CN110132739B - A fretting fatigue test normal load loading device and method - Google Patents

Abstract

The invention relates to a fretting fatigue test normal load loading device and method. The loading device consists of two parts: a fixed part and a load loading part. Specifically include: fretting pad, first clamping plate, second clamping plate, load cell, load adjustment screw, lock nut, limit screw, positioning nut, limit nut, bushing, fixing plate, fixing bolt , inner fixed block, outer fixed block. The invention realizes the fretting fatigue test on the common fatigue testing machine.

Description

A fretting fatigue test normal load loading device and method

technical field

The invention relates to the field of fretting fatigue test, in particular to a loading device and method for normal load in the fretting fatigue test of a standard specimen in a laboratory.

Background technique

The tenon joint structure is widely used in aero-engine axial compressors, turbines and other power machinery. Fretting fatigue will accelerate the initiation and propagation of cracks in the tenon joint and accelerate the failure of components. The disks and blades of aero-engine compressors are widely made of titanium alloys, which are sensitive to fretting fatigue.

In order to study the fretting fatigue characteristics of materials, it is necessary to carry out fretting fatigue tests in the laboratory. Ordinary uniaxial fatigue testing machines cannot apply normal loads to standard specimens, so they cannot be directly used for fretting fatigue testing. At present, fretting fatigue tests are carried out either by multiaxial fatigue testing machines or by adding devices to uniaxial fatigue testing machines to apply normal loads to the specimens. At present, the devices that apply normal force in the fretting fatigue test are mostly loaded by hydraulic loading and loading ring. The normal load that can be applied by hydraulic loading is relatively large, but because the left and right sides are loaded at the same time, even the control program is difficult to guarantee. The normal loads on the left and right sides can be the same in size, so the specimen may be subjected to additional bending moments, which will affect the test accuracy. Although the loading ring loading can overcome this problem, it cannot be applied due to the simple structure of the loading ring itself. Large normal load, and the loading ring is generally not axially fixed, so the axial stiffness is small.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is: to overcome the deficiencies in the background technology, to provide a fretting fatigue test method load loading device and method, so as to realize the purpose of carrying out the fretting fatigue test on a common fatigue testing machine. The invention combines the advantages of the existing two types of devices, and can apply a large normal load to the test piece, and at the same time realize unilateral loading through the mechanical structure, thereby avoiding the extra bending moment brought to the test piece due to asymmetric loading.

The technical solution of the present invention: a normal load loading device for a fretting fatigue test, comprising: a test piece (1), a fretting pad (2), a first clamping plate (3), and a second clamping plate (4) , load cell (5), load adjustment screw (6), fixing plate (7), limit screw (8), limit nut (9), outer fixing block (10), inner fixing block (11), Loose nut (12), shaft sleeve (13), fixing screw (14) and positioning nut (15). The outer fixing block (10) and the inner fixing block (11) fix the entire normal load loading device on the uprights on both sides of the fatigue testing machine under the action of the bolts, and the inner fixing block (11) is connected with the fixing screw (14), and is fixed after the fixing. Corresponding positions of the plate (7) are provided with threaded holes for connecting the fixing screw (14). The fixing plates (7) on both sides are connected by a limit screw (8), a positioning nut (15) is installed on the limit screw (8), a through hole is opened in the corresponding position of the fixing plate (7), and the positioning nut The function of (15) is to position the right fixing plate (7), and the limit nut (9) and the positioning nut (15) clamp the right fixing plate (7) together, thereby achieving a fixing effect. The right side of the second clamping plate (4) is provided with threaded holes, and the load cell (5) is mounted on the second clamping plate (4) by screws. After the load adjusting screw (6) passes through the threaded hole on the right side plate of the first clamping plate (3), install the loosening nut (12), and then push it against the load cell (5). Through holes are formed in the corresponding positions of the first clamping plate (3) and the second clamping plate (4), so that the limit screw (8) passes through, so that the whole device can be fixed on the two sides of the fatigue testing machine. The column is up. Rectangular grooves are pre-opened on the left side plate of the first clamping plate (3) and the second clamping plate (4) for installing the fretting pad (2); in the test, the normal load of fretting fatigue passes through the load Adjust screw (6) to apply. A shaft sleeve (13) is added between the first clamping plate (3), the second clamping plate (4) and the limit screw (8) to reduce wear.

