CN109883859A - Subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue - Google Patents
Subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue Download PDFInfo
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Abstract
The present invention provides subregion strain testing methods in a kind of heterogene structure's welding point During Low Cycle Fatigue, include the following steps: to carry out low cycle fatigue property test to sample under the conditions of setting strain value, post-rift sample is subjected to corrosion observation, judge fracture position, and analyzes the strain fatigue life and material properties for obtaining sample；Home position is marked using microhardness point on identical alternative sample；Sample after label is subjected to static stretch test；Sample after static stretch is tested carries out surface corrosion, finds out subregion corresponding to hardness mark point, and analysis obtains plastic strain amount caused by tissue subregion；It respectively organizes plastic strain obtained in subregion low-cycle fatigue test and overall strain to be modified to sample, obtains each tissue subregion actual strain；Subregion actual strain and fracture position are respectively organized according to sample, find out the actual strain at fracture position and service life；Differently strained value is set, is repeated the above steps, actual strain-Life Relation is obtained.
Description
Technical field
The present invention relates to welding point heterogene structure low-cycle fatigue testing fields, more particularly to a kind of heterogene structure
Subregion strain testing method in welding point During Low Cycle Fatigue.
Background technique
Existing " the metal material axial direction constant amplitude low-cycle fatigue test side low-cycle fatigue testing standard GB-T 15248-2008
Method " in, only the low cycle fatigue property test method of homogeneous material is proposed and is distinctly claimed.And for the low week of welding point
Fatigue property test is generally executed also referring to the mark.Welding point, especially thick plate welded joint, entire test scope by base material,
Complex organization is constituted in heat affected area and weld seam, and tissue difference causes hardness and strength in each subregion different.Welding point is low
All fatigue property tests are completed by controlled strain amount, this dependent variable, which is that extensometer range section is all, histogenetic always answers
The average value of variable.However welding point is caused entire due to the inhomogeneities of its each partitioned organization and the inconsistency of size
The certain subregion actual strains of connector are higher than load strain and are broken, this brings larger tired for rationally measurement joint fatigue performance
It is difficult.
It is tested for slab narrow gap welding connector low cycle fatigue property, structural heterogenity is mainly manifested in heat affected area
Coarse grain zone, fine grained region and two-phase section size are uneven, and weld seam cylindrical crystalline substance size and the direction of growth are uneven, and low-cycle fatigue is surveyed
The clamping extensometer range used when amount equally includes the above Nonuniform Domain Simulation of Reservoir.Therefore, in the tired longevity for measuring certain strain value
When life, there is " Large strain " and " low strain dynamic " fatigue phenomenon in partitioned organization, so that actual strain is higher than setting strain and overloads,
To which fracture failure occur.If proper method can be used, each practical generation of subregion in low-cycle fatigue test process is found out
Strain, in conjunction with the fracture position occurred, and then obtains the actual strain at fracture position and service life, to obtain actual answer
Become Life Relation.
Application No. is 201810239147.4 patent applications to disclose a kind of prediction technique of vermicular cast iron fatigue strength,
Belong to material and component fatigue technical field of performance test.The present invention is tested by microstructure and high cycle fatigue, analyzes compacted ink
The high cycle fatigue damage mechanisms of cast iron, establish the quantitative relationship of vermicular cast iron microstructure and fatigue strength.The present invention can not only
The fatigue strength of vermicular cast iron is effectively predicted, is likely to be suited for gray cast iron and metal-base composites, meanwhile, it can be substantially reduced
Experimental amount needed for plain fatigue strength detection, test process it is simpler, quick, hence it is evident that saved the time, reduce manpower and
Material resources cost, the method according to material structure subregion carry out repeated strain amendment, obtained data accuracy need into
One step improves.
