CN116929968A - Composite material test piece and test device suitable for developing high-low cycle composite fatigue test - Google Patents
Composite material test piece and test device suitable for developing high-low cycle composite fatigue test Download PDFInfo
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- 238000012360 testing method Methods 0.000 title claims abstract description 133
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- 238000009661 fatigue test Methods 0.000 title claims abstract description 47
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
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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
- G01M7/022—Vibration control arrangements, e.g. for generating random vibrations
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
- G01N3/06—Special adaptations of indicating or recording means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0005—Repeated or cyclic
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0073—Fatigue
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/026—Specifications of the specimen
- G01N2203/0262—Shape of the specimen
- G01N2203/0268—Dumb-bell specimens
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
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- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
The invention discloses a composite material test piece and a test device suitable for carrying out high-low cycle composite fatigue test, and designs an asymmetric dumbbell type test piece which can enable a failure part to be far away from an excitation end and ensure the continuity of fibers in a fatigue assessment area. Meanwhile, an experimental device for performing high-low cycle composite fatigue test by using the asymmetric test piece is also designed, and the experimental device comprises a low cycle fatigue load loading module, a high cycle fatigue load loading module and a strain measuring module. The low-cycle fatigue load loading module applies low-cycle fatigue load with axial load retention to a test piece through a universal testing machine; meanwhile, the upper clamping head of the testing machine is connected with the upper clamping head of the test piece through a flexible belt, so that a high-cycle fatigue load with high transverse frequency and low amplitude is applied to the test piece of the test piece through an excitation rod of the vibration exciter to continuously act until the test piece breaks. And in the process, recording strain data of the test piece fatigue checking area in a fatigue test by a strain measurement module.
Description
Technical Field
The invention belongs to the technical field of mechanical engineering, relates to a composite material and a common composite fatigue state of engineering, and in particular relates to a composite material test piece and a test device suitable for carrying out a high-low cycle composite fatigue test.
Background
The fan blade of the aeroengine bears the action of high-low cycle composite fatigue (composite fatigue for short) in the service process. The composite fatigue comprises a low-cycle fatigue load (Low Cycle fatigue, abbreviated as LCF) mainly based on centrifugal load and a high-cycle fatigue load (High Cycle fatigue, abbreviated as HCF) caused by pneumatic load excitation, reference "
LUO S, WU S.Fatigue failure analysis of rotor compressor blades concerning the effect of rotating stall and surge [ J ]. Engineering Failure Analysis,2016 ]. In order to pursue higher economic benefits, the composite material gradually replaces titanium alloy for preparing the fan blade, and the complex structural characteristics of the composite material make the stress state and damage evolution process of the composite material under the composite fatigue load more complex and lack related experimental theoretical research. Therefore, the design of the composite material test piece capable of carrying out the composite fatigue test and the matched test device thereof has important engineering significance.
Current research on composite fatigue tests is mainly conducted around metallic materials. In order to facilitate the development of compound fatigue research in a laboratory, students simplify the compound fatigue load into low-cycle fatigue load with axial load retention and high-cycle fatigue load with transverse high frequency and low amplitude, and design matched test pieces and test devices to realize non-coaxial loading of the low-cycle and high-cycle fatigue loads together, reference is made to WESER S, GAMPE U, RADDATZ M, et al advanced Experimental and Analytical Investigations on Com-bined Cycle Fatigue (CCF) of Conventional Cast and Single-Crystal Gas Turbine Blades [ J ]. Proceedings of ASME Turbo Expo 2011, vancouver, 2011:19-28).
