CN109799150B - Railway I-type elastic strip high-frequency fatigue testing method - Google Patents
Railway I-type elastic strip high-frequency fatigue testing method Download PDFInfo
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Abstract
A high-frequency fatigue testing method for railway I-type elastic strips. The invention provides a complete set of elastic strip three-dimensional model construction method, which is used for constructing a three-dimensional model of an elastic strip to be tested and obtaining pre-pressure Fn required by pressing the elastic strip to be tested to a correct installation position by means of finite element mechanical property analysis. Therefore, when the high-frequency fatigue test of the elastic strip is carried out, the actual performance of the elastic strip can be more truly simulated and tested, the test progress can be accelerated, and the guarantee is provided for the service performance of the railway key equipment.
Description
Technical Field
The invention relates to the field of railway equipment testing, in particular to a railway I-type elastic strip high-frequency fatigue testing method.
Background
In recent years, the railway industry in China is getting stronger, the running distance of high-speed railway in China is getting longer, the running speed is faster, the axle weight of a heavy haul railway is getting heavier, and the performance requirement on the lower foundation of the railway is getting higher. The rail clip spring system is an important part of the underlying foundation of a railway and the clip spring typically uses bolts to press the spring against the gage plate or rail. The elastic strip can press the steel rail through the elastic buckle of the elastic strip, so that certain rigidity and damping are provided for the steel rail, and sufficient buckling pressure is provided. The rail gauge, the height irregularity, the rail direction irregularity and the like of the steel rail have a certain relation with the fastening pressure of the fastener. Therefore, the fatigue performance of the fastener spring-strip system is very important.
The fatigue performance test of railway elastic strips adopts a traditional mode that a hydraulic fatigue testing machine is adopted to load under the frequency of 16 Hz. However, the low frequency fatigue test cannot reflect the stress condition of the elastic strip in the prior high-speed rail running system. Because the running speed of the high-speed rail is higher at present, the vibration frequency of the steel rail is higher than that of the prior rail, and the fastener elastic strip is correspondingly required to be subjected to higher-frequency vibration. Therefore, for the existing railway system, the test of the high-frequency fatigue of the elastic strip is more important.
When many scholars in China analyze and research the elastic strips, the used three-dimensional models are in large contact with the actual models. In the existing analysis process of the elastic strip structure, various projection methods are used for drawing, so that the three-dimensional model of the three-dimensional model based on the existing analysis is not smooth at the position where the stress is most concentrated, namely the position of the heel toe. Model deviations can cause very large deviations in the analysis results, which often exceed the material yield limit.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a railway I-type elastic strip high-frequency fatigue testing method, a testing clamp and a testing system which can improve the accuracy of the railway I-type elastic strip high-frequency fatigue testing.
Firstly, in order to achieve the purpose, a railway I-shaped elastic strip high-frequency fatigue testing method is provided, and the method comprises the following steps: step one, establishing a three-dimensional model of the elastic strip to be tested according to the size parameters of the elastic strip to be tested in the state iron standard; in the three-dimensional model, the tangent angle at the root toe of the bullet strip to be tested conforms to the size of a front view of the bullet strip to be tested in the national iron standard; the coordinate axis of the three-dimensional model takes a tangent line at the root toe of the elastic strip as an X-Y plane datum line; the vertical direction of the tangent angle of the root toe of the elastic strip is the Z axis of the three-dimensional model; the coordinate system of the three-dimensional model conforms to the right-hand rule; secondly, performing finite element analysis by using the three-dimensional model of the elastic strip to be tested to obtain the magnitude Fn of the pre-pressure under the high-frequency fatigue test corresponding to the elastic strip to be tested; the finite element analysis specifically comprises the following steps: step 201, performing mesh division on the three-dimensional model of the elastic strip to be tested; step 202, setting the root toe of the elastic strip to be tested to be completely fixed with a gauge baffle or a cushion block, and setting the root toe of the elastic strip to be tested to be in metal contact with the gauge baffle or the root toe of the elastic strip to be tested to be in metal contact with the cushion block; step 203, applying a concentrated force to the stress position of the heel and toe in the three-dimensional model of the elastic strip to be tested, wherein the concentrated force is gradually increased until the three-dimensional model of the elastic strip is pressed down to a correct installation position; 204, performing finite element analysis on each grid in the three-dimensional model of the elastic strip at the correct mounting position, and calculating to obtain the magnitude of the concentrated force at the moment as a pre-pressure Fn under the high-frequency fatigue test; thirdly, fixing the elastic strip to be tested on a base of the test fixture: keeping the back toe of the elastic strip to be tested to abut against a back toe stop block in the test fixture, arranging the front toe of the elastic strip to be tested to be lapped on a front toe cushion block in the test fixture, and limiting the horizontal movement of the elastic strip to be tested in the test fixture through a limiting plate; and fourthly, fixing the test fixture on a mounting seat of a high-frequency fatigue testing machine, and arranging a pressure head of the high-frequency fatigue testing machine at a toe stress position in the elastic strip to be tested so as to apply the pre-pressure Fn to the elastic strip to be tested for carrying out a fatigue performance test to obtain the fatigue performance of the elastic strip to be tested, wherein the resonance frequency of the pre-pressure is more than 100Hz in the test.