One is proposed when this project is assessed for welding point heterogene structure low cycle fatigue property in view of the above analysis
Subregion strain testing method in kind heterogene structure's welding point During Low Cycle Fatigue, this method can find out heterogene structure and exist
Respectively the strain actually generated is knitted in grouping when practical low-cycle fatigue is tested, in conjunction with fatigue life, to accurately assess welding point
Strain-Life Relation, and then Accurate Prediction is carried out to the differently strained amplitude lower service life.
Summary of the invention
For the defects in the prior art, the object of the present invention is to provide a kind of heterogene structure's welding point low-cycle fatigue
Subregion strain testing method in the process.
Subregion strain testing method in a kind of heterogene structure's welding point During Low Cycle Fatigue provided according to the present invention,
Include the following steps:
Step 1: according to welding point size and low cycle fatigue test standard, processing low-cycle fatigue sample；Choose extensometer
Gauge length carries out initial low cycle fatigue property test to low-cycle fatigue sample under the conditions of setting strain value, by post-rift low week
Fatigue testing specimen carries out corrosion observation, in conjunction with the metallographic structure of welding point, judges fracture position, and analyze and show that low-cycle fatigue tries
Elastic strain, plastic strain, overall strain, fatigue life and the material properties of sample；
Step 2: according to low-cycle fatigue sample tissue partitioned organization, using micro- hard on identical alternative low-cycle fatigue sample
Degree point label home position, and ensure that all hardness points on same straight line, measure and record two neighboring under the microscope
The distance between hardness mark point；
Step 3: the low-cycle fatigue sample after label is subjected to extension test, extensometer mark used on static stretch machine
Consistent away from clip position and initial low-cycle fatigue test, elongation strain amount reaches load dependent variable when initial low-cycle fatigue test
It unloads at once afterwards；Alternatively, the low-cycle fatigue sample after label is carried out low-cycle fatigue test, testing time on low-cycle fatigue machine
For the half-life cycle-index of corresponding setting strain value；
Step 4: the label low-cycle fatigue sample after unloading being subjected to surface corrosion, finds out and divides corresponding to hardness mark point
Area, measures the distance between every two hardness mark point again under the microscope, and analysis obtains plasticity caused by tissue subregion
Dependent variable；
Step 5: static drawing after obtained elastic strain, and label hardness point is tested according to initial low cycle fatigue test
The resulting plastic strain of analysis of experiments is stretched, modeling obtained in the initial low-cycle fatigue test of subregion is respectively organized to low-cycle fatigue sample
Property strain and overall strain be modified, obtain low-cycle fatigue sample and respectively organize subregion actual strain；
Step 6: respectively organizing the fracture position of subregion actual strain and low-cycle fatigue sample according to low-cycle fatigue sample, ask
Actual strain at fracture position and service life out；
Step 7: differently strained value is set, step 1 is repeated to step 6, obtains actual strain and service life under differently strained value,
To obtain actual strain-Life Relation, realize that strain-life equation to heterogene structure's low-cycle fatigue is predicted.
It preferably, include weld seam, heat affected area, base material in the extensometer gage length length range in step 1.
Preferably, in step 1, maximum load increases variation relation, judgement with fatigue life when analysis low-cycle fatigue is tested
The material properties of low-cycle fatigue sample judge whether the material of low-cycle fatigue sample is processing hardening or work softening material,
If processing hardening or work softening material, half-life cycle-index is recorded；If not processing hardening or softener material, then do not have to
Record half-life cycle-index.
Preferably, it in step 2, is determined according to the tissue subregion of low-cycle fatigue sample and beats the load of hardness mark point, each point
District's groups are knitted including at least 3 hardness points, and the distance between adjacent hardness point is equal, and the distance between adjacent hardness point is at least
20um is verified under the microscope and is recorded distance between each adjacent two hardness mark point.
Preferably, in step 2, the hardness mark point is square, the diagonal distance of the square 20um with
It is interior.
Preferably, before carrying out step 2, when identical alternative low-cycle fatigue sample is first carried out one section of low-cycle fatigue test
Between after, then carry out hardness label.
