High-temperature static strain gauge preparation method and high-temperature static strain gauge

Abstract

This invention provides a method for preparing a high-temperature static strain gauge and the high-temperature static strain gauge itself. The method includes: step S01, surface treatment of the test piece; step S02, attaching a working strain gauge to the surface of the test piece; step S03, laying a first high-temperature cotton insulation layer on top of the working strain gauge; step S04, laying a compensation strain unit on the first high-temperature cotton insulation layer; step S05, laying a second high-temperature cotton insulation layer on the compensation strain unit; and step S06, bridging the strain gauge and covering the second high-temperature cotton insulation layer with a protective layer. This invention solves the problem of large differences between steady-state and transient thermal output caused by the curve correction method, and realizes real-time measurement of static strain in high-temperature environments.

Description

Technical Field

[0001] This invention relates to the field of high-temperature static strain testing technology, specifically to a method for preparing a high-temperature static strain gauge and the high-temperature static strain gauge itself. Background Technology

[0002] Existing methods for measuring high-temperature static strain with compensated strain gauges have solved the problem of the compensated strain gauge and the working strain gauge sharing the same temperature field. However, they suffer from limitations such as the inability to guarantee the flatness of the mounting surface of the compensated strain gauge, and the spray-coating fixing method between the compensated and working strain gauges. This means that the grid wires of the compensated strain gauge can still deform along with the deformation of the working strain gauge, leading to stress issues with the compensated strain gauge and failing to meet the requirement that the compensated strain gauge only senses temperature and not force. Therefore, there is an urgent need to invent a novel high-temperature static strain gauge with a compensated strain gauge that can operate in high-temperature environments. Summary of the Invention

[0003] In view of this, the present invention provides a method for preparing a high-temperature static strain gauge and a high-temperature static strain gauge, so as to solve the problem that existing high-temperature static strain tests in China cannot completely make the compensating strain gauge free from force, and improve the accuracy and reliability of high-temperature static strain measurement results.

[0004] The present invention provides the following technical solution: 1. A method for preparing a high-temperature static strain gauge, comprising: step S01, surface treatment of the test piece; step S02, attaching a working strain gauge to the surface of the test piece; step S03, laying a first high-temperature cotton insulation layer above the working strain gauge; step S04, laying a compensation strain unit on the first high-temperature cotton insulation layer; step S05, laying a second high-temperature cotton insulation layer on the compensation strain unit; step S06, bridging and covering the second high-temperature cotton insulation layer with a protective layer.

[0005] A high-temperature static strain gauge includes: a working strain gauge, attached to a test specimen; a first high-temperature cotton insulation layer, laid on the upper surface of the working strain gauge; a compensation strain unit, laid on the upper surface of the first high-temperature cotton insulation layer; a second high-temperature cotton insulation layer, laid on the upper surface of the compensation strain unit; and a protective layer, covering the second high-temperature cotton insulation layer.

[0006] Compared with the prior art, the beneficial effects that the at least one technical solution adopted by the present invention can achieve include at least the following:

[0007] By ensuring that the compensated strain gauge and the working strain gauge measure the strain of the test piece in the same temperature field, the problem of large difference between steady-state and transient thermal output caused by the curve correction method is solved, and real-time measurement of static strain in high-temperature environment is realized.

[0008] This invention breaks through the limitations of traditional strain gauge bonding. The novel strain gauge bonding method ensures that the strain gauge is only subjected to material strain caused by temperature. Because the strain gauge is wrapped in high-temperature cotton, the problem of strain gauge bonding stress is solved. Unevenness in the bonding position will not cause unevenness on the strain gauge surface, reducing the risk of strain gauge damage due to stress. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 A schematic diagram of the process for manufacturing a high-temperature static strain gauge with a novel compensation strain gauge for this invention.

[0011] Figure 2 This is a three-dimensional schematic diagram of the layered structure of a high-temperature static strain gauge with a novel compensation strain gauge, which was fabricated according to the present invention.

[0012] Figure 3 This is a two-dimensional structural schematic diagram of a high-temperature static strain gauge with a novel compensation strain gauge, which was fabricated according to the present invention.

