Device and method for measuring volume expansion characteristics of material under tensile load

A technology of volume expansion and measuring device, applied in the direction of measuring device, analyzing material, strength characteristics, etc., can solve the problems of inability to accurately determine the time and displacement point of sample stretching, and it is difficult to ensure the volume compensation rod, so as to ensure the measurement Traceability, ensure accuracy, and avoid the effect of gas state changes

Pending Publication Date: 2020-05-26
西安航天三沃机电设备有限责任公司
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AI-Extracted Technical Summary

Problems solved by technology

[0006] In the above-mentioned gas dilatometer/measuring device, there are the following problems: First, a key prerequisite for effective and reliable measurement is that the relationship between the gas volume change and the differential pressure change obtained by using the volume calibration system is calibrated. - When the amount of gas substance in the combined cavity of the compensation cavity remains unchanged, it can continue to be established during the measurement process, and then used to convert the volume change from the differential pressure measurement result
However, in the process of opening the test chamber and the sample chamber, replacing the calibration steel rod with the material sample to be tested, and then sealing the sample chamber and the test chamber, it is impossibl...
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Abstract

The invention discloses a device and a method for measuring the volume expansion characteristic of a material under a tensile load. The device comprises a stretching rod, a compensation rod, a reference cavity, a differential pressure gauge and a micrometer caliper. Screws of the stretching rod, the compensation rod and the micrometer caliper respectively extend into a test cavity through specificmounting seats, the stretching rod and the compensation rod are the same in material size specification and are fixedly connected in the test cavity, and the moving directions are opposite in the stretching process. The measurement process is divided into three stages of background curve measurement, total curve measurement and data comprehensive processing. In the background curve determinationstage, a background curve representing the relationship between volume change data and displacement data caused by device factors in the stretching process is obtained through calibration and stretching test under the condition of no sample; in the total curve determination stage, a total curve representing the relationship between total volume change data and displacement data in the stretching process is obtained through calibration and stretching test after sample installation; in the data comprehensive processing stage, the inflection point of the force curve is used for determining starting point displacement in the stretching process, and a volume expansion characteristic curve is obtained in combination with the background curve and the total curve.

Application Domain

Technology Topic

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  • Device and method for measuring volume expansion characteristics of material under tensile load
  • Device and method for measuring volume expansion characteristics of material under tensile load
  • Device and method for measuring volume expansion characteristics of material under tensile load

Examples

  • Experimental program(1)

