CN103822754B - A kind of compressive stress generating means for stress measurement system calibration - Google Patents

Abstract

The invention designs a compressive stress generating device used for calibrating a stress measurement system. The device has the characteristics of simple structure, beautiful appearance and convenient use. By tightening the bolts at both ends, a load is applied to the elastic element, so that a certain compressive stress is generated in the calibration area of the elastic compressive stress generating element. Then use the ultrasonic stress detection system to measure the compressive stress value in the calibration area on the elastic compressive stress generating element. The section length and width are calculated and used as standard compressive stress values. The annular load cell and the geometric measuring instrument are calibrated and traceable, which can prove that the compressive stress value generated by the compressive stress generating device has traceability and high accuracy. The accuracy of the ultrasonic stress detection system for compressive stress measurement is evaluated and calibrated by comparing the deviation between the measured value and the standard compressive stress value.

Description

A compressive stress generating device for calibration of stress measurement system

1. Technical field

The invention relates to a compressive stress generating device for calibrating a stress measuring system, which is suitable for evaluating and calibrating the compressive stress measuring performance of an ultrasonic stress detecting system.

2. Background technology

With the development of non-destructive testing technology for structural stress of materials, ultrasonic stress measurement technology has become one of the main testing methods. Especially the ultrasonic critical refraction longitudinal wave method has a very broad prospect.

Any kind of detection device has its specific accuracy, and requires a corresponding calibrator to evaluate and calibrate its detection results. Acoustoelasticity theory shows that ultrasonic method measures relative stress value, and only by calibrating it with corresponding calibrator can the real absolute stress value be obtained. Therefore, designing a standard compressive stress generating device for the evaluation and calibration of the measurement performance of the ultrasonic stress-free testing system is of great significance to ensure the traceability and accuracy of the compressive stress values measured by the ultrasonic stress testing system.

3. Contents of the invention

The purpose of the present invention is to provide a compressive stress generating device for calibrating a stress measurement system, which has the characteristics of simple structure, beautiful appearance and small volume.

The purpose of the present invention is achieved by making the elastic compressive stress generating element with the material to be tested, tightening two bolts from both ends of the device, so that the calibration area on the elastic compressive stress generating element generates compressive stress, and the ring load cell Measure the pressure acting on the elastic compressive stress generating element, then measure the cross-sectional length and width of the calibration area on the elastic compressive stress generating element, and calculate the compressive stress value in the calibration area on the elastic compressive stress generating element through the formula. The ring force sensor for force and the length measuring instrument for measuring the cross section of the elastic element can be calibrated and traced in advance. Therefore, the calculated compressive stress value can be used as the standard value of compressive stress, and then the ultrasonic stress detection system is used to calibrate the elastic compressive stress generating element. The compressive stress value in the area is measured, and the accuracy of the compressive stress measurement of the ultrasonic stress detection system is evaluated and calibrated by comparing with the calculated results.

4. Description of drawings

Fig. 1 assembly drawing of compressive stress generating device;

Fig. 2 Schematic diagram of the ultrasonic stress testing system measuring the compressive stress of the calibration area on the elastic compressive stress generating element.

The reference signs are explained as follows:

Figure 1: Bolt 1, Washer 2, Ring load cell 3, Elastic compressive stress generating element 4, Nut 5, Bolt 6

Figure 2: Sensor 7 and elastic compressive stress generating element 4 of the ultrasonic stress detection system

5. Specific implementation

The specific embodiment of the present invention is described in detail below:

1. Generation and calculation of compressive stress in the calibration area of the elastic compressive stress generating element

(1) Generation and calculation principle of compressive stress in the calibration area of the elastic compressive stress generating element

As shown in Figure 1, the washer 2, the annular load cell 3, and the elastic compressive stress generating element 4 are placed concentrically from top to bottom, the nut 5 is placed inside the elastic compressive stress generating element, and the two bolts 1 and 6 are connected from the two sides of the device. The end is screwed into the nut 5, so that the calibration area on the elastic compressive stress generating element can generate compressive stress. The compressive stress value is calculated by measuring the pressure value and the cross-sectional area of the elastic element. The pressure acting on the elastic element is measured by a ring load cell, and the cross-section of the calibration area on the elastic compressive stress generating element is measured by a geometric measuring instrument. length and width, the compressive stress generated by the calibration area on the elastic compressive stress generating element can be calculated according to the following formula:

