CN113588263A - Fatigue test system and method for hub bearing unit structure - Google Patents
Fatigue test system and method for hub bearing unit structure Download PDFInfo
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Abstract
The invention discloses a fatigue test system and method for a hub bearing unit structure, and relates to the field of hub bearing fatigue detection. The system comprises a base, a bottom tool, a test hub bearing unit, a switching disc, a strain bridge, a loading arm, a vertical rod, an auxiliary mounting tool, a locking nut, an eccentric inner ring, a rolling body, an outer ring, a flexible shaft, a servo motor and a cross beam. The test method comprises load calibration, rotation frequency determination, loading test and failure determination. The fatigue test system for the hub bearing structure provided by the invention can be used for well and accurately evaluating the fatigue life of the hub bearing structure, and the problem that a ground test cannot be carried out due to the contact fatigue failure of the raceway of the test bearing is solved. Meanwhile, the electric drive loading mode is adopted, so that the device has the good characteristics of simple and reliable structure, accurate and stable loading, convenience in maintenance and timeliness in failure judgment.
Description
Technical Field
The invention relates to the field of fatigue detection of hub bearings, in particular to a system and a method for fatigue test of a hub bearing unit structure.
Background
A Hub bearing unit (Hub bearing unit) is a bearing applied to a wheel to bear the weight of a vehicle body and transmit power, and is called a Hub bearing unit because a flange connected to a brake disc and a Hub is integrated with the bearing.
Structural fatigue (structural fatigue) refers to the phenomenon of material failure in the flange Structure of a hub bearing under long-term bending cycles in application.
The following 2 schemes are provided for the fatigue test of the hub bearing unit structure in the prior art:
in the scheme 1, the Chinese patent invention 200420075349.3 discloses a bending fatigue testing machine for an automobile hub bearing. The hub bearing unit is arranged on the test main shaft, the hub bearing unit rotates in the test process, the two sides of the hub bearing unit are respectively connected with the radial loading mechanism and the axial loading mechanism, radial load and axial load are applied to the test bearing, the loading radius and offset are consistent with the state that the test bearing is arranged on a real vehicle, and the bending moment of the test bearing is obtained by superposing the loads in the two directions. The loading mechanism adopted by the test system is in a hydraulic mode, and the loading mechanism is connected with a loading force arm through a spherical hinge to keep certain loading flexibility. In the test process, the fatigue failure of the hub bearing unit occurs under the long-term action of the bending moment load, and the failure is monitored through the change of the vibration acceleration.
The defects are as follows: under the working condition of bending moment formed by loads in two specific directions, the test bearing is easy to generate contact fatigue stripping of the raceway under the long-term rotating working condition of the test bearing, and the structural fatigue life of the flange plate is difficult to evaluate due to the termination of the test caused by the contact fatigue. The test bed is applied to a large number of spherical hinge joints, and joint abrasion is easy to occur in a dynamic operation test to influence loading accuracy. At the same time, the use of hydraulic loading increases the complexity of hydraulic system maintenance.
In the proposal 2, the Chinese patent 201621028812.8 discloses a bending fatigue testing machine for a hub bearing unit. The hub bearing unit is installed on the base, the hub bearing unit is fixed and does not rotate in the test process, the two sides of the hub bearing unit are respectively connected with the radial loading mechanism and the axial loading mechanism, radial load and axial load are applied to the test bearing at a certain frequency, the loading radius and offset are consistent with the state that the test bearing is installed on a real vehicle, and the bending moment of the test bearing is obtained by superposing the loads in two directions. The loading mechanism adopted by the test system is in a hydraulic mode, and the loading mechanism is connected with a loading force arm through a spherical hinge to keep certain loading flexibility. In the test process, the fatigue failure of the hub bearing unit under the long-term action of the bending moment load is monitored through the indication value change of a metal densimeter connected with the bearing.
