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Teknikmobil.com-This time we will discuss the types of friction and wear that occur in cars, namely, firstly, mechanical friction and dry friction. Apart from mechanical friction and dry friction, there are at least several other important things that we will present in part 2 and part 3 that occur in a car. As we all know, the lubrication system has a main function. The main function of lubrication is to reduce wear and tear due to the six types of friction that occur in various positions in the car.
Gambar-3a-4-300×125.jpg The automotive industry’s dependence on lubrication systems is very high ©pcs-instruments
Friction has a concept that is very easy to understand. When people hear the word friction, the meaning of the word immediately occurs to them. Each type of friction provides benefits and disadvantages. For example, the friction that occurs on our footwear with the road we walk on. Provides benefits so that we can move forward, but if the friction is reduced (slippery) to a very small level, it will be difficult for us to move forward and will even fall. The same thing happens to the four wheels of the car when the vehicle is moving. Another example, someone takes advantage of friction to produce fire, for example by rubbing two pieces of wood together continuously.
Mechanical Friction
Various types of bearings in a car experience mechanical friction©bearingsdubai.blogspot
The first type of friction is mechanical friction. In this case, we will consider friction as an undesirable thing that arises from the rough surface of two objects in contact with each other. Friction forces absorb force and cause wear, which will result in various devices in the car needing maintenance.
To reduce mechanical friction between surfaces, we can introduce something called lubrication. The level of lubrication can reduce friction which not only depends on the choice of lubricant, but also on the situation and circumstances. Science connects friction and wear of materials with lubrication through the term tribology. Furthermore, several agreements propose the term tribology to replace the term lubrication in the scientific fields, namely teaching and research.
Our understanding of mechanical friction has come a long way. Although Aristotle around 500 BC introduced the existence of frictional forces, the first person to study mechanical friction scientifically was Leonardo de Vinci in 1470. He measured the forces for moving horizontally rotating blocks and inclined surfaces, as well as simple pulleys.
Gambar-3c-2-300×90.jpg Mechanical friction experiments initiated by Leonardo de Vinci.
Leonardo discovered that lubricants, smooth materials, and very small balls can all reduce mechanical friction forces. He said that the mechanical friction force corresponds to the load moving on the surface and does not depend on the area of the contact surface. For smooth, smooth surfaces, he found the mechanical friction resistance to be a quarter of the weight of the load. Currently, this result is a friction coefficient of 0.25, namely for a wooden or iron block moving on a wooden surface. Leonardo appears to be able to correctly distinguish between the load on a surface and the weight on an object, which is usually a block. If we look at the following picture, it supports the surface at an angle to the horizontal plane, and the normal force NF of the load is the weight W multiplied by . This is a surface load and not heavy in the true sense of a load.
A block on an inclined plane is an example of mechanical friction.
After Leonardo de Vinci, Guillaume Amontons was the next to study friction seriously. The experimental equipment is as shown in the following figure. In his experimental apparatus, he used springs to apply forces, and he studied the displacement of iron, wood, steel, and other objects when lubricated with lard. As a result, he stated that the force to move all bodies is equal to, say, one third of the applied load.
Amontons experimental apparatus for mechanical friction.
Amontons’ work was then continued by several other scientists such as de la Hire, Desaguliers, and also Coulomb, as well as several other scientists. Of the many scientists who tried to develop the research carried out by Amontons, Newton and Hooke played an important role. Newton studied fluid flow and simply defined viscosity by stating that the resistance to fluid flow corresponds to the speed at which the fluid is moving. Meanwhile, Hook is famous for studying elasticity and friction in rolling objects. He believed there was a contribution from adhesion to the friction force.
In 1750, Euler wrote a paper on friction and was perhaps the first to specifically distinguish between static and dynamic friction. If we look again at the case of an inclined plane, the greater the angle at which the block can slide itself provides a measure of the coefficient of static friction. The normal force and force F that make the block slide are . The coefficient of friction is F divided by NF, or . However, if it is changed, the block will accelerate. This indicates that friction is smaller when the block is in motion than when it is still (static). The concept of static and dynamic friction is very useful.
Dry Friction
The second type of friction is dry friction. To understand this type of friction let’s study it together. Let’s first consider two planar objects with no special lubrication between them, as shown in the following figure. Even without special lubrication, surface film, including contamination, and siding, may be present there.
Dry friction type, without special lubrication.
No surface is completely smooth. If you look at it with a very sophisticated tool, for example an electron microscope , you can get a pattern (section) of unevenness on an object’s surface. To the naked eye you may find a very smooth surface, but in reality this is not the case. Therefore, for larger scales, the surfaces will be in closer contact with each other.
If two surfaces are moved relative to each other, parts of the uneven pattern will collide. From this situation, we can imagine the following four possibilities:
· Two surfaces can separate and move away from each other, as proposed by Amontons and Coulomb.
· Two surfaces can be deformed, either momentarily or permanently, during sliding against a deforming force.
· Parts that show unevenness on one surface may separate from another.
· Parts that show unevenness on a surface can be pulled or pushed from one surface to another, and vice versa.
We can see that in the last two cases, material is removed from the surface. This then becomes what is often called material wear. Moreover, wear will occur on the two surfaces that rub against each other.
-3f-1-300×136.jpg Example of dry friction type ©jimbartonautomotive
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In a car, the easiest example of a problem to observe is a brake system problem, as shown in the following picture. Whether disc or drum brakes, both are examples of dry friction types. We find that, for example, the wear that occurs on brake brakes is not only the canvas but also wear on the disc disc . Of course, discs experience wear and tear longer than canvas. This is because the disc material is stronger than canvas.[]