[0013] The figures are labeled as follows: 1. Test piece; 2. Working strain gauge; 3. First high-temperature cotton insulation layer; 4. Compensating strain gauge; 5. Metal sheet; 6. Second high-temperature cotton insulation layer; 7. Protective layer. Detailed Implementation

[0014] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0015] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0016] like Figure 1 As shown, this embodiment of the invention provides a method for preparing a high-temperature static strain gauge, including the following steps:

[0017] Step S01: Surface Treatment of the Test Specimen. A test specimen made of a high-temperature alloy (such as Inconel 718) was selected. This specimen will be used for static strain testing at 800℃. First, acetone was used as a chemical cleaning agent to wipe the area of ​​the test specimen where the working strain gauge will be attached, removing surface dust, oil, and other impurities. Then, 1200-grit wet sandpaper was used to finely polish the area, removing the surface oxide layer. The surface roughness Ra after polishing was controlled between 0.8-1.2 μm to ensure the flatness of the strain gauge mounting position and the insulation performance after subsequent attachment. After polishing, the specimen was wiped clean again with acetone and allowed to air dry naturally for later use.

[0018] Step S02: The working strain gauge is attached using a dedicated flame spraying device. The high-temperature working strain gauge (HFN series strain gauge, operating temperature up to 870℃) is attached to the designated measurement position on the surface-treated test piece. During the flame spraying process, the flame temperature is controlled at 1200℃, the spraying distance at 150mm, and the spraying pressure at 0.6MPa to ensure a tight and firm bond between the working strain gauge and the test piece surface, without bubbles or curling edges.

[0019] Step S03: Laying the First High-Temperature Insulation Layer. Alumina fiber cotton is selected as the material for the first high-temperature insulation layer. This material can withstand temperatures up to 1200℃ and maintains stable thermal insulation and electrical properties under high-temperature environments. According to the dimensions of the working strain gauge, appropriately sized pieces of alumina fiber cotton are cut and laid flat on the upper surface of the working strain gauge with a thickness of 1mm, ensuring complete coverage of the working strain gauge and achieving insulation isolation between the working strain gauge and subsequent structures.

[0020] Step S04: Laying the Compensating Strain Unit. First, select a high-temperature alloy sheet of the same material as the test piece, with a thickness of 0.12 mm, and cut it into a shape matching the size of the working strain gauge. Adhere the compensating strain gauge, matching the model of the working strain gauge, to the center of the metal sheet using high-temperature adhesive. During adhesion, ensure the compensating strain gauge is flat, without wrinkles or misalignment, forming the compensating strain unit. After the adhesive has cured, place the compensating strain unit stably on the upper surface of the first high-temperature cotton insulation layer, aligning the compensating strain gauge with the working strain gauge in the vertical direction, ensuring both are in the same temperature field.

[0021] Step S05: Laying the second high-temperature cotton insulation layer. The same alumina fiber cotton as the first high-temperature cotton insulation layer is used. After cutting, it is laid flat on the upper surface of the strain compensation unit to form the second high-temperature cotton insulation layer, with a thickness of 1mm. At this point, the strain compensation unit is completely wrapped by both the first and second high-temperature cotton insulation layers, and does not directly contact the test specimen, thus avoiding the influence of forces generated by the deformation of the test specimen. It can only sense temperature changes.

[0022] Step S06: Bridging and Protective Layer Installation First, connect the leads of the working strain gauge and the compensating strain gauge using a half-bridge connection to form a half-bridge measurement circuit. This circuit effectively compensates for strain values ​​caused by temperature changes, measuring only the static strain caused by force changes. Next, a high-temperature resistant stainless steel protective layer is selected and placed over the upper surface of the second high-temperature cotton insulation layer, completely encasing the entire strain gauge structure. Lead holes are pre-drilled in the protective layer; the measurement leads of the working and compensating strain gauges are led out through these holes for easy connection to the measuring equipment. Finally, the protective layer is fixed to the test piece using high-temperature bolts to ensure the stability of the entire structure under high-temperature conditions.

[0023] Modified Example 1

[0024] The core difference between this modified embodiment and the basic embodiment lies in the adjustment of the test specimen material, the material and thickness of the high-temperature cotton insulation layer. It is suitable for static strain testing in a medium-high temperature environment of 600℃, as detailed below:

[0025] Step S01: Surface treatment of test specimens. The test specimens are made of 304 stainless steel. The surface treatment of the area to be pasted is the same as that of the basic embodiment. The surface roughness Ra is controlled between 0.6-1.0μm to ensure flatness and insulation.

[0026] Step S02: The working strain gauge is attached using a flame spraying device. The working strain gauge is an HFN series high-temperature strain gauge (working temperature up to 870℃). The spraying flame temperature is controlled at 1000℃, the spraying distance is 120mm, and the spraying pressure is 0.5MPa to ensure that the working strain gauge is firmly attached.

[0027] Step S03: Use aluminum silicate fiber cotton (high temperature resistant 1000℃) for laying. Adjust the laying thickness to 3mm. Other laying requirements are the same as those in the basic embodiment.