The defects are as follows: compared with the scheme 1, the scheme has the difference that the bearing does not rotate, which also brings a problem that the specific frequency is adopted to apply the load, the load only can accord with the characteristics of sine wave law, the uniform load of the structural member cannot be ensured, and the difference with the actual load of the hub bearing is larger. According to the scheme, a large number of spherical hinge joints are still adopted, and joint abrasion under specific frequency loading influences loading accuracy. The hydraulic loading is adopted, so that the maintenance complexity of a hydraulic system is increased, and meanwhile, the timeliness of failure judgment of the applied metal densimeter is poor.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a fatigue test system for a hub bearing unit structure, which is used for accurately simulating the actual loading bending moment of a hub bearing unit and realizing accurate and stable application of the test bending moment load; the adoption of the spherical hinge joint is abandoned, and the problem of reduced loading accuracy caused by the abrasion of the spherical hinge joint is solved; the fatigue life of the hub bearing unit structure is accurately evaluated, and the problem that the fatigue life of the structure cannot be evaluated because the test cannot be continued due to early fatigue of the raceway is thoroughly solved; the hydraulic loading is not adopted, and the electric driving loading scheme is adopted to eliminate the difficulty and complexity of the maintenance of the hydraulic system.
The purpose of the invention is achieved by the following technical scheme: a fatigue test system for a hub bearing unit structure comprises a base, a bottom tool, a test hub bearing unit, a switching disc, a strain bridge, a loading arm, a vertical rod, an installation auxiliary tool, a locking nut, an eccentric inner ring, a rolling body, an outer ring, a flexible shaft, a servo motor and a cross beam, wherein the base is arranged on the horizontal ground, the bottom of the bottom tool is fixedly arranged on the base through bolts, the test hub bearing unit is arranged on the bottom tool, the top of the bottom tool is fixedly locked with a flange plate of the test hub bearing unit, the outer ring of the test hub bearing unit is sleeved with the switching disc which is connected through bolts, the top of the switching disc is fixedly connected with the bottom end of the loading arm, four strain discs are uniformly distributed on the circumference of an arm body of the loading arm, the four strain discs are mutually bridged to jointly form the strain bridge, and the strain bridge is electrically connected with an external data acquisition system, thereby acquiring strain data of the loading arm in real time; the vertical rod is fixed on the base in the vertical direction, the mounting auxiliary tool is mounted on the vertical rod through the guide rail, so that the mounting auxiliary tool can move in the vertical direction along the vertical rod, and the guide rail selectively locks and fixes the mounting auxiliary tool and the vertical rod; the mounting auxiliary tool is provided with a positioning hole, and the arm body of the loading arm penetrates through the positioning hole to realize positioning; the beam is fixed on the horizontal ground, the servo motor is suspended and fixed at the top of the beam along the vertical direction and is used for driving the eccentric inner ring to rotate, an output shaft of the servo motor is connected with an input end of the flexible shaft for transmission, the eccentric inner ring is sleeved at an output end of the flexible shaft and fixed by a locking nut, and the eccentric inner ring is connected with the outer ring through the rolling body to realize rolling bearing type contact; the outer ring is locked and fixed at the top end of the loading arm through a bolt.
As a further technical scheme, an eccentric mass block is arranged on the outer edge of the eccentric inner ring.
As a further technical scheme, clearance fit is adopted between the mounting auxiliary tool and the loading arm.
As a further technical solution, the height H3 of the adapter plate is adjusted according to the height H4 of the test hub bearing unit, and the total height H2 of the two is kept constant; the height of the loading arm is constant, so that the total height H of the loading arm, the adapter plate and the test hub bearing unit is constant; the height H1 of the bottom tooling also remains constant.
As a further technical solution, the strain gauge includes a first strain gauge, a second strain gauge, a third strain gauge and a fourth strain gauge, and adjacent strain gauges are spaced by 90 °.
