CN114813972A - Nondestructive evaluation method and system for service life of in-service polyethylene pipeline electric melting joint - Google Patents
Nondestructive evaluation method and system for service life of in-service polyethylene pipeline electric melting joint Download PDFInfo
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Abstract
The invention relates to a nondestructive evaluation method for service life of an in-service polyethylene pipeline electric melting joint, which comprises the following steps: establishing a corresponding relation between the width of the edge of a heat affected zone of a welding area of the electric fusion joint of the polyethylene pipeline and the service life in a laboratory in advance; carrying out ultrasonic phased array detection on an in-service polyethylene pipeline electric melting joint to be evaluated on site to obtain the width da of the edge of a heat affected zone of a welding area of the in-service polyethylene pipeline electric melting joint; and substituting the heat affected zone edge width da into the corresponding relation to obtain the service life tfa of the in-service polyethylene pipeline electric melting joint. The invention also relates to a corresponding evaluation system, which comprises the ultrasonic self-focusing linear array probe and a host computer provided with data analysis software. The method and the evaluation system can realize the quick and nondestructive evaluation of the service life of the urban buried polyethylene pipeline electric melting joint.
Description
Technical Field
The invention relates to the field of pipeline detection, in particular to a nondestructive evaluation method and a nondestructive evaluation system for service life of an in-service polyethylene pipeline electric melting joint.
Background
The polyethylene pipeline electric fusion welding joint is used as an important component for connecting a pipe network system, and plays a vital role in bridging the long-distance safe transportation of flammable and explosive media. However, due to the influence of the welding process and the subjective experience of the welder, the electric fusion joint of the polyethylene pipeline is easy to have process defects (cold welding or over welding), so that the long-term mechanical property of the joint of the pipeline is obviously weakened, the service life of the operation of the joint of the pipeline is shortened, and serious safety accidents are caused by medium leakage. Therefore, the service life evaluation of the in-service polyethylene pipeline electric melting joint plays an important technical guarantee role in maintaining the safe operation of the urban buried polyethylene pipeline.
At present, the service life prediction mode of the in-service polyethylene pipeline mainly adopts the international standard ISO 9080-2006 (the long-term flow hydrostatic strength of the thermoplastic pipe type material is determined by an inference method) established by the American Plastic pipeline Association as follows:
wherein, t f For failure life, T is hydrostatic test temperature, A, B, C, D is regression model parameter associated with specific material grade, σ θ Is the hoop stress of the coining.
However, this method has the following limitations: firstly, the method belongs to destructive tests, has huge evaluation equipment, cannot implement field detection, needs to carry out field pipe cutting and sampling, and then is carried back to a laboratory for testing, and not only has large engineering quantity and complicated flow, but also has high cost; secondly, the evaluation period is long, the evaluation period of the method at least needs more than 1 year, and the method does not meet the actual field inspection requirement.
Disclosure of Invention
Based on the method, the service life of the in-service polyethylene pipeline electric melting joint can be quickly and nondestructively evaluated.
The technical scheme adopted by the invention is as follows:
a nondestructive evaluation method for service life of an in-service polyethylene pipeline electric melting joint comprises the following steps:
establishing a corresponding relation between the width of the edge of a heat affected zone of a welding area of the electric fusion joint of the polyethylene pipeline and the service life in a laboratory in advance;
carrying out ultrasonic phased array detection on an in-service polyethylene pipeline electric melting joint to be evaluated on site to obtain the width d of the edge of a heat affected zone of a welding area of the in-service polyethylene pipeline electric melting joint a ；
The width d of the heat affected zone edge a Substituting the obtained product into the corresponding relation to obtain the service life t of the in-service polyethylene pipeline electric melting joint fa 。
The invention provides a corresponding relation model for establishing the heat affected zone edge width and the service life of the welding area of the polyethylene pipeline electric melting joint in a laboratory in advance, and according to the corresponding relation, only the heat affected zone edge width d of the welding area of the polyethylene pipeline electric melting joint in service is measured on site a So as to obtain the service life t of the in-service polyethylene pipeline electric melting joint fa 。
Moreover, the method disclosed by the invention adopts an ultrasonic phased array nondestructive testing technology to carry out scanning actual measurement on the site, belongs to a nondestructive evaluation mode, can carry out visual and nondestructive evaluation on the service life of the electric melting joint of the buried polyethylene pipeline without carrying out site destructive sampling on the pipeline joint, is convenient and fast to implement, overcomes the defects of long evaluation period, large engineering quantity and high cost of the existing evaluation method, and eliminates the complicated operations such as destructive tests and the like required by the existing evaluation method.
