CN114216667B - Suspension method for modal test and modal test method - Google Patents
Suspension method for modal test and modal test method Download PDFInfo
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- CN114216667B CN114216667B CN202111533547.4A CN202111533547A CN114216667B CN 114216667 B CN114216667 B CN 114216667B CN 202111533547 A CN202111533547 A CN 202111533547A CN 114216667 B CN114216667 B CN 114216667B
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- 238000012360 testing method Methods 0.000 title claims abstract description 197
- 239000000725 suspension Substances 0.000 title claims abstract description 91
- 238000000034 method Methods 0.000 title claims abstract description 35
- 238000010998 test method Methods 0.000 title abstract description 10
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 182
- 239000010959 steel Substances 0.000 claims abstract description 182
- 238000005259 measurement Methods 0.000 claims abstract description 10
- 238000003825 pressing Methods 0.000 claims description 12
- 238000004088 simulation Methods 0.000 abstract description 7
- 230000000694 effects Effects 0.000 description 6
- 238000013461 design Methods 0.000 description 5
- 238000009434 installation Methods 0.000 description 5
- 238000012546 transfer Methods 0.000 description 5
- 238000004364 calculation method Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000013016 damping Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000005284 excitation Effects 0.000 description 2
- 230000001012 protector Effects 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- 239000004484 Briquette Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M13/00—Testing of machine parts
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M99/00—Subject matter not provided for in other groups of this subclass
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Abstract
The invention relates to a modal test suspension method and a modal test method, belongs to the technical field of modal test parameter measurement, and solves the problems that an air spring is complex to operate and has a small application range in modal test boundary condition simulation in the prior art. A modal test suspension method comprising the steps of: designing technical parameters of a steel spring contained in the suspension assembly, wherein the technical parameters comprise the wire diameter, the outer diameter, the rotation direction and the stretching length of the steel spring and the bearing capacity of the steel spring; and hanging the test piece by using a hanging assembly according to the determined technical parameters so as to enable the test piece to be in a free-free boundary condition. According to the invention, the technical parameters of the steel spring are determined according to the weight and the fundamental frequency of the test piece, so that the rigid body frequency of the test system can reach the lowest frequency of the test piece, and the test quality of the mode is improved.
Description
Technical Field
The invention relates to the technical field of modal test parameter measurement, in particular to a modal test suspension method and a modal test method.
Background
At present, the development of aerospace technology is rapid, and higher requirements are put on the model test technology. The larger the volume, the larger the mass, the lower the frequency and the ultralow frequency modal measurement requirements are more prominent. In order to accurately provide modal parameters for development and design of aerospace products, the test piece must be excited through a modal test to measure parameters such as dynamic characteristics, natural frequency, modal shape, damping and the like of the structure. In the mode test at home and abroad, the test piece is in a completely free state and is not influenced by the constraint of an additional boundary, so that the free-free state of the test piece is obtained, and the free-free boundary condition required by the structure is simulated by hanging.
In an ideal modal test, the test piece structure is in a completely free state, free from any additional boundary constraints, called the free-free boundary condition of the structure. Thus, in order to acquire a free mode of the structure, suspension or support is typically employed to simulate the free-free boundary conditions required for the structure. For a vertical mode test consisting of a "test piece-suspension device", the suspension device has the function of enabling the test piece of the mode test to be in a free state, and the rigid motion frequency of the suspension device in the vertical direction is lower than 3 times of the fundamental frequency of the test piece. The manner in which the boundaries of different suspension units are simulated varies considerably.
The existing mode test boundary condition simulation comprises an air spring supporting mode, the air spring is huge in size, different tooling molds are designed and produced for test pieces with different molded surfaces, and the air spring needs to be adjusted repeatedly during use, so that the air spring is mostly suitable for the test pieces which are heavy and are not easy to suspend.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a suspension method and a modal test method for a modal test, which are used for solving the problems of complex operation and small application range of an air spring in the existing modal test boundary condition simulation.
The aim of the invention is mainly realized by the following technical scheme:
in one aspect, the invention provides a suspension method for a modal test, comprising the steps of:
Designing technical parameters of a steel spring contained in the suspension assembly, wherein the technical parameters comprise the wire diameter, the outer diameter, the rotation direction and the stretching length of the steel spring and the bearing capacity of the steel spring;
And hanging the test piece by using a hanging assembly according to the determined technical parameters so as to enable the test piece to be in a free-free boundary condition.
