CN102590001A - Testing method for multi-directional fretting fatigue and testing machine therefor - Google Patents

Abstract

A multi-directional fretting fatigue test method and its testing machine. The method is as follows: the upper fixture is connected with the electromagnetic excitation actuator through the force sensor, the upper fixture clamps the spherical upper test piece, and the lower fixture is made of piezoelectric ceramics. The actuator is connected through the load cell, and the lower fixture clamps the lower specimen on the plane; the upper and lower specimens are brought into contact, and the data acquisition control system controls the upper specimen to apply the set vertical load; then controls the electromagnetic excitation actuator and the pressure The actuation of the electric ceramic actuator realizes the multi-directional fretting friction between the upper and lower specimens; at the same time, the friction force is measured by the force sensor 2 connected with the lower fixture, and sent to the data acquisition and control system for analysis. This method can easily cause the material to undergo multi-directional fretting friction and wear with small displacement, and more realistically simulate the multi-directional fretting damage of components under alternating loads. The control and testing accuracy is high, and the reproducibility of experimental data is good. And its degree of automation is high.

Description

A multi-directional fretting fatigue test method and its testing machine

technical field

The invention belongs to the field of friction technology research, in particular to a multidirectional fretting fatigue test method and a test machine.

Background technique

Fretting refers to the relative motion of extremely small amplitude (micron level) between two contact surfaces (such as tight fitting surfaces) under the action of alternating loads such as mechanical vibration, fatigue load, electromagnetic vibration or thermal cycle. The contacting surfaces are usually nominally stationary, i.e. fretting occurs in mechanical parts that are "tightly" fitted. Fretting tribology is a branch of disciplines that studies the mechanism of fretting, damage, testing, monitoring, and prevention. Electrical Engineering etc. Fretting is a friction method with a small relative motion range, and the material damage caused by it is usually manifested in two forms, namely: (1) Wear caused by fretting: fretting can cause surface wear between contact surfaces, resulting in material damage. Losses and changes in component dimensions, causing component seizure, loosening, power loss, increased noise, or source of contamination. (2) Fatigue caused by fretting: fretting can accelerate the initiation and expansion of cracks, greatly reducing the fatigue life of components, and the fretting fatigue limit can even be lower than 1/3 of the ordinary fatigue limit. Often this form of injury is more dangerous, resulting in some catastrophic accidents.

Under the condition of ball-plane contact, fretting can be divided into four basic fretting modes: tangential, radial, rolling and torsion. Rolling fretting and torsion fretting are both small-angle rotational motions of the grinding pair on the contact surface under the action of normal load. Both tangential fretting and radial fretting are the linear motions of the grinding pair with small displacement on the contact surface under the action of normal load. The difference is that the normal load direction of tangential fretting is perpendicular to its motion direction. , the radial fretting normal load direction is consistent with the motion direction.

Multi-directional fretting is the relative motion of micro-vibration between contact pairs under alternating load, which is characterized in that it is a compound of tangential fretting and radial fretting. There are a large number of multi-directional fretting in mechanical devices and living organisms, such as: fretting wear and fretting fatigue failure of tight fitting surfaces of rolling stock axles and various yoke shaft mechanisms, high temperature composite fretting damage of nuclear reactors. Test and analyze multi-directional fretting to clarify the wear mechanism and the relationship with related working conditions, which can provide accurate and reliable test basis for the design, manufacture and maintenance of related parts, so as to reduce the initiation and expansion of cracks , It is of great significance to improve the fatigue life of parts. However, there are no reports on multi-directional fretting test methods and equipment.

Contents of the invention

The first object of the present invention is to provide a multi-directional fretting fatigue test method, which can conveniently cause multi-directional fretting friction and wear of materials with small displacements, and more realistically simulate the behavior of components under alternating loads. Multi-directional fretting damage, high precision of control and testing, good reproducibility of experimental data; and high degree of automation.