Xie Ming et al in 2002 established a composite fatigue test platform and performed two types of multiaxial fatigue tests, namely stretch bending or tension torsion, on fan blades, with reference to "MING X, SONI S R, CROSS C J, et al Multiaxial high cycle fatigue test system [ J ].2004 ]. The method is characterized in that nylon belts are selected to transmit low-cycle fatigue loads to the blades, and meanwhile, the nylon belts serve as flexible connecting pieces to enable the high-cycle fatigue loads to be transversely loaded through 2 vibration exciters. The european union proposed in the PREMECCY (Predictive Methods For Combined Cycle Fatigue In Gas Turbines) program for studying composite fatigue that the vibration characteristics of the blade structure are affected by the geometric profile, and replaces the rectangular section test piece with a feature simulator to simulate the vibration characteristics of a real blade. The test adopts a plate spring clamp with different rigidity in the orthogonal direction, and the vibration test piece reaches a resonance mode, so that the application of the transverse high-cycle fatigue load is realized. In the research of high-low cycle composite fatigue test of the tenon tooth of a turbine blade in service, a test fixture realizes the aim of simultaneously transmitting vibration high-cycle fatigue load generated by an excitation device to the tenon tooth part while the blade is in a tensile state by a bearing mechanism, and the like are referred to' Xiaojun, sun Ruijie, deng Ying, etc.
At present, a certain research result is achieved by a metal material composite fatigue test technology, but the metal material fatigue test technology is directly prolonged to be used for a composite material, so that the following problems are encountered:
(1) If the composite fatigue test of the composite material is designed by referring to the thought of preparing the characteristic simulation piece, the processing difficulty and the cost of preparing the characteristic simulation piece by the composite material are far greater than those of a metal material. The Resin Transfer Molding (RTM) process is an advanced preparation process of the existing composite material, and the process needs to obtain a fiber preform firstly, and then the preform is put into a mold to be impregnated with liquid resin for curing and molding. The relatively complex geometry of the feature simulator makes precise positioning of the fibers difficult during preform preparation, and in addition, corresponding molds must be prepared for subsequent shaping based on the geometry. If the molded composite material is directly prepared into a feature simulation member by a machining method, the continuity of the fibers of the simulation member at the examined portion cannot be ensured.
(2) The test idea of applying deflection and high cycle fatigue stress by using the transverse displacement output by the vibration exciter has the same difficulty. Since the bending stiffness of the composite standard is significantly less than that of the metal blade, the clamp is at risk of instability during testing. In addition, when one end of the standard member is bent by being transversely excited, the composite material at the reinforcing region of the fixed end (the other end) thereof is liable to fail, so that effective fatigue test data cannot be obtained.
Disclosure of Invention
Aiming at various difficulties in the prior metal composite fatigue test technology applied to composite materials, after carefully analyzing the structural characteristics and the composite fatigue load characteristics of the composite materials, the invention provides a composite material test piece and a test device suitable for developing high-low cycle composite fatigue tests, and provides a thought for composite fatigue test research of the composite materials.
The invention is suitable for carrying out a composite material test piece of a high-low cycle composite fatigue test, the whole test piece is of an asymmetric dumbbell-shaped plate structure, one end is a fixed end, the other end is an excitation end, and a connecting section is arranged between the fixed end and the excitation end; meanwhile, the position, close to the fixed end, in the connecting section is the narrowest position, so that a fatigue checking area is formed; the width of both sides of the narrowest position gradually increases.
According to the composite material fatigue test device for developing the composite fatigue test, which is designed according to the combination design of the material test piece, the composite fatigue test is realized. The composite material fatigue test device comprises three modules, namely a low-cycle fatigue load loading module, a high-cycle fatigue load loading module and a strain measurement module.
The low-cycle fatigue load loading module comprises a universal testing machine, a connection conversion mechanism, a nylon belt, an upper clamp and a lower clamp. The connection conversion mechanism is fixedly connected with an upper chuck of the universal testing machine; the upper clamp is connected with the connection conversion mechanism through a nylon belt and clamps and fixes the excitation end of the test piece; the lower clamp is fixedly connected with a lower chuck of the universal testing machine, and clamps and fixes the fixed end of the test piece.
The high-cycle fatigue load loading module comprises a vibration exciter, a signal generator and a power amplifier; the vibration exciter is connected with the power amplifier and the signal generator; the power amplifier is used for adjusting the output power of the vibration exciter; the signal generator is used for controlling the output frequency of the vibration exciter; meanwhile, an excitation rod of the vibration exciter is horizontally arranged and fixedly connected with the upper clamp; the vibration exciter can generate transverse reciprocating displacement when outputting amplitude.
