JPH03229134A - Bending fatigue tester - Google Patents

Abstract

PURPOSE:To attain definite measurement conditions without acting an unnecessary force on a test piece by fixing one end of the test piece to a fixing part, holding the other end by a holding part movable in the direction orthogonal with a bending direction and applying forward and backward bending on the test piece via the holding part by a bending means. CONSTITUTION:One end of the test piece 1 is fixed to the fixing part 12 and the other end is held by the holding part 13 which is movable in the direction orthogonal with the bending direction. The test piece 1 is bent back and forth by the bending means via the holding part 13. The holding part 13 is provided with a force sensor 15 and a robot 11. The force sensor 15 to be provided at the front end of the robot 11 is so formed that the sensor can detect the forces in X-, Y- and Z-directions and the moments around the X-, Y- and Z-axes. The holding part 13 of this constitution is constituted of U-shaped housings 16 and 17, collared inner shafts 18 and 19 which penetrate these housings in parallel, screws 20 and 21 which are screwed thereto, outer shafts 24 and 25 which are supported by bearings 22 and 23, and spacers 26 and 27 for adjusting the spacing therebetween.

Description

[Detailed Description of the Invention] (Summary) The present invention relates to a bending fatigue test device for plastic test pieces, which aims to enable highly reliable measurements, and which tests the test piece against a test piece at a specified distance or with a commanded force. In a bending fatigue testing device that has a bending means that repeats a specified number of bending operations, a detection means that detects the force applied to the test piece, and a judgment means that judges the fatigue of the test piece, One end of the piece is fixed to a fixed part, and the other end is held by a holding part that is movable in a direction perpendicular to the bending direction,
The bending means is configured to bend the test piece back and forth through the holding part.

[Industrial application field]

The present invention relates to a bending fatigue testing device for plastic test pieces.

[Conventional technology]

As a bending fatigue test device for plastic test pieces (hereinafter referred to as test pieces), the one shown in the explanatory diagram in Fig. 6 (JISK
(excerpt from the explanation of 7118).

In the figure, 1 is a test piece, one end of which is fixed to the plate 2, and 12 the other end of which is fixed to the fixing part 3.

The middle part of the plate 2 has a thinner thickness, and a strain gauge 4 for detecting force is attached thereto.

The other end of the test piece 1 is fixed to a link 5, and the link 5 is rotatably supported by a link 6 and a rotating shaft 7.

Reference numeral 8 denotes a disk, which is rotatable around a rotating shaft 9.

The link 6 is rotatably supported by a rotating shaft 10 located at a distance e from the center of rotation of the disc 8.

Therefore, when the disk 8 is rotated by, for example, a motor, the test piece I is bent in the vertical direction by the links 5 and 6.

[Problem to be solved by the invention]

In the bending fatigue testing device configured as described above, in addition to the vertical force to give vertical movement to the test piece, for example, the tensile and compressive force in the length direction and the position supported by the link 5 are applied. Forces in various directions act, such as bending moments at .

In this way, various unnecessary forces are applied to the test piece, making it difficult to clarify the measurement conditions, reducing the reliability of the measurement, and causing measurement results to vary depending on the equipment. There was a problem.

The present invention aims to enable highly reliable measurements.

[Means to solve the problem]

In order to achieve the above object, in the present invention, as shown in the side view of FIG. The holding part 13 is held movably in the direction, and the holding part 13 is held by a bending means.
The test piece L is bent back and forth through the .

[Function] The test piece is held in the holding part so that it can move in a direction perpendicular to the bending direction, so if a force other than the bending direction is applied, the test piece will move in that direction and cause damage to the test piece itself. The impact will be minimal.

〔Example〕

1 to 5 show an embodiment of the present invention.

Identical parts are designated by the same reference numerals throughout the figures.

In the present invention, as shown in the side view in FIG. The test piece l is held by the holding part 13 and bent back and forth by the bending means via the holding part 13.

In the figure, reference numeral 11 is a so-called orthogonal robot that can move in three axes of XYZ.

A six-axis force sensor 15 that can detect, for example, forces in the XYZ-axis directions and moments around the XYZ-axes is attached to the tip of the robot 11.

Reference numeral 1 denotes a test piece, one end of which is fixed to a fixing part 12 and the other end held by a holding part 13.

The holding part 13 is shown in the side view of FIG. 2(a) and the side view of FIG.
) As shown in the front view of FIG. Screws 2 screwed into the inner shafts 18 and 19 to fix the
0 and 21, outer shafts 24 and 25 supported by bearings 22 and 23 so as to be rotatable around inner shafts 18 and 190, and outer shaft 24.
In order to adjust the gaps between the housings 16 and 17 to desired dimensions, spacers 26 and 27 made of aluminum plates, for example, 0.5 to 3 inches thick are inserted between the housings 16 and 17, and the housings 16 and 17 are It consists of screws 28 and 29 that are fixed together via screws 26 and 27.

The test piece 1 is inserted and held between the outer shafts 24 and 25.

Because of this configuration, when the holding part 13 moves in the vertical direction, the outer shafts 24 and 25 rotate and a large frictional force is exerted at the positions where the outer shafts 24 and 25 and the test piece l are in contact with each other. It moves automatically without any need.

This is an excellent feature compared to the conventional technique in which a large force acts in the lateral direction as shown in FIG. 1 when the test piece 1 is bent due to vertical movement by the link.

When this holding part 13 moves up and down, the test piece 1 is bent, but the gap between the outer shafts 24 and 25 required to hold the test piece 1 increases accordingly.

Therefore, it is desirable that the gap d between the outer shafts 24 and 25 be set so that the specimen 1 can be held with a margin when the specimen 1 is bent to the maximum.

FIG. 3 is an explanatory diagram showing a state in which the test piece 1 is tilted by an amount θ from a horizontal position.

To simplify the explanation, the outer shafts 24 and 25
Assume that the radii r of are equal.

Note that the following explanation holds true even if the two values are different.

In the figure, test piece 1 has outer shafts 24 and 25.
Suppose that they are in contact with each other at positions P and Q, respectively.

At this time, the gap d0 between the outer shafts 24 and 25
Therefore, the gap d0 between the outer shafts 24 and 25
should be set slightly larger than the above value.

Incidentally, the inclination θ of the test piece 1 can be estimated in advance as follows.

As shown in Figure 4, when one end of a beam of length, width b, and thickness t is fixed and the other end is bent by applying a load P, according to the cantilever theory, the beam The following relationship holds between the deflection δ, the inclination angle θ, and the load P.

bt3 Note that E is the longitudinal elastic modulus.

Therefore, if the maximum deflection δ or the maximum load P is known in advance, the inclination angle θ and, by extension, the necessary gap can be estimated from the above equation.

In addition, by looking at the output of the force sensor in FIG. 1, it is possible to know what kind of force is acting when setting or measuring the test piece 1, and to judge the validity of the measurement.

Although we have described the case where a robot is used as the bending means for the test piece 1, it is not limited to a robot, and any mechanism that can perform repeated movements may be used. For example, a uniaxial sliding mechanism that reciprocates in the Z direction may be used. It's okay.

In this case, the configuration is further simplified and an inexpensive device can be provided.

Furthermore, although a six-axis force sensor is used as a force detection mechanism, the present invention is not limited to this, but it is also possible to use a sensor that can detect force in the operating direction, such as a load transducer that detects force only in the l-axis direction. You may also use

Next, in actual measurements, a commanded force may be repeatedly applied to the test piece, or a commanded distance may be repeatedly moved.

A measuring method for repeatedly moving a commanded distance will be described with reference to the block diagram of FIG. 5.

Based on commands from the command device 30, a repetitive motion mechanism (robot in FIG. 1) 11 is driven to repeatedly bend the test piece 1.

The command device 30 commands the repetitive motion mechanism 11 including the final number of repetitions N and the distance to be moved.

Even if it is determined that the test piece 1 does not get fatigued after repeating the operation N0 times, the repeating operation ends.

However, N is not necessarily a necessary parameter, but can be used to command the repetitive motion mechanism 11 to operate an infinite number of times, and to forcibly terminate the motion from the command device 30 as necessary, depending on fatigue level data, etc. You can also do it.

The force applied to the test piece l is detected by a force detection mechanism (force sensor in Fig. 1) 15, and the measured value of the first cycle is
The measured value of the cycle is stored in the storage device 31.

Then, the measured value of the Nth cycle is temporarily stored in the measured value storage device 32 of the Nth cycle.

The first cycle stiffness value calculation device 33 calculates the first cycle stiffness value based on the data of the first cycle measured value storage device 31 and outputs it to the first cycle stiffness value storage device 35 .

Similarly, in the stiffness value calculation device 34 of the Nth cycle,
The stiffness value for the Nth cycle is calculated based on the data in the measured value storage device 32 for the cycle, and is output to the stiffness value storage device 36 for the Nth cycle.

The fatigue determination device 37 manually inputs the data in the stiffness value storage device 35 for the first cycle and the data in the stiffness value storage device 36 for the Nth cycle, compares them, and determines that the stiffness value for the Nth cycle is the stiffness value for the first cycle. A predetermined percentage of the value (e.g. 60%)
It is considered that you are fatigued when it is below.

The result of the determination is notified to the command device 30, and the command device 30 outputs a stop command to the repeating mechanism 11 to end the measurement.

When commanding a force, the command device 30 commands the repetitive motion mechanism 11 to perform a repetitive motion on the test piece l so as to output a predetermined maximum output. When the amount exceeds a predetermined amount, fatigue is determined.

As described above, the bending fatigue testing device of the present invention is capable of absorbing the amount of movement in the horizontal direction and rotational direction when holding the test piece 1, and
In addition, since the test piece 1 can be held at appropriate intervals depending on its thickness, the component of force in directions other than the vertical direction that causes the test piece 1 to move up and down becomes extremely small.

Therefore, measurement conditions become clear and highly reliable measurement becomes possible.

〔Effect of the invention〕

According to the present invention, it is possible to prevent unnecessary force from acting on the test piece, and the measurement conditions are made clear, making it possible to perform highly reliable measurements.

[Brief explanation of drawings]

Figure 1 is a side view of the bending fatigue testing apparatus of the present invention, Figure 2 (
al is a side view of the holding part, Fig. 2(b) is a front view of Fig. 2(a), Fig. 3 is an explanatory diagram showing the state where the test piece is tilted by θ from the horizontal position, and Fig. 4 is a cantilevered state. FIG. 5 is an explanatory diagram showing a beam. FIG. 5 is a block diagram of the structure of a bending fatigue testing apparatus according to the present invention. FIG. 6 is an explanatory diagram of a conventional bending fatigue testing apparatus. In the figure, 1 is a test piece, 11 is a robot, 12 is a fixed part, 13 is a holding part, 15 is a force sensor, 1
6.17 is the housing, 18.19 is the inner shaft, 20.21.28.29 is the screw, 22.23 is the bearing, 24.25 is the outer shaft, 26.27 is the spacer, 30 is the command device, 31 is the 1
A cycle measurement value storage device, 32 a measurement value storage device for the Nth cycle, 33 a first cycle stiffness value calculation device, 3
4 is a stiffness value calculation device for the Nth cycle, 35 is a stiffness value storage device for the first cycle, 36 is a stiffness value storage device for the Nth cycle, and 37 is a fatigue determination device. /IIoK'F Bending fatigue of the present invention! The front view of the 11111 side of the f'd device's first holding cap (G) is an explanatory diagram showing a state in which the piece is tilted from the horizontal position by an amount t. Explanatory diagram No. 4 Explanatory diagram of the conventional bending fatigue test device Fig. 5

Claims (1)

[Claims] A bending means that repeatedly performs a bending operation a specified number of times on a test piece (1) at a specified distance or with a commanded force, and detecting the force applied to the test piece. In a bending fatigue test apparatus having a detection means and a determination means for determining fatigue of the test piece, one end of the test piece (1) is fixed to a fixing part (12),
The other end is held by a holding part (13) that holds the other end movably in a direction perpendicular to the bending direction, and the bending means reciprocates the test piece (1) via the holding part (13). A bending fatigue testing device characterized by: