1. The utility model provides a prevent anchor clamps of testing machine received moment of flexure in fatigue test which characterized in that: comprises a left clamp body, a right clamp body, a clamping plate and fork lugs;

the upper end of the clamping plate is fixedly arranged at a chuck of the testing machine, and the lower end of the clamping plate is hinged with the upper end of the fork lug through a bolt; the lower end of the fork lug is assembled with a test piece;

the left clamp body and the right clamp body respectively comprise a supporting beam and a boss, one end of the supporting beam is connected with a bearing support arranged outside, and the other end of the supporting beam is fixedly connected with one end of the boss; the other end of the boss is provided with at least two rolling bearings, and the rolling bearings are in contact with the side faces of the fork lugs and are in rolling fit with the side faces of the fork lugs;

the left side surface and the right side surface of the fork lug are planes which are parallel to each other, and rolling bearings of the left clamp body and the right clamp body are respectively in corresponding contact with the left side surface and the right side surface of the fork lug and are in rolling fit with the left side surface and the right side surface of the fork lug;

the axis of the actuating rod of the testing machine is positioned in the hinge rotation plane of the fork lug relative to the clamping plate; the rotating shafts of the rolling bearings are parallel to each other and are parallel to the hinge shaft of the fork lug opposite to the clamping plate.

2. The clamp for preventing the testing machine from being subjected to bending moment in the fatigue test according to claim 1, is characterized in that: the lower end of the clamping plate and the upper end of the fork lug are connected in a single-lug and double-lug mode, the lower end of the clamping plate is a single lug, the upper end of the fork lug is a double lug, the lower end of the clamping plate is inserted into the upper end of the fork lug, and the overlapped part is hinged through a bolt.

3. The clamp for preventing the testing machine from being subjected to bending moment in the fatigue test according to claim 1, is characterized in that: the clamp springs are arranged at the two ends of the rolling bearing, and the end face of the rolling bearing is prevented from contacting with the boss through the clamp springs, so that the influence of extra friction force is avoided.

4. The clamp for preventing the testing machine from being subjected to bending moment in the fatigue test according to claim 1, is characterized in that: one end of the boss is fixedly connected with the supporting beam through a plurality of bolts, the other end of the boss is provided with a groove for placing a rolling bearing, a plurality of positioning shaft pin holes are formed in the groove, and the rolling bearing is connected with the boss through a shaft pin inserted in the positioning shaft pin holes and is positioned in the groove; the inner ring of the rolling bearing and the shaft pin do not slide relatively, and the shaft pin and the positioning shaft pin hole of the boss do not slide relatively.

5. The clamp for preventing the testing machine from being subjected to bending moment in the fatigue test according to claim 4, is characterized in that: the jump ring has respectively been placed between two medial surfaces of antifriction bearing and recess, avoids through the jump ring antifriction bearing terminal surface and boss contact avoid extra frictional force to influence.

6. The clamp for preventing the testing machine from being subjected to bending moment in the fatigue test according to claim 1, is characterized in that: the rolling bearing is tightly attached to the side face of the fork lug, and lubricating grease is coated on the contact part of the rolling bearing and the fork lug.

7. The clamp for preventing the testing machine from being subjected to bending moment in the fatigue test according to claim 1, is characterized in that: the bearing support column arranged outside adopts a testing machine upright column.

8. The clamp for preventing the testing machine from being subjected to bending moment in the fatigue test according to claim 1, is characterized in that: and the axes of the two testing machine stand columns are coplanar with the axis of the testing machine actuating rod.

9. A method of performing a fatigue test using the jig of claim 1, wherein: the method comprises the following steps:

step 1: determining the size of the support beam according to the distance between the two testing machine stand columns and the size of the test piece, and selecting a rolling bearing with corresponding size and bearing capacity;

step 2: the rolling bearing passes through a positioning shaft pin hole at the groove through a shaft pin to be connected with the boss, a clamp spring is respectively arranged between the rolling bearing and the inner surfaces of two sides of the groove, the diameter of each clamp spring is not larger than the outer diameter of an inner ring of the rolling bearing, the inner ring of the bearing and the shaft pin do not slide relatively, and the shaft pin and the positioning shaft pin hole of the boss do not slide relatively;

and step 3: the upper side of the clamping plate is fixedly arranged at a chuck of the testing machine, and the lower side of the clamping plate is hinged with the upper end of the fork lug through a bolt;

and 4, step 4: fixedly connecting the lug boss with the support beams, connecting the support beams to the upright columns of the testing machine, positioning the two support beams and the upright columns at two sides on the same plane, enabling the outer side surfaces of the rolling bearings to be close to the side surfaces of the fork lugs, and coating lubricating grease on the contact surfaces;

and 5: fixedly supporting the lower end of the test piece, adjusting the height of the clamp, and assembling the lower side of the fork lug with the test piece to enable the axis of the fork lug and the axis of the test piece to form a required angle;

step 6: and loading a test program and carrying out a fatigue test.