Specifically, the method for establishing the correspondence between the heat affected zone edge width and the service life of the welding area of the polyethylene pipeline electric melting joint in the laboratory comprises the following steps:
s1: according to different from each otherPreparing polyethylene pipeline electric melting joint samples in batches at welding time t, and then respectively carrying out ultrasonic phased array detection on the prepared electric melting joint samples to obtain the width d of the edge of a heat affected zone of the welding area of each electric melting joint sample i (ii) a The different welding time t is set to enable the polyethylene pipeline electric melting joint to form a series of welding time from severe cold welding to severe over welding;
s2: at different temperatures T and different aging times T f Respectively carrying out thermal oxidation aging tests on each electric melting joint sample prepared in the step S1, measuring the welding performance change coefficient P of each electric melting joint sample before and after aging, calculating the aging rate k of each electric melting joint sample at different temperatures T, and then obtaining the welding performance change coefficient P, the aging rate k and the aging time T of each electric melting joint sample through data fitting processing f The relationship I between the samples, and the relationship II between the aging rate k and the temperature T of each electrofusion joint sample;
s3: calculating the temperature T of the actual working condition according to the relation II obtained in the step S2 a Aging Rate k of lower electrofusion Joint test specimens i Coefficient of variation P of welding performance in combination with joint failure a Obtaining the temperature T of the actual working condition according to the relation I obtained in the step S2 a Service life t corresponding to failure of each electric melting joint sample fi And finally obtaining the edge width d of the heat affected zone of the electric fusion joint of the polyethylene pipeline by combining the ultrasonic phased array detection result of the step S1 i And service life t fi Corresponding relation d between i ～t fi ；
In the method, the heat affected zone edge width d of the in-service polyethylene pipeline electric melting joint is measured a Substituting into the corresponding relation d of step S3 i ～t fi In the process, the service life t of the in-service polyethylene pipeline electric melting joint is obtained fa 。
Specifically, in step S1, the material grade of the prepared polyethylene pipeline electric melting joint test sample is the same as that of the in-service polyethylene pipeline electric melting joint to be evaluated.
Specifically, in step S2, the different temperatures T are each set at 80 ℃ or above.
Specifically, in step S2, the different temperatures T are set to 80 ℃, 95 ℃, and 110 ℃, respectively.
Specifically, the different aging times t in step S2 f Set to 0h, 72h, 216h, 432h, 720h, respectively.
Specifically, step S2 further includes: performing a squeezing and stripping test on each electric melting joint sample respectively, and measuring the brittle stripping percentage C of each electric melting joint sample C And calculating the welding performance change coefficient P of each electric melting joint sample before and after aging, wherein the calculation formula is as follows:
H C ＝(1-C C )×100 (1)
P＝H C /H C0 (2)
in the formula (1), C C Percent brittle peeling of electrofused joint specimen, H C The welding performance of the aged electric fusion joint sample is shown;
in the formula (2), H C For the weldability of samples of electric fusion joints after ageing, H C0 The electric fusion joint sample welding performance before aging is shown.
Specifically, in step S2, the relationship I between the welding performance variation coefficient P of each electric fusion joint sample and the aging rate k and the aging time tf is obtained by data fitting processing by using the following formula:
in the formula (3), a and α are material-dependent constants of the electric fusion joint sample;
and (3) obtaining the relation II between the aging rate k and the temperature T of each electric melting joint sample by adopting the following formula and performing data fitting treatment:
k＝Be -(E/RT) (4)
in the formula (4), R is a gas constant, E is reaction activation energy, and B is a constant.
Specifically, in step S3, the temperature T of the actual operating condition a At room temperature, for exampleE.g. 20 ℃, and the welding performance variation coefficient P of joint failure is determined a Is 0.67.
