A method for detecting bending stiffness of rubberized steel cord

Abstract

The application discloses a kind of detection methods of bending stiffness of rubber-coated steel cord, steel cord is vulcanized with rubber sheet, after vulcanization, stand for a period of time, then sample is cut into test sample symmetrically;Stiffness tester is used to test bending stiffness, before testing, use random standard sample to calibrate;Test sample is vertically placed in the center of clamp, left and right clamp rollers are adjusted to touch test sample lightly, and ensure that pendulum black line still points to 0°;Start stiffness tester, test sample deflects to 15° left and right in turn, and instrument automatically records left bending stiffness MoL and right bending stiffness MoR;According to MoL and MoR value, select appropriate weight according to weight usage table;The bending stiffness of rubber-coated steel cord is calculated according to formula.Compared with prior art, the method can significantly improve the accuracy and standardization level of steel cord bending stiffness data under rubber-coated state, and can also ensure that experimental data has good repeatability and reliability, so as to provide stable and effective detection means for product quality control and process optimization of steel cord.

Description

Technical Field

[0001] This invention relates to the field of steel cord testing technology, and more particularly to a method for testing the bending stiffness of rubber-coated steel cord. Background Technology

[0002] As a key reinforcing skeleton material for radial tires and other rubber products, the bending stiffness of steel cord is a core mechanical indicator that affects tire handling, rolling resistance and durability.

[0003] In actual tire manufacturing and application, steel cords are used in a rubber-coated state, and their true mechanical properties are a reflection of the overall steel wire and rubber composite system. Evaluating the bending stiffness in this state has the most direct guiding significance for predicting the actual performance of the finished tire and optimizing the rubber coating process. Existing national standard methods only apply to bare cord design and are completely unsuitable for stiffness testing of rubber-coated steel cords, constituting a significant gap in the current technical system.

[0004] Therefore, there is an urgent need in this field to invent a complete and dedicated method for testing the bending stiffness of rubber-coated steel cords. This method needs to fill the technological gaps in the entire process, from sample preparation and equipment adaptation to test standardization, in order to provide an evaluation method that can truly reflect the bending deformation resistance of steel cords under actual tire operating conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a method for testing the bending stiffness of rubber-coated steel cords. For the first time, a complete testing system covering the entire process of "rubber-coated sample vulcanization preparation - standard size cutting - dedicated stiffness testing" has been constructed. A complete methodological framework independent of bare wire testing has been established for rubber-coated steel cords, fundamentally solving the problem that existing standards cannot be used for evaluating the rubber coating condition.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for testing the bending stiffness of rubber-coated steel cord includes the following steps:

[0008] Step 1: Vulcanize the steel cord and rubber sheet to prepare a rubber-coated steel cord sample with a rubber layer thickness of 2-5 mm, a width of 10-15 mm, and a length of 140-200 mm. After vulcanization, let it stand for a period of time, and then cut the sample symmetrically into two sections with a length of about 70-100 mm. A total of three groups of six samples are prepared.

[0009] Step 2: Use a stiffness tester to test the bending stiffness. Before testing, use a random standard sample for calibration. After calibration, adjust the base knob to align the black line in the middle of the pendulum with the 0° mark on the inner dial.

[0010] Step 3: Open the clamps symmetrically, place the sample vertically in the center of the clamps, and adjust the clamp knob to hold the sample firmly; adjust the left and right clamping rollers to lightly touch the sample, with the right clamping roller turning back 1 / 4 turn, and ensure that the black line of the pendulum still points to 0°;

[0011] Step 4: Start the automatic testing program of the stiffness tester. The sample is deflected to the left and right by 15° in sequence. The instrument automatically records the bending stiffness MoL to the left and the bending stiffness MoR to the right.

[0012] Step 5: Select appropriate weights according to the MoL and MoR values ​​from the weight usage table, so that the readings are within the range of 10 to 80 T.SU; repeat the above steps for the remaining five samples to obtain five sets of valid data.

[0013] Step 6: Calculate the bending stiffness of the rubber-coated steel cord using the following formula, accurate to 0.1 TSU:

[0014] , n = magnification factor.

[0015] A further aspect of the present invention is that the vulcanization and composite curing temperature of the steel cord and the rubber sheet is set at 140℃~160℃, pressure ≥3.5 MPa, and time at 20min~60min.