Optionally, in the method for testing high-frequency fatigue of railway I-shaped elastic strips, in the first step, the three-dimensional model is established as follows: step 101, calculating a tangent angle of a root toe of a bullet strip to be tested according to the size of a front view of the bullet strip to be tested in a national iron standard; 102, establishing a three-dimensional model coordinate system according with the right-hand rule by taking a tangent line at the root toe of the elastic strip as an X-Y plane datum line and taking the vertical direction of a tangent angle at the root toe of the elastic strip as a Z axis of the three-dimensional model; 103, establishing a plane expansion curve of the middle limb part on the X-Y plane according to a plane expansion diagram about the elastic strip to be tested in a national iron standard; 104, establishing a corresponding middle limb bending curve in a Y-Z plane of the established coordinate system according to a middle limb bending curve in a main view about the elastic strip to be tested in a national iron standard; establishing a straight line in the plane expansion curve of the middle limb part, wherein the straight line is used for referring to the bending condition of the curve; taking the plane expansion curve of the middle limb part as a reference to flow along the middle limb bending curve; 105, establishing a right limb plane expansion curve in an X-Y plane of the established coordinate system according to the size parameters of the bullet strip to be tested in the national iron standard; establishing a right limb bending curve in a Y-Z plane of the established coordinate system; establishing a right limb bending reference straight line in the right limb plane expansion curve; taking the right limb plane expansion curve as a reference, and flowing along a right limb bending curve; step 106, establishing a front toe straight line at the end point of the right limb curve obtained in step 105; step 107, establishing a symmetrical graph of the right limb curve and the front toe straight line along a Y-Z plane of the coordinate system to obtain a left limb curve and a front toe straight line connected with the left limb curve; step 108, combining the curve of the middle limb part, the curve of the left limb, the curve of the right limb and the front toe straight lines respectively connected with the curve of the left limb and the curve of the right limb; and step 109, establishing a sketch cross section at the end point of the front toe straight line according to the size parameters of the bullet strip to be tested in the national iron standard, and stretching the sketch cross section along the combined curve to obtain a three-dimensional model of the bullet strip to be tested.
Optionally, in the method for testing high-frequency fatigue of railway type I elastic strip, when the step 104 and the step 105 are performed to flow along the corresponding curves, the plane expansion curve of the right limb or the plane expansion curve of the middle limb portion is set to be not allowed to stretch.
Optionally, in the method for testing high-frequency fatigue of railway I-shaped elastic strip, in step 201, meshing the three-dimensional model of the elastic strip to be tested specifically includes: dividing the three-dimensional model of the elastic strip to be tested through a three-dimensional hexahedron 8-node unit grid; in the grid, the edges of the contact surfaces between adjacent cells coincide, and the vertices of the contact surfaces between adjacent cells coincide.
Optionally, in the above method for testing high-frequency fatigue of a railway I-type spring bar, in step 203, a force-receiving position of a toe in the three-dimensional model of the spring bar to be tested is 40mm before the toe; the concentrated force is applied to a toe stress position in the three-dimensional model of the elastic strip to be tested through a gasket with the diameter of 25 mm; and in the fourth step, the diameter of a pressure head of the high-frequency fatigue testing machine is correspondingly 25 mm.