Preferably, in step 3, by low-cycle fatigue sample when being stretched on static stretch machine, if the material of low-cycle fatigue sample
Material is processing hardening or softener material, then low-cycle fatigue test is carried out on low-cycle fatigue machine, and testing time is that corresponding setting is answered
The half-life cycle-index of variate；If the material of low-cycle fatigue sample is not processing hardening or softener material, in static stretch
Uniaxial direct tensile on machine unloads at once when the setting dependent variable being stretched to when corresponding to initial low-cycle fatigue test.
Preferably, in step 3, judgement of speed change when test rate and initial low-cycle fatigue are tested when the static stretch machine stretches
Rate is identical.
Preferably, in step 4, the label low-cycle fatigue sample after unloading is subjected to surface corrosion, the surface corrosion is
Shallow corrosion, that is, erode to and organize subregion where capable of telling indentation hardness point and hardness point.
Preferably, the low-cycle fatigue specimen surface machining accuracy and roughness meet Industry code requirements, each low week
The material of fatigue testing specimen, physics, chemical property are all the same.
Compared with prior art, the present invention have it is following the utility model has the advantages that
1, when the present invention is for heterogene structure's welding point low-cycle fatigue test, each subregion is marked by indentation hardness method
Home position and size again demarcate district location and size after strain loading, pass through and become before and after comparison partitions sizes
Change, and then obtain subregion actual strain in strain fatigue, avoids and actually occur strain in test and name load strain is not inconsistent
And the fracture failure occurred；The present invention is suitable for each subregion actual strain inspection when any heterogene structure's low cycle fatigue property is tested
It surveys.
2, the present invention finds out maximum strain region, and combine by the measurement to each subregion actual strain of heterogene structure
Fracture position when practical low-cycle fatigue, to strain service life revised, so that Welded Joints low-cycle fatigue life carries out effectively
Assessment.
Detailed description of the invention
Upon reading the detailed description of non-limiting embodiments with reference to the following drawings, other feature of the invention,
Objects and advantages will become more apparent upon:
Fig. 1 used low-cycle fatigue sample with hardness mark point when being static tensile test of the present invention.
Fig. 2 is the microscope view after the present invention divides hardness that sample is marked to stretch.
Specific embodiment
The present invention is described in detail combined with specific embodiments below.Following embodiment will be helpful to the technology of this field
Personnel further understand the present invention, but the invention is not limited in any way.It should be pointed out that the ordinary skill of this field
For personnel, without departing from the inventive concept of the premise, several changes and improvements can also be made.These belong to the present invention
Protection scope.
The invention belongs to welding point heterogene structure low-cycle fatigue testing fields, relate generally to multi-Layer Welding of Thick Plates institute
Cause the non-uniform low cycle fatigue property test of welding joint structure, and in particular to a kind of heterogene structure's welding point low-cycle fatigue
Each partitioned organization actual strain measurement during performance test, to complete heterogene structure's low cycle fatigue property accurate evaluation
Method.In thick plate welded joint low-cycle fatigue test process, since connector includes weld seam, heat affected area and base material, tissue and property
Can be uneven, cause each partitioned organization strain in During Low Cycle Fatigue different, so as to cause strain and name is actually occurred in test
Justice load strain is not inconsistent, and strain overload occurs and fatigue fracture occurs.In consideration of it, the present invention provides a kind of welding point low week is tired
Labor process subregion actual strain test method marks home position to low-cycle fatigue specimen surface microhardness point, passes through static state
It is stretched to low-cycle fatigue actual strain value, is then unloaded.By each subregion distance between measurement markers point, to measure strain
The practical plastic strain amount of subregion in fatigue process, in conjunction with dependent variable elastic in low-cycle fatigue test process, thus Welded Joints
Low-cycle fatigue life is effectively assessed.Technical principle of the invention is that subregion original size, strain are demarcated using indentation hardness
Partitions sizes variation is compared after load, to obtain each subregion actual strain value.
