CN100565175C - Carry out the method for analysis of fatigue and detection with infrared thermal imagery - Google Patents
Carry out the method for analysis of fatigue and detection with infrared thermal imagery Download PDFInfo
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- CN100565175C CN100565175C CNB2006100804906A CN200610080490A CN100565175C CN 100565175 C CN100565175 C CN 100565175C CN B2006100804906 A CNB2006100804906 A CN B2006100804906A CN 200610080490 A CN200610080490 A CN 200610080490A CN 100565175 C CN100565175 C CN 100565175C
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Abstract
The invention discloses a kind of method of carrying out analysis of fatigue and detection with infrared thermal imagery, treat test block and carry out CYCLIC LOADING under the different loads level, institute adds load to be increased from low to high, lowest load is not less than and makes test specimen that the minimum load value of temperature rise be arranged, under each load level, the cycle index that loads is greater than making the stable loaded cycle number of times of test specimen intensification, record test specimen to be measured different surface temperatures constantly under different loads with thermal infrared imager, after measured data processing, obtain two different straight lines of slope, the pairing abscissa value of the intersection point of these two straight lines is the fatigue limit of test specimen to be measured.Record test specimen to be measured after different surface temperatures constantly under the different loads with thermal infrared imager, can obtain the fatigue limit of this test specimen, and because at least two data under the data on the fatigue limit and at least two fatigue limits in the data are carried out linear fit respectively, make that analysis result is accurate more, the scope of application is wider.
Description
Technical field
The present invention relates to a kind of fatigue analysis method of test specimen, specifically refer to a kind of method of carrying out analysis of fatigue and detection with infrared thermal imagery.
Background technology
Intensity, rigidity and fatigue are to three basic demands of engineering structure and machinery use, determine that structure and mechanical fatigue method of life mainly contain two classes: test method(s) and analysis of experiments method.The traditional experiment method determines to depend on fatigue lifetime a large amount of tests, and it is directly by obtaining needed fatigue data with the same or analogous a large amount of tests of actual conditions.This method is reliable, but length often consuming time, need many with test specimen, cause the analysis of fatigue work period long, experimentation cost is higher, its feasibility is subjected to severely restricts.The analysis of experiments method is the fatigue behaviour according to material, and the load history that contrast structure is suffered is determined fatigue lifetime of structure by analytical model.Though reduced the dependence of analysis of fatigue for a large amount of tests, the reliability of its analysis result is usually too poor.And some other experimental measurement crack stress intensity factor that utilizes carries out the method that the fatigue of materials destruction characteristic is analyzed then, is closely connected with Micromechanics and is in the same place, and is not suitable for directly applying to engineering and industrial design.
In recent years, Infrared Thermography Technology has been applied in the analysis of fatigue research, and the initial application of Infrared Thermography Technology in Fatigue Failure Study is to change to determine crack position by the observation component surface temperature.Surface temperature by test specimen in the record CYCLIC LOADING process changes, and analyzes the fatigue characteristic parameter of given test specimen.And Italian scholar A.Risitano is with above-mentioned utilized method application that Infrared Thermogram determines fatigue limit of materials patent, called after Risitano method.But in the processing procedure of Risitano method, do not consider the temperature variation that non-fatigue effect such as viscosity produce
Summary of the invention
At above-mentioned condition, the object of the present invention is to provide a kind of viscosity of considering to make measurement result carry out the method for analysis of fatigue and detection more accurately with infrared thermal imagery to Temperature Influence.
For achieving the above object, technical solution of the present invention is:
A kind of method of carrying out analysis of fatigue and detection with infrared thermal imagery, treat test block and carry out CYCLIC LOADING under the different loads level, institute adds load to be increased from low to high, lowest load is not less than and makes test specimen that the minimum load value of temperature rise be arranged, under each load level, the cycle index that loads is greater than making the stable loaded cycle number of times of test specimen intensification, record test specimen to be measured different surface temperatures constantly under different loads with thermal infrared imager, after measured data processing, obtain the relation curve of temperature rise and cycle index under the different stress levels, to this relation curve secondary treating, obtain the relation data that load amplitude on the test specimen adds average load and temperature rise, utilize least square method to carry out linear fit respectively at least two data under the data on the fatigue limit and at least two fatigue limits in the data, obtain two different straight lines of slope, the pairing abscissa value of the intersection point of these two straight lines is the fatigue limit of test specimen to be measured.
Further, the relation curve of the cycle index when obtaining load and test specimen temperature stabilization according to the relation curve of temperature rise and cycle index under the different stress levels is estimated fatigue lifetime of test specimen to be measured.
Further, the relation curve of the cycle index the when relation curve of the cycle index during according to above-mentioned load and test specimen temperature stabilization obtains stress and test specimen temperature stabilization, thus obtain the focus stress distribution and the evolution rule of test specimen.
Further, described test specimen to be measured is workpiece and member.
Further, the cycle index that loads under described each load level is greater than making 20% of the stable loaded cycle number of times of test specimen intensification.
Adopt said method, record test specimen to be measured after different surface temperatures constantly under the different loads with thermal infrared imager, can obtain the fatigue limit of this test specimen, and owing to utilize least square method to carry out linear fit respectively at least two data under the data on the fatigue limit and at least two fatigue limits in the data, make analysis result more accurate, and be applicable to the workpiece and the member of various material different shapes, the scope of application is wider, and can further estimate the fatigue lifetime of test specimen and the focus stress distribution of test specimen.
Description of drawings
Fig. 1 is that surface temperature changes synoptic diagram in the test specimen fatigure failure process;
Fig. 2 is that the test specimen surface temperature changes synoptic diagram under the different loads effect;
Fig. 3 determines fatigue limit of materials synoptic diagram for utilizing the stabilization sub stage temperature;
Fig. 4 utilizes initial temperature gradient to determine the synoptic diagram of the fatigue limit of materials;
The test specimen surface temperature image synoptic diagram that Fig. 5 gathers for thermal infrared imager;
Fig. 6 is temperature rise and a cycle index relation curve under the different stress levels;
Fig. 7 is stress level and test specimen temperature rise graph of a relation;
Fig. 8 is for carrying out the figure as a result behind the linear fit respectively to data.
Embodiment:
Specify the present invention below:
The fatigue of material is the process of an energy dissipation, and temperature variation is the important parameter of research fatigue process, and it not only can determine the position of fatigue damage, and can monitor its evolutionary process intuitively.Heat dissipate what not only reflected the difference of the different destructive processs of material, also embodied the irreversible feature of material damage process.
The researchist sums up from a large amount of experiments: temperature variation can be divided into three obvious stages of feature as shown in Figure 1 in the fatigue of materials process, Δ T be in the experimentation test specimen at cyclic loading effect lower surface maximum temperature T and room temperature T
0Poor.Experiment is found, under the certain condition of load frequency, surpasses the fatigue limit σ of material when load
0The time, temperature variation is divided into following several stages:
Phase one---the initial temperature rise stage (Phase1).Most of heat dissipated and was used to improve the temperature of sample because the temperature difference of test specimen and environment is less, and the thermal loss in the convection process is fewer this stage, and the test specimen surface temperature rises very fast, until temperature stabilization.The time that its temperature rises, inferior comparing of the circulating cycle during with destruction only accounts for the very little part of whole fatigue lifetime.Usually, when load was kept off yield limit, it can not surpass 10% in the ratio that test specimen occupied in the whole life-span.
Subordinate phase---the temperature stabilization stage (Phase2).In this stage, because the exchange heat of the heat dissipation of test specimen and test specimen and environment is roughly suitable, so temperature variation is slow relatively, and temperature is relatively stable.The length of time in temperature stabilization stage is because the difference of load can alter a great deal.Load big more (greater than fatigue limit time), temperature value was high more when material reached the stabilization sub stage, and the time is as shown in Figure 2 short more.When the load that applies during near the material yield limit, this time in stage of temperature stabilization is very limited or almost do not have.Load is high more, and the temperature value when speed that the phase one temperature rises and subordinate phase are stablized is corresponding high more.
Phase III---temperature raise the stage fast (Phase3).Crackle enters extension phase in this stage test specimen, owing to split the energy snap-out release of point, causes splitting the tip temperature fast rise.Temperature is fast rise in very short time, until destroying.
1986, people such as Curti were by carrying out fatigue experiment to modified iron test specimen, and utilized thermal infrared imager to note its temperature changing regularity, in conjunction with lot of experiment results, had proposed a kind of new method of determining the fatigue limit of materials fast.Experiment shows that under the loading that is being higher than fatigue limit, the temperature value in temperature stabilization stage and magnitude of load have approximate linear in the fatigue of materials destructive process.So, the fatigue limit of material can be by drawing the temperature stabilization stage under the different loads level temperature value (Fig. 3) or starting stage temperature gradient (Fig. 4) and load between the curve that changes determine that fatigue stress limits is exactly the intersection point of curve and load transverse axis.
According to above-mentioned rule, the present invention adopts following method, in the following air dielectric of room temperature (22 ℃), test specimen is fixed on the testing machine, this testing machine is selected for use and is made every effort to achieve the 100KN HF fatigue testing machine, test specimen is selected the ordinary steel test specimen for use, at first estimate to make test specimen that the lower limit of the load level of temperature rise be arranged, then same test specimen is carried out CYCLIC LOADING under the different loads level, load on test specimen by testing machine, loading environment is for drawing--draw luffing symmetrical cycle load, be averaged load 10KN in the process of the test, amplitude is by 4KN, is increased to 8KN successively by the increment of 1KN, increment by 0.5KN is increased to 10.5KN again, test specimen fracture after amplitude reaches 10.5KN, under each load level, the cycle index of loading is greater than and makes the test specimen stable loaded cycle number of times that heats up, generally get greater than making 20% of the stable loaded cycle number of times of test specimen intensification, loading frequency is resonant frequency 133.6Hz; Each is decided the load loaded cycle and finishes, and makes test specimen return to room temperature, carries out the CYCLIC LOADING of next load value again.In the loading procedure, adopt ThermalCAM
TMThe E65 thermal infrared imager is gathered different thermography such as Fig. 5 constantly under the different loads level respectively, thereby obtains different temperature constantly under the different loads level of test specimen surface;
We to the data of being gathered in the experiment after treatment, obtain the relation curve of temperature rise and cycle index under the different stress level shown in Figure 6, horizontal ordinate is represented cycle index among the figure, ordinate is a temperature rise value, lines from top to bottom represent respectively the load amplitude when 4KN is increased to 10.5KN temperature rise and the relation curve of cycle index, time * the loading frequency of cycle index=experience is got room temperature and is roughly 22 ℃, test specimen temperature rise=test specimen hot face temperature-room temperature.
Load is not that temperature rise curve of 20.5KN when not considering test specimen destruction, and the data among Fig. 6 are carried out secondary treating, obtains result shown in the following table:
The load amplitude adds the relation data of average load and temperature rise
Data in the above table are painted in rectangular coordinate a little, simultaneously load is transformed to stress (stress=load/area of section), obtain result shown in Figure 7.
The first five data under the data on the fatigue limit and back three fatigue limits utilizes least square method to carry out linear fit respectively in the his-and-hers watches, obtain two straight lines shown in Fig. 8, horizontal ordinate represents that stress, ordinate represent temperature, obtain after the straight line that slope among the figure is little is handled the first five data, obtain after the straight line that slope is big is handled back three data.By finding out among the figure, the pairing horizontal ordinate of the intersection point of two straight lines is the fatigue limit of material, and the fatigue limit that can draw this kind material from figure is about 264MPa.
The relation curve of the cycle index when obtaining load and test specimen temperature stabilization according to the relation curve of temperature rise and cycle index under the different stress levels is estimated fatigue lifetime of test specimen to be measured.
The relation curve of the cycle index the when relation curve of the cycle index during according to above-mentioned load and test specimen temperature stabilization obtains stress and test specimen temperature stabilization, thus the focus stress envelope of test specimen obtained.
In addition, optional workpiece and the member of selecting various materials, different shape of described test specimen to be measured.
Claims (5)
1, a kind of method of carrying out analysis of fatigue and detection with infrared thermal imagery, it is characterized in that, treat test block and carry out CYCLIC LOADING under the different loads level, institute adds load to be increased from low to high, lowest load is not less than and makes test specimen that the minimum load value of temperature rise be arranged, under each load level, the cycle index that loads is greater than making the stable loaded cycle number of times of test specimen intensification, record test specimen to be measured different surface temperatures constantly under different loads with thermal infrared imager, after measured data processing, obtain the relation curve of temperature rise and cycle index under the different stress levels, to this relation curve secondary treating, obtain the relation data that load amplitude on the test specimen adds average load and temperature rise, utilize least square method to carry out linear fit respectively at least two data under the data on the fatigue limit and at least two fatigue limits in the data, obtain two different straight lines of slope, the pairing abscissa value of the intersection point of these two straight lines is the fatigue limit of test specimen to be measured.
2, method of carrying out analysis of fatigue and detection with infrared thermal imagery as claimed in claim 1, it is characterized in that, the relation curve of the cycle index when obtaining described load amplitude and add average load and test specimen temperature stabilization according to the relation curve of temperature rise and cycle index under the different stress levels is estimated fatigue lifetime of test specimen to be measured.
3, method of carrying out analysis of fatigue and detection with infrared thermal imagery as claimed in claim 2, it is characterized in that, the relation curve of the cycle index the when relation curve of the cycle index when adding average load and test specimen temperature stabilization according to above-mentioned load amplitude obtains stress and test specimen temperature stabilization, thus the focus stress distribution and the evolution rule of test specimen obtained.
4, method of carrying out analysis of fatigue and detection with infrared thermal imagery as claimed in claim 1 is characterized in that, described test specimen to be measured is workpiece and member.
5, method of carrying out analysis of fatigue and detection with infrared thermal imagery as claimed in claim 1 is characterized in that, the cycle index that described each load level loads down is greater than making 20% of the stable loaded cycle number of times of test specimen intensification.
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| CN101598650B (en) * | 2009-06-24 | 2012-07-25 | 深圳市网蓝实业有限公司 | Method for determining load-life curve and working life of component |
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| CN103076243A (en) * | 2012-12-07 | 2013-05-01 | 太原理工大学 | System for predicting fatigue limit of magnesium alloy member based on infrared thermal imaging, and method thereof |
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| CN108254410B (en) * | 2017-12-27 | 2020-04-03 | 中国人民解放军陆军装甲兵学院 | Spraying layer contact fatigue life prediction method and device based on infrared detection |
| CN110826203A (en) * | 2019-10-25 | 2020-02-21 | 成都大汇智联科技有限公司 | Method for evaluating fatigue life of connecting bolt of top cover of water turbine and monitoring system |
| CN112824867B (en) * | 2019-11-21 | 2022-11-25 | 湖南大学 | Method and device for testing fatigue limit of metal material |
| CN111504818A (en) * | 2020-04-22 | 2020-08-07 | 南京蜂动检测科技有限公司 | Method for detecting fatigue life of aluminum alloy for rail transit |
| CN112284595B (en) * | 2020-10-28 | 2022-03-15 | 湖南大学 | Stress measuring method, device and equipment for metal component and storage medium |
| CN114065556B (en) * | 2022-01-14 | 2022-05-03 | 湖南大学 | Amplitude-variable fatigue life prediction method based on dissipation energy |
| CN115684271B (en) * | 2022-12-30 | 2023-04-07 | 北京迈思发展科技有限责任公司 | Formed steel bar qualification detection method based on image recognition |
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| CN86103893A (en) * | 1986-06-08 | 1988-02-10 | 洛阳工学院 | The method of fast measuring contact fatigue strength limit of material |
| EP0577512A1 (en) * | 1992-06-30 | 1994-01-05 | Association Pour La Recherche Et Le Developpement Des Methodes Et Processus Industriels (Armines) | Method and apparatus for determining the fatigue limit of a material |
| CN1598557A (en) * | 2003-09-19 | 2005-03-23 | 中国科学院金属研究所 | Method for detecting fatigue damage of metal structure |
| RU2252409C2 (en) * | 2003-04-17 | 2005-05-20 | Сидоров Олег Тихонович | Method for testing fatigue |
| JP2005249597A (en) * | 2004-03-04 | 2005-09-15 | Toyota Motor Corp | Evaluation method for fatigue life and its system |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN86103893A (en) * | 1986-06-08 | 1988-02-10 | 洛阳工学院 | The method of fast measuring contact fatigue strength limit of material |
| EP0577512A1 (en) * | 1992-06-30 | 1994-01-05 | Association Pour La Recherche Et Le Developpement Des Methodes Et Processus Industriels (Armines) | Method and apparatus for determining the fatigue limit of a material |
| RU2252409C2 (en) * | 2003-04-17 | 2005-05-20 | Сидоров Олег Тихонович | Method for testing fatigue |
| CN1598557A (en) * | 2003-09-19 | 2005-03-23 | 中国科学院金属研究所 | Method for detecting fatigue damage of metal structure |
| JP2005249597A (en) * | 2004-03-04 | 2005-09-15 | Toyota Motor Corp | Evaluation method for fatigue life and its system |
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