A method for determining the dynamic tensile bond strength between a coating and a substrate

Abstract

The application is a kind of method for determining the dynamic tensile bonding strength between coating and substrate. It comprises the following steps: preparing a dynamic tensile bonding sample; constructing a double measurement system composed of high sensitivity semiconductor strain gauges and conventional resistance strain gauges on a transmission rod, carrying out an empty rod strong dynamic load calibration test; using SHTB device to apply dynamic tensile load to the sample, causing the coating-substrate interface to fail; discriminating the failure mode; calculating the dynamic tensile bonding stress time history curve of the coating-substrate interface from the transmission wave voltage of the semiconductor strain gauge, determining the loading rate according to the maximum tangent slope of the rising section of the dynamic tensile bonding stress time history curve, and determining the dynamic tensile bonding strength between the coating and the substrate according to the peak value of the dynamic tensile bonding stress time history curve. The application fills the gap of related test technology and provides key technical support for the performance evaluation of the bonding strength of high-performance coatings under dynamic load conditions.

Description

Technical Field

[0001] This invention belongs to the field of material mechanical property testing, specifically relating to a method for determining the dynamic tensile bond strength between a coating and a substrate. Background Technology

[0002] In modern engineering, coating technology is a key means of improving or endowing substrates with specific properties, and its applications are extremely wide. For example, by applying functional coatings to metal or ceramic surfaces, their corrosion resistance and wear resistance can be significantly improved; in geotechnical engineering, novel polymer sprays are used as flexible support structures for tunnels or slopes to resist impact or explosive loads. In all engineering applications, the bond strength between the coating and the substrate is a fundamental indicator determining the reliability and lifespan of the entire coating-substrate system.

[0003] Current testing methods for evaluating bond strength, such as the scratch test, indentation test, or direct tensile test (pull-out test), are all conducted under static or quasi-static loading conditions. However, many coated components will be subjected to dynamic loads during their service life. For example, the protective coatings of weaponry need to withstand projectile impacts and explosions; the support coatings of underground engineering projects may be subject to dynamic load disturbances such as rock bursts or blasting excavation.

[0004] Numerous studies have shown that the mechanical behavior of materials and their interfaces exhibits a significant strain rate effect, meaning that mechanical properties under dynamic loading can differ significantly from those under static loading. Therefore, relying solely on static test results cannot accurately reflect the actual adhesion performance of the coating / substrate interface under dynamic loading conditions, and may even lead to erroneous or overly optimistic safety assessments. Thus, an experimental method is needed to accurately and reliably measure the dynamic tensile bond strength between the coating and the substrate, filling the gap in existing testing techniques and providing crucial experimental data support for the design and application of high-performance coatings. Summary of the Invention

[0005] To overcome the lack of effective means in the existing technology to characterize the interfacial tensile bond performance of coating / substrate systems under high strain rate loads such as impact, this invention aims to provide a method for determining the dynamic tensile bond strength of coating / substrate interfaces based on the Split Hopkinson tensile bar (SHTB) technology, which can achieve high strain rate loading, reliable data, and good repeatability.

[0006] The technical solution for achieving the objective of this invention is: a method for determining the dynamic tensile bond strength between a coating and a substrate, comprising the following steps:

[0007] Step (1): Prepare dynamic tensile bonded specimens using a rigid sleeve;

[0008] Step (2): Construct a dual measurement system on the transmission rod consisting of symmetrically arranged high-sensitivity semiconductor strain gauges and conventional resistance strain gauges, and conduct a strong dynamic load calibration test on the empty rod to obtain the calibration coefficients of the semiconductor strain gauges. :

[0009] Step (3): Apply dynamic tensile load to the sample using the split Hopkinson bar SHTB device, causing the coating-substrate interface to fail.

[0010] Step (4): Determine the failure mode; the test is only valid if the failure occurs at the coating-substrate interface.

[0011] Step (5): Calculate the dynamic tensile bond stress time history curve of the coating-substrate interface from the transmitted wave voltage of the semiconductor strain gauge, determine the loading rate based on the maximum tangent slope of the rising segment of the dynamic tensile bond stress time history curve, and determine the dynamic tensile bond strength between the coating and the substrate based on the peak value of the dynamic tensile bond stress time history curve.

