CN102706743A - Judgment method for critical destruction of fatigue test - Google Patents
Judgment method for critical destruction of fatigue test Download PDFInfo
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- CN102706743A CN102706743A CN2012101766451A CN201210176645A CN102706743A CN 102706743 A CN102706743 A CN 102706743A CN 2012101766451 A CN2012101766451 A CN 2012101766451A CN 201210176645 A CN201210176645 A CN 201210176645A CN 102706743 A CN102706743 A CN 102706743A
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Abstract
The invention discloses a judgment method for critical destruction of fatigue test and is applicable to critical destruction judgment of a test piece to be detected for fatigue destruction test. The method comprises the following steps of: firstly, arranging a strain gauge which is used for the critical destruction judgment of the test piece to be detected on the surface of the test piece to be detected, wherein the strain gauge is a copper wire gauze or a copper foil which is adhered to the surface of the test piece to be detected by an efficient insulating adhesive; and secondly, performing fatigue destruction test on the test piece to be detected, and performing fatigue destruction judgment on the test piece to be detected by destructive judgment of the copper wire gauze or the copper foil. Therefore, compared with the conventional non-destructive inspection method, the method provided by the invention has the advantages that macroscopic control is preferred, detection dispersion is slightly influenced by human subjective factors, and the method is easy and convenient to operate and facilitates improvement of fatigue test efficiency.
Description
Technical field
The present invention relates to the determination methods of the critical destruction of a kind of torture test, belong to the structural test field.
Background technology
During material generation fatigure failure, the load action that it bore is well below the strength of materials.Big quantity research shows, periodically under the load action, the appearance of material internal crackle with carry out, be the key reason that causes its inefficacy.
Therefore, when structural design, except checking computations ultimate limit state and serviceability limit state; Carry out tired checking computations for the member that bears dynamic load or cyclic loading, and the latter's key, be that given circulating cycle is during issue; Structure Design intensity, and these two key parameters all will be confirmed through experimental study; Even if finite element program calculates, its basis is based upon on the basis of experimental equally.
The main research purpose of torture test is to explore material, the performance of structure under the periodicity load action, and it comprises the identification of initial crack, development, fatigure failure criterion and the destruction form thereof of crackle.Different phase adopts the different detection means, help objective, truly, exactly the performance of different structure under Fatigue Load described.
In decades in the past, the test of the single shaft fatigue of material has obtained considerable progress, and achievement is enrolled standard.And along with steel building, bridge large-scale application; New fatigue problem embodies gradually, strides steel case beam in the cable support bridge especially greatly, because it adopts all welded construction; Weld spacing is little; The leg size is big, and directly bears the vehicular load effect, and the fatigue problem of weld seam and near zone material thereof all needs new torture test to solve.
In general Fatigue Test Research, the periodicity of cyclic load is easy to obtain; And along with nondestructive testing technique research progressively deeply, the feasibility of form and position that accurately detects fatigue crack is increasingly high, and is perfect although this type of technology is still waiting at present, and the use of instrument and equipment receives the control of artificial subjective factor more; Judge that whether structure/member can also continue bearing load behind the cyclic loading of experience a period of time, in disclosed document, nearly all hold one's opinion at present yet how to let.Most scholars all with the degree of depth, width or the distributional pattern of crackle, number as discrimination standard, so exist following problem:
1. evaluation criteria is not unique, and to different members, it is also different to pass judgment on principle, is unfavorable for the experimental study of system;
2. even judgment criteria is fixed, the means/method of evaluation receives artificially to influence obviously because of ringing, and causes the discrete type of final sumbission (cycle index) bigger;
3. adopt at present usually the stress of foil gauge/sinusoid strain gauging structure/member, the strain through measuring individual point is to obtain the nominal stress of structure, and its measurement technology itself has bigger error.
In addition, at welded seam area, especially fillet weld is regional, because the existence of unrelieved stress and initial imperfection, when fatigue load was the periodicity moment of flexure, its fatigure failure position was confirmed as yet, adopts traditional decision procedure, causes bigger error equally.
In sum; In torture test; Adopt that a kind of dispersion degree is little, the critical destruction decision method of the torture test of stress determination broad covered area (critical conditions and corresponding fatigue stress thereof), in the torture test of systematic study material, structure/member, have crucial meaning.
