CN110940265A - Large strain correction measurement method applied to rapid loading acquisition system of static strength test - Google Patents
Large strain correction measurement method applied to rapid loading acquisition system of static strength test Download PDFInfo
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- CN110940265A CN110940265A CN201911218117.6A CN201911218117A CN110940265A CN 110940265 A CN110940265 A CN 110940265A CN 201911218117 A CN201911218117 A CN 201911218117A CN 110940265 A CN110940265 A CN 110940265A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
- G01B7/18—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in resistance
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- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
Abstract
The invention provides a large strain correction measurement method applied to a rapid loading acquisition system for a static strength test. The comparison result shows that the test precision of the invention is higher.
Description
Technical Field
The invention relates to the technical field of static strength tests, in particular to a large strain correction measurement method applied to a quick loading acquisition system of a static strength test.
Background
In the static strength test process, the strain parameters are main parameters for examining the test piece, so the measurement technology of the strain parameters of the test piece is particularly critical. At present, the industry mainly adopts a resistance strain gauge to measure the strain parameter of a test piece.
For an ideal resistance strain gauge, the resistance change rate of the resistance strain gauge is in direct proportion to the length change rate, the strain gauge is pasted on a test piece during measurement, and the length change rate of the resistance strain gauge is in direct proportion to the strain value of a structure test part. The resistance change rate and the strain relation of the resistance strain gauge are as follows:
generally called k is the sensitivity coefficient of the resistance strain gauge, and is provided by manufacturers; r is the strain gauge resistance, Δ R is the strain gauge resistance change, and ε is the strain. According to the formula (1), the strain magnitude of the strain gauge can be obtained by measuring the resistance change rate of the resistance strain gauge, and the test surface strain value of the test piece can be obtained. Fig. 1 shows a method for obtaining the resistance change rate of a strain gauge by using a universal bridge measurement method.
R1＝R+ΔR，R2＝R3＝R4＝R (2)
The output voltage of the voltage output bridge is:
as can be seen from (3), the output voltage of the measurement circuit and the rate of change of the resistance of the strain gauge are in a nonlinear relationship, and therefore the output voltage and the strain are also in a nonlinear relationship. In order to reduce the calculation error of strain measurement, at present, an instrument is generally calibrated according to actual measurement, and a curve relation between voltage and strain is given, so that the strain gauge is inconvenient to use and has poor universality. In addition, the testing precision of the static test of small strain can be ensured by adopting the curve relation, but when the strain is very large, particularly in a destructive working condition test, for example, when the strain is more than 10000, the precision of a strain value obtained by adopting the curve relation can not meet the requirement; furthermore, for dynamic strain measurements at high sampling rates (e.g., greater than 100kHz), the strain cannot be calculated by comparison using the curve relationship.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a large strain correction measurement method applied to a rapid loading acquisition system for a static strength test.
The technical scheme of the invention is as follows:
the large strain correction measurement method applied to the rapid loading acquisition system for the static strength test is characterized by comprising the following steps of: according to the formula
Calculating strain epsilon, wherein k is a design value of a sensitivity coefficient of the strain gauge, U is a power supply voltage of the measuring circuit, and delta Ug(RE)Is the actual measured output voltage reading; c is a correction coefficient considering the sensitive coefficient of the strain gauge and the influence of the long lead:
wherein k is(RE)The sensitivity coefficient of the actual strain gauge is obtained through calibration, R is the resistance of the strain gauge, R isLIs a wire resistance.
Advantageous effects
The large strain correction measurement method provided by the invention can be used for directly and accurately calculating according to the nonlinear relation between the voltage and the strain change, the large strain measurement calculation error can be effectively eliminated, and the comparison result shows that the measurement precision of the method is higher.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1: a schematic diagram of the resistance change rate of the strain gauge is measured by adopting a universal bridge;
FIG. 2: consider a plot of measured strain gage resistance change rate for a long wire.
