IE 560 Assignment 2 – Comparison of Material Performance and Cost Comparison of Specic Strength
Summary of Specic Strength values S.No
Material
Specic Strength (kN*m/Kg) Loer Limit
!pper Limit
"
#lain $ar%on an& Lo 'lloy Steels
.
+,.,
St Stainless Steel
.-
",+."
- $ast rons
-,.
0".
1 'l 'luminum 'lloys
".
"-.
,.
"-".-
Magnesium 'lloys
.1
".
,
-,.
0+.,
0 $opper 'lloys 2i 2itanium 'lloys
$oncrete" 3lass" "+ Silic licon $a $ar%i& r%i&e e" ""
#olymers
" $omp $ompos osit ite e Mate Materi rial als s" "- 4oo&"
0. .
".-
"0.+
"-.-
,+.+
".0
.
",.+
".+
". !ltimate 2ensile Strength use& for calculating Specic Strength for materials hose 5iel& Strength is not
Comparison of Specic Modulus
Summary of Specic Mo&ulus values S.No
Material $lass
Specic Mo&ulus (3pa*cm -/Kg) Loer Limit
!pper Limit
.
.
#lain $ar%on an& Lo 'lloy Steels Stainless Steel
1."
.0
-
$ast rons
"-.+
1.+
1
'luminum 'lloys
0.
.,
0
$opper 'lloys
"".
".1
Magnesium 'lloys
1.1
0.+
,
2itanium 'lloys
.
0.
$oncrete
".0
".
3lass
,.
-".
"+
Silicon $ar%i&e
+.
.1
""
#olymers
+.+
.,
"
$omposite Materials
1."
"++.+
"-
4oo&
".+
1.+
"
Comparison of Cost!oad "earing Capacit# $henceforth called as C!" ratio%
Summary of $ost/Loa& 6earing $apacity values
S.No " 1 0 , "+ "" " "-
Material $lass #lain $ar%on an& Lo 'lloy Steels Stainless Steel $ast rons 'luminum 'lloys $opper 'lloys Magnesium 'lloys 2itanium 'lloys $oncrete 3lass Silicon $ar%i&e #olymers $omposite Materials 4oo&
$ost/5iel& Strength ("+ - !S7/Kg*M#a) Loer Limit !pper Limit .
0."
. ".-0 ". . -+.1 "+.1+.+1 ., ,0.0 . +.,0 0.00
+ ".0 "., "1."1 0+ ,.1, ".+ ""."0 1,"., "+. -"0., .--
Plain car&on and lo' allo# steels ith a cost to loa& %earing capacity of . to 0." (secon& %est amongst metal alloys) an& very goo& mechanical strength make it the most i&ely use& of all alloys. 2hey are only prece&e& %y cast iron in terms of cost to loa& %earing capacity (".-0 to ".0). 8oever9 the poor tensile strength an& mallea%ility of cast iron fairly limits its usage. 'lloy steels starting ith a specic strength range from . to +,., n& a i&e variety of applications &ue to this e:ceptional range from heavy loa& applications to in&ustries here eight is an important consi&eration (use of high strength steels). 2heir very goo& &uctility an& mallea%ility also translates into loer machining an& manufacturing costs.
Cast Irons as alrea&y &iscusse& su;er from poor tensile strength. 8oever9 they have very goo& compressive strength an& vi%ration &ening properties. 2herefore9 they n& limite& usage.
Stainless steels ($L6 ratio range< . to +) are not as i&esprea& as car%on alloy steels &ue to cost9 %ut9 ith a specic strength range similar to car%on steels9 su%stitute car%on an& lo alloy steels in applications re=uiring high resistance to corrosion.
Aluminum allo#s ($L6 ratio range from ". to ".,) are the ne:t most i&ely use& after ferrous alloys. 2heir very goo& specic strength makes them one of the most preferre& materials in applications here eight is an important consi&eration.
Magnesium allo#s ($L6 ratio range< -+.1 to 0+) ith its very lo &ensity has a very goo& specic strength. 8oever9 their relatively high costs an& lo melting temperatures limits its usage to applications re=uiring light eight construction.
Copper Allo#s ($L6 ratio range< . to "1."1) n& limite& usage in loa& %earing applications &ue to their or&inary specic strength (%arring 6eryllium $opper)9 an& are mostly use& for their e:ceptional thermal an& electrical con&uctivity. 6eryllium $opper
though has very goo& strength is e:or%itantly price& ("1."1 $6 ratio) an& is therefore limite& to niche areas (oing to its other properties like non>sparking9 corrosion resistance an& maintaining structural integrity un&er high temperatures).
(itanium allo#s ith their e:ceptional specic strength (%etter even then steels) an& corrosion resistance make for very goo& materials for loa& %earing applications. 8oever9 their very high $L6 ratio (varying from "+.1- to ,.1,) severely limits their
. 2he un&erline& te:t also ansers the =uestion regar&ing reason for i&esprea& usage of #lain car%on an& alloy
usage to applications here eight is a consi&eration an& harsh environmental con&itions e:ist (aircraft in&ustry9 surgical implants9 petroleum an& chemical in&ustries).
Concrete has poor specic strength. 8oever9 ith a very lo $L6 ratio of ".+
an&
very goo& compressive strength (an& tensile strength as reinforce& concrete) n&s application in construction in&ustry (large volumes of concrete an& using steel ro&s o;sets the &isa&vantage of having lo specic strength).
)lasses ith a $L6 ratio ranging from ., to ""."0 have a i&e range of specic strength from %eing as lo as . for so&a lime glass to "0.1 for chemically tempere& glass. 8oever9 %rittleness of the material means it is not suita%le for loa& %earing applications.
Silicon Car&ide has very goo& specic strength. 8oever9 a very high $L6 ratio an& e:treme %rittleness means that is not use& for loa& %earing applications. nstea&9 it is mostly employe& for its a%rasive properties an& in semicon&uctor electronics.
Pol#mers have lo specic strength hen compare& to most of the steel alloys. 'lso9 their $L6 ratio is much higher compare& to ferrous alloys (. to "+.) an& is therefore not i&ely use& in loa& %earing applications.
Composite Materials e:hi%it the highest specic strength amongst all materials (for $ar%on9 #'N precursor > Stan&ar& Mo&ulus). 8oever9 they are also the most
e:or%itantly an& therefore9 are use& in applications here %enets from eight re&uction outeighs input cost or hen cost consi&eration is secon&ary (aircraft in&ustry9 high performance cars9 etc.)
*ood ith a $L6 ratio ranging from 0.0 to .- has a very goo& specic strength. 8oever9 since oo& has poor resistance to %en&ing (loa& perpen&icular to grain orientation)9 its usage in loa& %earing applications is limite& to construction in&ustry. $omparing the specic strength of materials9 composites clearly outperform all other materials ? there%y9 they oul& present the highest possi%ility of eight re&uction in aircraft in&ustry. 2hey also have the highest sti;ness hich is very important for parts that ant high resistance to @e:ing. 8oever9 the e:or%itant cost fairly limits is usage. 'lso9 these materials &o not sho any signs of failure %efore giving in. n aircraft in&ustry9 visual inspection of key components is a vital aspect of preventive maintenance. 4hile metal alloys may sho cracks %efore failing there%y giving the Maintenance personnel a chance to catch the &efect %efore failure9 composites oul& re=uire more regular usage of sophisticate& inspection techni=ues like ultrasonic or acoustic testing. 2itanium alloys have the %est specic strength amongst &iscusse& metal alloys an& therefore9 o;er the %est possi%ility of eight re&uction hen comparing metal alloys. 8aving higher temperature an& corrosion resistance compare& to 'luminum an& steels is also an a&&e& a&vantage. 2his also means that engine components an& skin panels may also %e manufacture& ith titanium alloys. 'luminum alloys though not as goo& as titanium alloys are relatively cheap an& therefore the most use& alloy. 8igh strength steel alloys an& stainless steels even though have e:ceptional specic strength are fairly limite& in their usage &ue to high &ensity. f e try to achieve eight re&uction through gauge re&uction9 @e:ing %ecomes an issue. 2herefore9 their usage is restricte& to areas here strength an& har&ness is e:tremely important like lan&ing gear.
#arameters Strength Specic Strength 7ensity $ost to Loa& 6earing $apacity 7uctility
7ecreasing Ar&er $omposites B 8igh Strength Steel 'lloys B 2itanium 'lloys B 'luminum 'lloys $omposites B 2itanium alloys B 8igh Strength Steel alloys B 'luminum 'lloys Steel 'lloys B 2itanium 'lloys B 'luminum 'lloys B $omposites $omposites B 2itanium 'lloys B 'luminum 'lloys B 8igh Strength Steel 'lloys 'luminum 'lloys B Steel 'lloys B 2itanium 'lloys BBB $omposites
'luminum alloys ith their very goo& specic strength can %e a goo& su%stitute of steel for making the chassis. 2he skin panels of a carCs %o&y &o not e:perience much loa& (e.g hoo&9 fen&er panels9 &oor panels9 roof) an& therefore9 can easily %e su%stitute& ith 'luminum alloy panels for attaining eight re&uction. Lo stress areas like the col9 inner &oor panels9 @oor of the un&er%o&y9 si&e etc. that e:perience me&ium stress levels can also use 'luminum ithout a;ecting the %o&yCs structural integrity. 8oever9 'luminum oul&nCt have a&e=uate toughness for high stress areas like suspension an& engine mounts9 frontal portion (critical for crash orthiness). 'lso9 for achieving the same strength as steels9 a thicker gauge oul& %e re=uire& hich ill make Doining process more pro%lematic. 8igh strength steels might %e more suita%le for such areas for attaining eight re&uction. 'nother pro%lem oul& %e the choice of Doining process. $urrently9 resistance spot el&ing is the most i&esprea& practice in the in&ustry. 8oever9 'luminum re=uires very high electric current for el&ing. 6esi&es9 presence of o:i&e layer on 'luminum sheets &rastically re&uces the el&a%ility of sheet panels.