The strain measurement module comprises a dynamic strain gauge and a dynamic strain gauge; the dynamic strain gauge is adhered to the test piece fatigue assessment area and connected with the dynamic strain gauge, and the dynamic strain gauge is used for collecting high-cycle fatigue strain data.
By the composite material fatigue test device, the composite fatigue load is divided into low-cycle fatigue load with axial load retention and high-cycle fatigue load with transverse high frequency and low amplitude. The whole experiment is divided into the following steps: firstly, controlling a universal testing machine to apply low-cycle fatigue load, wherein high-cycle fatigue load is not overlapped in the first low-cycle fatigue load cycle, and only strain data of a test piece when the test piece is only subjected to the low-cycle fatigue load is recorded by utilizing a dynamic strain gauge; when the second low cycle fatigue cycle reaches the load-maintaining section, starting the vibration exciter to output amplitude, applying high cycle fatigue load to the test piece, recording strain data under the continuous action of the high and low cycle compound fatigue load by the dynamic strain gauge, and continuously acting the high cycle fatigue load until the test piece breaks.
The invention has the advantages that:
1. the invention designs a test piece and a test device for the first time aiming at the composite fatigue test research of the composite material. After the structural characteristics of the composite material and the loading mode of the composite fatigue load are comprehensively considered, a special-shape test piece and a matched test device are designed, and the aim of developing the composite fatigue test of the composite material under the condition of a laboratory is fulfilled.
2. According to the invention, the standard component is finished into the asymmetric dumbbell-shaped test piece through numerical control machining, so that a fatigue check area is constructed to avoid fatigue failure of the test piece at the fixed end, and an effective target of a test result is ensured. Meanwhile, a large number of test pieces can be obtained in a short time due to simple processing technology and low cost, and the limitation of introducing additional clamps is not needed.
3. The test device disclosed by the invention utilizes the characteristic that the nylon belt can be flexibly connected, and is matched with a universal testing machine and a vibration exciter to realize the aim of non-coaxial loading of low-cycle and high-cycle fatigue loads in a test. Further simulating load characteristics of the rotor blade in service under laboratory conditions.
4. The invention utilizes the dynamic strain gauge and the dynamic strain gauge to measure the strain data of the test piece fatigue checking area in the test, can intuitively display the change rule of the strain under the composite fatigue, is convenient for calculating and obtaining the low-cycle and high-cycle fatigue stress in the test, and provides test data for the subsequent failure analysis and the establishment of a fatigue life model.
Drawings
FIG. 1 is a schematic diagram of a composite material test piece structure for carrying out a high-low cycle composite fatigue test;
FIG. 2 is a schematic diagram of the experimental device for carrying out the high-low cycle composite fatigue test;
FIG. 3 is a schematic diagram of a link conversion mechanism in an experimental device for carrying out a high-low cycle compound fatigue test;
FIG. 4 is a schematic diagram of the structure of the upper and lower clamps in the experimental device for carrying out the high-low cycle compound fatigue test;
FIG. 5 is a side view of the structure of the upper and lower clamps in the experimental device for carrying out the high-low cycle compound fatigue test;
FIG. 6 is a simplified fatigue load spectrum of a laboratory;
FIG. 7 is a graph of strain in the examined area of the test.
In the figure:
101-fixed end 102-exciting end 103-connecting section
104-reinforcing sheet 201-universal testing machine 202-connection conversion mechanism
203-nylon belt 204-upper clamp 205-lower clamp
202 a-upper joint 202 b-upper bolt 204 a-upper clamp interface
204 b-upper clamp pressing end cap 204 c-lower bolt 204 d-connecting hole
205 a-lower clamp interface 205 b-lower clamp hold down end cap 205 c-lower fitting
301-vibration exciter 302-signal generator 303-power amplifier
301 a-excitation rod 401-dynamic strain gauge 402-dynamic strain gauge
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings.
