CN110501217B - Creep compression clamp - Google Patents
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- CN110501217B CN110501217B CN201910913177.3A CN201910913177A CN110501217B CN 110501217 B CN110501217 B CN 110501217B CN 201910913177 A CN201910913177 A CN 201910913177A CN 110501217 B CN110501217 B CN 110501217B
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- 238000007906 compression Methods 0.000 title claims abstract description 51
- 230000006835 compression Effects 0.000 title claims abstract description 48
- 238000012360 testing method Methods 0.000 claims abstract description 111
- 230000000149 penetrating effect Effects 0.000 claims abstract description 10
- 238000012669 compression test Methods 0.000 claims description 5
- 238000000034 method Methods 0.000 abstract description 11
- 238000011900 installation process Methods 0.000 abstract description 2
- 230000032683 aging Effects 0.000 description 17
- 230000035882 stress Effects 0.000 description 10
- 230000008569 process Effects 0.000 description 7
- 239000000463 material Substances 0.000 description 6
- 238000006073 displacement reaction Methods 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 4
- 238000004088 simulation Methods 0.000 description 4
- 238000005452 bending Methods 0.000 description 3
- 238000009434 installation Methods 0.000 description 3
- 229910000838 Al alloy Inorganic materials 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
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- 235000015842 Hesperis Nutrition 0.000 description 1
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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
- G01N3/04—Chucks
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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
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/18—Performing tests at high or low temperatures
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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
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
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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
- G01N2203/0071—Creep
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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
- G01N2203/0075—Strain-stress relations or elastic constants
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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
- G01N2203/022—Environment of the test
- G01N2203/0222—Temperature
- G01N2203/0226—High temperature; Heating 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
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/025—Geometry of the test
- G01N2203/0252—Monoaxial, i.e. the forces being applied along a single axis of the specimen
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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
- G01N2203/0266—Cylindrical 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
- G01N2203/04—Chucks, fixtures, jaws, holders or anvils
- G01N2203/0423—Chucks, fixtures, jaws, holders or anvils using screws
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Abstract
The invention provides a creep compression clamp which comprises a commutator, wherein the commutator comprises an upper pressing block and a lower pressing block, triangular prism-shaped upper and lower positioning holes into which the tail ends of samples extend are respectively formed in the bottom surface of the upper pressing block and the top surface of the lower pressing block, upper and lower fastening holes penetrating through the upper and lower positioning holes from the outside are respectively formed in the positions of the side walls of the upper and lower pressing blocks corresponding to the upper and lower positioning holes, and propping parts for propping up the samples along the transverse direction of the samples are arranged in the upper and lower fastening holes. The invention optimizes the parallelism between the sample and the center of the compression clamp in the installation process, ensures the centering of the sample in the compression process, reduces the difference of left and right deformation and improves the test precision. The test stress range is enlarged, and the repeatability, the integrity and the operation safety of test data are ensured. The test steps are simplified, the test time is saved, the using amount of the sample and the using times of the machine are greatly reduced, and the method is more energy-saving and environment-friendly.
Description
Technical Field
The invention relates to creep test equipment, in particular to a creep compression clamp.
Background
Along with the rapid development of industry in China, the creep aging forming technology is also continuously improved, the creep aging forming technology is a main forming technology of large-scale wallboards such as airplanes, rockets and the like, before actual creep aging forming is carried out on materials such as aluminum alloy and the like, the creep aging forming simulation is generally carried out by finite element software, and the most suitable actual forming scheme is determined through software simulation. Before the creep aging simulation is performed on the material, the creep performance of the material is tested, a creep testing machine is commonly used, the material to be tested is processed into a sample, the sample is clamped between an upper tensile rod and a lower tensile rod of the creep testing machine, the creep stretching or compression test is performed on the sample at a set creep aging temperature, so that the stretching or compression creep amount of the sample is obtained, further a creep curve of the material is obtained, the creep curve is provided for the creep aging simulation model, and finally the creep aging simulation model is used for guiding actual creep aging.