The invention also provides an evaluation system used by the method, which comprises an ultrasonic self-focusing linear array probe and a host, wherein the ultrasonic self-focusing linear array probe is used for scanning the in-service polyethylene pipeline electric melting joint to be evaluated on site; the host machine acquires an ultrasonic phased array characteristic map measured by the ultrasonic self-focusing linear array probe through a signal transmission line, and then calculates the width d of the edge of a heat affected zone of the welding area of the in-service polyethylene pipeline electric-fusion joint by using data analysis software a Finally, the width d of the heat affected zone edge is determined a Substituting the obtained product into the corresponding relation between the heat affected zone edge width and the service life which is established in a laboratory in advance to obtain the service life t of the in-service polyethylene pipeline electric melting joint fa 。
The invention relates to a corresponding relation d established in a laboratory i ～t fi Storing the model into phased array host computer analysis software, and measuring the on-site actual edge width d of the welding surface heat affected zone of the in-service buried polyethylene pipeline electric melting joint to be measured a D to be tested a The service life t corresponding to the pipeline joint is automatically calculated by data analysis software after being transmitted to a phased array detection host through a data line fa Therefore, the service life of the in-service buried polyethylene pipeline electric melting joint can be rapidly and nondestructively predicted on site, the defects of long evaluation period, large engineering quantity and high cost of the existing evaluation method are overcome, and the complicated operations of destructive tests and the like required by the existing evaluation method are eliminated.
For a better understanding and practice, the invention is described in detail below with reference to the accompanying drawings.
Drawings
FIG. 1 is a schematic view of a nondestructive evaluation system for service life of an in-service polyethylene pipeline electric fusion joint of the invention;
FIG. 2A is a phased array map measured on an electrofusion joint specimen prepared with a weld time of 87 seconds;
FIG. 2B is a phased array map measured on an electrofusion joint sample prepared with a welding time of 30 seconds;
FIG. 2C is a phased array map measured on an electrofusion joint specimen prepared with a welding time of 135 seconds;
FIG. 3 is a graph showing the change of the width d of the edge of the heat-affected zone of the electrofusion joint specimen with the welding time t;
FIG. 4 shows the natural logarithm of the welding performance variation coefficient P of the electrofusion joint specimen at different temperatures and the aging time t f Linear fitting relationship diagram of (1);
FIG. 5 is a plot of the natural logarithm of the aging rate k of an electrofusion joint specimen as a linear fit to the reciprocal of the temperature T.
Detailed Description
The invention provides a nondestructive evaluation method for service life of an in-service polyethylene pipeline electric melting joint, which comprises the following steps:
establishing a corresponding relation between the width of the edge of a heat affected zone of a welding area of the electric fusion joint of the polyethylene pipeline and the service life in a laboratory in advance;
carrying out ultrasonic phased array detection on an in-service polyethylene pipeline electric melting joint to be evaluated on site to obtain the width d of the edge of a heat affected zone of a welding area of the in-service polyethylene pipeline electric melting joint a ；
The width d of the heat affected zone edge a Substituting the obtained product into the corresponding relation to obtain the service life t of the in-service polyethylene pipeline electric melting joint fa 。
As shown in figure 1, the service life nondestructive evaluation system for the in-service polyethylene pipeline electric melting joint provided by the invention comprises an ultrasonic self-focusing linear array probe 2, a signal transmission line 3 and a host machine 4.
The ultrasonic self-focusing linear array probe 2 is used for scanning an in-service polyethylene pipeline electric melting joint 1 to be evaluated on site. The host 4 is connected with the ultrasonic self-focusing linear array probe 2 through a signal transmission line 3, is provided with data analysis software, and stores the corresponding relation which is established in a laboratory in advance in the data analysis software.
The host 4 collects the ultrasonic phased array characteristic spectrum measured by the ultrasonic self-focusing linear array probe 2 through the signal transmission line 3, and then calculates the polyethylene in service by using data analysis softwareHeat affected zone edge width d of welding area of electric fusion joint 1 for olefin pipe a Finally, the width d of the heat affected zone edge is determined a Substituting the obtained product into the corresponding relation between the heat affected zone edge width and the service life which is established in a laboratory in advance to obtain the service life T of the in-service polyethylene pipeline electric melting joint 1 a 。
The method of the invention is specifically carried out according to the following steps:
the method comprises the following steps: preparing polyethylene pipeline electric melting joint samples S1, S2 and S3 … … in batches according to different welding time t in a laboratory, and then respectively carrying out ultrasonic phased array detection on each prepared electric melting joint sample to obtain the heat affected zone edge width d of each electric melting joint sample welding area i (d 1 、d 2 And d 3 … …); the different welding time t is set to enable the series of welding time from forming severe cold welding to forming severe overwelding of the polyethylene pipeline electrofusion joint.