Secondly, in order to achieve the purpose, the railway I-shaped elastic strip high-frequency fatigue testing clamp is further provided for the railway I-shaped elastic strip high-frequency fatigue testing method. It includes: the surface of the base is provided with a base fixing hole, two width sides of the base are respectively provided with two side baffles, and the length side of the base is provided with a front baffle; the base fixing hole is used for fixing the elastic strip to be tested on the base of the test fixture through an M12 bolt; the front toe cushion block is arranged on one side, close to the front baffle, of the surface of the base, protrudes out of the surface of the base and is connected with the lower portion of the front baffle, and the upper surface of the front toe cushion block is in contact with the front toe of the tested elastic strip; the rear toe stop block is arranged on one side, far away from the front baffle, of the surface of the base, the rear toe stop block protrudes out of the surface of the base, and the upper surface of the rear toe stop block abuts against the rear toe of the tested elastic strip; the limiting plate is of an L-shaped structure consisting of a horizontal connecting part and a vertical limiting part, and comprises at least 2 blocks for horizontally limiting the left limb and the right limb of the elastic strip to be tested respectively; the horizontal connecting part is fixed on the upper surface of the rear toe stop block through an M6 bolt, and the vertical limiting part clamps the left limb or the right limb of the elastic strip to be tested between the left limb or the right limb and the front side end surface of the rear toe stop block.
Optionally, in the above-mentioned railway I-type elastic strip high-frequency fatigue test fixture, the total width of the base is 166mm, and the total length is 135 mm; the thickness of the side baffle or the front baffle is 10mm, the thickness of the front toe cushion block is 10mm, and the thickness of the rear toe baffle block is 15 mm.
Meanwhile, the invention also provides a railway I-type elastic strip high-frequency fatigue testing system which comprises a high-frequency fatigue testing machine and the testing clamp. The test fixture fixes the elastic strip to be tested through four M12 bolts, the tangential angle of the root and toe of the elastic strip to be tested is 55.5 degrees, and the diameter of the cross section of the elastic strip to be tested is 13 mm; the test fixture is fixed on a mounting seat of the high-frequency fatigue testing machine; the high-frequency fatigue testing machine pressure head is arranged at a toe stress position in the elastic strip to be tested so as to apply the pre-pressure Fn to the elastic strip to be tested for carrying out a fatigue performance test and finally obtain the fatigue performance of the elastic strip to be tested; in the test, the resonance frequency of the pre-pressure is more than 100 Hz; the pre-pressure Fn is obtained as follows: step t1, establishing a three-dimensional model of the elastic strip to be tested according to the size parameters of the elastic strip to be tested; step t2, carrying out hexahedron 8-node unit mesh division on the three-dimensional model of the elastic strip to be tested; step t3, arranging the root toe of the elastic strip to be tested in the three-dimensional model to be completely fixed with the gauge baffle or the cushion block, and arranging metal contact between the root toe of the elastic strip to be tested and the gauge baffle or between the root toe of the elastic strip to be tested and the cushion block; the thickness of the gauge baffle plate is the same as that of a rear toe baffle plate of the test fixture, and the thickness of the cushion block is the same as that of a front toe cushion block of the test fixture; step t4, applying a concentrated force to the stress position of the heel and toe in the three-dimensional model of the elastic strip to be tested, wherein the concentrated force is gradually increased until the three-dimensional model of the elastic strip is pressed down to a correct installation position; and t5, performing finite element analysis on each unit grid in the three-dimensional model of the elastic strip at the correct mounting position, and calculating to obtain the magnitude of the concentrated force at the moment as the pre-pressure Fn under the high-frequency fatigue test.
Optionally, in the railway I-type spring strip high-frequency fatigue testing system, the force-bearing position of the toe of the spring strip to be tested is 40mm before the toe.
Advantageous effects
The invention provides a complete set of elastic strip three-dimensional model construction method, which is used for constructing a three-dimensional model of an elastic strip to be tested and obtaining a pre-pressure Fn required by pressing the elastic strip to be tested to a correct installation position by means of finite element mechanical property analysis. Therefore, when the high-frequency fatigue test of the elastic strip is carried out, the actual performance of the elastic strip can be more truly simulated and tested, the test progress can be accelerated, and the guarantee is provided for the service performance of the railway key equipment.
