CN102607948B - Method for characterizing steel fatigue crack propagation behavior for casing drilling - Google Patents
Method for characterizing steel fatigue crack propagation behavior for casing drilling Download PDFInfo
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Abstract
The invention discloses a method for characterizing a steel fatigue crack propagation behavior for casing drilling. The method comprises the steps of: firstly, sampling casing drilling steel, preparing a sample and cleaning; secondly, carrying out low-frequency noise testing on the sample before fatigue; thirdly, carrying out fatigue testing on the sample; fourthly, carrying out low-frequency noise testing on the sample after fatigue; and fifthly, analyzing, extracting and processing low-frequency noise data before and after the fatigue testing according to low-frequency l/f noise information before and after the fatigue, and characterizing a fatigue crack propagation behavior of the sample. Through two times of low-frequency l/f noise testing before and after the fatigue propagation, the influence of background noise of the sample is eliminated, more complex formula derivation and mathematical calculation in common characterizing methods are avoided, no strict requirements are required for the shape of the sample, the fatigue testing quantity is favorably reduced, the testing cost is lowered, and the fatigue crack propagation behaviors of various samples can be conveniently subjected to sampling and fatigue service life estimation; and the method has the characteristics of convenience in use, low cost and convenience in popularization.
Description
Technical field
The present invention relates to Casing Drilling Technique field, be specifically related to the characterizing method of steel fatigue crack propagation for a kind of casing drilling, relate to the low-frequency noise characterizing method of steel crack Propagation for N80 casing drilling, be mainly used in the analysis of low frequency 1/f noise to N80 casing drilling steel crack Propagation performance, by the low-frequency noise information before and after contrast and analysis crack Propagation, thereby obtain tired information and the Crack Extension information of N80 casing steel.
Background technology
In actual oil-gas mining operation, the stressing conditions of sleeve pipe is very complicated.When sleeve pipe is on active service, not stopping under effect of periodicity alternative cycle load, fatigure failure, to start by a small margin increase, starts germinating at fatigue crack after damage after a while.It is generally acknowledged, the germinating of fatigue crack often occurs in the position of stress high concentration.The continuous opening and closing of crackle, expansion gradually, increases, and finally in the situation that stress is less than the strength of materials, there is no the sudden change of omen.This inefficacy is a kind of destruction that accumulates formula, has irreversible character.Once there is the economic loss that is difficult to estimation by bringing to oil gas field.The characterizing method of crack Propagation routine is to utilize Paris formula.The method is thought, second stage at Crack Extension, be stable or linear flaws spreading rate district, crack Propagation rate controlled in the stress-intensity factor range of crack tip, and the exponential relationship between fatigue crack growth rate and stress intensity factor is described.
Further research is found, C and m are material constant, and environmental factor all lies among constant as temperature, humidity, medium, loading frequency etc., conventionally by test data fitting, is obtained.But in test, seldom find that C and m are the phenomenons of constant, find that C increases along with the increase of stress ratio in some documents, m reduces along with the increase of stress.In other documents, m increases along with the increase of stress ratio.But in most of documents, the variation of m is random.The heterogeneous microstructure of material, the frequency of cyclic loading and waveform, environment, temperature and load ratio R use impact to C and m, and constant acquisition relevant with material microstructure in formula is very difficult, has seriously affected the promotion and application of this formula.
Because this model hypothesis is too simple, influence factor is too much, and therefore, from this model, the physical significance of extracting parameter is unclear, cannot analyze the local message of crack Propagation.All the time, through constantly correction and improved Paris formula have tens of kinds more than.
Noise, comes from fluctuation.The physical characteristics fluctuation research of condensed state matter is as existing many decades of an active research field, and these researchs have caused the attention of people's pair physical phenomenon relevant with fluctuation.All the time, in low-frequency noise, comprised much important information, usually by people, ignored.In this field, the most noticeable research topic is the research of ubiquitous 1/f noise.1/f noise is a kind of of low-frequency noise, and name origin that it is generally acknowledged 1/f noise is that the fluctuation due to lot of materials shows as: its power spectrum s(f) with
be directly proportional,
generally, near 1,1/f noise is with a wide range of applications, on the one hand the 1/f noise of " surplus " (
generally in 1 left and right) there is close relationship with some imperfection of system, thereby can be as latent defect in detected electrons and material; On the other hand, the 1/f(of " intrinsic "
=1) near, noise has reflected again natural perfection and harmony, yet uses it for the aspects such as musical composition to obtain the effect from create an aesthetic feeling.The most important thing is that the characterization method of low frequency 1/f noise is a kind of lossless detection method of sensitivity.Conventional Pairs characterizing method is by carrying out the expansion that fatigue crack is measured in destructive torture test on fatigue tester, often taking time and effort, and has the restriction of many objective factors and range estimation factor.And as mentioned before, the physical significance of the parameter that it obtains is often clear and definite not.Utilize low-frequency noise to characterize casing drilling and can avoid above shortcoming and defect by the crack Propagation of steel, because in the process of crack Propagation, germinating from crackle, expand to the termination of crackle, all be accompanied by the formation (by doing the methods such as SEM, AFM) of sample interior defect and the variation of sample electrical quantity, these variations, can gather out by data collecting card, through processing the low frequency 1/f noise information that changes into.
