CN115014950A - Qualification evaluation method for mechanical properties of cable products - Google Patents
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Abstract
The invention discloses a method for evaluating the qualification of the mechanical property of a cable product, wherein the expression of a measurement result Y of the mechanical property of the cable is Y +/-U, wherein the Y mechanical property parameter is a measured value, namely the average value of multiple measurement data, U is the expansion uncertainty of the measured value, and the measurement result Y of the performance parameter is compared with a lower limit value [ Y ] or an upper limit value [ Y' ] specified in a standard so as to judge whether the cable product is qualified. The invention standardizes the mechanical performance of cable products and relates to the detection quality control and judgment rules of technical parameters, thereby meeting the technical index requirements and the use requirements of the technical standards of products.
Description
Technical Field
The invention relates to the technical field of wire and cable products, in particular to a qualification method for mechanical properties of a cable product.
Background
The cable product provides important supporting guarantee function in the major engineering and various fields of national construction, has high requirements on various technical performances when working under the condition of high voltage and large current for transmitting high-power electric energy in the power transmission and transformation engineering, and the mechanical performance of the wire and cable product is a key technical index for ensuring the quality of the wire and cable product. Therefore, the corresponding technical indexes of the mechanical performance of the cable must be tested and checked, so that the manufacturing and installation quality of the power cable is ensured, the operation accidents are reduced, and the power supply reliability is improved.
At present, various power cable products manufactured at home and abroad are largely used in the field of power transmission and transformation transmission, and because the country only has detection requirements and technical indexes for the cable products, no unified cable mechanical performance qualification standard exists, a specific method for evaluating the product mechanical performance qualification is lacked, and especially when a measurement result is close to a limit value of the technical requirements, the influence of a measurement error is not reasonably considered, so that the misjudgment on whether the cable products are qualified or not is caused, and the quality of the cable products is difficult to ensure. In order to ensure that the mechanical performance of a power cable product can meet the inspection technical requirements and the use requirements, key mechanical performance indexes influencing the product quality are effectively controlled, and the indexes can meet the index requirements of national standards and customer requirements at the same time, so that the misjudgment probability of mechanical performance measurement results is reduced, and the product detection qualified rate of the cable is effectively controlled. Therefore, it is necessary to provide a qualified assessment method for the mechanical performance index of the power cable product with unified specification.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for evaluating the mechanical property of a cable product.
In order to achieve the purpose, the invention adopts the following specific scheme:
the cable product mechanical performance qualification method includes that an expression of a cable mechanical performance measurement result Y is Y +/-U, wherein Y mechanical performance parameters are measured values, namely average values of multiple measurement data, and U is expansion uncertainty of the measured values. The performance parameter measurement result Y is compared with a limit value (lower limit value or upper limit value) specified in the standard, and is thereby judged as being acceptable.
Preferably, if the measurement criteria are given a lower limit value [ Y ]]If the mechanical performance parameter measurement result is qualified, the formula is: y-U y ≥[Y](ii) a Wherein y is the measured value of the mechanical property parameter, i.e. the average value of the measured data, U y For measuring uncertainty of measured value of mechanical property parameter, [ Y]The lower limit value of the maximum allowable error is given to the mechanical performance parameter.
Preferably, if given in the standard is an upper limit value [ Y']And the qualification judgment formula of the mechanical performance parameter measurement result is as follows: y + U y ≤[Y’](ii) a Where y is the measured value of the mechanical property parameter, i.e. the average of a number of measurements, U y Is the measured uncertainty, [ Y']The maximum allowable error upper limit value is given to the mechanical performance parameter.
Preferably, the mechanical property index parameter Y of the cable product can represent the tensile strength of the cable, the tensile strength after insulation aging, the change rate before and after insulation aging, and the change of elongation at break.
By adopting the technical scheme of the invention, the invention has the following beneficial effects: the mechanical performance of cable products is normalized, and the detection quality control and judgment rules of technical parameters are related, so that the technical index requirements and the use requirements of the technical standards of the products are met; according to the qualification evaluation of the mechanical performance index of the power cable by the method, the product misjudgment rate caused by the defects of the measurement evaluation method is effectively reduced, and the improvement of the product inspection quality is further ensured. The invention has been primarily applied to a detection technology mechanism and has better control effect.
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FIG. 1 is a schematic representation of a qualified evaluation of the mechanical properties of a cable with a given lower error limit in accordance with the present invention;
FIG. 2 is a schematic representation of the qualification of the mechanical properties of a cable for a given upper error limit of the present invention;
FIG. 3 is a schematic representation of the mechanical property index-tensile Strength qualification of the present invention;
FIG. 4 is a diagram illustrating the qualification of tensile strength change after insulation aging according to the present invention.
