CN109724873B - CT sample crack propagation test fixture suitable for tension and compression loads - Google Patents
CT sample crack propagation test fixture suitable for tension and compression loads Download PDFInfo
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- CN109724873B CN109724873B CN201910088626.5A CN201910088626A CN109724873B CN 109724873 B CN109724873 B CN 109724873B CN 201910088626 A CN201910088626 A CN 201910088626A CN 109724873 B CN109724873 B CN 109724873B
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Abstract
The invention discloses a CT sample crack propagation test fixture suitable for tension and compression loads, which can apply stable tension and compression alternating loads to a CT sample. The chuck is connected with a special CT sample through a pin; the inclined surface of the wedge-shaped block is attached to the inclined groove of the chuck, and the upper surface of the wedge-shaped block is attached to the bottom surface of the pressing block; the arc-shaped bulge of the pressing block clamps a notch of a specially-made CT sample; the hoop is sleeved on the chuck, and the fastening screw is connected with the hoop through threads and props against the side face of the wedge-shaped block; the upper end of the metal rod is connected with the fatigue machine clamp through a screw hole in the center of the fastening disc; the fastening nut is attached to the bottom surface of the chuck; a circle of screws are arranged on the fastening disc; the screw withstands the fatigue machine clamp. The invention can ensure that no clearance is generated between the clamp and the sample when the tension-compression alternating load is loaded, and the loading axis is kept unchanged. Meanwhile, the invention is suitable for CT samples with different sizes and is convenient to install.
Description
Technical Field
The invention relates to metal material fatigue performance test equipment, in particular to the field of design and manufacture of uniaxial tension/compression fatigue test clamps of metal materials, and particularly relates to a CT sample crack propagation test clamp suitable for tension and compression loads.
Background
The rotor part of the aircraft engine bears huge fatigue load, is mostly in a high-temperature and corrosive environment and is easy to crack. Cracks in parts such as compressor blades, compressor disks, turbine blades, turbine disks and the like can have a serious impact on the safety of the use of aircraft engines. It is therefore necessary to study the crack propagation rate of rotating parts under fatigue load. Research shows that the crack propagation rate and the stress ratio of the fatigue load and other characteristic parameters have close relation, and the crack propagation rate under the tension-tension fatigue load and the tension-compression fatigue load is greatly different. Therefore, it is necessary to design a crack propagation test under fatigue loads with different stress ratios, which requires that the test fixture can adapt to the fatigue loads with different stress ratios such as tension-compression, tension-tension and the like.
The standard compact tensile test sample (CT test sample for short) recommended in GB-T6398 can be used for experimental study on the propagation rate of a type of cracks. An axial fatigue load is applied through the pin hole, which generates stress concentration at the position of the pre-crack, causing the crack to be initiated and propagated. However, there are significant problems with the test fixture when tensile-compressive fatigue loads are applied: the load inevitably passes through a condition where the load is zero during the change between tension and compression. If the pin clearance fit is adopted to install the test piece, a section of idle stroke can occur when the load is zero, the loading of a fatigue machine is not facilitated, the loading is not consistent with the actual fatigue load, and meanwhile impact load on the pin can be caused, so that the fatigue failure of the pin is caused.
The Chinese invention patent CN 105004607A discloses a tension-compression integrated experiment clamp for a universal testing machine, but the problem mainly solved is that a plate is bent when being compressed, and the idle stroke problem when the tension-compression load of a CT sample is changed can not be directly solved.
The Chinese invention patent CN 106885729A discloses a high-temperature tension-compression fatigue test fixture for a flat plate test piece, which can solve the problem of looseness of a wedge-shaped friction chuck during reverse loading. However, the CT sample is originally connected to the clamp through the pin, and if the CT sample is connected by friction, the loading axis is changed, which affects the experimental result. Therefore, the problem in the CT sample tension and compression test cannot be solved.