Subregion strain testing method in a kind of heterogene structure's welding point During Low Cycle Fatigue provided according to the present invention,
Include the following steps:
Step 1: according to welding point size and low cycle fatigue test standard, processing low-cycle fatigue sample；Choose extensometer
Gauge length carries out initial low cycle fatigue property test to low-cycle fatigue sample under the conditions of setting strain value, by post-rift low week
Fatigue testing specimen carries out corrosion observation, in conjunction with the metallographic structure of welding point, judges fracture position, and analyze and show that low-cycle fatigue tries
Elastic strain, plastic strain, overall strain, fatigue life and the material properties of sample；
Step 2: according to low-cycle fatigue sample tissue partitioned organization, using micro- hard on identical alternative low-cycle fatigue sample
Degree point label home position, and ensure that all hardness points on same straight line, measure and record two neighboring under the microscope
The distance between hardness mark point；
Step 3: the low-cycle fatigue sample after label is subjected to extension test, extensometer mark used on static stretch machine
Consistent away from clip position and initial low-cycle fatigue test, elongation strain amount reaches load dependent variable when initial low-cycle fatigue test
It unloads at once afterwards；Alternatively, the low-cycle fatigue sample after label is carried out low-cycle fatigue test, testing time on low-cycle fatigue machine
For the half-life cycle-index of corresponding setting strain value；
Step 4: the label low-cycle fatigue sample after unloading being subjected to surface corrosion, finds out and divides corresponding to hardness mark point
Area, measures the distance between every two hardness mark point again under the microscope, and analysis obtains plasticity caused by tissue subregion
Dependent variable；
Step 5: static drawing after obtained elastic strain, and label hardness point is tested according to initial low cycle fatigue test
The resulting plastic strain of analysis of experiments is stretched, modeling obtained in the initial low-cycle fatigue test of subregion is respectively organized to low-cycle fatigue sample
Property strain and overall strain be modified, obtain low-cycle fatigue sample and respectively organize subregion actual strain；
Step 6: respectively organizing the fracture position of subregion actual strain and low-cycle fatigue sample according to low-cycle fatigue sample, ask
Actual strain at fracture position and service life out；
Step 7: differently strained value is set, step 1 is repeated to step 6, obtains actual strain and service life under differently strained value,
To obtain actual strain-Life Relation, realize that strain-life equation to heterogene structure's low-cycle fatigue is predicted.
It include weld seam, heat affected area, base material in the extensometer gage length length range in step 1.In step 1, analyze low
Maximum load increases variation relation with fatigue life when all testing fatigues, judges the material properties of low-cycle fatigue sample, that is, judges
Whether the material of low-cycle fatigue sample is processing hardening or work softening material, if processing hardening or work softening material, note
Record half-life cycle-index；If not processing hardening or softener material, then do not have to record half-life cycle-index.
In step 2, the load for beating hardness mark point is determined according to the tissue subregion of low-cycle fatigue sample, each partitioned organization is extremely
It include less 3 hardness points, the distance between adjacent hardness point is equal, and the distance between adjacent hardness point is at least 20um,
It is verified under microscope and records distance between each adjacent two hardness mark point.In step 2, the hardness mark point is pros
Shape, the diagonal distance of the square is within 20um, so that it is determined that the load value of hardness point.It, will before carrying out step 2
After identical alternative low-cycle fatigue sample first carries out low-cycle fatigue test a period of time, then carry out hardness label and static stretch examination
It tests, to prevent fatigue loading from processing hardening or softening being caused to have an impact subregion strain.Preferably, hardometer is using automatic hard
Degree meter.