[0012] Furthermore, step (1) specifically involves:

[0013] Step (11): Select a cylindrical substrate sample with the same diameter as the Hopkinson tie rod and a height-to-diameter ratio of 1:1, and clean the surface with acetone or alcohol;

[0014] Step (12): Use a rigid sleeve with the same inner diameter as the substrate sample as the mold. The rigid sleeve is a split-half type. The height of the rigid sleeve is the sum of the height of the substrate sample and the expected coating thickness. After spraying the sleeve with release agent, place the substrate sample coaxially in the mold. Pour the prepared coating material into the mold and smooth it along the top surface of the sleeve with a scraper to form a uniform coating thickness. Cure the sample with the mold for 20-36 hours.

[0015] Step (13): Demolding and curing; after curing, perform quality inspection on the sample.

[0016] Step (14): Bond the two ends of the qualified test specimen to the dynamic loading fixture with epoxy resin.

[0017] Furthermore, the quality inspection in step (13) includes checking the coating thickness using a vernier caliper and visually inspecting macroscopic defects at the bonding interface between the coating and the substrate.

[0018] During the bonding process in step (14), ensure that the sample coincides with the central axis of the upper and lower loading fixtures.

[0019] Furthermore, step (2) specifically involves: conducting a dynamic load calibration test on an empty pole and simultaneously acquiring the voltage signal of the resistor element. and semiconductor strain gauge voltage signal The calibration coefficients of the semiconductor strain gauge were obtained. :

[0020] .

[0021] Furthermore, step (3) specifically involves:

[0022] In the Hopkinson bar test, the dynamically tensile bonded specimen is installed between the incident bar and the transmission bar using a dynamic loading fixture, ensuring that the coated end of the specimen is connected to the incident bar. The impact bar is driven by air pressure to strike the flange ring at the end of the incident bar at a set speed, thereby exciting and generating a tensile stress wave in the incident bar. The tensile stress wave acts directly on the coating-substrate bonding interface, causing the coating-substrate interface to fail.

[0023] Furthermore, the failure mode determination in step (4) specifically involves:

[0024] Dynamic failure mode I: When failure occurs at the bonding interface between the coating and the substrate, and the area of ​​the substrate attached to the coating surface is not greater than 40% of the total bonding area, it is considered as a debonding failure of the coating and the substrate interface. The test results are valid, and the strength value measured under this failure mode is the true dynamic tensile bond strength of the coating-substrate interface.

[0025] Dynamic Failure Mode II: Failure occurs at the interface between the epoxy resin and the substrate or coating, and the test is invalid; this indicates that the dynamic tensile bond strength between the epoxy resin and the substrate or coating is lower than the dynamic tensile bond strength between the coating and the substrate, and a stronger epoxy resin should be used to prepare a new sample for testing.

[0026] Dynamic failure mode III: Failure occurs simultaneously between the coating and the substrate, and the substrate itself is also damaged. The test is invalid, and the test results do not represent the interfacial adhesion performance.

[0027] Dynamic failure mode IV: Failure occurs within the coating material, i.e., cohesive failure, rather than at the coating-substrate bonding interface, rendering the test invalid. This failure mode indicates that the dynamic bond strength at the coating-substrate interface is higher than the dynamic tensile strength of the coating material itself, and the measured result is the cohesive strength of the coating rather than the interfacial bond strength.

[0028] Dynamic failure mode V: All bonding interfaces remain intact, but the substrate itself fractures, rendering the test invalid; this indicates that the dynamic tensile bond strength of the interface is higher than the dynamic tensile strength of the substrate, and the measured value is the dynamic tensile strength of the substrate, which is less than the true dynamic tensile bond strength of the coating / substrate interface.

[0029] Furthermore, step (5) specifically involves: when the failure mode of the sample is dynamic failure mode I, the force measured in the transmission rod reflects the dynamic tensile force applied to the coating-substrate interface. Based on the one-dimensional elastic stress wave theory, the dynamic tensile bonding stress time history curve of the coating-substrate interface is determined by the transmitted wave voltage signal of the semiconductor strain gauge, and its calculation formula is:

[0030]

[0031] in For dynamic tensile bond stress; and These are the cross-sectional areas of the rod and the specimen, respectively. Let be the elastic modulus of the rod. For the sensitivity of the resistance strain gauge, For bridge pressure, The gain coefficient of the dynamic strain gauge connected to the resistance strain gauge;

[0032] The loading rate is determined based on the maximum tangent slope of the rising segment of the dynamic tensile bond stress time history curve, and the dynamic tensile bond strength between the coating and the substrate is determined based on the peak value of the dynamic tensile bond stress time history curve.