The Chinese invention patent CN 104792612A discloses a high-temperature tension-compression fatigue test fixture for a hollow round bar test piece, which solves the problem of thread clearance in the tension-compression process of the hollow round bar test piece. However, the clamp is only suitable for the round bar standard sample and cannot be applied to the CT sample.
Chinese utility model CN 205898563U discloses a hydraulic clamping device for thin-wall flat plate test piece high-frequency fatigue test. However, this clamping method is not suitable for testing CT samples, and in particular it cannot ensure that the loading axis is the direction of the test design.
In summary, the design of the existing test fixture cannot be used for realizing the tension and compression load in the process of the crack propagation test of the CT sample, and the fixture needs to be additionally designed to adapt to the tension and compression fatigue load.
Disclosure of Invention
The technical problem solved by the invention is as follows: overcome the problem in the prior art, provide a CT sample crack propagation test anchor clamps that adapts to and draw pressure load, satisfy the CT sample and draw the demand of pressing centre gripping under the fatigue load, concrete requirement includes: (1) the idle stroke of the clamp in the tension and compression fatigue load change process is solved; (2) the loading axis is kept unchanged no matter tension or pressure is ensured; (3) the clamp is convenient to replace for CT samples with different sizes; (4) the assembly is convenient.
The solution of the invention is: a CT specimen crack propagation test fixture adapting to tension and compression loads comprises: the device comprises a chuck, a wedge-shaped block, a pressing block, a hoop, a fastening screw, a pin, a special CT sample, a metal rod, a fastening nut, a fastening disc and a screw; a pin hole is arranged on the chuck and is connected with a special CT sample through a pin; the inclined plane of the wedge block is contacted with the inclined plane at the inner side of the chuck; the lower surface of the pressing block is in contact with the upper surface of the wedge-shaped block, and the upper surface of the pressing block is provided with a notch which is convex and used for clamping the lower surface of a specially-made CT sample; the ferrule sleeves the chuck; the fastening screw is connected with the threaded hole in the hoop and screwed tightly against the side face of the wedge-shaped block; the upper end of the metal rod penetrates through the fastening nut and is connected with the threaded hole on the lower surface of the chuck; the fastening nut is screwed tightly to prop against the lower surface of the chuck; the lower end of the metal rod penetrates through the fastening disc and is connected with the fatigue machine clamp through threads; and a circle of screw is arranged on the fastening disc and screwed down to prop against the fatigue machine clamp.
When the load applied by the fatigue machine is tensile force, the tensile force is transmitted to the metal rod through the threads by the fatigue machine clamp; the metal rod is connected with the chuck through upper end threads to transmit the pulling force to the chuck; the collet transfers the pulling force to a specially prepared CT specimen through a pin.
When the load applied by the fatigue machine is pressure, the pressure is transmitted to the fastening disc by the fatigue machine clamp through the screwed screw, and then is transmitted to the metal rod through the thread; the metal rod transmits the pressure to the fastening nut through the upper end thread, and the fastening nut transmits the pressure to the chuck; the clamping head transmits pressure to the wedge-shaped block through the inclined surface, and then transmits the pressure to the pressing block contacted with the wedge-shaped block; the pressure block transmits the pressure to the special CT sample through the circular arc protrusion.
Compared with the existing CT sample crack propagation test fixture scheme, the invention has the advantages that:
(1) the invention can adapt to tension-compression fatigue load, and the clamp has no idle stroke in the tension-compression load change process;
(2) the invention can ensure that the loading axis keeps unchanged for the applied tension and compression load;
(3) the clamp is convenient to replace for samples with different sizes. For CT samples with different sizes, the test requirements can be met only by replacing wedge blocks and pressing blocks with different sizes;
(4) the invention is convenient to assemble.
Drawings
FIG. 1 is an assembly view of the jig of the present invention (only the lower half of the whole set of the jig is shown, and the upper half is identical to the upper half), wherein FIG. 1(a) is an external view; FIG. 1(b) is a divided external view; fig. 1(c) is an enlarged external view after division.