A fatigue test method for a hub bearing unit structure comprises the following steps:
1) load calibration: slowly applying a radial load F to the loading arm at a position H above the bottom tool, and simultaneously detecting the Strain Strain of the loading arm in real time through a Strain bridge to obtain a relation function of the Strain Strain and a bending moment M, wherein the bending moment M is F H;
2) and (3) determining the rotation frequency: starting a servo motor, arranging an eccentric mass block with mass m at the outer edge of the eccentric inner ring, wherein the eccentric mass block is away from the rotation center of the eccentric inner ring by a distance r, namely the rotation radius r, and during the driving rotation, the rotation angular velocity of the eccentric mass block is omega, the rotation frequency is F, and the following centrifugal acting force Fbias is generated:
Fdeflection＝ω2r＝m(2π*f)2r
Bending moment M generated by eccentric mass block under working stateDeflectionComprises the following steps:
Mdeflection＝FDeflection*H＝m(2π*f)2r H
Setting a test loading bending moment M0, controlling a servo motor to gradually increase the rotation frequency of an eccentric inner ring so as to increase the rotation frequency f of an eccentric mass block, simultaneously measuring a Strain Strain of a loading arm through a Strain bridge, obtaining an actual loading bending moment M1 of the loading arm according to a relation function of the Strain Strain and the bending moment M, and when the actual loading bending moment M1 is equal to the test loading bending moment M0, the rotation frequency f of the eccentric mass block is not increased any more and is fixed at the moment and the rotation frequency f1 is fixed;
3) and (3) loading test: keeping the eccentric inner ring rotating at the frequency f1 obtained in the step 2), monitoring the actual loading bending moment M1 of the loading arm in real time through a strain bridge, and keeping the actual loading bending moment M1 consistent with the test loading bending moment M0;
4) failure determination: when the test hub bearing unit has cracks, the rotating radius r of the eccentric mass block on the eccentric inner ring is increased, the servo motor is controlled to adjust the rotating frequency of the eccentric inner ring, the rotating frequency of the eccentric mass block is reduced to ensure that the actual loading bending moment M1 is consistent with the test loading bending moment M0, the rotating frequency of the eccentric mass block after reduction is f2, the difference value between f1 and f2 is delta f, when the delta f is larger than the warning value, the servo motor stops working, the test is stopped, and an operator takes down the test hub bearing unit for crack inspection.
As a further technical scheme, the radial load F applied in step 1) is at least kept on the same side and the same interface with the center of one of the four strain gauges, and load calibration of the first strain gauge, the second strain gauge, the third strain gauge and the fourth strain gauge is performed in sequence.
As a further technical scheme, the alarm value of the delta f in the step 4) is more than or equal to 1Hz, and preferably is 2 Hz.
The invention has the beneficial effects that:
1. the load rotation mode is adopted to replace a hub bearing rotation mode, so that the 360-degree omnibearing load application of the bearing is realized, the accurate simulation of the actual working condition is achieved, the accurate evaluation of the structural fatigue life is realized, and the problem that the structural fatigue life cannot be judged because the test caused by the early fatigue of the raceway cannot be continued is solved;
2. a non-joint loading connection mode is adopted, so that the problem of reduced loading accuracy caused by the abrasion of a spherical hinge joint is solved;
3. an electric drive loading mode is adopted, so that the operation and the maintenance are simple and convenient;
4. and a new failure crack monitoring method is adopted in a matched manner, and the occurrence time point of the structural fatigue of the hub bearing unit is accurately judged.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a schematic structural diagram of load calibration.
FIG. 3 is a schematic structural diagram of a strain bridge and a strain gauge.
Fig. 4 is a schematic view of an installation structure of the eccentric mass block and the eccentric inner ring.
Fig. 5 is a force diagram of the eccentric mass.
Fig. 6 is a graph of experimental monitoring.
Fig. 7 is a graph of the number of test cycles versus the drive rotation frequency.
Description of reference numerals: the device comprises a base 1, a bottom tool 2, a test hub bearing unit 3, an adapter plate 4, a strain bridge 5, a loading arm 6, a vertical rod 7, an auxiliary mounting tool 8, a locking nut 9, an eccentric inner ring 10, a rolling body 11, an outer ring 12, a flexible shaft 13, a servo motor 14, a cross beam 15, a strain gauge 16, a guide rail 17, a positioning hole 18, an eccentric mass block 19, a first strain gauge G1, a second strain gauge G2, a third strain gauge G3 and a fourth strain gauge G4.