[0033] Furthermore, the substrate is metal, ceramic, or rock, and the coating is an epoxy resin coating or a polyurethane coating.

[0034] Compared with the prior art, the significant advantages of this invention are:

[0035] (1) Applicable to dynamic load conditions. This method utilizes the mature Hopkinson tie rod technology to achieve high strain rate loading, which truly simulates the stress state of the coating under dynamic load conditions such as impact and explosion, and overcomes the fundamental defect that static tests cannot reflect the strain rate effect.

[0036] (2) The calculation is simple and accurate. The present invention can directly calculate the dynamic tensile bond strength using only the transmitted wave signal. This not only simplifies the data processing flow, but also avoids the calculation error that may be introduced when using the "three-wave method" or "two-wave method" due to the superposition of incident wave and reflected wave on the end face of the sample, making the measurement results more direct and reliable;

[0037] (3) Wide applicability: This invention is applicable to evaluating the dynamic tensile bonding performance between various coatings (such as epoxy resin coatings, polyurethane coatings) and different substrates (such as metals, ceramics, rocks, etc.), and can be widely used in aerospace, defense, transportation and other fields. Attached Figure Description

[0038] Figure 1 To prepare a dynamic tensile bonded specimen for the rigid sleeve in this invention.

[0039] Figure 2 The images show the dynamic loading fixture and the prepared sample involved in this invention; where (a) is a schematic diagram and (b) is a physical image.

[0040] Figure 3 The method of mounting dynamically tensile bonded specimens on a Hopkinson bar and the dual measurement system consisting of semiconductor strain gauges and conventional resistance strain gauges.

[0041] Figure 4 Typical voltage signal waveform of the dual measurement system during testing.

[0042] Figure 5 Types of dynamic tensile bond failure.

[0043] Figure 6 The loading rate and dynamic tensile bond strength are determined based on the dynamic tensile bond stress-time history curve. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention.

[0045] A method for determining the dynamic tensile bond strength between a coating and a substrate includes: preparing a dynamic tensile bond specimen using a rigid sleeve, and applying a dynamic tensile load to the specimen using a split Hopkinson bar (SHTB) device, causing failure at the coating / substrate interface. To address the problem of weak transmitted wave signals potentially caused by large impedance differences between the coating, substrate, and bar, this invention proposes constructing a dual measurement system on the transmission bar, consisting of a high-sensitivity semiconductor strain gauge and a conventional resistance strain gauge. The semiconductor strain gauge amplifies and captures the weak transmitted wave signal, while the symmetrically arranged conventional strain gauges are used for real-time calibration and standardization of the transmitted wave, significantly improving the accuracy and reliability of the data. After the impact test, the bond failure mode is determined, and the test is only valid when failure occurs at the coating / substrate interface. The dynamic tensile bond stress-time history curve of the coating / substrate interface is calculated from the transmitted wave voltage of the semiconductor strain gauge. The loading rate is determined based on the maximum tangent slope of the rising segment of the dynamic tensile bond stress-time history curve, and the dynamic tensile bond strength between the coating and the substrate is determined based on the peak value of the dynamic tensile bond stress-time history curve.

[0046] Preparation of dynamically tensile bonded specimens includes:

[0047] Step 1: Select a cylindrical base material with the same diameter as the Hopkinson tie rod and a height-to-diameter ratio of 1:1, and clean its surface with acetone or alcohol;

[0048] Step 2: A rigid sleeve with the same inner diameter as the substrate sample is used as a mold. The sleeve height is designed to be the sum of the substrate sample height and the expected coating thickness to achieve precise control of the coating thickness. After spraying the sleeve with a release agent, the rock substrate is coaxially placed in the mold. The prepared coating material is poured into the mold and smoothed along the top surface of the sleeve with a scraper to form a uniform coating thickness. The sample is cured in the mold for 24 hours. This initial curing ensures sufficient initial bond strength between the coating and the substrate interface. Premature demolding may cause debonding damage at the interface edges during the demolding process, thus adversely affecting the test results.

