Strain gauge pasting quality testing device and usage method

Abstract

A strain gauge pasting quality testing device and a method for use thereof, which consists of a pad, a pressure block and a fastening bolt. One side of the pad in the thickness direction is a convex arc surface with a fixed curvature, and one side of the pressure block in the thickness direction is a concave arc surface consistent with the curvature of the pad arc surface. The fastening bolt connects the pad and the pressure block together through the bolt hole. During the test, the pad and the pressure block are clamped on the component to be tested from both sides of the component to be tested, and the component to be tested is forced to undergo a slight deformation along the known arc surface by tightening the fastening bolt. The error between the actual strain value of the strain gauge and the theoretical strain value is compared to judge the pasting quality of the strain gauge. Under the premise of non-destructive components, the present invention provides a reference standard for judging the pasting quality of strain gauges, which helps to discover strain gauge pasting quality problems in advance and improve the quality of strain detection data. The present invention has a simple principle and is easy to operate. It does not require large-scale loading equipment and is suitable for different detection environments such as laboratories and engineering sites, which is conducive to promotion and use.

Description

Technical Field

[0001] The present invention relates to the technical field of material mechanical property testing, and in particular to a testing device for detecting the pasting quality of strain gauges. Background Art

[0002] A strain gauge, composed of a sensitive grid, is used to measure the strain of a component. It is widely used in production and scientific research in fields such as civil engineering, machinery, and materials science. When subjected to force, a strain gauge deforms, causing its resistance to change. The gauge is firmly attached to the surface of a component. When the component deforms under force, the change in resistance is measured, converting it into the strain value at the component's measuring point.

[0003] The quality of strain gauge attachment directly impacts the accuracy of the resulting strain values. Due to the diverse stress environments, strain gauges are typically attached manually by inspectors based on their experience in practical applications. However, strain gauge attachment involves complex procedures such as interface cleaning, glue application, and patching. The entire process is significantly affected by human factors, such as proper cleaning and polishing of the attachment surface, the appropriate choice of glue, a uniform and appropriate glue thickness, and the removal of air bubbles during attachment. Measurement failures due to poor strain gauge attachment quality are common in practical engineering and scientific research, yet there is currently no reliable method to quantitatively verify strain gauge attachment prior to work. In engineering, strain gauge attachment issues often go undetected until the component is subjected to actual stress. Replacing or adding strain gauges at this point can severely impact data accuracy. For some concealed projects, the work surface is completely lost after the concealment work, and any issues with attachment quality can lead to data loss.

[0004] Existing national patents for strain gauges primarily address improvements to the structure of the strain gauge itself and the design of the strain gauge attachment device. No mention has been found of pre-work testing of the strain gauge attachment quality. However, strain gauge attachment quality is a crucial aspect of the inspection process. A simple and convenient method for testing the firm and precise attachment of strain gauges to components after attachment would allow inspectors to identify problematic gauges in advance and replace them promptly, thereby reducing the frequency of inspection issues and improving the quality of strain gauge inspection data. Summary of the Invention

[0005] The purpose of the present invention is to provide a strain gauge pasting quality testing device and method for use, which can simply, conveniently and quickly test the pasting quality of strain gauges in response to the deficiencies of the existing technology and the needs of engineering safety.

[0006] The present invention is achieved through the following technical solutions.

[0007] The strain gauge pasting quality testing device described in the present invention is composed of three parts: a cushion block, a pressure block and a fastening bolt.

[0008] The width of the pad can be pre-made into various sizes, and a pad larger than the width of the component to be measured can be selected according to the actual situation of the component to be measured.

[0009] The pad should be thick enough to ensure the overall rigidity of the pad.

[0010] One side of the pad in the thickness direction is a flat surface for mounting bolts; the other side is a convex curved surface with a fixed curvature, and its curvature radius R should be such that the thickness H of the component to be tested / pad curvature radius R = 1‰~1%. The curved surface is the surface in contact with the component to be tested.

[0011] The length direction of the pad is consistent with the length direction of the component to be tested. The four corners of the pad are respectively provided with bolt holes penetrating the thickness direction for installing fastening bolts to connect it with the pressure block.

[0012] The width of the pressing block should be consistent with that of the spacer.

[0013] The pressing block should be thick enough to ensure the overall rigidity of the pressing block. One side of the pressing block in the thickness (height) direction is a flat surface, and the other side is an inwardly concave arc surface with the same curvature as the arc surface of the cushion block.