As shown in FIG. 1, the composite material test piece for carrying out the composite fatigue test is of an asymmetric dumbbell-shaped plate structure as a whole, one end is a fixed end 101, the other end is an excitation end 102, the two ends are rectangular with equal size, and a connecting section 103 is arranged between the short sides. On the premise that the characteristics of the standard dumbbell-shaped test piece are met, the position, close to the fixed end 101, of the connecting section 103 of the whole test piece is the narrowest position, and the widths of the two sides of the narrowest position gradually increase to be equal to the widths of the fixed end 101 and the exciting end 102.
In order to cope with the load characteristics of the composite material, in the process of manufacturing a test piece, firstly, processing the appearance of the composite material test piece from a rectangular shape to an asymmetric dumbbell shape through numerical control processing, and specifically, cutting a composite material plate into a standard plate-shaped rectangular shape through a plane mill grinding finish processing technology or a water jet cutting knife processing technology and other modes; and then the test piece is processed into an asymmetric dumbbell-shaped structure by adopting the same method.
An asymmetric dumbbell-shaped test piece obtained through numerical control processing is provided with a fatigue checking area at the narrowest position for composite fatigue characteristic research; the fatigue failure of the composite material test piece at the joint position of the fixed end 101 and the connecting section 103 can be avoided, but the composite material test piece breaks in the fatigue checking area, so that the failure part is far away from the excitation end 102, and the continuity of fibers in the fatigue checking area is ensured.
Aiming at the composite material test piece with the structure, the invention designs a composite material test device for developing a composite fatigue test, which mainly comprises three modules, namely a low-cycle fatigue load loading module, a high-cycle fatigue load loading module and a strain measuring module, as shown in figure 2.
The low cycle fatigue load loading module comprises a universal tester 201, a connection conversion mechanism 202, a nylon strap 203, an upper clamp 204 and a lower clamp 205.
Wherein, the universal testing machine 201 is rigidly connected with the connection conversion mechanism 202 through a self-contained chuck. As shown in fig. 3, an upper joint 202a is designed at the top end of the connection conversion mechanism 202, and the structure of the upper joint 202a needs to be designed in cooperation with the upper clamp connection part of the universal testing machine 201 itself, so that the connection conversion mechanism 202 can be fastened and connected with the upper clamp connection part of the universal testing machine 201 through the upper joint 202 a.
Lugs are designed on two sides of the bottom end of the connection conversion mechanism 202, through holes are formed in the opposite positions of the two lugs, and an upper bolt 202b passes through the two through holes and is screwed and fixed by nuts. An upper beam for connecting the nylon belt 203 is formed at the bottom of the connection converting mechanism 202 by an upper bolt 202 b.
As shown in fig. 4 and 5, the upper clamp 204 includes three sections, namely, an upper section, a middle section and a lower section, wherein the upper section of the upper clamp 204 has the same structure as the bottom end of the connection conversion mechanism 202, and also has two lugs on both sides, and a lower bolt 204c connected with the two lugs, and a lower beam for connecting the nylon strap 203 is formed on the top of the upper clamp 204 through the lower bolt 204 c.
The nylon belt 203 is ring-shaped, and is sleeved on the upper bolt 202b and the lower bolt 204c in the process that the upper bolt 202b and the lower bolt 204c pass through the lugs on two sides. The connection between the upper clamp 204 and the connection conversion mechanism 202 is realized through a nylon belt 203; and nylon strap 203 is a flexible connection that does not affect the transfer of axial loads. The width of the nylon belt 203 is larger than that of the test piece, so that the tensile load is transferred more stably in the test, and the nylon belt 203 is prevented from twisting due to deviation of the excitation rod 301a in the excitation process of the vibration exciter 301 during the test.
A plurality of connecting holes 204d are longitudinally and equally arranged at intervals on the middle section of the upper clamp 204, and when a test is performed, the excitation rod 301a of the vibration exciter 301 can be connected with the connecting holes 204d at different positions according to requirements.
