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Science Forum Index » Mechanics Forum » In shear or...?...
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 Posted: Fri May 16, 2008 9:44 am |
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Guest
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So I'm not an engineer or a student, but I fabricate some things for
various jobs I need done. Recently I pondered two things and was
wondering about them, if anyone could enlighten me that'd be wonderful
as I can reason out both a yes and no to 'A' as well as either end
result for 'B', but I don't know which is correct.
A) If there's two plates standing on end with force pulling them down,
a third fit in between them being pulled up, and a shaft running
through concentric holes in all 3 plates, the shaft is in shear. Now
lets spread those two plates being pulled down further apart so
there's a good amount of space between them, to throw some numbers at
it, .5" plates with the outer two being 8" apart from inside face to
inside face and the third centered between them. Is this still shear
even though the shaft will bend when it yields rather than flat out
shearing if the force is great enough?
B) I have a pipe that fits inside another pipe, I slide the one
halfway in the other and drill a hole through both putting a pin in
there to hold them together. I apply compression to the ends of the
tubes putting the pin in shear. Is this considered double shear or is
each side of the pipe treated individually? |
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| dlzc... |
| Posted: Fri May 16, 2008 10:36 am |
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Guest
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Dear joshya...:
On May 16, 12:44 pm, joshya... at (no spam) gmail.com wrote:
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Quote: A) If there's two plates standing on end with force
pulling them down, a third fit in between them
being pulled up, and a shaft running through
concentric holes in all 3 plates, the shaft is in
shear. Now lets spread those two plates being
pulled down further apart so there's a good
amount of space between them, to throw some
numbers at it, .5" plates with the outer two
being 8" apart from inside face to inside face
and the third centered between them. Is this
still shear even though the shaft will bend when
it yields rather than flat out shearing if the force
is great enough?
Yes. If the line of action of each force is not "coaxial" with all
the others, a bending moment is produced, and the material under
stress is forced to provide / transmit this bending moment, which
produces non-zero shear in the member.
Quote: B) I have a pipe that fits inside another pipe,
I slide the one halfway in the other and drill a
hole through both putting a pin in there to hold
them together. I apply compression to the
ends of the tubes putting the pin in shear. Is
this considered double shear or is each side
of the pipe treated individually?
I wouldn't spend a great deal of time worrying about names. *If* the
pin is inserted normal to the line of action of the forces, and the
holes are all the same diameter, you can treat the pipe example as you
do the "tongue and groove" example in A).
David A. Smith |
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| Posted: Tue May 20, 2008 8:29 am |
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Guest
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On May 16, 3:36 pm, dlzc <dl... at (no spam) cox.net> wrote:
Quote: Dear joshya...:
On May 16, 12:44 pm, joshya... at (no spam) gmail.com wrote:
...
A) If there's two plates standing on end with force
pulling them down, a third fit in between them
being pulled up, and a shaft running through
concentric holes in all 3 plates, the shaft is in
shear. Now lets spread those two plates being
pulled down further apart so there's a good
amount of space between them, to throw some
numbers at it, .5" plates with the outer two
being 8" apart from inside face to inside face
and the third centered between them. Is this
still shear even though the shaft will bend when
it yields rather than flat out shearing if the force
is great enough?
Yes. If the line of action of each force is not "coaxial" with all
the others, a bending moment is produced, and the material under
stress is forced to provide / transmit this bending moment, which
produces non-zero shear in the member.
B) I have a pipe that fits inside another pipe,
I slide the one halfway in the other and drill a
hole through both putting a pin in there to hold
them together. I apply compression to the
ends of the tubes putting the pin in shear. Is
this considered double shear or is each side
of the pipe treated individually?
I wouldn't spend a great deal of time worrying about names. *If* the
pin is inserted normal to the line of action of the forces, and the
holes are all the same diameter, you can treat the pipe example as you
do the "tongue and groove" example in A).
David A. Smith
Thanks a bunch  |
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