Background

Under increasingly severe market competition and stringent technical requirements, the fatigue life of structures is a focus of increasing concern, and components must be subjected to fatigue tests to verify their fatigue properties before being put into use. Fatigue testing of most components is accomplished by fatigue testing machines. A common hydraulic fatigue testing machine adopts an electro-hydraulic servo principle, achieves the purpose of applying a cyclic load by controlling the reciprocating motion of a hydraulic actuator cylinder, and has the advantages of high frequency, quick response, stable loading and the like.

Considering that the fatigue test is a long-time loading process, for a hydraulic fatigue testing machine, the centroid of a test piece is required to be positioned on an axis which passes through the centroid of the actuating rod and is parallel to the loading direction in the test process, so that the phenomenon that one side of a sealing ring of the actuating rod is seriously worn and oil leakage is caused in the long-time fatigue test due to the fact that the actuating rod bears bending moment in the loading process is avoided.

However, the requirement of the eccentric loading fatigue test of the structural member is objective, and aiming at the requirement of the eccentric loading fatigue test, the common method is to divide the loading direction into each simple component without passing through a complex structure of a centroid, calculate the load distribution of each component and simplify the load distribution, and independently carry out the fatigue test on each component; or a standard part is manufactured, the fatigue performance of the material is researched, and the fatigue performance of the structure is further promoted, so that the defects of complex data processing, large error, increased cost and the like exist.

In engineering practice, a method is also provided for simultaneously carrying out fatigue tests on a plurality of test pieces needing eccentric loading by designing a clamp, and the test pieces are symmetrically distributed along the loading direction of an actuating rod of the testing machine, so that no bending moment exists for the actuating cylinder, but the method has problems in later data processing, and the main reason is that when a plurality of test pieces are simultaneously loaded, if fatigue damage occurs to a certain test piece, the load distribution is not uniform, so that the subsequent loading is actually not in accordance with the test requirements, and the test result is inaccurate.

Disclosure of Invention

Aiming at the objective requirement of the eccentric loading fatigue test of the structural member and the problems of the existing method for carrying out the eccentric loading fatigue test of the structural member, the invention provides a clamp for preventing a testing machine from being subjected to bending moment in the fatigue test.

The technical scheme of the invention is as follows:

the clamp for preventing the testing machine from being subjected to bending moment in the fatigue test comprises a left clamp body, a right clamp body, a clamping plate and fork lugs;

the upper end of the clamping plate is fixedly arranged at a chuck of the testing machine, and the lower end of the clamping plate is hinged with the upper end of the fork lug through a bolt; the lower end of the fork lug is assembled with a test piece;

the left clamp body and the right clamp body respectively comprise a supporting beam and a boss, one end of the supporting beam is connected with a bearing support arranged outside, and the other end of the supporting beam is fixedly connected with one end of the boss; the other end of the boss is provided with at least two rolling bearings, and the rolling bearings are in contact with the side faces of the fork lugs and are in rolling fit with the side faces of the fork lugs;

the left side surface and the right side surface of the fork lug are planes which are parallel to each other, and rolling bearings of the left clamp body and the right clamp body are respectively in corresponding contact with the left side surface and the right side surface of the fork lug and are in rolling fit with the left side surface and the right side surface of the fork lug;

the axis of the actuating rod of the testing machine is positioned in the hinge rotation plane of the fork lug relative to the clamping plate; the rotating shafts of the rolling bearings are parallel to each other and are parallel to the hinge shaft of the fork lug opposite to the clamping plate.

Furthermore, the lower end of the clamping plate and the upper end of the fork lug are connected in a single-lug and double-lug mode, the lower end of the clamping plate is a single lug, the upper end of the fork lug is a double lug, the lower end of the clamping plate is inserted into the upper end of the fork lug, and the overlapped part is hinged through a bolt.