Detailed Description
The invention will be described in detail below with reference to the following drawings:
example (b): as shown in the attached figure 1, the fatigue test system for the hub bearing unit structure comprises a base 1, a bottom tool 2, a test hub bearing unit 3, an adapter plate 4, a strain bridge 5, a loading arm 6, a vertical rod 7, an installation auxiliary tool 8, a lock nut 9, an eccentric inner ring 10, a rolling body 11, an outer ring 12, a flexible shaft 13, a servo motor 14 and a cross beam 15, wherein the base 1 is arranged on a horizontal ground, the bottom of the bottom tool 2 is fixedly arranged on the base 1 through bolts, the test hub bearing unit 3 is arranged on the bottom tool 2, the top of the bottom tool 2 is fixedly locked with a flange plate of the test hub bearing unit 3, the adapter plate 4 is sleeved on the outer ring of the test hub bearing unit 3 and is fixedly connected through bolts, the top of the adapter plate 4 is fixedly connected to the bottom end of the loading arm 6, four strain gages 16 are uniformly distributed along the circumference of the arm body of the loading arm 6, the four strain gages 16 are mutually bridged to jointly form the strain bridge 5, the strain bridge 5 is electrically connected with an external data acquisition system so as to acquire strain data of the loading arm 6 in real time; the vertical rod 7 is fixed on the base 1 along the vertical direction, the mounting auxiliary tool 8 is mounted on the vertical rod 7 through the guide rail 17, so that the vertical rod 7 moves in the vertical direction, and the mounting auxiliary tool 8 and the vertical rod 7 are selectively locked and fixed through the guide rail 17; the mounting auxiliary tool 8 is provided with a positioning hole 18, and the arm body of the loading arm 6 penetrates through the positioning hole 18 to realize positioning; the cross beam 15 is fixed on the horizontal ground, the servo motor 14 is suspended and fixed at the top of the cross beam 15 along the vertical direction and used for driving the eccentric inner ring 10 to rotate, an output shaft of the servo motor 14 is connected with an input end of the flexible shaft 13 for transmission, the eccentric inner ring 10 is sleeved at an output end of the flexible shaft 13 and fixed by the locking nut 9, and the eccentric inner ring 10 is connected with the outer ring 12 through the rolling body 11 to realize rolling bearing type contact; the outer ring 12 is secured to the top end of the loading arm 6 by bolting.
Preferably, an eccentric mass 19 is arranged on the outer edge of the eccentric inner ring 10. And the mounting auxiliary tool 8 is in clearance fit with the loading arm 6. The height H3 of the adapter plate 4 is adjusted according to the height H4 of the test hub bearing unit 3, and the total height H2 of the two is kept constant; the height of the loading arm 6 is constant, so that the total height H of the loading arm 6, the adapter plate 4 and the test hub bearing unit 3 is constant; the height H1 of the bottom tooling 2 also remains constant. The strain gauges 16 include a first strain gauge G1, a second strain gauge G2, a third strain gauge G3 and a fourth strain gauge G4, with a 90 ° spacing between adjacent strain gauges 16.
Referring to fig. 2 to 4, a fatigue test method for a hub bearing unit structure includes the following steps:
1) load calibration: at a position H above the bottom tooling 2, a radial load F is slowly applied to the loading arm 6, and the applied radial load F is maintained at least at the same interface on the same side as the center of one strain gage 16 of the four strain gages 16, and load calibration of the first strain gage G1, the second strain gage G2, the third strain gage G3 and the fourth strain gage G4 is performed in this order. Detecting the Strain of the loading arm 6 in real time through a Strain bridge 5 to obtain a relation function of the Strain and a bending moment M, wherein the bending moment M is F H;
2) and (3) determining the rotation frequency: starting the servo motor 14, and arranging an eccentric mass block 19 with mass m at the outer edge of the eccentric inner ring 10, wherein the distance of the eccentric mass block 19 from the rotation center of the eccentric inner ring 10 is r, that is, the rotation radius is r, during the driving rotation, the rotation angular velocity of the eccentric mass block 19 is ω, and the rotation frequency is F, the following centrifugal acting force fset will be generated:
Fdeflection＝ω2r＝m(2π*f)2r
Bending moment M generated by the eccentric mass block 19 in the working stateDeflectionComprises the following steps:
Mdeflection＝FDeflection*H＝m(2π*f)2r H
Setting a test loading bending moment M0, controlling the servo motor 14 to gradually increase the rotation frequency of the eccentric inner ring 10 so as to increase the rotation frequency f of the eccentric mass block 19, simultaneously measuring the Strain Strain of the loading arm 6 through the Strain bridge 5, obtaining the actual loading bending moment M1 of the loading arm 6 according to the relation function of the Strain Strain and the bending moment M, and when the actual loading bending moment M1 is equal to the test loading bending moment M0, the rotation frequency f of the eccentric mass block 19 is not increased any more and is fixed at the moment, namely the rotation frequency f 1;
3) and (3) loading test: keeping the eccentric inner ring 10 rotating at the frequency f1 obtained in the step 2), monitoring the actual loading bending moment M1 of the loading arm 6 in real time through the strain bridge 5, and keeping the actual loading bending moment M1 consistent with the test loading bending moment M0;
4) failure determination: when the test hub bearing unit 3 cracks, the rotation radius r of the eccentric mass block 19 on the eccentric inner ring 10 is increased, at this time, the servo motor 14 is controlled to adjust the rotation frequency of the eccentric inner ring 10, so that the rotation frequency of the eccentric mass block 19 is reduced to ensure that the actual loading bending moment M1 is consistent with the test loading bending moment M0, the rotation frequency of the eccentric mass block 19 after reduction is f2, the difference value between f1 and f2 is delta f, when the delta f is larger than the warning value and is set to be 2Hz, the servo motor 14 stops working, the test is stopped, and an operator takes off the test hub bearing unit 3 for crack inspection.