Summary of the invention
In order to overcome above-mentioned the deficiencies in the prior art, the object of the present invention is to provide the characterizing method of steel fatigue crack propagation for a kind of casing drilling, adopt low-frequency noise characterization method, by contrast standard specimen, (sample is made compact tension specimen (CT) sample by ASTM E647 standard, ) in the low-frequency noise of crack Propagation front and back, (be white noise, 1/f noise amplitude and γ value wherein), by the low-frequency noise information before and after comparative analysis crack Propagation, can realize exactly the behavior of the crack Propagation of N80 casing steel is grasped comparatively accurately and characterized, contribute to reduce torture test quantity, reduce experimentation cost, and it is easy to use not exist potential safety hazard to have, with low cost, be convenient to the feature of promoting.
To achieve these goals, the technical solution used in the present invention is: the characterizing method of steel fatigue crack propagation for a kind of casing drilling, utilize the feature of sample standard specimen low frequency 1/f noise before and after crack Propagation, in conjunction with the origin of the low frequency 1/f noise feature relevant with defect to the inherent crackle of sample, by the size of twice comparative analysis noise parameter, the fatigue crack propagation of analyzing casing steel, comprises the steps:
The first, casing drilling steel is sampled, sample preparation is also cleaned;
At box cupling place, (stress is comparatively concentrated) is followed successively by according to length and width are high
size the intercepting of N80 well casing steel, then according to ASTM E647 metric system, make CT sample, the high size of length and width of sample is followed successively by
, first test carries out presplitting to CT sample before carrying out, and presplitting length is 2 millimeters, the rust cleaning of the hydrochloric acid that is 1.0%～5.0% in volumetric molar concentration (HCl) solution, soak time is 1～3 minute; Then with ethanol and deionized water, clean respectively, soak time is 1～3 minute, and tangent plane grinds after polishing, adopts the HNO that 200 milliliters of volumetric molar concentrations are 2%～5%
3solution, cleans, and takes out and hangs up, and dries up;
The second, sample is carried out to the low frequency noise measurement before fatigue;
Sample is carried out to low frequency noise measurement, need under certain biasing, carry out, the present invention is with reference to the current potential reference point in plain fatigue test, respectively in the precrack both sides of sample, weld two lead-in wires, and be connected on noise testing platform, regulation voltage scope is 2.0～3.0V, when reaching needed biasing, together with bias unit, put sample into screened room, and carry out the low frequency noise measurement before fatigue, whole low frequency 1/f noise test is carried out in Cu net screened room, before test, need to carry out the test of ground unrest, and adopt physical means to reduce as much as possible ground unrest,
The 3rd, sample is carried out to torture test;
Sample is taken out from low frequency noise measurement system, being placed on model is on the microcomputer controlled electro-hydraulic servo fatigue tester of PLD-100, when command signal enters amplifier, control is from the hydraulic oil servo-valve of hydraulic power source, make the piston movement of hydraulic cylinder, stretch or compression sample, power sensor measure load force (or distortion) by signal feedback to amplifier and command signal comparison, form closed loop, the system that realizes is controlled, continuous recording load p and corresponding crack tip opening displacement V in loading procedure, the variation of crack tip opening displacement V has represented not yet crack initiation of crackle, crack initiation, the situation of stable expansion and unstable propagation, setting stress ratio is 0.1～0.7, until fatigue and cyclic 1 * 10
6till 0.1mm expansion does not occur inferior crackle, corresponding △ K is corresponding Crack Extension threshold value, when Crack Extension to 5～20mm, stops torture test,
The 4th, the sample after fatigue is carried out to low frequency noise measurement, sample is proceeded to the low frequency noise measurement after torture test, identical with step 2 of experimental technique and added biasing, to guarantee the contrast property of experimental data;
The 5th, according to low frequency 1/f noise information before and after tired, to the low-frequency noise data analysis before and after torture test, extract and process, sample crack Propagation situation is characterized, theoretical according to low-frequency noise, in the situation that other noise parameters approach,
the size of value is directly relevant with the origin of noise and the crackle of sample interior, defect;
Described HNO
3solution adopts straight alcohol to make solvent.
