CN1191969A

CN1191969A - Non-destructive thermal image detection method for pressure container

Info

Publication number: CN1191969A
Application number: CN97101246A
Authority: CN
Inventors: 黄毅; 许聪; 徐军; 李伟
Original assignee: Institute of Metal Research of CAS
Current assignee: Institute of Metal Research of CAS
Priority date: 1997-02-25
Filing date: 1997-02-25
Publication date: 1998-09-02
Anticipated expiration: 2017-02-25
Also published as: CN1069408C

Abstract

The detection method is that pressure container surface is painted with IR paint of emissivity greater than 0.9 and the container is placed before background of thermal shield plate; pressure container is pressurized at the pressure rise speed greater than 1 MPa/s while obtaining the thermal image of container with IR thermal imaging system and the place with obvious cold emission or largest stress is found out through comparison of serial thermal images; pressure container is unloaded and the place with obvious hot emission or most concentrated stress is found out similarly. The said method can detect the practical stress distribution and hidden defect of pressure container without destruction.

Description

A kind of non-destructive thermal image detection method of pressure vessel

The present invention relates to safety assessment and Dynamic Non-Destruction Measurement, a kind of non-destructive thermal image detection method that is used for pressure vessel is provided especially.

Pressure vessel all has a wide range of applications at industrial circle and space industry, the security of its work, serviceable life and after using after a while, be damaged and degree that defective occurs is the subject matter that people paid close attention to always, for a long time, though the nondestructive examination that some are conventional and the method for inspection can be detected a flaw and detect defective pressure vessel, but these methods generally are the Static Detection of carrying out under off working state, detected result also can only or have the time of wound to reflect and to say something at defectiveness, for pressure vessel under in working order the actual stress distribution situation and potential defective, these methods are just powerless.

The object of the present invention is to provide the actual stress distribution situation of a kind of pressure vessel under in working order and the lossless detection method of potential defective.

The invention provides a kind of non-destructive thermal image detection method of pressure vessel, it is as follows to it is characterized in that detecting step:

(1) be coated with infrared coating in Surface Pressure Vessel, the surface ratio emissivity value that requires infrared coating is greater than 0.9;

(2) before the pressure vessel that will be coated with infrared coating placed the background that is made of heat shield plate, heat shield plate was rough surface produces diffuse scattering to infrared ray a material;

(3) in the working pressure range of pressure vessel, pressure vessel is suppressed, the rate of rise is greater than 1MPa/sec, simultaneously with thermal infrared imager obtain initially, in the process and the pressure vessel thermal map of final state, by the contrast of serial thermal map being found out the most tangible place of infrared cold emission (IRCE) in the thermal map, promptly corresponding to the stress maximum position;

(4) to the pressure vessel release, obtain in initial, the process equally and the thermal map of final state, by contrast, find out infra-red heat emission (IRHE) the most tangible place in the thermal map, promptly corresponding to the most concentrated position of stress to serial thermal map.

Solid material is under the state of stress load, and according to thermoelastic effect, the temperature of itself will change, and the variation in this temperature field is relevant with the stress and strain of material itself.Especially, under elastic range and adiabatic condition, the temperature variation of object and the relation of its stress are shown in (1) formula

