CN113155560A - Metal workpiece crack opening method without fracture damage - Google Patents
Metal workpiece crack opening method without fracture damage Download PDFInfo
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- CN113155560A CN113155560A CN202110298098.3A CN202110298098A CN113155560A CN 113155560 A CN113155560 A CN 113155560A CN 202110298098 A CN202110298098 A CN 202110298098A CN 113155560 A CN113155560 A CN 113155560A
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- crack
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- 238000000034 method Methods 0.000 title claims abstract description 27
- 239000002184 metal Substances 0.000 title claims abstract description 20
- 238000012360 testing method Methods 0.000 claims abstract description 25
- 238000013001 point bending Methods 0.000 claims abstract description 7
- 230000006835 compression Effects 0.000 claims abstract description 5
- 238000007906 compression Methods 0.000 claims abstract description 5
- 238000005520 cutting process Methods 0.000 claims abstract description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 230000001788 irregular Effects 0.000 claims description 3
- 239000000463 material Substances 0.000 abstract description 3
- 238000005336 cracking Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 241000169624 Casearia sylvestris Species 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010892 electric spark Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
- G01N2001/2873—Cutting or cleaving
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- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
The invention discloses a metal workpiece crack opening method without damaging a fracture, which belongs to the technical field of material failure analysis and comprises the following steps: 1) cutting the workpiece containing the cracks into blocks containing the cracks, wherein a set distance is kept between the end face of each block and the tip of each crack; 2) a clamp capable of enabling three points of a block body containing cracks to be stressed is arranged on a testing machine with a compression function; 3) placing the block containing the cracks between an upper clamp and a lower clamp of a testing machine; 4) moving the upper clamp of the testing machine downwards to be in three-point contact with the block body containing the cracks; 5) and (4) slowly moving the clamp on the testing machine downwards, and applying stress to the block body containing the crack to open the crack. The invention adopts the testing machine with the compression function, utilizes the three-point bending principle to open the cracks of the workpiece without damage, ensures that the fracture is not damaged in the opening process, ensures the failure analysis result to be reliable, has low requirements on the size and the shape of the workpiece, can be used for special-shaped and large-sized workpieces, is time-saving and labor-saving compared with manual knocking, is safe to operate, and has no risk of hurting people caused by flying out of the workpiece after the workpiece is fractured.
Description
Technical Field
The invention belongs to the technical field of material failure analysis, and particularly relates to a metal workpiece crack opening method without damaging a fracture.
Background
Cracking/breaking of a metal workpiece is the most common form of failure of a part, often occurs in industrial production and often causes serious consequences, in order to thoroughly solve problems and prevent similar accidents from happening again, the cracking reason of the workpiece generally needs to be analyzed, the cracking property can be analyzed by observing the microscopic appearance of the fracture surface, the important step for determining the failure reason of the workpiece is provided, whether the material has macroscopic and microscopic defects or not can be determined according to the appearance of the fracture, the crack source area, the trend, the fracture property and the like can be determined, and the function in failure analysis cannot be replaced.
However, regular inspection of critical components often enables timely detection before the component has not broken or even before the crack has penetrated, greatly reducing the losses that can occur, in which case it is important to open the crack without damaging the fracture surface.
CN108857302A proposes a relatively common method for opening cracks on a metal workpiece, in which a metal workpiece is cut and then fixed on a bench vice, and the cracks are opened by manual striking and limited by the clamping manner of the bench vice, which can only be used for workpieces with regular appearance and straight crack trend; the total size of the workpiece and the size of the area of the workpiece that has not yet cracked cannot be too large, limited by manual forces. In addition, this method also has the risk of flying out and being easily injured when the workpiece is broken.
CN109759810A discloses a metal workpiece crack opening device and method, pin shafts are arranged at two ends of a workpiece crack, the crack is opened by utilizing the acting force of a wedge-shaped component on the pin shafts, the method is used for punching holes on the workpiece and installing the pin shafts, a plurality of pairs of pin shafts are often required to be installed, the operation is complex, the workpiece is damaged, and meanwhile, the holes are punched under the condition that the trend of the crack in the workpiece is unclear, and the fracture can be damaged.
Disclosure of Invention
The object of the present invention is to provide a method for crack opening of a metal workpiece without damage to the fracture, in view of the above-mentioned problems of the prior art.
