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Strain or Tension?

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Forum topic by Surfside posted 707 days ago 654 views 0 times favorited 11 replies Add to Favorites Watch
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Surfside

3040 posts in 771 days


707 days ago

I know most woodworkers use the term tension rather than strain. In sawmillcreek.org, a thread has been trending with comments regarding which is right, strain or tension? As a non-expert to the field, I would like to ask LJ’s regarding this subject and your knowledge. What do you think? Is tension and strain the same?

-- "someone has to be wounded for others to be saved, someone has to sacrifice for others to feel happiness, someone has to die so others could live"


11 replies so far

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bondogaposis

2439 posts in 949 days


#1 posted 707 days ago

I use tension to distinguish it from compression.

-- Bondo Gaposis

View Nicky's profile

Nicky

636 posts in 2690 days


#2 posted 707 days ago

Non expert opinion…

I don’t think of tension and strain being the same in the context of wood.

Strain causes a board to warp or deform in someway (e.g. as it looses moister)

Tension is released when I cut a strained board, and this deforms my cutoff in someway.

But what do I know. My 2cents.

-- Nicky

View RickRogers7's profile

RickRogers7

39 posts in 1636 days


#3 posted 707 days ago

Tension or compression describe the load being applied to a particular item. Strain is a measure of how much that item deflects due to an applied load.

View JJohnston's profile

JJohnston

1577 posts in 1889 days


#4 posted 707 days ago

Strain is technically the amount of UNIT deformation (so much deformation per unit of length – think of it as “inch per inch”). The total amount of elongation or shortening is strain x the length of the member.

Tension is a force; its units are units of force, like pounds. It causes a tensile stress which is a function of the cross-sectional area of the member (stress = force divided by area, for lb/sq. in.)

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

View Dusty56's profile

Dusty56

11638 posts in 2286 days


#5 posted 707 days ago

World English Dictionary
tension (ˈtɛnʃən)

— n
1. the act of stretching or the state or degree of being stretched
2. mental or emotional strain; stress
3. a situation or condition of hostility, suspense, or uneasiness
4. physics a force that tends to produce an elongation of a body or structure
5. physics a. voltage, electromotive force, or potential difference b. ( in combination ): high-tension ; low-tension
6. a device for regulating the tension in a part, string, thread, etc, as in a sewing machine
7. knitting the degree of tightness or looseness with which a person knits

[C16: from Latin tensiō, from tendere to strain]

strain/strān/
Verb:
Force (a part of one’s body or oneself) to make a strenuous or unusually great effort.
Noun:
A force tending to pull or stretch something to an extreme or damaging degree.
A breed, stock, or variety of an animal or plant developed by breeding.
Synonyms:
verb. stretch – filter – tighten – tense
noun. stress – tension – race

-- I'm absolutely positive that I couldn't be more uncertain!

View DylanC's profile

DylanC

114 posts in 1272 days


#6 posted 707 days ago

RickRogers has it…Strain is a measurement of how much something is stretched. That’s the engineering definition, by the way. Common woodworing context may be different. The behavior Nicky is describing (a board warping after it is cut) is something that metals to also and is cased by residual internal stress.

-- Dylan C ...Seems like all ever I make is sawdust...

View JJohnston's profile

JJohnston

1577 posts in 1889 days


#7 posted 707 days ago

No, what he defined is deformation, and deformation and strain are not the same thing.

http://www.mechatools.com/en/definition.html

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

View Surfside's profile

Surfside

3040 posts in 771 days


#8 posted 706 days ago

So, when does strain apply when we deal with band saw blades?

-- "someone has to be wounded for others to be saved, someone has to sacrifice for others to feel happiness, someone has to die so others could live"

View JJohnston's profile

JJohnston

1577 posts in 1889 days


#9 posted 706 days ago

I’m not sure what you mean. The blade manufacturer has (probably) an allowable tensile stress on the blade material. That and the cross sectional area determine the allowable tension. The strain is what it is; in this application, it doesn’t seem to me to be important to know it.

I can tell you, for example, where it would be important to. I’m a bridge engineer, and sometimes, we want to know the actual stress on a member in service, so we put strain gauges on it. We measure the strain, and using these relationships between force, area, stress and strain, we can calculate the actual stress on it.

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

View Surfside's profile

Surfside

3040 posts in 771 days


#10 posted 703 days ago

As you’ve mentioned that strain is the amount of unit of deformation or elongation, wouldn’t elongation or deformation happen in a band saw blade? I think this is what I was supposed to ask.

-- "someone has to be wounded for others to be saved, someone has to sacrifice for others to feel happiness, someone has to die so others could live"

View JJohnston's profile

JJohnston

1577 posts in 1889 days


#11 posted 690 days ago

Yes, yes it would.

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

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