Exam 3 Flashcards
(228 cards)
1
Q
Alloys containing more than 50wt.% Fe
A
Ferrous Alloys
2
Q
Alloys containing less than 50wt.% Fe
A
Nonferrous Alloys
3
Q
Based on carbon content:
(< 0.008wt% C)
A
Pure iron
4
Q
Based on carbon content:
0.008 ~ 2.14wt% C
A
Steels
5
Q
In most steels the microstructure consists of both
A
a and Fe3C phases
6
Q
Carbon concentrations in commercial steels rarely exceed
A
1.0 wt%
7
Q
Based on carbon content:
2.14 ~ 6.70wt% C
A
Cast irons
8
Q
Commercial cast irons normally contain less than
A
4.5wt% C
9
Q
Less than 0.25 wt%C, containing only residual concentrations of impurities and a little manganese.
A
Plain carbon steels
10
Q
About 90% of all steel made is
A
carbon steel
11
Q
more alloying elements are intentionally added in specific concentrations
A
Alloy steels
12
Q
What are the 3 Ferrous Alloys — Steels?
A
Plain carbon steels
Alloy steels
Stainless steels
13
Q
The first two digits indicate the
A
alloy content
14
Q
The last two digits indicate the
A
the carbon concentration
15
Q
For plain carbon steels, the first two digits are
A
1 and 0
16
Q
alloy steels are designated by
A
other initial two-digit combinations (e.g., 13, 41, 43)
17
Q
The third and fourth digits represent
A
the weight percent carbon multiplied by 100
18
Q
For example, a 1040 steel is
A
a plain carbon steel containing 0.40 wt% C
19
Q
A four-digit number
A
the first two digits indicate the alloy content; the last two, the carbon concentration
20
Q
AISI
A
American Iron and Steel Institute
21
Q
SAE
A
Society of Automotive Engineers
22
Q
UNS
A
Uniform Numbering System
23
Q
Low-carbon steels
A
Less than 0.25 wt%C
24
Q
Medium-carbon steels
A
0.25 ~ 0.60 wt%C
25
High-carbon steels
0.60 ~ 1.4 wt%C
26
Unresponsive to heat treatments intended to form martensite; strengthening is accomplished by cold work
Low-Carbon Steels
27
Microstructures of low-carbon steel
ferrite and pearlite
28
Relatively soft and weak, but having outstanding ductility and toughness
Low-Carbon Steels
29
Typically, sy = 275 MPa, sUT = 415~550 MPa, and ductility = 25%EL
Low-Carbon Steels
30
Machinable, weldable, and, of all steels, are the least expensive to produce
Low-Carbon Steels
31
Applications for low-carbon steels:
automobile body components, structural shapes, and sheets used in pipelines, buildings, bridges, etc.
32
0.25 ~ 0.60 wt% C
Medium-Carbon Steels
33
May be heat treated by austenitizing, quenching, and then tempering to improve their mechanical
Medium-Carbon Steels
34
Often utilized in the tempered condition
Medium-Carbon Steels
35
Microstructures of medium carbon steel:
tempered martensite
36
Stronger than low-carbon steels and weaker than high-carbon steels
Medium-Carbon Steels
37
Applications for medium-carbon steels:
railway wheels and tracks, gears, crankshafts, and other machine parts and high-strength structural components calling for a combination of high strength, wear resistance, and toughness
38
0.60 ~ 1.4 wt%C
High-Carbon Steels
39
Used in a hardened and tempered condition
High-Carbon Steels
40
Hardest, strongest, and yet least ductile; especially wear resistant and capable of holding a sharp cutting edge
High-Carbon Steels
41
Containing Cr, V, W, and Mo; these alloying elements form very hard and wear-resistant carbide compounds (e.g., Cr23C6, V4C3, and WC)
High-Carbon Steels
42
Applications for high carbon steel:
cutting tools and dies for forming and shaping materials, knives, razors, hacksaw blades, springs, and high-strength wire
43
Stainless steels are selected for their excellent
resistance to corrosion
44
Stainless steels are divided into three classes:
martensitic, ferritic, or austenitic
45
The predominant alloying element in stainless steel is
chromium; a concentration of at least 11 wt% Cr is required
46
The predominant alloying element __________
permits a thin, protective surface layer of chromium oxide to form when the steel is exposed to oxygen
47
Aluminum and aluminum alloys are the most widely used
nonferrous metals
48
strengthened by cold working and alloying
Aluminum alloys
49
Nonheat-treatable: single phase, solid solution strengthening
Aluminum alloys
50
Low density (2.7 g/cm3), as compared to 7.9 g/cm3 for steel
High electrical and thermal conductivity
Resistant to corrosion in some common environments
Easily formed and thin Al foil sheet may be rolled
Al has an FCC crystal structure; its ductility is retained even at very low temperatures
Limitation: low melting temperature (660°C)
Properties of aluminum alloys
51
Al alloys can provide a weight savings of up to ___ compared to an equivalent steel structure
55%
52
________ is used in the manufacture of aircraft and for fuel tanks in spacecraft
Aluminum plate
53
- So soft and ductile that it is difficult to machine
- Unlimited capacity to be cold worked
- Highly resistant to corrosion in diverse environments
Unalloyed copper
54
strengthened by cold working and/or solid-solution alloying
Copper alloys
55
________ and _______ are two common copper alloys
Bronze and brass
56
Applications for copper alloys:
costume jewelry, cartridge casings, automotive radiators, musical instruments, electronic packaging, and coins
57
Bronze is an alloy of _______ and _____.
copper and tin
58
May contain up to 25% tin
Bronze
59
Brass is an alloy of ______
| and ____.
copper
| zinc
60
Contain 5-30% zinc
Brass
61
The zinc ________ the strength of the copper
increases
62
_______ and _______ are also increased by the zinc.
Ductility
| formability
63
Relatively new engineering material that possess an extraordinary combination of properties
Titanium
64
Low density (4.5 g/cm3)
Titanium
65
High melting temperature (1668°C), high elastic modulus (107 GPa)
Titanium
66
What are the limitations of titanium?
- Chemical reactivity with other materials and oxidation problems at elevated temperatures
- Cost
67
What are the applications of titanium?
High-strength prosthetic implants, petroleum & chemical-processing equipment, airframe structural components
68
Most polymers are
hydrocarbons
69
Each carbon singly bonded to four other atoms
Saturated hydrocarbons
70
Example of a Saturated hydrocarbons
Ethane, C2H6
71
Double & triple bonds somewhat unstable – can form new bonds
Unsaturated Hydrocarbons
72
_______ found in ethylene (ethene) - C2H4
Double bond
73
_________ found in acetylene (ethyne) - C2H2
Triple bond
74
two compounds with same chemical formula can have quite different structures
Isomerism
75
Example of Isomerism
C8H18:
normal-octane
2,4-dimethylhexane
76
_______ is a long-chain hydrocarbon
polyethylene
77
Molecular Shape is also known as
Conformation
78
chain bending and twisting are possible by rotation of carbon atoms around their chain bonds
Molecular Shape
79
not necessary to break chain bonds to ________
alter molecular shape
80
two or more monomers polymerized together
Copolymers
81
A and B randomly positioned along chain
random
82
A and B alternate in polymer chain
alternating
83
large blocks of A units alternate with large blocks of B units
block
84
chains of B units grafted onto A backbone
graft
85
Crystallinity in Polymers
- Ordered atomic arrangements involving molecular chains
| - Crystal structures in terms of unit cells
86
Polymer Crystalline regions
- thin platelets with chain folds at faces
| - Chain folded structure
87
Polymers _____ 100% crystalline
rarely
88
in Polymer Crystallinity, it is difficult for all regions of all chains to become ________
aligned
89
Degree of crystallinity is expressed as
% crystallinity
90
Some physical properties depend on
% crystallinity
91
Heat treating causes crystalline regions to _____ and % crystallinity to _______
grow
| increase
92
Some semicrystalline polymers form
spherulite structures
93
Alternating chain-folded crystallites and amorphous regions
Semicrystalline Polymers
94
Spherulite structure for relatively _____ growth rates
rapid
95
Mass of a mole of chains
Molecular weight
96
Not all chains in a polymer are of the
same length
97
there can be a ________ of molecular weights
distribution
98
average number of repeat units per chain
Degree of Polymerization, DP
99
The fracture strengths of polymers is _____ of those for metals
10%
100
Deformation strains for polymers are
> 1000%
101
for most metals, deformation strains are
< 10%
102
Drawing
- stretches the polymer prior to use
| - aligns chains in the stretching direction
103
What are the results of drawing?
- increases the elastic modulus (E) in the stretching direction
- increases the tensile strength (TS) in the stretching direction
- decreases ductility (%EL)
104
Annealing after drawing:
- decreases chain alignment
| - reverses effects of drawing (reduces E and TS, enhances %EL)
105
Predeformation by Drawing
Contrast to effects of cold working in metals
106
Compare elastic behavior of elastomers with the:
- brittle behavior (of aligned, crosslinked & network polymers)
- plastic behavior (of semicrystalline polymers) (as shown on previous slides)
107
-little crosslinking
- ductile
- soften w/heating
- polyethylene
polypropylene
polycarbonate
polystyrene
Thermoplastics
108
- significant crosslinking (10 to 50% of repeat units)
- hard and brittle
- do NOT soften w/heating
- vulcanized rubber, epoxies, polyester resin, phenolic resin
Thermosets
109
Decreasing T
- increases E
- increases TS
- decreases %EL
110
Increasing strain rate
- increases E
- increases TS
- decreases %EL
111
Both Tm and Tg increase with
increasing chain stiffness
112
Chain stiffness increased by presence of
1. Bulky sidegroups
2. Polar groups or sidegroups
3. Chain double bonds and aromatic chain groups
113
formation prior to cracking
Craze
114
What happens during crazing?
- plastic deformation of spherulites
| - formation of microvoids and fibrillar bridges
115
There are two types of polymerization:
- Addition (or chain) polymerization
| - Condensation (step) polymerization
116
Polymer Additives can
Improve mechanical properties, process-ability, durability, etc.
117
Added to improve tensile strength & abrasion resistance, toughness & decrease cost
Fillers
118
What are some examples of Polymer fillers?
carbon black, silica gel, wood flour, glass, limestone, talc, etc
119
- Added to reduce the glass transition temperature Tg below room temperature
- Presence of plasticizer transforms brittle polymer to a ductile one
- Commonly added to PVC - otherwise it is brittle
Plasticizers
120
- can be reversibly cooled & reheated
| i. e. recycled heat until soft, shape as desired, then cool
Thermoplastic
121
- when heated forms a molecular network (chemical reaction)
- degrades (doesn’t melt) when heated
- a prepolymer molded into desired shape, then chemical reaction occurs
Thermoset
122
Polymer Fibers - length/diameter
>100
123
Primary use is in textiles
Polymer Fibers
124
Fiber characteristics:
- high tensile strengths
- high degrees of crystallinity
- structures containing polar groups
125
Polymers fibers are formed by
spinning:
- extrude polymer through a spinneret (a die containing many small orifices)
- the spun fibers are drawn under tension
- leads to highly aligned chains - fibrillar structure
126
Coatings
thin polymer films applied to surfaces – i.e., paints, varnishes
127
- protects from corrosion/degradation
- decorative – improves appearance
- can provide electrical insulation
Coatings
128
bonds two solid materials
Adhesives (adherands)
129
bonding types:
Secondary – van der Waals forces
| Mechanical – penetration into pores/crevices
130
produced by blown film extrusion
Films
131
gas bubbles incorporated into plastic
Foams
132
Limitations of polymers:
- E, σy, Kc, T application are generally small.
| - Deformation is often time and temperature dependent
133
Thermoplastics (PE, PS, PP, PC):
- Smaller E, σy, T application
- Larger Kc
- Easier to form and recycle
134
Elastomers (rubber):
- Large reversible strains
135
Thermosets (epoxies, polyesters):
- Larger E, σy, T application
| - Smaller Kc
136
Polymer Processing:
compression and injection molding, extrusion, blown film extrusion
137
Combination of two or more individual materials
Composite
138
What is the design goal of composites?
obtain a more desirable combination of properties (principle of combined action)
139
Multiphase material that is artificially made
Composite
140
Phase types:
- Matrix - is continuous
| - Dispersed - is discontinuous and surrounded by matrix
141
Purposes of the matrix phase:
- transfer stress to dispersed phase
| - protect dispersed phase from environment
142
Types matrix phase:
MMC, CMC, PMC (metal, ceramic, polymer)
143
Dispersed phase:
| -- Purpose:
MMC: increase σy, TS, creep resist.