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; bc</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; bh</span>}}$

Among them, F is the pressure value acting on the elastic element measured by the ring load cell

A is the cross-sectional area of the calibration area on the elastic compressive stress generating element

b is the width of the cross-section of the calibration area on the elastic compressive stress generating element

h is the length of the cross-section of the calibration area on the elastic compressive stress generating element.

(2) Explanation of the accuracy of the calculation results of the compressive stress in the calibration area on the elastic compressive stress generating element

Because of the pressure value F acting on the calibration area on the elastic compressive stress generating element, the width b of the calibration area cross-sectional area on the elastic compressive stress generating element, and the length h of the calibration area cross-sectional area on the elastic compressive stress generating element, the three values It has good traceability, so the accuracy of the results calculated by the formula is guaranteed, that is, the compressive stress value σ _bc calculated by the formula has high precision.

2. Compressive stress calibration method of ultrasonic stress testing system

As shown in Figure 2, when the pressure value F measured by the annular load cell 3 is stable, that is, after the pressure in the calibration area on the elastic compressive stress generating element is stable, the sensor 7 of the ultrasonic stress detection system that needs to be calibrated is placed on the elastic compressive stress. In the calibration area on the stress generating element, the compressive stress of the calibration area on the elastic compressive stress generating element is measured.

Comparing the compressive stress results measured by the ultrasonic stress detection system with the calculation results of the formula, the deviation of the measured value can be obtained, which can evaluate the measurement accuracy of the compressive stress of the ultrasonic stress detection system or provide a basis for its adjustment and guarantee.

By controlling the amount of rotation of the bolts 1 and 6 at both ends, different pressures can be applied to the elastic element, so the standard compressive stress generating device designed by the present invention can be used to measure the accuracy of the ultrasonic stress detection system under multiple compressive stress values. Fully calibrated.

3. Processing instructions for the two bolts 1 and 6

As shown in Figure 1, the upper and lower bolts 1 and 6 are made of A-level hexagon socket head screws with thread specification D≥M48, performance level ≥10.9, and surface oxidation. The diameter of the cylindrical head is D1≥72mm. During processing, the external thread of the bolt is processed into a thread specification D2≥24mm according to the method specified in the national standard, and the performance level is guaranteed to remain unchanged.

The reason why the two bolts 1 and 6 are made of hexagon socket head cap screws is for the sake of appearance, and the bolts with thread specification D≥M48 are selected because the diameter of the cylindrical head is large, which can ensure that the elastic compressive stress generating elements are evenly stressed.

4. Instructions for making the elastic compressive stress generating element 4

As shown in Figure 2, the elastic compressive stress generating element 4 is composed of two upper and lower rings and four rectangular columns in the middle. The main function of the rings is to increase the stability of the elastic compressive stress generating element 4 and increase the elastic compression The contact area between the stress generating element 4 and the annular force sensor 3 and the lower nut 6 reduces the compressive stress loads borne by the annular force sensor 3 and the nut 6 under the same pressure.

The material used for the elastic compressive stress generating element 4 should be consistent with that of the component or structure to be tested.

The height H of the elastic compressive stress generating element 4 ranges from 100 to 130 mm, and the thickness of the upper and lower rings ranges from 10 to 20 mm. The specific value can be determined according to the sensor spacing of the ultrasonic stress detection system, and it is only necessary to ensure that it does not lose stability.

The calibration area of the elastic compressive stress generating element 4 is on the four rectangular columns, and the surface must be free from scratches, pits, burrs and other defects during processing. The surface roughness of its calibration area is Ra≤1.6. In this way, the sensor 7 of the ultrasonic stress detection system can be better coupled with the calibration area, and the calibration accuracy can be improved.