When the existing creep testing machine is used for carrying out creep compression tests on samples, the rod-shaped samples are generally adopted for testing, external threads are arranged at two ends of each rod-shaped sample, the two ends of each rod-shaped sample are connected with a compression clamp in a direct or indirect threaded connection mode, for example, the creep compression testing device disclosed in Chinese patent 201910244627.4 is characterized in that the upper end of each sample is connected with an upper pressing block in a threaded manner, the lower end of each sample is connected with a conical positioner in a threaded manner, and the conical positioners are positioned by conical holes on a lower pressing block so as to enhance the centering of the samples. Because the screw thread is screwed and can also have the installation clearance, consequently, the sample still can exist slight left and right rocking's possibility in the pressurized process, and is not enough to the centering, and the deformation about the sample has certain difference in the creep aging test process, influences the accuracy of test data, consequently, needs a better scheme in the prior art to solve this problem.
Disclosure of Invention
The invention aims to provide a creep compression clamp for solving the problems in the background technology.
The creep compression clamp comprises a first propping part, a second propping part and a reverser which is used for being connected between an upper connector and a lower connector of a creep testing machine, wherein the reverser comprises an upper pressing block and a lower pressing block, a distance for installing a sample is kept between the upper pressing block and the lower pressing block along the stretching direction of the creep testing machine, the distance value can be adjusted, the distance is used for providing creep compression loading operation for the sample when the distance is smaller, and the distance is used for unloading the sample when the distance is larger;
the bottom surface of the upper pressing block is provided with a triangular prism-shaped upper positioning hole into which the upper end of the sample extends, the top surface of the lower pressing block is provided with a triangular prism-shaped lower positioning hole into which the lower end of the sample extends, the upper positioning hole and the lower positioning hole are aligned along the axial direction of a tensile rod of the creep testing machine, the positions, the outlines and the sizes of the upper positioning hole and the lower positioning hole are the same, the inner surfaces of the upper positioning hole and the lower positioning hole are smooth surfaces, and the diameter of an inscribed cylinder of the upper positioning hole and the lower positioning hole is larger than the diameter of the end part of the sample to be stretched, so that the sample smoothly extends;
the upper pressing block is characterized in that an upper fastening hole penetrating through the upper positioning hole from the outside is formed in the position, corresponding to the upper positioning hole, of the side wall of the upper pressing block, the axial lead of the upper fastening hole is intersected with one side edge of the upper positioning hole, the first propping component is arranged in the upper fastening hole and used for propping against the outer wall of the upper end of the sample along the axial direction of the upper fastening hole, so that the upper end of the sample is attached to the other two side walls of the upper positioning hole, tangential positional relation is formed, and the upper fastening hole is locked, and the intersection line of the two side walls is the side edge intersected with the axial lead of the upper fastening hole;
the lower fastening hole penetrating through the lower positioning hole from the outside is formed in the position, corresponding to the lower positioning hole, of the side wall of the lower pressing block, the axial lead of the lower fastening hole is intersected with one side edge of the lower positioning hole, the second propping component is arranged in the lower fastening hole and used for propping against the outer wall of the lower end of the sample along the axial direction of the lower fastening hole, so that the lower end of the sample is attached to the two side walls of the lower positioning hole, tangential position relation is formed, and the two side walls are locked, and the intersection line of the two side walls is the side edge intersected with the axial lead of the lower fastening hole;
the axial lines of the upper fastening hole and the lower fastening hole are positioned in the same plane parallel to the axial direction of the tensile rod of the creep testing machine, so that when the upper end and the lower end of the sample are respectively abutted against the tail ends of the first jacking part and the second jacking part and are respectively tangent to the upper positioning hole and the lower positioning hole, the upper end and the lower end of the sample are also just positioned in the same plane parallel to the axial direction of the tensile rod of the creep testing machine, thereby realizing the centering of the sample and preventing the sample from being bent prematurely in the creep compression test.
Preferably, the axial lead of the upper fastening hole is perpendicularly intersected with one side edge of the upper positioning hole, and the axial lead of the lower fastening hole is perpendicularly intersected with one side edge of the lower positioning hole.
Further, the upper fastening hole and the lower fastening hole are threaded holes with internal threads, the first propping part and the second propping part are bolts or screws with external threads, and the first propping part and the second propping part are respectively screwed in the upper fastening hole and the lower fastening hole towards the direction close to the sample so as to respectively fasten the sample.