Example Embodiment

[0030] like figure 1 As shown in the figure, a measuring device for the volume expansion characteristics of materials under tensile load is characterized by comprising a platform 1, which is installed on the base 3 of the tensile testing machine through a support column 2, and a test cavity 4 and a reference cavity 5 are fixed on the platform 1. , the mounting seat 25, the force sensor 8, and the upper fixture 10 are fixed on the top of the test chamber 4 in sequence from top to bottom. The upper end of the tension rod 13 and the lower end of the compensation rod 14 are connected and fixed. The tension rod 13 passes through the test cavity 4 through the tension rod mounting seat 15, and its lower end is connected and fixed with the tensile test motorized beam 16. The displacement sensor 17 on the compensating rod 14 passes through the test cavity 4 through the compensating rod mounting seat 18; the screw micrometer 19 is fixed outside the test cavity 4 through the screw micrometer mounting seat 20. The screw 21 extends into the test chamber 4; the reference chamber 5 is provided with a pressure adjustment interface 22; the test chamber 4 and the reference chamber 5 are respectively provided with a first air pressure interface 23 and a second air pressure interface 24, and the first air pressure interface 23 and the second air pressure interface 24 communicates with the positive and negative pressure measuring ports of the differential pressure gauge 9 through the first pressure-inducing pipe 6 and the second pressure-inducing pipe 7 respectively.
[0031] like figure 2 , image 3 As shown, the measurement process includes three stages: background curve determination, total curve determination, and data comprehensive processing;
[0032]In the background curve determination stage, through the calibration and tensile test under the condition of no sample, the background curve representing the relationship between the volume change data and the displacement data caused by the measurement device factor during the stretching process is obtained, such as Image 6;
[0033] In the overall curve determination stage, through the calibration and tensile test after installing the sample, the overall curve representing the relationship between the total volume change data and the displacement data during the stretching process is obtained, such as Figure 7;
[0034] In the data synthesis processing stage, the inflection point of the force curve is used to determine the starting point displacement of the stretching process, and the volume expansion characteristic curve is obtained by combining the background curve and the total curve, such as Figure 8.
[0035] The specific measurement steps are as follows:
[0036] Step 1: According to typical sample size and shape of the material to be tested (e.g. Figure 4 ), prepare matching fixtures, tension rods 13 and compensating rods 14, and then prepare a test cavity 4. Under the premise of ensuring the installation of the above-mentioned components and the material sample 11 to be tested, the cavity door should meet the requirements of easy disassembly and assembly. According to the requirements, after the cavity door is installed, the airtight requirements under normal temperature and pressure should be ensured, and the pressure-inducing interface should be provided, as well as the screw micrometer mounting seat 20, the tension rod mounting seat 15 and the compensation rod mounting seat 18 with built-in airtight structure, Select the matching helical micrometer 19.
[0037] A reference cavity 5 is prepared, the inner cavity volume of which is similar to that of the test cavity 4 after the sample is installed, and a pressure-inducing interface is provided.
[0038] Step 2: Using the verified measuring tool, measure the initial volume of the material sample 11 to be tested, the initial length in the stretching direction, and the diameter of the screw 21;
[0039] Step 3: Connect the test chamber 4 and the reference chamber 5 with the positive and negative pressure measuring ports of the differential pressure gauge 9 through the first pressure-inducing tube 6 and the second pressure-inducing tube 7 respectively; install the screw on the screw micrometer mounting seat 20 Micrometer 19, confirm that the screw 21 can enter and exit the screw micrometer mounting seat 20 relatively smoothly, and meet the airtight requirements under normal temperature and pressure; install the stretching rod 13 on the stretching rod mounting seat 15, confirm that the stretching rod 13 can be relatively The dynamic seal structure can enter and exit smoothly, and meet the airtight requirements under normal temperature and pressure; install the compensating rod 14 on the compensating rod mounting seat 18 to confirm that the compensating rod 14 can enter and exit the dynamic sealing structure relatively smoothly, and meet the airtight requirements under normal temperature and pressure;
[0040] Step 4: Connect the upper clamp 10 to the top of the test chamber 4, connect the lower clamp 12 to the tensile rod 13 and the compensation rod 14, operate the tensile testing machine, and make the lower clamp 12 stop at the position after the sample is bonded, It is allowed to be upward; confirm that the differential pressure gauge 9 and the displacement sensor 17 are working normally;
[0041] Step 5: Seal the test cavity 4 and the reference cavity 5, change the length of the screw 21 extending into the test cavity 4 several times within the range of the screw micrometer 19, record the length change and the reading change of the differential pressure gauge 9, and then Obtain the conversion relationship A between the change of the gas volume in the cavity and the change of the differential pressure under the condition of no sample 1 ( Figure 5 );
[0042] Step 6: Start stretching to the lower limit according to the test parameters, simultaneously record the displacement data and differential pressure data during the stretching process, convert the differential pressure data into volume change, and draw a displacement-volume change curve, which is the device influence Background curve C of factors causing volume changes during stretching 1;
[0043] Step 7: Adhere the upper and lower fixtures 10 and 12 to both ends of the material sample 11 to be tested, and confirm that they have sufficient bonding strength; install the material sample 11 to be tested in the test cavity 4, and seal the test cavity 4;
[0044] Step 8: Change the length of the screw 21 extending into the test cavity 4 several times within the range of the screw micrometer 19, record the length change and the reading change of the differential pressure gauge 9, and then obtain the cavity under the condition of installing the sample. Conversion relationship between gas volume change and differential pressure change A 2;
[0045] Step 9: Adjust the screw 21 back to the position before step 8, start the tensile test, and collect the force, differential pressure, displacement and other data during the stretching process simultaneously; after the material sample 11 to be tested is broken, stop stretching and data collection;
[0046] Step 10: Use Conversion A obtained in Step 8 2 , convert the differential pressure data in step 5 into volume change data, and draw the displacement-total volume change curve C 2;
[0047] Step 11: Compare Curve C 1 and curve C 2 , combined with the data of the force sensor 8 to determine the displacement of the sample at the beginning of the force, and draw the volume expansion characteristic curve of the material under the tensile load;
[0048] It should be noted that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still The technical solutions described in the foregoing embodiments are modified, or some technical features thereof are equivalently replaced.
[0049] Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
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