[0014] The length direction of the pressing block should be consistent with that of the cushion block.

[0015] The concave arc surface of the pressure block should be provided with a dark groove slightly larger than the size of the strain gauge along the arc direction. When installing the test device, the dark groove should be aligned with the strain gauge on the component to be tested so that the strain gauge can be freely deformed in the dark groove.

[0016] The inner concave arc surface of the pressure block is manufactured to various cross-sectional shapes depending on the shape of the component being tested. For sheet, plate, or square rod-shaped components, a pressure block with a smooth cross-section is used; for round rod-shaped components, a pressure block with triangular beveled guide grooves is used to prevent the component from slipping under load.

[0017] The four corners of the pressing block are respectively provided with bolt holes which are consistent with the pad block and penetrate in the thickness direction.

[0018] The fastening bolts connect the pad and the pressing block together through the bolt holes.

[0019] The pads and pressure blocks can be made of solid steel or other materials with relatively high rigidity.

[0020] The method for using the strain gauge bonding quality testing device of the present invention is carried out according to the following steps:

[0021] (1) Connect the strain gauge on the component to be measured to the strain gauge in its natural state, measure the strain data, and measure the thickness value H of the component to be measured at the same time;

[0022] (2) Apply a small amount of vaseline to the surface of the component to be tested, clamp the component to be tested with a pad and a pressure block from both sides of the component to be tested, and place the strain gauge in the dark groove. At the same time, the length direction of the pad and the pressure block should be consistent with the component to be tested;

[0023] (3) Pass the fastening bolts through the bolt holes at the four corners of the pad and the pressure block, tighten the bolts and nuts with a wrench, and make the component to be measured bend along with the arc surface of the pressure block until it fits completely with the pad. Measure the strain data and calculate the actual strain value ε generated by the strain gauge after bending. r If the data is obviously unstable at this time, it is judged that the strain gauge is of poor quality and needs to be re-pasted;

[0024] (4) Along the length direction of the component to be tested, the theoretical strain value of the component to be tested should be:

[0025]

[0026] Where H is the thickness of the component to be measured, and R is the curvature radius of the pad. If the direction of the strain gauge is exactly the same as the length direction of the component to be measured, ε can be directly compared. r and If the deviation between the two is large, it is judged that the strain gauge is of poor quality and needs to be re-pasted. If the strain gauge pasting direction is required to form an angle α with the length direction of the component to be measured, it is necessary to change ε r Converted into the strain value in the length direction of the component:

[0027]

[0028] Then compare ε′ r and If the deviation between the two is large, it is judged that the strain gauge has poor pasting quality and needs to be re-pasted.

[0029] The beneficial effects of the present invention are:

[0030] (1) The present invention provides inspectors with a reference standard for judging the quality of strain gauge adhesion without damaging the components. This is very helpful for inspectors to discover strain gauge problems in advance and make timely adjustments, thereby reducing the frequency of detection problems and improving the quality of strain detection data.

[0031] (2) The device provided by the present invention does not require large-scale loading equipment and can be well adapted to different testing environments such as laboratories and engineering sites;

[0032] (3) The present invention has a simple implementation principle and is easy to operate. The supporting instruments are all traditional strain detection equipment, and there is no need to add other detection equipment and calculation software, which is conducive to social promotion.

[0033] The device of the present invention is mainly used to test the situation where the component to be tested has low rigidity but can produce a certain elastic deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is an assembly diagram of the strain gauge pasting quality testing device of the present invention (top view).

[0035] Figure 2 This is an assembly diagram of the strain gauge pasting quality testing device of the present invention (front view).

[0036] Figure 3 It is a structural diagram of a cushion block according to the present invention (front view).

[0037] Figure 4 This is a structural diagram of the cushion block of the present invention (side view).

[0038] Figure 5 This is a structural diagram (front view) of a pressing block 1 for sheet-shaped, plate-shaped, or square-bar-shaped components to be tested according to the present invention.

[0039] Figure 6 This is a structural diagram (side view) of a pressing block 1 for sheet-shaped, plate-shaped, or square-bar-shaped components to be tested according to the present invention.

[0040] Figure 7 This is a diagram of the pressing block structure of the present invention for sheet-shaped, plate-shaped, and square rod-shaped components to be tested (viewed from bottom).

[0041] Figure 8 This is a structural diagram of a pressing block for a round rod-shaped component to be tested according to the present invention (front view).

[0042] Figure 9 This is a structural diagram of the pressing block for a round rod-shaped component to be tested according to the present invention (side view).

[0043] Figure 10 This is a structural diagram of a pressing block for a round rod-shaped component to be tested according to the present invention (viewed from above).

[0044] Figure 11 This is a schematic diagram of the connection between the component to be measured and the strain gauge of the present invention (the strain gauge is in the same direction as the component).

[0045] Figure 12 Schematic diagram of the connection between the component to be measured and the strain gauge of the present invention (the strain gauge and the component are at a certain angle).

[0046] Figure 13 This is a schematic diagram of the calculation principle of the theoretical strain value tested in the present invention.

[0047] Among them, 1 is a pressure block, 2 is a spacer, 3 is a fastening bolt, 4 is a bolt hole, 5 is a hidden groove, 6 is a component to be measured, 7 is a guide groove, 8 is a strain gauge, and 9 is a strain meter. DETAILED DESCRIPTION

[0048] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0049] Figure 1 、 Figure 2 The working status of the device after the overall assembly is completed is shown from two angles: a top view and a front view. Figure 3 、 Figure 4 The structure of the pad device is shown from two angles: front view and side view. Figures 5 to 10 The structure of the pressing block device is shown from the front, side and bottom view angles. The present invention designs two types of pressing blocks to adapt to different types of test components, of which Figures 5 to 7 The pressure block shown has a smooth surface and is suitable for sheet, plate, and square rod components. Figures 8 to 10 The shown pressing block has a guide groove 7 added to the pressure surface to prevent the component from slipping after being subjected to force. It is suitable for round rod-shaped components. Figure 11 and Figure 12 It shows the connection of the strain gauge when the strain test is carried out after the component to be tested is attached. Figure 11 The length direction of the strain gauge is the same as that of the component. Figure 12 The included angle between the strain gauge and the length direction of the component is α. Figure 13 This is a schematic diagram of the strain value calculation, which is used to understand the derivation of the theoretical strain value calculation formula during component testing.

[0050] like Figure 1 、 Figure 2 Figure 1 shows a strain gauge adhesion quality testing device consisting of a spacer 1, a pressure block 2, and fastening bolts 3. Both pressure block 1 and spacer 2 have matching arcuate surfaces. A component 6 to be tested is clamped between spacer 1 and pressure block 2, with the arcuate surfaces forming the contact surfaces with component 6. Four fastening bolts 3 pass through bolt holes 4 to connect the entire device.

[0051] Example 1.

[0052] like Figure 1 、 Figure 2 、 Figures 5 to 7 As shown, the strain gauge bonding quality testing device described in this embodiment is composed of three parts: a pad 2, a pressure block 1 and a fastening bolt 3.

[0053] The width of the pad 2 is selected to be greater than the width of the component to be measured 6.

[0054] The cushion block 2 should be thick enough to ensure the overall rigidity of the cushion block 2 .

[0055] One side of the pad 2 in the thickness direction is flat for mounting the bolt 3; the other side is a convex curved surface with a constant curvature, the radius of curvature R of which should be such that the thickness H of the component to be tested 6 / the pad curvature radius R = 1‰ to 1%. The curved surface is the surface in contact with the component to be tested 6.

[0056] The length direction of the pad 2 is consistent with the length direction of the component to be tested 6. The four corners of the pad 2 are respectively provided with bolt holes 4 running through the thickness direction for installing fastening bolts 3 to connect it with the pressing block 1.

[0057] The width of the pressing block 1 should be consistent with that of the cushion block 2.

[0058] The pressing block 1 should be thick enough to ensure the overall rigidity of the pressing block 1. One side of the pressing block 1 in the thickness direction is a flat surface, and the other side is an inwardly concave arc surface with the same curvature as the arc surface of the cushion block 2.

[0059] The length direction of the pressing block 1 should be consistent with that of the cushion block 2.

[0060] The concave arc surface of the pressure block 1 should be provided with a dark groove 5 slightly larger than the size of the strain gauge 8 along the arc direction. When installing the test device, the dark groove 5 should be aligned with the strain gauge 8 on the component to be tested 6, so that the strain gauge 8 is in the dark groove 5 and can deform freely.

[0061] For the sheet-shaped, plate-shaped, or square-bar-shaped component 6 to be tested, the pressing block 1 described in this embodiment uses a pressing block 1 with a concave arc surface and a smooth cross-section on the inner side.

