LECTURE 12.2. LECTURE OUTLINE Lesson 12 Quiz Feedback Lesson 12 Quiz Feedback Ashby Maps Ashby Maps.

LECTURE 12.2LECTURE 12.2

LECTURE OUTLINELECTURE OUTLINE

Lesson 12 Quiz FeedbackLesson 12 Quiz FeedbackAshby MapsAshby Maps

Table 1.

Selected Physical and Mechanical Properties of Various Materials Material Melting Point

(˚C) Specific Gravity (Density)

Young's Modulus (GPa)

Mohs Hardness

Metals Aluminum 660 2.7 70 ~2.5 Copper 1085 8.9 115 ~3 Tungsten 3410 19.3 407 ~5 Ceramics Alumina 2045 4.0 400 9 Mullite 1830 3.1 145 5 Soda-Lime Glass ~1000 2.5 70 5.5 Polymers LDPE ~115 ~0.92 0.25 < 2 HDPE ~137 ~0.95 1.05 < 2 Nylon ~265 1.14 1.6-3.8 < 2

Q1. Table 1 shows some of the materials that were listed as Table 3.4 in the book. Use this information to answer the following question.The object is to design a scratch resistant countertop for the kitchen. Which material would be employed for maximum scratch resistance?<a> Soda-Lime Glass HDPE<c> Tungsten<d+> Alumina<e> Mullite

Table 1.

Selected Physical and Mechanical Properties of Various Materials

Material Melting Point(˚C)

Specific Gravity(Density)

Young's Modulus(GPa)

Mohs'Hardness

MetalsAluminum 660 2.7 70 ~2.5Copper 1085 8.9 115 ~3Tungsten 3410 19.3 407 ~5

CeramicsAlumina 2045 4.0 400 9Mullite 1830 3.1 145 5Soda-Lime Glass ~1000 2.5 70 5.5

PolymersLDPE ~115 ~0.92 0.25 < 2HDPE ~137 ~0.95 1.05 < 2Nylon ~265 1.14 1.6-3.8 < 2

Q2. Table 1 presents some property measurements for a series of materials, while Figure 1 plots the Young's moduli of these materials as a function of their specific gravities. The line P passes through the datum point for our benchmark material: aluminum. The datum point marked A on Figure 1 corresponds to _______.<a+> alumina tungsten<c> copper<d> mullite<e> nylon

Q3. Table 2 presents atomic numbers (At #), melting points (MP), specific gravities (SG), and Mohs Hardness values (H) for a series of metals and their corresponding oxides.

The specific gravity of a metal oxide increases as the specific gravity of the metal increases.

<a> Always true

<b+> Sometimes false

Metal At# MP(˚C)

H SG CeramicOxide

MP(˚C)

H SG

Magnesium(Mg)

12 650 2.5 1.74 Periclase(MgO)

2800 5.5 3.65

Aluminum (Al) 13 660 2.5 2.70 Corundum(Al2O3)

2050 9.0 4.0

Titanium (Ti) 22 1668 3.5 4.51 Rutile (TiO2) 1640 6.25 4.26

Manganese (Mn) 25 1244 3.5 7.47 Pyrolusite(MnO)

1840 6.25 5.43

Iron (Fe) 26 1538 3,5 7.87 Magnetite(Fe3O4)

1700 6.00 5.7

Copper (Cu) 29 1085 3.0 8.93 Cuprite(Cu2O)

1235 3.75 6.0

Zinc (Zn) 30 420 2.75 7.13 Zincite(ZnO)

1800 4.25 5.6

Tin (Sn) 50 232 2.0 5.77 Cassiterite(SnO2)

1127 6.5 7.0

Uranium (U) 92 1132 4.5 19.0 Uraninite(UO2)

2176 5.5 10.95

Q4. Table 2 presents some properties of a variety of materials. Corundum is a ________.<a> metal<b+> ceramic<c> polymer<d> composite<F> Corundum is a compound; it is non-metallic and inorganic; it is an oxide-ceramic.

Metal At# MP(˚C)

H SG CeramicOxide

MP(˚C)

H SG

Magnesium(Mg)


2800 5.5 3.65


2050 9.0 4.0



1840 6.25 5.43


1700 6.00 5.7


1235 3.75 6.0


1800 4.25 5.6


1127 6.5 7.0


2176 5.5 10.95

Q5. Table 2 presents some properties of a variety of materials. Corundum is an ore for which metal?

<a> Magnesium

<b+> Aluminum

<c>Manganese

<d> Iron

<e> Copper

Metal At# MP(˚C)

H SG CeramicOxide

MP(˚C)

H SG

Magnesium(Mg)


2800 5.5 3.65


2050 9.0 4.0



1840 6.25 5.43


1700 6.00 5.7


1235 3.75 6.0


1800 4.25 5.6


1127 6.5 7.0


2176 5.5 10.95

Q6. Figure 2 shows the variation in the specific strengths of a series of composites (also see Chapter 27) as a function of the percent of glass fiber in the composite.

In order to attain a specific strength of approximately 105 MPa, the % fiber should be about _______.<a> 10 20<c> 30<d+> 40<e> 50

Table 3.

Selected Materials and Selected Physical/Mechanical Properties.

Material Specific Gravity Young's Modulus(GPa)

Approximate YieldStrength. (MNm-2).

Alloy Steel 7.8 200 1000Aluminum Alloys 2.7 69 500Titanium Alloys 4.5 120 1000Beryllium Alloys 1.9 300 250

Wood 0.6 12 40Polyurethane Foam 0.1 6 1

Concrete 2.5 47 25Alumina 3.9 390 400

GFRP* 2.0 40 200CFRP** 1.5 270 650

Q7. Table 3 presents the specific gravities, Young's moduli, and yield strengths for a series of materials.The specific modulus of an alloy steel is approximately _______.<a+> 26 MPa 13 GPa<c> 128 GPa<d> 260 GPa<e> 1280 GPa

Table 3.







GFRP* 2.0 40 200CFRP** 1.5 270 650

Q8. Table 3 presents some property measurements for a series of materials, while Figure 3 plots the yield strengths of these materials as a function of their specific gravities. The line P passes through the datum point for our benchmark material: aluminum. The datum point marked A on Figure 3 corresponds to ______.<a+> CFRP titanium alloys<c> alloy steel<d> alumina<e> GFRP

Q10. The semiconductor gallium arsenide (GaAs) has a specific gravity of about 5.5 and a Young's modulus of approximately 100 GPa.

Is gallium arsenide a better or worse choice than aluminum (our benchmark material) for an aircraft wing—based on specific stiffness alone?

<a> Better

<b+> Worse

Table 1.

Selected Physical and Mechanical Properties of Various Materials

Material Melting Point(˚C)

Specific Gravity(Density)

Young's Modulus(GPa)

Mohs'Hardness

MetalsAluminum 660 2.7 70 ~2.5Copper 1085 8.9 115 ~3Tungsten 3410 19.3 407 ~5

CeramicsAlumina 2045 4.0 400 9Mullite 1830 3.1 145 5Soda-Lime Glass ~1000 2.5 70 5.5

PolymersLDPE ~115 ~0.92 0.25 < 2HDPE ~137 ~0.95 1.05 < 2Nylon ~265 1.14 1.6-3.8 < 2

Q11. Table 1 presents some property measurements for a series of materials, while Figure 1 plots the Young's moduli of these materials as a function of their specific gravities. The line P passes through the datum point for our benchmark material: aluminum. Which of the following materials would have a superior performance index for application as an aircraft wing, for which a high value of Young's modulus and a low value of specific gravity are desirable?

<a+> Alumina

 Tungsten

<c> Nylon

<d> Copper

PERFORMANCEPERFORMANCE

Ashby MapsAshby Maps

THE MATERIALS SCIENCE THE MATERIALS SCIENCE TETRAHEDRONTETRAHEDRON

A “PERFORMANCE INDEX”A “PERFORMANCE INDEX”

Define a “performance index” as strength Define a “performance index” as strength (hardness)/ unit weight, or(hardness)/ unit weight, or

Specific Strength = HardnessSpecific Strength = Hardness

Specific GravitySpecific Gravity

SPECIFIC STRENGTH/SPECIFIC SPECIFIC STRENGTH/SPECIFIC STIFFNESSSTIFFNESS

Weight-limited design!Weight-limited design!Suppose that we have two materials, A and B, Suppose that we have two materials, A and B,

and that A has a yield strength of 200 MPa and and that A has a yield strength of 200 MPa and B has a yield strength of 100 MPa.B has a yield strength of 100 MPa.

Could I replace material A with material B for Could I replace material A with material B for something such as the fuselage of a something such as the fuselage of a commercial aircraft? commercial aircraft?

I would need “struts”of material B that were I would need “struts”of material B that were twice as thick as “struts” of material A. Is this twice as thick as “struts” of material A. Is this a problem?a problem?

SPECIFIC STRENGTH/SPECIFIC SPECIFIC STRENGTH/SPECIFIC STIFFNESS IISTIFFNESS II

Answer: It depends on the specific gravity of the Answer: It depends on the specific gravity of the two materials!two materials!

Case #1: Material B has a specific gravity ~ 0.33 x Case #1: Material B has a specific gravity ~ 0.33 x that of material A. Even though the struts must be that of material A. Even though the struts must be twice as thick, they will still weigh less than the twice as thick, they will still weigh less than the smaller struts of Material A.smaller struts of Material A.

Case #2: Material B has the same specific gravity Case #2: Material B has the same specific gravity as Material A. The struts of Material B will now as Material A. The struts of Material B will now weigh twice that of Material A.weigh twice that of Material A.

SPECIFIC STRENGTH/SPECIFIC SPECIFIC STRENGTH/SPECIFIC STIFFNESS IIISTIFFNESS III

ConclusionConclusion A more important parameter than “strength” is “specific A more important parameter than “strength” is “specific

strength,” where:strength,” where: Specific strength is the strength/unit weight, or:Specific strength is the strength/unit weight, or: Specific Strength = Yield StrengthSpecific Strength = Yield Strength


Also:Also:

Specific Stiffness = Young’s ModulusSpecific Stiffness = Young’s Modulus


SELECTED PROPERTIES OF SELECTED PROPERTIES OF SELECTED MATERIALSSELECTED MATERIALS

Table 36.1.







GFRP* 2.0 40 200CFRP** 1.5 270 650

SELECTED PROPERTIES OF SELECTED PROPERTIES OF SELECTED MATERIALSSELECTED MATERIALS

TOWARD THE ASHBY MAP”TOWARD THE ASHBY MAP”

EE// = = qq ““q” is a “number” that can be q” is a “number” that can be

used as a benchmark. used as a benchmark. Materials with a larger value Materials with a larger value of “q” will have a better of “q” will have a better “specific stiffness” than our “specific stiffness” than our benchmark, whereas materials benchmark, whereas materials with a lower value of “q” will with a lower value of “q” will be inferior.be inferior.

We can plot the straight line:We can plot the straight line: E E = = qq

Materials above this line are Materials above this line are superior; those below are superior; those below are inferior.inferior.

a

E Benchmark Material

A “PROPERTY MAP”A “PROPERTY MAP”

TOWARD THE ASHBY MAPTOWARD THE ASHBY MAP

Reminder:Reminder: EE// = = qqWhen values ofWhen values of

EE// varyvary over orders over orders of magnitude, it is of magnitude, it is necessary to use a necessary to use a “log-log” plot and:“log-log” plot and:

logE logE = = loglog + + loglogq q y = mx + Cy = mx + C

a

loglogq“ ” Benchmark Material

LINEAR AND LOG-LOG LINEAR AND LOG-LOG PERFORMANCE MAPSPERFORMANCE MAPS

AN ASHBY MAPAN ASHBY MAP

LECTURE 12.2. LECTURE OUTLINE Lesson 12 Quiz Feedback Lesson 12 Quiz Feedback Ashby Maps Ashby Maps.

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