[0049] Step 3: After demolding, the sample continues to cure under the pre-set curing conditions for the preset time. After curing, the sample undergoes a quality inspection, including: a) measuring the sample height to ensure the coating thickness meets the expected requirements; b) visually inspecting the adhesion interface between the coating and the substrate to confirm the absence of macroscopic defects such as bubbles or delamination. Any sample with visible defects should be considered unqualified, discarded, and re-prepared.

[0050] Step 4: Use high-strength epoxy resin to bond both ends of the specimen to the dynamic loading fixtures. During bonding, ensure that the central axis of the specimen is strictly aligned with the central axis of the upper and lower loading fixtures to achieve overall vertical alignment. Central alignment ensures that no torque is generated when the loading fixtures are connected to the Hopkinson rod and prevents eccentric loading during the experiment.

[0051] Applying dynamic tensile loads to specimens using a split Hopkinson tie rod (SHTB) device includes:

[0052] In the Hopkinson bar test, the dynamically tensile bonded specimen is installed between the incident bar and the transmission bar using a dynamic loading fixture, ensuring that the coated end of the specimen is connected to the incident bar. The impact bar is driven by air pressure to impact the flange ring at the end of the incident bar at a certain speed, thereby exciting and generating a tensile stress wave within the incident bar. The tensile stress wave acts directly on the coating / substrate bonding interface, causing the coating / substrate interface to fail.

[0053] Due to the significant difference in wave impedance between the coating, substrate, and rod, the stress wave signal (transmitted wave) transmitted to the transmission rod is extremely weak. Therefore, a high-sensitivity semiconductor strain gauge is attached to the transmission rod to effectively amplify and reliably acquire the transmitted wave signal. Considering that semiconductor strain gauges are susceptible to drift errors caused by changes in environmental factors such as temperature and humidity, conventional resistance strain gauges are also attached to the same cross-section and symmetrical positions of the transmission rod to ensure the accuracy of the test results. Both types of strain gauges are connected in a quarter-bridge configuration to a dynamic strain gauge with a gain coefficient of 100, a low-pass filter of 10 kHz, and a bridge voltage of 2 V, and then connected to a data acquisition instrument with a sampling frequency of 1 MHz via a data transmission line.

[0054] Conduct a dynamic load calibration test on an empty pole and simultaneously acquire the voltage signal of the resistor element. and semiconductor strain gauge voltage signal The calibration coefficients of the semiconductor strain gauge were obtained. :

[0055]

[0056] The identification of adhesion failure modes includes:

[0057] To ensure that the measured strength value represents the true dynamic tensile bond strength, the failure modes of the specimens should be examined and classified after the test. The failure modes and their corresponding validity criteria are as follows:

[0058] Dynamic Failure Mode I: Failure occurs at the bonding interface between the coating and the substrate, and when the area of ​​the substrate adhering to the coating surface is no more than 40% of the total bonded area, it is considered a debonding failure of the coating-substrate interface, and the test results are valid. The strength value measured under this failure mode is the true dynamic tensile bond strength of the coating / substrate interface;

[0059] Dynamic Failure Mode II: Failure occurs at the interface between the epoxy resin and the substrate or coating, and the test is invalid; this indicates that the dynamic tensile bond strength between the epoxy resin and the substrate or coating is lower than the dynamic tensile bond strength between the coating and the substrate, and a stronger epoxy resin should be used to prepare a new sample for testing.

[0060] Dynamic failure mode III: Failure occurs simultaneously between the coating and the substrate, and the substrate itself is also damaged. The test is invalid, and the test results do not represent the interfacial adhesion performance.

[0061] Dynamic failure mode IV: Failure occurs inside the coating material (i.e., cohesive failure) rather than at the coating / substrate bonding interface, and the test is invalid; this failure mode indicates that the dynamic bond strength at the coating / substrate interface is higher than the dynamic tensile strength of the coating material itself, and the measured result is the cohesive strength of the coating rather than the interfacial bond strength.

