What are the types of rubber wear?
Wear and tear
When rubber products are used on a rough surface, the local contact points on the rubber surface are cut and broken into small particles, which fall off the rubber surface and form wear (also known as abrasive wear or abrasion wear). When going slowly on a rough surface, this is the main kind of tread wear.
Rolling (crimping) wear
When the rubber touches the smooth surface, friction makes the slightly uneven spots on the vulcanizate surface deform, tear, and break, causing them to roll off the surface. It is especially important when the temperature is high, there is a lot of friction, and the speed of sliding is fast.
During repeated friction, the surface of the vulcanizate that is in contact with the friction surface is subjected to compression, shear, tension, and other deformations. This causes the rubber surface layer to wear down and form tiny cracks called “fatigue micro cracks.” When these cracks form, the surface of the material gets “micro-spalled.” The fatigue wear strength goes up as the rubber’s elasticity and pressure go up, and it goes down as the rubber’s tensile strength and fatigue performance go down.
How does the Akron abrasion tester work?
Let the sample rub against the grinding wheel at a certain angle and under a certain load, and then measure how much the sample has worn down after a certain distance. Then, the wear volume value is found by dividing (mass before sample test minus mass after sample test) by the sample’s density.
When two solid surfaces rub against each other, the surface material wears away. This is called abrasion.
How do different things affect the results of an Akron abrasion test on rubber?
The Akron abrasion test is an important way to test how well rubber materials and products can stand up to wear. Wear resistance is important for rubber materials and products because it has a big effect on how long they will last. So, the wear resistance of rubber materials and products is one of the most important reference indices at the start of a product’s life and after it has been used. The test results are strongly affected by the following: Sample
Preparing the samples is the most important and difficult part of an experiment. The accuracy of the test results is directly linked to how good the sample is. The long-term test shows that the length and thickness of the Akron wear test have a large effect on the results. In the test, the surface tension of the grinding surface was higher and the amount of wear was higher when the sample was shorter.
The wear amount is less the longer the sample is. Because of this, the length of the sample doesn’t always have the same effect on the results. Also, the amount of wear will go up as the sample thickness goes up, and down as the sample thickness goes down. These problems are also what cause the data to be different.
The grinding wheel
During the test, the grinding wheel is the abrasive, and its cutting force has a direct effect on how the test turns out. During use, a layer of sticky glue foam will build up on the surface, or it may even get stained with oil, which will change the test results. You should do a lot of things to make sure that your test formula is right. You should choose a test formula that works for your situation, calibrate your testing machine often, and learn how to change the cutting force of your grinding wheel at any time.
The sliding angle has a big effect on the results of the Akron abrasion test. In general, the angle between the shaft of the grinding wheel and the shaft of the rubber wheel should be 15 0.5°. Once the angle is passed, the amount of wear on the rubber also goes up in a straight line with the angle. This is mostly because the angle gets bigger and the rate of sliding gets faster, which leads directly to more wear.
Many tests show that as the test load goes up, the rubber will wear out faster. The reason for this is that in the test, we found that if the load goes up, the grinding wheel of the test equipment has to take on more forces. Since the forces are mutual, the increase in wear is a direct result of this. So, for the Akron abrasion test, it is suggested that the force the sample has to bear be kept at 26.7N 0.2N.
Besides the “sample,” what other things can have a direct effect on the test results? The Akron abrasion testing machine uses a grinding wheel that isn’t right for every kind of rubber. The composite standard grinding wheel must be chosen and calibrated based on what is being tested. Also, the force with which the grinding wheel cuts will have a big effect on the test results. During the test, there may be a layer of sticky foam or oil on the surface of the grinding wheel. These are the things we thought about when we did the experiment.
These are the main things that change the results of the Akron abrasion test for rubber. It takes a lot of research to figure out how wear-resistant rubber is. These tests must be based on science, take into account the effects of many different factors, and fully understand and calculate the possible deviation of test parameters. This way, we can get the wear resistance data we need quickly and accurately, use it to figure out how long a rubber will last, and make it work as well as possible.
How to test with an Akron abrasion tester
Rubber’s abrasion performance depends on how well it sticks together and how well it sticks to the friction surface. This includes the full effect of the substrate’s breaking strength, elongation at break, fatigue resistance, and viscoelasticity. You can’t say that abrasion is always caused by a certain property of matter.
The Din abrasion test of rubber is an example of abrasion, which is when tiny pieces of rubber wear away and fall off the surface due to friction. Under a certain load pressure, the rubber wheel of the rubber sole test piece makes a certain angle with the grinding wheel for rotary rolling friction. When sharp points rub against the surface of the grinding wheel, the rubber surface creates a localized area of high stress.
