Measuring Friction at a curved surface

In summary, the conversation discusses ways to measure the friction between a metal block and a metal roller with a matching radius. The coefficient of friction, Cfrict, can be measured by rotating the cylinder and correcting the torque required, Ftorque, for the radius and ratio with the applied force, Fapp. It is suggested to use a motor attached directly to the cylinder shaft and measure the torque of the motor against its mounting, which would be a cost-effective solution using force transducers.
  • #1
bartrocs
27
0
Hi, if I have a block of metal with a quarter circle curve cut out of it, and a metal roller of matching radius that contacts this curved piece, what are some ways I could go about measuring the friction between these two surfaces? The roller is fixed and the block is pushed into it with a horizontal force. See the image for clarification:
XbhVSR6.jpg
 

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  • #2
The friction coefficient will be highly dependent on lubrication and surface contamination.

To measure the coefficient, Cfrict, you need to rotate the cylinder. The torque required, Ftorque, needs to be corrected for the radius, Ftorque / r, then the ratio with your Fapp computed.
Cfrict = Ftorque / ( r * Fapp )
 
  • #3
of course, I understand the theory, I was probably not clear enough but I am interested in the actual system of measurement, for example, if I had some motor driving a shaft with the drum on it. If I put a reactive torque (torsional) sensor inline between the drum and the motor, would that work to measure the frictional torque?
 
  • #4
bartrocs said:
If I put a reactive torque (torsional) sensor inline between the drum and the motor, would that work to measure the frictional torque?
Yes.
But if instead you attached the motor directly to the cylinder shaft, you could then measure the torque of the motor against it's mountings. The torque gauge is then not rotating, so you need no slip rings for instrumentation cables to the gauge.
 
  • #5
Baluncore said:
But if instead you attached the motor directly to the cylinder shaft, you could then measure the torque of the motor against it's mountings. The torque gauge is then not rotating, so you need no slip rings for instrumentation cables to the gauge.

Perfect! I did not think of that. It would probably be a more cost effective solution as I could use force transducers on the mountings and measure torque that way. Thanks for your help
 
  • #6
bartrocs said:
I could use force transducers on the mountings and measure torque that way.
The motor could be mounted on a shaft co-axial with the roller shaft. Then only one force sensor is needed at the far end of a torque arm attached to the motor casing. So simple.
 

1. How is friction measured at a curved surface?

Friction at a curved surface can be measured using a device called a tribometer, which applies a known force to the surface and measures the resulting frictional force. This can also be done using an inclined plane, where the angle at which an object starts to slide can be used to calculate the coefficient of friction.

2. What factors affect friction at a curved surface?

The amount of friction at a curved surface is affected by several factors, including the nature of the materials in contact, the smoothness of the surface, and the force pressing the surfaces together. Additionally, the angle of the curved surface and the speed at which the surfaces are moving can also affect friction.

3. How does the coefficient of friction change on a curved surface?

The coefficient of friction, which is a measure of the amount of friction between two surfaces, can vary on a curved surface depending on the direction of the force being applied. This is because the curvature of the surface can affect the distribution of the force and therefore the amount of friction.

4. Can lubricants affect friction on a curved surface?

Yes, lubricants can have a significant impact on friction at a curved surface. By reducing the contact between the surfaces, lubricants can decrease the amount of friction and make the surface smoother to slide against. However, the type and amount of lubricant used can also affect the coefficient of friction.

5. How is friction at a curved surface important in real-world applications?

Understanding and measuring friction at a curved surface is crucial in many real-world applications, such as designing tires for vehicles, creating efficient machinery, and developing medical devices. Friction at a curved surface can also impact the performance and safety of sports equipment, such as ice skates and ski edges.

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