Optionally, the technical parameter design method of the steel spring comprises the following steps: and determining the technical parameters of the spring according to the axial deformation born by the steel spring.
Optionally, the axial deformation amount born by the steel spring is determined according to the weight of the test piece and the fundamental frequency.
Optionally, the rigid body motion frequency of the steel spring in the vertical direction is 1/5 times of the fundamental frequency of the test piece.
Alternatively, the test piece is suspended by a suspension assembly in a three-point suspension mode.
Optionally, the tensile lengths of the steel springs are all 250mm.
Optionally, the method for suspending the test piece by using the suspension assembly comprises the following steps:
The suspension arm is connected with a suspension rope, and then the test piece is suspended on the suspension rope through a connecting component. Preferably, the lifting rope is a steel wire rope.
Optionally, the type of the steel spring comprises one or a combination of a plurality of 1.5T steel springs, 3T steel springs, 5T steel springs and 7T steel springs.
Optionally, the fundamental frequency of the test piece is 3-5Hz.
On the other hand, the invention also provides a modal test method, comprising the suspension method of the modal test.
Optionally, the calculation formula of the axial deformation is:
In the above formula:
Lambda is the axial deflection in units of: mm;
n is the effective number of turns of the spring, unit: a ring;
G is the shear modulus of the spring material, unit: pa;
d is the diameter of the material, unit: mm;
D 2 is the outer diameter of the spring, unit: mm;
d is the spring pitch diameter, unit: mm;
C is the rotation ratio, unit: c=d/D;
f is the axial pressure in units of: n.
The number of turns n of the spring is:
The spring has the following rigidity:
The modal test method of the invention is completed by a modal test suspension device, and the modal test suspension device comprises: a suspension assembly; the suspension assembly comprises a plurality of steel springs, and technical parameters of the steel springs are determined according to the weight and the fundamental frequency of the test piece; the steel springs comprise a plurality of steel springs which are arranged in parallel, and at least one group of steel springs which are connected in parallel; the test piece is characterized by further comprising a crane beam, wherein a plurality of hanging chains are connected to the crane beam, and each steel spring and each group of steel springs are respectively hung on the hanging chains through a lifting hook.
Optionally, each group of steel springs is provided with a resultant force tool, a plurality of steel springs are connected to the resultant force tool in parallel, and the hanging chain lifting hook is connected with the resultant force tool.
Optionally, the resultant force tool comprises a main body, a rotary hanging ring, a fixing plate, a pressing block and a first pin shaft.
Optionally, the resultant force tool comprises an upper resultant force tool and a lower resultant force tool, a plurality of steel springs are connected in parallel between the upper resultant force tool and the lower resultant force tool, and the upper resultant force tool is connected with the hanging hook of the hanging chain.
Optionally, the tool further comprises a switching sleeve, and the lower resultant force tool is connected with the switching sleeve.
Optionally, the adapting sleeve comprises an adapting shackle, and the adapting shackle is connected with the lower resultant force tool.
Optionally, the transfer shackle comprises a U-shaped rod and a second pin shaft, wherein the U-shaped rod is connected with the rotary hanging ring, and the pin shaft is connected with the test piece.
Optionally, a protector is further included, the protector being disposed between the hoist link hook and the adapter sleeve.
Optionally, the protection member is a steel wire rope.
Optionally, the protection member is disposed between the upper resultant force tooling and the lower resultant force tooling.
Compared with the prior art, the invention has at least one of the following beneficial effects:
(1) According to the invention, the steel springs are arranged to comprise a plurality of steel springs which are arranged in parallel, or a plurality of steel springs which are arranged in parallel and at least one group of steel springs which are connected in parallel, so that the flexibility of steel spring connection can be improved, and the combination of single or a plurality of steel springs with the same weight and frequency can be realized, thereby realizing the high-precision parameter measurement of the modal test of the aerospace product with longer length (more than 20 meters), larger volume and heavier weight (more than 30 tons).
(2) According to the invention, the crane beam and the plurality of hanging chains connected to the crane beam are arranged, so that the test piece can be conveniently hung through the steel spring and the connecting assembly, and the stable hanging state of the test piece is ensured.
(3) Through the hanging chain lifting hook connected to the hanging chain or the switching external member arranged between each group of steel springs and the test piece, the convenience and the reliability of the connection of the test piece are improved. The resultant force tool included in each group of steel springs can enable a plurality of steel springs in a single group to be connected in parallel, so that the combination of the plurality of steel springs is convenient to achieve, the plurality of steel springs with the same weight and frequency can be connected in parallel, the purpose of increasing bearing capacity is achieved, and the modal test measurement of a heavy and fundamental frequency low-test piece is guaranteed.
(4) Through set up protection piece (wire rope) between hanging chain lifting hook and switching external member, perhaps last resultant force frock and lower resultant force frock between, can effectively avoid the incident that the test piece caused because of unexpected dropping, improved the security of test process.
(5) According to the invention, the suspension assembly is arranged to comprise a plurality of steel springs, so that the connection and assembly of test pieces can be facilitated, the number and technical parameters of the steel springs are determined according to the weight and fundamental frequency of the test pieces, and the rigid body frequency of the test system can be lower than 1/3 of the fundamental frequency of the test pieces. In particular, it may be 1/5 of the fundamental frequency of the test piece, such a low rigid body frequency improves the quality and accuracy of the measurement of modal test parameters (e.g., natural frequency, mode shape, damping ratio, force-frequency curve, etc.). In a specific modal test, technical parameters such as steel wire diameter, outer diameter, rotation direction, stretching length, bearing capacity and the like of a steel spring can be designed according to the weight and fundamental frequency requirements of an actual test piece, and the simulation of the natural frequency boundary condition of a system is ensured by selecting a form of freely matching a single steel spring or a plurality of steel springs in parallel.
The steel spring suspension device can meet the modal test of the free-free boundary condition of the test piece in the vertical direction, and for heavier (more than 30 tons) test pieces, the rigidity is far greater than the additional rigidity of the steel spring, so that the influence of the additional rigidity of the steel spring on measurement data can be ignored, and a good test effect is obtained.
In the invention, the technical schemes can be mutually combined to realize more preferable combination schemes. 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 drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
FIG. 1 is a schematic view of a modal test suspension of the present invention;
FIG. 2 is a schematic structural diagram of the upper resultant force tool of the present invention;
fig. 3 is a schematic structural view of the transfer shackle in the present invention;
FIG. 4 is a schematic view of the structure of the briquette of the present invention;
Fig. 5 is a schematic structural view of a first pin according to the present invention;
FIG. 6 is a schematic structural view of a fixing plate according to the present invention;
FIG. 7 is a schematic structural view of the lifting ring of the present invention;
FIG. 8 is a schematic structural view of a main body of the resultant force tool of the present invention;
fig. 9 is a schematic structural view of an embodiment of the present invention provided with a spare pendant.
Reference numerals:
1-a steel spring;
2-a crane beam;
3-a pendant;
4-a hanging chain lifting hook;
5-resultant force tooling; 51-assembling a resultant force tool; 52-lower resultant force tooling; 53-hanging rings; 54-a fixed plate; 55-briquetting;
6-an adapter sleeve; 61-rotating the hanging ring; 62-transfer shackle; 63-U-shaped bar; 64-a second pin;
7-a steel wire rope;
8-test piece;
9-a main body;
10-a standby hanging chain;
11-protrusions;
12-connecting a hanging ring;
13-belting.
Detailed Description
The following detailed description of preferred embodiments of the invention is made in connection with the accompanying drawings, which form a part hereof, and together with the description of the embodiments of the invention, are used to explain the principles of the invention and are not intended to limit the scope of the invention.
Example 1
Referring to fig. 1, a modal trial suspension is disclosed in one embodiment of the present invention. The modal test suspension device of the embodiment is used for measuring high-precision parameters of modal tests of 3-5Hz aerospace products with longer length (more than 20 meters), larger volume and heavier weight (more than 30 tons).
The modal test suspension device of this embodiment includes: a suspension assembly and a test piece 8 attached to the suspension assembly; the suspension assembly comprises a plurality of steel springs 1, and the technical parameters of the steel springs 1 are determined according to the weight and the fundamental frequency of the test piece 8.
In practice, the mode test suspension device of the invention has the function of enabling the test piece 8 of the mode test to be in a suspension state and simulating free-free boundary conditions, and measuring structural mode parameters of the test piece 8 in the free-free state.
Compared with the prior art, the suspension assembly provided by the embodiment can suspend the test piece 8, and the test piece 8 is suspended by the plurality of steel springs 1, so that the installation operation of the test piece 8 on the simulation assembly is simplified.
The modal test suspension device has the advantages of simple structure, easy installation and strong practicability, can be applied to modal tests of test pieces 8 in different forms, and has practical engineering significance.
The technical parameters of the steel springs 1 are specifically set according to the weight and the fundamental frequency of the test piece 8, including the parallel connection quantity of the steel springs 1 and the adjustment of the technical indexes such as the wire diameter, the outer diameter, the rotation direction, the stretching length, the bearing capacity and the like of the steel wires of each steel spring 1.
The suspension device for the modal test can fully meet the modal test boundary conditions of the test piece 8 with larger and heavier volume and low fundamental frequency. The test piece 8 can be suspended by the steel spring 1 in the test, so that the test preparation work is effectively reduced, and the test period is shortened.
Through the form of adjustable technical parameters, the mode test suspension device can be in coordinated association with the mass of the test piece 8 in the mode test state and the lower limit frequency of the test, and the success rate of the test is reliably ensured. Compared with the existing air spring supporting mode, the method effectively simplifies the installation operation of the test piece 8 on the test tool through the mode of suspending the test piece 8, is suitable for the test pieces 8 with different volumes, weights and fundamental frequencies, effectively expands the application range, and simultaneously ensures the reliability, stability and accuracy of the test.
Based on different properties and parameters of the test piece 8, the steel springs 1 can be arranged in parallel, or can be combined in a plurality of groups, and the overall frequency of the modal test suspension device and the natural frequency of the test piece 8 can be coordinated and unified through the combination of the steel springs 1 in different forms, so that the simulation effect of the test piece 8 is ensured.
In one specific embodiment, the steel springs 1 comprise two steel springs 1 which are arranged in parallel, and a group of two steel springs 1 which are connected in parallel, wherein two independent steel springs 1 are arranged on two sides of the group of steel springs 1, so that the overall suspension force of the modal test suspension device is dispersed more uniformly.
The steel spring 1 and the test piece 8 are in the mode test, in particular in the form of a suspension, and the mode test suspension device in the invention further comprises a crane beam 2 arranged at the top, wherein the test piece 8 is suspended on the crane beam 2 through the steel spring 1.
Preferably, a plurality of hoist chains 3 are connected to the hoist beam 2, and the length of the hoist chains is changed by operating the hoist. Each steel spring 1 and each group of steel springs 1 respectively suspend the test piece 8 on the hanging chain 3 through the hanging chain hanging hook 4. On each individual steel spring 1, the steel spring 1 is connected between the hoist chain 3 and the test piece 8; on each group of steel springs 1, a plurality of steel springs 1 are connected in parallel on the resultant force tool, and a hanging chain lifting hook 4 is connected with the resultant force tool.
The plurality of steel springs 1 in each group of steel springs 1 are connected and assembled through a resultant force tool 5, and the plurality of steel springs 1 are connected in parallel on the resultant force tool. By adopting a combination form of the connecting component, the resultant force tool 5 and the steel spring 1, the steel spring 1 and the test piece 8 can be rapidly installed on the hanging chain lifting hook 4.
Specifically, the resultant force tooling 5 includes an upper resultant force tooling 51 and a lower resultant force tooling 52, the plurality of steel springs 1 are connected in parallel between the upper resultant force tooling 51 and the lower resultant force tooling 52, the upper resultant force tooling 51 is connected with the hanging chain hook 4, and the lower resultant force tooling 52 is connected with the adapting sleeve 6.
Based on the different setting forms of each individual steel spring 1 and each group of steel springs 1, the embodiment further comprises a switching sleeve, and the lower resultant force tool is connected with the switching sleeve. Each steel spring 1 and each group of steel springs 1 are connected with a hanging chain lifting hook 4, and the lower ends of the individual steel springs 1 and the lower ends of the groups of steel springs 1 are connected with a test piece 8 through a switching sleeve 6.