The clamp special for fixing the elastic strip to be tested is designed according to the requirements of the high-frequency fatigue test. This anchor clamps can with on the stable mount pad that is fixed in high frequency fatigue testing machine of bullet strip, it is right through limiting plate wherein the left limb and the right limb of the bullet strip that awaits measuring carry out the level spacing, and the high frequency fatigue testing machine of being convenient for continuously applies high-frequency vibration to the root toe stress position of bullet strip to more real simulation test goes out bullet strip actual properties, improves the precision to the fatigue behavior test of fastener bullet strip.
Additional features and advantages of the invention will be set forth 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 accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic view of a spring to be tested of the present invention secured to a test fixture;
FIG. 2 is a schematic diagram of the structure of the bullet strip to be tested after meshing;
FIG. 3 is a schematic diagram of the stress condition of the bullet strip to be tested by finite element analysis according to the present invention;
FIG. 4 is a top view of the test fixture of the present invention;
FIG. 5 is a front view of the test fixture of the present invention;
FIG. 6 is a schematic structural diagram of a limiting plate in the test fixture of the present invention;
FIG. 7 is a schematic view of a pressure head structure in the railway type I elastic strip high-frequency fatigue testing system of the invention.
In the drawings, 1 denotes a base of a test fixture; 1-1 denotes a toe cushion block; 1-2 denotes a rear toe stop; 2 denotes a base fixing hole; 3 denotes a side dam; 4 denotes the bullet strip to be tested; 5 denotes a front baffle; 6 denotes a limit plate; and 7, a mounting hole of the stopper plate.
Detailed Description
In order to make the purpose and technical solution of the embodiments of the present invention clearer, the technical solution of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The meaning of "front and back" in the present invention means that when the user faces the elastic strip, the side close to the user is front and the side far from the user is back, and is not specifically limited to the present invention.
The meaning of "inside and outside" in the present invention means that the direction toward the center of the spring bar mounted thereon is inside and vice versa with respect to the spring bar mounting base itself, and is not a specific limitation of the mechanism of the device of the present invention.
The meaning of "left and right" in the present invention means that when the user faces the elastic strip, the left side of the user is left, and the right side of the user is right, and is not a specific limitation of the present invention.
The term "connected" as used herein may mean either a direct connection between the components or an indirect connection between the components via other components.
The term "up and down" as used herein means that when the user faces the elastic strip, the upper side of the user is the upper side, and the lower side of the user is the lower side, and is not specifically limited to the present invention.
Fig. 1 shows a fixture for high-frequency fatigue testing of railway type I spring strips according to the invention. As shown in fig. 4 and 5, the present invention includes:
the surface of the base 1 is provided with a base fixing hole 2, two width sides of the base are respectively provided with two side baffles 3, and the length side of the base is provided with a front baffle 5; the base fixing hole 2 is used for fixing the elastic strip 4 to be tested on the base 1 of the test fixture through an M12 bolt;
the front toe cushion block 1-1 is arranged on one side, close to the front baffle 5, of the surface of the base 1, the front toe cushion block 1-1 protrudes out of the surface of the base 1 and is connected with the lower portion of the front baffle 5, and the upper surface of the front toe cushion block 1-1 is in contact with the front toe of the tested elastic strip;
the rear toe stop block 1-2 is arranged on one side of the surface of the base 1 far away from the front baffle 5, the rear toe stop block 1-2 protrudes out of the surface of the base 1, and the upper surface of the rear toe stop block 1-2 is abutted with the rear toe of the tested elastic strip;
referring to fig. 6, the fixture further includes a limiting plate 6, which is an L-shaped structure formed by a horizontal connecting portion and a vertical limiting portion, where the limiting plate 6 includes at least 2 blocks for horizontally limiting the left limb and the right limb of the elastic strip 4 to be tested; the horizontal connecting part is fixed on the upper surface of the rear toe block 1-2 through an M6 bolt, and the vertical limiting part clamps the left limb or the right limb of the spring strip 4 to be tested between the vertical limiting part and the front side end surface of the rear toe block 1-2.
In order to match the spring strip structure specified by the national iron standard TB/T1495-:
the total width of the base is 166mm, and the total length is 135 mm; the transverse spacing of the base fixing holes 2 is 50mm, and the longitudinal spacing is 44 mm; the thicknesses of the side baffle 3 and the front baffle 5 are both 10 mm; the thickness of the front toe cushion block 1-1 is 10mm, and the thickness of the rear toe stop block 1-2 is 15 mm.
