CN111256935B - Blade vibration test method and vibration test tool - Google Patents
Blade vibration test method and vibration test tool Download PDFInfo
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- CN111256935B CN111256935B CN202010246978.1A CN202010246978A CN111256935B CN 111256935 B CN111256935 B CN 111256935B CN 202010246978 A CN202010246978 A CN 202010246978A CN 111256935 B CN111256935 B CN 111256935B
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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
- G01M7/00—Vibration-testing of structures; Shock-testing of structures
- G01M7/02—Vibration-testing by means of a shake table
- G01M7/027—Specimen mounting arrangements, e.g. table head adapters
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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
- G01M7/00—Vibration-testing of structures; Shock-testing of structures
- G01M7/02—Vibration-testing by means of a shake table
- G01M7/025—Measuring arrangements
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Abstract
The invention discloses a blade vibration test method and a vibration test tool, on the basis of the equipment capability of the existing domestic and foreign vibration tables, by means of a computer three-dimensional design and a simulation analysis technology and through continuous parameter iteration and optimization, the first-order resonance frequency of a designed and formed cantilever beam structure is close to the first-order resonance frequency of a small-size blade, and by utilizing the resonance principle, the amplitude of the free end of the cantilever beam structure is sharply increased, and correspondingly, the acceleration value is sharply increased, so that the blade is excited by the acceleration, and the blade reaches the required stress value at the first-order bending resonance frequency. And the innovation is carried out on the basis of utilizing the existing equipment, advanced equipment is not purchased or expensive materials are not used, the cost is greatly reduced while the problem is solved, and the efficiency is improved.
Description
Technical Field
The invention belongs to the technical field of strength tests of parts and components of an aero-engine, and particularly relates to a vibration test method and a vibration test tool for a small-size blade.
Background
In order to obtain higher compressor pressure ratio of an aircraft engine and a gas turbine, the design stage number of a high-pressure compressor can reach dozens of stages, the size of a blade is reduced along with the increase of the stage number, the length of the last stage blade is less than 50mm, the first-order resonance frequency is higher than 3000Hz, and the fatigue strength is required to be more than 400 MPa. The test shows that: a foreign vibration fatigue test bench is used for carrying out fatigue test on 3500Hz small-size blades, and when the blades are loaded to require vibration stress, the vibration table reaches the non-idle load limit output capacity of the vibration table, so that the vibration table is heated seriously and is overloaded and stopped for multiple times.
At present, the universal equipment for the vibration fatigue test of the blades at home and abroad is an electric vibration table, the frequency, the thrust, the acceleration and the like of the electric vibration table have upper limit values, and due to the additional mass of the tested blades and a tool, the working range of the vibration table is reduced, and shutdown protection is caused after the working range is exceeded; in addition, the frequency of the small-size blade is very high, and the small-size blade is 2 pi f.A according to the formula2And a is the acceleration of the table top of the vibration table, f is the excitation frequency, A is the displacement peak value of the table top of the vibration table, the displacement of the table top of the vibration table is very small, and although the g value of the table top of the vibration table is very high, the displacement of the table top is very small, so that the vibration stress actually applied to the blade body of the blade is very small. Therefore, under the condition of the capability of the current domestic and foreign equipment, the application of the vibration stress of the small-size blade becomes a technical problem.
Disclosure of Invention
The invention provides a blade vibration test method and a vibration test tool, which effectively solve the technical problem that the vibration stress of small-size blades of aero-engines and gas turbines is difficult to apply.
In order to achieve the purpose, the blade vibration test method comprises the following steps:
Furthermore, in the step 2, the material of the holding tool is 3Cr13, and in the step 3, the material of the cantilever beam is high-temperature alloy.
Furthermore, in step 3, the interface between the cantilever beam tool and the fixed tool is designed to be a symmetrical U-shaped structure.
Further, in step 3, the root transfer radius R of the cantilever beam should not be smaller than R5.
Further, in step 5, for the blade with the frequency higher than 3000Hz and the damping ratio larger than 0.5%, the size of the combined tool is adjusted by taking the frequency difference value between the combined tool and the blade within +/-1% of the first-order resonance frequency of the blade as a target.
Further, in step 5, the size of the combined tool is adjusted by adjusting the length, width and height of the cantilever beam tool.
Further, in step 6, when the cantilever beam tool is processed, surface finishing and shot peening are performed on the cantilever beam tool.
