Look at strength of materials from an historical perspective

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29 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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Look at strength of materials from
an historical perspective

Since the Stone Age, Human advancement has been inextricably tied to

metal alloy
STRENGTH

compression tension


shear

the
strength

of a material is its ability to withstand an applied
stress

without

failure. Yield strength refers to the point on a stress
-
strain curve beyond which

the material begins deformation that cannot be reversed upon

removal of the loading. Ultimate strength refers to the point corresponding to the

maximum stress. The applied stress may be
tensile
,
compressive
, or
shear
.

What sets properties (strength)?

Synthesize what you learned in HS (chemistry+physics+life)

Bonding

+


Crystal Structure

+


Defects

Properties

ionic


metallic

dislocation

strain

stress

rock

Relative

Strength

Stone Age

STONE AGE

2,500,000 BCE
-

4,200 BCE

5

Fe

Ferrum

Cu

Cuprum

Ag

Argentum

Sn

Stannum

Au

Aurum

Hg

Hydrargyrum

Pb

Plumbum

SEVEN METALS of ANTIQUITY

chalcolithic

iron

bronze

hammering

at room temp

did 2 things:

1)
shaped

2)
stronger

6

Metal Forming of Silver

Strength

Stress/Strain

To get strain

Need to apply more force

So, stronger

referred to as

WORK HARDENING

6000 year old copper needle

modern copper needle

Flat grains so hammered into a needle

Iran 4200BC (on left)

copper

strain

stress

rock

Relative

Strength

Chalcolithic Age

Stone Age

CHALCOLITHIC AGE

4,200 BCE
-

3,000 BCE

10

Bronze Age


Alloying

-

Purposeful mixing of different metals or
ores to achieve a product with even better
properties (e.g. hardness or wear
-
resistance)


Adding
Tin

to Copper yields
Bronze


Origin unknown since tin ores are not widely present in
eastern Mediterranean.


A number of other chemicals are typically present
(e.g. arsenic, bismuth, and antimony)


Type and quantity of impurity can tell archeologists the
origin of a bronze

11

Bronze Production in Egypt

2000 BC

12

Bronze Production in Egypt

Figures after Hummel

Cu
-
Sn

bronze

copper

strain

stress

rock

Relative

Strength

Bronze Age

Stone Age

Chalcolithic Age

BRONZE AGE

3,000 BCE
-

1,200 BCE

iron

bronze

copper

strain

stress

rock

Relative

Strength

Iron Age

?????

weaker than
Bronze
!

Bronze Age

IRON AGE

1,200 BCE


21st CENTURY

IRON making

--
wrought iron
--

Still not liquid iron

This is slag

here is a

Bloom


almost

pure iron

but the back
-
and

forth


“steeling”

or adding carbon

Fe
-
C is steel

wrought iron

Noun

a pure form of iron

with a low carbon

content, often

used for decorative

work

wrought is middle

English as past

tense for ‘work’

iron

bronze

copper

mild steel

strain

stress

rock

Relative

Strength

Ahh
-

Iron (steel) Age

Bronze Age

Iron Age

Chalcolithic Age

Stone Age

IRON AGE

1,200 BCE


20TH CENTURY

only steel is
so versatile

--
the democratic metal
--

From: Mathurin Jousse, 1627

copperas==iron sulfate

verdigris==green patina on bronze

alum==hydrated aluminum potassium sulfate

You do not want your sword to be
just
tough

and do this:

Nor should they be just hard

Uma has the strong steel sword

Wire die

iron

bronze

mild steel

strain

stress

piano wire

Very High Strength

Great Creep Resistance

Acoustic (Sounds good)

MPa

4000

2000

1000

500

High Strength Steel

iron

bronze

copper

mild steel

strain

stress

rock

Iron (steel) Age

Bronze Age

Iron Age

Chalcolithic Age

Stone Age

steel advancement through 20
th


century

steels

MSE201

Materials Selection

1903 Wright Brothers

The genesis for this topic is the National Research Council NRC report from 2003


which concluded that :

"monolithic structural materials composed of metal alloys are

not likely to enjoy major improvements in any of several

mechanical properties."


In this circumstance the document refers to discovering and

producing new metal alloys in quantities that are sufficient

for manufacturing structural materials, which would include

things like plates, beams, or sheets.


So, after ca. 6,000 years (according to the NRC) metals are

finished for advancement of human civilization advancement

Materials Research to Meet the 21st Century Defense Needs


(National Research Council, National Academies Press, Washington, DC, 2003)

Simulated

liquid

structure

of

amorphous

steel

(Fe
48
Cr
15
Mo
14
Y
2
C
15
B
6
)

obtained

from

first
-
principles

molecular

dynamics

(M
.

Widom)
.


Fe




Cr




Mo




Y




C


††

B



Copper

Bronze

Gold

Silver

Electrum

Lead


one more trick for metals?

strain

amorphous steel

iron

bronze

copper

stress

rock

Relative

Strength

steels

to

modern

times

about 2
-
3 times the yield strength of

high strength steels and 2 times the

elastic strain

AND has damage tolerance

29

Fracture strengths of

glassy metals approaching
ideal strengths


Deformation are localized

There is no work hardening


1

2

3

4

Elastic Strain (%)


Stress (GPa)

1

2

3

Steel

Ti

5

Ceramic

0

UVa Amorphous

steel

Polymer

EVSC 201

Lisa E. Friedersdorf, PhD

Future: How big is a nanometer?

Lisa E. Friedersdorf, PhD

Carbonaceous nanomaterials are exciting
because of their amazing material properties.


Nanotubes, for example:


Mechanical


100 times stronger than steel


Electrical


Conduct electricity better than copper


Depending on “flavor” metal or semiconductor


Thermal



Conduct heat better than diamonds

Optical/ Surface/ Geometry, etc.



properties also being exploited


Conclusions

Human technological advancement can be tracted with advance of materials
strength



Stone Age

Chalcolithic Age

Iron (steel) Age

Nano Age (?)