Tire sidewall rubber anti-aging ability test device and test method thereof

Abstract

The present application relates to the technical field of tire sample detection, and particularly relates to a tire sidewall rubber anti-aging capability test equipment and a test method thereof. The tire sidewall rubber anti-aging capability test equipment comprises an aging box, a gas generator, two sets of clamping devices, an upper pushing rod, a lower pushing rod and an ultraviolet light source. The equipment provides more actual working conditions of the sidewall rubber, can realize rapid aging and crack of the sidewall sample, the test period can be shortened to one day, and the formula engineer can quickly understand whether the anti-aging system of the sidewall formula is reasonable. Of course, the test conditions of the present application can be adjusted, for example, the ultraviolet light source can be turned off, the ozone and oxygen concentration can be reduced, and the anti-aging capability of the sidewall formula to a single factor can be understood.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tire sample detection, and particularly relates to a tire sidewall rubber anti-aging capability test device and a test method thereof. BACKGROUND

[0002] During use, cracks will appear on the tire side, which is called alligatoring in the profession. This is due to the influence of heat, oxygen, ozone, light, mechanical stress and other external factors on the tire side during use; the mechanical properties such as tensile strength, elongation at break, elasticity and other indicators will decrease and gradually lose the value of the rubber aging. The specific influencing mechanism is as follows:

[0003] Oxygen: Oxygen attacks the weak links such as unsaturated double bonds of rubber molecular chains to generate free radicals, and then free radical chain lock reactions occur between the free radicals and rubber molecules, causing the rubber molecular chains to break or crosslink, which is one of the important reasons for causing rubber aging.

[0004] Ozone: The chemical activity of ozone is much higher than that of oxygen, and it is more destructive. It also causes the rubber molecular chain to break, but the effect of ozone on rubber is different depending on whether the rubber is deformed. The ozone aging of rubber first appears in the surface layer of the product, and is particularly prone to occur at the stress concentration or the interface between the matching particles and the rubber. After the ozone aging of the rubber without stretching, a hard and brittle film similar to a frost-like white film is formed on the surface. However, ozone cracking occurs under the action of stress or strain, and the crack direction of the ozone cracking is perpendicular to the stress direction. Especially when used under dynamic conditions, the film is more likely to break continuously to expose a fresh surface, causing the ozone aging to continuously develop in depth until complete destruction. The cracking time of various rubbers is significantly shortened as the ozone concentration increases, but the degree of difference varies depending on the type of rubber. In addition, the ozone concentration also affects the growth rate of the crack.

[0005] Heat: The heat stability of rubber mainly depends on its chemical composition and structure, but in the usual use environment, the basic role of heat is mainly to activate the oxidation reaction, thereby accelerating the aging of the rubber, that is, the heat oxygen aging we know. This is a common aging phenomenon. In the presence of oxygen, the aging results of various rubbers are different.

[0006] Light: Especially the ultraviolet part of sunlight, due to its short wavelength and high energy, it can not only directly cause the rupture and crosslinking of the rubber molecular chain, but also can generate free radicals in the rubber, thereby triggering a free radical chain reaction. Especially in the presence of oxygen, the aging process will be greatly accelerated, that is, photo-oxidative aging occurs. The difference between photo-oxidative aging and thermal-oxidative aging is that photo-oxidative aging mainly occurs on the surface of the rubber product, causing the product to crack and gradually penetrate into the interior.

[0007] Mechanical stress: mechanical stress repeatedly causes part of the molecular chain to be torn, which is particularly prominent when the rubber is in periodic deformation. The direct generation of free radicals by the rupture of the rubber molecular chain initiates the aging of the rubber. This mainly includes two processes: one is the generation of free radicals by the rupture of the rubber molecular chain caused by mechanical stress, which further initiates aging, and the other is the free radicals generated by mechanical stress under the action of oxygen, which initiates the oxidation chain reaction and accelerates the aging process of the rubber. This aging phenomenon is the "fatigue aging" we often encounter.

[0008] The actual use of the tire sidewall is subjected to tensile and compressive alternating loads under pre-strain. The existing tire aging test is to inflate the tire and place it in an aging oven or to place the vulcanized test piece in an aging oven and stand still. The test time is 35 days, which can represent the thermal-oxidative aging of the rubber under tensile stress. The test piece flex fatigue test is that one side of the thinnest part of the test piece is subjected to alternating tensile stress, and the other side is subjected to alternating compressive deformation. The test time is about 7-10 days, which can represent the crack generation of the test piece under alternating deformation. However, the above tests cannot reflect the actual use of the sidewall rubber. SUMMARY

[0009] In order to overcome the single test condition of the existing test and shorten the test period, the purpose of the present application is to provide a tire sidewall rubber anti-aging ability test equipment, which provides more actual working condition conditions of the sidewall rubber, can realize the rapid aging and crack of the sidewall test piece, and the test period can be shortened to one day, so that the formula engineer can quickly understand whether the anti-aging system of the sidewall formula is reasonable.