In the first step, preferably, the material grade of the prepared polyethylene pipeline electric melting joint sample is the same as that of the in-service polyethylene pipeline electric melting joint to be evaluated.
By changing the welding process, i.e. setting different welding time t gradients (t) 1 、t 2 And t 3 … …) is set, the welding time t is set to include each welding time period from severe cold welding to severe overbonding of the joint, so as to prepare a batch of polyethylene pipeline electric melting joint samples S1, S2 and S3 … … which have the same brand number as the in-service polyethylene pipeline electric melting joint to be evaluated on site and contain different degrees of process defects, and ensure that the unknown state or defect of the in-service polyethylene pipeline electric melting joint to be evaluated is contained in the samples, so as to improve the accuracy and reliability of the final evaluation result.
Referring to fig. 2A to 2C and fig. 3, fig. 2A to 2C show phased array maps measured for 3 electrofusion joint samples prepared at different welding times by way of example, and fig. 3 shows a correlation between the width d of the heat affected zone edge and the welding time t of 5 electrofusion joint samples S1-S5 prepared at different welding times t by way of example, and a linear fitting curve. As shown in figure 2A of the drawings,according to welding time t 1 Heat affected zone edge width d of electrofusion joint specimen prepared as 87s 1 2.71 mm; as shown in fig. 2B, according to the welding time t 2 Heat affected zone edge width d of electrofusion joint specimen prepared at 30s 2 1.31mm, as shown in fig. 2C, according to the welding time t 3 Heat affected zone edge width d of electrofusion joint test specimen prepared in 135s 3 ＝4.27mm。
It can be seen that the edge width d of the melting region, i.e., the Heat Affected Zone (HAZ), of the electrofusion joint samples prepared at different welding times t i Are different from each other in width d of the heat affected zone edge i Changes occur with the welding time t.
Step two: at different temperatures T and different aging times T f Respectively carrying out thermal oxidation aging tests on each electric melting joint sample prepared in the step one, measuring the welding performance change coefficient P of each electric melting joint sample before and after aging, calculating the aging rate k of each electric melting joint sample at different temperatures T, and then obtaining the welding performance change coefficient P, the aging rate k and the aging time T of each electric melting joint sample through data fitting processing f And a relationship II between the aging rate k and the temperature T of each electrofusion joint specimen.
In the second step, specifically, the different temperatures T are all set at 80 ℃ or above, so as to shorten the time required by the aging test; preferably, the different temperatures T are set to 80 ℃, 95 ℃ and 110 ℃, respectively. In particular, the different aging times t f Set to 0h, 72h, 216h, 432h and 720h, respectively.
The second step specifically comprises: after the corresponding aging time tf, taking out each electric melting joint sample, respectively carrying out an extrusion stripping test, and measuring the brittle stripping percentage C of each electric melting joint sample C Calculating the welding performance change coefficient P of each electric melting joint sample before and after aging, wherein the calculation formula is as follows:
H C ＝(1-C C )×100 (1)
P＝H C /H C0 (2)
in the formula (1), C C Percent brittle peeling of electrofused joint specimen, H C The welding performance of the aged electric fusion joint sample is shown; in the formula (2), H C For the weldability of samples of electric fusion joints after ageing, H C0 The welding performance of the electrofusion joint sample before aging (i.e. the aging time is 0h) is shown.
Percent brittle Peel C C Calculated from the following formula:
in the formula, d is the brittle peeling length measured by a squeeze peeling test and has a unit of mm; s is the length of the wire measured in the pinch peel test in mm.
Welding performance change coefficient P, aging rate k and aging time t of each electric melting joint sample f The relationship I is obtained by adopting the following formula and performing data fitting treatment:
in the formula (3), A and alpha are material-related constants of the electric melting joint sample and are obtained by linear fitting; exp represents an exponential function with a natural constant e as the base.
The relation II between the aging rate k and the temperature T of each electric melting joint sample is obtained by adopting the following formula and performing data fitting treatment:
k＝Be -(E/RT) (4)
in the formula (4), R is a gas constant, E is reaction activation energy, and B is a constant, which are obtained by linear fitting; e is a natural constant.
Referring to fig. 4, which shows, by way of example, the trend of the change coefficient P of the welding performance with the increase of the aging time tf at temperatures of 80 c, 95 c and 110 c, respectively, of the electrofusion joint samples produced at a certain welding time, it can be seen that the higher the temperature, the faster the welding performance of the joint decreases, corresponding to the above formula (3).