Summary of the invention
The present invention is directed to the deficiency of prior art; The determination methods of the critical destruction of a kind of torture test is provided; Compare with traditional nondestructive examination, this method is more paid attention to macroscopic aspect control, and the dispersion that detects influenced by artificial subjective factor less; This method is easy and simple to handle in addition, helps improving the efficient of torture test.
For realizing above technical purpose, the present invention will take following technical scheme:
The determination methods of the critical destruction of a kind of torture test; The test specimen to be checked that carries out fatigue to failure test is done critical destruction to be judged; At first; Be provided for the foil gauge that the critical destruction of test specimen to be checked is judged on the surface of test specimen to be checked, this foil gauge is copper mesh or Copper Foil, and said copper mesh or Copper Foil are pasted the surface that agent sticks on test specimen to be checked through efficient insulation; Then treat and inspect part and carry out fatigue to failure test, judge that through the destructiveness of copper mesh or Copper Foil the fatigure failure of carrying out test specimen to be checked judges.
The method that said copper mesh sticks on test specimen to be checked surface is: because of vertical direction and the parallel direction that fatigue to failure test produces principle stress horizontal copper wire, vertical copper wire are set accordingly at test specimen to be checked respectively; To lay copper mesh on test specimen to be checked surface; And vertically copper wire directly sticks on the surface of test specimen to be checked, and laterally the junction of copper wire, vertical copper wire directly bonds simultaneously; Said each horizontal copper wire spacing is 1/10 ~ 1/15 of a test specimen minor face to be checked, and each vertical copper wire spacing is 1/10 ~ 1/15 of a test specimen minor face to be checked.
The method that Copper Foil sticks on test specimen to be checked surface is: directly Copper Foil is sticked on test specimen to be checked surface; And the length direction of Copper Foil is consistent because of fatigue to failure test produces the principle stress parallel direction with test specimen to be checked, and the lengthwise edge of Copper Foil does not go out the edge on test specimen to be checked surface.
The destructive determination methods of Copper Foil is: the two ends of Copper Foil length direction are connected the expansion slot connection respectively with one; Two connect expansion slot connects with checkout equipment, external power supply through lead, and this checkout equipment can be monitored the electric current or the voltage signal of Copper Foil, connection expansion slot, sealing series loop that checkout equipment, external power supply constituted.
Said checkout equipment is reometer or voltage table.
It is oxirene that agent is pasted in said efficient insulation.
According to above technical scheme, can realize following beneficial effect:
The present invention is that a kind of dispersion degree is little, the critical destruction decision method of the torture test of stress determination broad covered area (critical conditions and corresponding fatigue stress thereof), in the torture test of systematic study material, structure/member, has crucial meaning.Simultaneously, the present invention compares with traditional nondestructive examination, more pays attention to macroscopic aspect control, and the dispersion that detects influenced by artificial subjective factor less, this method is easy and simple to handle in addition, helps improving the efficient of torture test.
Description of drawings
Fig. 1 is the test specimen structural representation to be checked that is bonded with Copper Foil;
Fig. 2 is that the said test specimen to be checked of Fig. 1 did not carry out the structural representation that destructive test detects before Copper Foil ruptured;
Fig. 3 is the circuit theory diagrams corresponding to Fig. 2;
The said test specimen to be checked of Fig. 1 carried out the structural representation that destructive test detects when Fig. 4 was the Copper Foil fracture;
Fig. 5 is the circuit theory diagrams corresponding to Fig. 4;
Wherein: test specimen 1 to be checked; Copper Foil 2; Agent 3 is pasted in efficient insulation; Lead 4; Connect expansion slot 5.
Embodiment
Accompanying drawing discloses the structural representation of preferred embodiment involved in the present invention without limitation; Below will combine accompanying drawing that technical scheme of the present invention at length is described.
Two embodiment involved in the present invention below are detailed respectively.
Embodiment one, vertical, horizontal copper wire scheme
Foil gauge has certain discrete type when measuring structure/component surface stress, and this mainly comes from the limitation of foil gauge self area coverage; And the core parts of foil gauge are the tinsels of one group of annular; If with the copper wire expansion and the vertical, horizontal arranged crosswise of same diameter is netted,, can address the above problem to form " foil gauge " that enlarges version.
Test shows, when brass wire diameter very little (diameter is less than 0.04mm), if the stress of structure/component surface is big or underbead crack when carrying out to the surface, copper wire promptly ruptures.At this moment; Original structure/member is the cyclic loading of number of times necessarily still; But under primary frequency, the peak stress that structure can bear will descend gradually, and be generating material property fracture (load that structure can bear moment glide) at 2% ~ 5% back original structure of primitive period number.In addition, it is worthy of note, when copper wire ruptures, if stop torture test at once, original structure is carried out bearingtest, the maximum stress of structure and is higher than nominal fatigue stress near the design load of the strength of materials during destruction.
Can think that thus when utilizing this method (whether the fracture of vertical, horizontal copper wire judges the critical conditions of torture test), the faulting stress of copper wire is the nominal fatigue stress of test specimen.
It is worthy of note; In the test preparatory stage; The copper wire parallel with principal direction of stress (
type copper wire) should directly stick on the test specimen surface, and the copper wire vertical with principle stress (
type copper wire) then pasted on test specimen or
type copper wire.Extra process is not done in intersection at copper wire, but copper wire must apply a less prestress before stickup, is in complete extended state and contacts with test specimen to guarantee it.In addition, the spacing of copper wire is generally decided according to actual conditions, generally, gets 1/10 ~ 1/15 of test specimen bond length and is advisable.
Vertical, horizontal copper wire scheme is applicable to that mainly sample dimensions is less, and test specimen target location stress state is comparatively single.Because whether the fracture of copper wire need judge (phenomenon itself very significantly) through naked eyes, when not satisfying above-mentioned condition, many fractures simultaneously or copper wire distortion, the precision of influence experiment possibly appear in copper wire.
When less and stress state is comparatively simple when the size of test specimen, adopts in length and breadth and often can obtain comparatively satisfied result to copper wire.Yet when the size of test specimen stress state big or test specimen target detection position was comparatively complicated, the discrete type of vertical, horizontal copper wire scheme increased gradually.For this reason, if when Copper Foil replaced copper wire, can well address this problem.
The same with copper wire; Copper Foil links to each other with the target test specimen through the agent of efficiently pasting of insulation, and structure is as shown in Figure 1, and the length direction of Copper Foil is greater than the width (be in the nature and stretch out the test specimen edge) of test specimen; And be provided with at the Copper Foil two ends and connect expansion slot as electrode; The bottom that connects expansion slot is provided with lead, links to each other with coherent detection equipment, external power supply to form a loop, structure such as Fig. 2, shown in Figure 4.
In process of the test, the bulk deformation of Copper Foil is less, and the voltage at the electric current in loop or Copper Foil two ends is comparatively stable, and this moment, circuit theory diagrams were as shown in Figure 3; When the local stress on test specimen surface crackle occurs greater than the ultimate stress of Copper Foil or test specimen surface; Partial fracture promptly takes place in Copper Foil; At this moment; A sudden change will take place in loop current or expansion slot voltage, no matter be that people's meat is observed or this reaction can discerned or catch to computing machine all rapidly, and this moment, circuit theory diagrams were as shown in Figure 5.
Identical to the copper wire scheme with in length and breadth, Copper Foil need be provided with certain prestress before pasting; Different with copper wire slightly different be that the connection expansion slot at Copper Foil two ends has bigger rigidity, can pass through specific instrument, makes Copper Foil have fixing prestress value.
Have in addition be pointed out that the globality of Copper Foil is good than copper wire, the planarization of pasting is required also higher,, can make test findings bigger fluctuation occur if paste and exist space or bubble in the process.
Claims (6)
1. the determination methods of the critical destruction of torture test; The test specimen to be checked that carries out fatigue to failure test is done critical destruction to be judged; It is characterized in that, at first, be provided for the foil gauge that the critical destruction of test specimen to be checked is judged on the surface of test specimen to be checked; This foil gauge is copper mesh or Copper Foil, and said copper mesh or Copper Foil are pasted the surface that agent sticks on test specimen to be checked through efficient insulation; Then treat and inspect part and carry out fatigue to failure test, judge that through the destructiveness of copper mesh or Copper Foil the fatigure failure of carrying out test specimen to be checked judges.
2. according to the determination methods of the critical destruction of the said torture test of claim 1; It is characterized in that; The method that said copper mesh sticks on test specimen to be checked surface is: because of vertical direction and the parallel direction that fatigue to failure test produces principle stress horizontal copper wire, vertical copper wire are set accordingly at test specimen to be checked respectively; Laying copper mesh on test specimen to be checked surface, and vertically copper wire directly sticks on the surface of test specimen to be checked, simultaneously laterally copper wire, vertically the junction of copper wire directly bonds; Said each horizontal copper wire spacing is 1/10 ~ 1/15 of a test specimen minor face to be checked, and each vertical copper wire spacing is 1/10 ~ 1/15 of a test specimen minor face to be checked.
3. according to the determination methods of the critical destruction of the said torture test of claim 1; It is characterized in that; The method that Copper Foil sticks on test specimen to be checked surface is: directly Copper Foil is sticked on test specimen to be checked surface; And the length direction of Copper Foil is consistent because of fatigue to failure test produces the principle stress parallel direction with test specimen to be checked, and the lengthwise edge of Copper Foil does not go out the edge on test specimen to be checked surface.
4. according to the determination methods of the critical destruction of the said torture test of claim 3; It is characterized in that; The destructive determination methods of Copper Foil is: the two ends of Copper Foil length direction are connected the expansion slot connection respectively with one; Two connect expansion slot connects with checkout equipment, external power supply through lead, and this checkout equipment can be monitored the electric current or the voltage signal of Copper Foil, connection expansion slot, sealing series loop that checkout equipment, external power supply constituted.
5. according to the determination methods of the critical destruction of the said torture test of claim 4, it is characterized in that said checkout equipment is reometer or voltage table.
6. according to the determination methods of the critical destruction of the said torture test of claim 1, it is characterized in that it is oxirene that agent is pasted in said efficient insulation.
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| CN2012101766451A CN102706743A (en) | 2012-05-31 | 2012-05-31 | Judgment method for critical destruction of fatigue test |
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| CN2012101766451A CN102706743A (en) | 2012-05-31 | 2012-05-31 | Judgment method for critical destruction of fatigue test |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3979949A (en) * | 1975-06-30 | 1976-09-14 | The Boeing Company | Fatigue damage indicator |
| US5379644A (en) * | 1991-08-15 | 1995-01-10 | Shimizu Costruction Co., Ltd. | Strain or stress gauge and method for detecting strain or stress of structure using the same, and plastic composite material for foreknowing progress of breakdown of structure and method using the same |
| US20050284232A1 (en) * | 2004-06-25 | 2005-12-29 | Rice Brian P | Sensing system for monitoring the structural health of composite structures |
| US20060254366A1 (en) * | 2003-09-09 | 2006-11-16 | Caroline Williamson | Sensor and sensor array for monitoring a structure |
| CN101050985A (en) * | 2007-04-30 | 2007-10-10 | 哈尔滨工业大学 | Local monitoring pressure sensitive cement base stress and strain sensor of concrete structure |
| CN101946153A (en) * | 2008-01-03 | 2011-01-12 | 欧洲航空防务及航天公司Eads法国 | The equipment of the testing airplane structure of lead interrupt type |
-
2012
- 2012-05-31 CN CN2012101766451A patent/CN102706743A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3979949A (en) * | 1975-06-30 | 1976-09-14 | The Boeing Company | Fatigue damage indicator |
| US5379644A (en) * | 1991-08-15 | 1995-01-10 | Shimizu Costruction Co., Ltd. | Strain or stress gauge and method for detecting strain or stress of structure using the same, and plastic composite material for foreknowing progress of breakdown of structure and method using the same |
| US20060254366A1 (en) * | 2003-09-09 | 2006-11-16 | Caroline Williamson | Sensor and sensor array for monitoring a structure |
| US20050284232A1 (en) * | 2004-06-25 | 2005-12-29 | Rice Brian P | Sensing system for monitoring the structural health of composite structures |
| CN101050985A (en) * | 2007-04-30 | 2007-10-10 | 哈尔滨工业大学 | Local monitoring pressure sensitive cement base stress and strain sensor of concrete structure |
| CN101946153A (en) * | 2008-01-03 | 2011-01-12 | 欧洲航空防务及航天公司Eads法国 | The equipment of the testing airplane structure of lead interrupt type |
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Application publication date: 20121003 |