[0010] In order to achieve the above purpose, the following technical solutions are adopted in the present application:

[0011] A tire sidewall rubber anti-aging ability test equipment, the equipment comprises:

[0012] An aging oven body, the aging oven body is provided with a heating constant temperature device and can be kept sealed during the test;

[0013] A gas generator, the gas generator is arranged on one side of the aging oven body and communicates with the aging oven body, and the gas generator can mix oxygen, ozone and nitrogen and charge into the aging oven;

[0014] Two sets of clamping devices, the two sets of clamping devices are arranged in the aging oven body and located on the left and right sides of the sidewall rubber test sample respectively, and the two sets of clamping devices are used for clamping the two ends of the sidewall rubber test sample and can provide tension to the sidewall rubber test sample;

[0015] The upper and lower poking rods are arranged in a cross shape with the clamping device, and are respectively located on the upper and lower sides of the middle part of the sidewall rubber sample.

[0016] The ultraviolet light source is located at a position where the sidewall rubber sample can be deformed.

[0017] Preferably, the ultraviolet light source is in a strip shape, and the strip-shaped ultraviolet light source is arranged at the center position of the lower surface of the upper poking rod and the upper surface of the lower poking rod.

[0018] Preferably, the lower surface of the upper poking rod and the upper surface of the lower poking rod are both arc surfaces.

[0019] Preferably, the clamping device comprises a pneumatic cylinder and a clamp, and the clamp is provided with a clamping opening for the sidewall rubber sample.

[0020] Preferably, the driving device comprises a driving motor, a gear and a rack, and the driving motor drives the upper or lower poking rod to move through the gear and the rack.

[0021] Further, the application also discloses a test method for the anti-aging capability of the sidewall rubber of a tire, which adopts the device and comprises the following steps.

[0022] 1) Firstly, the finite element calculation is performed on the sidewall strain of the tire under the tire inflation loading condition, and the stroke of the two poking rods is determined according to the calculation;

[0023] 2) The vulcanized sidewall rubber sample is fixed on the clamping device, the clamping device is tensioned to make the sidewall rubber sample bear an initial tensile strain, the tensioning force is adjustable and remains unchanged after adjustment, and the test period is short when the tensioning force is large;

[0024] 3) The aging oven is heated to the actual temperature of the sidewall surface near the mouth of the tire in actual use;

[0025] 4) The gas generating device is used to mix oxygen, ozone and nitrogen to fill the aging oven, and the gas concentration can be adjusted according to the test period requirement, and the test piece is aged faster when the oxygen and ozone concentrations are high;

[0026] 5) The ultraviolet light source embedded in the poking rod is turned on to irradiate the deformation position of the sidewall rubber sample, so as to accelerate the aging of the rubber;

[0027] 6) The driving device connected to the upper and lower poking rods is started, the rolling frequency of the tire is calculated according to the speed of the commonly used working condition of the tire, the frequency of the upward and downward movement of the poking rod is designed according to the calculated frequency, the frequency of the alternating load of the sidewall is simulated, the upward and downward stroke ratio of the upper and lower poking rods is input according to the data calculated in the first step, and the stroke can be appropriately increased or reduced to change the test period.

[0028] As preferred, the stroke of the upper push rod and the lower push rod in step 1) is 70mm up and 40mm down in the original state balanced position.

[0029] As preferred, the middle part of the sidewall rubber sample in step 2) is provided with a thin part, the thickness of the sidewall rubber sample is h, and the thickness of the thin part is 0.4-0.7h.

[0030] As preferred, the thickness of the sidewall rubber sample in step 2) is 5-8mm, and the thickness of the thin part is 3-5mm.

[0031] As preferred, the temperature of the aging oven in step 3) is 60-70°.

[0032] The device provides more actual working conditions of the sidewall rubber, can realize the rapid aging of the sidewall sample to produce cracks, the test period can be shortened to one day, and the formula engineer can quickly understand whether the sidewall formula anti-aging system is reasonable. Of course, the test conditions of the present application can be adjusted, for example, the ultraviolet light source can be turned off, the ozone and oxygen concentration can be reduced, and the ability of the sidewall formula to resist single factor aging can be understood. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The figure is a structural schematic diagram of the present application.