The technical solution adopted by the present invention to realize the first object of the invention is: a kind of multidirectional fretting fatigue test method, and its practice is:

a. Connect the upper fixture with the electromagnetic excitation actuator through the load cell, and the vertical centerline of the clamping cavity of the upper fixture is aligned with the axis of the electromagnetic excitation actuator, and use the upper fixture to clamp the spherical upper test piece Then connect the lower fixture with the piezoelectric ceramic actuator through the second load cell, and the horizontal centerline of the clamping cavity of the lower fixture is aligned with the axis of the piezoelectric ceramic actuator, and use the lower fixture to clamp the lower surface of the plane. test piece; and align the center of the upper test piece with the test point of the lower test piece;

b. Make the upper and lower specimens contact, and under the feedback of load cell 1, the data acquisition and control system controls to apply the set vertical load P to the upper specimen; then the data acquisition and control system controls the electromagnetic excitation actuator at the same time And the action of the piezoelectric ceramic actuator, so that the upper fixture and the upper specimen held by it move vertically with the set amplitude and reciprocating times, and the lower fixture and the lower specimen held by it move with the set amplitude Reciprocate horizontally with the number of reciprocations to achieve multi-directional fretting friction between the upper and lower specimens;

c. While multi-directional fretting friction occurs on the upper and lower test pieces, the friction force is measured through the load cell 2 connected to the lower fixture, and sent to the data acquisition and control system for analysis.

Compared with prior art, the beneficial effect of the present invention is:

1. In the method of the present invention, the spherical upper test piece and the lower plane test piece are respectively connected with a vertical electromagnetic exciter and a horizontal piezoelectric ceramic actuator, and the spherical upper test piece is driven by the electromagnetic vibrator to make radial (Vertical) micro-motion, and at the same time, the piezoelectric ceramic actuator drives the sample under the plane to make tangential (horizontal) micro-motion, thus realizing the simultaneous radial and tangential movement between the spherical upper specimen and the lower plane specimen. Double multi-directional micro-movement can analyze and test multi-directional micro-motion more realistically and effectively.

2. Due to the accurate positioning of the electromagnetic exciter driving the test piece on the spherical surface and the piezoelectric ceramic actuator driving the sample below the plane, the actuation range is small, the frequency is high (300Hz), the precision is high, and they are independent; Realize the tangential and radial multi-directional compound micro-motion of the upper and lower specimens according to their respective set small displacement amplitudes (up to 100nm); under the control of the data acquisition system, the set value can also be accurately applied. Normal load, so as to accurately realize the torsional compound fretting friction and wear test under the condition of given parameters.

3. The electromagnetic exciter that drives the test piece on the spherical surface for vertical micro-motion and the piezoelectric ceramic actuator that drives the specimen under the plane for horizontal micro-motion are independent; during the test, the amplitude of vertical micro-motion and horizontal micro-motion The frequency and frequency can be set independently and can be completely different, so that the multi-directional compound micro-motion composed of vertical micro-motion and horizontal micro-motion with different amplitudes and frequencies that cannot be realized on existing equipment can be realized. Simulation of multidirectional compound fretting.

4. The force sensor one connected to the upper fixture is combined with the data acquisition control system to accurately set and output the vertical load during multi-directional micro-movement; the second force sensor connected to the lower fixture can accurately measure the vertical load during multi-directional micro-motion The tangential force is the friction force, so the dynamic characteristics of multi-directional fretting can be accurately characterized. And the materials after the test can be used for other relevant analysis.

In short, this test method can conveniently cause various multi-directional fretting friction and wear of materials with precise micro-displacement values. The test is directly controlled by the data acquisition control system to set the corresponding test parameters, and measure the friction force for automatic analysis. It can more realistically simulate multi-directional fretting damage of components under alternating loads, and the experimental results are more accurate and reliable; the precision of control and testing is high, the reproducibility of experimental data is good, and the degree of automation is high. It overcomes the defects of singleness and poor reproducibility of the results of the existing experimental methods.

Another object of the present invention is to provide a test device for implementing the above-mentioned multi-directional fretting friction fatigue test method, the device is simple in structure, easy to operate, and can carry out multi-directional fretting friction and wear tests of different working conditions and specification materials, The precision of control and test is high, and the experimental data is more accurate, reliable and reproducible.

The technical solution adopted by the present invention to realize the object of the invention is: a test device implementing the above-mentioned test method, which is composed of an electromagnetic excitation drive device, a piezoelectric excitation drive device, a data acquisition control system and a support, wherein:

The specific composition of the electromagnetic excitation driving device is as follows: the upper fixture is a fixture for clamping the spherical upper test piece, and the vertical centerline of the clamping cavity of the upper fixture is aligned with the axis of the electromagnetic excitation actuator and passed through the force sensor One is connected; the electromagnetic excitation actuator is connected with the motor fixed on the top plate of the machine base through the cylindrical cam mechanism; the motor, the electromagnetic excitation actuator and the force sensor are all electrically connected with the data acquisition control system.

The specific composition of the piezoelectric excitation drive device is as follows: the lower fixture is a fixture for clamping the specimen under the plane, and the horizontal centerline of the clamping cavity of the lower fixture is aligned with the axis of the piezoelectric ceramic actuator and passed through the load cell. The two are connected, the piezoelectric ceramic actuator is connected to the side wall of the horizontal moving platform; one side of the horizontal moving platform is connected to the linear motor fixed on the longitudinal moving plate; the horizontal slider at the bottom of the horizontal moving platform is embedded in the longitudinal moving plate in the horizontal chute; the longitudinal slider at the bottom of the longitudinal moving plate is embedded in the longitudinal chute of the bottom plate of the machine base, and is positioned by the positioning screw on the longitudinal moving plate; the linear motor, piezoelectric ceramic actuator and measuring Both force sensors are electrically connected with the data acquisition control system.

The use method and working process of this device are:

The spherical upper specimen is fixed on the upper fixture, and the flat lower specimen is fixed on the lower fixture. Control the linear motor to drive the lateral movement of the horizontal moving pedestal through the data acquisition control system, and adjust the longitudinal position of the longitudinal moving plate by moving the position of the longitudinal slider of the longitudinal moving plate, so that the test point of the lower specimen is in line with the center of the upper specimen Align vertically. Then, the rotation position of the cylindrical cam in the motor-driven cylindrical cam mechanism is controlled by the data acquisition control system, so that the upper test piece moves downward to contact the lower test piece, and under the feedback of the force sensor one, the upward test piece Apply the given vertical load.

Then the data acquisition and control system controls the electromagnetic exciter to make the upper test piece reciprocate up and down (radial) according to the set parameters (amplitude, frequency); at the same time, the data acquisition and control system controls the piezoelectric ceramic actuator to make the lower test piece The parts perform lateral (tangential) reciprocating micromotion according to the set parameters (amplitude, frequency). Realize the ball-plane multi-directional micro-motion of the lower and upper specimens. During this process, the force sensor 2 monitors the tangential force (friction force) during the multi-directional micro-motion in real time, and sends it to the data acquisition and control system for processing to obtain the friction force - Displacement amplitude (F _t -D) curve. At the same time, the force sensor 1 also feeds back the vertical (radial) load monitored in real time to the data acquisition and control system, and the data acquisition and control system performs real-time feedback adjustment and control on the vertical position of the upper fixture to ensure the correctness of the upper specimen. The axial load is always at a constant given value.

Given different parameters (parameters of radial fretting and tangential fretting can be given independently), multi-directional fretting friction and wear tests under different working conditions can be carried out. For upper and lower test pieces of different sizes, upper and lower fixtures of corresponding specifications can be used.