The elastic strip 4 is limited to move in a horizontal plane by two limiting plates 6, the transverse center distance of the mounting holes 7 of the limiting plates 6 is 84mm, the longitudinal center distance of the mounting holes 7 of the limiting plates 6 is 15mm, and M6 bolts are used.
The test fixture is arranged on a high-frequency fatigue testing machine to form a system for testing the high-frequency fatigue performance of the railway I-type elastic strip. In the system, the test fixture fixes the elastic strip 4 to be tested through four M12 bolts, the tangent angle of the root toe of the elastic strip 4 to be tested is 55.5 degrees, and the diameter of the cross section of the elastic strip 4 to be tested is 13 mm; the test fixture is fixed on a mounting seat of the high-frequency fatigue testing machine.
In the system, the high-frequency fatigue testing machine pressure head is arranged at a toe stress position in the elastic strip 4 to be tested so as to apply the pre-pressure Fn to the elastic strip 4 to be tested for performing a fatigue performance test and finally obtain the fatigue performance of the elastic strip 4 to be tested.
Specifically, based on the above system, the fatigue performance of the bullet strip 4 to be tested can be obtained by:
step one, establishing a three-dimensional model of the elastic strip to be tested according to the size parameters of the elastic strip to be tested in the state iron standard; in the three-dimensional model, the tangent angle at the root toe of the bullet strip to be tested conforms to the size of a front view of the bullet strip to be tested in the national iron standard; the coordinate axis of the three-dimensional model takes a tangent line at the root toe of the elastic strip as an X-Y plane datum line; the vertical direction of the tangent angle of the root toe of the elastic strip is the Z axis of the three-dimensional model; the coordinate system of the three-dimensional model conforms to the right-hand rule;
secondly, performing finite element analysis by using the three-dimensional model of the elastic strip to be tested to obtain the magnitude Fn of the pre-pressure under the high-frequency fatigue test corresponding to the elastic strip to be tested; the finite element analysis specifically comprises the following steps:
step 201, performing mesh division on the three-dimensional model of the elastic strip to be tested, which is shown in fig. 2;
step 202, setting the root toe of the elastic strip to be tested to be completely fixed with a gauge baffle or a cushion block, and setting the root toe of the elastic strip to be tested to be in metal contact with the gauge baffle or the root toe of the elastic strip to be tested to be in metal contact with the cushion block;
step 203, applying a concentrated force to the stress position of the heel and toe in the three-dimensional model of the elastic strip to be tested, wherein the concentrated force is gradually increased until the three-dimensional model of the elastic strip is pressed down to a correct installation position;
step 204, performing finite element analysis on each grid in the three-dimensional model of the elastic strip at the correct installation position to obtain the condition of the stressed elastic strip shown in fig. 3, and calculating to obtain the magnitude of the concentrated force at the moment as a pre-pressure Fn under the high-frequency fatigue test;
thirdly, fixing the elastic strip 4 to be tested on the base 1 of the test fixture: keeping the back toe of the elastic strip to be tested against a back toe stop block 1-2 in the test fixture, arranging the front toe of the elastic strip to be tested to be lapped on a front toe cushion block 1-1 in the test fixture, and limiting the horizontal movement of the elastic strip to be tested 4 in the test fixture through a limiting plate 6;
and fourthly, fixing the test fixture on a mounting seat of a high-frequency fatigue testing machine, and arranging a pressure head of the high-frequency fatigue testing machine at a toe stress position in the elastic strip 4 to be tested so as to apply the pre-pressure Fn to the elastic strip 4 to be tested for carrying out a fatigue performance test to obtain the fatigue performance of the elastic strip 4 to be tested, wherein the resonance frequency of the pre-pressure is more than 100Hz in the test. The structure of the pressure head of the high-frequency fatigue testing machine is shown in fig. 7, and the pressure head is a cylinder with a diameter corresponding to 25mm and sleeved on a testing part of the high-frequency fatigue testing machine.
The three-dimensional model of the bullet strip to be tested shown in fig. 2 can be created by the following steps:
(1) firstly, drawing the elastic strip into a three-dimensional model with the same horizontal line according to a drawing of the elastic strip to be tested;
(2) the unfolded drawing is folded into a physical drawing appearance according to a front view and a side view, and is shown as an elastic strip 4;
(3) the elastic strips are subjected to continuous solid three-dimensional hexahedron 8-node unit grid division, as shown in fig. 1, the number of grids and the number of nodes can be reduced, the calculation speed is increased, and the calculation cost is reduced while the high precision is ensured by using the type of grids;
(4) after the elastic strip and the cushion block are integrally assembled, the rear toe is fixed, as shown in figure 3;
(5) the bolt down force is gradually changed until the spring strips reach the correct mounting state, as shown in fig. 3. At this point, the bolt down force Fn in kN is obtained. After the numerical value is obtained, the reasonable installation state can be achieved when the high-frequency fatigue testing machine loads pre-pressure, and the testing steps are simplified.
