A tooth root patch mold and its manufacturing method, and a strain gauge installation method

Abstract

The present invention belongs to the technical field of research, development and testing of aircraft engines, and particularly relates to a tooth root patch mold, a method for making the same, and a method for installing a strain gauge. By using a tooth root patch mold to replace tape and rubber, the proposed tooth root patch mold has consistency. The small recessed cavity at the bottom of the tooth root patch mold formed after removing the small-sized strain gauge has the function of fixing the small-sized strain gauge, accurately positioning the strain gauge and well controlling the thickness after bonding. It can ensure that the position and final thickness of the strain gauge remain consistent during multiple pasting processes, and can solve problems such as uneven adhesive layer and excessive thickness leading to failure caused by pressurizing the strain gauge. The tooth root patch mold adopts a process of curing and molding from the outside to the inside, which can effectively avoid problems such as stress concentration in the mold corners and size reduction caused by volume shrinkage during the curing of the photosensitive resin. A loading rod is provided in the mold, which can be used to apply pressure for a long time for the adhesive to be heated and pressurized for curing.

Description

Technical Field

[0001] The present invention belongs to the technical field of research, development and testing of aircraft engines, and in particular relates to a tooth root patch mold and a manufacturing method thereof, and a strain gauge installation method. Background Art

[0002] Conventional strain gauge installation typically involves attaching tape to the back of the strain gauge. The tape is then moved to transfer the strain gauge, and the gauge is positioned by observing the markings around the gauge to align it with a reference line on the test piece. During installation, adhesive is applied to the underside of the strain gauge, and the tape is used to transfer the strain gauge to the designated location. Even pressure is then applied using finger pressure until the adhesive is fully cured. For adhesives with longer cure times, higher pressure requirements, or those that require heat curing, rubber blocks are used instead of finger pressure, and spring clips are used to apply pressure.

[0003] When transferring strain gauges using tape, the positioning of the gauges requires visual inspection to ensure alignment with the reference line, making precise measurement impossible. This is difficult to achieve in the confined space of a tooth root, where strain gauge positioning accuracy (±0.2mm) is particularly demanding. Even if position measurement is performed after application, the gauge cannot be moved for correction because it is already adhered. Applying pressure using finger pressure or cutting rubber blocks is not suitable for small strain gauges (0.6mm x 6mm) in tooth roots. This is because fingers cannot penetrate the tooth base. Furthermore, poorly shaped rubber blocks can easily cause asymmetrical pressure, resulting in the strain gauges shifting from their intended position, uneven adhesive thickness, or even an out-of-tolerance final thickness. Consequently, measurement after application reveals that the strain gauges have not met the required position and height, leading to different responses to deformation among multiple strain gauges installed at the same tooth base, or even crushing and failure during gear meshing.

[0004] In response to the above-mentioned problems, some solutions have been proposed in the prior art. Chinese application publication number CN107843371A discloses a strain gauge installation method, comprising the following steps: polishing and cleaning the installation area; spraying a pre-coat, spraying an active spray material on the installation area of ​​the test piece to form a pre-coat; and fixing the strain gauge, fixing the strain gauge on the pre-coat with one surface of the strain gauge attached to the pre-coat; spraying a cover coat, spraying the active spray material on the remaining surface of the strain gauge and the portion of the pre-coat not covered by the strain gauge to form a cover coat; spraying a final coat, spraying the active spray material on the cover coat to form a final coat; and connecting a high-temperature wire, connecting the pins of the strain gauge to the high-temperature wire. There is also a Chinese application with publication number CN109357605A that proposes a method for installing a gear tooth root strain gauge with a narrow top gap, including: determining the installation position, determining the position with maximum stress at the tooth root of the gear to be installed as the installation position; strain gauge preparation, matching the spatial size of the strain gauge with the top gap of the gear to be installed; polishing and cleaning, polishing and cleaning the installation position of the tooth root of the gear to be installed; strain gauge installation, gluing and fixing the strain gauge at the installation position and pressing it tightly; terminal installation, installing the terminal for connecting the test wire and the lead of the strain gauge on the non-working surface of the gear to be installed adjacent to the strain gauge installation tooth; lead distribution and fixation, laying the leads on both sides of the strain gauge along the bottom of the tooth groove respectively, folding the lead away from the terminal side back or passing through the vibration damping hole and then gathering it with the lead on the other side at the terminal and fixing it to the terminal, so that the leads and the leads, and the leads and the strain gauge do not overlap with each other.