The cross-sectional area of the four rectangular columns in the calibration area of the elastic compressive stress generating element 4 should be within 400mm2 to ensure that the bolts can withstand the corresponding compressive stress load. The specific length and width of the cross-section can be determined according to the sensor width of the ultrasonic stress detection system It depends on the actual situation.

Corresponding rounds should be processed between the two circular rings of the elastic compressive stress generating element 4 and the four rectangular columns to ensure smooth transition and prevent concentrated stress.

The elastic compressive stress generating element 4 also needs corresponding heat treatment after processing to eliminate the stress generated during the processing.

5. Function of gasket 2

As shown in Figure 1, the washer 2 is mainly used to protect the annular force sensor 3, and prevent the relative sliding between the annular washer sensor 3 and the bolt 1 from damaging the annular force sensor 3, so the two sides of the washer 2 must ensure that the surface roughness Ra≤ 3.2.

6. As shown in Figure 2, in order to ensure that the load can be completely transmitted to the calibration area of the elastic element, the bolt 1, the washer 2, the ring load cell 3, the elastic compressive stress generating element 4, the nut 5 and the bolt 6 should be concentrically aligned.

Claims (8)

1. the compressive stress generating means for stress measurement system calibration, it is characterized in that: it comprises bolt, nut, toroid load cell, packing ring, elasticity compressive stress generating device, it is inner that nut is put in elasticity compressive stress generating device, two bolts are contained in the two ends of device, rotate the bolt at two ends, make flexible member stressed generation definite value compressive stress, by ultrasonic stress mornitoring system, the value of compressive stress in calibration region on elasticity compressive stress generating device is measured, carry out contrasting the accuracy assessed with calibrating ultrasonic stress mornitoring system and measuring compressive stress by the standard value of compressive stress occurred with device.

2. a kind of compressive stress generating means for stress measurement system calibration according to claim 1, its feature of standard value of compressive stress occurred is: the value of compressive stress that device produces is by the flexible member force value measured with toroid load cell and draw with the flexible member Size calculation that geometric measurement instrument is measured, because toroid load cell and geometric measurement instrument are easily calibrated, so the value of compressive stress that this device occurs has trace back originality and higher accuracy, can be used as standard value of compressive stress and use.

3. a kind of compressive stress generating means for stress measurement system calibration according to claim 1, its elasticity compressive stress generating device is characterised in that: the material of device Elastic compressive stress generating device is identical with the material of the component that the ultrasonic stress mornitoring system be calibrated will detect or structure, can meet the constraint that in ultrasonic stress mornitoring system, sonic elastic modulus is relevant to material category.

4. a kind of compressive stress generating means for stress measurement system calibration according to claim 1, its elasticity compressive stress generating device is characterised in that: two circular ring structures up and down of flexible member and four rectangular columns can increase the stability of elasticity compressive stress generating device.

5. a kind of compressive stress generating means for stress measurement system calibration according to claim 1, its elasticity compressive stress generating device is characterised in that: the sensor four rectangular columns of elasticity compressive stress generating device all can being placed ultrasonic stress mornitoring system, to measure the value of compressive stress in calibration region on elasticity compressive stress generating device.

6. a kind of compressive stress generating means for stress measurement system calibration according to claim 1, its elasticity compressive stress generating device is characterised in that: adding man-hour, the structure that two annulus of elasticity compressive stress generating device are connected with four rectangular columns has rounding, can prevent stress from concentrating.

7. a kind of compressive stress generating means for stress measurement system calibration according to claim 1, its elasticity compressive stress generating device is characterised in that: it is separated with the bolt of lower end, can make separately.

8. a kind of compressive stress generating means for stress measurement system calibration according to claim 1, it rotates the bolt at two ends, flexible member stressed generation definite value compressive stress is characterised in that: by controlling the rotation amount of bolts at two ends, different pressure can be applied to flexible member, thus in the elastic range of flexible member material, general calibration can be carried out to ultrasonic stress mornitoring systematic survey accuracy under multiple standard value of compressive stress.