Based on the form of connecting two steel springs 1 on one resultant force tool 5 in the present embodiment, the upper resultant force tool 51 and the lower resultant force tool 52 are arranged in the vertical direction and have the same structural form, as shown in fig. 2, and each of the two resultant force tools includes a main body 9, a rotary lifting ring 61, two lifting rings 53, two fixing plates 54, two pressing blocks 55 and two first pins.
The rotary hanging ring 61 comprises a rotary main body and a ring part, the rotary main body is in threaded connection with the main body 9, each pressing block is fixed on the main body 9 through two M20 screws, and the two pressing blocks 55 are respectively located at two ends of the main body 9. As shown in fig. 6, the fixing plate 54 is L-shaped, and the fixing plate 54 and the pressing block 55 are fixed by 2M 10 screws, so that a gap is formed between the fixing plate 54 and the main body 9, and a wire rope for protection passes through the gap.
The hanging ring 53 is in a stepped column shape, as shown in fig. 7, and includes a first column body and a second column body, wherein the first column body is a cylinder, and the lower surface of the first column body is connected with the upper surface of the second column body. The first column is screwed with the main body 9 to achieve a fixed connection of the lifting ring 53 with the main body 9.
The second post is equipped with the recess of opening orientation direction of keeping away from first post direction, and this recess does not extend to the upper surface of second post along the axial direction of second post, but radially link up along the lateral wall of second post, and this recess cuts apart the second post into two opposite jambs, all is equipped with radial through-hole on every jamb, and two radial through-holes are passed to first round pin axle. In order to prevent the first pin shaft from falling off, a pin hole is further formed in the first pin shaft, and a pin penetrates through the pin hole. The first pin and the suspension ring 53 form a gap through which the hook of the steel spring 1 passes.
The two steel springs 1 are respectively connected and fixed in a mode of penetrating through the hanging ring 53 through a pin shaft, the upper resultant force tool 51 is respectively connected with the hanging chain hook 4 and one end of the steel spring 1, and the lower resultant force tool 52 is respectively connected with the switching sleeve 6 and the other end of the steel spring 1. The structures of the hanging ring 53, the pressing block 55, the first pin shaft, the fixing plate 54 and the main body 9 are shown in fig. 7, 4,5, 6 and 8 respectively. The body 9 has a length of 750mm and a width of 200mm.
The adaptor sleeve 6 specifically comprises a adaptor shackle 62, wherein the adaptor shackle 62 is connected with a rotary lifting ring 61 of the lower resultant force tool 52, and the connection between the resultant force tool 5 and the test piece 8 is realized through a transfer mode.
Referring to fig. 3, the adapter shackle 62 includes a U-shaped rod 63 and a second pin 64 inserted on the U-shaped rod 63. As shown in FIG. 1, the U-shaped rod 63 is connected with the rotary hanging ring 61, so that the convenience of operation during connection is enhanced, and the second pin shaft 64 is connected with the test piece 8 through the wrapping belt 13, so that the fixing tightness is effectively improved.
One end of each individual steel spring 1 is connected to the catenary hook 4 and the other end is connected to the U-shaped rod 63.
Considering that the steel spring 1 slides on the U-shaped rod 63 after being hung on the U-shaped rod 63, in a preferred embodiment, a stopper is provided at a portion of the U-shaped rod 63 connected to the hanger of the steel spring 1, as shown in fig. 3. Preferably, the limiting portion is a protrusion 11 or a groove.
When the limiting part is a bulge, the number of the bulges is 2, a gap is reserved between the 2 bulges, and the hook of the steel spring 1 is clamped in the gap; when the limiting part is a groove, the hook of the steel spring 1 falls into the groove.
Through set up spacing portion on U type pole 63, can prevent that steel spring 1 from hanging behind U type pole 63 and sliding on U type pole 63, improve the stability of steel spring 1 on U type pole 63 greatly.