[0028] Step S04: Laying the metal sheet of the compensation strain unit. The sheet is made of the same material as the 304 stainless steel test piece and has a thickness of 0.3 mm. The compensation strain gauge is the same model as the working strain gauge. The pasting and placement method is the same as the basic embodiment.

[0029] Step S05: Lay the second high-temperature cotton insulation layer. Also use aluminum silicate fiber cotton, with a thickness of 3mm, to ensure that the compensation strain unit is wrapped.

[0030] Step S06: The bridging method and the protective layer are the same as in the basic embodiment. The protective layer is made of 304 stainless steel and is fixed by welding. The size of the reserved lead hole is adjusted according to the number of lead wires. Other requirements remain unchanged.

[0031] Modified Example 2

[0032] This modified embodiment addresses the static strain testing requirements in high-temperature environments above 1000℃ by optimizing the fabrication method and structure, as detailed below:

[0033] Step S01: Surface treatment of test specimens. The test specimens are made of silicon carbide ceramic matrix composite material. The area to be bonded is first cleaned with a plasma cleaner to remove impurities and oxide layers. Then, it is polished with a diamond wheel to control the surface roughness Ra between 1.0-1.5μm. After polishing, plasma cleaning is performed again to ensure surface cleanliness and flatness.

[0034] Step S02: Adhesive bonding of working strain gauges. GC high-temperature ceramic adhesive is used instead of flame spraying to bond the working strain gauges. HFH series strain gauges (working temperature up to 1375℃) are selected. The adhesive coating thickness is controlled at 0.4mm. After bonding, the strain gauges are cured in a 315℃ oven for 2 hours to ensure a firm bond.

[0035] Step S03: Laying the first high-temperature cotton insulation layer. Zirconia fiber cotton (high temperature resistance 1600℃) is selected and laid with a thickness of 1mm. High-temperature fire-resistant adhesive is used to fix it during the laying process to prevent displacement.

[0036] Step S04: Laying the metal sheet for the compensation strain unit. Select a high-temperature alloy sheet (such as GH4169) with a thermal expansion coefficient that matches that of the silicon carbide ceramic matrix composite material. The thickness is 0.12mm. The compensation strain gauge is the same model as the working strain gauge. It is attached to the metal sheet with a high-temperature ceramic adhesive. After curing, it is placed on the first high-temperature cotton insulation layer to ensure alignment with the working strain gauge.

[0037] Step S05: Lay the second high-temperature cotton insulation layer. Zirconia fiber cotton is selected and laid with a thickness of 1mm. It is also fixed with high-temperature fire-resistant adhesive to completely wrap the compensation strain unit.

[0038] Step S06: The bridging method for the bridge and the protective layer is a semi-bridging method. The protective layer is made of high-temperature resistant alloy steel plate (material Inconel 625), which is fixed to the test piece by high-temperature bolts. The reserved lead hole is insulated with high-temperature resistant ceramic sleeve. The lead wire is made of high-temperature resistant armored cable to ensure normal operation in high-temperature environment.

[0039] like Figure 2 and Figure 3As shown, the present invention also provides a high-temperature static strain gauge. The high-temperature static strain gauge obtained by the above preparation method includes the following structure: a test piece 1, a working strain gauge 2, a first high-temperature cotton insulation layer 3, a compensation strain unit, a second high-temperature cotton insulation layer 6, and a protective layer 7. The working strain gauge 2 is attached to a designated measurement position on the test piece 1; the first high-temperature cotton insulation layer 3 is laid on the upper surface of the working strain gauge 2; the compensation strain unit consists of a compensation strain gauge 4 and a metal sheet 5 bonded together, and the metal sheet 5 is made of the same material as the test piece 1, and is laid on the upper surface of the first high-temperature cotton insulation layer 3; the second high-temperature cotton insulation layer 6 is laid on the upper surface of the compensation strain unit; the protective layer 7 covers the second high-temperature cotton insulation layer, and the protective layer has reserved holes for lead wires to be led out.

[0040] In one embodiment, the materials of the first high-temperature cotton insulation layer 3 and the second high-temperature cotton insulation layer 6 are replaced with aluminum silicate fiber cotton, the thickness is adjusted to 1 mm, and the material of the metal sheet 5 is matched with that of the 304 stainless steel test piece 1, which is suitable for strain measurement in medium and high temperature environments.