[0062] The four corners of the pressing block 1 are respectively provided with bolt holes 4 which are consistent with the pad block 2 and penetrate in the thickness direction.

[0063] The fastening bolts 3 connect the cushion block 2 and the pressing block 1 together through the bolt holes 4 .

[0064] The cushion block 2 and the pressing block 1 can be made of solid steel or other materials with strong rigidity.

[0065] In this embodiment, the pressure block 1 and the cushion block 2 both have matching arcuate surfaces. The component 6 to be tested is clamped between the cushion block 1 and the pressure block 2, with the arcuate surfaces serving as the contact surfaces with the component 6. Four fastening bolts 3 pass through bolt holes 4 to connect the entire device.

[0066] Example 2.

[0067] like Figures 8 to 10 As shown, for the round rod-shaped test member 6, the pressure block 1 of this embodiment uses a pressure block 1 with a concave arc surface containing a triangular inclined guide groove 7 on the inner side to prevent the test member 6 from slipping after being subjected to force. Other components and structures are the same as those in Example 1.

[0068] Example 3.

[0069] This embodiment considers that the component to be measured 6 is in sheet shape, and the strain gauge 8 is pasted on the component to be measured 6, and the length directions of the two are consistent. The pressing block is selected to have a smooth arc surface, such as Figures 5 to 7 , and the strain gauge wiring method is as follows Figure 11 The main steps of strain gauge pasting quality testing include:

[0070] (1) Use a vernier caliper to measure the thickness H of the component to be measured 6, connect the strain gauge 8 to the strain gauge 9 through a wire, and read the strain data without external force as the starting data;

[0071] (2) Apply a small amount of vaseline on the surface of the component to be tested 6. Place the curved surfaces of the pad 2 and the pressure block 1 facing each other and clamp them on both sides of the component to be tested 6. During installation, ensure that the length direction of the pad 2 and the pressure block 1 is consistent with the component to be tested 6, and that the position of the pasted strain gauge 8 can fall into the hidden groove 5 to ensure that the pressure block 1 does not directly contact the strain gauge 8 when under pressure;

[0072] (3) Fasten the bolt 3 through the bolt hole 4 to connect the pad 2 and the pressure block 1 together. Tighten the bolts and nuts with a wrench. During the tightening process, turn the fastening bolts 3 in the diagonal direction in sequence. The component to be tested 6 bends along with the arc surface of the pressure block 1 until it is completely fitted with the pad 2. Measure the strain data at this time and determine whether the strain gauge is firmly attached based on the stability of the data. If there is no obvious drift in the data, calculate the actual strain value ε generated during the bending process of the component to be tested. r ;

[0073] (4) Using the formula Calculate the theoretical strain value of the component to be tested 6 Comparison ε r and The error is used to judge the quality of strain gauge pasting.

[0074] Example 4.

[0075] This embodiment considers that the component to be measured 6 is a round rod and the direction of the strain gauge 8 is at an angle α to the length direction of the component to be measured 6. The arc surface of the pressure block is provided with a guide groove 7, such as Figures 8 to 10 , and the strain gauge wiring method is as follows Figure 12 The main steps of strain gauge pasting quality testing include:

[0076] (1) Use a vernier caliper to measure the thickness H of the component to be measured 6, connect the strain gauge 8 to the strain gauge 9 through a wire, and read the strain data without external force as the starting data;

[0077] (2) Apply a small amount of vaseline on the surface of the component to be tested 6. Place the curved surfaces of the pad 2 and the pressure block 1 opposite each other and clamp them on both sides of the component to be tested 6. When installing, the component to be tested 6 should be aligned with the guide groove 7 to ensure that the component to be tested 6 will not slide out of the guide groove 7 when under pressure, and the position of the pasted strain gauge 8 can fall into the hidden groove 5 to ensure that the pressure block 1 does not directly contact the strain gauge 8 when under pressure;

[0078] (3) Fasten the bolt 3 through the bolt hole 4 to connect the pad 2 and the pressure block 1 together, and tighten the bolt and nut with a wrench. The component to be tested 6 bends along with the arc surface of the pressure block 1 until it is completely in contact with the pad 2. Measure the strain data at this time and determine whether the strain gauge is firmly attached based on the stability of the data. If there is no obvious drift in the data, calculate the actual strain value ε generated by the bending process of the strain gauge 8 r ;

[0079] (4) Using the formula Calculate the actual strain value ε′ of the component to be measured 6 in the bending direction r ,use Calculate the theoretical strain value of the component to be tested 6 Compare ε′ r and The error is used to judge the quality of strain gauge pasting.