Preferably, the depth of the upper positioning hole and the lower positioning hole is smaller than or equal to the length of the end part to be extended into the sample, and the depth of the upper positioning hole and the lower positioning hole is larger than or equal to 1/2 of the length of the end part to be extended into the sample, so that the firmness of clamping is ensured, and the connection between the upper lug and the lower lug of the sample and the extension device is not influenced.
Further, the commutator further comprises an upper guide rod, a lower guide rod, an upper stretching rod and an upper connecting block which are positioned above the upper pressing block, and a lower stretching rod and a lower connecting block which are positioned below the lower pressing block, wherein the upper end of the upper stretching rod is used for being connected with an upper connector of the creep testing machine, the lower end of the upper stretching rod is fixedly connected with the upper connecting block, the lower end of the lower stretching rod is used for being connected with a lower connector of the creep testing machine, the upper end of the lower stretching rod is fixedly connected with the lower connecting block, the upper guide rod sequentially penetrates through guide holes formed in the upper connecting block, the upper pressing plate and the lower pressing plate from top to bottom, the middle part of the upper guide rod is penetrated into the guide holes formed in the upper pressing block, the upper end of the upper guide rod is provided with a shaft shoulder and is fixedly connected with the upper connecting block through a first nut, and the lower end of the upper guide rod is connected with a second nut after penetrating through the guide hole in the lower pressing block; the lower guide rod sequentially passes through the lower connecting block, the lower pressing plate and the guide holes arranged on the upper pressing plate from bottom to top, the middle part of the lower guide rod is arranged in the guide holes arranged on the lower pressing plate in a penetrating mode, the upper end of the lower guide rod is connected with a third nut after passing through the guide holes on the upper pressing plate, the lower end of the lower guide rod is provided with a shaft shoulder, and the lower end of the lower guide rod is fixedly connected with the lower connecting block through the fourth nut. The upper pressing block and the lower pressing block can slide relative to the upper guide rod and the lower guide rod, and the interval between the upper pressing block and the lower pressing block for installing the sample can be manually adjusted.
The invention has at least the following beneficial effects:
according to the invention, by changing the clamping mode between the compression clamp and the rod-shaped sample, the problems of large left-right deformation gap and poor creep measurement precision of the sample caused by poor sample centering due to the installation gap between the sample and the compression clamp in the compression creep test process are solved, and the invention is mainly applied to measuring the micro deformation in the uniaxial compression creep aging test, and can solve the following problems:
1. the parallelism between the sample and the center of the compression clamp in the installation process is optimized, the centering of the sample in the compression process is ensured, the difference between the left deformation and the right deformation is reduced, and the measurement accuracy of the micro deformation can be obviously improved.
2. The problem that the aging time cannot meet the test requirement due to easy bending of the sample under a higher stress level is solved, the test stress range is enlarged, the integrity of test data is ensured, and a more comprehensive test result is provided for scientific research.
3. The probability of instability and bending of the sample in the compression process is reduced, so that the stability of the sample is better, and the safety of a test machine is well ensured. And the accuracy and the repeatability of test measurement data are good, the phenomenon that repeated tests are needed when the traditional compression clamp is used is avoided, the test steps are simplified, the test time is saved, the using amount of a sample and the using times of a machine are greatly reduced, and the device is more energy-saving and environment-friendly.
When the creep compression clamp is used for a test, the external thread structures at two ends of the existing rod-shaped sample can be changed into smooth cylindrical structures and used for extending into the upper positioning hole and the lower positioning hole, so that on one hand, the contact area between the sample and the positioning hole can be increased, the clamping firmness of the sample is enhanced, and on the other hand, the steps required by processing the sample to a finished product can be reduced, and labor and cost are saved.