The lower section of the upper clamp 204 has an upper clamp abutment surface 204a and the upper clamp compresses the end cap 204b. An inner side surface of the upper clamp butt joint surface 204a opposite to the upper clamp compression end cover 204b is provided with an equal-size rectangular groove; the circumferential dimension of the rectangular groove is the same as that of the excitation end 102 of the test piece, and the depth D is greater than half of the thickness of the test piece and is smaller than the thickness of the test pieceHalf the degree and the thickness of the reinforcement sheet 104, i.e.:where m is the specimen thickness and n is the reinforcement sheet 104 thickness. The reinforcing sheet 104 is a rectangular sheet with the same size as the fixed end 101 and the exciting end 102, and is adhered and fixed on two sides of the fixed end 101 and the exciting end 102 when the fixed end 101 and the exciting end 102 are clamped, so that the test result is prevented from being invalid due to the fact that the clamp clamps or pinches the test piece, as shown in fig. 5. Thus, one side of the excitation end 102 with the reinforcing sheet 104 adhered to the two ends is integrally arranged in the groove of the butt joint surface 204a of the upper clamp, and the other side is integrally arranged in the groove of the compression end cover 204b of the upper clamp; further, after the bolts pass through the through holes designed in the circumferential direction of the upper clamp butt joint surface 204a and the upper clamp compression end cover 204b, the bolts are matched with nuts to be screwed down, so that the upper clamp butt joint surface 204a is tightly attached to the inner side surface of the upper clamp compression end cover 204b. Because of the thickness design of the rectangular grooves on the upper clamp butt joint surface 204a and the upper clamp compression end cover 204b, two half parts of the two sides of the excitation end 102 adhered with the reinforcing sheet are respectively positioned in the two rectangular grooves, so that the clamping position has better centering property, and the test piece is ensured to be clamped; simultaneously, the upper clamp abutting surface 204a and the upper clamp pressing end cover 204b can firmly clamp the excitation end 102 between the rectangular grooves of the upper clamp abutting surface and the upper clamp pressing end cover.
The lower clamp 205 has the same structure as the lower section of the upper clamp 204, and the same points are that: the clamping device comprises a lower clamp butt joint surface 205a and a lower clamp pressing end cover 205b, wherein grooves which are formed in the lower clamp butt joint surface 205a and the lower clamp pressing end cover 205b and have the same size as the fixed end 101. The groove depth design and the clamping and fixing mode of the fixing end 101 are the same as the excitation end 102.
The lower end of the lower clamp 205 is provided with a lower connector 205c for connecting with a base connector of the universal testing machine 201; also, the structure of the lower connector 205c is designed to match the base connector connection mode of the universal testing machine 201 itself.
In the above manner, the connection between the test piece and the universal testing machine 201 is realized, and the axial low-cycle fatigue load is applied to the test piece by controlling the universal testing machine.
The high cycle fatigue load loading module comprises a vibration exciter 301, a signal generator 302 and a power amplifier 303. Wherein the exciter 301 is connected to the power amplifier 302 and the signal generator 303. The power amplifier 303 is used to adjust the output power of the exciter 301. The signal generator 302 is used for controlling the output frequency of the exciter 301. Meanwhile, an excitation rod 301a of the vibration exciter 301 is horizontally arranged and is fixedly connected with the middle section opening of the upper clamp 204. Whereby the vibration exciter 201 is displaced in a lateral direction to and fro by the upper clamp 204 when outputting the amplitude by virtue of the flexible connection characteristic of the nylon strap 203. The upper clamp 204 applies bending deflection to the test piece excitation end 102 in the transverse displacement process, so that high-cycle fatigue load acts on the test piece fatigue assessment area in the form of bending fatigue load.