Wherein, the abscissa x is the measurement sequence, and the ordinate y represents the measurement parameters.
Detailed Description
The invention is further described below with reference to the following figures and specific examples.
Referring to fig. 1 and 2, a method for qualifying the mechanical properties of a cable product
(1) The qualification method for a given lower limit value comprises the following steps: if the measurement criteria are given by the lower limit value Y]If the mechanical performance parameter measurement result is qualified, the formula is: y-U y ≥[Y](ii) a Where y is the measured value of the mechanical property parameter, i.e. the average of a number of measurements, U y For measuring uncertainty of measured value of mechanical property parameter, [ Y]The lower limit value of the maximum allowable error is given to the mechanical performance parameter.
As shown in fig. 1: the situation of the measurement result (i) is in a qualified area, and the judgment is qualified; the situation spans between qualified and unqualified areas, and the situation cannot be clearly judged; and the situation of the measurement result is in an unqualified area, so that the judgment is unqualified.
In the mechanical performance indexes of the cable, the measurement result of the tensile strength parameter before insulation aging is sigma-U σ The qualification decision formula is expressed as follows:
σ-U σ ≥[σ]
wherein, sigma is the measured value of the tensile strength parameter before insulation aging;
U σ -a measurement uncertainty corresponding to the tensile strength measurement;
[ σ ] -lower value of allowable error for a given tensile strength parameter.
In the mechanical performance indexes of the cable, the measured value of the elongation at break parameter before insulation aging and the uncertainty of the measurement thereof form the measurement result delta-U of the elongation at break δ The qualification judgment formula is expressed as follows:δ-U δ ≥[δ]wherein, delta is a measured value of a breaking elongation parameter before insulation aging, U δ -measurement uncertainty corresponding to the elongation measurement, [ delta ]]-lower limit value of allowable error for given elongation at break.
(2) And (3) qualification method of the given upper limit value: if given in the standard is the upper limit value [ Y']And the qualification judgment formula of the mechanical performance parameter measurement result is as follows: y + U y ≤[Y’](ii) a Wherein y is the measured value of the mechanical property parameter, i.e. the average value of the measured data, U y Is the measured uncertainty, [ Y']And a maximum allowable error upper limit value is given to the mechanical performance parameter.
As shown in fig. 2, the measurement result (i) is qualified; the measurement result (II) cannot be determined; and measuring result and judging the condition to be unqualified.
In the cable mechanical performance indexes, the tensile strength change rate measurement result (f) is obtained by measuring the tensile strength change rate parameter measured value after insulation aging and the measurement uncertainty thereof σ +U f ) The qualification formula of (a) is expressed as: f. of σ +U f ≤[F’]Wherein f is σ Determination of the rate of change of tensile strength, usually the mean value of the measurements, U f -measurement uncertainty, [ F']-a given maximum allowable error upper limit value.
In the mechanical performance indexes of the cable, if the measured value of the elongation at break change rate parameter after insulation aging and the uncertainty of the measurement are obtained, the result of the change rate at break is measured (f) δ +U δ ) The qualification decision formula of (a) is expressed as: f. of δ +U δ ≤[F δ ′]Wherein f is δ The measured value of the rate of change of tensile strength, usually the mean value of the measurements, U δ -measurement uncertainty corresponding to the measured value of the rate of change, [ F ] δ ′]-a given maximum allowable error upper limit value.
The mechanical performance parameters such as the tensile strength of the cable, the tensile strength after insulation aging, the change rate before and after insulation aging, the change of the elongation at break and the like can be judged according to the method.
(3) In a special case, when the measurement result of the mechanical property is close to the required limit value, for example, when the measurement result reaches more than 80% of the given limit value, the measurement result may exceed the limit value of the corresponding index due to the influence of the uncertainty of the measurement, and at this time, the determination as qualified or unqualified is not made. The qualification can be made with a suitably reduced probability of measurement inclusion, with still little risk of false positives. If the conformity judgment can not be made clearly, a standard instrument with a higher precision grade is selected to be used, so that the expansion uncertainty U' of the measurement result is within 1/3 of the measurement uncertainty U of the original measuring instrument, and the conformity judgment can be made by further analysis after the secondary measurement.