Detailed Description
Because the output voltage and the strain of the existing measuring circuit are in a nonlinear relation, in order to reduce the calculation error of strain measurement, at present, instruments are generally calibrated according to actual measurement, and the curve relation of the voltage and the strain is given, so that the measuring circuit is inconvenient to use and has poor universality; moreover, the calculation by adopting the curve relation is only suitable for static test of small strain, and when the strain is very large, particularly in destructive working condition tests, for example, when the strain is more than 10000, the strain value precision obtained by adopting the curve relation can not meet the requirement; furthermore, for dynamic strain measurements at high sampling rates (e.g., greater than 100kHz), the strain cannot be calculated by comparison using the curve relationship.
Therefore, in the embodiment, through theoretical derivation, accurate calculation is directly performed according to the nonlinear relation between the voltage and the strain change, and the calculation error of large strain measurement can be effectively eliminated.
The formula (3) is transformed into the formula (1):
generally, strain gauges are designed according to the strain gauge sensitivity coefficient k being 2.20, while the strain gauge sensitivity coefficients of actual strain gauges are different and need to be calibrated once in advance to determine the actual strain gaugesSensitivity coefficient k of strain gauge(RE)And converting formula (1) to:
ε(RE)is the strain gauge reading.
According to the test circuit shown in FIG. 2, the wire resistance R is taken into accountLAnd the sensitivity coefficient of the strain gauge can be obtained
Get
C is a correction coefficient obtained by considering the sensitivity coefficient of the strain gauge and the influence of the long lead
ε＝C·ε(RE)(8)
And because of epsilon(RE)∝ΔUg(RE)Namely:
ΔUg＝C·ΔUg(RE)(9)
is obtainable from the formulae (4) and (9)
ΔUg(RE)Is the actual output voltage reading.
The strain calculation can be carried out by applying the formula (10), and the method is not limited by instruments and types of strain gauges and has high precision. The following table is a table comparing results of the method of the present invention and the conventional method, and it can be seen that the present invention has better precision.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.
Claims (1)
1. A large strain correction measurement method applied to a rapid loading acquisition system for a static strength test is characterized by comprising the following steps: according to the formula
Calculating strain epsilon, wherein k is a design value of a sensitivity coefficient of the strain gauge, U is a power supply voltage of the measuring circuit, and delta Ug(RE)Is the actual measured output voltage reading; c is a correction coefficient considering the sensitive coefficient of the strain gauge and the influence of the long lead:
wherein k is(RE)The sensitivity coefficient of the actual strain gauge is obtained through calibration, R is the resistance of the strain gauge, R isLIs a wire resistance.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114508995A (en) * | 2022-01-20 | 2022-05-17 | 中国航空工业集团公司北京长城计量测试技术研究所 | Step response characteristic calibration device and method of resistance strain measuring instrument |
| CN114526851A (en) * | 2022-04-25 | 2022-05-24 | 中国飞机强度研究所 | Method for measuring thermal stress of metal-composite material mixed structure for airplane |
| CN114719734A (en) * | 2022-02-25 | 2022-07-08 | 中国科学院武汉岩土力学研究所 | Strain value correction method under condition of arrangement deviation of precision diaphragm strain element |
-
2019
- 2019-12-03 CN CN201911218117.6A patent/CN110940265A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114508995A (en) * | 2022-01-20 | 2022-05-17 | 中国航空工业集团公司北京长城计量测试技术研究所 | Step response characteristic calibration device and method of resistance strain measuring instrument |
| CN114719734A (en) * | 2022-02-25 | 2022-07-08 | 中国科学院武汉岩土力学研究所 | Strain value correction method under condition of arrangement deviation of precision diaphragm strain element |
| CN114526851A (en) * | 2022-04-25 | 2022-05-24 | 中国飞机强度研究所 | Method for measuring thermal stress of metal-composite material mixed structure for airplane |
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