[0005] However, none of the above methods can completely solve the problem of high-precision installation of strain gauges in a narrow space. Summary of the Invention

[0006] In response to the above problems, the present invention proposes a method for manufacturing a tooth root patch mold to solve the problem that strain gauges are difficult to install on the tooth roots of gears with narrow top clearance. The manufacturing method includes the following steps:

[0007] Position the strain gauge at the tooth root patch position and fix the strain gauge pin so that the entire strain gauge fits the tooth bottom;

[0008] Fix baffles on both sides of the tooth width, and spray a release agent on the funnel-shaped cavity formed by the baffles and the working surface of the tooth root;

[0009] After the release agent is formed, pouring a photosensitive resin into the cavity and irradiating it with a UV lamp until the photosensitive resin forms an outer hollow shell with hardness, and then stopping the irradiation;

[0010] Pouring photosensitive resin into the outer hollow shell, shaking the gear and irradiating it with a UV lamp until the photosensitive resin thickens inwardly to form an inner hollow shell;

[0011] A loading rod is placed in the inner hollow shell, and then photosensitive resin is added and irradiated with a UV lamp to form a complete tooth root patch mold.

[0012] Furthermore, before positioning the strain gauge at the patch position on the tooth root, the following steps are also included:

[0013] Grind the patch position of the tooth root and clean the tooth root where the strain gauge needs to be attached.

[0014] Furthermore, after forming a complete tooth root patch mold, the following steps are also included:

[0015] Separating the tooth root patch mold from the tooth root;

[0016] Repair the excess part of the tooth root patch mold that extends beyond the gear working surface.

[0017] Furthermore, the baffle is a tetrafluoroethylene plate.

[0018] Furthermore, fixing the pin of the strain gauge so that the entire strain gauge fits the tooth bottom specifically includes: determining the position of the strain gauge through a reading microscope, and fine-tuning the strain gauge to meet the installation requirements.

[0019] Furthermore, the installation requirements are that the position accuracy requirement is ±0.2mm and the thickness does not exceed the tooth top clearance requirement;

[0020] The tooth top gap is required to be greater than the thickness of the adhesive layer, strain gauge, and protective rubber layer.

[0021] On the other hand, the present invention also proposes a tooth root patch mold manufactured using the manufacturing method.

[0022] Furthermore, the bottom of the tooth root patch mold has a small concave cavity that cooperates with the strain gauge;

[0023] The tooth root patch mold includes an outer hollow shell, which is fitted with the tooth root; multiple inner hollow shells are formed inside the outer hollow shell, and a loading channel for a loading rod is left inside the hollow shell.

[0024] In a third aspect, the present invention provides a method for installing a strain gauge, which uses the manufactured tooth root patch mold to install the strain gauge.

[0025] Furthermore, the installation method includes the following steps:

[0026] Fit the strain gauge into the recessed cavity at the bottom of the tooth root patch mold, and fix the strain gauge pins to the front and back sides of the tooth root patch mold;

[0027] Apply adhesive evenly on the bottom of the strain gauge;

[0028] Inserting the tooth root patch mold with the strain gauge attached along the tooth root position so that the surface of the tooth root patch mold fits the tooth root and the baffle;

[0029] The required pressure is calculated based on the required bonding pressure, and the pressure is applied to the entire tooth root patch mold through the loading rod and then evenly applied to the strain gauge;

[0030] Cure according to the adhesive curing conditions.

[0031] Beneficial effects of the present invention:

[0032] The present invention uses a tooth root patch mold instead of tape and rubber, which can solve the problem of inaccurate positioning of small-sized strain gauges in the narrow space of the tooth root. It can also solve the problems of uneven adhesive layer and excessive thickness leading to failure when pressurizing the strain gauge.

[0033] The tooth root patch mold of the present invention adopts a layer-by-layer curing molding process from the outside to the inside, which can effectively avoid the problems of stress concentration in the mold corners and size reduction caused by volume shrinkage during the curing of the photosensitive resin. In addition, a loading rod is provided in the tooth root patch mold, which can be used to apply pressure for a long time for the adhesive to be heated and pressurized for curing.

[0034] The tooth root patch mold proposed in the present invention has consistency. The concave small cavity at the bottom of the tooth root patch mold formed after removing the small-sized strain gauge has the function of fixing the small-sized strain gauge, can accurately position the strain gauge and well control the thickness after bonding, and can ensure that the position and final thickness of the strain gauge remain consistent during multiple pasting processes.