[0034] Figure 2 The figure is a structural schematic diagram of the upper push rod and the lower push rod.

[0035] Figure 3 The figure is a schematic diagram of the deformation of the sidewall rubber sample after the upper push rod and the lower push rod go up and down.

[0036] Figure 4 The figure is a diagram of the sidewall strain under the tire inflation loading condition calculated by the finite element method. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be described below, and the embodiments of the present application will be described in detail, and then the present application will be further explained. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments. Given the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0038] As Figure 1The device shown is a tire sidewall rubber anti-aging ability testing device. The device includes: an aging chamber 1, a gas generator 2, two sets of clamping devices, an upper lever 5, a lower lever 6, and an ultraviolet light source 9. The aging chamber 1 is equipped with a heating and temperature control device and can maintain a sealed environment during the test. The gas generator 2 is located on one side of the aging chamber 1 and connected to it. The gas generator 2 can mix oxygen, ozone, and nitrogen and fill the aging chamber. The two sets of clamping devices are located inside the aging chamber 1 and are positioned on the left and right sides of the sidewall rubber sample 8, respectively. The two sets of clamping devices are used to clamp both ends of the sidewall rubber sample 8 and provide tension to the sample. Figure 2 As shown, the upper lever 5 and the lower lever 6 are arranged in a cross shape with the clamping device, located on the upper and lower sides of the middle of the sidewall rubber sample 8, respectively. The levers 5 and 6 are connected to driving devices, which can drive the lower lever 6 to press the sidewall rubber sample 8 upwards, or drive the upper lever 5 to press the sidewall rubber sample 8 downwards. The lower surface of the upper lever 5 and the upper surface of the lower lever 6 are both arc-shaped surfaces. The ultraviolet light source 9 is strip-shaped and positioned at the center of the lower surface of the upper lever 5 and the upper surface of the lower lever 6.

[0039] like Figure 1 As shown, the clamping device includes a cylinder 3 and a clamp 4, with the clamp 4 having a clamping opening for the tire sidewall rubber sample 8. The driving device includes a drive motor, gears, and a rack, with the drive motor driving the upper lever 5 or the lower lever 6 to move via the gears and rack.

[0040] A method for testing the anti-aging ability of tire sidewall rubber using the above-mentioned equipment, the method comprising the following steps:

[0041] 1. First, the finite element method is used to calculate the tire sidewall strain under the tire inflation and loading conditions, as follows: Figure 4 The maximum tensile strain in the sidewall area near the bead is approximately 3.9e-2 at the far end of the tire contact patch, and the compressive strain is approximately 7e-2 at the contact patch end. According to calculations, the travel of the two levers is approximately 4 / 7. For example, it can be determined that the two levers move upward 70mm and downward 40mm from their original balanced position.

[0042] 2. Take the vulcanized sidewall rubber sample 8 and fix it in the clamping device. The thickness of the sidewall rubber sample 8 is 6.3mm and the thickness of the thin part is 4mm. The vulcanized sidewall specimen is fixed at the cylinders on both sides. The two cylinders are used to tension the specimen so that it is subjected to the initial tensile strain. The tension force is adjustable and remains unchanged after adjustment. When the tension force is large, the test cycle is short.

[0043] 3. The aging chamber is heated to 65°C, which matches the actual temperature of the tire sidewall surface near the bead during actual tire use;

[0044] 4. The gas generating device mixes oxygen, ozone and nitrogen into the aging box, and the gas concentration can be adjusted according to the test period requirement, and the aging speed of the test piece is fast when the oxygen and ozone concentration is high;

[0045] 5. Turn on the ultraviolet light source 9 embedded in the dial lever to irradiate the deformation position of the sidewall rubber test sample 8, and accelerate the rubber aging;

[0046] 6. Start the driving device connected to the upper dial lever 5 and the lower dial lever 6, calculate the rolling frequency of the tire according to the speed of the commonly used working condition of the tire, for example, the tire with a rolling radius of 537mm, about 5 turns per second at 60Km / h working condition. According to the calculated frequency, design the frequency of the dial lever up and down, simulate the frequency of the sidewall alternating load; The up and down stroke ratio of the upper dial lever 5 and the lower dial lever 6 is input according to the data calculated in the first step, and the stroke can be appropriately increased or reduced to change the test period, such as shown in the formula: Figure 3

[0047] Through the above method, the sidewall test piece can be quickly aged to produce cracks, and the test period can be shortened to one day, so that the formula engineer can quickly understand whether the sidewall formula anti-aging system is reasonable. The test device test condition can be adjusted, for example, the ultraviolet light source can be turned off, the ozone and oxygen concentration can be reduced, and the ability of the sidewall formula to resist single factor aging can be realized.