Based on the protection of the structure of the steel spring 1 itself and in order to prevent the test piece 8 from falling accidentally to cause a safety accident, a protection piece (e.g., a wire rope 7) is further provided on the steel spring 1 in this embodiment. Specifically, one end of the steel wire rope 7 is connected with the hanging chain lifting hook 4, and the other end is connected with the transfer shackle 62, so that the steel spring 1 can be well protected through the steel wire rope 7. Or one end of the steel wire rope 7 is connected with an upper resultant force tool 51, and the other end is connected with a lower resultant force tool 52. In the embodiment, according to the weight borne by the steel spring 1, the steel wire rope 7 with the safety coefficient of 3 times is designed and selected for protection, so that the safety is effectively improved.
Since the test piece of this embodiment is heavy (30 tons or more), if it accidentally falls, it will be damaged directly, resulting in immeasurable losses. In a further possible embodiment, the invention thus provides a further structure for preventing accidental dropping of the test piece, namely an additional strap 13, which strap 13 is directly suspended from the catenary hook 4, as shown in fig. 1. Under normal conditions, the bag belt does not bear force, only bears force when unexpected situations occur, does not influence the normal running of the modal test, can prevent the test piece from accidentally falling, and effectively improves the safety of the modal test.
Further improving the safety of the modal test, in a preferred embodiment, a spare hoist chain 10 is provided adjacent each hoist chain 3. The spare hoist chain 10, like the other hoist chains, extends from the hoist beam 2 and is connected to the hoist chain hook 4. Specifically, the hanging chain lifting hook 4 is provided with the connecting hanging ring 12, the standby hanging chain 10 is connected with the connecting hanging ring 12, and the length of the standby hanging chain 10 is larger than that of the hanging chain 3 to be protected, as shown in fig. 9, so that under normal conditions, the standby hanging chain 10 does not bear force, only bears force when unexpected conditions occur, normal running of a modal test is not affected, unexpected dropping of a test piece can be prevented, and safety of the modal test is further improved. The steel springs can be freely matched with a single steel spring or a plurality of steel springs connected in parallel according to the weight and frequency requirements of the test piece, are not limited to the combination of the two independent steel springs and a group of steel springs, and can be adjusted in connection form according to specific actual requirements.
The invention also provides a modal test system comprising the modal test suspension device, and the assembly efficiency of the modal test system can be effectively improved by selecting a single steel spring or connecting a plurality of steel springs in parallel for free collocation, so that the simulation of the natural frequency boundary condition of the system is ensured, and meanwhile, the accuracy of the modal test of the test piece is improved.
The vertical mode test system can form a vertical mode test consisting of a test piece-suspension device, the test piece can be in a free-free boundary condition through the suspension device, and the rigid motion frequency of the suspension device in the vertical direction is lower than 1/3 of the fundamental frequency of the test piece. Specifically, the rigid motion frequency in the vertical direction of the suspension device of the invention is 1/5 of the fundamental frequency of the test piece.
Before the test, the weight of the steel spring needed by each suspension point is calculated according to the mass of the test piece, the mass center and the position size of the suspension point from the mass center. Meanwhile, according to the structural fundamental frequency requirement of a test piece, technical indexes such as steel wire diameter, outer diameter, rotation direction, stretching length, bearing capacity and the like of the steel spring are designed, and a single steel spring or a plurality of steel springs with the same tonnage are selected for combined use.
And then connecting one end of the single steel spring or the grouped steel springs used in parallel connection to the hanging chain lifting hook according to the selected single steel spring, connecting the other end of the single steel spring or the other end of the grouped steel springs with the test piece, and finally lifting to the height required by actual excitation through the hanging chain lifting hook.
In this embodiment, the test piece is 20 meters long, weighing 30 tons and having a fundamental frequency of 3Hz. According to the mass, the mass center and the reinforcing frame position, a three-point suspension mode is adopted, the load bearing calculation is carried out according to three suspension points, the extension length of the designed steel spring is 250mm, in order to achieve the test effect, the three-point suspension is respectively designed into 1 7T steel spring device, 2 7T steel spring devices are combined, 1 5T steel spring device meets the use requirement of fundamental frequency, and a steel wire rope protection device with a 3-time safety coefficient is used. In an actual modal test, the test piece is not only in a free-free boundary condition, but also the rigid motion frequency of the suspension device in the vertical direction is 1/5 of the fundamental frequency of the test piece, the test piece structure modal parameter measurement effect is good, and the test data are accurate and effective.