[0062] Dynamic failure mode V: All bonding interfaces remain intact, but the substrate itself fractures, rendering the test invalid; this indicates that the dynamic tensile bond strength of the interface is higher than the dynamic tensile strength of the substrate, and the measured value is the dynamic tensile strength of the substrate, which is less than the true dynamic tensile bond strength of the coating / substrate interface.

[0063] In summary, only when the failure mode of the sample is dynamic failure mode I can the corresponding measured value be adopted as the dynamic tensile bond strength of the coating / substrate interface.

[0064] Determining the dynamic tensile bond strength between the coating and the substrate includes:

[0065] The force measured in the transmission rod reflects the dynamic tensile force applied to the coating / substrate interface. Based on the one-dimensional elastic stress wave theory, the time history curve of the dynamic tensile bond stress at the coating / substrate interface is determined by the transmitted wave voltage signal from the semiconductor strain gauge. The calculation formula is as follows:

[0066]

[0067] in For dynamic tensile bond stress; and These are the cross-sectional areas of the rod and the specimen, respectively. Let be the elastic modulus of the rod. For the sensitivity of the resistance strain gauge, For bridge pressure, This is the gain coefficient of the dynamic strain gauge connected to the resistance strain gauge.

[0068] The loading rate is determined based on the maximum tangent slope of the rising segment of the dynamic tensile bond stress time history curve, and the dynamic tensile bond strength between the coating and the substrate is determined based on the peak value of the dynamic tensile bond stress time history curve.

[0069] Example

[0070] This embodiment aims to determine the dynamic tensile bond strength between a specific polymer coating and a rock substrate.

[0071] Step 1: Sample Preparation: Select a cylindrical rock substrate sample with the same diameter as the Hopkinson rod (19.5 mm) and a height-to-diameter ratio of 1:1, and clean its surface with acetone; use a detachable two-half steel sleeve with an inner diameter of 19.5 mm as a mold. The mold height is designed to be the sum of the substrate height (19.5 mm) and the target coating thickness (1 mm), i.e., 20.5 mm; after spraying the mold with a release agent, place the rock substrate coaxially in the mold; pour the prepared coating material into the mold and smooth it along the top surface of the mold, as shown. Figure 1 As shown; the molded specimen was cured for 24 hours under standard experimental conditions (25℃, 55%) before demolding. The demolded specimen continued to cure for 6 days. The coating thickness was measured using calipers to ensure it met expectations, and the coating / substrate interface was visually confirmed to be well-bonded, without macroscopic defects such as bubbles or delamination. High-strength epoxy resin was used to bond both ends of the specimen to the dynamic loading fixture. The prepared specimen is shown below. Figure 2 As shown.

[0072] Step 2: Sample loading and data acquisition:

[0073] like Figure 3 As shown, the dynamically tensile bonded specimen is mounted between the incident rod and the transmission rod using a dynamic loading fixture. The coated end of the specimen is connected to the incident rod, and the elastic modulus of the rod is... The value is 71.2 GPa. Semiconductor strain gauges are attached to the transmission rod of the Hopkinson bar to effectively amplify and reliably acquire the transmitted wave voltage signal. In this embodiment, the sensitivity of the resistance strain gauge is... The bridge voltage is 2.11. The gain coefficient of the dynamic strain gauge connected to the resistance strain gauge is 2V. The value is 100. Considering that semiconductor strain gauges are susceptible to drift errors caused by changes in environmental factors such as temperature and humidity, conventional resistance strain gauges are simultaneously attached to the transmission rod for calibration. The impact gas pressure is set to 0.6 MPa. The impact rod strikes the flange ring at the end of the incident rod, and the tensile stress wave acts directly on the coating / substrate bonding interface. A typical voltage signal waveform of the dual measurement system during the test is shown below. Figure 4 As shown.

[0074] Step 3: Identify the failure mode:

[0075] To ensure that the measured strength value represents the true dynamic tensile bond strength, the failure modes of the specimens are examined and classified after the test. For example... Figure 5 As shown, the failure modes and their corresponding validity criteria are as follows:

[0076] Dynamic Failure Mode I: Failure occurs at the bonding interface between the coating and the substrate, and when the area of ​​the substrate adhering to the coating surface is no more than 40% of the total bonded area, it is considered a debonding failure of the coating-substrate interface, and the test results are valid. The strength value measured under this failure mode is the true dynamic tensile bond strength of the coating / substrate interface;

[0077] Dynamic Failure Mode II: Failure occurs at the interface between the epoxy resin and the substrate or coating, and the test is invalid; this indicates that the dynamic tensile bond strength between the epoxy resin and the substrate or coating is lower than the dynamic tensile bond strength between the coating and the substrate, and a stronger epoxy resin should be used to prepare a new sample for testing.