[0016] A further aspect of the present invention is that the rubber-coated steel cord sample is vulcanized and left to stand for no less than 16 hours.

[0017] A further aspect of the present invention is that the stiffness tester is model Taber V5.

[0018] A further aspect of the present invention is that the stiffness meter is calibrated using a 3x0.24 / 9x0.225 CC HT random standard sample before testing. The standard sample has a nominal stiffness of 70.4 TSU and an allowable deviation of ±3 TSU.

[0019] The beneficial effects of this invention are:

[0020] First, the method for testing the bending stiffness of coated steel cords in this invention fills a gap in testing standards, enables direct evaluation under coated conditions, and establishes for the first time a complete and dedicated method for testing the bending stiffness of coated steel cords, providing the industry with a crucial new testing basis.

[0021] Secondly, the method for testing the bending stiffness of rubber-coated steel cord in this invention realistically simulates working conditions, and the results have greater engineering guidance value. By introducing a standardized vulcanization sample preparation process, the sample can truly reproduce the "steel wire-rubber" composite structure of steel cord in the tire. The measured bending stiffness can more accurately reflect the product's resistance to bending deformation in actual use, significantly improving the guiding significance of the test results for product design, process optimization, and quality control.

[0022] Third, the method for testing the bending stiffness of coated steel cord of the present invention is standardized throughout the entire process, ensuring data reliability and comparability. From sample specifications, preparation process, equipment operation to data processing, a systematic standard has been implemented, which greatly reduces human error and ensures that the test results have excellent repeatability and comparability among different batches and different operators.

[0023] Fourth, the method for testing the bending stiffness of coated steel cord of the present invention is highly practical and easy to promote and apply. The testing method is based on the universal Taber V5 stiffness tester and is adapted by optimizing the clamping, zeroing and weight selection strategies. It does not require modification of core equipment, is easy to implement and promote under existing laboratory conditions, and has high practicality and economy. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the stiffness meter of the present invention.

[0025] Figure 2 This is a schematic diagram of the test sample of the present invention.

[0026] In the figure: 1-stiffness tester, 101-clamp, 102-left clamping roller, 103-right clamping roller, 2-sample. Detailed Implementation

[0027] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1:

[0029] Steel cord specifications: 1+5×0.345 UT

[0030] (1) A composite vulcanization of 1+5×0.345 UT steel cord and rubber sheet was carried out at a vulcanization temperature of 151℃, a pressure of 15MPa, and a time of 40min to prepare a rubber-coated steel cord sample with a rubber layer thickness of 3mm, a width of 12.5mm, and a length of 165mm. After vulcanization, the sample was left to stand at room temperature for more than 16 hours, and then the sample was symmetrically cut into two sample 2s with a length of about 75mm along the center using an abrasive wheel cutter. Figure 2 As shown, there are three groups in total, with two test samples in each group.

[0031] (2) The Taber V5 stiffness tester was used for testing. Before testing, the equipment was calibrated using random standard samples (3×0.24 / 9×0.225CC HT). The bending stiffness of the standard samples was 71.2 TSU, which was within the control range. After calibration, the base knob was adjusted so that the black line in the middle of the pendulum was aligned with the 0° scale line on the inner dial.

[0032] (3) For example Figure 1As shown, symmetrically open the clamp 101, take one of the samples 2 and place it vertically in the center of the clamp 101. Adjust the knob of the clamp 101 to make the sample 2 firmly clamped and not loose. Adjust the left clamping roller 102 and the right clamping roller 103 in sequence to lightly touch the sample 2. After the right clamping roller 103 makes contact, turn it back 1 / 4 turn to ensure that the black line in the middle of the pendulum still points to the 0° mark on the inner dial.

[0033] (4) Start the automatic testing program of the equipment. First, deflect the sample 2 to the left by 15° and record the left bending stiffness value MoL; then return to the center and deflect to the right by 15° and record the right bending stiffness value MoR.

[0034] (5) Based on the initial measured values ​​of MoL and MoR, select appropriate weights according to the instrument weight usage table. In this example, the initial reading is in the range of >80T.SU, so the "500" weight is selected to make the reading fall into the optimal measurement range of 10–80T.SU. At this time, the instrument reading is the display value after magnification by 5 times. Repeat steps (3) to (4) for the remaining five samples 2 to complete the test of all six samples 2.

