A method for measuring deformation and displacement of high-temperature tensile test specimens

Abstract

A method for measuring the deformation displacement of a high-temperature tensile test specimen belongs to the field of experimental mechanics high-temperature testing technology, and solves the problem of electronic components being unable to withstand high temperatures and having low precision in deformation displacement measurement in high-temperature environments. The method of the present invention is implemented through a high-temperature displacement measurement module, a normal-temperature displacement measurement module, and a connection module. A pair of high-temperature resistant sliders are provided in the high-temperature box, each connected to a retractable high-temperature contact, and can slide along a guide rod parallel to the axis of the specimen; each slider is staggeredly connected to the lower and upper normal-temperature sliders on the same axis outside the high-temperature box through a high-temperature resistant and inelastic silk thread, converting the high-temperature environment displacement to a normal-temperature environment; then, the dynamic relative displacement of the two normal-temperature sliders is measured by a normal-temperature extensometer and introduced into the tensile test system. The method of the present invention breaks through the limitations of high-temperature environments on electronic components for displacement measurement, has the characteristics of a wide range of applications, high measurement precision, and low cost, and is suitable for deformation displacement measurement in metal tensile tests over a large temperature range.

Description

Technical Field

[0001] The invention relates to an experimental mechanics high-temperature testing technology, and in particular to a method for measuring the deformation and displacement of a high-temperature tensile test specimen. Background Art

[0002] With the increasing demand for energy conservation in the environment and the increasing demand for endurance in electric vehicles, lightweight vehicles are the general trend of future automotive development and have great development potential. The forming of various lightweight materials such as high-strength automotive steel, aluminum alloys, and magnesium alloys has become a current technical hotspot. These materials are often difficult to form at room temperature, but have good forming properties under heating conditions. High-temperature mechanical properties are the basis and necessary conditions for the design and simulation analysis of high-temperature forming processes of materials. High-temperature tensile testing is one of the most commonly used methods for testing the high-temperature mechanical properties of metal materials. It is usually carried out in a closed high-temperature box equipped with a testing machine. There are two types of deformation and displacement measurement methods combined with the experimental system: contact and non-contact. The contact method mainly uses direct measurement with an extensometer, while the non-contact method uses digital image correlation technology for measurement.

[0003] Compared with normal temperature, high-temperature tensile testing has certain particularities: First, ordinary extensometers cannot be used to measure deformation displacement in high-temperature environments, and special high-temperature extensometers are required. However, high-temperature extensometers have a small applicable temperature range and are expensive; second, digital image correlation technology is used to measure high-temperature deformation displacement, and the existence of thermal air flow disturbances in high-temperature environments has a greater impact on measurement accuracy.

[0004] To address this issue, several specialized fixtures for warm-forming tensile testing have been developed. For example, Shenzhen Xinsansi Materials Testing Co., Ltd. has developed a hot-forming tensile testing fixture that can extract displacement from a heating furnace. However, when the specimen strain is high, the protrusion at the gauge length in the middle of the tensile specimen is easily deformed by the pull of a lead-out rod, thereby reducing the accuracy of displacement measurement. CN 101608988 discloses a fixture for warm-forming unidirectional tensile testing of metal sheets. This fixture uses a displacement lead-out rod to extract and measure deformation displacement in a high-temperature environment. However, two issues need to be addressed: first, the tension adjustment significantly affects measurement accuracy; second, the lead-out rod is large, which can easily cause uneven temperature distribution at the outlet. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of the existing technology for measuring deformation displacement in high-temperature tensile tests, such as a small operating temperature range, low measurement accuracy and high cost. A method for measuring the deformation displacement of a high-temperature tensile test specimen is provided. The deformation displacement in a high-temperature environment is transferred to a room temperature environment through a high-temperature resistant wire and then measured using a room-temperature extensometer. This method improves the temperature application range and measurement accuracy, and greatly reduces costs.

[0006] The present invention is implemented by adopting the following technical solutions: a method for measuring the deformation displacement of a high-temperature tensile test specimen, firstly leading out the high-temperature deformation displacement through a high-temperature slider, connecting it to two normal-temperature sliders with a high-temperature resistant silk thread, and then using a normal-temperature extensometer to measure the relative displacement between the two normal-temperature sliders, and then collecting the displacement signal and importing it into the tensile test system.

