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Questions tagged [friction]

160 questions
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Additional jacking force to overcome stiction/dry friction

It is common to lift bridges to replace bearings, etc. In an ideal world the lifting capacity required of the jacks would be the self-weight of the bridge divided by the number of jacks (+ allowances for wind/snow, etc.). From my (limited)…
thomasmichaelwallace
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What type of ultrasonic transducer would be suitable for ultrasonic welding?

Project background: I am working on a project where i need to weld plastic using ultrasonic transducers. Problem: Since I'm still learning engineering, I have a hard time figuring out what all the factors are in order to choose the right…
vaid
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What causes friction in magnetic bearings?

Magnetic bearings work by levitating a rotating shaft so that it is not in contact with its supports. This greatly reduces the friction of the system. In all of the literature that I have seen on magnetic bearings, the bearings are described as "low…
hazzey
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Not a good idea to rub two of the same material against each other?

I've read that it's not a good idea to rub two surfaces of the same material against each other, e.g., plastic against plastic, metal against metal. Plastic against metal is preferred. Why is this the case? Is it because that the coefficient of…
John M.
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How do you attach something temporary to a smooth metal shaft?

I want to attach something small to the smooth metal shaft of a small motor (2-3 mm in diameter), like fan blades, but I want it to be temporary. If I make it too loose, then the fan won't turn at all, but if I glue or solder it on, then it will be…
Pyraminx
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Wheelbarrow minimize wear

I have a question about the design principle. To explain my problem I made the sketch "wheelbarrow". To minimize wear, which design is preferred?
laurens van Lieshout
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Deriving the amplitude of a coulomb (dry friction) damped spring

This is my first time posting anything, but I could not figure out the derivation of the amplitude of the spring for the 4 first oscillations. I am not acquainted with the effect and calculations of damping since I am only in high school. This is…
Sam
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Adding a lubricant to an already lubricious material, how is CoF affected?

I have a dry film moly-graphite lubricant (CoF=.075) and a lubricious CVD coating (CoF=.05). The CoF of each of these lubricious materials was determined using the same ASME standardized test. The standardized test consists of: a plain steel object…
CBRF23
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Why is the friction factor in laminar flow independent of pipe roughness?

The Darcy friction factor is defined as: $$f_D =\frac{64}{Re}$$ with $Re$ I mean Reynolds number (global). I was wondering why Darcy in laminaire flow is independent of pipe roughness (wall roughness)? That is not the case in turbulent and transient…
user14407
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5 answers

How can I improve traction on a wheeled vehicle yet reduce friction?

This is inspired by a project I undertook for my Physics class last year; I'd like to apply it in the future. Background: For the project, I and a few classmates were required to build a small car powered by any of a number of sources; we opted for…
HDE 226868
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Are jeweled bearings commonly used for applications other than mechanical timepieces?

Jeweled bearings use a metal spindle with a jewel lined pivot hole (pictured below). They have been important in the manufacture of mechanical timepieces since the early 1700's. Their importance lies in the fact that they can be machined to very…
Chris Mueller
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Quantifying and measuring friction under extreme conditions

I want to quantify friction between a bullet and barrel to test different friction-proofing coatings and treatments. Is there a controlled test I could do at low speeds in a lab between samples of treated copper and steel that would be theoretically…
feetwet
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Why use bushings of different material than what they contact?

I've heard that materials that need to slide against each other should be of different materials. Why is that?
uncaged
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Suggestions for low friction surface materials for a "beltless static treadmill"

I'm currently developing a treadmill for clinic gait research. If I were to build a flat treadmill with no moving surfaces what materials or coatings would be worth exploring as walking surface. Ideally, the surface would be durable, safe to touch…
piman
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Equivalent viscous damper for friction damping

I have a friction damping system which is exited by a harmonic force FE (depicted on the left side). Is there a way to convert the friction damper to a linear or nonlinear damper, such that the damping at a given excitement frequency is equal? I am…
M. Martin
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