[0035] (6) The five sets of valid data obtained from the test are as follows (unit: TSU, all readings after magnification of 5 times):

[0036] Group 1: ,

[0037] Group 2: ,

[0038] Group 3: ,

[0039] Group 4: ,

[0040] Group 5: ,

[0041] (7) Calculate the bending stiffness of the rubber-coated steel cord using the following formula, with the result accurate to 0.1 TSU:

[0042]

[0043] (8) Comparative experiment: Prepare samples according to the standard for testing the bending stiffness of uncoated steel cord and test their bending stiffness.

[0044] Uncoated steel cord:

[0045]

[0046] Example 2:

[0047] Steel cord specifications: 3x0.20 + 6x0.35 HT

[0048] (1) 3x0.20+6x0.35 HT steel cord and rubber sheet were composite vulcanized at a vulcanization temperature of 151℃, a pressure of 15MPa, and a time of 40min to prepare a rubber-coated steel cord sample with a rubber layer thickness of 3mm, a width of 12.5mm, and a length of 165mm. After vulcanization, the sample was left to stand at room temperature for more than 16 hours, and then the sample was symmetrically cut into two sample 2s with a length of about 75mm along the center using an abrasive wheel cutter. Figure 2 As shown, there are three groups in total, with two test samples in each group.

[0049] (2) The Taber V5 stiffness tester was used for testing. Before testing, the equipment was calibrated using random standard samples (3×0.24 / 9×0.225CC HT). The bending stiffness of the standard samples was 70.5 TSU, which was within the control range. After calibration, the base knob was adjusted so that the black line in the middle of the pendulum was aligned with the 0° scale line on the inner dial.

[0050] (3) For example Figure 1 As shown, symmetrically open the clamp 101, take one of the samples 2 and place it vertically in the center of the clamp 101. Adjust the knob of the clamp 101 to make the sample 2 firmly clamped and not loose. Adjust the left clamping roller 102 and the right clamping roller 103 in sequence to lightly touch the sample 2. After the right clamping roller 103 makes contact, turn it back 1 / 4 turn to ensure that the black line in the middle of the pendulum still points to the 0° mark on the inner dial.

[0051] (4) Start the automatic testing program of the equipment. First, deflect the sample 2 to the left by 15° and record the left bending stiffness value MoL; then return to the center and deflect to the right by 15° and record the right bending stiffness value MoR.

[0052] (5) Based on the initial measured values ​​of MoL and MoR, select appropriate weights according to the instrument weight usage table. In this example, the initial reading is in the range of >80T.SU, so the "500" weight is selected to make the reading fall into the optimal measurement range of 10–80T.SU. At this time, the instrument reading is the display value after magnification by 5 times. Repeat steps (3) to (4) for the remaining five samples 2 to complete the test of all six samples 2.

[0053] (6) The five sets of valid data obtained from the test are as follows (unit: TSU, all readings after magnification of 5 times):

[0054] Group 1: ,

[0055] Group 2: ,

[0056] Group 3: , 70.4

[0057] Group 4: , 62.1

[0058] Group 5: ,

[0059] (7) Calculate the bending stiffness of the rubber-coated steel cord using the following formula, with the result accurate to 0.1 TSU:

[0060]

[0061] (8) Comparative experiment: Prepare samples according to the standard for testing the bending stiffness of uncoated steel cord and test their bending stiffness.

[0062] Uncoated steel cord:

[0063]

[0064] Example 3:

[0065] Steel cord specifications: 4+3x0.33 ST

[0066] (1) 4+3x0.33 ST steel cord and rubber sheet were composite vulcanized at a vulcanization temperature of 151℃, a pressure of 15MPa, and a time of 40min to prepare a rubber-coated steel cord sample with a rubber layer thickness of 3mm, a width of 12.5mm, and a length of 165mm. After vulcanization, the sample was left to stand at room temperature for more than 16 hours, and then the sample was symmetrically cut into two sample 2s with a length of about 75mm along the center using an abrasive wheel cutter. Figure 2 As shown, there are three groups in total, with two test samples in each group.

[0067] (2) The Taber V5 stiffness tester was used for testing. Before testing, the equipment was calibrated using random standard samples (3×0.24 / 9×0.225CC HT). The bending stiffness of the standard samples was 71.5 TSU, which was within the control range. After calibration, the base knob was adjusted so that the black line in the middle of the pendulum was aligned with the 0° scale line on the inner dial.