Example two
In another embodiment of the present invention, a suspension method for performing a modal test using the suspension device of the first embodiment is provided, including the following steps:
Designing technical parameters of a steel spring contained in the suspension assembly, wherein the technical parameters comprise the wire diameter, the outer diameter, the rotation direction and the stretching length of the steel spring and the bearing capacity of the steel spring;
And hanging the test piece by using a hanging assembly according to the determined technical parameters so as to enable the test piece to be in a free-free boundary condition.
In the specific method, the design method of the technical parameters is to determine the technical parameters of the spring according to the axial deformation born by the steel spring, wherein the calculation formula of the axial deformation is as follows:
In the above formula:
Lambda is the axial deflection in units of: mm;
n is the effective number of turns of the spring, unit: a ring;
G is the shear modulus of the spring material, unit: pa;
d is the diameter of the material, unit: mm;
D 2 is the outer diameter of the spring, unit: mm;
d is the spring pitch diameter, unit: mm;
C is the rotation ratio, unit: c=d/D;
f is the axial pressure in units of: n.
The number of turns n of the spring is:
The spring has the following rigidity:
the suspension method further comprises the step of suspending the resultant force tool, and the method comprises the following steps:
1. The 16-ton rotary lifting ring is arranged on the upper combined force tool through the threads (M56 is 5.5), and is lifted by a crane (convenient for subsequent installation).
2. Two lifting rings 53 are respectively arranged on two sides of the upper resultant force tool 51 through threads (M80 x 4.5), the directions of grooves of the lifting rings 53 are good during installation, and the directions are required to be consistent, so that the steel spring 1 can be conveniently installed.
3. The steel spring 1 is placed at the top end of the groove of the hanging ring 53, the first pin shaft penetrates through the middle hole of the hanging ring 53, the steel spring 1 is hung on the first pin shaft, an M48 nut and a pin are arranged on one side of the first pin shaft, and the first pin shaft is prevented from falling off. The other side is also the same hanging method.
4. The pressing block 55 is fixed on the upper resultant force tool 51 through two M20 screws, the fixing plate 54 is arranged on the pressing block 55 and fixed through 2M 10 screws, and the fixing plate 54 is used for preventing the steel wire rope for protection from falling off.
The suspension method of the lower resultant force tool is similar to that of the upper resultant force tool.
In actual operation, the specific model of the steel spring is not limited, the type of the steel spring comprises one or a combination of more than one of a 1.5T steel spring, a 3T steel spring, a 5T steel spring and a 7T steel spring, and the actual selection is carried out according to the specific actual condition, and the technical indexes of the models are shown in Table 1.
Table 1 technical index of steel springs of various numbers
Note that: in the table, the unit of the wire diameter and the outer diameter of the spring is mm, and the unit of the hardness is HRC.
The vertical mode test consisting of the test piece-suspension device can be formed by the mode test suspension method, the test piece can be in a free-free boundary condition, and the rigid motion frequency of the steel spring in the vertical direction is lower than 1/3 of the fundamental frequency of the test piece. Specifically, the rigid motion frequency in the vertical direction of the suspension device of the invention is 1/5 of the fundamental frequency of the test piece.
Before the test, the weight of the steel spring needed by each suspension point is calculated according to the mass of the test piece, the mass center and the position size of the suspension point from the mass center. Meanwhile, according to the structural fundamental frequency requirement of a test piece, technical indexes such as steel wire diameter, outer diameter, rotation direction, stretching length, bearing capacity and the like of the steel spring are designed, and a single steel spring or a plurality of steel springs with the same tonnage are selected for combined use.
And then connecting one end of the single steel spring or the grouped steel springs used in parallel connection to the hanging chain lifting hook according to the selected single steel spring, connecting the other end of the single steel spring or the other end of the grouped steel springs with the test piece, and finally lifting to the height required by actual excitation through the hanging chain lifting hook.
In this embodiment, but the test piece adopts the three-point suspension mode according to quality, barycenter and reinforcing frame position, and the test piece fundamental frequency is 3Hz, according to three suspension point load bearing calculation, and design steel spring tensile length is 250mm, in order to reach experimental effect, three-point suspension designs into 1 7T steel spring device respectively, and 2 7T steel spring devices of resultant force, 1 5T steel spring device, satisfies the fundamental frequency operation requirement to use 3 times factor of safety's wire rope protection device. In an actual modal test, the test piece is not only in a free-free boundary condition, but also the rigid motion frequency of the suspension device in the vertical direction is 1/5 of the fundamental frequency of the test piece, the test piece structure modal parameter measurement effect is good, and the test data are accurate and effective.