σ=-K Δ T/T _o(1) in the formula, Δ T is the increment of object temperature, T _oBe the temperature of object when not stressing, K is a constant, is that σ is the stress of object by the thermal behavior of object and elastic performance decision.According to this expression formula, can draw elastic stretching load and cause cooling, elastic compression load causes that then temperature raises.In metal, also there is this kind effect, though very little on temperature variation.The present invention names this kind effect for infrared cold emission (IRCE) corresponds to elastic stretching load and infra-red heat emission (ICHE) respectively and corresponds to elastic compression load.As the pressure vessel of hardware, under elastic stress condition and adiabatic condition, also have infrared cold puberty (IRCE) and infra-red heat emission (IRHE) equally.The power of IRCE and IRHE with and thermal map type looks be relevant with the area of stress concentration and the defect area of pressure vessel, technical scheme proposed by the invention just is being based on that this point finishes.Generally, the Surface Pressure Vessel infrared emission characteristic that operating mode is used is extremely inhomogeneous, and the surface ratio emissivity that has extremely low (＜0.2) is so can not obtain any real infrared emission information.Adopt and improve the infrared coating of Surface Pressure Vessel than emissivity value, it reaches unanimity the Surface Pressure Vessel ε value under the operating mode (requiring ε＞0.9), and Surface Pressure Vessel is not produced influence such as any corrosion, and this class infrared coating can be a paint, clay, carbon black etc.For preventing of the influence of surrounding environment and pressure vessel self infrared radiation to detecting, adopting rough surface is the key of testing successfully to the material of infrared ray diffuse scattering and the heat shield plate of structure, the material of heat shield plate can be the various plastics of tool rough surface, paper, wood-based planet etc.

Non-destructive thermal image detection method of the present invention has detected following advantage to pressure vessel stress distribution situation in working order:

1. can reflect the stress distribution under pressure vessel in working order truly, stress maximum on the pressure vessel and area of stress concentration just can obtain intuitively by analyzing.

2. if container exists certain defective and damage and corrosion etc., detection by this method can both be diagnosed, especially some defective during also at germination period this method just can come out by early prediction.This is that other detection means is not accomplished.

3. noncontact completely, harmless detection also need not measured body is implemented radiation exposure, and easy and simple to handle, the efficient height can carry out long-term monitoring rate to measured object, and even set up Data Base Pile.

4. can be developed into portable detection system, the pressure vessel that the scene is used detects at any time, and compares safety.Below by embodiment in detail the present invention is described in detail.

1 20 liters of steel balls of accompanying drawing photo in kind;

The thermal map of 2 20 liters of steel balls of accompanying drawing when pressure is 10MPa, wherein dark blue look zone shows that IRCE is bigger;

Thermal map during 3 20 liters of steel ball pressurizations of accompanying drawing 20MPa;

4 20 liters of steel balls of accompanying drawing increase the thermal map that changes with stress;

1 second thermal map after 5 20 liters of steel ball releases of accompanying drawing;

4 seconds thermal map after 6 20 liters of steel ball releases of accompanying drawing;

It is the 5MPa thermal map that 7 0.6 liters of steel cylinders of accompanying drawing are exploded the test original pressure;

8 0.6 liters of steel cylinder pressure of accompanying drawing are the 10MPa thermal map;

9 0.6 liters of steel cylinders of accompanying drawing are pressed and are increased to the 30MPa thermal map;

10 0.6 liters of steel cylinder pressure of accompanying drawing add to the 80MPa thermal map;

The variation of 11 0.6 liters of steel cylinders of accompanying drawing thermal map in exploding process;

It is 0MPa that 12 No. 2 0.6 liter of steel cylinders of accompanying drawing are exploded test thermal map pressure;

The thermal map of 13 No. 2 0.6 liter of steel cylinders of accompanying drawing when pressure is 30MPa;

The thermal map of 14 No. 2 0.6 liter of steel cylinders of accompanying drawing when pressure rises to 80MPa;

15 No. 2 0.6 liter of steel cylinder pressure 85MPa thermal maps of accompanying drawing.

Embodiment

Testing procedure is as follows:

1. to the geometric configuration of the pressure vessel that will test, size and specification are understood and are surveyed, for calibration is in the future got ready

2. evenly be sprayed on the surface of sample with the black quick-drying lacquer of height ratio emissivity, to guarantee the slin emissivity uniformity of sample

3. adopt shaggy former wood plywood (having the infrared diffuse performance) with pressure vessel and heat radiation environment isolation on every side

4. infra-red heat edge instrument probe is placed suitable position, connect every parts of infra-red thermal imaging instrument, as monitor and magnetic tape recorder etc.Connect with the mains the start initial adjustment.

5. after the start, observe the infrared video of the measured object in the display screen on the monitor, adjust the probe orientation, aim at next width of cloth of measured object postscript pressure vessel original elephant the during pressurized not.