[0068] (3) For example Figure 1As shown, symmetrically open the clamp 101, take one of the samples 2 and place it vertically in the center of the clamp 101. Adjust the knob of the clamp 101 to make the sample 2 firmly clamped and not loose. Adjust the left clamping roller 102 and the right clamping roller 103 in sequence to lightly touch the sample 2. After the right clamping roller 103 makes contact, turn it back 1 / 4 turn to ensure that the black line in the middle of the pendulum still points to the 0° mark on the inner dial.

[0069] (4) Start the automatic testing program of the equipment. First, deflect the sample 2 to the left by 15° and record the left bending stiffness value MoL; then return to the center and deflect to the right by 15° and record the right bending stiffness value MoR.

[0070] (5) Based on the initial measured values ​​of MoL and MoR, select appropriate weights according to the instrument weight usage table. In this example, the initial reading is in the range of >80T.SU, so the "500" weight is selected to make the reading fall into the optimal measurement range of 10–80T.SU. At this time, the instrument reading is the display value after magnification by 5 times. Repeat steps (3) to (4) for the remaining five samples 2 to complete the test of all six samples 2.

[0071] (6) The five sets of valid data obtained from the test are as follows (unit: TSU, all readings after magnification of 5 times):

[0072] Group 1: ,

[0073] Group 2: 93.1,

[0074] Group 3: , 96.3

[0075] Group 4: , 88.0

[0076] Group 5: ,

[0077] (7) Calculate the bending stiffness of the rubber-coated steel cord using the following formula, with the result accurate to 0.1 TSU:

[0078]

[0079] (8) Comparative experiment: Prepare samples according to the standard for testing the bending stiffness of uncoated steel cord and test their bending stiffness.

[0080] Uncoated steel cord:

[0081] .

[0082] Wherein, 1T.SU=97.974×10⁻³N / mm.

[0083] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for testing the bending stiffness of rubber-coated steel cord, characterized in that, Includes the following steps: Steel cord and rubber sheet were vulcanized to prepare rubber-coated steel cord samples with a rubber layer thickness of 2-5 mm, a width of 10-15 mm, and a length of 140-200 mm. After vulcanization, the samples were left to stand for a period of time and then symmetrically cut into two sections of about 70-100 mm in length, and a total of three groups of six test samples were prepared. Bending stiffness was tested using a stiffness tester. Before testing, the tester was calibrated using a random standard sample. After calibration, the base knob was adjusted so that the black line in the middle of the pendulum was aligned with the 0° mark on the inner dial. Open the clamps symmetrically, place the sample vertically in the center of the clamps, and adjust the clamp knobs to hold the sample securely. Adjust the left and right clamping rollers to lightly touch the sample, with the right clamping roller turning back 1 / 4 turn, and ensure that the black line of the pendulum still points to 0°. Start the automatic testing program of the stiffness meter. The sample is deflected to the left and right by 15° in sequence. The instrument automatically records the bending stiffness MoL to the left and the bending stiffness MoR to the right. Based on the MoL and MoR values, select appropriate weights from the weight usage table to ensure that the readings are within the range of 10–80 T.SU; repeat the above steps for the remaining five samples to obtain five sets of valid data. Calculate the bending stiffness of the rubber-coated steel cord using the following formula, with the result accurate to 0.1 TSU: , n = magnification factor.

2. The method for detecting the bending stiffness of rubber-coated steel cord as described in claim 1, characterized in that: The vulcanization process for the steel cord and rubber sheet is set at a temperature of 140℃~160℃, a pressure of ≥3.5 MPa, and a duration of 20min~60min.

3. The method for testing the bending stiffness of rubber-coated steel cord as described in claim 1, characterized in that: The rubber-coated steel cord samples were vulcanized and left to stand for no less than 16 hours.

4. The method for testing the bending stiffness of rubber-coated steel cord as described in claim 1, characterized in that: The stiffness tester is a Taber V5.

5. The method for testing the bending stiffness of rubber-coated steel cord as described in claim 1, characterized in that: The stiffness tester was calibrated using 3x0.24 / 9x0.225 CC HT random standard samples before testing. The standard sample had a nominal stiffness of 70.4 TSU and an allowable deviation of ±3 TSU.

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