Referring to fig. 5, the trend of the aging rate K with the temperature T of the obtained electric fusion joint sample at a certain welding time is shown, for example, in kelvin (K) corresponding to the above equation (4).
In the second step, the thermal oxidation aging test can refer to the standard GB/T71141-2008 & ltPlastic thermal aging test method'. The extrusion peeling test can refer to the extrusion peeling test of polyethylene electric melting components of plastic pipes and pipe fittings in GB/T19806-2005.
Step three: calculating the temperature T of the actual working condition according to the relation II obtained in the step two a Aging Rate k of lower electrofusion Joint test specimens i Coefficient of variation P of welding performance in combination with joint failure a And obtaining the temperature T of the actual working condition according to the relation I obtained in the step two a Aging time t required for each lower electrofusion joint sample to fail fi And finally obtaining the edge width d of the heat affected zone of the electric fusion joint of the polyethylene pipeline by combining the ultrasonic phased array detection result of the step I i And aging time t fi Corresponding relation d between i ～t fi 。
In the third step, the actual working condition is determined according to the actual common working condition of the in-service polyethylene pipeline electric melting joint to be evaluated, and is usually room temperature, and preferably, the temperature T of the actual working condition a The temperature was selected to be 20 ℃. According to the standard requirement, the welding performance variation coefficient P for determining joint failure a ＝0.67。
Step four: using the aforementioned evaluation system shown in FIG. 1, the corresponding relationship d established in the laboratory in step three is used i ～t fi Storing the model into data analysis software of a phased array host, and measuring the width d of the edge of a heat affected zone of the welding surface of an in-service buried polyethylene pipeline electric melting joint to be evaluated on site a D tested a The aging time is automatically calculated by data analysis software, namely the service life t corresponding to the in-service polyethylene pipeline electric melting joint fa 。
Under the working condition that the actual polyethylene pipeline electric melting joint operates, the general ambient temperature is 20 ℃. In the invention, the test temperature T gradient is set to be higher (for example, not less than 80 ℃) in the second step, so that the joint aging test time can be shortened. In order to improve the accuracy of the service life prediction result, the invention establishes a temperature gradient T epsilon (80 ℃, 95 ℃ and 110 ℃) aging test in the step two, establishes the corresponding relation between the joint aging rate k and the test temperature T through an Arrhenius extrapolation model according to the formula (4), and substitutes the temperature T of the actual working condition a The temperature T can be obtained a Aging Rate k of lower electrofusion Joint test specimens i Then aging rate k i And coefficient of variation P of welding performance at failure a The above equation (3) was substituted with 0.67 to obtain each electrofusion joint sample at the temperature T a Aging time t required for reaching failure correspondence fi I.e. equivalent to service life, thereby obtaining the characteristic line width d of the edge of the heat affected zone of each electrofusion joint sample prepared by different welding processes (different welding time t) i And its service life t fi Corresponding relation d between i ～t fi 。
The method can realize rapid and nondestructive prediction of the service life of the in-service buried polyethylene pipeline electric melting joint on site, overcomes the defects of long evaluation period, large engineering quantity and high cost of the existing evaluation method, and eliminates the complicated operations of destructive tests and the like required by the existing evaluation method.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Claims (10)
1. A nondestructive evaluation method for service life of an in-service polyethylene pipeline electric melting joint comprises the following steps:
the method comprises the steps of establishing a corresponding relation between the edge width of a heat affected zone of a welding area of the electric fusion joint of the polyethylene pipeline and the service life in a laboratory in advance;
carrying out ultrasonic phased array detection on an in-service polyethylene pipeline electric melting joint to be evaluated on site to obtain the width d of the edge of a heat affected zone of a welding area of the in-service polyethylene pipeline electric melting joint a ；
The width d of the heat affected zone edge a Substituting the obtained product into the corresponding relation to obtain the service life t of the in-service polyethylene pipeline electric melting joint fa 。
2. The method according to claim 1, wherein the previously establishing the correspondence between the heat affected zone edge width and the service life of the welded area of the electric fusion joint of the polyethylene pipeline in a laboratory comprises the following steps:
