JPH0344258B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a jig for testing materials, and more particularly to a jig for testing bending of brittle materials.

Conventionally, bending tests on brittle materials have been performed using an Instron universal testing machine with a bending test jig attached. This bending test jig uses a 4-point bending method.
Fixed fulcrums 104, 10 as shown in FIG.
4' and pressure wedges 102, 102' that come into contact with the test piece 105 placed on these supports, and a spherical seat 103 that engages with the spherical surface 101a of this loading platform. A spherical seat is attached to the crosshead 106 of the tester. The crosshead of the tester is then moved toward the test piece 105, and two pressure wedges 10 are attached to the test piece.
A load is applied to the test piece by pressing 2,102'. If there is a gap between one of the pressure wedges and the test piece, the other pressure wedge receives a reaction force from the test piece, and the load table 101 rotates by sliding on the spherical seat 103, filling the gap and separating the two An equal load will be applied to the specimen via the pressure wedge. As described above, the purpose of the four-point bending type bending test jig is to equalize the loads applied to the test piece through the two pressure wedges.
However, this bending test jig has the following drawbacks. First, the spherical load table itself is quite heavy, and since there is friction between the spherical surface and the spherical seat, the spherical load table has the drawback of not being able to rotate sufficiently. For this reason, in actual bending tests, a method is used in which a load is applied to the vicinity of the measured load, and after the test piece and pressure wedge have become compatible, the load is applied again. Furthermore, as shown in Figure 1, if the direction in which the load is applied is the Y-Y' direction, and the longitudinal direction of the test piece placed on the fulcrum is the X-X' direction, then the X-X' direction and the Y-Y In the Z-Z' direction perpendicular to the plane formed by the ' direction, as the load increases, the spherical load platform becomes more likely to rotate and becomes unstable. Therefore, the spherical load platform and the spherical seat must be loosely connected so that they are restrained to some extent. As a result, the friction on the spherical seat increases and the rotation to fill the gap tends to be insufficient, making it difficult to apply an equal load to the test piece via the two pressure wedges. Second, the contact area between the spherical seat and the spherical surface is large, and processing costs are high in order to improve the precision of dimensions and roughness.

An object of the present invention is to provide a bending test jig that eliminates the drawbacks of the prior art as described above.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIG.

FIG. 2 shows a bending test jig for carrying out the present invention, which is a conventional crosshead 13.
It has a cylinder block 12 attached to the cylinder block 12. This cylinder block is provided with a plurality of cylinders, for example two cylinders 6, 6'. In one embodiment, pistons 1, 1' of equal diameter are slidably inserted into these cylinders. Note that numerals 8 and 8' indicate O-rings. Piston rods 9, 9' extend from these pistons,
At the tips of these piston rods are pressure wedges 2,
2' is attached. These pressure wedges are arranged so as to contact the test piece 5 placed on the fulcrums 4, 4'. The fulcrums 4, 4' are fixed bases 20,
It is mounted on legs 21, 21' provided at 20'. Note that the symbols 22 and 22' are the legs 21 and 2.
1' and the fixed bases 20, 20'.

One end of the cylinder 6, 6' is a bush 10, 1.
0', and the piston rods 9, 9' are slidably and sealingly inserted into the central holes provided in these bushes. The piston side of the cylinder is communicated by a flow path 3, and these cylinders and the flow path are filled with a fluid, for example oil 11.

The cylinder block is provided with an inlet 15 for filling the cylinder with oil, and this inlet is plugged with a blind stopper 7.

The function of the above jig is as follows.

Place the test piece 5 on the fulcrums 4, 4' and then place the test piece 5 on the cylinder block 12 attached to the crosshead.
the pressure wedges 2, 2'
A load is applied to the specimen through the At this time, if the two pressure wedges do not touch the test piece at the same time and there is a gap between one of the pressure wedges and the test piece, the pressure wedge that first contacted the test piece will be separated from the test piece. The reaction force pushes the piston up. The oil in the cylinder rises to a pressure equal to the reaction force divided by the pressure-receiving area of the piston. Due to Pascal's principle, this pressure propagates through the oil and forces the piston with the gap down. The gap with the test piece can then be filled. The above bending test jig is of a type that seals the oil in the cylinder and the flow path, but apart from this, oil with equal pressure is supplied into the two cylinders from another hydraulic source, and the cylinder block is sealed. Alternatively, only the piston may be moved toward the test piece without moving the test piece, and the load may be applied via a pressure wedge. In this type, the load applied to the test piece is determined by the oil pressure supplied from the pressure source. This type of application includes constant load double torsion testing, which is a fracture mechanics test for brittle materials, and has high utility value. As described above, according to the present invention, even if there is a gap between one pressure wedge and the test piece, this gap is immediately corrected. Furthermore, since the pressure-receiving areas of the two pistons are equal, the loads applied to the test piece through the two pressure wedges are equal, and the direction in which the piston moves due to sliding between the piston rod and bush is always constant. , the instability caused by rotation in the Z-Z' direction of the conventional type is eliminated. Furthermore, in the bending test jig of the present invention, it is not only the O-ring groove of the piston and the inner surface of the cylinder that are finished with high precision, but the area to be finished is smaller than that of a conventional spherical surface. There is a practical benefit of lower costs.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional bending test jig, Figure 2 is a sectional view of a conventional bending test jig.
The figure is a sectional view of the bending test jig of the present invention. 1, 1'... Piston, 2, 2'... Pressure wedge, 3... Channel, 4, 4'... Fulcrum, 5... Test piece, 6, 6'... Cylinder, 9, 9' ... Piston rod, 11 ... Oil, 12 ... Cylinder block, 13 ... Crosshead.

Claims (1)

[Scope of Claims] 1. A cylinder block attached to a crosshead, a plurality of cylinders provided on the cylinder block, and a cylinder that is slidably inserted into the plurality of cylinders and is moved by fluid pressure within the cylinders. A pressure wedge is provided at the tip of a piston rod extending from the piston to contact the test specimen, and each cylinder is communicated with a flow path so that the fluid pressure in each cylinder is equal. Test jig. 2. The jig according to claim 1, wherein each piston has an equal fluid pressure receiving area. 3. The jig according to claim 1, wherein the fluid pressure receiving area of each piston is set differently so that the load applied to the test piece via the pressure wedge corresponds to the fluid pressure receiving area of each piston.