In step 3, by low-cycle fatigue sample when being stretched on static stretch machine, if the material of low-cycle fatigue sample is processing
Hardening or softener material, then carry out low-cycle fatigue test on low-cycle fatigue machine, and testing time is the half of corresponding setting strain value
Life Cycle number；If the material of low-cycle fatigue sample is not processing hardening or softener material, on static stretch machine directly
Stretch, when setting dependent variable when being stretched to corresponding initial low-cycle fatigue test unloads at once, i.e., ought be stretched to strain value with
When the initial low-cycle fatigue strain value of correspondence is equal, it is zero by load unloading, strain cannot be reverted to zero, remove sample.Step 3
In, strain rate is identical when test rate is tested with initial low-cycle fatigue when the static stretch machine stretches.
In step 4, the label low-cycle fatigue sample after unloading is subjected to surface corrosion, the surface corrosion is shallow corrosion,
It erodes to and organizes subregion where capable of telling indentation hardness point and hardness point.
The low-cycle fatigue specimen surface machining accuracy and roughness meet Industry code requirements, each low-cycle fatigue sample
Material, physics, chemical property it is all the same.
Preferably, include the following steps:
The first step, for welding point using Weld pipe mill as line of symmetry processing criterion low-cycle fatigue sample, selection is properly drawn
The dependent variable corresponding longevity can be obtained comprising weld seam, heat affected area and base material under the conditions of differently strained value by stretching meter gauge length
Life completes low-cycle fatigue test.
Second step analyzes low-cycle fatigue fracture position；Post-rift low-cycle fatigue sample is subjected to corrosion observation, in conjunction with weldering
The metallographic structure of connector is accurately judged to its fracture position.
Third step, maximum load increases variation relation with fatigue life when analysis low-cycle fatigue is tested, and whether judgement material
It is processing hardening or work softening material, if it is processing hardening or work softening material, records its half-life cycle-index；Such as
The non-processing hardening of fruit or softener material do not have to record then.
The low-cycle fatigue specimen surface that do not test is carried out indentation hardness label by the 4th step.Choose lesser hardness
Load, it is ensured that the Diagonal Dimension of impression point is centainly less than the 1/3 of each subregion minimum dimension of heterogene structure, i.e. smallest partition ruler
It is very little to include at least 3 hardness points.The distance between load value and the hardness point for determining indentation hardness, on atutomatic hardness tester
Impression label is carried out to low-cycle fatigue sample, and ensures to be equidistant between all hardness points and on same straight line.
5th step, using metallographic microscope, the distance between indentation hardness marked to step 3 measures again
Record, accurately determines the initial distance between each subregion indentation hardness point.
6th step will mark the sample with indentation hardness, stretch on static tensile test machine.If material is to add
Work hardening or softener material then need to carry out fatigue on low-cycle fatigue machine, and the tired time is the half-life of corresponding dependent variable.Such as
Processing hardening or ruckbildung is not present in fruit material, then the uniaxial direct tensile on static stretch machine, and when being stretched to, corresponding measurement is tired
When dependent variable when, unload at once.
7th step is directly shallowly corroded the tensile sample after unloading with corrosive agent, can differentiate place's indentation hardness point
And the tissue at corresponding place.
Tensile sample after shallow corrosion is carried out calibration measurement to hardness point distance under the microscope again by the 8th step, is remembered
Distance between hardness point, the plastic strain amount occurred so as to find out each subregion after record stretches.
9th step, in conjunction with the plastic strain magnitude that the calculated elastic properties of materials dependent variable of the first step and the 8th step are obtained,
The overall strain value in the practical During Low Cycle Fatigue in each region is obtained, in conjunction with the fracture position of low-cycle fatigue sample, and then is found out
The practical dependent variable occurred at fracture position, and then strain is modified.
Tenth step regains strain according to the practical plastic strain and overall strain at the 9th resulting fracture position of step
Life Relation；Above step is repeated, each subregion plastic strain under differently strained fatigue is modified respectively respectively, thus real
Now to the strain of heterogene structure's low-cycle fatigue-life equation Accurate Prediction.