The invention also provides a modal test method, which comprises the suspension method of the modal test, and compared with the prior test method, the modal test method has the advantages that the operation steps are simpler, more convenient and quicker, and the test time is greatly saved.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (10)
1. A method of suspending a modal test comprising the steps of:
Designing technical parameters of a steel spring contained in the suspension assembly, wherein the technical parameters comprise the wire diameter, the outer diameter, the rotation direction and the stretching length of the steel spring and the bearing capacity of the steel spring;
suspending the test piece by using a suspension assembly according to the determined technical parameters so as to enable the test piece to be in a free-free boundary condition;
the suspension method of the modal test is completed by a modal test suspension device, and the modal test suspension device comprises: a suspension assembly;
the suspension assembly comprises a plurality of steel springs, and technical parameters of the steel springs are determined according to the weight and the fundamental frequency of the test piece;
the steel springs comprise a plurality of steel springs which are arranged in parallel, and at least one group of steel springs which are connected in parallel;
The test piece is suspended on the suspension chains through a lifting hook respectively by each steel spring and each group of steel springs;
The modal test suspension device is used for realizing high-precision parameter measurement of modal tests of aerospace products with the length of more than 20 meters, the volume of larger and the weight of more than 30 tons;
Each group of steel springs is provided with a resultant force tool, a plurality of steel springs are connected to the resultant force tools in parallel, and the hanging chain lifting hook is connected with the resultant force tools;
the resultant force tool comprises a main body, a rotary hanging ring, a fixed plate, a pressing block and a first pin shaft;
The rotary lifting ring comprises a rotary main body and a ring part, the rotary main body is connected with the main body, the pressing blocks are fixed on the main body, and the two pressing blocks are respectively positioned at two ends of the main body;
The fixing plate is L-shaped and is fixed with the pressing block, and a gap is formed between the fixing plate and the main body;
the lifting ring is in a ladder column shape and comprises a first column body and a second column body, the first column body is a cylinder, and the lower surface of the first column body is connected with the upper surface of the second column body; the first column body is connected with the main body to realize the fixed connection of the hanging ring and the main body;
The second column is provided with a groove with an opening facing away from the direction of the first column, the groove does not extend to the upper surface of the second column along the axial direction of the second column, but radially penetrates through the side wall of the second column, the groove divides the second column into two opposite side columns, each side column is provided with a radial through hole, and the first pin shaft penetrates through the two radial through holes;
The first pin shaft is provided with a pin hole through which the pin passes to prevent the first pin shaft from falling off; the first pin shaft and the hanging ring form a gap for the hook of the steel spring to pass through.
2. The suspension method for the modal test according to claim 1, wherein the method for designing the technical parameters of the steel spring comprises the steps of: and determining the technical parameters of the spring according to the axial deformation born by the steel spring.
3. A suspension method for a modal test according to claim 2, characterized in that the amount of axial deformation to which the steel spring is subjected is determined based on the weight of the test piece and the fundamental frequency.
4. A method of suspending a modal test according to claim 2, characterised in that the rigid body frequency of the steel spring in the vertical direction is 1/5 times the fundamental frequency of the test piece.
5. A method of suspending a modal test according to claim 2, wherein the suspension assembly is used to suspend the test piece in a three-point suspension manner.
6. The method of claim 5, wherein the steel springs each have a tensile length of 250mm.
7. A method of suspending a modal test according to any one of claims 1 to 6, wherein the method of suspending the test piece using a suspension assembly comprises:
The suspension arm is connected with a suspension rope, and then the test piece is suspended on the suspension rope through a connecting component.
8. A method of suspension for a modal test according to any one of claims 1 to 6, characterised in that the type of steel springs comprises one or a combination of several of 1.5T steel springs, 3T steel springs, 5T steel springs, 7T steel springs.
9. The method of claim 7, wherein the test piece has a fundamental frequency of 3-5Hz.
10. A method of modal testing comprising the suspension method of modal testing according to any one of claims 1 to 9.
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