What Is a Friction Tester?
A friction tester is a device designed to measure various frictional forces.
Friction is a resistance force that occurs when two objects are in contact. There are two main types of friction forces: static and kinetic. Static friction acts on a stationary object, while kinetic friction affects an object in motion. The coefficient of static friction evaluates the resistance to movement or slippage of a stationary object. Conversely, the coefficient of kinetic friction, which represents the frictional force between moving objects, assesses how slippery or worn an object is during motion.
Uses of Friction Testers
Friction testers are instrumental in inspecting and evaluating the performance of various materials and products.
1. Evaluation of Materials
For example, the evaluation of rubber and plastic, commonly used as shock absorbers and safety devices, requires measuring their friction force to assess their durability and safety.
2. Evaluation in the Automotive Field
These testers are essential for evaluating the durability of painted surfaces on automobiles. They help ensure that these surfaces are sufficiently resilient to friction and resistant to scratching and peeling.
3. Evaluation in the Field of Construction Materials
Friction testers also play a significant role in assessing coatings on building materials. They measure the slipperiness of wooden floors and the scratch resistance of paints and other coatings.
4. Evaluation in the Medical Field
In the medical sector, these devices are used for measuring the friction of artificial joints and injection needles.
Principle of Friction Tester
Friction testers measure either the “coefficient of static friction” or the “coefficient of kinetic friction,” corresponding to the two types of frictional forces: static and dynamic.
1. Static Friction Coefficient Measurement Type
This type determines the coefficient of static friction, often used for materials like paper and plastic film. The inclined method involves placing weights on the sample and tilting it until the weight begins to slide. The angle at this point is used to calculate the coefficient. The horizontal method, where a weight is placed on the sample and pulled, measures the resistance at the point of movement.
2. Coefficient of Dynamic Friction Measurement Type
Specialized testers for kinetic friction slide a specified material on the sample. They come in rotational and reciprocating types. Measurements are made using various methods, including direct force measurement with a strain gauge or load cell, or calculating based on the load power of the drive motor.
Types of Friction Testers
The main types for measuring dynamic friction are rotating and reciprocating testers, available in point, line, and surface contact forms.
1. Point Contact Type
Examples include ball-on-plate and ball-on-disk methods, where a spherical material interacts with a disk or plate sample. These methods are straightforward due to the point of contact but can be inaccurate if the balls or pins wear down.
2. Linear Contact Type
The block-on-ring and pin-block methods involve a block or pin-shaped sample interacting with a cylindrical material. These are predominantly used for rotating types and are particularly useful for measuring lubricating materials.
3. Surface Contact Type
These include block-on-plate, pin-on-disk, and thrust cylinder types. The pin or cylinder in these methods interacts with a flat sample surface. The block-on-plate method is a reciprocating type, while the pin-on-disk and thrust cylinder methods are rotating types. The advantage of surface contact types is their larger contact area, providing increased durability.