[0041] In another embodiment, the strain gauge is bonded with a high-temperature ceramic adhesive; the first high-temperature cotton insulation layer 3 and the second high-temperature cotton insulation layer 6 are made of zirconium oxide fiber cotton with a thickness of 1mm; the metal sheet 5 is made of a high-temperature alloy with a thermal expansion coefficient matching that of the test piece 1; the protective layer 7 is made of alloy steel plate with higher temperature resistance; the lead wire and lead wire hole are designed with high temperature resistance, which is suitable for accurate static strain measurement in high-temperature environments above 1000℃.

[0042] The high-temperature static strain gauges prepared in the above embodiments are achieved by attaching the compensating strain gauge to a thin metal sheet with the same or matching coefficient of thermal expansion as the test specimen, and by using two layers of high-temperature cotton insulation to isolate the compensating strain unit from the working strain gauge and the test specimen. This ensures that the compensating strain gauge is only affected by the temperature field and is not affected by the deformation force of the test specimen. Simultaneously, the working strain gauge and the compensating strain gauge form a half-bridge circuit, effectively canceling out strain interference caused by temperature, thus realizing real-time and accurate measurement of static strain caused by force changes under high-temperature conditions.

[0043] The basic embodiment is suitable for high-temperature environments of around 800℃ with a measurement error of ≤±0.5%; the modified embodiment 1 is suitable for medium-high temperature environments of around 600℃ with a measurement error of ≤±0.6%; and the modified embodiment 2 is suitable for ultra-high temperature environments above 1000℃ with a measurement error of ≤±0.8%. All of these embodiments solve the problem of low measurement accuracy caused by the stress on the compensating strain gauge in traditional high-temperature static strain measurement, and improve the reliability and stability of the measurement results.

[0044] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical solutions, and technical solutions in this invention can be freely combined and used.

Claims

1. A method for preparing a high-temperature static strain gauge, characterized in that, include: Step S01: Perform surface treatment on the test piece; Step S02: Attach the working strain gauge to the surface of the test piece; Step S03: Lay the first high-temperature cotton insulation layer above the working strain gauge; Step S04: Lay a strain compensation unit on the first high-temperature cotton insulation layer; Step S05: Lay a second high-temperature cotton insulation layer on the compensation strain unit; The compensation strain unit is completely wrapped by the first high-temperature cotton insulation layer and the second high-temperature cotton insulation layer. It does not directly contact the test piece, thus avoiding the influence of the force generated by the deformation of the test piece. It can only sense temperature changes. Step S06: Perform bridge assembly and cover the protective layer onto the second high-temperature cotton insulation layer.

2. The method for preparing a high-temperature static strain gauge according to claim 1, characterized in that, The specific steps of step S01 are as follows: removing impurities from the surface of the test piece at the bonding location and adjusting its flatness.

3. The method for preparing a high-temperature static strain gauge according to claim 2, characterized in that, Step S02 specifically involves attaching the working strain gauge to the surface of the location to be attached using a flame spraying method.

4. The method for preparing a high-temperature static strain gauge according to claim 3, characterized in that, Step S04 specifically involves: The compensating strain gauge is attached to a metal sheet of the same material as the test piece to form a compensating strain unit; The compensation strain unit is placed on the first high-temperature cotton insulation layer.

5. The method for preparing a high-temperature static strain gauge according to claim 4, characterized in that, Step S06 includes: The leads of the working strain gauge and the compensation strain gauge are combined to form a half-bridge to counteract the strain value caused by temperature.

6. The method for preparing a high-temperature static strain gauge according to claim 5, characterized in that, Step S06 further includes: Cover the entire second high-temperature cotton insulation layer with a protective layer, and lead out the working strain gauge and the compensation strain gauge leads from the reserved holes in the protective layer.

7. The method for preparing a high-temperature static strain gauge according to claim 6, characterized in that, Both the first and second high-temperature cotton insulation layers are made of alumina fiber cotton.

8. A high-temperature static strain gauge, characterized in that, include: Working strain gauge (2) is attached to test piece (1); The first high-temperature cotton insulation layer (3) is laid on the upper surface of the working strain gauge (2); The strain compensation unit is laid on the upper surface of the first high-temperature cotton insulation layer (3); The second high-temperature cotton insulation layer (6) is laid on the upper surface of the compensation strain unit; The compensation strain unit is completely wrapped by the first high-temperature cotton insulation layer and the second high-temperature cotton insulation layer. It does not directly contact the test piece, thus avoiding the influence of the force generated by the deformation of the test piece. It can only sense temperature changes. A protective layer (7) is placed over the second high-temperature cotton insulation layer (6).

9. A high-temperature static strain gauge according to claim 8, characterized in that, The compensation strain unit includes a compensation strain gauge (4) bonded together as a whole and a metal sheet (5).

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