Fig. 2 is a schematic view of a chuck 1 of the jig of the present invention, wherein fig. 2(a) is an external view; fig. 2(b) is an external view after being divided.
Fig. 3 is an external view of a wedge 2 of the jig of the present invention;
FIG. 4 is an external view of a pressing block 3 of the jig of the present invention;
FIG. 5 is an external view of ferrule 4 of the clip of the present invention;
FIG. 6 is an external view of a fastening screw 5 of the jig of the present invention;
FIG. 7 is an external view of a pin 6 of the jig of the present invention;
FIG. 8 is an external view of a tailored CT sample 7;
FIG. 9 is an external view of the metal rod 8 of the clip of the present invention;
FIG. 10 is an external view of a fastening nut 9 of the clip of the present invention;
FIG. 11 is a front view of the fastening plate 10 of the clamp of the present invention;
Detailed Description
The invention designs the CT sample crack propagation test fixture suitable for tension and compression loads.
In the actual test process, the whole set of the fixture comprises two fixtures of the invention, which are divided into an upper fixture and a lower fixture which are respectively connected with two pin holes of a specially-made CT sample 7.
When the clamp is used, the specific method is as follows:
and (I) respectively assembling an upper clamp and a lower clamp, and connecting with a specially-made CT sample 7. The specific method comprises the following steps:
1. firstly, inserting the wedge-shaped block 2, the pressing block 3 and the specially-made CT sample 7 into the chute of the chuck 1, ensuring that the inclined surface of the wedge-shaped block 2 is attached to the chute of the chuck 1, the lower surface of the pressing block 3 is attached to the upper surface of the wedge-shaped block 2, and the notch of the CT sample 7 is attached to the arc-shaped protrusion of the pressing block 3. The pin 6 is inserted by aligning the special CT sample 7 with the pin hole of the chuck 1.
2. A ferrule 4 is sleeved on the outer sleeve of the chuck 1, and a threaded hole of the ferrule 4 is aligned with the longer side of the wedge block 2. A fastening screw 5 is screwed into the threaded hole of the ferrule 4 and abuts against the side of the wedge-shaped block 2.
3. The fastening nut 9 is screwed into the thread of the upper end of the metal rod 8 and the thread of the upper end of the metal rod 8 is connected to the chuck 1.
4. The fastening plate 10 is screwed into the screw thread at the lower end of the metal rod 8, and the screw 11 is screwed into the screw hole around the fastening plate 10.
And (II) resetting the tension of the fatigue machine, and respectively connecting the threads of the metal rods 8 of the upper clamp and the lower clamp with the upper universal clamp and the lower universal clamp with threaded holes of the fatigue machine.
And thirdly, applying tension to the whole set of fixture and the sample through a fatigue machine to enable the whole set of fixture to be subjected to the tension and eliminate gaps between the threads and the threaded holes and between the pins and the pin holes. The applied tension is required to be no greater than the maximum load in the test and does not affect the test results.
And (IV) under the condition that the clamp is pulled, tightening the following three screws and nuts:
1. tightening the fastening screw 5 to prop against the side surface of the wedge-shaped block 2;
2. tightening the fastening nut 9 to prop against the lower surface of the chuck 1;
3. the screws 11 are tightened against the fatigue machine clamp surface.
And (V) unloading the tension of the fatigue machine to zero. And finishing the installation of the test fixture.