[0080] Results Analysis: Using a strain gauge bonding quality testing device, the quality of strain gauge bonding can be quickly tested before a component is subjected to significant external forces or strain measurements. The device is simple in principle, easy to operate, and highly efficient, without impacting the original strain measurement schedule. The testing device is adaptable to a variety of component shapes and strain gauge bonding methods, and can be used in a variety of applications, from laboratory specimen testing to on-site structural testing. Extensive comparative tests have shown that the strain gauge bonding quality testing device of the present invention significantly reduces the probability of strain gauge failure and significantly improves the data integrity of strain tests.

[0081] The above description is only an embodiment of the present invention and does not limit the present invention in any form. Therefore, any simple modification, equivalent transformation or decoration made according to the technical essence of the present invention without departing from the content of the present invention is still within the scope of patent protection of the present invention.

Claims

1. A strain gauge pasting quality testing device, characterized by It consists of three parts: pad, pressure block and fastening bolts. The pad and pressure block are fixed by fastening bolts. The width of the pad is greater than the width of the component to be tested; The thickness of the pad should ensure that the pad has sufficient overall rigidity; One side of the pad in the thickness direction is a flat surface for mounting bolts; the other side is a convex arc surface with a fixed curvature, and its curvature radius R should be such that the thickness H of the component to be tested / the curvature radius R of the pad = 1‰~1%, where the arc surface is the surface in contact with the component to be tested; The length direction of the pad is consistent with the length direction of the component to be tested; the four corners of the pad are respectively provided with bolt holes penetrating the thickness direction, for installing fastening bolts to connect it with the pressure block; The width of the pressing block is consistent with that of the spacer; The thickness of the pressing block should ensure that the pressing block has sufficient overall rigidity; one side of the pressing block in the thickness direction is a flat surface, and the other side is a concave arc surface with the same curvature as the arc surface of the cushion block; The length direction of the pressing block is consistent with that of the cushion block; The concave arc surface of the pressure block is provided with a dark groove slightly larger than the size of the strain gauge along the arc direction. When the test device is installed, the dark groove is aligned with the strain gauge on the component to be tested, so that the strain gauge is in the dark groove and can deform freely. The four corners of the pressing block are respectively provided with bolt holes which are consistent with the thickness direction of the pad; The fastening bolts connect the pad and the pressing block together through the bolt holes; Tighten the bolts and nuts with a wrench to make the component to be tested bend along with the arc surface of the pressure block until it fits completely with the pad.

2. A strain gauge pasting quality testing device according to claim 1, characterized in that The inner side of the concave arc surface of the pressing block is a smooth cross section for sheet-shaped, plate-shaped, or square rod-shaped components to be tested, or a cross section containing a triangular inclined guide groove for a round rod-shaped component to be tested.

3. The method for using the strain gauge bonding quality testing device according to claim 1, characterized in that Follow these steps: (1) Connect the strain gauge on the component to be measured to the strain gauge in its natural state, measure the strain data, and simultaneously measure the thickness value H of the component to be measured; (2) Apply a small amount of vaseline to the surface of the component to be tested, clamp the component to be tested with a pad and a pressure block from both sides of the component to be tested, and place the strain gauge in the dark groove. At the same time, the length direction of the pad and the pressure block should be consistent with the component to be tested; (3) Pass the fastening bolts through the bolt holes at the four corners of the pad and the pressure block, tighten the bolts and nuts with a wrench, and make the component to be measured bend along with the arc surface of the pressure block until it fits completely with the pad. Measure the strain data and calculate the actual strain value ε generated by the strain gauge after bending. r If the data is obviously unstable at this time, it is judged that the strain gauge is of poor quality and needs to be re-pasted; (4) Along the length direction of the component to be tested, the theoretical strain value of the component to be tested should be: Where H is the thickness of the component to be measured, and R is the curvature radius of the pad. If the direction of the strain gauge is exactly the same as the length direction of the component to be measured, ε can be directly compared. r and If the deviation between the two is large, it is judged that the strain gauge is of poor quality and needs to be re-pasted; if the strain gauge pasting direction is required to form an angle α with the length direction of the component to be measured, it is necessary to adjust ε r Converted into the strain value in the length direction of the component: Then compare ε r 'and If the deviation between the two is large, it is judged that the strain gauge has poor pasting quality and needs to be re-pasted.

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