The invention has the beneficial effects as follows:
The present invention utilizes low frequency 1/f noise to carry out nondestructive characterisation (NDC) to the fatigue crack propagation of N80 casing steel owing to having adopted; By two infra-low frequency 1/f noises before and after Fatigue, test, eliminated the impact of sample copy body ground unrest, avoided the derivation of equation and mathematical computations comparatively complicated in general characterizing method; Simultaneously because the present invention is a kind of method with statistical significance, the shape of sample is not had to proper requirement, thereby the fatigue crack propagation of various samples is sampled and the assessment of fatigue lifetime easily, formula is simple, be easy to realize, and error is less.
Accompanying drawing explanation
Fig. 1 is the position sample figure of torture test and low frequency noise measurement sample in the embodiment of the present invention.
Fig. 2 is the CT figure of torture test and low frequency noise measurement sample in the embodiment of the present invention.
Embodiment
Below in conjunction with specific embodiment, the present invention is described in further detail.
Embodiments of the invention are signs of the fatigue crack propagation that carries out in N80 casing steel compact tension specimen (CT) as shown in Figure 2.With reference to Fig. 2, the present invention characterizes and provides following three embodiment the low frequency 1/f noise of the fatigue crack propagation of the N80 casing steel shown in Fig. 1.
embodiment mono-
A characterizing method for steel fatigue crack propagation for casing drilling, comprises the steps:
The first, the CT sample of N80 casing steel is eliminated rust, polishing and cleaning;
First CT sample is carried out to presplitting, presplitting length is 2 millimeters, with the hydrochloric acid solution that volumetric molar concentration is 1.0%, eliminates rust, and soak time is 1 minute; Then with ethanol and deionized water, clean respectively, soak time is 2 minutes, and tangent plane grinds after polishing, adopts the HNO that 200 milliliters of volumetric molar concentrations are 2%
3solution, described HNO
3solution adopts straight alcohol to make solvent, cleans, and takes out and hangs up, and dries up;
The second, N80 casing steel CT sample is carried out to the low frequency noise measurement before fatigue;
1) to rust cleaning and clean after the welding that goes between of the CT sample of N80 casing steel, being take in fatigue crack monitoring point in plain fatigue test in the present invention is current potential reference point, respectively in the precrack both sides of sample, two lead-in wires of burn-oning;
2) sample is carried out to the low frequency noise measurement before fatigue, a lead-in wire is wherein connected in the biasing circuit of making in advance, for the sake of assurance, the wire resistor of 50 ohm of connecting, then regulation voltage level is 2.0V; Another root lead-in wire connects the low-noise preamplifier on noise testing platform, the capture card of access computer after low-frequency noise signal amplifies, carry out data acquisition and spectrum analysis, when setting needed voltage, together with bias unit, put sample into screened room, and carry out the low frequency noise measurement before fatigue, it should be noted that, whole low frequency 1/f noise test is carried out in Cu net screened room, before test, need to carry out the test of ground unrest, and adopt physical means to reduce as much as possible ground unrest.
Utilize 1/f noise model:
(1)
Wherein f is frequency; A is the amplitude of white noise; B is the amplitude of 1/f noise;
for the noise figure factor.Test data is processed, and result is as following table:
The 3rd, sample is carried out to torture test;
Sample is taken out from low frequency noise measurement system, be placed on model and be on the fixture of microcomputer controlled electro-hydraulic servo fatigue tester of PLD-100, test temperature is room temperature, frequency is 10Hz, loading waveform is sinusoidal waveform, maximum load is 1.4kN, setting stress ratio is 0.1, sample is exchanged to high-cycle fatigue test, crack length is monitored by the auxiliary potential method of microcomputer, classification load shedding number percent remains on 5%, guarantees that crack extension under every grade of load is 4～6 times of plastic zone size under upper level load, until fatigue and cyclic 1 * 10 simultaneously
6till there is not 0.1mm expansion in inferior crackle, continuous recording load p and corresponding crack tip opening displacement V in loading procedure, the variation of crack tip opening displacement V has represented the situation of not yet crack initiation of crackle, crack initiation, stable expansion and unstable propagation, when Crack Extension is during to 5mm, stop torture test;
The 4th, sample is carried out to the low frequency noise measurement after fatigue;
Sample is proceeded to the low frequency noise measurement after torture test, identical with step 2 of experimental technique and added biasing, measure when the low frequency 1/f noise of Crack Extension during to 5mm, utilize 1/f noise model (1) to process test data, result is as following table:
The 5th, according to low frequency 1/f noise information before and after tired, crack Propagation situation to N80 casing steel characterizes, before and after contrast torture test, the result of the low frequency 1/f noise data of N80 casing steel, can find, no matter is the white noise amplitude in low-frequency noise information, 1/f noise amplitude and 1/f noise exponential factor, all obviously increase than corresponding noise figure before tired; Secondly, along with the increase of crack Propagation length, the numerical value of above three kinds of parameters is all monotonically increasing trend, and according to the correlation theory of low-frequency noise, the size of γ value and the defect of material internal are closely related.Therefore, can, by analyzing the variation of γ value, realize the behavior of sample crack Propagation is characterized.