[0007] Furthermore, the method specifically comprises the following steps:

[0008] Step 1: Install the high-temperature displacement measurement module 2. Install the specimen 23 between the upper high-temperature chuck 211 and the lower high-temperature chuck 212 in the high-temperature box 1. Place the upper high-temperature slider 261 and the lower high-temperature slider 262 on the high-temperature guide rod 27. The high-temperature guide rod 27 is installed between the upper fixed end 241 of the high-temperature bracket and the lower fixed end 242 of the high-temperature bracket. The upper high-temperature slider 261 is connected to the upper fixed end 241 of the high-temperature bracket through the upper high-temperature spring 251, and the lower high-temperature slider 262 is connected to the lower fixed end 242 of the high-temperature bracket through the lower high-temperature spring 252. The upper high-temperature contact 221 and the lower high-temperature contact 222 are fixedly installed on the upper high-temperature slider 261 and the lower high-temperature slider 262 respectively. The contacts are in contact with the surface of the specimen 23 to ensure a certain contact force.

[0009] Step 2: Install the normal-temperature displacement measurement module 5. Place the upper normal-temperature slider 521 and the lower normal-temperature slider 522 on the normal-temperature guide rod 53 so that they can slide up and down. The normal-temperature guide rod 53 is fixedly installed between the upper fixed end 511 of the normal-temperature support and the lower fixed end 512 of the normal-temperature support. The axis of the normal-temperature guide rod 53 must be parallel to the axis of the specimen 23. The upper normal-temperature slider 521 is connected to the upper fixed end 511 of the normal-temperature support via an upper normal-temperature spring 541, and the lower normal-temperature slider 522 is connected to the lower fixed end 512 of the normal-temperature support via a lower normal-temperature spring 542.

[0010] Step 3: Connect the high-temperature displacement measurement module 2 and the normal-temperature displacement measurement module 5, and stagger the upper high-temperature slider 261 and the lower high-temperature slider 262 with the lower normal-temperature slider 522 and the upper normal-temperature slider 521 through the upper high-temperature resistant wire 31 and the lower high-temperature resistant wire 32, respectively.

[0011] Step 4: System balance adjustment: rotate the upper tensioning wheel 41 and the lower tensioning wheel 42 respectively to tension the upper high-temperature resistant wire 31 and the lower high-temperature resistant wire 32; adjust the upper high-temperature spring 251 and the lower normal temperature spring 542 to balance the upper high-temperature slider 261 and the lower normal temperature slider 522; adjust the lower high-temperature spring 252 and the upper normal temperature spring 541 to balance the lower high-temperature slider 262 and the upper normal temperature slider 521;

[0012] Step 5: The upper extensometer contact 611 and the lower extensometer contact 612 of the room temperature extensometer 6 are respectively in contact with the upper room temperature slider 521 and the lower room temperature slider 522; the room temperature extensometer 6 collects displacement signals and imports them into the tensile test system to complete the deformation displacement measurement.

[0013] Furthermore, the installation of the test piece 23 in step 1 requires that the axis of the test piece 23 is consistent with the stretching direction; the installation of the high-temperature guide rod 27 in step 1 requires that the axis of the high-temperature guide rod 27 is parallel to the axis of the test piece 23;

[0014] As a preferred solution, in step 1, the upper high-temperature contact 221 and the lower high-temperature contact 222 are brought into contact with the test piece 23 to ensure a certain contact force, and can be bound to the test piece 23 through a high-temperature resistant spring.

[0015] Furthermore, the equilibrium state in step 4 means that a small force is applied to the upper high-temperature slider 261, and the upper high-temperature slider 261 and the lower normal-temperature slider 522 can move the same small displacement.

[0016] As a preferred solution, in step 4, the upper high-temperature resistant wire 31 and the lower high-temperature resistant wire 32 are tensioned, and the tensioning force is 10N.

[0017] As a preferred solution, the extensometer upper contact 611 and the extensometer lower contact 612 in step 4 are in contact with the upper normal temperature slider 521 and the lower normal temperature slider 522 respectively, and are tied with rubber bands to generate a certain contact pressure.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) By converting the displacement in a high-temperature environment to a normal-temperature environment for measurement, the present invention overcomes the influence of the high-temperature environment on electronic components, expands the applicable temperature range, improves the measurement accuracy, and reduces the cost compared with the traditional displacement measurement method.