[0078] Dynamic failure mode III: Failure occurs simultaneously between the coating and the substrate, and the substrate itself is also damaged. The test is invalid, and the test results do not represent the interfacial adhesion performance.

[0079] Dynamic failure mode IV: Failure occurs inside the coating material (i.e., cohesive failure) rather than at the coating / substrate bonding interface, and the test is invalid; this failure mode indicates that the dynamic bond strength at the coating / substrate interface is higher than the dynamic tensile strength of the coating material itself, and the measured result is the cohesive strength of the coating rather than the interfacial bond strength.

[0080] Dynamic failure mode V: All bonding interfaces remain intact, but the substrate itself fractures, rendering the test invalid; this indicates that the dynamic tensile bond strength of the interface is higher than the dynamic tensile strength of the substrate, and the measured value is the dynamic tensile strength of the substrate, which is less than the true dynamic tensile bond strength of the coating / substrate interface.

[0081] In summary, only when the failure mode of the specimen is dynamic failure mode I can the corresponding measured value be adopted as the dynamic tensile bond strength of the coating / substrate interface. In this case, the specimen's failure mode is type I, and the test results are valid.

[0082] Step 4: Calculate the dynamic tensile bond strength between the coating and the substrate:

[0083] The force measured in the transmission rod reflects the dynamic tensile force applied to the coating / substrate interface. Based on the one-dimensional elastic stress wave theory, the time history curve of the dynamic tensile bond stress at the coating / substrate interface is determined by the transmitted wave voltage signal of the semiconductor strain gauge. In this case, the calibration factor α of the semiconductor strain gauge compared to the resistance strain gauge in the no-load dynamic load calibration test is 17. Based on the transmitted wave voltage signal of the semiconductor strain gauge... The dynamic tensile bond stress time history curve is determined using the following formula ( Figure 6 ):

[0084]

[0085] The loading rate was determined to be 86000 MPa / s based on the maximum tangent slope of the rising segment of the dynamic tensile bond stress time history curve, and the dynamic tensile bond strength between the coating and the substrate was determined to be 3.51 MPa based on the peak value of the dynamic tensile bond stress time history curve.

[0086] The final test results showed that the dynamic tensile bond strength between the 1 mm coating and the rock substrate at a loading rate of 86,000 MPa / s was 3.51 MPa.

Claims

1. A method for determining the dynamic tensile bond strength between a coating and a substrate, characterized in that, Includes the following steps: Step (1): Prepare dynamic tensile bonded specimens using a rigid sleeve; Step (2): Construct a dual measurement system on the transmission rod consisting of symmetrically arranged high-sensitivity semiconductor strain gauges and conventional resistance strain gauges, and conduct a strong dynamic load calibration test on the empty rod to obtain the calibration coefficients of the semiconductor strain gauges. : Step (3): Apply dynamic tensile load to the sample using the split Hopkinson bar SHTB device, causing the coating-substrate interface to fail. Step (4): Determine the failure mode; the test is only valid if the failure occurs at the coating-substrate interface. Step (5): Calculate the dynamic tensile bond stress time history curve of the coating-substrate interface from the transmitted wave voltage of the semiconductor strain gauge, determine the loading rate based on the maximum tangent slope of the rising segment of the dynamic tensile bond stress time history curve, and determine the dynamic tensile bond strength between the coating and the substrate based on the peak value of the dynamic tensile bond stress time history curve.

2. The method according to claim 1, characterized in that, Step (1) is as follows: Step (11): Select a cylindrical substrate sample with the same diameter as the Hopkinson tie rod and a height-to-diameter ratio of 1:1, and clean the surface with acetone or alcohol; Step (12): Use a rigid sleeve with the same inner diameter as the substrate sample as a mold. The rigid sleeve is a split-half type. The height of the rigid sleeve is the sum of the height of the substrate sample and the expected coating thickness. After spraying the sleeve with release agent, place the substrate sample coaxially in the mold. Pour the prepared coating material into the mold and smooth it along the top surface of the sleeve with a scraper to form a coating with uniform thickness. Cur the sample with the mold for 20-36 hours; Step (13): Demolding and curing; after curing, perform quality inspection on the sample. Step (14): Bond the two ends of the qualified test specimen to the dynamic loading fixture with epoxy resin.