Embodiment 1:
Using 120mm thickness CrMoV steel as research material, using multilayer multiple tracks submerged arc soldering method, welding is completed, weld width is about
20mm。
The first step, centered on weld seam, 21, processing criterion low-cycle fatigue sample, parallel-segment gauge length 30mm, using low week
Fatigue extender 25mm.
Second step chooses 16 samples, respectively with strain amplitude for 0.3%, 0.4%, 0.5%, 0.6%, 0.7%,
0.8%, 0.9% carries out low-cycle fatigue respectively, and each strain amplitude is repeated 2 times, and needs 14, sample altogether.
Third step judges that low-cycle fatigue sample fracture position is in Weld pipe mill position, and remaining 7 samples divide
Hardness point label is carried out not on automatic hardness tester, it is 300g, load time 10s, every two hardness point that hardness point, which applies load,
Distance is 100um, and total hardness point length is 25mm, is equal to extensometer gage length distance.
Sample with hardness mark point is re-measured hardness spot size under the microscope, and kept a record by the 4th step.
5th step will have 7 samples of hardness mark point, carry out low cycle fatigue test, fatigue loading strain amplitude again
Respectively 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, when load number respectively corresponds the disconnected of strain amplitude
It can stop testing when splitting the half in service life, be zero by load unloading, make sure to keep in mind that strain zero can not be reverted to.
6th step, by the low-cycle fatigue sample of unloading, surface is shallowly corroded, it may be observed that clear tissue.Then
Again it observes under the microscope, records hardness point distance change, so that the plastic strain to each region carries out calibration measurement, such as
Shown in Fig. 2.
7th step after calibrating plastic strain, in conjunction with the elastic strain of low-cycle fatigue sample, regains the bullet modeling of sample
Property strain, the service life of low-cycle fatigue sample is predicted again.
Compliance test result is as shown in the table:
As can be seen from the table, the practical distortion amount of sample and the dependent variable of load are different, practical distortion amount bases
This is greater than the dependent variable of load, and sample low-cycle fatigue life and true lifetime error through present invention amendment prediction are smaller, accurately
Degree is higher than traditional life-span prediction method.
Specific embodiments of the present invention are described above.It is to be appreciated that the invention is not limited to above-mentioned
Particular implementation, those skilled in the art can make a variety of changes or modify within the scope of the claims, this not shadow
Ring substantive content of the invention.In the absence of conflict, the feature in embodiments herein and embodiment can any phase
Mutually combination.
Claims (10)
1. subregion strain testing method in a kind of heterogene structure's welding point During Low Cycle Fatigue, which is characterized in that including such as
Lower step:
Step 1: according to welding point size and low cycle fatigue test standard, processing low-cycle fatigue sample；Extensometer gage length is chosen,
Initial low cycle fatigue property test is carried out to low-cycle fatigue sample under the conditions of setting strain value, post-rift low-cycle fatigue is tried
Sample carries out corrosion observation, in conjunction with the metallographic structure of welding point, judges fracture position, and analyze the bullet for obtaining low-cycle fatigue sample
Property strain, plastic strain, overall strain, fatigue life and material properties；
Step 2: according to low-cycle fatigue sample tissue partitioned organization, microhardness point is used on identical alternative low-cycle fatigue sample
Home position is marked, and ensures that all hardness points on same straight line, measure and record two neighboring hardness under the microscope
The distance between mark point；
Step 3: the low-cycle fatigue sample after label is subjected to extension test, extensometer gage length folder used on static stretch machine
It holds position and initial low-cycle fatigue test is consistent, after load dependent variable when elongation strain amount reaches initial low-cycle fatigue test i.e.