In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The present invention will be described in further detail with reference to the drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
FIG. 1 is an overall mounting block diagram of a creep compression jig according to a preferred embodiment of the present invention;
FIG. 2 is an enlarged detail view of a sample clamping location of a creep compression jig according to a preferred embodiment of the invention;
FIG. 3 is a schematic view of the structure of the creep compression jig of the preferred embodiment of the present invention in internal section at the clamping location of the test specimen;
FIG. 4 is a graph of deformation versus time for a first set of first compressive creep test runs with a prior art compression clamp;
FIG. 5 is a graph of deformation over time for a first set of second compressive creep test runs with a prior art compression clamp;
FIG. 6 is a graph of deformation versus time for a second set of compressive creep tests conducted with a creep compression clamp according to a preferred embodiment of the present invention;
FIG. 7 is a graph of deformation over time for a third set of compressive creep tests performed with a creep compression clamp according to a preferred embodiment of the invention.
In the figure: 1-upper press block, 11-upper positioning hole, 12-upper fastening hole, 13-upper guide rod, 14-upper stretching rod, 15-upper connecting block, 16-first nut, 17-third nut, 2-lower press block, 21-lower positioning hole, 22-lower fastening hole, 23-lower guide rod, 24-lower stretching rod, 25-lower connecting block, 26-second nut, 27-fourth nut, 3-sample, 4-first propping component and 5-second propping component.
Detailed Description
Embodiments of the invention are described in detail below with reference to the attached drawings, but the invention can be implemented in a number of different ways, which are defined and covered by the claims.
Referring to fig. 1 to 3, a creep compression clamp comprises a first tightening part 4, a second tightening part 5 and a reverser for connecting between an upper connector and a lower connector (namely, an upper connector and a lower connector, not shown in the figure), wherein the reverser comprises an upper pressing block 1 and a lower pressing block 2, a distance for installing a sample 3 is kept between the upper pressing block and the lower pressing block along the stretching direction of the creep test machine, the distance can be adjusted under the driving of the creep test machine, the distance can be reduced for providing creep compression loading operation for the sample, and the distance can be increased for unloading the sample 3; in this embodiment, external threads are provided on the outer walls of the upper and lower ends of the sample 3.
The bottom surface of the upper pressing block is provided with a triangular prism-shaped upper positioning hole 11 for the upper end of a sample to extend in, the top surface of the lower pressing block is provided with a triangular prism-shaped lower positioning hole 21 for the lower end of the sample to extend in, the upper positioning hole and the lower positioning hole are aligned along the axial direction of a tensile rod of the creep testing machine, the positions, the outlines and the sizes of the upper positioning hole and the lower positioning hole are the same, the inner surfaces of the upper positioning hole and the lower positioning hole are smooth, and the inscribed circle diameter of the upper positioning hole and the lower positioning hole is larger than the diameter of the end part of the sample to be extended in; in this embodiment, the cross sections of the upper positioning hole and the lower positioning hole are all regular triangles.
An upper fastening hole 12 penetrating through the upper positioning hole from the outside is formed in the position, corresponding to the upper positioning hole, of the side wall of the upper pressing block, the axial lead of the upper fastening hole is intersected with one side edge of the upper positioning hole, a first propping component 4 is arranged in the upper fastening hole, the tail end of the first propping component is propped against the outer wall of the upper end of the rod-shaped sample along the axial direction of the upper fastening hole, the upper threaded end of the rod-shaped sample is attached to the other two side walls of the upper positioning hole, tangential position relation is formed, and the intersection line of the two side walls is the side edge intersected with the axial lead of the upper fastening hole;
the position of the side wall of the lower pressing block corresponding to the lower positioning hole is provided with a lower fastening hole 22 which penetrates through the lower positioning hole from the outside, the axial lead of the lower fastening hole is intersected with one side edge of the lower positioning hole, the lower fastening hole is internally provided with a second propping component 5, the tail end of the second propping component is propped against the outer wall of the lower end of the rod-shaped sample along the axial direction of the lower fastening hole, the lower threaded end of the rod-shaped sample is attached to the two side walls of the lower positioning hole and forms a tangential position relation, and the intersection line of the two side walls is the side edge intersected with the axial lead of the lower fastening hole;
in this embodiment, the axial lines of the upper fastening hole and the lower fastening hole are arranged along the horizontal direction and are located in the same plane parallel to the axial direction of the tensile rod of the creep testing machine, so that when the upper end and the lower end of the sample are respectively abutted against the first abutting part and the second abutting part and are respectively tangential to the upper positioning hole and the lower positioning hole, the upper end and the lower end of the sample are also just located in the same plane parallel to the axial direction of the tensile rod of the creep testing machine, thereby realizing centering of the sample and preventing the sample from being bent prematurely in the creep compression test.