The working process of the invention is as follows:
referring to fig. 1, in a state where the servo motor 14 is not in operation, the auxiliary mounting tool 8 is pushed upward along the vertical rod 7 in a vertical direction until the upper end surface of the auxiliary mounting tool 8 abuts against the end surface of the loading arm 6 and is lifted upward by a distance of 15mm, so that the self weight of the loading arm 6 is completely borne by the auxiliary mounting tool 8, and at this time, the loading arm 6 is suspended, and a sufficient installation space for the test specimen and the tool is reserved below the loading arm. The bottom tool 2 and the base 1 are fastened and connected by 6 bolts of M14 multiplied by 1.5 at the lower part, and the locking torque of each bolt is 50N M +90 degrees. And the test hub bearing unit 3 and the bottom tool 2 are tightly connected by adopting 5M 14 multiplied by 1.5 bolts, and the locking torque of each bolt is 130 N.m. The adapter plate 4 and the test hub bearing unit 3 are fastened and connected by adopting 3M 14 multiplied by 1.5 bolts, and the locking torque is 120 N.m.
Next, the mounting aid 8 is slowly lowered down along the vertical direction of the vertical rod 7, so that the lower end surface of the loading arm 6 is attached to the upper end surface of the adapter plate 4, and the loading arm 6 is locked and connected to the adapter plate 4 by using 6M 14 × 1.5 bolts, and the locking torque is 50N · M +90 °. After the work is finished, the auxiliary mounting tool 8 is moved downwards by a distance of 10mm along the vertical direction of the vertical rod 7, so that the auxiliary mounting tool 8 is not in contact with the loading arm 6, and the influence on loading in the test process is avoided.
Referring to fig. 2, the total height of the working area of the test system is H + H1-515 mm, which is a fixed value, and the total height of the working area of the test system is composed of the height H of the loading arm of 450mm and the thickness H1 of the bottom fixture 2 of 65 mm. When H2 is a constant value of 110mm and the height H4 of the test hub bearing unit 3 is 50mm, the H3 design value is 60 mm.
Referring to fig. 2, a loading mechanism is used to slowly apply a radial load F to the loading arm 6 at a location H450 mm above the loading arm 6. The loading operation is performed at every 90 ° position in the circumferential direction in sequence. Referring to fig. 3, 4 strain gauges 16(G1, G2, G3, G4) are disposed under the loading arm 6. The applied radial load F remains at least on the same side interface as the center of one strain gage 16 of the 4 strain gages 16(G1, G2, G3, G4).
During the application of the radial load F, the strain gauges 16(G1, G2, G3, G4) are able to sense the deformation and measure the acquired strain data. Load calibration of the Strain gauges G1, G2, G3 and G4 is carried out in sequence, and a relation function of Strain and bending moment M, F and H is obtained, and the relation function is as follows:
through linear fitting, the relationship function of the strain X and the bending moment M acquired to the strain gages G1, G2, G3 and G4 is as follows:
the first strain gauge G1 calibrates the function:
M＝0.0842X+3.1026；
the second strain gauge G2 calibrates the function:
M＝0.0891X+5.1982；
the third strain gauge G3 calibrates the function:
M＝0.0873X+7.0711；
the fourth strain gage G4 calibrates the function:
M＝0.0834X+5.0509。
and introducing the 4 functional formulas into measurement and control software, and applying the measurement and control software to the actual test load application in the structural fatigue test of the test hub bearing unit 3. Not every test sample is tested requiring load calibration, a 1 year calibration is a good choice.
Referring to fig. 1, after the test sample is mounted, the test hub bearing unit 3, the adapter plate 4, the strain bridge 5 (including G1, G2, G3 and G4) and the loading arm 6 are all static and do not rotate in the whole test process. The servo motor 14 is started through a measurement and control system, and the servo motor 14 transmits power to the eccentric inner ring 10 through the flexible shaft 13. Referring to fig. 4 and 5, the eccentric inner ring 10 is provided with an eccentric mass 19 having a mass m of 2000g at an outer edge, and the eccentric mass 19 is spaced from the rotation center of the eccentric inner ring 10 by a distance r, i.e., a rotation radius r of 58 mm.