[0035] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 A schematic structural diagram of a tooth root patch mold according to an embodiment of the present invention is shown;

[0038] Figure 2 A flow chart showing a method for making a tooth root patch mold according to an embodiment of the present invention is shown;

[0039] Figure 3 A flow chart of a method for installing a strain gauge using a tooth root patch mold in an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0041] A strain gauge is a sensor used to sense stress changes on a structure's surface and produce synchronous deformation. The strain is reflected by the resistance change caused by the strain gauge grid being stretched (or compressed) after deformation. This resistance change is measured using a Wheatstone bridge circuit, which can be used to measure the strain on the surface of the structure being measured. To address the inconvenience of strain gauge installation and the lack of precise measurement and positioning in existing technologies, the present invention utilizes a tooth root patch mold to assist in strain gauge installation, enabling high-precision installation of strain gauges within the confined space of a tooth root.

[0042] The structural diagram of the tooth root patch mold proposed by the present invention is as follows: Figure 1 As shown, the bottom of the tooth root patch mold is fitted with the tooth bottom of the tooth root, and includes an outer empty shell, an inner empty shell and a loading rod. The bottom of the outer empty shell is fitted with the tooth root, the inner empty shell is cast in the outer empty shell, and a loading channel for the loading rod is left in the middle of the inner empty shell.

[0043] The manufacturing method of the tooth root patch mold proposed by the present invention mainly includes the following steps: tooth root grinding, cleaning, positioning strain gauge, sealing both sides of the tooth width and spraying release agent, pouring the outer layer of photosensitive resin to form, pouring the inner layer to form and fix the loading rod, demoulding and repairing the tooth root patch mold; the specific operation of each step is as follows Figure 2 As shown:

[0044] Tooth root grinding and cleaning: simply grind the tooth root where the patch is to be applied, and clean the tooth root to be patched to remove impurities or particles on the tooth root surface;

[0045] Positioning the strain gauge: Operate the enameled leads on both sides of the strain gauge to position the strain gauge at the desired patch location and secure its leads to the gear so that the entire strain gauge fits snugly against the tooth bottom. In this embodiment, the strain gauge measures 0.6mm by 6mm. In this embodiment, the strain gauge position can be determined using a reading microscope and fine-tuned to achieve the required positional accuracy (±0.2mm). The thickness of the strain gauge should not exceed the required tooth top clearance, which is generally approximately 0.6-0.7mm. This dimension must be greater than the thickness of the adhesive layer, strain gauge, and protective rubber layer to prevent the strain gauge from being squeezed and failing.

[0046] Seal both sides of the tooth width and spray the release agent: fix the baffle on both sides of the tooth width (i.e., the two side surfaces of the tooth root excluding the working surface) to form a funnel-shaped cavity, spray a small amount of release agent, and evenly coat the release agent on the surface of the funnel-shaped cavity. After removing the excess release agent, allow it to evaporate in the air for 5-10 minutes; in this embodiment, the baffle is made of tetrachloroethylene board.

[0047] Pouring the outer layer of photosensitive resin: Pour a small amount of photosensitive resin glue into the cavity. By shaking the gear, the photosensitive resin is coated on the surface of the funnel-shaped cavity with a thickness of about 0.5-1mm. The photosensitive resin at the bottom should completely cover the small-sized strain gauge and avoid the formation of bubbles. Continue to shake the gear slowly and irradiate the photosensitive resin glue with a UV lamp until the outer shell is formed.

[0048] The inner layer is cast and the loading rod is fixed: After the outer shell reaches a certain hardness, the UV light is stopped, and a small amount of photosensitive resin is added. Slowly shake it and irradiate it with UV light, thickening it inward by 1-2mm to form the inner shell. The inner shell can be formed into multiple layers. A loading channel for the loading rod is left in the middle of the innermost shell. The loading rod is placed in it, and photosensitive resin is added. The UV light is irradiated to form a complete tooth root patch mold.

[0049] Demolding repair: Separate the entire tooth root patch mold from the tooth root, forming a small concave cavity at the bottom strain gauge position; repair the excess part on the tooth root patch mold, and slightly repair some excess parts on both sides of the tooth width where the gear working surface fits.

[0050] The tooth root patch mold made by the above manufacturing method includes an outer hollow shell, multiple inner hollow shells inside the outer hollow shell, and a loading rod inserted into the innermost hollow shell. There is a concave small cavity at the bottom of the outer hollow shell, and the small cavity fits the strain gauge.

[0051] In another embodiment of the present invention, the tooth root patch mold manufactured by the above method is used to install a strain gauge, which specifically includes the following steps:

[0052] Step 1: Grind and clean the tooth root to be patched;

[0053] Step 2: Fit the strain gauge into the small recessed cavity at the bottom of the tooth root patch mold, and fix the strain gauge pins to the front and back sides of the tooth root patch mold. Install the strain gauge in this way, and the direction and position of the strain gauge are exactly the same as the original positioning strain gauge.

[0054] Step 3: Apply a small amount of adhesive evenly on the bottom of the strain gauge to form an adhesive layer;

[0055] Step 4: Insert the entire tooth root patch mold with the strain gauge attached along the tooth root position, so that the left and right sides of the strain gauge are attached to the working surface, and the front and back sides are attached to the tetrachloroethylene sheet;

[0056] Step 5: Calculate the required pressure based on the required bonding pressure, then apply it to the entire tooth root patch mold through the loading rod and evenly apply it to the strain gauge;

[0057] Step 6: Cure according to the adhesive's curing conditions. Once curing is complete, remove the tooth root patch mold. Curing conditions include heat and pressure curing, room temperature curing, or light curing. If heat and pressure curing is required, use a tool to maintain pressure on the loading rod and then place the gear in an oven for curing. If the adhesive can be cured directly or requires light curing, simply set the corresponding curing conditions.

[0058] The tooth root patch mold proposed in the present invention can accurately install strain gauges within a narrow range and can be applied to testing occasions such as fixed gear rings and bevel gears.

[0059] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for making a tooth root patch mold, characterized in that: The production method comprises the following steps: Position the strain gauge at the tooth root patch position and fix the strain gauge pin so that the entire strain gauge fits the tooth bottom; Fix baffles on both sides of the tooth width, and spray a release agent on the funnel-shaped cavity formed by the baffles and the working surface of the tooth root; After the release agent is formed, pouring a photosensitive resin into the cavity and irradiating it with a UV lamp until the photosensitive resin forms an outer hollow shell with hardness, and then stopping the irradiation; Pouring photosensitive resin into the outer hollow shell, shaking the gear and irradiating it with a UV lamp until the photosensitive resin thickens inwardly to form an inner hollow shell; A loading rod is placed in the inner hollow shell, and then photosensitive resin is added and irradiated with a UV lamp to form a complete tooth root patch mold.

2. The method for manufacturing a tooth root patch mold according to claim 1, characterized in that: Before positioning the strain gages at the tooth root patch locations, the following steps are also included: Grind the patch position of the tooth root and clean the tooth root where the strain gauge needs to be attached.

3. The method for manufacturing a tooth root patch mold according to claim 1, characterized in that: After forming a complete tooth root patch mold, it also includes: Separating the tooth root patch mold from the tooth root; Repair the excess part of the tooth root patch mold that extends beyond the gear working surface.

4. The method for manufacturing a tooth root patch mold according to any one of claims 1 to 3, characterized in that: The baffle is a tetrafluoroethylene plate.

5. The method for manufacturing a tooth root patch mold according to claim 1, characterized in that: Fixing the strain gauge pin so that the entire strain gauge fits the tooth bottom is specifically as follows: determining the position of the strain gauge through a reading microscope, and fine-tuning the strain gauge to meet the installation requirements.

6. The method for manufacturing a tooth root patch mold according to claim 5, characterized in that: The installation requirements are that the position accuracy is ±0.2mm and the thickness does not exceed the tooth top clearance requirements; The tooth top gap is required to be greater than the thickness of the adhesive layer, strain gauge, and protective rubber layer.

7. A tooth root patch mold, characterized in that: The tooth root patch mold is made by the manufacturing method according to any one of claims 1 to 6.

8. The tooth root patch mold according to claim 7, characterized in that: The bottom of the tooth root patch mold has a small concave cavity that cooperates with the strain gauge; The tooth root patch mold includes an outer hollow shell, which is fitted with the tooth root; multiple inner hollow shells are formed inside the outer hollow shell, and a loading channel for a loading rod is left inside the hollow shell.

9. A method for installing a strain gauge, characterized in that: A strain gauge is installed using the tooth root patch mold made by any one of claims 1 to 6 or the patch mold described in claim 7 or 8.

10. The method for installing a strain gauge according to claim 9, wherein: The installation method comprises the following steps: Fit the strain gauge into the recessed cavity at the bottom of the tooth root patch mold, and fix the strain gauge pins to the front and back sides of the tooth root patch mold; Apply adhesive evenly on the bottom of the strain gauge; Inserting the tooth root patch mold with the strain gauge attached along the tooth root position so that the surface of the tooth root patch mold fits the tooth root and the baffle; The required pressure is calculated based on the required bonding pressure, and the pressure is applied to the entire tooth root patch mold through the loading rod and then evenly applied to the strain gauge; Cure according to the adhesive curing conditions.

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