In this embodiment, the axial lead of the upper fastening hole perpendicularly intersects with one prismatic surface of the upper positioning hole, the side edge opposite to the prismatic surface also perpendicularly intersects with the axial lead of the upper fastening hole, the axial lead of the lower fastening hole perpendicularly intersects with one prismatic surface of the lower positioning hole, and the side edge opposite to the prismatic surface also perpendicularly intersects with the axial lead of the lower fastening hole.
In this embodiment, the depth of upper locating hole and lower locating hole equals to wait to stretch into the length of sample tip to guarantee the firmness of clamping, can not influence the connection of lug department and extension device about the sample again.
In this embodiment, the commutator further includes an upper guide rod 13, a lower guide rod 23, an upper stretching rod 14 and an upper connecting block 15 located above the upper pressing block, and a lower stretching rod 24 and a lower connecting block 25 located below the lower pressing block, wherein the upper end of the upper stretching rod is used for connecting an upper connector of the creep testing machine, the lower end of the upper stretching rod is fixedly connected with the upper connecting block, the lower end of the lower stretching rod is used for connecting a lower connector of the creep testing machine, the upper end of the lower stretching rod is fixedly connected with the lower connecting block, the upper guide rod sequentially passes through guide holes formed in the upper connecting block, the upper pressing plate and the lower pressing plate from top to bottom, the middle part of the upper guide rod is arranged in the guide hole formed in the upper pressing block in a penetrating manner, the upper end of the upper guide rod is provided with a shaft shoulder, the end of the upper guide rod is fixedly connected with the upper connecting block through a first nut 16, and the lower end of the upper guide rod is connected with a second nut 26 after passing through the guide hole in the lower pressing block. The lower guide rod sequentially passes through the lower connecting block, the lower pressing plate and the guide holes arranged on the upper pressing plate from bottom to top, the middle part of the lower guide rod is arranged in the guide holes arranged on the lower pressing plate in a penetrating mode, the upper end of the lower guide rod passes through the guide holes on the upper pressing plate and then is connected with a third nut 17, the lower end of the lower guide rod is provided with a shaft shoulder, and the lower end of the lower guide rod is fixedly connected with the lower connecting block through a fourth nut 27. The upper pressing block and the lower pressing block can slide relative to the upper guide rod and the lower guide rod, and the interval between the upper pressing block and the lower pressing block for installing the sample 3 can be manually adjusted.
In this embodiment, the first and second tightening members are bolts with hexagonal holes.
When the test sample is clamped, the upper end and the lower end of the test sample are respectively placed in the upper positioning hole and the lower positioning hole of the triangular prism, after the upper end face and the lower end face of the test sample are completely contacted with the inner bottom faces of the upper positioning hole and the lower positioning hole, the inner hexagon bolts used for locking in the upper fastening hole and the lower fastening hole are screwed, the two ends of the test sample are locked in the positioning holes of the triangular prism by using a locking method of pushing-up radial stress, and at the moment, the connection of the test sample and the reverser is completed.
In the test process, the driving system of the creep testing machine transmits force to the upper and lower movable pull rods, so that the upper and lower pull rods respectively move upwards and downwards, the needed compressive stress state of the sample is realized through the commutator, and the commutator converts the tensile stress of the creep testing machine into the compressive stress of the sample.
After the sample is fixed, an upper extension rod group and a lower extension rod group are arranged on the sample, a displacement sensor is connected below the extension rod, deformation data of the sample is measured in real time, a thermocouple is fixed on the surface of the middle part of the sample, and the temperature of the sample is ensured to be basically consistent with the temperature in a creep machine furnace set by a test. Specific test parameters, test steps and data sampling point frequencies of the steps are set on a computer for controlling the creep machine.
After the test is finished, detailed creep data including left deformation, right deformation, average deformation and relative elongation can be obtained from a PC display screen of the creep testing machine. The coincidence ratio of the time-varying curves of the left deformation and the right deformation is an important reference for judging the deformation uniformity of the sample and whether the sample is bent or not, and if the left deformation and the right deformation are basically consistent, the sample deformation is uniform and has no bending basically, and the creep data at the moment has high accuracy and can be used for subsequent scientific analysis.