Further, in step 7, an auxiliary strain gauge is attached to the blade, and the auxiliary strain gauge is attached to a position where the stress is 60% of the stress of the maximum stress point.
A blade vibration test tool comprises a cantilever beam tool and a fixing tool, wherein the cantilever beam tool comprises a base and a cantilever beam fixed on the base, the fixing tool and the cantilever beam tool are detachably connected, a mortise for clamping a blade and a cavity for accommodating a jacking block and a jacking screw rod are arranged on the fixing tool, and the inner wall of the cavity is provided with threads; the cavity is communicated with the mortise.
Furthermore, the connection part of the root part of the cantilever beam and the base is provided with a transition arc surface.
Compared with the prior art, the invention has at least the following beneficial technical effects:
on the basis of the capability of the existing vibration table equipment at home and abroad, the invention designs the first-order resonance frequency of the formed cantilever beam structure to be close to the first-order resonance frequency of the small-size blade by means of computer three-dimensional design and simulation analysis technology through continuous parameter iteration and optimization, and utilizes the resonance principle to sharply increase the amplitude of the free end of the cantilever beam structure and correspondingly sharply increase the acceleration value, so that the blade is excited by the acceleration, and the blade reaches the required stress value at the first-order bending resonance frequency.
The cantilever beam of the blade vibration test tool is simple in structure, the vibration response of the free end is obvious in a wide range near the resonance frequency, the free end of the cantilever beam is used as an excitation source of the blade, high excitation force can be provided for the blade, and the blade can reach required stress under the condition that the g value of the table top of the vibration table is far lower than an output limit value; secondly, the design of the test tool is completed based on computer aided design and simulation analysis technology, innovation is performed on the basis of the existing equipment, advanced equipment does not need to be purchased or expensive materials do not need to be used, the problem is solved, meanwhile, the cost is greatly reduced, and the efficiency is improved.
Furthermore, in the step 3, the interface of the cantilever beam tool and the blade holding tool is designed to be a symmetrical U-shaped structure, so that the connection rigidity is increased, and meanwhile, the mounting position of the holding tool is convenient to adjust in the later period, and the purpose of frequency modulation of the combined tool is achieved.
Further, in step 3, the root transfer radius R should not be smaller than R5, so as to reduce stress concentration of the cantilever beam.
Furthermore, because the holding tool is designed according to the minimum size when the holding tool is designed, if the holding tool is large in size, the first-order frequency of the combined tool is directly reduced, the inherent frequency of the blade is deviated, and the difficulty in adjusting the size of the cantilever beam in the later period is large, in the step 5, the three-dimensional size of the cantilever beam tool is selected to be adjusted instead of the size of the holding tool.
Further, in step 6, when the cantilever beam tool is processed, surface finishing and shot peening strengthening are carried out on the cantilever beam tool, so that the fatigue strength of the cantilever beam tool is improved;
further, in step 7, an auxiliary strain gauge is attached to the blade, the auxiliary strain gauge is attached to a position where the stress is 60% of the stress of the maximum stress point, and when the main strain gauge fails due to excessive stress, the stress value of the maximum stress point is measured by using the proportional relation between the two strain gauges instead of the main strain gauge through the auxiliary strain gauge.
Drawings
FIG. 1 is a schematic diagram of a blade vibration test method;
FIG. 2 is a top view of a cantilever beam tooling structure;
fig. 3 is a schematic view of a holding fixture.
In the figure: 1-vibration table, 2-connecting screw, 3-fastening screw, 4-fixing tool, 41-tongue-and-groove, 42-cavity, 5-blade, 6-top block, 7-top screw, 8-cantilever beam tool, 81-base, 82-cantilever beam, 83-threaded hole and 84-U-shaped interface.
Detailed Description
In order to make the objects and technical solutions of the present invention clearer and easier to understand. The present invention will be described in further detail with reference to the following drawings and examples, wherein the specific examples are provided for illustrative purposes only and are not intended to limit the present invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified. In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
A blade vibration test method comprises the following steps:
and 9, after the test is finished, disassembling the blade and the tool.
