metallurgy question

Michael Press wrote:
In article
,
" wrote:

On Jun 6, 12:28 pm, zencycle wrote:
Aluminum has the characteristic of being able to be bent to a position
to hold its form, pretty much one time, and only to a certain extent
in that shape. When you bend it back, stress cracks occur, and even
breakage.

I'm only thinking of the context of cold-working, not forging or hot
working.

I seem to remember the reason for the crack and breakage upon
attempting a second manipulation was that the initial bend in cold
working sets up a crystalline structure, and subsequent working
essentially breaks the structure. Do I have that right?

I'm looking for the applicable terms:

Please correct me if I'm wrong. Is it the modulus of elasticity that
is the overall characteristic that I'm referring to?

What is the term used for the initial bend (if there is one)? and what
is the name of the stress factor that occurs after the second attempt
at working the part?
The modulus of elasticity is how much the material
bends or elongates per applied force.

Not quite.
It is elongation per applied force per area of applied force.
Modulus of elasticity is stress/strain.

the slope of the line, yes.


Strain is force applied per area.
Stress is amount of deformation.

no.

stress is force per area.
strain is elongation per length.




Elastic modulus is a 2-tensor of dimension 3.
9 components.
The diagonal components give deformation normal to
a coordinate plane given force applied normal to
the coordinate planes.
The six off diagonal components give shear deformation
for force applied parallel to coordinate planes.
The 9 components could all be different from each other.


that's mental masturbation if you can't define stress and strain correctly.

On 2008-06-08, Michael Press wrote:
[...]
Elastic modulus is a 2-tensor of dimension 3.
9 components.
The diagonal components give deformation normal to
a coordinate plane given force applied normal to
the coordinate planes.
The six off diagonal components give shear deformation
for force applied parallel to coordinate planes.
The 9 components could all be different from each other.

So for a lump of steel, am I right in thinking the tensor looks like
this:

E 0 0
0 E 0
0 0 E

where E is about 200GPa.

But for CF or something anisotropic, I would have different values all
over the place.

There don't seem to be any "shear components" in my matrix for steel,
but I don't really understand that: coordinate planes are usually
orthogonal, which means force normal to one plane is parallel to the
other two. So I don't see how you can divide forces into two sets of
those normal to coordinate planes and those parallel to them.

On 2008-06-09, jim beam wrote:
[...]
/any/ material that plastically deforms is ductile to some degree.
the question is, "how much". to be clear, the o.p. is describing low
ductility, not brittleness.

What's the difference between low ductility and brittleness?

"Ben C" wrote in message
...
On 2008-06-09, jim beam wrote:
[...]
/any/ material that plastically deforms is ductile to some degree.
the question is, "how much". to be clear, the o.p. is describing low
ductility, not brittleness.

What's the difference between low ductility and brittleness?

It means that beam can beam.

Ben C wrote:
On 2008-06-09, jim beam wrote:
[...]
/any/ material that plastically deforms is ductile to some degree.
the question is, "how much". to be clear, the o.p. is describing low
ductility, not brittleness.

What's the difference between low ductility and brittleness?

energy absorption on fracture for one. it's all about the propagation
mechanism. but you're on the right track that the two are related.

Ben C wrote:
On 2008-06-08, Michael Press wrote:
[...]
Elastic modulus is a 2-tensor of dimension 3.
9 components.
The diagonal components give deformation normal to
a coordinate plane given force applied normal to
the coordinate planes.
The six off diagonal components give shear deformation
for force applied parallel to coordinate planes.
The 9 components could all be different from each other.

So for a lump of steel, am I right in thinking the tensor looks like
this:

E 0 0
0 E 0
0 0 E

where E is about 200GPa.

But for CF or something anisotropic, I would have different values all
over the place.

There don't seem to be any "shear components" in my matrix for steel,
but I don't really understand that: coordinate planes are usually
orthogonal, which means force normal to one plane is parallel to the
other two. So I don't see how you can divide forces into two sets of
those normal to coordinate planes and those parallel to them.

michael press is blowing smoke. [surprise.] yes, you need to know
about triaxial stress, mohr's circle, poisson ratio, etc., if doing
in-depth analysis, but for simple questions about ductility, it's just
bull. particularly when from someone that can't define stress or strain
properly.

In article ,
Ben C wrote:

On 2008-06-08, Michael Press wrote:
[...]
Elastic modulus is a 2-tensor of dimension 3.
9 components.
The diagonal components give deformation normal to
a coordinate plane given force applied normal to
the coordinate planes.
The six off diagonal components give shear deformation
for force applied parallel to coordinate planes.
The 9 components could all be different from each other.

So for a lump of steel, am I right in thinking the tensor looks like
this:

E 0 0
0 E 0
0 0 E

where E is about 200GPa.

But for CF or something anisotropic, I would have different values all
over the place.

There don't seem to be any "shear components" in my matrix for steel,
but I don't really understand that: coordinate planes are usually
orthogonal, which means force normal to one plane is parallel to the
other two. So I don't see how you can divide forces into two sets of
those normal to coordinate planes and those parallel to them.

Epoxy resin and carbon fiber lay ups have anisotropic elastic properties,
as do various crystals.

http://books.google.com/books?id=90_ORVHeNkIC&pg=PT237&lpg=PT237&dq=anisot ropic+crystal+%22elastic+modulus%22&source=web&ots =Zg1nRkq41y&sig=39g5dHxh5jGudvEd3_N-aug5sFc&hl=en

--
Michael Press

Michael Press wrote:
In article ,
Ben C wrote:

On 2008-06-08, Michael Press wrote:
[...]
Elastic modulus is a 2-tensor of dimension 3.
9 components.
The diagonal components give deformation normal to
a coordinate plane given force applied normal to
the coordinate planes.
The six off diagonal components give shear deformation
for force applied parallel to coordinate planes.
The 9 components could all be different from each other.
So for a lump of steel, am I right in thinking the tensor looks like
this:

E 0 0
0 E 0
0 0 E

where E is about 200GPa.

But for CF or something anisotropic, I would have different values all
over the place.

There don't seem to be any "shear components" in my matrix for steel,
but I don't really understand that: coordinate planes are usually
orthogonal, which means force normal to one plane is parallel to the
other two. So I don't see how you can divide forces into two sets of
those normal to coordinate planes and those parallel to them.

Epoxy resin and carbon fiber lay ups have anisotropic elastic properties,
as do various crystals.

http://books.google.com/books?id=90_ORVHeNkIC&pg=PT237&lpg=PT237&dq=anisot ropic+crystal+%22elastic+modulus%22&source=web&ots =Zg1nRkq41y&sig=39g5dHxh5jGudvEd3_N-aug5sFc&hl=en


so? that doesn't address his question in the slightest. perhaps you
shouldn't try to bull**** outside your area of expertise?

ah, but i remember now, you're the guy that thinks anodizing crack
orientation has no bearing on fatigue initiation! now your confusion
becomes clear!