At the point where the stress is highest, the rubber is torn off strongly, making small pieces that fall off and cause wear. When the sharp points on the surface of the sand wheel are very sharp, the rubber surface will get scratched, and there will be marks that run parallel to the way the wheel slides. This is a sign of cutting wear and abrasion, and it is also a type of abrasion wear.
Prepare the sample
1) The width of the sample is 12.7 ± 0.2mm and the thickness is 3.2 ± 0.2mm. The surface of the sample with the length of (D + H) Π + 0-5mm shall be flat without cracks, impurities, etc. (Note: D is the diameter of the rubber wheel, h is the thickness of the sample, and Π is the Pi of 3.14)
2) The diameter of the rubber wheel is 68 mm, the thickness of the working surface is 12.7 ± 0.2mm, the hardness is 75-80 degrees (shore A type), and the diameter of the center hole shall comply with the diameter of the foot axle.
Start a test
1) Cut the sample into 12.7 ± 0.2mm wide and 3.2 ± 0.2mm thick, the length is the circumference of the rubber wheel. Polish both sides, and stick the sample to the rubber wheel with glue. During bonding, the sample shall not be subject to tension. During bonding, the joint should transition smoothly and butt at an angle of 45 degrees.
2) After bonding, the sample should be kept in the laboratory environment for no more than 8 hours.
3) Fix the bonded sample on the rubber wheel shaft, place the weight on the grinding wheel support, turn on the power supply of the electronic counter, turn on the power switch, adjust the preset number button to 600 revolutions (15–20 min for pre grinding time), start the motor, and start the pre grinding test.
4) After pre-grinding, remove it, brush the rubber chips, and weigh M1 (to 0.001 g) with an electronic balance.
5) Mount the weighed sample on the rubber wheel shaft, program the test times, set the preset number key to 1341 RPM (1.6km for the test mileage), start the motor, and begin the formal test.
6) Within 1 hour of the test times, remove the sample, clean the rubber chips with a brush, and weigh the weight M2 (to 0.001g) with an electric balance.
7) Replace the sample and continue the abrasion test.
Differences between the rubber Akron abrasion tester and the Bourne tester
One of the most important things about rubber products is that they don’t wear down easily. It directly affects the quality and life of things like tires, soles, rubber bearings, tape, and so on. The Akron abrasion tester method and the rotary roller abrasion tester method are both common ways to test wear resistance. However, because rubber products (especially tires) have strict requirements for the environment when they are being used, and because there are many unknown factors, the test results from these two methods don’t match up well with the real application. This makes it harder for people to agree with the test results.
ISO 23337:2016, which was put out by the international standards organization, says that the improved Lambert wear tester method is used to measure the wear resistance of rubber. This method can be set up for a variety of test conditions and is as close as possible to how the products are used in real life. All of the tests are done in the environmental box, which has a temperature that can be changed. This not only makes sure that the test conditions are always the same, but it also tests the wear resistance at high temperatures (like 60 °C), which can be close to the temperature of the tread rubber when the tire is being used. This means that the test results can be used in real life.
The Bourne abrasion tester lets you set slip rate, linear speed, load, and other abrasion conditions on its own. This method can be used to test different rubber products, especially tire rubber, in harsh environments. His test is based on the idea that wear happens when the disc-shaped rubber sample and the grinding wheel move in opposite directions at different linear speeds within a certain amount of time. Under the specified load, the disc-shaped rubber sample and the grinding wheel are tightly pressed against each other and turn at different linear speeds because they are driven by separate systems. Different speeds because the sample and the grinding wheel slip relative to each other, which causes the loss caused by wear. The test results show how much volume is lost per unit time or stroke and how much the wear index is different from the material that the test was done on.
What is the size of the Akron abrasion tester sample?
According to the measurement standard for wear resistance of vulcanized rubber, we can know:
The sample is in strip shape: the length is (68 + 3.2) л+ 0 ~ 5mm, 12.7 ± 0.2mm in width, and 3.2 ± 0.2mm in thickness. 68 is the diameter of the rubber wheel. The diameter of the rubber wheel is 68-1 mm, the thickness is 12.7 ± 0.2mm, and the hardness is 75-80 degrees (Shore A). The diameter of the central hole shall comply with the diameter of the rubber wheel rotating shaft.
After both sides of the sample have been polished, it will be stuck to the rubber wheel. During bonding, the sample shouldn’t be under any stress, and the bonding should be smooth.
Most of the time, the sample is made on a flat vulcanizer using an Akron wear test mold. If there is a rubber mixing machine in the lab, it can also be made by combining a punching machine and a rectangular cutter with the rubber mixing machine.