Referring to fig. 3, taking the qualified assessment method of cable mechanical property-insulation tensile strength as an example, the qualified assessment of mechanical property belonging to the given lower limit requirement is as follows:
(1) in actual work, the mechanism measures the tensile strength of a cable sample by using an electronic tensile machine according to the specified method steps to obtain a tensile strength measured value sigma which is 14.2N/mm 2 The extended uncertainty U is 1.5N/mm 2 If the tensile strength of the cable is not less than the limit value [ sigma ] according to the requirement]＝12.5N/mm 2 And then the product is qualified. The conformity of the measurement results is determined as follows:
if the measured values are extended by an uncertainty downwards, the minimum tensile strength is obtained as:
σ min ＝σ-U＝14.2-1.5＝12.7N/mm 2 ＞[σ]＝12.5N/mm 2 ，
if the condition meets the specification requirement, the condition is judged to be qualified, such as the situation of (r) in fig. 3.
(2) For another cable wire sample, the tensile strength parameter was measured, also according to the specification, using an electric tensile machine, with a measurement σ of 13.9N/mm 2 When the calculation factor k is taken to be 2, the expansion uncertainty U is evaluated to be 1.5N/mm 2 Minimum limit of tensile strength requirement [ sigma ] of insulation]＝12.5N/mm 2 The following is determined for the conformity of the measurement results:
the minimum tensile strength is obtained after the tensile strength measurements are extended by the uncertainty: sigma min ＝σ-U＝13.9-1.5＝12.4N/mm 2 ＜[σ]＝12.5N/mm 2 ，
Due to the measurement result and its limit value [ sigma ]]If the difference is very close (more than 80% of the limit value), the difference does not meet the standard requirement, namely the difference cannot be definitely judged to be qualified, as shown in the case of the second in FIG. 3; if the calculation factor is appropriately reduced, e.g., k is 1.7, the estimated expansion uncertainty becomes U' 1.3N/mm 2 The measurement result after considering the extended uncertainty is:
σ min ＝σ-U’＝12.6N/mm 2 ＞[σ]＝12.5N/mm 2 ，
at this time, the qualification decision can be made definitely, as shown in the third case of fig. 3.
(3) The tensile strength of the third cable insulation sample was measured using an electronic tensile machine, and the value σ was 11.1N/mm 2 If the expansion uncertainty U' is 1.3N/mm 2 Minimum tensile Strength requirement [ sigma ]]＝12.5N/mm 2 The conformity of this measurement result is determined as follows:
the tensile strength maximum is obtained if the measurement results extend the uncertainty upwards:
σ max ＝σ+U’＝11.1+1.3＝12.4N/mm 2 ＜[σ]＝12.5N/mm 2 ，
a positive conclusion can be drawn that it is not qualified, as is the case in (r) of fig. 3.
Referring to fig. 4, the qualification method for the tensile strength change rate index after the cable insulation aging belongs to the qualification of mechanical properties required by a given upper limit.
(1) In actual work, the tensile strength change rate of a cable sample after insulation aging is measured by the detection mechanism, the tensile strength change rate of a three-core cable after insulation aging is respectively measured, and the measurement results corresponding to yellow, red and green wires are respectively as follows: 16%, 18%, 19%, evaluating to obtain an extended uncertainty U f 5 percent, if the tensile strength of the cable is changed after the insulation of the cable is aged according to the requirements of corresponding technical standardsThe rate is not greater than a limit value f']When the ratio is 25%, the product can be judged to be acceptable. The conformity of the measurement results is determined as follows:
if the measured value of the green line is extended by 19% upward uncertainty, the maximum value of the tensile strength change rate after insulation aging is obtained as follows:
f max ＝f σ +U f ＝19％+5％＝24％＜[f’]if the tensile strength change rate is 25%, the rate of change of the tensile strength of the yarn is judged to be acceptable, as shown in FIG. 4.
The tensile strength change rates of the yellow line and the red line are both smaller than the measured value of the green line, so that the tensile strength change rates of the yellow line and the red line can be qualified, and the index of the tensile strength change rate of the cable after insulation aging is qualified.
(2) The detection mechanism measures the change rate of the tensile strength of another cable sample after insulation aging, and respectively measures the measured values f of the change rates of the tensile strength of the yellow, red and green three-core cables after insulation aging σ Respectively as follows: 21%, 20%, 19%, evaluating the extended uncertainty U f 5%, if the tensile strength change rate after insulation aging is not more than the limit value f']When 25%, the measurement results were judged to be compatible as follows:
the measured values of the red line and the green line are not more than 20 percent, and after the uncertainty is expanded upwards, the maximum value of the tensile strength change rate after insulation aging is obtained as follows:
f max ＝f σ +U f ＝20％+5％＝25％＝[f’]then the two wire cores are judged to be qualified.