6. begin to the pressure vessel pressurization, open tape recorder simultaneously and carry out thermal map seizure and record, should write down corresponding force value when every note one width of cloth resembles simultaneously with the speed of per 4 seconds one width of cloth elephants;

7. treat pressure increase to certain level after (needing decide as the case may be), can prolong time interval of record.

8. when release, beginning is kept to 0 with the speed record thermal image of 2 seconds one width of cloth elephants until pressure.

9. probe is changed an orientation other sightingpiston with measuring samples, repeating step 3 is to step 8 then.

10. carry out image processing in the thermal map input computing machine of noting in the time of will boosting, setting analysis variation in temperature distribution and force value, increase along with pressure, the temperature of sample can descend to some extent, pressure is big more, temperature descends obvious more, this phenomenon is called as infrared cold emission (IRCE), in thermal map, find out the most tangible place of IRCE, this is local just corresponding to the position of stress maximum, calculate the Δ T/T0 value at this place, will be worth substitution (1) formula then and just draw maximum stress value under certain pressure.The stress value of other point also can be obtained by this method.So, just can understand the stress distribution of entire container.

11. the thermal map of the pressure vessel after the release is input to one by one carries out image processing in the computing machine.During release, pressure constantly reduces, and the temperature of container will rise, and this phenomenon is called infra-red heat emission (IRHE), and IRHE can find out the position that stress is concentrated by observation, and it is more obvious to make that also the stress distribution gradient variable gets.

Above method is the basic step and the rules of pressure vessel non-destructive thermal image detection method, lifts the use that some examples illustrate this method below.

At first the method for IRCE is analyzed in explanation, the scene graph when Fig. 1 is 20 liters of steel ball actual measurements, and the material of steel ball is the 37SiMnCrNiMoV steel.Fig. 2 is a thermal map of suppressing when pressure is 10MPa in the examination process.According to IRCE, the skipper zone that temperature is lower on it is the zone of stress maximum.Along with the increase of pressure, this cool region will be along with expansion.Fig. 3 is the thermal map of this ball when pressure is 20MPa.Fig. 4 has shown that pressure a series of thermal maps from low to high change, the trend that changes of IRCE and the center of IRCE as can be seen from this figure, can obtain the temperature value of every bit in the thermal map image processing, the variation of this temperature value will can be converted to stress value by formula (1) as the data of following quantitative test.Secondly, about the visible Fig. 5 of the analysis of IRHE, the thermal map when Fig. 6, Fig. 5 begin release for container, Fig. 6 are 4 seconds thermal maps after the release.Temperature variation at the weld seam near zone of ball is comparatively obvious as can be seen from these two figure, and promptly IRHE is more obvious, illustrates that this zone is a region of stress concentration.Next lift some again and suppress the example that passes through thermal map detected pressures container explosion position in the certification test in destructiveness.Fig. 7 to Figure 11 is that 0.6 liter of steel cylinder (material is the D6AC steel) is exploded the several thermal maps that obtain in the test.Thermal map when Fig. 7 is 5MPa, small arrow indication position is the position of wanting explosion in the future among the figure, it is the maximum stress concentrated area of this gas cylinder, Fig. 8 is the thermal map of pressure when being 10MPa, small IRCE appears in the position of the front indication that this figure reflects, but also not fairly obvious, by the time IRCE that pressure should the zone when increasing to 30MPa just clearly.Fig. 9 is the thermal map of pressure when being 30MPa, after plasticity and surrender appear in pressure vessel, IRHE and very outstanding and obvious appears in this zone, sees that exceptions area shown in Figure 10 is about to the position of explosion just, and Figure 11 has showed 0.6 liter of a series of variation that steel cylinder is exploded the process thermal map.Figure 12 to Figure 15 is the thermal map of steel cylinder in exploding test of 0.6 liter of another, also can find out the variation of IRCE and IRHE from these figure, and actual explosion position is the place of arrow indication just.

Claims

1. the non-destructive thermal image detection method of a pressure vessel, it is as follows to it is characterized in that detecting step: