Sheet impact performance evaluation method based on energy equivalent model

Abstract

The invention discloses a thin plate impact performance evaluation method based on an energy equivalent model, belongs to the technical field of metal material impact performance testing, and aims at solving the technical problem that the impact performance of a thin plate with the thickness smaller than 5 mm lacks an effective detection and judgment standard. According to the method, an existing pendulum bob testing machine does not need to be transformed, a plurality of sheets to be tested are obtained through continuous sampling, the sheets are stacked to form a quasi-thick plate structure with the total thickness B larger than or equal to 7.5 mm and larger than or equal to 11 mm, the size of a stacked sample is 55 mm * 10 mm * B, and a V-shaped or U-shaped notch is formed in the middle of the stacked sample and fixed through an M3 screw; and performing an impact test by using a pendulum bob testing machine to obtain actually measured energy K, calculating equivalent absorption energy according to an energy equivalent formula KE = K * 10 / B, and further evaluating the impact performance of the thin plate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material impact performance test detection, and in particular to a thin plate impact performance evaluation method based on an energy equivalent model. BACKGROUND

[0002] Impact test is a key means to measure the resistance to fracture of materials under impact load, and the toughness of materials can be evaluated by testing, that is, the ability to absorb energy before fracture and to deform plastically. Materials with insufficient toughness are prone to sudden fracture when impacted, which can cause safety accidents. In particular, in low-temperature environments, most materials will exhibit increased brittleness and decreased toughness. Therefore, low-temperature impact test is crucial to ensuring the safety of products used in cold regions.

[0003] In existing relevant standards, GB / T 229-2020 "Metallic materials Charpy pendulum impact test method" specifies that the standard impact specimen size is 10 10 55, and V-shaped, U-shaped notched or unnotched designs can be used. When the material thickness is insufficient, small size specimens of 7.5mm, 5.0mm, 2.5mm can be selected, or other thickness specifications can be used according to the agreement. However, GBT 1591-2018 "Low alloy high strength structural steel" only specifies the impact energy determination value (not less than 75%, 50% of the standard specimen, respectively) of the 10mm x 7.5mm x 10mm or 10mm x 5mm x 55mm small size specimen, and does not specify the determination standard for 2.5mm and other thickness specifications, resulting in the inability to determine the eligibility of 2.5mm-<5.0mm thin strip steel, and the impact test and determination of thickness <2.5mm thin gauge strip steel are even lack of standard basis.

[0004] With the development of high-strength materials, thin plates with a thickness of <5.0mm are widely used in purlins, photovoltaic supports and other profiles, and the application environment is becoming increasingly complex. In particular, in power station projects in low-temperature and high-cold regions, materials need to pass low-temperature impact performance verification. However, the traditional impact test method is not suitable for thin plate materials, there is no corresponding impact specimen specification and detection method standard, and it is difficult to further process thin plates into general specifications and sizes, and the processing process may also cause changes in performance, which cannot accurately reflect the original impact performance of the materials. Therefore, there is an urgent need for a method that can accurately evaluate the impact performance of thin plates without modifying existing equipment. SUMMARY

[0005] To achieve the above purpose, the present application provides the following technical solutions: A thin plate impact performance evaluation method based on an energy equivalent model, comprising the following steps: a) Continuous sampling: continuously cutting multiple sample thin plates from the thin plate to be tested, the length of the sample thin plate being 55mm, the width being 10mm, and the thickness being ≤5mm; b) Laminated sample preparation: multiple sample sheets are laminated to form a laminated sample, the total thickness of the laminated sample is 4mm-11mm at B, the total thickness of the laminated sample is B, the size of the laminated sample is 55mm*10mm*B, and a V-shaped or U-shaped notch is formed at the center of the side of the laminated sample; c) Fixing treatment: the laminated sample is fixed by screws; d) Impact test: under different temperature conditions such as room temperature, high temperature or low temperature, a pendulum impact tester is used to test the fixed laminated sample, and the measured energy K is recorded; e) Energy calculation: the equivalent absorbed energy KE is calculated according to the energy equivalent formula KE=K*10 / B; f) Performance evaluation: whether the impact performance of the tested sheet meets the requirements is determined according to the equivalent absorbed energy KE.

[0006] Further, the total thickness B of the laminated sample in step b is 9-10mm.

[0007] Further, the temperature of the low-temperature environment in step e is-40℃.

[0008] Compared with the prior art, the beneficial effects of the present application mainly include: 1. High accuracy: the laminated sheet structure is constructed by laminating multiple sheets, which meets the plane strain assumption, eliminates the data fluctuation error of single sheet test, and significantly improves the stability of test data. Test verification shows that when the number of laminated sheets is 5-7, the single value impact work range is only 0.7J, and the 95% confidence interval is controllable; the single value impact work of laminated sheets of the same steel type is approximately consistent with the direct single sheet impact work, which can accurately reflect the original impact performance of the material.