embodiment bis-
The low-frequency noise characterizing method of casing steel fatigue crack propagation, include following steps:
The first, as the CT sample of N80 casing steel eliminates rust, polishing and cleaning;
Hydrochloric acid (HCl) solution that rust cleaning is 3.0% by volumetric molar concentration carries out, and soak time is 2 minutes; Then with ethanol and deionized water, clean respectively, soak time is 2 minutes, and tangent plane grinds after polishing, adopts the HNO that 200 milliliters of volumetric molar concentrations are 4.0%
3clean with the etchant of ethanolic solution, take out and hang up, dry up;
The second, N80 casing steel sample is carried out to the low frequency noise measurement before fatigue;
1) welding CT sample of rust cleaning and clean rear N80 casing steel being gone between.Being take in fatigue crack monitoring point in plain fatigue test in the present invention is current potential reference point, respectively in the precrack both sides of sample, and two lead-in wires of burn-oning;
2) sample is carried out to the low frequency noise measurement before fatigue, a lead-in wire is wherein connected in the biasing circuit of making in advance, for the sake of assurance, the wire resistor of 50 ohm of connecting, then regulation voltage level is 2.5 V; Another root lead-in wire connects the low-noise preamplifier on noise testing platform, the capture card of access computer after low-frequency noise signal amplifies, carry out data acquisition and spectrum analysis, when setting needed voltage, together with bias unit, put sample into screened room, and carry out the low frequency noise measurement before fatigue, it should be noted that, whole low frequency 1/f noise test is carried out in Cu net screened room, before test, need to carry out the test of ground unrest, and adopt physical means to reduce as much as possible ground unrest;
Utilize 1/f noise model:
(1)
Wherein f is frequency; A is the amplitude of white noise; B is the amplitude of 1/f noise;
for the noise figure factor.Test data is processed, and result is as following table:
The 3rd, sample is carried out to torture test;
Sample is taken out from low frequency noise measurement system, be placed on model and be on the fixture of microcomputer controlled electro-hydraulic servo fatigue tester of PLD-100, test temperature is room temperature, frequency is 10Hz, loading waveform is sinusoidal waveform, maximum load is 1.4kN, fixed stress ratio is 0.1, sample is exchanged to high-cycle fatigue test, crack length is monitored by the auxiliary potential method of microcomputer, classification load shedding number percent remains on 5%, guarantees that crack extension under every grade of load is 4～6 times of plastic zone size under upper level load, until fatigue and cyclic 1 * 10 simultaneously
6till there is not 0.1mm expansion in inferior crackle, continuous recording load p and corresponding crack tip opening displacement V in loading procedure, the variation of crack tip opening displacement V has represented the situation of not yet crack initiation of crackle, crack initiation, stable expansion and unstable propagation, when Crack Extension is during to 15mm, stop torture test;
The 4th, sample is carried out to the low frequency noise measurement after fatigue;
Sample is proceeded to the low frequency noise measurement after torture test, identical with step 2 of experimental technique and added biasing, measure when the low frequency 1/f noise of Crack Extension during to 15mm, utilize 1/f noise model (1) to process test data, result is as following table:
The 5th, according to low frequency 1/f noise information before and after tired, crack Propagation situation to N80 casing steel characterizes, before and after contrast torture test, the result of the low frequency 1/f noise data of N80 casing steel, can find, no matter is the white noise amplitude in low-frequency noise information, 1/f noise amplitude and 1/f noise exponential factor, all obviously increase than corresponding noise figure before tired; Secondly, increase along with crack Propagation length, the numerical value of above three kinds of parameters is all monotonically increasing trend, according to the correlation theory of low-frequency noise, the size of γ value and the defect of material internal are closely related, therefore, can, by analyzing the variation of γ value, realize the behavior of sample crack Propagation is characterized.
embodiment tri-
The low-frequency noise characterizing method of casing steel fatigue crack propagation, include following steps:
The first, as the CT sample of N80 casing steel eliminates rust, polishing and cleaning;
The available volumetric molar concentration that eliminates rust is that 5.0% hydrochloric acid (HCl) solution carries out, and soak time is 3 minutes; Then with ethanol and deionized water, clean respectively, soak time is 2 minutes, and tangent plane adopts the HNO that 200 milliliters of volumetric molar concentrations are 5% after grinding polishing
3solution, described HNO
3solution adopts straight alcohol to make solvent, cleans, and takes out and hangs up, and dries up;
The second, N80 casing steel sample is carried out to the low frequency noise measurement before fatigue;
1) to rust cleaning and clean after the welding that goes between of the CT sample of N80 casing steel, being take in fatigue crack monitoring point in plain fatigue test in the present invention is current potential reference point, respectively in the precrack both sides of sample, two lead-in wires of burn-oning;
2) sample is carried out to the low frequency noise measurement before fatigue, a lead-in wire is wherein connected in the biasing circuit of making in advance, for the sake of assurance, the wire resistor of 50 ohm of connecting, then regulation voltage level is 3.0V; Another root lead-in wire connects the low-noise preamplifier on noise testing platform, the capture card of access computer after low-frequency noise signal amplifies, carry out data acquisition and spectrum analysis, when setting needed voltage, together with bias unit, put sample into screened room, and carry out the low frequency noise measurement before fatigue, it should be noted that, whole low frequency 1/f noise test is carried out in Cu net screened room, before test, need to carry out the test of ground unrest, and adopt physical means to reduce as much as possible ground unrest;
Utilize 1/f noise model:
(1)
Wherein f is frequency; A is the amplitude of white noise; B is the amplitude of 1/f noise;
for the noise figure factor.Test data is processed, and result is as following table:
The 3rd, sample is carried out to torture test;
Sample is taken out from low frequency noise measurement system, be placed on model and be on the fixture of microcomputer controlled electro-hydraulic servo fatigue tester of PLD-100, test temperature is room temperature, frequency is 10Hz, loading waveform is sinusoidal waveform, maximum load is 1.4kN, fixed stress ratio is 0.1, sample is exchanged to high-cycle fatigue test, crack length is monitored by the auxiliary potential method of microcomputer, classification load shedding number percent remains on 5%, guarantees that crack extension under every grade of load is 4～6 times of plastic zone size under upper level load, until fatigue and cyclic 1 * 10 simultaneously
6till there is not 0.1mm expansion in inferior crackle, continuous recording load p and corresponding crack tip opening displacement V in loading procedure, the variation of crack tip opening displacement V has represented the situation of not yet crack initiation of crackle, crack initiation, stable expansion and unstable propagation, when Crack Extension is during to 20mm, stop torture test;
The 4th, sample is carried out to the low frequency noise measurement after fatigue;
Sample is proceeded to the low frequency noise measurement after torture test, identical with step 2 of experimental technique and added biasing, measure when the low frequency 1/f noise of Crack Extension during to 20mm, utilize 1/f noise model (1) to process test data, result is as following table:
The 5th, according to low frequency 1/f noise information before and after tired, the crack Propagation situation of N80 casing steel is characterized.Before and after contrast torture test, the result of the low frequency 1/f noise data of N80 casing steel, can find, no matter is the white noise amplitude in low-frequency noise information, 1/f noise amplitude and 1/f noise exponential factor, all obviously increase than corresponding noise figure before tired; Secondly, increase along with crack Propagation length, the numerical value of above three kinds of parameters is all monotonically increasing trend, according to the correlation theory of low-frequency noise, the size of γ value and the defect of material internal are closely related, therefore, can, by analyzing the variation of γ value, realize the behavior of sample crack Propagation is characterized.
Referring to Fig. 1, the sample position figure of N80 well casing steel box cupling place.
Referring to Fig. 2, according to ASTM E647 standard, Fig. 1 sample thief is made into the dimensional drawing of CT sample.
Claims (4)
1. a characterizing method for steel fatigue crack propagation for casing drilling, is characterized in that, comprises the steps:
The first, casing drilling steel is sampled, sample preparation is also cleaned;
At box cupling place, according to length and width are high, be followed successively by
size the intercepting of N80 well casing steel, then according to ASTM E647 metric system, make CT sample, the high size of length and width of sample is followed successively by
, first test carries out presplitting to CT sample before carrying out, and presplitting length is 2 millimeters, in the hydrochloric acid that is 1.0%～5.0% (HCl) solution, eliminates rust in volumetric molar concentration, and soak time is 1～3 minute; Then with ethanol and deionized water, clean respectively, soak time is 1～3 minute, and tangent plane grinds after polishing, adopts the HNO that 200 milliliters of volumetric molar concentrations are 2%～5%
3solution, described HNO
3solution adopts straight alcohol to make solvent, cleans, and takes out and hangs up, and dries up;
The second, sample is carried out to the low frequency noise measurement before fatigue;
Sample is carried out to low frequency noise measurement, need under certain biasing, carry out, with reference to the current potential reference point in plain fatigue test, respectively in the precrack both sides of sample, weld two lead-in wires, and be connected on noise testing platform, regulation voltage scope is 2.0～3.0V, when reaching needed biasing, together with bias unit, put sample into screened room, and carry out the low frequency noise measurement before fatigue, whole low frequency 1/f noise test is carried out in Cu net screened room, before test, need to carry out the test of ground unrest, and adopt physical means to reduce as much as possible ground unrest,
The 3rd, sample is carried out to torture test;
Sample is taken out from low frequency noise measurement system, being placed on model is on the microcomputer controlled electro-hydraulic servo fatigue tester of PLD-100, when command signal enters amplifier, control is from the hydraulic oil servo-valve of hydraulic power source, make the piston movement of hydraulic cylinder, stretch or compression sample, power sensor measure load force by signal feedback to amplifier and command signal comparison, form closed loop, the system that realizes is controlled, continuous recording load p and corresponding crack tip opening displacement V in loading procedure, the variation of crack tip opening displacement V has represented not yet crack initiation of crackle, crack initiation, the situation of stable expansion and unstable propagation, setting stress ratio is 0.1～0.7, until fatigue and cyclic 1 * 10
6till 0.1mm expansion does not occur inferior crackle, corresponding △ K is corresponding Crack Extension threshold value, when Crack Extension to 5～20mm, stops torture test,
The 4th, the sample after fatigue is carried out to low frequency noise measurement, sample is proceeded to the low frequency noise measurement after torture test, identical with step 2 of experimental technique and added biasing, to guarantee the contrast property of experimental data;
The 5th, according to low frequency 1/f noise information before and after tired, to the low-frequency noise data analysis before and after torture test, extract and process, sample crack Propagation situation is characterized, theoretical according to low-frequency noise, in white noise amplitude, low frequency 1/f noise amplitude, in the approaching situation of 1/f noise exponential factor parameter
for the noise figure factor,
the size of value is directly relevant with the origin of noise and the crackle of sample interior, defect.
2. the characterizing method of steel fatigue crack propagation for a kind of casing drilling according to claim 1, is characterized in that, comprises the following steps:
The first, N80 casing steel CT sample is eliminated rust, polishing and cleaning;
First CT sample is carried out to presplitting, presplitting length is 2 millimeters, with the hydrochloric acid solution that volumetric molar concentration is 1.0%, eliminates rust, and soak time is 1 minute;
Then with ethanol and deionized water, clean respectively, soak time is 2 minutes, and tangent plane grinds after polishing, adopts the HNO that 200 milliliters of volumetric molar concentrations are 2%
3solution, described HNO
3solution adopts straight alcohol to make solvent, cleans, and takes out and hangs up, and dries up;
The second, N80 casing steel CT sample is carried out to the low frequency noise measurement before fatigue;
1) welding CT sample of rust cleaning and clean rear N80 casing steel being gone between, in the plain fatigue of take test, fatigue crack monitoring point is current potential reference point, respectively in the precrack both sides of sample, two lead-in wires of burn-oning;
2) sample is carried out to the low frequency noise measurement before fatigue, a lead-in wire is wherein connected in the biasing circuit of making in advance, for the sake of assurance, the wire resistor of 50 ohm of connecting, then regulation voltage level is 2.0V; Another root lead-in wire connects the low-frequency noise prime amplifier on noise testing platform, the capture card of access computer after low-frequency noise signal amplifies, carry out data acquisition and spectrum analysis, when setting needed voltage, together with bias unit, put sample into screened room, and carry out the low frequency noise measurement before fatigue, it should be noted that, whole low frequency 1/f noise test is carried out in Cu net screened room, before test, need to carry out the test of ground unrest, and adopt physical means to reduce as much as possible ground unrest;
Utilize 1/f noise model:
(1)
Wherein f is frequency; A is the amplitude of white noise; B is the amplitude of 1/f noise;
for the noise figure factor, test data is processed;
The 3rd, sample is carried out to torture test;
Sample is taken out from low frequency noise measurement system, be placed on model and be on the fixture of microcomputer controlled electro-hydraulic servo fatigue tester of PLD-100, test temperature is room temperature, frequency is 10Hz, loading waveform is sinusoidal waveform, maximum load is 1.4kN, setting stress ratio is 0.1, sample is exchanged to high-cycle fatigue test, crack length is monitored by the auxiliary potential method of microcomputer, classification load shedding number percent remains on 5%, guarantees that crack extension under every grade of load is 4～6 times of plastic zone size under upper level load, until fatigue and cyclic 1 * 10 simultaneously
6till there is not 0.1mm expansion in inferior crackle, continuous recording load p and corresponding crack tip opening displacement V in loading procedure, the variation of crack tip opening displacement V has represented the situation of not yet crack initiation of crackle, crack initiation, stable expansion and unstable propagation, when Crack Extension is during to 5mm, stop torture test;
The 4th, sample is carried out to the low frequency noise measurement after fatigue;
Sample is proceeded to the low frequency noise measurement after torture test, and identical with above-mentioned steps second of experimental technique and added biasing, measures when the low frequency 1/f noise of Crack Extension during to 5mm, utilizes 1/f noise model (1) to process test data;
The 5th, according to low frequency 1/f noise information before and after tired, crack Propagation situation to N80 casing steel characterizes, before and after contrast torture test, the result of the low frequency 1/f noise data of N80 casing steel, according to the correlation theory of low-frequency noise, the size of γ value and the defect of material internal are closely related, by analyzing the variation of γ value, realize the behavior of sample crack Propagation is characterized.
3. the characterizing method of steel fatigue crack propagation for a kind of casing drilling according to claim 1, is characterized in that, comprises the following steps:
The first, N80 casing steel CT sample is eliminated rust, polishing and cleaning;
Hydrochloric acid (HCl) solution that rust cleaning is 3.0% by volumetric molar concentration carries out, and soak time is 2 minutes; Then with ethanol and deionized water, clean respectively, soak time is 2 minutes, and tangent plane grinds after polishing, adopts the HNO that 200 milliliters of volumetric molar concentrations are 4%
3solution, described HNO
3solution adopts straight alcohol to make solvent, cleans, and takes out and hangs up, and dries up;
The second, sample is carried out to the low frequency noise measurement before fatigue;
1) welding CT sample of rust cleaning and clean rear N80 casing steel being gone between, in the plain fatigue of take test, fatigue crack monitoring point is current potential reference point, respectively in the precrack both sides of sample, two lead-in wires of burn-oning;
2) sample is carried out to the low frequency noise measurement before fatigue, a lead-in wire is wherein connected in the biasing circuit of making in advance, for the sake of assurance, the wire resistor of 50 ohm of connecting, then regulation voltage level is 2.5 V; Another root lead-in wire connects the low-frequency noise prime amplifier on noise testing platform, the capture card of access computer after low-frequency noise signal amplifies, carry out data acquisition and spectrum analysis, when setting needed voltage, together with bias unit, put sample into screened room, and carry out the low frequency noise measurement before fatigue, it should be noted that, whole low frequency 1/f noise test is carried out in Cu net screened room, before test, need to carry out the test of ground unrest, and adopt physical means to reduce as much as possible ground unrest;
Utilize 1/f noise model:
(1)
Wherein f is frequency; A is the amplitude of white noise; B is the amplitude of 1/f noise;
for the noise figure factor, test data is processed;
The 3rd, sample is carried out to torture test;
Sample is taken out from low frequency noise measurement system, be placed on model and be on the fixture of microcomputer controlled electro-hydraulic servo fatigue tester of PLD-100, test temperature is room temperature, frequency is 10Hz, loading waveform is sinusoidal waveform, maximum load is 1.4kN, fixed stress ratio is 0.1, sample is exchanged to high-cycle fatigue test, crack length is monitored by the auxiliary potential method of microcomputer, classification load shedding number percent remains on 5%, guarantees that crack extension under every grade of load is 4～6 times of plastic zone size under upper level load, until fatigue and cyclic 1 * 10 simultaneously
6till there is not 0.1mm expansion in inferior crackle; Continuous recording load p and corresponding crack tip opening displacement V in loading procedure, the variation of crack tip opening displacement V has represented the situation of not yet crack initiation of crackle, crack initiation, stable expansion and unstable propagation; When Crack Extension is during to 15mm, stop torture test;
The 4th, sample is carried out to the low frequency noise measurement after fatigue;
Sample is proceeded to the low frequency noise measurement after torture test, and identical with above-mentioned steps second of experimental technique and added biasing, measures when the low frequency 1/f noise of Crack Extension during to 15mm, utilizes 1/f noise model (1) to process test data;
The 5th, according to low frequency 1/f noise information before and after tired, crack Propagation situation to N80 casing steel characterizes, before and after contrast torture test, the result of the low frequency 1/f noise data of N80 casing steel, according to the correlation theory of low-frequency noise, the size of γ value and the defect of material internal are closely related, by analyzing the variation of γ value, realize the behavior of sample crack Propagation is characterized.