s1: respectively preparing polyethylene pipeline electric melting joint samples in batches according to different welding time t, and then respectively carrying out ultrasonic phased array detection on the prepared electric melting joint samples to obtain the width d of the edge of a heat affected zone of the welding area of each electric melting joint sample i (ii) a The different welding time t is set to enable the polyethylene pipeline electric melting joint to form a series of welding time from severe cold welding to severe over welding;
s2: at different temperatures T and different aging times T f Respectively carrying out thermal oxidation aging tests on each electric melting joint sample prepared in the step S1, measuring the welding performance change coefficient P of each electric melting joint sample before and after aging, calculating the aging rate k of each electric melting joint sample at different temperatures T, and then obtaining the welding performance change coefficient P, the aging rate k and the aging time T of each electric melting joint sample through data fitting processing f The relationship I between the samples, and the relationship II between the aging rate k and the temperature T of each electrofusion joint sample;
s3: calculating the temperature T of the actual working condition according to the relation II obtained in the step S2 a Aging Rate k of lower electrofusion Joint test specimens i And a coefficient of variation P of the welding performance combined with the identification of joint failure a Obtaining the temperature T of the actual working condition according to the relation I obtained in the step S2 a Corresponding to failure of lower electrically fused joint specimenService life t fi And finally obtaining the edge width d of the heat affected zone of the electric fusion joint of the polyethylene pipeline by combining the ultrasonic phased array detection result of the step S1 i And service life t fi Corresponding relation d between i ～t fi ；
In the method, the heat affected zone edge width d of the in-service polyethylene pipeline electric melting joint is measured a Substituting into the corresponding relation d of step S3 i ～t fi In the process, the service life t of the in-service polyethylene pipeline electric melting joint is obtained fa 。
3. The method of claim 2, wherein in step S1, the prepared polyethylene electric-fusion joint test sample has the same material grade as the in-service polyethylene electric-fusion joint to be evaluated.
4. The method according to claim 3, wherein in step S2, the different temperatures T are all set at 80 ℃ or above.
5. The method according to claim 4, wherein in step S2, the different temperatures T are set to 80 ℃, 95 ℃ and 110 ℃, respectively.
6. Method according to any of claims 2-5, wherein said different aging times t in step S2 f Set to 0h, 72h, 216h, 432h, 720h, respectively.
7. The method according to any one of claims 2-5, wherein step S2 further comprises: performing a squeezing and stripping test on each electric melting joint sample respectively, and measuring the brittle stripping percentage C of each electric melting joint sample C And calculating the welding performance change coefficient P of each electric melting joint sample before and after aging, wherein the calculation formula is as follows:
H C ＝(1-C C )×100 (1)
P＝H C /H C0 (2)
in the formula (1), C C Percent brittle peeling of electrofused joint specimen, H C The welding performance of the aged electric fusion joint sample is shown;
in the formula (2), H C For the weldability of samples of electric fusion joints after ageing, H C0 The electric fusion joint sample welding performance before aging is shown.
8. The method according to claim 7, wherein in step S2, the welding performance variation coefficient P, the aging rate k and the aging time t of each electrofusion joint sample f The relationship I is obtained by adopting the following formula and performing data fitting treatment:
in the formula (3), a and α are material-dependent constants of the electric fusion joint sample;
and (3) obtaining the relation II between the aging rate k and the temperature T of each electric melting joint sample by adopting the following formula and performing data fitting treatment:
k＝Be -(E/RT) (4)
in the formula (4), R is a gas constant, E is reaction activation energy, and B is a constant.
9. Method according to any of claims 2-5, characterized in that in step S3, the temperature T of the actual operating condition a The welding performance variation coefficient P for determining joint failure at room temperature a Is 0.67.
10. The evaluation system used in the method of claim 1, which comprises an ultrasonic self-focusing linear array probe and a host, wherein the ultrasonic self-focusing linear array probe is used for scanning an in-service polyethylene pipeline electric melting joint to be evaluated in the field; the host machine collects the ultrasonic phased array characteristic spectrum measured by the ultrasonic self-focusing linear array probe through a signal transmission line, and then calculates the electric melting characteristic spectrum of the in-service polyethylene pipeline by using data analysis softwareHeat affected zone edge width d of joint weld area a Finally, the width d of the heat affected zone edge is determined a Substituting the obtained product into the corresponding relation between the heat affected zone edge width and the service life which is established in a laboratory in advance to obtain the service life t of the in-service polyethylene pipeline electric melting joint fa 。
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