In order to verify the beneficial effects of the creep compression clamp in the aspect of neutrality and stability of the sample, the invention uses the SanzhishaSUST-D5 creep testing machine produced by SUST-D5 electric equipment limited company is used as testing equipment, the force control error precision of the creep testing machine is +/-3N, and the temperature control precision of the matched auxiliary heating furnace is +/-2 ℃. The creep amount integral measurement system comprises: the upper extension rod group, the lower extension rod group and the displacement sensor outside the furnace. In the creep aging process, the creep quantity of the sample is transmitted to a displacement sensor outside the furnace for reading through the left and right extension rods of the upper extension rod group and the lower extension rod group. Wherein the displacement sensor is a grating linear displacement sensor with the precision of 5 multiplied by 10 -4 mm。
The creep testing machine is used for carrying out uniaxial constant stress compression creep aging comparison test, the test is divided into three groups, the samples used in the three groups of tests are 2219 aluminum alloy creep samples with identical states, and two ends of the samples used in the three groups of tests are provided with external threads, wherein:
the first group uses the existing compression clamp (the selected existing compression clamp has the same structure as that disclosed in China patent 201910244627.4) to carry out three times of compression creep tests on the test sample under the identical test conditions: the test temperature is 165 ℃, the heating rate is 5 ℃/min, the aging time is 9 hours, and the stress is 120MPa;
the second group carries out three identical compression creep tests on the sample by using the creep compression clamp, and the test conditions are identical to those of the first group;
and the third group carries out two identical compression creep tests on the test sample by using the creep compression clamp provided by the invention, and the rest test conditions are identical with those of the second group except that the stress is 180 MPa.
The creep amounts of the first set of three tests were 0.27% for the first time (see the graph of FIG. 4 for details), 0.215% for the second time (see the graph of FIG. 5 for details), 0.259% for the third time, and the differences in the left and right deformation amounts of the first, second and third tests were 0.022mm,0.029mm and 0.018mm (about 21%,32% and 18% for the left and right deformation amounts, respectively, but the differences in the left and right deformation amounts were still large. The creep test is performed by the existing compression clamp, the test repeatability is poor, the test data accuracy is low, great difficulty is caused to analysis of the test data, and a more accurate test result can be determined after repeated tests are performed for many times;
the difference of the left deformation and the right deformation of the second group of three tests is between 0.011 mm and 0.014mm (about 13% -17% of the difference), and the change curve of the strain quantity of the three tests with time can be basically represented by the graph of FIG. 6;
the difference of the left and right deformation amounts of the third group of two tests is between 0.013 and 0.016mm (about 11% -15% of the difference), and the change curves of the strain amounts of the two tests with time can be basically represented by the graph of fig. 7.
From the above data, the creep compression jig of the present invention represented by the second and third sets of tests is significantly reduced as compared with the conventional compression jigs, and the experimental data has high repeatability, and generally more accurate experimental data can be determined by performing the same test twice.
In the three groups of test processes, the inventor finds that the existing compression clamp still slightly shakes after the test sample is mounted because the test sample is in clearance connection with the commutator in the test sample mounting process, the creep amount of the creep aging test is very small, the measurement is very precise, even the slight shake greatly affects the left and right deformation of the test sample during the creep aging, thus a tester is required to ensure the accuracy of data as much as possible by depending on the parallelism between the visual test sample and the compression clamp, but the method has very high operation requirement on the tester and the uncertainty of the test result is large. Therefore, the creep data measured by the existing compression clamp is not high enough in precision, and only a rough data range and a rough test rule can be obtained.
