outputs ■ and (D are obtained, respectively.

These outputs ■ and ■ are monostable multi-by-break M
M3. The waveform is converted by MM4, and the pulse signal ■,
0, and is input to the set and reset trigger terminals of the flip-flop FF, respectively.

These pulse signals ■ and ■ represent the point in time when the sawtooth wave signal 0 and the DC level set by the respective variable resistors VR3 and VR4 match, and the sawtooth wave signal [F
] can be set at a specific point in one cycle.

Therefore, if the -cycle is set to 360 degrees, the angle can be specified, and in this example, the variable resistance vR3 is 18
The variable resistor VR4 is designed for 0° to 3600°, and the variable resistor VR4 is designed for 00° to 180°.

Therefore, as the repetition period of the sawtooth wave signal 0 becomes longer, the peak value of the signal 0 also becomes higher, but the variable resistors VR3 and VH2
Since the partial pressure level set by also increases, the signal 0
The set angle during one cycle does not change.

Further, a set output [phase] is obtained from the flip-flop FF triggered by these pulse signals (1) and (Q), and this output (2) is input to the base of the transistor TR2 for the gate of the drive circuit DRV, The above electromagnet SQL connected to its emitter is connected to the flip-flop F
It is possible to drive only while the set output [phase] from F is present.

This drive period is influenced by the voltage division level set by variable resistors VR3 and VH2.

Therefore, by setting the partial pressure level to an optimum value for maintaining free vibration of the vibration system, the driving period of the electromagnet SQL during the -cycle can be maintained constant even if the repetition frequency changes.

In this embodiment, this specific drive period is set for approximately a half cycle from just before the vibration system is farthest from the electromagnet SQL to just before it approaches the electromagnet SQL, thereby reducing the hysteresis, etc. of the electromagnet SQL. It is possible to generate the most effective auxiliary force under consideration, but the specific adjustment of variable resistance VR3°VH2 is
can be obtained very easily by experimentally manipulating it in various ways.

On the other hand, the detection signal (2) which is also input to the comparator circuit GCM is converted into a DC signal [F] corresponding to its peak value by the die hood D1 and capacitor C1 of the circuit COM.

The level of this DC signal (2) corresponds to the peak value of each cycle of the detection signal (2), and as the amplitude of the detection signal (2) increases, the level of this signal (2) also increases.

This DC signal [F] is compared with the reference DC level set by the moment setting variable resistor VRI by the comparator DEF 1, and a supplementary comparison output with respect to that level is output.
is obtained.

That is, an output corresponding to the level of the DC signal [F] that is insufficient with respect to the reference DC level is obtained.

Moreover, the DC signal (2) responds to a new detection signal (2) every time the pulse signal (2) from the driving period setting circuit GTE is added to the pace of the transistor TRI, that is, every cycle of the detection signal (2). Since the detection signal (2) is replaced by the level DC signal (2), a supplementary comparison output 0 is obtained that immediately responds to the level change of the detection signal (2).

As described above, the drive output 0 where the comparison output 0 from the comparison circuit COM is intermittent by the drive period setting circuit GTE is, for example, the preset variable resistor VR1.
If the strain DC signal (2) from the strain gauge SG is too small with respect to the reference value, a large output will be obtained, and if the strain signal is not too small, a small output will be obtained.

As a result, if a strong magnetic force is generated by the electromagnet SQL, the generated magnetic force will strongly attract the weighted object 2 in the vibrating system, thereby increasing the amplitude of the vibrating system as a whole.

Then, the distortion of the support plate 8 caused by the vibration also becomes
Naturally, it becomes larger, and a small output is now applied to the electromagnet SQL, thereby weakening the generated magnetic force.

By these control operations, when the vibration system continues to vibrate due to force, when the electromagnet SQL sequentially applies a supporting force corresponding to the attenuation of the vibration, the vibration system vibrates at a certain level, and the vibration system vibrates at a certain level. The strain of the support plate 8 is maintained at a substantially constant value, and the magnitude of this value is determined by the reference value of the variable resistor VRI.

The fact that the strain of the support plate 8 is maintained at a substantially constant value is that a bending stress of a substantially constant value is repeatedly generated in the test piece 1, thereby increasing the fatigue strength. can be measured.

Further, changing the magnitude of the strain value of the support plate 8, that is, changing the reference value of the variable resistor VRI, means changing the magnitude of the vibration amplitude of the vibration system. Large and small bending stresses can be repeatedly generated in the piece 1.

In this way, the test piece 1, which is subject to repeated bending stress, may undergo so-called fatigue failure when the bending stress value exceeds a certain value, and the number of repeated vibrations before this failure occurs is important. It becomes a material.

For this purpose, the electromagnetic counter CN of the display device IND
T is driven by supplying the detection output ■ via the comparator DEF6, the monostable multi-by-break MM5, and the amplifier AMP6, and performs counting display.

Sometimes, when the free vibration of the vibration system stops due to fatigue failure occurring in the test piece 1, etc., the level of the sawtooth wave signal 0 increases rapidly, and the level of the sawtooth wave signal 0 rises rapidly. When the level becomes higher than the reference level, the comparator DEF
5. A comparison output [F] is generated via the amplifier AMP5, energizes the alarm buzzer BL, and is input to the base of the transistor TR3 of the drive circuit DRV, shorting the base input to the gate transistor TR2. Then, the transistor TR2 is completely cut off.