Specifically, for the elastic strip to be tested according to the national iron standard TB/T1495-1992 drawings, the three-dimensional model can be established through the following steps:
step 1: and calculating the tangent angle of the heel toe of the elastic strip according to the size in the front view of the railway I-type elastic strip.
Step 2: in the rhinoceros software, the angle is taken as an X-Y plane reference line, the vertical direction is taken as a Z axis, and a three-dimensional coordinate system which accords with the right-hand rule is adjusted.
And step 3: on this plane, a plane development curve of the limb portion in a plane development view is drawn in accordance with the railway type I bullet.
And 4, step 4: drawing a curve in the Y-Z plane of the coordinate system according to the bending curve of the middle limb in the front view.
And 5: and drawing a bending reference straight line in the middle limb plane expansion curve.
Step 6: using the along-the-curve flow command, the mid-limb plane expansion curve is referenced to a reference straight line and flows along the mid-limb flexion curve.
And 7: and drawing a right limb plane expansion curve in an X-Y plane.
And 8: the right limb flexion curve is plotted in the Y-Z plane.
And step 9: and drawing a bending reference straight line in the unfolding curve of the right limb plane.
Step 10: the right limb plane expansion curve is referenced to a reference straight line and flows along the right limb flexion curve using an along-the-curve flow command.
Step 11: and drawing a front toe straight line at the end point of the bent right limb curve.
Step 12: the right limb curve and the anterior toe straight line are symmetrical along the Y-Z plane.
Step 13: combine 5 curves.
Step 14: a sketched cross-section of 13mm in diameter was drawn at the front toe end point.
Step 15: and stretching the sketched section along the combined curve, and storing the sketched section as an x _ t format file.
Wherein: the angle described in step 1 is 55.5 °.
Wherein: and 3, the Y-axis coordinate range of the mid-limb plane expansion curve is within the range of (-42, 42).
Wherein: in step 5, the coordinates of the reference straight line end points are (0,0), (80.9 and 0), respectively.
Wherein: the flow along the curve in step 6 requires selection of the disallow stretch option.
Wherein: the unfolding curve of the right limb plane in the step 7 is a three-section curve, namely a curve R22.5+42.6+ R19.5.
Wherein: in step 9, the reference straight line end coordinates are (0,42), (80.9,42), respectively.
Wherein: the flow along the curve in step 10 requires the selection of the disallowed stretch option.
In the second step, finite element analysis is performed by using the three-dimensional model of the elastic strip to be tested, so as to obtain the magnitude Fn of the pre-pressure under the high-frequency fatigue test corresponding to the elastic strip to be tested, which can be realized by ABAQUS software specifically:
step 1: importing the x _ t file drawn by the rhinoceros software into the ABAQUS software.
Step 2: and carrying out hexahedral mesh division on the elastic strips. The grid of the type can ensure high precision, reduce the number of grids and nodes, accelerate the calculation speed and reduce the calculation cost.
And step 3: completely fixing the elastic strip heel toe, completely fixing the gauge baffle or the cushion block, and setting metal contact.
And 4, step 4: a pad with a diameter of 25mm is used, and a concentrated force is applied to press down the position 40mm before the heel of the elastic strip.
And 5: the down force is gradually increased, and the down force of 22.5kN is found in the post-processing to just reach the correct installation position. After the numerical value is obtained, the reasonable installation state can be achieved when the high-frequency fatigue testing machine loads pre-pressure, and the testing steps are simplified.
Step 6: the force is the magnitude Fn of the pre-pressure of the high-frequency fatigue testing machine.