The improved compression clamp assembly does not need test staff to rely on visual inspection in the process of installing the test sample, is simple in installation operation, has high accuracy of test data, can basically accurate to specific numerical values, avoids repeated operation of the test, greatly shortens test time, expands test stress range, and provides reliable guarantee for high-accuracy data analysis and theoretical research by scientific researchers. Meanwhile, the using amount of the sample is greatly reduced, the using amount and the processing cost of materials are effectively saved, and the method accords with the concept of energy conservation and environmental protection.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. The creep compression clamp is characterized by comprising a first propping part (4), a second propping part (5) and a reverser which is used for being connected between an upper connector and a lower connector of a creep testing machine, wherein the reverser comprises an upper pressing block (1) and a lower pressing block (2), a distance for installing a sample (3) is kept between the upper pressing block and the lower pressing block along the stretching direction of the creep testing machine, the distance value can be adjusted, the distance is used for providing creep compression loading operation for the sample when the distance is reduced, and the distance is used for unloading the sample when the distance is increased;
the bottom surface of the upper pressing block is provided with a triangular prism-shaped upper positioning hole (11) for the upper end of a sample to extend in, the top surface of the lower pressing block is provided with a triangular prism-shaped lower positioning hole (21) for the lower end of the sample to extend in, the upper positioning hole and the lower positioning hole are aligned along the axial direction of a tensile rod of the creep testing machine, the positions, the contours and the sizes of the upper positioning hole and the lower positioning hole are the same, the inner surfaces of the upper positioning hole and the lower positioning hole are smooth surfaces, and the diameter of an inscribed cylinder of the upper positioning hole and the lower positioning hole is larger than the diameter of the end part of the sample to be extended in, so that the sample can extend in smoothly;
an upper fastening hole (12) penetrating through the upper positioning hole from the outside is formed in the position, corresponding to the upper positioning hole, of the side wall of the upper pressing block, the axial lead of the upper fastening hole is intersected with one side edge of the upper positioning hole, the first propping component (4) is arranged in the upper fastening hole and used for propping against the outer wall of the upper end of the sample along the axial direction of the upper fastening hole, so that the upper end of the sample is attached to the other two side walls of the upper positioning hole, tangential positional relation is formed, and the other two side walls are locked, and the intersection line of the two side walls is the side edge of the upper positioning hole intersected with the axial lead of the upper fastening hole;
the lower fastening hole (22) penetrating through the lower positioning hole from the outside is formed in the position, corresponding to the lower positioning hole, of the side wall of the lower pressing block, the axial lead of the lower fastening hole is intersected with one side edge of the lower positioning hole, the second propping component (5) is arranged in the lower fastening hole and used for propping against the outer wall of the lower end of the sample along the axial direction of the lower fastening hole, so that the lower end of the sample is attached to the two side walls of the lower positioning hole, tangential position relation is formed, and the two side walls are locked, and the intersection line of the two side walls is the side edge, intersecting with the axial lead of the lower positioning hole and the lower fastening hole;
the axial lines of the upper fastening hole and the lower fastening hole are positioned in the same plane parallel to the axial direction of the tensile rod of the creep testing machine, so that when the upper end and the lower end of the sample are respectively abutted against the tail ends of the first jacking part and the second jacking part and are respectively tangent to the upper positioning hole and the lower positioning hole, the upper end and the lower end of the sample are also just positioned in the same plane parallel to the axial direction of the tensile rod of the creep testing machine, thereby realizing the centering of the sample and preventing the sample from being bent prematurely in the creep compression test.
2. The creep compression jig of claim 1, wherein the axis of the upper fastening hole perpendicularly intersects one side edge of the upper positioning hole, and the axis of the lower fastening hole perpendicularly intersects one side edge of the lower positioning hole.
3. The creep compression jig according to claim 1, wherein the upper and lower fastening holes are threaded holes with internal threads, and the first and second tightening members are bolts or screws with external threads, and the first and second tightening members are screwed in the upper and lower fastening holes toward the sample, respectively, to fasten the sample.
4. The creep compression clamp according to claim 1, wherein the depths of the upper and lower positioning holes are less than or equal to the length of the end portion to be inserted into the test sample, and the depths of the upper and lower positioning holes are greater than or equal to 1/2 of the length of the end portion to be inserted into the test sample, so as to ensure the clamping firmness without affecting the connection between the upper and lower lugs of the test sample and the extension device.
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| CN201910913177.3A CN110501217B (en) | 2019-09-25 | 2019-09-25 | Creep compression clamp |
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| CN201910913177.3A CN110501217B (en) | 2019-09-25 | 2019-09-25 | Creep compression clamp |
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