[0009] 2. Strong universality: suitable for different steel types with a thickness of 1.5-3.0mm, such as SCS355DH-Q and SCS460E-Q, the test result is only related to the characteristics of the material itself, and is not limited by the thickness specification, solving the problem of no judgment standard for 2.5mm-5.0mm sheet.

[0010] 3. Simple operation: the sample preparation process is simple, the laminated sheets are fixed by M3 screws, the test steps are consistent with the traditional pendulum impact test, and it is easy to popularize and apply. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 Figure 1 is a graph of the relationship between the number of laminated sheets and the impact absorbed work of the sheet sample of embodiment 1 of the present application; Figure 2 Figure 2 is a graph of the relationship between the impact absorbed work of the average 1 sheet sample and the laminated sheets of the sheet sample of embodiment 1 of the present application. Figure 3 This is a graph showing the relationship between the single-value impact energy of the stacked thin plate specimens of the same steel grade and the impact energy of the single-piece impact of the thin plate specimen in Example 4 of the present invention. Figure 4 This is a schematic diagram of the thin plate sample before impact tests with different stacking numbers in an embodiment of the present invention; Figure 5 This is a schematic diagram of the impact test results of a thin plate sample with different stacking numbers in an embodiment of the present invention. Detailed Implementation

[0012] The technical solution of the present invention will be described in detail below with reference to specific test cases. This embodiment is only used to explain the present invention and is not intended to limit the scope of protection of the present invention.

[0013] Example 1: Impact Performance Test of Low-Strength Cold-Rolled Steel Sheet (JG-BLC) Test material: low-strength cold-rolled steel sheet JG-BLC, thickness 1.5mm.

[0014] Sample preparation process: Continuously cut samples to prepare stacked samples of 1 (thickness 1.5mm), 2 (thickness 3.0mm), 3 (thickness 4.5mm), 4 (thickness 6.0mm), 5 (thickness 7.5mm), 6 (thickness 9.0mm), and 7 (thickness 10.5mm). The dimensions of each sample combination are 55mm × 10mm × corresponding thickness, with a V-shaped notch in the middle, and fixed with M3 screws.

[0015] Test conditions: room temperature environment, impact test was conducted using a pendulum tester, each group of samples was tested 3 times, and the impact absorption energy was recorded.

[0016] Experimental results: As shown in Table 1, the impact absorption energy is linearly related to the thickness of the stack; the average impact absorption energy of a single piece in each group is 17.37 J, and the equivalent impact absorption energy of a 7-piece stack is 121.9 J; the range of single-piece test is 4.22 J, with large data fluctuations; when the number of stacked pieces is 5-7, the range is only 0.7 J, and the data stability is significantly improved.

[0017] Table 1. Impact Absorption Energy Test Results of Cold-Rolled Steel Sheets JG-BLC with Different Stacking Numbers Example 2: Low-Temperature Impact Performance Test of High-Strength Steel SCS355DH-Q (2.5mm) Test material: High-strength steel SCS355DH-Q, thickness 2.5mm.

[0018] Sample preparation process: Continuously cut samples to prepare 1 (thickness 2.5mm), 2 (thickness 5.0mm), 3 (thickness 7.5mm), and 4 (thickness 10.0mm) stacked samples respectively, with dimensions of 55mm×10mm×corresponding thickness, a U-shaped notch in the middle, and M3 screws for fixing.

[0019] Test conditions: -40℃ low temperature environment, pendulum impact test, 3 tests per group.

[0020] Test results: As shown in Table 2, the impact absorption energy is linearly related to the thickness of the laminate, and the range of single-value impact energy is only 2.4J, indicating good data stability. Through the equivalent formula calculation, the equivalent absorption energy of 4 laminates (10.0mm thick) can accurately reflect the low-temperature impact performance of the thin plate.

[0021] Table 2. Impact Absorption Energy Test Results of High-Strength Steel SCS355DH-Q (2.5mm) at -40℃ Example 3: Impact Performance Test of High-Strength Steel SCS460EH-Q (3.0mm) Test material: High-strength steel SCS460EH-Q, thickness 3.0mm.

[0022] Sample preparation process: Continuously cut samples to prepare 1 (3.0mm), 2 (6.0mm), and 3 (9.0mm) stacked samples with dimensions of 55mm × 10mm × corresponding thickness, V-shaped notch, and M3 screws for fixing.

[0023] Test conditions: -40℃ low temperature environment, pendulum impact test, 3 repetitions per group.

[0024] Experimental results: As shown in Table 3, the single-value impact energy range is only 0.3J, and the data stability is excellent, which verifies the applicability of this method to 3.0mm thick high-strength steel.

[0025] Table 3. Impact Absorption Energy Test Results of High-Strength Steel SCS460EH-Q (3.0mm) at -40℃ Example 4: Comparative Test of Multiple Production Batches of the Same Steel Grade Test material: SCS460E-Q steel, 2.5mm thick, 6 production batches.

[0026] Sample preparation process: Four samples were cut from each batch and stacked together (total thickness 10mm) to prepare stacked sample (55mm×10mm×10mm). At the same time, a single sample (2.5mm) was prepared as a control. V-shaped notches were made in all samples. The stacked samples were fixed with M3 screws.

[0027] Test conditions: room temperature environment, pendulum impact test, 3 repetitions per group.

[0028] Experimental results: As shown in Table 4, the single-value impact energy of the stacked impact is approximately consistent with the single-piece impact energy. The range of single-value impact energy of the six batches of stacked impact is 2.92J, and the range of single-piece impact energy is 2.67J. This verifies the accuracy and stability of the method and can effectively reflect the consistency of impact performance of thin plates from different production batches.

[0029] Table 4 Comparison of Impact Performance of SCS460E-Q (2.5mm) from Multiple Production Batches Example 5: Testing of thin plates of the same steel grade but different thicknesses Test material: SCS355DH-Q steel with thicknesses of 2.0mm, 2.3mm, 2.5mm, 3.0mm, 3.5mm, 4.0mm, and 5.0mm.

[0030] Sample preparation process: Prepare 1, 2, and 3 stacked specimens for thin plates with a thickness of 2.0-3.5mm respectively; prepare 1 and 2 specimens for thin plates with a thickness of 4.0mm and 5.0mm respectively (because the impact value changes greatly when the thickness is ≥4.0mm, it is more appropriate to use single specimen testing). The stacked specimen size is 55mm×10mm×corresponding thickness, with V-notch, and fixed with M3 screws.

[0031] Test conditions: room temperature environment, pendulum impact test, 3 repetitions per group.

[0032] Test results: As shown in Table 5, the single-value impact energy of the stacked impact of thin plates with a thickness of 2.0-3.5mm is close to that of a single sheet impact, and the impact absorption energy is linearly related to the thickness of the stack. The equivalent absorbed energy calculated by the equivalent formula can be used to unify the judgment standard. When the thickness is ≥4.0mm, the impact value changes significantly. Therefore, the applicable thickness of this method is limited to <4.0mm. For thicknesses of 4.0mm-5.0mm, single-sample testing is used.

[0033] Table 5 Impact Absorption Energy Test Results of SCS355DH-Q Thin Plates of Different Thicknesses This invention efficiently solves the industry pain point of impact performance testing for thin plates with a thickness of <5mm by using stacked preparation and energy equivalent calculation. It has the characteristics of not requiring modification of existing equipment, providing stable and accurate data, and being applicable to a wide range of scenarios. It can strongly support the engineering application of thin plates in complex environments such as low temperature and high cold, and has good practicality and promotion value.

Claims

1. A method for evaluating the impact performance of thin plates based on an energy equivalence model, characterized in that, Includes the following steps: a) Continuous sampling: Multiple sample plates are continuously cut from the plate to be tested. The length of the sample plate is 55 mm, the width is 10 mm, and the thickness is ≤5 mm. b) Preparation of stacked specimens: Multiple thin specimen plates are stacked to form a stacked specimen. The total thickness of the stacked specimen is 4 mm to 11 mm. The total thickness of the stacked specimen is B. The size of the stacked specimen is 55 mm × 10 mm × B. A V-shaped or U-shaped notch is opened at the center of the side of the stacked specimen. c) Fixing process: Secure the stacked sample pieces with screws; d) Impact test: Under different temperature conditions such as room temperature, high temperature or low temperature, a pendulum impact tester is used to conduct a pendulum impact test on the fixed stacked specimens, and the measured energy K is recorded; e) Energy calculation: Calculate the equivalent absorbed energy KE according to the energy equivalence formula, which is KE=K×10 / B; f) Performance evaluation: Determine whether the impact performance of the sheet to be tested meets the requirements based on the equivalent absorbed energy KE.

2. The method for evaluating the impact performance of thin plates based on an energy equivalence model according to claim 1, characterized in that, The total thickness B of the stacked sample in step b is 9-10 mm.

3. The method for evaluating the impact performance of thin plates based on an energy equivalence model according to claim 1, characterized in that, The temperature of the low-temperature environment in step e is -40℃.

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