JPH09281023A - U-shape bending fatigue tester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce the destruction phenomenon caused by U-shape bending fatigue with high accuracy by providing rotary jigs making the test piece fixing jigs connected through rotary shafts freely rotatable between the test piece fixing jigs and upper and lower fixing jigs. SOLUTION: The test piece fixing jigs 2 fixing a test piece 1 are respectively connected to rotary jigs 3 through a rotary shaft 5 and the rotary jigs 6 are fixed to upper and lower jigs 3, 4. By this constitution, the upper and lower test piece fixing jigs 2 can be freely rotated centering around the rotary shafts 5 at a time of up and down vibration. As a result, the stress concentrated to the test piece 1 at the end parts of the test piece fixing jigs is relaxed by the rotation of the rotary jigs and the stress applied to the test piece is mainly applied to a bent processed part to make it possible to execute an accurate U-shape bending fatigue test. In the case of the fatigue test of stress control, it is necessary to attach a strain gauge (load cell) 7 to the upper jig 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bellows of an automobile exhaust system or an exhaust system in a building, and a fatigue fracture phenomenon of a bent portion of the bellows due to vibration or bending of a plate material represented by a leaf spring. The present invention relates to a U-shaped bending fatigue testing machine that reproduces a fatigue fracture phenomenon of a processed part.

[0002]

2. Description of the Related Art Bellows are used in automobile exhaust systems and exhaust systems for air conditioning in buildings. Members are subjected to vibrations propagating from connecting equipment such as an engine or vibrations of gas or liquid flowing through the inside. . Therefore, it is necessary to consider fatigue damage due to these vibrations when selecting materials. In the case of a bellows structure, stress is applied to the bent portion of the bellows due to vibration. Therefore, it is necessary to perform a bending fatigue test for material selection. As a bending fatigue test, there is a JIS Z 2275 fatigue test method using a bending moment on a flat plate, but the actual fatigue phenomenon of a bent part and the fatigue test on a flat plate do not correspond accurately, so the material selection A fatigue test using bending test pieces is desired.

[0003]

As a fatigue test of a bending part, a test method of applying stress to the bending part of the test piece 1 bent in U shape by vertical vibration as shown in FIG. 3 is considered. To be However, when the test piece is a thin plate,
The deflection of the horizontal part of the test piece reduces the vertical vibration and reduces the stress applied to the bent part. Therefore, it is necessary to increase the amplitude of vertical vibration in order to increase the stress applied to the bending portion, but in that case, the stress is concentrated on the test piece at the end of the test piece fixing jig 2 rather than the bending portion. However, the fracture at this portion precedes the fracture at the bending portion. Further, the output stress of the bending test piece is below the detection limit of the strain gauge (load cell) permanently installed in the general-purpose fatigue tester, and it is difficult to carry out the stress control test.

It is an object of the present invention to provide a U-shaped bending fatigue testing machine capable of reproducing a fracture phenomenon of a U-shaped bending member due to bending fatigue with high accuracy.

[0005]

Means for Solving the Problems As a result of earnest studies on means for solving the above-mentioned problems, the present inventors found that the upper and lower jigs 3 and 4 in FIG. The present invention has been accomplished based on the knowledge that the stress concentrated on the test piece at the end of the test piece fixing jig is relieved by releasing it.

That is, the U-shaped bending fatigue tester of the present invention is U-shaped.
When performing a bending bending fatigue test, fix both ends of a U-shaped bending test piece with a test piece fixing jig, fix one end to a lower fixing jig, and the other end to an upper fixing jig that can vibrate vertically. In a fatigue testing machine that is fixed and applies repeated load with a constant vertical amplitude of the upper fixing jig, fixing the test piece connected via a rotating shaft between the test piece fixing jig and the upper and lower fixing jigs. A U-shaped bending fatigue testing machine, which is equipped with a rotating jig that allows the jig to rotate, or a U-shaped bending fatigue testing machine in which a strain gauge is further attached to an upper jig.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a state in which test pieces are set in the U-shaped bending fatigue tester of the present invention.
The test piece fixing jig 2 to which the test piece 1 is fixed is connected to the rotating jig 6 via the rotating shaft 5, respectively. The rotary jig 6 is fixed to the upper jig 3 and the lower jig 4, respectively. With such a configuration, the upper and lower test piece fixing jigs 2 can freely rotate about the rotating shaft 5 when vertically vibrating. As a result, the stress concentrated on the test piece at the end of the test piece fixing jig is relaxed by the rotation of the rotating jig, and the stress applied to the test piece is mainly in the bending part, and the accurate U-shaped bending fatigue test is performed. Can be carried out. Further, in the case of a stress control fatigue test, it is necessary to mount a strain gauge (load cell) 7 on the upper jig 3.

FIG. 2 is a block diagram of a U-shaped bending fatigue tester. The tester main body 8 operates according to a command from the control device 9, and the load necessary for this is provided from the hydraulic power source 10. Further, the output from the load cell 7 makes it possible to carry out a stress control fatigue test.

[0009]

Example A U-shaped bending fatigue test piece having a circular arc with a radius of 20 mm and a width of 10 mm was prepared using stainless steel SUS304 having a plate thickness of 0.8 mm. First, a fatigue test was carried out using this without a rotating jig. As a result, a crack was generated in the test piece at the end of the test piece fixing jig, resulting in destruction. On the other hand, when a fatigue test was carried out by mounting a rotating jig as in the present invention, a fracture occurred at the bending part, and the relationship between the amplitude of vertical vibration and the number of times until fracture was Showed a tendency. Therefore, according to the present invention, it is possible to accurately reproduce the fatigue fracture phenomenon of the bent portion.

[0010]

As described above, by using the U-shaped bending fatigue testing machine of the present invention, it is possible to accurately reproduce the fatigue fracture phenomenon of the bent portion, which was impossible with the conventional fatigue testing machine. Is possible.

[Brief description of drawings]

FIG. 1 is a simulated view in which a jig is mounted in a U-shaped bending fatigue tester of the present invention.

FIG. 2 is a system diagram when stress control is performed by the U-shaped bending fatigue tester of the present invention.

FIG. 3 is a schematic view of a conventional U-shaped bending fatigue tester.

[Explanation of symbols]

 1 Bending test piece 2 Test piece fixing jig 3 Upper jig 4 Lower jig 5 Rotating shaft 6 Rotating jig 7 Load cell 8 Testing machine body 9 Controller 10 Hydraulic power source

Claims (2)

[Claims] 1. When performing a U-shaped bending fatigue test, both ends of the U-shaped bending test piece are fixed by a test piece fixing jig,
One end is fixed to the lower fixing jig, and the other end is fixed to the upper fixing jig that can vibrate vertically. A U-shaped bending fatigue testing machine comprising a rotating jig that allows a test piece fixing jig connected via a rotating shaft to rotate, between the tool and the upper and lower fixing jigs. 2. The U-shaped bending fatigue tester according to claim 1, wherein a strain gauge is attached to the upper jig.