It can be seen that the above device can conveniently and automatically realize the test method of the present invention according to the set conditions, and can carry out multi-directional fretting friction and wear tests of different working conditions and specifications of materials, and more realistically simulate the components under alternating loads. The multi-directional fretting damage under the action has high control and test precision, and the experimental data is more accurate, reliable and reproducible.

Description of drawings

Fig. 1 is a front view structural schematic diagram of an embodiment of the present invention.

Fig. 2 is a left view structural diagram of an embodiment of the present invention.

Detailed ways

Fig. 1, Fig. 2 show that a kind of specific embodiment of the present invention is, a kind of multidirectional fretting fatigue test method, and its practice is:

a. Connect the upper fixture 5 and the electromagnetic excitation actuator 3 through the load cell 4, and the vertical centerline of the clamping cavity of the upper fixture 5 is aligned with the axis of the electromagnetic excitation actuator 3, and use the upper fixture 5 Clamp the spherical upper test piece 6; then connect the lower fixture 9 with the piezoelectric ceramic actuator 11 through the force sensor 2 10, and the horizontal centerline of the clamping cavity of the lower fixture 9 and the piezoelectric ceramic actuator 11 Centering the shaft, use the lower fixture 9 to clamp the plane lower test piece 7; and align the center of the upper test piece with the test point of the lower test piece;

b. Make the upper and lower test pieces 6 and 7 contact, and under the feedback of the load cell 4, the data acquisition control system controls the upper test piece 6 to apply a set vertical load; then the data acquisition control system simultaneously controls the electromagnetic The actuation of the exciting actuator 3 and the piezoelectric ceramic actuator 11 makes the upper fixture 5 and the upper specimen 6 held by it vertically reciprocate with the set amplitude and reciprocating times, and the lower fixture 9 and its clamped The lower test piece 7 reciprocates horizontally with the set amplitude and reciprocating times to realize multi-directional fretting friction between the upper and lower test pieces;

c. While multi-directional fretting friction occurs on the upper and lower test pieces 6 and 7, the friction force is measured through the force sensor 2 10 connected to the lower fixture 9, and sent to the data acquisition and control system for analysis.

In order to realize the above test method more conveniently and quickly, the specific composition of the test device used in this example is as follows:

Fig. 1, Fig. 2 show, implement the multidirectional fretting fatigue testing machine of above-mentioned test method, it is made of electromagnetic excitation driving device, piezoelectric excitation driving device, data acquisition control system and support 15, wherein:

The specific composition of the electromagnetic excitation driving device is as follows: the upper fixture 5 is a fixture for clamping the spherical upper test piece 6, and the vertical centerline of the clamping cavity of the upper fixture 5 is aligned with the axis of the electromagnetic excitation actuator 3 and Connected by a force sensor-4; the electromagnetic excitation actuator 3 is connected with the motor 1 fixed on the top plate 15A of the machine base 15 through a cylindrical cam mechanism 2; the motor 1, the electromagnetic excitation actuator 3 and the force sensor-4 Both are electrically connected with the data acquisition control system.

The specific composition of the piezoelectric excitation driving device is as follows: the lower fixture 9 is a fixture for clamping the plane lower test piece 7, and the horizontal centerline of the clamping cavity of the lower fixture 9 is aligned with the axis of the piezoelectric ceramic actuator 11 and Connected by load cell 2 10, the piezoelectric ceramic actuator 11 is connected with the side wall 12A of the horizontally moving pedestal 12; one side of the horizontally moving pedestal 12 is connected with the linear motor 8 fixed on the longitudinal moving plate 13; the horizontally moving pedestal The horizontal slider 12B at the bottom of 12 is embedded in the horizontal chute of the longitudinally moving plate 13; the longitudinal slider 13A at the bottom of the longitudinally moving plate 13 is embedded in the longitudinal chute of the bottom plate 15B of the machine base 15, and is moved by the vertically moving plate The positioning screw on 13 realizes the positioning; the linear motor 8, the piezoelectric ceramic actuator 11 and the load cell 10 are all electrically connected with the data acquisition control system.