4. the characterizing method of steel fatigue crack propagation for a kind of casing drilling according to claim 1, is characterized in that, comprises the following steps:
The first, the CT sample of N80 casing steel is eliminated rust, polishing and cleaning;
The available volumetric molar concentration that eliminates rust is that 5.0% hydrochloric acid (HCl) solution carries out, and soak time is 3 minutes; Then with ethanol and deionized water, clean respectively, soak time is 2 minutes, and tangent plane grinds after polishing, adopts the HNO that 200 milliliters of volumetric molar concentrations are 5%
3solution, described HNO
3solution adopts straight alcohol to make solvent, cleans, and takes out and hangs up, and dries up;
The second, sample is carried out to the low frequency noise measurement before fatigue;
1) welding CT sample of rust cleaning and clean rear N80 casing steel being gone between, in the plain fatigue of take test, fatigue crack monitoring point is current potential reference point, respectively in the precrack both sides of sample, two lead-in wires of burn-oning;
2) sample is carried out to the low frequency noise measurement before fatigue, a lead-in wire is wherein connected in the biasing circuit of making in advance, for the sake of assurance, the wire resistor of 50 ohm of connecting, then regulation voltage level is 3.0V; Another root lead-in wire connects the low-frequency noise prime amplifier on noise testing platform, the capture card of access computer after low-frequency noise signal amplifies, carry out data acquisition and spectrum analysis, when setting needed voltage, together with bias unit, put sample into screened room, and carry out the low frequency noise measurement before fatigue, it should be noted that, whole low frequency 1/f noise test is carried out in Cu net screened room, before test, need to carry out the test of ground unrest, and adopt physical means to reduce as much as possible ground unrest;
Utilize 1/f noise model:
(1)
Wherein f is frequency; A is the amplitude of white noise; B is the amplitude of 1/f noise;
for the noise figure factor, test data is processed;
The 3rd, sample is carried out to torture test;
Sample is taken out from low frequency noise measurement system, be placed on model and be on the fixture of microcomputer controlled electro-hydraulic servo fatigue tester of PLD-100; Test temperature is room temperature, and frequency is 10Hz, and loading waveform is sinusoidal waveform, and maximum load is 1.4kN, and fixed stress ratio is 0.1, and sample is exchanged to high-cycle fatigue test; Crack length is monitored by the auxiliary potential method of microcomputer, and classification load shedding number percent remains on 5%, guarantees that crack extension under every grade of load is 4～6 times of plastic zone size under upper level load, until fatigue and cyclic 1 * 10 simultaneously
6till there is not 0.1mm expansion in inferior crackle; Continuous recording load p and corresponding crack tip opening displacement V in loading procedure, the variation of crack tip opening displacement V has represented the situation of not yet crack initiation of crackle, crack initiation, stable expansion and unstable propagation, when Crack Extension is during to 20mm, stop torture test;
The 4th, sample is carried out to the low frequency noise measurement after fatigue;
Sample is proceeded to the low frequency noise measurement after torture test, and identical with above-mentioned steps second of experimental technique and added biasing, measures when the low frequency 1/f noise of Crack Extension during to 20mm, utilizes 1/f noise model (1) to process test data;
The 5th, according to low frequency 1/f noise information before and after tired, crack Propagation situation to N80 casing steel characterizes, before and after contrast torture test, the result of the low frequency 1/f noise data of N80 casing steel, according to the correlation theory of low-frequency noise, the size of γ value and the defect of material internal are closely related, by analyzing the variation of γ value, realize the behavior of sample crack Propagation is characterized.
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| JP5571137B2 (en) * | 2012-08-13 | 2014-08-13 | 株式会社東芝 | Sealed secondary battery welding method, sealed secondary battery and cap body |
| CN103743636B (en) * | 2014-01-16 | 2015-11-18 | 清华大学 | A kind of method predicting welding joint threshold in fatigue crack propagation |
| CN105004766A (en) * | 2015-07-07 | 2015-10-28 | 中冶建筑研究总院有限公司 | Method for monitoring fatigue crack of surface of engineering structure |
| CN105352800B (en) * | 2015-11-13 | 2018-01-02 | 武汉钢铁有限公司 | Steel box-girder fatigue crack growth rate method of testing |
| CN105548281B (en) * | 2016-01-12 | 2018-04-17 | 中国地质大学（武汉） | A kind of nondestructive detection system and method based on Kelvin effect resistance excess noise |
| CN106053213B (en) * | 2016-08-02 | 2019-12-10 | 上海交通大学 | Manual loading device for industrial CT (computed tomography) in-situ tensile test |
| CN106706453B (en) * | 2016-12-05 | 2019-08-27 | 潍柴动力股份有限公司 | A kind of Parts test crack monitoring method |
| CN107084899A (en) * | 2017-05-16 | 2017-08-22 | 西安邮电大学 | A kind of fractal dimension characterizing method of Gas Pipeline Corrosion crack Propagation trend |
| CN107941611A (en) * | 2017-10-27 | 2018-04-20 | 西安石油大学 | A kind of method of the compound fatigue crack growth rates of definite I/III |
| CN108918690B (en) * | 2018-04-27 | 2020-09-01 | 佛山科学技术学院 | Ultrasonic fatigue-based casting high-temperature alloy anti-fatigue hot isostatic pressing repair evaluation model |
| CN111289566A (en) * | 2018-12-07 | 2020-06-16 | 中南大学 | Method for efficiently detecting quality of conductive film |
| CN112285140B (en) * | 2020-10-20 | 2022-01-28 | 北京航空航天大学 | Quantitative characterization method for early-stage propagation rate of internal crack of single crystal ultrahigh cycle fatigue |
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| US5837882A (en) * | 1997-06-05 | 1998-11-17 | Ntn Corporation | Stationary element rolling contact fatigue tester |
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