The measured value of the change rate of the tensile strength of the yellow line and the uncertainty of the measurement are the following measurement results:
f max ＝f σ +U f ＝21％+5％＝26％＞[f’]if so, the pass cannot be determined for the moment.
Further determination is required because the measurement result is close to the limit value. If the inclusion probability is reduced, the expanded uncertainty is reduced to be within 80% of the original value, even if U is less than 4%, and then the measurement result is:
f max ＝f σ +U f ＜21％+4％＝25％＝[f’]can be judged as qualified, as shown in FIG. 4②。
Therefore, the tensile strength change rate index of the cable after insulation aging can be also obtained to be qualified.
(3) Selecting another cable sample to measure the change rate of tensile strength after insulation aging, and respectively measuring the change rates of tensile strength of the yellow, red and green three-core cables after insulation aging to obtain a value f σ Respectively as follows: 32%, 29%, 31%, evaluation of extended uncertainty U f 5%, if the tensile strength change rate after insulation aging is not more than the limit value f']When 25%, the measurement results were judged to be compatible as follows:
the measured values of the tensile strength change rates of the three cables after insulation aging are all more than 25%, and the measured values of the green line and the yellow line are analyzed, so that the minimum value of the tensile strength change rates after edge aging after uncertainty measurement is considered as follows:
f min ＝f σ -U f ＝31％-5％＝26％＞[f’]then the two lines are judged as disqualified, as shown in the third of FIG. 4.
For a red line measurement of 29%, the minimum value of the tensile strength change rate after edge aging after taking into account the measurement uncertainty is:
f min ＝f σ -U f ＝29％-5％＝24％＜[f’]25%, but close to the limit value, so it cannot be directly used
And (6) judging. If the inclusion probability is reduced, the expanded uncertainty is reduced to be within 80 percent of the original value even if U is reduced f < 4%, when the measurement results are:
f min ＝f σ -U f ＞29％-4％＝25％＝[f’]therefore, it can be determined as a fail, as shown in the fourth part of FIG. 4.
Therefore, the index of the tensile strength change rate of the cable after insulation aging is unqualified.
For the qualified evaluation of the detection results of other mechanical performance parameter indexes of the cable, the corresponding evaluation method can be referred to according to the condition of the given upper limit or the given lower limit requirement.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (4)
1. A method for evaluating the mechanical performance of cable products is characterized in that the expression of the measurement result Y of the mechanical performance of the cable is Y +/-U, wherein the Y mechanical performance parameter is a measured value, namely the average value of multiple measurement data, U is the expansion uncertainty of the measured value, and the measurement result Y of the performance parameter is compared with a lower limit value or an upper limit value specified in a standard so as to judge whether the cable products are qualified.
2. A method for qualifying mechanical properties of cable products according to claim 1 characterised in that if the measurement criteria are given a lower limit value [ Y [ ]]And the qualification judgment formula of the mechanical performance parameter measurement result is as follows: y-U y ≥[Y](ii) a Where y is the measured value of the mechanical property parameter, i.e. the average of a number of measurements, U y For measuring uncertainty of measured value of mechanical property parameter, [ Y]The lower limit value of the maximum allowable error is given to the mechanical performance parameter.
3. Method for the qualification of the mechanical properties of cable products according to claim 1, characterized in that the upper limit value [ Y 'is given in the standard']And the qualification judgment formula of the mechanical performance parameter measurement result is as follows: y + U y ≤[Y’](ii) a Wherein y is the measured value of the mechanical property parameter, i.e. the average value of the measured data, U y Is the measured uncertainty, [ Y']The maximum allowable error upper limit value is given to the mechanical performance parameter.
4. The method of claim 1, wherein the mechanical property index parameter Y of the cable product is a tensile strength of the cable, a tensile strength after insulation aging, a change rate before and after insulation aging, and a change in elongation at break.
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| CN103869191A (en) * | 2014-03-17 | 2014-06-18 | 中国航空无线电电子研究所 | Aircraft electromagnetic environment safety margin assessment regulation method |
| WO2018090363A1 (en) * | 2016-11-21 | 2018-05-24 | 潘磊 | Method for testing aging resistance performance of paint of shipboard cable |
| CN110286303A (en) * | 2019-07-10 | 2019-09-27 | 国家电网有限公司 | A kind of coaxial cable insulation cable ageing state appraisal procedure based on BP neural network |
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