During the continuous test, four strain gauges 16(G1, G2, G3, G4) will continuously monitor the change of the actual bending moment of the test, as shown in FIG. 6 which is a test monitoring graph.
During the test, the change of the test rotation frequency f was continuously monitored, and when the test continued for 235 ten thousand cycles, the rotation frequency had a tendency to decrease, and when the rotation frequency decreased from the initial 27.3Hz to 25.2Hz, the rotation frequency decreased by Δ f — 2.1Hz, as shown in fig. 7.
The frequency drop alarm limit set by the test system software is 2Hz, and after the test bearing is tested for 239 ten thousand times, the test system alarms and stops, and the structural crack failure of the tested object is judged. The test sample is inspected by a tester, and two cracks are found at the root of the turning part of the disc surface of the flange plate of the test hub bearing unit 3.
And finishing the structural fatigue test of the test hub bearing unit 3, and determining that the structural fatigue life of the test hub bearing unit under the working condition that the bending moment M is 1500 N.m is 239 ten thousand times.
The fatigue test system for the hub bearing structure provided by the invention can be used for well and accurately evaluating the fatigue life of the hub bearing structure, and the problem that a ground test cannot be carried out due to the contact fatigue failure of the raceway of the test bearing is solved. Meanwhile, the electric drive loading mode is adopted, so that the device has the good characteristics of simple and reliable structure, accurate and stable loading, convenience in maintenance and timeliness in failure judgment.
It should be understood that equivalent substitutions and changes to the technical solution and the inventive concept of the present invention should be made by those skilled in the art to the protection scope of the appended claims.
Claims (8)
1. The utility model provides a wheel hub bearing unit structure fatigue test system which characterized in that: the device comprises a base (1), a bottom tool (2), a test hub bearing unit (3), a switching disc (4), a strain bridge (5), a loading arm (6), a vertical rod (7), an installation auxiliary tool (8), a locking nut (9), an eccentric inner ring (10), a rolling body (11), an outer ring (12), a flexible shaft (13), a servo motor (14) and a cross beam (15), wherein the base (1) is arranged on the horizontal ground, the bottom of the bottom tool (2) is fixedly arranged on the base (1), the test hub bearing unit (3) is arranged on the bottom tool (2), the top of the bottom tool (2) is fixedly locked with a flange plate of the test hub bearing unit (3), the outer ring of the test hub bearing unit (3) is sleeved with the switching disc (4), the top of the switching disc (4) is fixedly connected to the bottom end of the loading arm (6), four strain discs (16) are uniformly distributed along the circumference of an arm body of the loading arm (6), the four strain gauges (16) are mutually bridged to form the strain bridge (5), and the strain bridge (5) is electrically connected with an external data acquisition system so as to acquire strain data of the loading arm (6) in real time; the vertical rod (7) is fixed on the base (1) along the vertical direction, the mounting auxiliary tool (8) is mounted on the vertical rod (7) through the guide rail (17) so as to move along the vertical rod (7) in the vertical direction, and the mounting auxiliary tool (8) and the vertical rod (7) are selectively locked and fixed by the guide rail (17); a positioning hole (18) is formed in the mounting auxiliary tool (8), and the arm body of the loading arm (6) penetrates through the positioning hole (18) to realize positioning; the cross beam (15) is fixed on the horizontal ground, the servo motor (14) is suspended and fixed at the top of the cross beam (15) along the vertical direction and used for driving the eccentric inner ring (10) to rotate, an output shaft of the servo motor (14) is connected and driven with an input end of the flexible shaft (13), an output end of the flexible shaft (13) is sleeved with the eccentric inner ring (10) and fixed by a locking nut (9), and the eccentric inner ring (10) is connected with the outer ring (12) through the rolling body (11) to realize rolling bearing type contact; the outer ring (12) is locked and fixed at the top end of the loading arm (6).
2. The hub-bearing unit structural fatigue testing system of claim 1, wherein: an eccentric mass (19) is arranged on the outer edge of the eccentric inner ring (10).
3. The hub-bearing unit structural fatigue testing system of claim 1, wherein: the installation auxiliary tool (8) is in clearance fit with the loading arm (6).