[0048] The above is the description of the embodiments of the present application, through the above description of the disclosed embodiments, the person skilled in the art can realize or use the present application. Various modifications of these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.​

Claims

1. A tire sidewall rubber anti-aging ability test apparatus characterized by, The device comprises: an aging box (1) provided with a heating constant temperature device and capable of keeping sealed during the test; a gas generator (2) arranged on one side of the aging box (1) and communicated with the aging box (1), the gas generator (2) being capable of mixing oxygen, ozone and nitrogen and filling into the aging box; two sets of clamping devices arranged in the aging box (1) and respectively located on the left and right sides of the sidewall rubber sample (8), the two sets of clamping devices being used for clamping the two ends of the sidewall rubber sample (8) and capable of providing tension to the sidewall rubber sample (8); an upper pushing rod (5) and a lower pushing rod (6), the lower surface of the upper pushing rod (5) and the upper surface of the lower pushing rod (6) being arc surfaces; the upper pushing rod (5) and the lower pushing rod (6) being arranged in a cross shape with the clamping devices and respectively located on the upper and lower sides of the middle part of the sidewall rubber sample (8), the upper pushing rod (5) and the lower pushing rod (6) being respectively connected with driving devices, the driving devices being capable of driving the lower pushing rod (6) to press the sidewall rubber sample (8) upward or driving the upper pushing rod (5) to press the sidewall rubber sample (8) downward; an ultraviolet light source (9) located at a position where the sidewall rubber sample (8) can be deformed, the ultraviolet light source (9) being in a strip shape, the strip-shaped ultraviolet light source (9) being arranged at the center position of the lower surface of the upper pushing rod (5) and the upper surface of the lower pushing rod (6).

2. The apparatus according to claim 1, wherein The clamping device comprises a pneumatic cylinder (3) and a clamp (4), the clamp (4) being provided with a clamping opening of the sidewall rubber sample (8).

3. The device for testing the anti-aging ability of a tire sidewall rubber according to claim 1, wherein The driving device comprises a driving motor, a gear and a rack, the driving motor driving the upper pushing rod (5) or the lower pushing rod (6) to move through the gear and the rack.

4. A method for testing the anti-aging ability of a tire sidewall rubber, characterized by, The method adopts the device of any one of claims 1-3 and comprises the following steps: 1) firstly, the finite element calculation is performed on the sidewall strain of the tire under the tire inflation loading condition, and the stroke of the two pushing rods is determined according to the calculation; 2) the vulcanized sidewall rubber sample (8) is fixed to the clamping device, the clamping device tensions the sidewall rubber sample (8) to make it bear the initial tensile strain, the tension is adjustable and remains unchanged after adjustment, and the test period is short when the tension is large; 3) the aging box is heated to the actual temperature of the sidewall surface near the mouth of the tire during actual use; 4) the gas generating device mixes oxygen, ozone and nitrogen and fills into the aging box, the gas concentration can be adjusted according to the test period requirement, and the test piece ages faster when the oxygen and ozone concentrations are high; 5) the ultraviolet light source (9) embedded in the pushing rod is turned on to irradiate the deformed position of the sidewall rubber sample (8) to accelerate the rubber aging; 6) the driving device connected with the upper pushing rod (5) and the lower pushing rod (6) is started, the rolling frequency of the tire is calculated according to the speed of the commonly used working condition of the tire, the frequency of the up-and-down movement of the pushing rod is designed according to the calculated frequency, the frequency of the alternating load of the sidewall is simulated; the up-and-down stroke ratio of the upper pushing rod (5) and the lower pushing rod (6) is input according to the data calculated in the first step, and the stroke can be appropriately increased or reduced to change the test period.

5. The method of claim 4, wherein, In step 1), the stroke of the upper pushing rod (5) and the lower pushing rod (6) is 70mm upward and 40mm downward from the original balanced position.

6. The method of claim 4, wherein, The middle part of the sidewall rubber test sample (8) in step 2) is provided with a thin part, the thickness of the sidewall rubber test sample (8) is h, and the thickness of the thin part is 0.4-0.7h.

7. The method of claim 6, wherein, The thickness of the sidewall rubber test sample (8) in step 2) is 5-8mm, and the thickness of the thin part is 3-5mm.

8. The method of claim 4, wherein, The temperature of the aging oven in step 3) is 60-70℃.

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