Claims (4)
1. The utility model provides an adaptation CT sample crack propagation test anchor clamps of tension and compression load which characterized in that contains: the device comprises a chuck (1), a wedge-shaped block (2), a pressing block (3), a hoop (4), a fastening screw (5), a pin (6), a special CT sample (7), a metal rod (8), a fastening nut (9), a fastening disc (10) and a screw (11); a pin hole of the chuck (1) is connected with a special CT sample (7) through a pin (6); the inclined surface of the wedge-shaped block (2) is attached to the inclined groove of the chuck (1), and the upper surface of the wedge-shaped block (2) is attached to the bottom surface of the pressing block (3); the arc-shaped bulge of the pressing block (3) clamps a notch of a special CT sample (7); the ferrule (4) sleeves the chuck (1); the fastening screw (5) is connected with the hoop (4) through threads and props against the side face of the wedge-shaped block (2); the upper end of the metal rod (8) is threaded through the fastening nut (9) and connected with a threaded hole at the bottom of the chuck (1), and the lower end of the metal rod (8) is threaded through a threaded hole at the center of the fastening disc (10) and connected with the fatigue machine clamp; the fastening nut (9) is attached to the bottom surface of the chuck (1); a circle of screws (11) are arranged on the fastening disc (10); the screw (11) is pressed against the fatigue machine clamp.
2. The CT specimen crack propagation test fixture of claim 1, wherein: the fastening screw (5) is screwed down to prop against the side face of the wedge-shaped block (2), so that a gap between the pressing block (3) and a special CT sample (7) can be eliminated.
3. The CT specimen crack propagation test fixture of claim 1, wherein: the fastening nut (9) is screwed to prop against the bottom surface of the chuck (1), so that a gap between the chuck (1) and the upper end thread of the metal rod (8) can be eliminated.
4. The CT specimen crack propagation test fixture of claim 1, wherein: the screw (11) is screwed down to prop against the fatigue machine clamp, so that a gap between the lower end thread of the metal rod (8) and the fatigue machine clamp can be eliminated.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910088626.5A CN109724873B (en) | 2019-01-30 | 2019-01-30 | CT sample crack propagation test fixture suitable for tension and compression loads |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910088626.5A CN109724873B (en) | 2019-01-30 | 2019-01-30 | CT sample crack propagation test fixture suitable for tension and compression loads |
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| Publication Number | Publication Date |
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| CN109724873A CN109724873A (en) | 2019-05-07 |
| CN109724873B true CN109724873B (en) | 2020-06-19 |
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| CN201910088626.5A Active CN109724873B (en) | 2019-01-30 | 2019-01-30 | CT sample crack propagation test fixture suitable for tension and compression loads |
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Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110631902B (en) * | 2019-10-31 | 2024-05-28 | 浙江工业大学 | Clamp convenient to safely and quickly install CT (computed tomography) sample |
| CN111175158A (en) * | 2020-02-10 | 2020-05-19 | 天津大学 | Open structure corner fatigue and crack propagation measurement sample |
| CN113804537B (en) * | 2021-08-05 | 2022-08-16 | 北京航空航天大学 | Clamp capable of applying pull/press cyclic load to CT test piece |
| CN114942185A (en) * | 2022-04-13 | 2022-08-26 | 北京理工大学 | In-situ mechanical loading testing machine, testing system and testing method |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2000147182A (en) * | 1998-11-17 | 2000-05-26 | Mitsubishi Heavy Ind Ltd | Method and device for monitoring toughness of reactor vessel support structure member |
| CN201382880Y (en) * | 2009-02-24 | 2010-01-13 | 河北省电力研究院 | Connecting rod chuck for measuring displacement of loading line of small-sized CT sample |
| US9188519B2 (en) * | 2012-09-11 | 2015-11-17 | The United States Of America, As Represented By The Secretary Of Commerce | Multiple specimen testing |
| CN104142266B (en) * | 2014-07-31 | 2016-08-24 | 浙江大学 | High pressure hydrogen environment Material Testing Machine compact tensile specimen fixture |
| CN106885729B (en) * | 2017-04-05 | 2018-07-03 | 北京航空航天大学 | The high temperature push-pull fatigue test cramp and method of a kind of flat test piece |
| CN109030194B (en) * | 2018-08-01 | 2023-12-15 | 长沙理工大学 | Assembled fixture for fatigue crack growth rate test |
| CN109470468B (en) * | 2018-12-29 | 2020-08-07 | 北京航空航天大学 | High-low cycle composite fatigue test fixture of turbine joggle joint structure |
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