The invention is realized by the following technical scheme:
a method for opening a crack in a metal workpiece without damaging the fracture comprises the following steps:
1) cutting the workpiece containing the cracks into blocks containing the cracks, wherein a set distance is kept between the end face of each block and the tip of each crack;
2) a clamp capable of enabling three points of a block body containing cracks to be stressed is arranged on a testing machine with a compression function;
3) placing the block containing the cracks between an upper clamp and a lower clamp of a testing machine;
4) moving the upper clamp of the testing machine downwards to be in three-point contact with the block body containing the cracks;
5) and (4) slowly moving the clamp on the testing machine downwards, and applying stress to the block body containing the crack to open the crack.
The invention is further improved in that the method also comprises the following steps:
6) the cracks were removed after opening for observation and analysis.
The further improvement of the invention is that the step 5 applies stress to the crack-containing block body to make the crack open, and alternately increasing the stress and reducing the stress.
The invention is further improved in that a three-point bending fixture is adopted for the crack-containing blocks with regular shapes.
The invention is further improved in that a flattening clamp or a three-point bending clamp is adopted for the irregular crack-containing blocks.
The invention has the further improvement that in the process of applying stress, the longest surface of the crack is positioned between two stress points, the trend of the crack is vertical to the connecting line of the two stress points, and the surface near the root of the crack is a third stress point.
The invention is further improved in that the minimum distance from the crack tip to the surface of the block is in the range of 0.5-20 mm.
The invention is further improved in that the crack-containing block is soaked in liquid nitrogen for cooling before being placed between the upper clamp and the lower clamp of the testing machine, so as to reduce the stress required by crack opening and possible plastic deformation.
The invention has at least the following beneficial technical effects:
compared with the prior art, the metal workpiece crack opening method without damaging the fracture has the following advantages that a testing machine with a compression function is utilized:
1. the fracture is not damaged, and the failure analysis result is ensured to be reliable.
2. Compared with manual knocking, the utility model saves time and labor.
3. The requirements on the size and the shape of the workpiece are low, and the method is suitable for special-shaped and large-size workpieces.
4. The operation is safe, and the risk of hurting people caused by flying out of the broken workpiece is avoided.
Drawings
FIG. 1 shows the crack morphology of example 1 of the present invention.
FIG. 2 is a schematic view of workpiece loading according to embodiment 1 of the present invention.
FIG. 3 is a schematic view of the loading of the regular-shaped workpiece for opening cracks by the three-point bending method in example 2 of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
Example 1
Header pipe seat with sample cracked at certain fillet weld
The appearance of the crack is shown in figure 1, the workpiece is irregular in shape, large in size and uneven in crack trend, and the crack cannot be opened by fixing the workpiece by a conventional bench vice and manually knocking the workpiece. A loading schematic for crack opening using a crush clamp is shown in fig. 2.
Firstly, cutting off redundant metal into V-shaped blocks containing cracks by adopting an electric spark cutting mode.
And secondly, mounting a flattening test fixture on the universal testing machine, and soaking the V-shaped block containing the cracks in liquid nitrogen for low-temperature cooling.
And thirdly, placing the block on a lower clamp of the testing machine, and moving the upper clamp downwards to enable the upper clamp to be in contact with two upper vertex points of the V shape respectively, and enabling the lower vertex point of the V-shaped block to be in contact with the lower clamp.
And fourthly, controlling the upper clamp of the testing machine to move downwards slowly to increase the stress and slightly open the crack.
And fifthly, reducing the stress of the testing machine, so that the two upper vertexes of the V-shaped block can slightly move according to the opening condition.
And sixthly, increasing the stress to open the crack at a larger angle.
And seventhly, repeating the fifth step and the sixth step until the fracture is opened, and taking down the fracture for observation and analysis.
Example 2
The sample being a regularly shaped workpiece
The shape of the sample is regular, the crack is opened by adopting a three-point bending method, and the loading schematic diagram is shown in figure 3.
In the first step, the excess metal is cut into regular blocks containing cracks.
And secondly, mounting a bending test fixture on the universal testing machine, and soaking the crack-containing regular block in liquid nitrogen for low-temperature cooling.
And thirdly, placing the block on a lower clamp of the testing machine, and enabling the crack to face downwards and be positioned at the center of the two supporting points. The upper jig is moved downward to bring the upper jig into contact with the crack backside surface.
And fourthly, controlling the upper clamp of the testing machine to move downwards slowly to increase stress, so that the crack is opened until the fracture is opened, and taking down the fracture for observation and analysis.
Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (8)
1. A method for opening a crack in a metal workpiece without damaging the fracture is characterized by comprising the following steps:
1) cutting the workpiece containing the cracks into blocks containing the cracks, wherein a set distance is kept between the end face of each block and the tip of each crack;
2) a clamp capable of enabling three points of a block body containing cracks to be stressed is arranged on a testing machine with a compression function;
3) placing the block containing the cracks between an upper clamp and a lower clamp of a testing machine;
4) moving the upper clamp of the testing machine downwards to be in three-point contact with the block body containing the cracks;
5) and (4) slowly moving the clamp on the testing machine downwards, and applying stress to the block body containing the crack to open the crack.
2. The method of claim 1, further comprising the steps of:
6) the cracks were removed after opening for observation and analysis.
3. The method for opening the crack of the metal workpiece without damaging the fracture as claimed in claim 1 or 2, wherein the step 5 applies stress to the crack-containing block so as to alternately increase the stress and decrease the stress during the crack opening process.
4. A method of opening a crack in a metal workpiece without damaging the fracture as claimed in claim 1 or 2, characterized in that for regular shaped crack containing blocks a three point bending fixture is used.
5. A method of opening a crack in a metal workpiece without damaging the fracture as claimed in claim 1 or 2, characterized in that for irregular crack-containing blocks a flattening jig or a three-point bending jig is used.
6. The method for opening the crack of the metal workpiece without damaging the fracture as claimed in claim 1 or 2, wherein the longest surface of the crack is positioned between two stress points in the process of applying the stress, the crack runs perpendicular to the connecting line of the two stress points, and the surface near the root of the crack is the third stress point.
7. The method for opening a crack in a metal workpiece without damaging the fracture as claimed in claim 1 or 2, wherein the minimum distance from the crack tip to the surface of the block is in the range of 0.5 to 20 mm.
8. The method for opening the crack of the metal workpiece without damaging the fracture as claimed in claim 1 or 2, wherein the crack-containing block is soaked in liquid nitrogen for cooling before being placed between an upper clamp and a lower clamp of a testing machine so as to reduce the stress required for opening the crack and the possible plastic deformation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110298098.3A CN113155560A (en) | 2021-03-19 | 2021-03-19 | Metal workpiece crack opening method without fracture damage |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110298098.3A CN113155560A (en) | 2021-03-19 | 2021-03-19 | Metal workpiece crack opening method without fracture damage |
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| Publication Number | Publication Date |
|---|---|
| CN113155560A true CN113155560A (en) | 2021-07-23 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110298098.3A Pending CN113155560A (en) | 2021-03-19 | 2021-03-19 | Metal workpiece crack opening method without fracture damage |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113155560A (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4864867A (en) * | 1988-01-19 | 1989-09-12 | Battelle Development Corporation | Determining fracture mode transition behavior of solid materials using miniature specimens |
| JP2004340591A (en) * | 2003-05-13 | 2004-12-02 | Toshiba Corp | Method of testing stress corrosion cracking |
| CN102564870A (en) * | 2011-12-19 | 2012-07-11 | 中南大学 | Crack-propagation test method and device |
| CN103105406A (en) * | 2011-11-09 | 2013-05-15 | 北京有色金属研究总院 | Method for observing crack propagation path of titanium alloy under plane strain state |
| CN103487339A (en) * | 2013-09-29 | 2014-01-01 | 哈尔滨工程大学 | Device for testing fatigue crack growth rate of metal material in aqueous corrosive medium |
-
2021
- 2021-03-19 CN CN202110298098.3A patent/CN113155560A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4864867A (en) * | 1988-01-19 | 1989-09-12 | Battelle Development Corporation | Determining fracture mode transition behavior of solid materials using miniature specimens |
| JP2004340591A (en) * | 2003-05-13 | 2004-12-02 | Toshiba Corp | Method of testing stress corrosion cracking |
| CN103105406A (en) * | 2011-11-09 | 2013-05-15 | 北京有色金属研究总院 | Method for observing crack propagation path of titanium alloy under plane strain state |
| CN102564870A (en) * | 2011-12-19 | 2012-07-11 | 中南大学 | Crack-propagation test method and device |
| CN103487339A (en) * | 2013-09-29 | 2014-01-01 | 哈尔滨工程大学 | Device for testing fatigue crack growth rate of metal material in aqueous corrosive medium |
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Application publication date: 20210723 |