Furthermore, the clamp springs are arranged at the two ends of the rolling bearing, and the end face of the rolling bearing is prevented from contacting with the boss through the clamp springs, so that the influence of extra friction force is avoided.

Furthermore, one end of the boss is fixedly connected with the support beam through a plurality of bolts, the other end of the boss is provided with a groove for placing a rolling bearing, a plurality of positioning shaft pin holes are formed in the groove, and the rolling bearing is connected with the boss through a shaft pin inserted in the positioning shaft pin holes and is positioned in the groove; the inner ring of the rolling bearing and the shaft pin do not slide relatively, and the shaft pin and the positioning shaft pin hole of the boss do not slide relatively.

Further, the jump ring has respectively been placed between two medial surfaces of antifriction bearing and recess, avoids through the jump ring antifriction bearing terminal surface and boss contact avoid extra frictional force to influence.

Furthermore, the rolling bearing is tightly attached to the side face of the fork lug, and lubricating grease is coated on the contact part of the rolling bearing and the fork lug.

Furthermore, the bearing support column arranged outside adopts a testing machine upright column.

Furthermore, the axes of the two testing machine stand columns are coplanar with the axis of the testing machine actuating rod.

The method for carrying out the fatigue test by using the clamp comprises the following steps:

step 1: determining the size of the support beam according to the distance between the two testing machine stand columns and the size of the test piece, and selecting a rolling bearing with corresponding size and bearing capacity;

step 2: the rolling bearing passes through a positioning shaft pin hole at the groove through a shaft pin to be connected with the boss, a clamp spring is respectively arranged between the rolling bearing and the inner surfaces of two sides of the groove, the diameter of each clamp spring is not larger than the outer diameter of an inner ring of the rolling bearing, the inner ring of the bearing and the shaft pin do not slide relatively, and the shaft pin and the positioning shaft pin hole of the boss do not slide relatively;

and step 3: the upper side of the clamping plate is fixedly arranged at a chuck of the testing machine, and the lower side of the clamping plate is hinged with the upper end of the fork lug through a bolt;

and 4, step 4: fixedly connecting the lug boss with the support beams, connecting the support beams to the upright columns of the testing machine, positioning the two support beams and the upright columns at two sides on the same plane, enabling the outer side surfaces of the rolling bearings to be close to the side surfaces of the fork lugs, and coating lubricating grease on the contact surfaces;

and 5: fixedly supporting the lower end of the test piece, adjusting the height of the clamp, and assembling the lower side of the fork lug with the test piece to enable the axis of the fork lug and the axis of the test piece to form a required angle;

step 6: and loading a test program and carrying out a fatigue test.

Advantageous effects

When a fatigue test is carried out on a structural part needing to be loaded with an eccentric load, the left clamp body and the right clamp body are matched for use, even if the centroid of the test piece is not on the loading axis of the actuating cylinder, the generated bending moment can be offset by the left clamp body and the right clamp body, and can not be transmitted to the actuating rod, so that the actuating rod only can bear pure tension-compression cyclic load, the abrasion phenomenon of a sealing ring is avoided, and the service life of the testing machine is greatly prolonged.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic structural view of a bending moment-resisting clamp for a testing machine.

FIG. 2 is an exploded view of the bending moment-proof fixture of the testing machine.

Fig. 3 is a schematic view of the left clamp of the present invention.

Fig. 4 is a schematic diagram of the present invention in use with the tab tilted.

In the figure: 1. a left clamp body; 2. a right clamp body; 3. a clamping plate; 4. a fork ear; 5. a support beam; 6. a boss; 61. a groove; 62. positioning the shaft pin hole; 7. a bearing; 8. a shaft pin; 9. a testing machine upright post; 10. a clamp spring; 11. test piece tabs.

Detailed Description

The following detailed description of embodiments of the invention is intended to be illustrative, and not to be construed as limiting the invention.

As shown in fig. 1 to 3, in the present embodiment, the clamp for preventing the testing machine from being subjected to bending moment in the fatigue test includes a left clamp body 1, a right clamp body 2, a clamping plate 3 and a fork lug 4.

The upper end of the clamping plate 3 is fixedly arranged at a chuck of the testing machine, and the lower end of the clamping plate is hinged with the upper end of the fork lug 4 through a bolt; the lower end of the fork lug 4 is assembled with a test piece, and the lower end of the fork lug 4 can be properly modified according to the shape of the actual test piece.