The maximum load of the electromagnetic excitation actuator 3 used in this example: 3000N, the precision is 0.5; the load cell 4: 3000N (x/y/z direction load); the displacement range: 0.1-200μm; the precision is not less than 0.1μm; Servo frequency: not less than 100Hz.

The maximum load of the piezoelectric ceramic actuator 11 used in this example: 1000N, the precision is 0.5; the displacement range: 0.1-100μm; the precision is not lower than 0.1μm; the servo frequency is not lower than 300Hz.

The translational displacement range of the linear motor 8 used in this example: 0.1-10mm; displacement accuracy: 1 μm.

Claims (2)

1. A multi-directional fretting fatigue test method, its practice is: a. Connect the upper fixture (5) and the electromagnetic excitation actuator (3) through the load cell one (4), and the vertical centerline of the clamping cavity of the upper fixture (5) is connected to the electromagnetic excitation actuator (3) ), use the upper fixture (5) to clamp the spherical upper test piece (6); then connect the lower fixture (9) to the piezoelectric ceramic actuator (11) through the load cell 2 (10), And the horizontal centerline of the clamping cavity of the lower fixture (9) is aligned with the axis of the piezoelectric ceramic actuator (11), and the lower test piece (7) is clamped by the lower fixture (9); and the upper test piece The center of the center is aligned with the test point of the lower specimen; b. Make the upper and lower test pieces (6, 7) contact, and under the feedback of load cell one (4), the data acquisition control system controls the upper test piece (6) to apply a set vertical load P; then The data acquisition and control system simultaneously controls the actuation of the electromagnetic excitation actuator (3) and the piezoelectric ceramic actuator (11), so that the upper fixture (5) and the upper specimen (6) held by it and reciprocating times vertically reciprocating, the lower fixture (9) and the lower specimen (7) clamped by it reciprocate horizontally with the set amplitude and reciprocating times to realize multi-directional fretting friction between the upper and lower specimens; c. While multi-directional fretting friction occurs on the upper and lower test pieces (6, 7), the friction force is measured through the load cell 2 (10) connected to the lower fixture (9), and sent to the data acquisition and control system for analysis. 2. a multi-directional fretting fatigue testing machine implementing the test method described in claim 1, it is made of electromagnetic excitation driving device, piezoelectric excitation driving device, data acquisition control system and support (15), wherein : The specific composition of the electromagnetic excitation driving device is as follows: the upper fixture (5) is a fixture for clamping the spherical upper test piece (6), and the vertical centerline of the clamping cavity of the upper fixture (5) and the electromagnetic excitation actuator The shaft of (3) is centered and connected by load cell one (4); the electromagnetic excitation actuator (3) is fixed on the motor on the top plate (15A) of the support (15) through the cylindrical cam mechanism (2) (1) are connected; the motor (1), the electromagnetic excitation actuator (3) and the load cell one (4) are all electrically connected with the data acquisition control system. The specific composition of the piezoelectric excitation driving device is as follows: the lower fixture (9) is a fixture for clamping the lower test piece (7) on the plane, and the horizontal centerline of the clamping cavity of the lower fixture (9) and the piezoelectric ceramic actuator The axis of (11) is centered and connected by load cell two (10), and the piezoelectric ceramic actuator (11) is connected with the side wall (12A) of the horizontally moving pedestal (12); one of the horizontally moving pedestal (12) The side is connected with the linear motor (8) fixed on the vertical moving plate (13); the horizontal sliding block (12B) at the bottom of the horizontal moving pedestal (12) is embedded in the horizontal chute of the vertical moving plate (13); the vertical moving The longitudinal slider (13A) at the bottom of the plate (13) is fitted in the longitudinal chute of the bottom plate (15B) of the support (15), and is positioned by the positioning screw on the longitudinally moving plate (13); the linear motor (8 ), the piezoelectric ceramic actuator (11) and the load cell two (10) are all electrically connected with the data acquisition control system.

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