Referring to fig. 1 to 3, a blade vibration test tool comprises a cantilever beam tool 8 and a fixing tool 4, wherein the cantilever beam tool 8 comprises a base 81 and a cantilever beam 82 fixed on the base 81, a transition arc surface is arranged at the joint of the root of the cantilever beam 82 and the base 81, 4 threaded holes 83 are formed in the base 81, and the cantilever beam tool 8 is fixed on a vibration table 1 through the threaded holes 83 and connecting screws 2. The two U-shaped interfaces 84 are symmetrically arranged on the side surface of the cantilever beam 82, and the two U-shaped interfaces 84 increase the connection rigidity and facilitate the adjustment of the mounting position of the later-stage holding tool 4; the fixing tool 4 is fixed on the cantilever beam tool 8 through a fastening screw 3 and a U-shaped interface 84. The fixing tool 4 is in a block shape, a mortise 41 for clamping the blade and a cavity 42 for accommodating the jacking block 6 and the jacking screw 7 are formed in the fixing tool 4, and threads are formed in the inner wall of the cavity 42; the cavity 42 communicates with the mortise 41. When the blade is subjected to a vibration test, the tenon of the blade 5 is clamped into the mortise 41, the jacking block 6 is placed into the cavity 42, and then the jacking screw 7 is gradually screwed into the cavity 42, so that the jacking screw 7 jacks the tenon of the blade 5 through the jacking block 6.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (6)
1. A blade vibration test method is characterized by comprising the following steps:
step 1, measuring a first-order natural frequency and a damping ratio of a blade;
step 2, designing a three-dimensional model of a blade holding tool, determining the shape and the size of the holding tool, wherein the holding tool (4) adopts a tenon back-pushing holding mode;
step 3, designing a cantilever beam tool three-dimensional model, determining the length, width, height and root transfer radius R of a cantilever beam of the cantilever beam tool (8), and designing an interface connected with the vibration table (1) and an interface connected with the fixed fixture (4) on the cantilever beam tool (8); the three-dimensional structure size of the cantilever beam tool (8) is positively correlated with the structure size of the blade;
step 4, rigidly combining the three-dimensional models of the fixing tool (4) designed in the step 2, the cantilever beam tool (8) designed in the step 3 and the blade (5) to form a combined tool, distributing material attributes, and carrying out modal analysis on the combined tool to obtain the resonant frequency and the vibration mode of the combined tool;
step 5, if the relative deviation of the first-order resonance frequency of the combined tool and the first-order natural frequency of the blade is larger than 2%, adjusting the size of the combined tool until the relative deviation of the frequency of the combined tool and the frequency of the blade is within +/-2% of the first-order natural frequency of the blade, and the first-order natural frequency of the combined tool and the first-order natural frequency of the blade are different;
step 6, machining a cantilever beam tool (8) and a fixed tool (4) according to the size of the combined tool obtained in the step 5;
step 7, attaching a strain gauge at the stress point of the blade (5);
step 8, installing a cantilever beam tool (8) on the vibration table (1), fixedly connecting a fixing tool (4) with the cantilever beam tool (8), and installing the blade to be measured attached with the strain gauge on the fixing tool (4) and tightly pushing and fixing the blade to be measured; starting the vibration table (1) and the strain gauge, carrying out stress loading under the first-order natural frequency of the blade, measuring the strain value of the blade by using the strain gauge, increasing the output voltage of the vibration table (1) to enable the stress of the blade to reach a required value, and recording test data;
for the blade with the frequency higher than 3000Hz and the damping ratio larger than 0.5%, the size of the combined tool is adjusted by taking the frequency difference value between the combined tool and the blade within +/-1% of the first-order natural frequency of the blade as a target;
and 5, adjusting the size of the combined tool by adjusting the length, the width and the height of the cantilever beam tool (8).
2. The blade vibration test method according to claim 1, wherein in the step 2, the material of the holding tool (4) is 3Cr13, and in the step 3, the material of the cantilever beam is high-temperature alloy.
3. The blade vibration test method according to claim 1, wherein in the step 3, the interface between the cantilever beam tool (8) and the holding tool (4) is designed to be a symmetrical U-shaped structure.
4. The blade vibration test method as claimed in claim 1, wherein in the step 3, the root transfer radius R of the cantilever beam is not less than R5.
5. The blade vibration test method according to claim 1, wherein in the step 6, when the cantilever beam tool (8) is processed, the cantilever beam tool (8) is subjected to surface finishing and shot peening.
6. The blade vibration test method according to claim 1, wherein in the step 7, an auxiliary strain gauge is further attached to the blade, and the auxiliary strain gauge is attached to a position where the stress is 60% of the stress at the maximum stress point.
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