The strain measurement module comprises a dynamic strain gauge 401 and a dynamic strain gauge 402; wherein, the dynamic strain gauge 401 is adhered to the test piece fatigue checking area; and is coupled to a dynamic strain gauge 402. Because of the high frequency low amplitude load characteristics of high cycle fatigue loads, the fatigue load frequency is outside the measurement range of static strain gauges, and thus the high cycle fatigue strain data needs to be acquired using dynamic strain gauges 402.
After the connection work of the three modules is completed, the preparation work of the composite fatigue test is basically completed. To facilitate the development of composite fatigue tests under laboratory conditions, the composite fatigue load is reduced to two parts: (1) low cycle fatigue loading with axially-oriented dwell; (2) The high cycle fatigue load of the transverse high frequency and low amplitude, as shown in fig. 6, the middle trapezoid line represents low cycle fatigue and the reciprocating motion represents high cycle fatigue.
In order to ensure smooth loading of the composite fatigue load in the test, first, the universal testing machine 201 is controlled to apply a low cycle fatigue load, a high cycle fatigue load is not superimposed during the first low cycle fatigue load cycle, and strain data of the test piece only subjected to the low cycle fatigue load is recorded by the dynamic strain gauge 401. When the second low cycle fatigue cycle reaches the load-maintaining segment, the vibration exciter 301 is started to output amplitude, high cycle fatigue load is applied to the test piece, the dynamic strain gauge 401 records strain data under the continuous action of the high and low cycle compound fatigue loads at the moment, and the high cycle fatigue load can continuously act until the test piece breaks.
The results show that:
the test results of the fatigue test performed by using the test piece, the experimental equipment and the method show that the composite material test piece is subjected to fatigue failure in the fatigue checking area according to the pre-design, and the failure position is far away from the fixed end 101, so that the asymmetric dumbbell type test piece is proved to be suitable for the composite fatigue test and ensures that the test result is effective. The dynamic strain gauge 402 is used for collecting data and drawing a strain change curve graph, so that the strain characteristics of the test piece fatigue assessment area under the composite fatigue load can be analyzed more intuitively. As shown in FIG. 7, when the universal testing machine 201 applies the first low cycle fatigue, the test piece is only subjected to low cycle fatigue load, and the strain curve represents the strain value under pure low cycle fatigue load and is used for calculating the low cycle fatigue stress of the test area. And applying high-cycle fatigue load in the load-maintaining section of the second low-cycle fatigue cycle, and observing the law of high-frequency reciprocating change of the strain curve to show that the strain change of the assessment area shows the composite fatigue characteristic.
And (3) knowing the stress strain value during low cycle fatigue, calculating the high cycle fatigue stress value according to the amplitude of the reciprocating change of the strain curve, and providing test data for subsequent failure analysis and fatigue life model establishment. The test result proves that the composite material test piece, the test device and the test method for developing the high-low cycle composite fatigue test have the advantage of developing the composite fatigue test of the composite material.
Claims (8)
1. One end of the composite material test piece is a fixed end, the other end is an excitation end, and a connecting section is arranged between the fixed end and the excitation end; the method is characterized in that: the whole body is of an asymmetric dumbbell-shaped plate structure, and the position, close to the fixed end, in the middle connecting section is the narrowest position, so that a fatigue checking area is formed; the width of both sides of the narrowest position gradually increases.
2. A composite test piece suitable for performing a high and low cycle composite fatigue test according to claim 1, wherein: and processing the appearance of the composite material test piece from rectangular to asymmetric dumbbell type through numerical control processing.