The fretting fatigue normal load loading device can realize different fretting pair forms by changing the geometry and size of the fretting pad according to different specific requirements.

The fretting fatigue normal load loading device can be installed on different types of fatigue testing machines by replacing fixed screws of different lengths.

A method for loading a normal load of a fretting fatigue test of the present invention comprises the following steps:

In the first step, during the test, the fretting fatigue normal force is applied through the load adjustment screw (6), the load cell (5) is fixed on the second clamping plate (4), and the load adjustment screw (6) is tightened by tightening the load adjustment screw (6). , the load adjustment screw (6) will first push on the load cell (5), and under the action of the limit screw (8), the load cell (5) moves to the left together with the second clamping plate (4), Until the micro-motion pad (2) on the second clamping plate (4) is in contact with the test piece (1), it plays a positioning role. Then the second clamping plate (4) is not in motion.

In the second step, continuing to tighten the load adjusting screw (6) will make the first clamping plate (3) move to the right as a whole, and the fretting pad (2) on the left side of the specimen (1) can also be pressed against the specimen. .

In the third step, continue to tighten the load adjusting screw (6), and the fretting pads (2) on both sides can be pressed against both sides of the specimen (1) with a certain load to achieve the purpose of applying a normal load. After reaching the expected normal load, tighten the anti-loosening nut (12), which can prevent the reduction of the normal load caused by thread loosening during the test. The load cell (5) can be connected with an external display, so that the change of the normal force can be continuously monitored during the experiment.

Compared with the prior art, the present invention has the following advantages:

(1) Since the specimen is first fixed on the upper and lower chucks of the fatigue testing machine, it cannot be guaranteed to be located in the symmetrical center of the two fretting pads, so that the specimen is bent by an asymmetric load. In the present invention, this situation can be avoided, and the micro-movement pads can be automatically positioned symmetrically to both sides of the test piece during the process of applying the normal load with the load adjusting screw.

(2) The present invention has a simple structure and can apply a large normal load. It can be fixed on the fatigue testing machine, and the axial rigidity is large. It has a wide range of applicability and can be used for different types of fatigue testing machines.

Description of drawings

Fig. 1 is the front view of the overall structure of the loading device of the present invention;

Fig. 2 is the isometric drawing of the overall structure of the loading device of the present invention;

3 is an isometric view of the first clamping plate in the loading device of the present invention.

Detailed ways

The invention will be described in detail below with reference to the accompanying drawings and embodiments.

First of all, the whole device needs to be fixed to the fatigue testing machine through the columns on both sides of the fatigue testing machine.

As shown in Figures 1-3, the entire fretting fatigue normal load loading device of the present invention is divided into two parts: a fixed part and a load loading part;

The load loading part includes a micro-motion pad 2 , a first clamping plate 3 , a second clamping plate 4 , a load cell 5 , a load adjusting screw 6 , a locking nut 12 and a shaft sleeve 13 . The micro-motion pad 2 can be replaced according to different needs and needs of testing. The first clamping plate 3 as shown in Fig. 3 is connected by two left and right flat plates through four rods. The right side of the left plate has a groove for placing the fretting pad 2, and the right plate has a threaded through hole for installing the load adjustment. Screw 6, the load adjustment screw 6 passes through the threaded through hole and then rests on the load cell 5. The load cell 5 is fixed on the right side of the second clamping plate 4 with screws, and the left side of the second clamping plate 4 is also open. There are grooves for installing the micro-motion pad 2. Through holes are opened at the corresponding positions of the first clamping plate 3 and the second clamping plate 4, and the limit screw 8 is fixed on the fixing plates 7 on both sides through these through holes, so as to limit the displacement of the load-bearing part, Movement of the load-carrying part is only allowed in the normal direction, i.e. the x-direction in Figure 1.

The fixing part consists of a fixing plate 7 , a limit screw 8 , a limit nut 9 , an outer fixing block 10 , an inner fixing block 11 , a fixing screw 14 and a positioning nut 15 . There is a fixed plate 7 on each side, and the function of the fixed plate 7 is to support the limit screw 8 . The load loading part is supported by the limit screw 8 . Therefore, the limit screw is mainly affected by the gravity of the load-bearing part and the friction force caused by the normal load in the contact area during the test. Therefore, it is necessary to check the strength of the limit screw 8 when it is bent. The function of the positioning nut 15 is to position the right fixing plate 7 , and the limit nut 9 and the positioning nut 15 clamp the right fixing plate 7 , so as to fix the right fixing plate 7 . The corresponding positions of the left and right fixing plates 7 are provided with threaded through holes, the corresponding positions of the inner fixing block 11 are provided with stepped holes for installing the fixing screws 14, and the fixing screws 14 are assembled to the threads on the fixing plate 7 through the stepped holes. in the through hole. Finally, the outer fixing blocks 10 and inner fixing blocks 11 on both sides fix the entire normal load loading device on the columns on both sides of the fatigue testing machine under the action of bolts.