In this embodiment, the lower end of the clamping plate 3 and the upper end of the fork lug 4 are connected in a single-lug and double-lug manner, the lower end of the clamping plate 3 is a single lug, the upper end of the fork lug 4 is a double lug, the lower end of the clamping plate 3 is inserted into the upper end of the fork lug 4, and the overlapping portions are hinged by bolts.

The left clamp body and the right clamp body are matched for use, each clamp body comprises a support beam 5 and a boss 6, one end of the support beam 5 is connected with the stand column 9 of the testing machine, and the other end of the support beam and the boss 6 are fixedly supported through two bolts; the other end of the boss is provided with a groove 61 for placing a rolling bearing 7, a plurality of positioning shaft pin holes 62 are formed in the groove, and the rolling bearing 7 is connected with the boss 6 through a shaft pin 8 inserted in the positioning shaft pin holes 62 and is positioned in the groove; the inner ring of the rolling bearing 7 and the shaft pin 8 do not slide relatively, and the shaft pin 8 and the positioning shaft pin hole 62 of the boss 6 do not slide relatively. Jump ring 10 has respectively been placed between two medial surfaces of antifriction bearing 7 and recess 61, and the jump ring external diameter is not more than the external diameter of antifriction bearing 7 inner circle, avoids through the jump ring antifriction bearing terminal surface and boss medial surface contact avoid extra frictional force to influence.

The left side surface and the right side surface of the fork lug are planes which are parallel to each other, after the installation is finished, the rolling bearings 7 of the left clamp body and the right clamp body are correspondingly clung to and contacted with the left side surface and the right side surface of the fork lug respectively and are in rolling fit, and the contact parts of the left clamp body and the right clamp body are coated with lubricating grease.

In order to ensure reliable transmission of force and to eliminate bending moments, the axis of the actuation lever of the testing machine is in the plane of the pivoting of the fork lugs 4 with respect to the clamping plate 3, and the axes of rotation of the rolling bearings 7 are parallel to each other and to the axis of articulation of the fork lugs 4 with respect to the clamping plate 3. And the axes of the two testing machine stand columns are coplanar with the axis of the testing machine actuating rod.

As shown in fig. 4, in this embodiment, the lug is obliquely loaded, and at this time, the loading direction does not pass through the centroid of the lug, so that a bending moment is generated on the actuating rod of the testing machine in the conventional loading process, which affects the service life of the testing machine. By adopting the included angle of the invention, the lower end of the straight lug piece is fixed, the upper end of the straight lug piece is connected with the lower side of the fork lug through a bolt, and the cyclic load with the direction forming an included angle of 50 degrees with the axis of the lug piece is applied. The specific test steps are as follows:

step 1: determining the size of the support beam according to the distance between the two testing machine stand columns and the size of the test piece, and selecting a rolling bearing with corresponding size and bearing capacity;

step 2: the rolling bearing passes through a positioning shaft pin hole at the groove through a shaft pin to be connected with the boss, a clamp spring is respectively arranged between the rolling bearing and the inner surfaces of two sides of the groove, the diameter of each clamp spring is not larger than the outer diameter of an inner ring of the rolling bearing, the inner ring of the bearing and the shaft pin do not slide relatively, and the shaft pin and the positioning shaft pin hole of the boss do not slide relatively;

and step 3: the upper side of the clamping plate is fixedly arranged at a chuck of the testing machine, and the lower side of the clamping plate is hinged with the upper end of the fork lug through a bolt;

and 4, step 4: fixedly connecting the lug boss with the support beams, connecting the support beams to the upright columns of the testing machine, positioning the two support beams and the upright columns at two sides on the same plane, enabling the outer side surfaces of the rolling bearings to be close to the side surfaces of the fork lugs, and coating lubricating grease on the contact surfaces;

and 5: fixedly supporting the lower end of the test piece, adjusting the height of the clamp, and assembling the lower side of the fork lug and the test piece to enable the axis of the fork lug and the axis of the test piece to form an included angle of 50 degrees;

step 6: and loading a test program and carrying out a fatigue test.

In the test process, the bending moment is offset by the left clamp body and the right clamp body and cannot be transmitted to the actuating rod, so that the actuating rod only bears pure tension-compression cyclic load, the abrasion phenomenon of a sealing ring is avoided, and the service life of the testing machine is greatly prolonged.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.