4. The hub-bearing unit structural fatigue testing system of claim 1, wherein: the height H3 of the adapter plate (4) is adjusted according to the height H4 of the test hub bearing unit (3), and the total height H2 of the adapter plate and the test hub bearing unit is kept constant; the height of the loading arm (6) is constant, so that the total height H of the loading arm (6), the adapter plate (4) and the test hub bearing unit (3) is constant; the height H1 of the bottom tooling (2) is also kept constant.
5. The hub-bearing unit structural fatigue testing system of claim 1, wherein: the strain gauges (16) comprise a first strain gauge (G1), a second strain gauge (G2), a third strain gauge (G3) and a fourth strain gauge (G4), and adjacent strain gauges (16) are spaced by 90 degrees.
6. A fatigue test method for a hub bearing unit structure is characterized by comprising the following steps: the method comprises the following steps:
1) load calibration: slowly applying a radial load F to the loading arm (6) at a position H above the bottom tool (2), and simultaneously detecting the Strain Strain of the loading arm (6) in real time through the Strain bridge (5) to obtain a relation function of the Strain Strain and a bending moment M, wherein the bending moment M is F H;
2) and (3) determining the rotation frequency: starting the servo motor (14), arranging an eccentric mass block (19) with mass m at the outer edge of the eccentric inner ring (10), wherein the distance between the eccentric mass block (19) and the rotation center of the eccentric inner ring (10) is r, namely the rotation radius is r, and during the driving rotation, the rotation angular velocity of the eccentric mass block (19) is omega, the rotation frequency is F, and the following centrifugal acting force Fbias is generated:
Fdeflection＝ω2r＝m(2π*f)2r
Bending moment M generated by the eccentric mass block (19) in the working stateDeflectionComprises the following steps:
Mdeflection＝FDeflection*H＝m(2π*f)2r H
Setting a test loading bending moment M0, controlling a servo motor (14) to gradually increase the rotation frequency of an eccentric inner ring (10) so as to increase the rotation frequency f of an eccentric mass block (19), simultaneously measuring a Strain string of a loading arm (6) through a Strain bridge (5), and obtaining an actual loading bending moment M1 of the loading arm (6) according to a relation function of the Strain string and the bending moment M, wherein when the actual loading bending moment M1 is equal to the test loading bending moment M0, the rotation frequency f of the eccentric mass block (19) is not increased any more and is fixed at the moment, namely the rotation frequency f 1;
3) and (3) loading test: keeping the eccentric inner ring (10) rotating at the frequency f1 obtained in the step 2), monitoring the actual loading bending moment M1 of the loading arm (6) in real time through the strain bridge (5), and keeping the actual loading bending moment M1 consistent with the test loading bending moment M0;
4) failure determination: when the test hub bearing unit (3) cracks, the rotating radius r of the eccentric mass block (19) on the eccentric inner ring (10) is increased, the servo motor (14) is controlled to adjust the rotating frequency of the eccentric inner ring (10), the rotating frequency of the eccentric mass block (19) is reduced to ensure that the actual loading bending moment M1 is consistent with the test loading bending moment M0, the rotating frequency of the reduced eccentric mass block (19) is f2, the difference value between f1 and f2 is delta f, when the delta f is larger than an alarm value, the servo motor (14) stops working and stops testing, and an operator takes down the test hub bearing unit (3) to check the cracks.
7. The fatigue test method for a hub-bearing unit structure according to claim 6, characterized in that: the radial load F applied in the step 1) is at least kept on the same interface with the center of one strain gage (16) in the four strain gages (16), and load calibration of the first strain gage (G1), the second strain gage (G2), the third strain gage (G3) and the fourth strain gage (G4) is sequentially carried out.
8. The fatigue test method for a hub-bearing unit structure according to claim 6, characterized in that: the alarm value of delta f in the step 4) is more than or equal to 1 Hz.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110831796.5A CN113588263A (en) | 2021-07-22 | 2021-07-22 | Fatigue test system and method for hub bearing unit structure |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116878878A (en) * | 2023-09-05 | 2023-10-13 | 万向钱潮股份公司 | Bearing test reinforcing and fastening device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116878878A (en) * | 2023-09-05 | 2023-10-13 | 万向钱潮股份公司 | Bearing test reinforcing and fastening device |
| CN116878878B (en) * | 2023-09-05 | 2023-11-14 | 万向钱潮股份公司 | Bearing test reinforcing and fastening device |
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