During the test, the specimen 1 was first clamped to the upper and lower chucks of the fatigue testing machine. The load is applied by tightening the load adjustment screw 6. The load adjustment screw 6 will first push against the load cell 5, and drive the second clamping plate 4 to move to the left until the fretting pad 2 on the right is in contact with the test piece 1. The second clamping plate 4 no longer moves, and has the effect of positioning. Then continue to tighten the load adjustment screw 6, under the action of the thread, the first clamping plate 3 will move to the right until the left fretting pad 2 is also pressed against the specimen 1, continue to tighten the load adjustment nut 6, the two The fretting pads 2 on the side can be pressed against both sides of the specimen with a certain value of normal load. After the normal load reaches the level required for the test, tighten the locknut 12. The load cell 5 is connected with a display, which can monitor the magnitude of the normal load. The lock nut 12 can ensure that the normal load will not be reduced due to thread loosening during the test.

In order to reduce the wear between the first clamping plate 3, the second clamping plate 4 and the limit screw 8, between the through holes of the first clamping plate 3 and the second clamping plate 4 and the limit screw 8 Add bushing 13.

After the test, first loosen the anti-loosening nut 12, and then loosen the load adjusting screw 6. After the display of the load cell 5 is reduced to 0, continue to loosen the load adjusting screw 6. The first clamping plate 3 will move to the left. After the first clamping plate 3 moves to the left for a certain distance, there is enough space to take out the test piece.

The parts of the present invention that are not described in detail belong to the well-known technology in the art.

The above description is only a part of the specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Any person familiar with the art within the technical scope disclosed by the present invention can easily think of changes or substitutions. Included within the scope of protection of the present invention.

Claims (1)

1. A fretting fatigue test normal load loading device, characterized in that it comprises: a test piece (1), a fretting pad (2), a first clamping plate (3), a second clamping plate (4) , load cell (5), load adjustment screw (6), fixing plate (7), limit screw (8), limit nut (9), outer fixing block (10), inner fixing block (11), The loose nut (12), the shaft sleeve (13), the fixing screw (14) and the positioning nut (15); the outer fixing block (10) and the inner fixing block (11) fix the entire normal load loading device under the action of the bolts. On the columns on both sides of the fatigue testing machine, the inner fixing block (11) is connected to the fixing screw (14), and the corresponding position of the fixing plate (7) is provided with a threaded hole for connecting the fixing screw (14). The testing machine determines a fixed screw (14) with an appropriate length to achieve the purpose of adapting to different fatigue testing machines; the fixing plates (7) on both sides are connected by a limit screw (8), and the positioning nut (15) is installed at the limit On the screw (8), a through hole is opened at the corresponding position of the fixing plate (7). The function of the positioning nut (15) is to position the right fixing plate (7), while the limit nut (9) and the positioning nut ( 15) Clamp the fixing plate (7) on the right side together to achieve the effect of fixing; the right side of the second clamping plate (4) is provided with threaded holes, and the load cell (5) is installed on the second clamp by screws on the holding plate (4); after the load adjusting screw (6) passes through the threaded hole on the right side plate of the first holding plate (3), install the locking nut (12), and then push it against the load cell (5) There are through holes in the corresponding positions of the first clamping plate (3) and the second clamping plate (4), so that the limit screw (8) passes through, so that the whole device can be fixed on both sides of the fatigue testing machine Rectangular grooves are pre-opened on the left side plate of the first clamping plate (3) and the second clamping plate (4) for installing the micro-motion pad (2). By modifying the micro-motion pad (2) ) to realize the fretting fatigue test of different fretting pairs; in the test, the normal load of fretting fatigue is applied through the load adjusting screw (6), and the first clamping plate (3), the second clamping plate (3), the second clamping A shaft sleeve (13) is added between the holding plate (4) and the limit screw (8) to reduce wear.

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