In the fourth step, the fatigue performance test can be carried out by mounting and fixing the elastic strip to be tested in the following mode:
step 1: fixing the base on a high-frequency fatigue testing machine mounting seat by using four M12 bolts, and placing the front baffle facing an experimenter;
step 2: placing the fastener elastic strip in the middle of the base, enabling the rear toe to abut against the rear toe stop block, enabling the front toe to be lapped on the front toe cushion block, and aligning the middle limb to a cylindrical pressure head with the diameter of 25 mm;
and step 3: using four M6 bolts to install two limit plates at correct positions and fixing the horizontal position of the elastic strip;
and 4, step 4: and (3) mounting a cylindrical pressure head on the testing machine actuator, pressing the pressure head down to press the middle limb of the elastic strip, wherein the pre-pressure is the magnitude of Fn obtained by finite element calculation, so as to ensure that the state of the elastic strip during testing is the correct mounting state of the elastic strip during the installation, and loading the pre-pressure of the Fn to finish the correct assembly of the testing.
Wherein: the longitudinal center distance and the transverse center distance of the M12 bolt holes are 44mm and 50mm respectively;
wherein: the longitudinal center distance and the transverse center distance of the M6 bolt holes are respectively 15mm and 84 mm;
wherein: the total length of the base is 135mm, the total width is 166mm, and the total height is 60 mm.
Wherein: the thickness of the base, the left side baffle, the right side baffle and the front baffle is 10 mm;
wherein: the rear toe block is 15mm thick, and the front toe cushion block is 10mm thick.
In the test, the dither test machine used a 25mm diameter indenter with a loading position 40mm in front of the heel and toe. And (5) gradually increasing the magnitude of the down pressure according to the step (5), finding out that the down pressure of 22.5kN can just reach the correct installation position in the post-processing, loading the pre-pressure of 22.5kN, and performing a fatigue test at a frequency of more than 100Hz in a resonance mode.
Therefore, the invention provides a fatigue test method of railway I-shaped elastic strips under high-frequency vibration and a clamp design thereof, rhinoceros software is used for accurately modeling a three-dimensional entity of the I-shaped elastic strips, finite element software ABAQUS is used for carrying out correct installation mechanical property analysis on the I-shaped elastic strips, parameters which can be applied to a high-frequency fatigue testing machine are obtained, and the designed clamp and a high-frequency fatigue testing machine are used for testing the response of the I-shaped elastic strips under the high-frequency vibration, so that the high-frequency fatigue damage characteristic closer to the actual condition is obtained.
The invention has the following advantages:
1. the elastic strip three-dimensional model is high in establishing precision and good in accuracy.
2. The elastic strips drawn by the method are easy to divide into hexahedral meshes, and the number of the meshes and the quality of the meshes can be well controlled.
3. When the finite element calculation is carried out by using the drawn elastic strip model, the calculation precision is high, the calculation cost is low, and the actual working condition can be well simulated.
4. The elastic strip is convenient to install and firm in fixation.
5. The elastic strip has accurate testing pre-pressure and can accurately reach the actual correct installation state.
6. Can be adjusted by simple parameters to be suitable for different sizes of elastic strips and different fatigue testing machines.
The above are merely embodiments of the present invention, which are described in detail and with particularity, and therefore should not be construed as limiting the scope of the invention. It should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the spirit of the present invention, and these changes and modifications are within the scope of the present invention.