[0020] (2) The present invention uses high-temperature resistant wire to connect the high-temperature displacement measurement module and the normal-temperature displacement measurement module. It has no special requirements on the size of the lead-out hole of the high-temperature box and can match most high-temperature boxes, with a wide range of applications.

[0021] (3) The high-temperature slider and the normal-temperature slider of the present invention are respectively connected to the corresponding fixed ends through springs, and a tensioning wheel is used to tension the wire for balance adjustment, thereby eliminating the influence of external resistance on displacement changes and significantly improving the displacement measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the principle of converting deformation displacement in a high-temperature environment to measurement in a normal-temperature environment according to the present invention.

[0023] Figure 2 for Figure 1 A scaled-up view of the displacement measurement module for medium and high temperature environments.

[0024] Figure 3 for Figure 1 A scaled-up view of the displacement measurement module in a medium-normal temperature environment.

[0025] Description of Reference Numerals

[0026] 1—High temperature box, 2—High temperature displacement measurement module, 211—Upper high temperature chuck, 212—Lower high temperature chuck, 221—Upper high temperature contact, 222—Lower high temperature contact, 23—Test piece, 241—Upper fixed end of high temperature bracket, 242—Lower fixed end of high temperature bracket, 251—Upper high temperature spring, 252—Lower high temperature spring, 261—Upper high temperature slider, 262—Lower high temperature slider, 27—High temperature guide rod; 31—Upper high temperature resistant Wire, 32—lower high temperature resistant wire, 41—upper tensioning pulley, 42—lower tensioning pulley, 5—normal temperature displacement measurement module, 511—upper fixed end of normal temperature bracket, 512—lower fixed end of normal temperature bracket, 521—upper normal temperature slider, 522—lower normal temperature slider, 53—normal temperature guide rod, 541—upper normal temperature spring, 542—lower normal temperature spring, 6—normal temperature extensometer, 611—extensometer upper contact, 612—extensometer lower contact. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It is particularly noted that, under the premise of the present invention, some variations and improvements are made, which all fall within the scope of protection of the present invention.

[0028] In this embodiment, the sample is a 7075-T6 aluminum alloy plate with a thickness of 2 mm and a gauge length of 50 mm. Other dimensions are made in accordance with GB / T228.2-2015. The temperature range of the high temperature box is 0-1000°C, which is suitable for stretching most metal materials.

[0029] This embodiment provides a displacement measurement method suitable for high-temperature tensile testing of materials. The principle diagram of the method is shown in FIG. Figure 1 As shown, it mainly consists of three parts: a high-temperature box 1, a high-temperature displacement measurement module 2 and a normal-temperature displacement measurement module 5. The high-temperature tensile test is carried out in the high-temperature box 1.

[0030] The enlarged picture of high temperature displacement measurement module 2 is as follows Figure 2As shown, the specimen 23 is mounted between the upper high-temperature chuck 211 and the lower high-temperature chuck 212. The high-temperature guide rod 27 is fixedly mounted between the upper fixed end 241 of the high-temperature bracket and the lower fixed end 242 of the high-temperature bracket, with the axis of the high-temperature guide rod 27 parallel to the axis of the specimen 23. The upper high-temperature slider 261 and the lower high-temperature slider 262 are placed on the high-temperature guide rod 27 and can slide up and down along the high-temperature guide rod 27. The upper high-temperature slider 261 is connected to the upper fixed end 241 of the high-temperature bracket via an upper high-temperature spring 251, and the lower high-temperature slider 262 is connected to the lower fixed end 242 of the high-temperature bracket via a lower high-temperature spring 252. The upper high-temperature contact 221 is fixedly connected to the upper high-temperature slider 261, and the lower high-temperature contact 222 is fixedly connected to the lower high-temperature slider 262. The upper high-temperature contact 221 and the lower high-temperature contact 222 are respectively in contact with the surface of the specimen 23, with a gauge length of 50 mm, and are tied together by high-temperature resistant springs to provide a certain contact pressure.

[0031] The enlarged view of the normal temperature displacement measurement module 5 is as follows: Figure 3 As shown. In the normal-temperature displacement measurement module 5, the normal-temperature guide rod 53 is fixedly mounted between the upper fixed end 511 of the normal-temperature bracket and the lower fixed end 512 of the normal-temperature bracket. The upper and lower normal-temperature sliders 521 and 522 are placed on the normal-temperature guide rod 53 and can slide up and down. The upper and lower high-temperature sliders 261 and 262 are staggeredly connected to the lower and upper normal-temperature sliders 522 and 521 respectively via upper and lower high-temperature resistant threads 31 and 32. The upper and lower extensometer contacts 611 and 612 are in contact with the upper and lower normal-temperature sliders 521 and 522, respectively, and are tied with rubber bands to maintain a certain contact pressure. Finally, the normal-temperature extensometer 6 collects the displacement signal and imports it into the tensile test system. This method transfers the deformation and displacement measurement of the specimen in a high-temperature environment to a normal-temperature environment outside the high-temperature chamber, using a normal-temperature extensometer for measurement. This method solves the problem of electronic components being unable to operate or having low accuracy in high-temperature environments, significantly reducing costs.

Claims

1. A method for measuring deformation displacement of a high-temperature tensile test specimen, characterized in that: The following steps are involved: Step 1: Install the high-temperature displacement measurement module. Fix the test piece (23) between the upper high-temperature chuck (211) and the lower high-temperature chuck (212). Place the upper high-temperature slider (261) and the lower high-temperature slider (262) on the high-temperature guide rod (27). The upper high-temperature contact (221) and the lower high-temperature contact (222) are respectively fixedly connected to the upper high-temperature slider (261) and the lower high-temperature slider (262) in a vertical direction, and the other ends are respectively in contact with the surface of the test piece (23). Step 2: Install the normal temperature displacement measurement module. Fix the normal temperature guide rod (53) vertically between the upper fixed end (511) of the upper normal temperature bracket and the lower fixed end (512) of the normal temperature bracket. The upper normal temperature slider (521) and the lower normal temperature slider (522) are respectively fixedly connected to the upper high-temperature slider (261) and the lower high-temperature slider (522). Placed on the normal temperature guide rod (53) and slidable up and down, the upper contact (611) and the lower contact (612) of the extensometer are respectively brought into contact with the surface of the upper normal temperature slider (521) and the lower normal temperature slider (522), and a certain contact pressure is maintained by binding with a rubber band, and the signal of the normal temperature extensometer (6) is introduced into the test system; Step three, the upper high temperature slider (261) and the lower high temperature slider (262) are respectively connected to the lower normal temperature slider (522) and the upper normal temperature slider (521) by the upper high temperature resistant wire (31) and the lower high temperature resistant wire (32) in a staggered manner; Step four, adjust the tension of the upper high temperature resistant wire (31) and the lower high temperature resistant wire (32); Step five, start the tensile test system to start the test and complete the high temperature tensile test; The staggered connection described in step 3 refers to the connection of the upper high-temperature slider (261) to the lower normal-temperature slider (522), and the connection of the lower high-temperature slider (262) to the upper normal-temperature slider (521); The adjustment of the tension in step 4 is performed by rotating the upper tensioning wheel (41) to tighten the upper high-temperature resistant wire (31) so that the upper high-temperature slider (261) and the lower normal-temperature slider (522) are in dynamic equilibrium; and by rotating the lower tensioning wheel (42) to tighten the lower high-temperature resistant wire (32) so that the lower high-temperature slider (262) and the upper normal-temperature slider (521) are in dynamic equilibrium; The dynamic balance means that when the upper high-temperature slider (261) is subjected to any small displacement, the lower normal-temperature slider (522) will produce an equal reverse displacement; when the lower high-temperature slider (262) is subjected to any small displacement, the upper normal-temperature slider (521) will produce an equal reverse displacement.

2. The method for measuring deformation and displacement of a high-temperature tensile test specimen according to claim 1, characterized in that: The axis of the high-temperature guide rod (27) described in step 1 should be parallel to the axis of the test piece (23).

3. The method for measuring deformation and displacement of a high-temperature tensile test specimen according to claim 2, characterized in that: The vertical fixed connection described in step 1 is that the upper high-temperature contact (221) and the upper high-temperature slider (261) have no relative displacement along the axis of the high-temperature guide rod (27), but can have relative displacement in the horizontal direction; the lower high-temperature contact (222) and the lower high-temperature slider (262) have no relative displacement along the axis of the high-temperature guide rod (27), but can have relative displacement in the horizontal direction.

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