3. The method according to claim 2, characterized in that, The quality inspection in step (13) includes checking the coating thickness using a vernier caliper and visually inspecting the macroscopic defects at the bonding interface between the coating and the substrate. During the bonding process in step (14), ensure that the sample coincides with the central axis of the upper and lower loading fixtures.

4. The method according to claim 1, characterized in that, Step (2) specifically involves: conducting a dynamic load calibration test on an empty pole and simultaneously acquiring the voltage signal of the resistor element. and semiconductor strain gauge voltage signal The calibration coefficients of the semiconductor strain gauge were obtained. : 。 5. The method according to claim 1, characterized in that, Step (3) is as follows: In the Hopkinson bar test, the dynamically tensile bonded specimen is installed between the incident bar and the transmission bar using a dynamic loading fixture, ensuring that the coated end of the specimen is connected to the incident bar. The impact bar is driven by air pressure to impact the flange ring at the end of the incident bar at a set speed, thereby exciting and generating a tensile stress wave in the incident bar. The tensile stress wave acts directly on the coating-substrate bonding interface, causing the coating-substrate interface to fail.

6. The method according to claim 1, characterized in that, The specific steps for determining the failure mode in step (4) are as follows: Dynamic failure mode I: When failure occurs at the bonding interface between the coating and the substrate, and the area of ​​the substrate attached to the coating surface is not greater than 40% of the total bonding area, it is considered as a debonding failure of the coating and the substrate interface. The test results are valid, and the strength value measured under this failure mode is the true dynamic tensile bond strength of the coating-substrate interface. Dynamic Failure Mode II: Failure occurs at the interface between the epoxy resin and the substrate or coating, and the test is invalid; this indicates that the dynamic tensile bond strength between the epoxy resin and the substrate or coating is lower than the dynamic tensile bond strength between the coating and the substrate, and a stronger epoxy resin should be used to prepare a new sample for testing. Dynamic failure mode III: Failure occurs simultaneously between the coating and the substrate, and the substrate itself is also damaged. The test is invalid, and the test results do not represent the interfacial adhesion performance. Dynamic failure mode IV: Failure occurs within the coating material, i.e., cohesive failure, rather than at the coating-substrate bonding interface, rendering the test invalid. This failure mode indicates that the dynamic bond strength at the coating-substrate interface is higher than the dynamic tensile strength of the coating material itself, and the measured result is the cohesive strength of the coating rather than the interfacial bond strength. Dynamic failure mode V: All bonding interfaces remain intact, but the substrate itself fractures, rendering the test invalid; this indicates that the dynamic tensile bond strength of the interface is higher than the dynamic tensile strength of the substrate, and the measured value is the dynamic tensile strength of the substrate, which is less than the true dynamic tensile bond strength of the coating / substrate interface.

7. The method according to claim 1, characterized in that, Step (5) specifically involves: when the failure mode of the sample is dynamic failure mode I, the force measured in the transmission rod reflects the dynamic tensile force applied to the coating-substrate interface. Based on the one-dimensional elastic stress wave theory, the dynamic tensile bond stress time history curve of the coating-substrate interface is determined by the transmitted wave voltage signal of the semiconductor strain gauge, and its calculation formula is as follows: in For dynamic tensile bond stress; and These are the cross-sectional areas of the rod and the specimen, respectively. Let be the elastic modulus of the rod. For the sensitivity of the resistance strain gauge, For bridge pressure, The gain coefficient of the dynamic strain gauge connected to the resistance strain gauge; The loading rate is determined based on the maximum tangent slope of the rising segment of the dynamic tensile bond stress time history curve, and the dynamic tensile bond strength between the coating and the substrate is determined based on the peak value of the dynamic tensile bond stress time history curve.

8. The method according to claim 1, characterized in that, The substrate is metal, ceramic or rock, and the coating is an epoxy resin coating or a polyurethane coating.

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