Claims (4)
1. A high-frequency fatigue testing method for railway I-shaped elastic strips is characterized by comprising the following steps:
firstly, establishing a three-dimensional model of a spring strip to be tested; the coordinate axis of the three-dimensional model takes a tangent line at the root toe of the elastic strip as an X-Y plane datum line; the vertical direction of the tangent angle of the root toe of the elastic strip is the Z axis of the three-dimensional model;
secondly, performing finite element analysis by using the three-dimensional model of the elastic strip to be tested to obtain the magnitude Fn of the pre-pressure under the high-frequency fatigue test corresponding to the elastic strip to be tested; the finite element analysis specifically comprises the following steps:
step 201, performing mesh division on the three-dimensional model of the elastic strip to be tested;
step 202, setting the root toe of the elastic strip to be tested to be completely fixed with a gauge baffle or a cushion block, and setting the root toe of the elastic strip to be tested to be in metal contact with the gauge baffle or the root toe of the elastic strip to be tested to be in metal contact with the cushion block;
step 203, applying a concentrated force to the stress position of the heel and toe in the three-dimensional model of the elastic strip to be tested, wherein the concentrated force is gradually increased until the three-dimensional model of the elastic strip is pressed down to a correct installation position;
204, performing finite element analysis on each grid in the three-dimensional model of the elastic strip at the correct mounting position, and calculating to obtain the magnitude of the concentrated force at the moment as a pre-pressure Fn under the high-frequency fatigue test;
thirdly, fixing the elastic strip (4) to be tested on a base (1) of the test fixture: keeping the back toe of the elastic strip to be tested against a back toe stop block (1-2) in the test fixture, arranging the front toe of the elastic strip to be tested to be lapped on a front toe cushion block (1-1) in the test fixture, and limiting the horizontal movement of the elastic strip to be tested (4) in the test fixture through a limiting plate (6);
fourthly, fixing the test fixture on a mounting seat of a high-frequency fatigue testing machine, and arranging a pressure head of the high-frequency fatigue testing machine at a root-toe stress position in the elastic strip (4) to be tested to apply the pre-pressure Fn to the elastic strip (4) to be tested to carry out fatigue performance test so as to obtain the fatigue performance of the elastic strip (4) to be tested, wherein the resonance frequency of the pre-pressure is more than 100Hz in the test;
the three-dimensional model is built in the following way:
step 101, calculating a tangent line angle of the root and toe of the elastic strip to be tested;
102, establishing a three-dimensional model coordinate system according with the right-hand rule by taking a tangent line at the root toe of the elastic strip as an X-Y plane datum line and taking the vertical direction of a tangent angle at the root toe of the elastic strip as a Z axis of the three-dimensional model;
103, establishing a planar expansion curve of the middle limb part on the X-Y plane;
104, establishing a corresponding middle limb bending curve in a Y-Z plane of the established coordinate system; establishing a straight line in the plane expansion curve of the middle limb part, wherein the straight line is used for referring to the bending condition of the curve; taking the plane expansion curve of the middle limb part as a reference to flow along the middle limb bending curve;
105, establishing a right limb plane expansion curve in the X-Y plane of the established coordinate system; establishing a right limb bending curve in a Y-Z plane of the established coordinate system; establishing a right limb bending reference straight line in the right limb plane expansion curve; taking the right limb plane expansion curve as a reference, and flowing along a right limb bending curve;
step 106, establishing a front toe straight line at the end point of the right limb curve obtained in step 105;
step 107, establishing a symmetrical graph of the right limb curve and the front toe straight line along a Y-Z plane of the coordinate system to obtain a left limb curve and a front toe straight line connected with the left limb curve;
step 108, combining the curve of the middle limb part, the curve of the left limb, the curve of the right limb and the front toe straight lines respectively connected with the curve of the left limb and the curve of the right limb;
and step 109, establishing a sketch cross section at the end point of the front toe straight line, and stretching the sketch cross section along the combined curve to obtain a three-dimensional model of the elastic strip to be tested.
2. The railway type I elastic strip high frequency fatigue testing method as claimed in claim 1, wherein in said step 104 and said step 105, when the step of flowing along the corresponding curve is performed, the right limb plane expansion curve or the middle limb plane expansion curve is set to not allow stretching.
3. The railway type I spring strip high-frequency fatigue testing method of claim 1, wherein in the step 201, the gridding of the three-dimensional model of the spring strip to be tested is specifically: dividing the three-dimensional model of the elastic strip to be tested through a three-dimensional hexahedron 8-node unit grid;
in the grid, the edges of the contact surfaces between adjacent cells coincide, and the vertices of the contact surfaces between adjacent cells coincide.
4. The railway type I spring strip high-frequency fatigue testing method as claimed in claim 1, wherein in the step 203, the force-bearing position of the toe in the three-dimensional model of the spring strip to be tested is 40mm before the toe;
the concentrated force is applied to a toe stress position in the three-dimensional model of the elastic strip to be tested through a gasket with the diameter of 25 mm;
and in the fourth step, the diameter of a pressure head of the high-frequency fatigue testing machine is correspondingly 25 mm.
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| CN110765684B (en) * | 2019-10-16 | 2023-10-13 | 中国铁路设计集团有限公司 | W-shaped spring strip parameterization modeling method |
| KR102173934B1 (en) * | 2019-11-27 | 2020-11-04 | 대원강업주식회사 | Fatigue Inspection Device of Rail Fastener Spring for High-Speed Railroad |
| CN110987678B (en) * | 2019-12-17 | 2022-01-04 | 西南交通大学 | Fastener system fatigue test method |
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