Carve unloading；Alternatively, the low-cycle fatigue sample after label is carried out low-cycle fatigue test on low-cycle fatigue machine, testing time is pair
The half-life cycle-index of strain value should be set；
Step 4: the label low-cycle fatigue sample after unloading is subjected to surface corrosion, finds out subregion corresponding to hardness mark point,
Measure the distance between every two hardness mark point again under the microscope, analysis obtains plastic strain caused by tissue subregion
Amount；
Step 5: static stretch tries after testing obtained elastic strain, and label hardness point according to initial low cycle fatigue test
The resulting plastic strain of analysis is tested, respectively organizes plasticity obtained in the initial low-cycle fatigue test of subregion to answer on low-cycle fatigue sample
Become and overall strain is modified, obtains low-cycle fatigue sample and respectively organize subregion actual strain；
Step 6: respectively organizing the fracture position of subregion actual strain and low-cycle fatigue sample according to low-cycle fatigue sample, find out disconnected
Split the actual strain at position and service life；
Step 7: differently strained value is set, step 1 is repeated to step 6, obtains actual strain and service life under differently strained value, thus
Actual strain-Life Relation is obtained, realizes that strain-life equation to heterogene structure's low-cycle fatigue is predicted.
2. subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue according to claim 1,
It is characterized in that, includes weld seam, heat affected area, base material in the extensometer gage length length range in step 1.
3. subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue according to claim 1,
It is characterized in that, in step 1, maximum load increases variation relation with fatigue life when analysis low-cycle fatigue is tested, and judges that low week is tired
The material properties of labor sample judge whether the material of low-cycle fatigue sample is processing hardening or work softening material, if plus
Work hardening or work softening material, record half-life cycle-index；If not processing hardening or softener material, then do not have to record half
Life Cycle number.
4. subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue according to claim 1,
It is characterized in that, in step 2, the load for beating hardness mark point, each partitioned organization is determined according to the tissue subregion of low-cycle fatigue sample
Including at least 3 hardness points, the distance between adjacent hardness point is equal, and the distance between adjacent hardness point is at least 20um,
It verifies under the microscope and records distance between each adjacent two hardness mark point.
5. subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue according to claim 1,
It is characterized in that, in step 2, the hardness mark point is square, and the diagonal distance of the square is within 20um.
6. subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue according to claim 1,
It is characterized in that, before carrying out step 2, after identical alternative low-cycle fatigue sample is first carried out low-cycle fatigue test a period of time,
Hardness label is carried out again.
7. subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue according to claim 3,
It is characterized in that, in step 3, by low-cycle fatigue sample when being stretched on static stretch machine, if the material of low-cycle fatigue sample is to add
Work hardening or softener material, then carry out low-cycle fatigue test on low-cycle fatigue machine, and testing time is corresponding setting strain value
Half-life cycle-index；It is straight on static stretch machine if the material of low-cycle fatigue sample is not processing hardening or softener material
Stretching is connect, is unloaded at once when the setting dependent variable being stretched to when corresponding to initial low-cycle fatigue test.
8. subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue according to claim 1,
It is characterized in that, in step 3, strain rate phase when test rate is tested with initial low-cycle fatigue when the static stretch machine stretches
Together.
9. subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue according to claim 1,
It being characterized in that, in step 4, the label low-cycle fatigue sample after unloading is carried out surface corrosion, and the surface corrosion is shallow corrosion,
It erodes to and organizes subregion where capable of telling indentation hardness point and hardness point.
10. subregion strain testing method in heterogene structure's welding point During Low Cycle Fatigue according to claim 1,
It is characterized in that, the low-cycle fatigue specimen surface machining accuracy and roughness meet Industry code requirements, each low-cycle fatigue examination
The material of sample, physics, chemical property are all the same.
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| CN113218796B (en) * | 2021-04-16 | 2022-06-10 | 上海交通大学 | Method for detecting relation between strain and hardness of material |
| CN113203638A (en) * | 2021-04-20 | 2021-08-03 | 上海交通大学 | Method and system for testing shearing large strain of metal sheet under microscopic scale |
| CN113624671A (en) * | 2021-07-30 | 2021-11-09 | 中车工业研究院有限公司 | Welding joint corrosion tensile test method and test device |
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