As a result, electromagnet SQL is no longer driven.

By the way, if a large number of test specimens 1 are always combined with the same weighted material 2, it is possible to generate repeated bending stress at a constant frequency. It is also possible to change the time interval at which the fatigue occurs and measure how this changes the fatigue intensity.

That is, if the weight of the weight addition material 2 is increased or decreased as appropriate, in other words, if a large number of weight addition materials 2 with different weights are prepared and a suitable one of them is combined with the test piece 1, this results in Since the mass of the entire vibrating system changes, the frequency specific to the vibrating system can be easily changed as needed.

Furthermore, by combining the weight addition material 2 made of ferromagnetic material, even if the test piece 1 itself does not have ferromagnetism, it can easily provide a supporting force to the vibration system including the test piece 1. This makes it possible to easily measure test pieces made of, for example, synthetic resin materials and non-ferrous materials such as copper and aluminum.

Furthermore, since the target test piece 1 independently vibrates freely at an extremely high frequency, for example, if the frequency exceeds the response range of the measuring device, especially the electromagnetic counter CNT, etc. Even if there is, by appropriately combining the weighted material 2 with the test piece 1, it is possible to perform measurements while keeping the frequency of the entire vibration system including the test piece 1 low.

Therefore, a wide variety of test pieces can be measured.

In this example, the strain signal was not taken out directly from the test piece 1, but was taken out indirectly from the support plate 8 that supported the test piece 1, so the test piece 1 to be measured was There is no need to attach a strain gauge SG to each test piece 1 every time it is replaced, and the measurement can be easily and quickly performed.

Furthermore, in the circuit of this embodiment, a sawtooth wave oscillator ST is used in the drive period setting circuit GTE, and the drive period in one cycle of the vibration system is set using the sawtooth wave signal.
Even for vibration systems having different natural frequencies, it is possible to extremely easily set the most efficient drive period for each vibration system.

As explained above, the present invention is a device for measuring fatigue strength by performing so-called free vibration, and a control device for generating a supporting force necessary to maintain the free vibration.
In particular, it is equipped with a driving period setting circuit GTE that can apply an auxiliary force for an arbitrary specific period during one cycle of free vibration, and the driving period setting circuit GTE controls the electromagnet SQL for applying the auxiliary force to the test piece 1. The vibration system is driven so as to supplement the damped free vibrations of the vibration system, and the driving period is limited to the most effective period for supporting the vibration of the vibration system, and further,
Considering the hysteresis of the electromagnet SQL for applying the auxiliary force, we specified the drive start time and end time of the drive circuit DRV so that the auxiliary force is generated at the most timely timing.
Extremely efficient fatigue testing can be performed.

In particular, even when targeting various test pieces, the most efficient drive start time and end time of the electromagnet SQL can be determined independently according to the repetition frequency that differs for each test piece. It has extremely excellent practical effects, such as being able to be adjusted very easily using the two adjustment members VR3° and VH2.

[Brief explanation of drawings]

Figure 1 is an exploded perspective view of the main parts of this device, and Figure 2 is the same as Figure 1.
3 is an exploded perspective view of a main part showing a modified example of the test piece support device, and FIG. 4 is an enlarged sectional view taken along the line IV-
5 is a block diagram of an electric circuit such as a control device, FIG. 6 is an operation waveform diagram thereof, and FIG. 7 is an explanatory diagram of the operation. 1 is a test piece, 8 is a support plate as a test piece support device, SQ
L is an electromagnet for applying auxiliary force, DET is a detection circuit, COM
is a comparison circuit, DRV is a drive circuit, GTE is a drive period setting circuit, IND is a display device, and VH2 and VH2 are variable resistors as adjustment members.

Claims (1)

[Scope of Claims] 1. In order to measure how much fatigue strength the test piece 1 has against repeated bending stress, etc., using a test piece 1 having an appropriate elastic force, at least the test piece 1 A test piece support device 8 that supports a vibration system including 1 so that it can freely vibrate at a fixed frequency.
, an electromagnet SQL for applying a auxiliary force that applies a auxiliary force to the vibration system to maintain its free vibration, and a stress generated in the test piece 1 for the electromagnet SQL for applying the auxiliary force. a control device for generating an auxiliary force necessary to maintain a substantially constant value; and a display device IND for detecting the number of repeated vibrations of the vibration system, counting and displaying the number of vibrations. In the fatigue strength measuring device, the control device includes a detection circuit DET for detecting stress occurring in the test piece, and a comparison circuit COM for comparing the magnitude of the detection output of the detection circuit DET with a reference level. 1 drive circuit DRV for the auxiliary force applying electromagnet SQL, which generates 1 drive force at a level to compensate for the deficiency in the reference level of the detection output by the comparison output from the comparison circuit COM, and the detection signal A drive period setting circuit GTE synchronizes with the repetition frequency of and operates the one drive circuit DRV for an arbitrary specific period during the - cycle, and the drive period setting circuit GTE sets the operation start timing and end of the drive circuit DRV. A fatigue strength measuring device comprising two adjustment members VR3 and VR4 that can individually adjust the timing.