3. A composite material test device for developing a composite fatigue test is characterized in that: the device comprises three modules, namely a low-cycle fatigue load loading module, a high-cycle fatigue load loading module and a strain measuring module;
the low-cycle fatigue load loading module comprises a universal testing machine, a connection conversion mechanism, a nylon belt, an upper clamp and a lower clamp; the connection conversion mechanism is fixedly connected with an upper chuck of the universal testing machine; the upper clamp is connected with the connection conversion mechanism through a nylon belt and clamps and fixes the excitation end of the test piece; the lower clamp is fixedly connected with a lower chuck of the universal testing machine, and clamps and fixes the fixed end of the test piece;
the high-cycle fatigue load loading module comprises a vibration exciter, a signal generator and a power amplifier; the vibration exciter is connected with the power amplifier and the signal generator; the power amplifier is used for adjusting the output power of the vibration exciter; the signal generator is used for controlling the output frequency of the vibration exciter; meanwhile, an excitation rod of the vibration exciter is horizontally arranged and fixedly connected with the upper clamp; the vibration exciter generates transverse reciprocating displacement when outputting amplitude;
the strain measurement module comprises a dynamic strain gauge and a dynamic strain gauge; the dynamic strain gauge is adhered to the test piece fatigue assessment area and connected with the dynamic strain gauge, and the dynamic strain gauge is used for collecting high-cycle fatigue strain data.
4. A composite material testing device for performing a composite fatigue test according to claim 3, wherein: the connection mode of the connection conversion mechanism, the nylon belt and the upper clamp is as follows: an upper beam is arranged at the bottom end of the connection conversion mechanism; simultaneously, a lower beam is arranged at the top of the upper clamp; the upper beam and the lower beam are sleeved by nylon belts.
5. A composite material testing device for performing a composite fatigue test according to claim 3, wherein: the width of the nylon belt is larger than that of the test piece.
6. A composite material testing device for performing a composite fatigue test according to claim 3, wherein: the upper clamp is provided with a plurality of connecting holes at equal intervals along the longitudinal direction for connecting and fixing the excitation rod of the vibration exciter.
7. A composite material testing device for performing a composite fatigue test according to claim 3, wherein: the fixing mode between the upper clamp and the excitation end is as follows: designing an upper clamp, wherein the lower section of the upper clamp is provided with an upper clamp butt joint surface, and the upper clamp tightly presses the end cover; the inner side surface of the butt joint surface of the upper clamp, which is opposite to the compression end cover of the upper clamp, is provided with a groove with equal size, the circumferential size of the groove is the same as that of the fixed end of the test piece, the depth is greater than half of the thickness of the test piece, and the depth is smaller than the sum of half of the thickness of the test piece and the thickness of the reinforcing sheets fixed at two sides of the fixed end; one side of the fixed end of the reinforcing sheet with two ends is integrally arranged in a groove of the butt joint surface of the upper clamp, and the other side is integrally arranged in a groove of the upper clamp pressing end cover; the end cover is pressed and fixed by the upper clamp butt joint surface and the upper clamp;
the fixing mode between the lower clamp and the fixing end is the same as the fixing mode between the upper clamp and the exciting end.
8. A composite material testing device for performing a composite fatigue test according to claim 3, wherein: in the following material test process: firstly, controlling a universal testing machine to apply low-cycle fatigue load, wherein high-cycle fatigue load is not overlapped in the first low-cycle fatigue load cycle, and only strain data of a test piece when the test piece is only subjected to the low-cycle fatigue load is recorded by utilizing a dynamic strain gauge; when the second low cycle fatigue cycle reaches the load-maintaining section, starting the vibration exciter to output amplitude, applying high cycle fatigue load to the test piece, recording strain data under the continuous action of the high and low cycle compound fatigue load by the dynamic strain gauge, and continuously acting the high cycle fatigue load until the test piece breaks.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310936944.9A CN116929968A (en) | 2023-07-27 | 2023-07-27 | Composite material test piece and test device suitable for developing high-low cycle composite fatigue test |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310936944.9A CN116929968A (en) | 2023-07-27 | 2023-07-27 | Composite material test piece and test device suitable for developing high-low cycle composite fatigue test |
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| CN116929968A true CN116929968A (en) | 2023-10-24 |
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| CN202310936944.9A Pending CN116929968A (en) | 2023-07-27 | 2023-07-27 | Composite material test piece and test device suitable for developing high-low cycle composite fatigue test |
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| Country | Link |
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| CN (1) | CN116929968A (en) |
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- 2023-07-27 CN CN202310936944.9A patent/CN116929968A/en active Pending
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