CMC: increase Kic ( fracture toughness)
PMC: increase E, σy, TS, creep resist
144
Types of dispersed phase:
particle, fiber, structural
145
Estimate fiber-reinforced composite modulus of elasticity for continuous fibers
Continuous fibers
146
- Continuous fibers pulled through resin tank to impregnate fibers with thermosetting resin
- Impregnated fibers pass through steel die that preforms to the desired shape
- Preformed stock passes through a curing die that is
- -precision machined to impart final shape
- -heated to initiate curing of the resin matrix
Pultrusion
147
- Continuous reinforcing fibers are accurately positioned in a predetermined pattern to form a hollow (usually cylindrical) shape
- Fibers are fed through a resin bath to impregnate with thermosetting resin
- Impregnated fibers are continuously wound (typically automatically) onto a mandrel
- After appropriate number of layers added, curing is carried out either in an oven or at room temperature
- The mandrel is removed to give the final product
Filament Winding
148
- stacked and bonded fiber-reinforced sheets
- stacking sequence: e.g., 0º/90º
- benefit: balanced in-plane stiffness
Laminates
149
honeycomb core between two facing sheets
| - benefits: low density, large bending stiffness
Sandwich panels
150
Costs are not effected by the level of production
Fixed costs
151
Includes both variable and semi-variable costs
Overhead costs
152
costs that are directly affected by the level of production
Variable costs
153
Variable costs
= UC = Total Unit Cost
154
Variable costs that have a minimum fixed value and then a variable component that fluctuates with the production level
Semi-variable costs
155
total income received from sales
Revenue
156
Selling Price times number of units sold
Revenue
157
the money you have after subtracting fixed and variable cost from the revenue
Profit BT
158
the money you have after subtracting fixed and variable cost and Taxes from the revenue
Profit AT
159
purchased material and lower level manufactured parts that include direct labor and overhead
Material
160
Pay to employees who add value to product
| Often paid hourly, or per item, but can be salaried
Direct Labor
161
General term for all other variable costs that are NOT included in material and direct labor
Overhead (OH)
162
labor paid for non value added work such as: moving & stocking material, quality inspection, unloading trucks, receiving material (both purchased and manufactured). Includes fringe benefits
Indirect labor
163
for manufacturing and warehouse areas
Utilities
164
paint, jigs & fixtures, cutting oils, maintenance supplies, shipping supplies not on BOM, bolts, nails, glue not on BOM, etc
Production Supplies
165
shop/warehouse
Janitorial & maintenance Services
166
A decision-making aid for determining whether a particular production or sales volume will result in losses or profits
Break-Even Analysis
167
What is the break-even analysis used for?
Used to see if your income is more than your expense
Determine minimum price a product can be sold for
Determine the minimum quantity of sales
168
How do you set a selling price?
Need to know the Unit Cost = M, L, OH
| Determine the margin profit
169
Based on competitive strategy
margin profit
170
Based on who you are selling to
margin profit
171
- Technique for evaluating process and equipment alternatives
- Objective is to find the point in dollars and units at which certain costs equals revenue
- Requires estimation of fixed costs, variable costs, and revenue
Break-Even Analysis
172
Revenue function begins at the _____ and proceeds ____ to the _____, increasing by the selling price of each unit
origin
upward
right
173
Where the revenue function crosses the total cost line is the
break-even point
174
What are the assumptions of a break-even analysis?
- Costs and revenue are linear functions
- -Generally not the case in the real world
- We actually know these costs
- -Although sometimes difficult to verify
- Time value of money is often ignored
175
Two basic approaches to Break-Even
- Fixed time period with variable production rate
| - Fixed production rate with variable time period
176
The _________ is traditionally used
Fixed Time Period
177
Four different Break-Even Points:
- Shutdown Point
- Break-Even at cost
- Break-Even at required return
- Break-Even at required return after taxes
178
When the total revenue is equal to sum of variable and semivariable costs
Shutdown Point
179
When the total revenue is equal to total costs (variable, semi-variable, and fixed)
Break-Even at cost
180
When the total revenue is equal to the total costs plus the required return
Break-Even at required return
181
When the total revenue is equal to the total costs plus the required return plus the taxes on the required return
Break-Even at required return after taxes
182
Revenue (shutdown point) =
Variable costs + Semi-variable costs
183
Revenue (Break-Even Analysis: At Cost) =
Total costs =Fixed costs + Variable costs +Semi-variable costs
184
Revenue (At Required Return) =
Total cost + Required return
185
Revenue (At Required Return) =
Fixed costs + Variable costs + Semi-variable costs + Required return
186
Revenue (At Required Return After Tax) =
Total cost + Required return + Taxes on the required return
187
General expression to determine material cost:
C(u) = C(w) x W
188
C(u)
total unit cost, $
189
C(w)
cost per unit weight, $/weight ($/kg, $/lb)
190
W
weight (k,lb)
191
Weight can be expressed by:
W = d x V
192
d
density, weight/unit volume (kg/m^3, lb/in^3)
193
V
volume (m^3, in^3) `
194
Thus expression transforms to:
C(u) = C(w) x d x V
195
Volume can be expressed by:
V = L x A
196
L
design length (m, in)
197
A
design cross-sectional area (m^2, in^2)
198
Thus expression transforms to again:
C(u) = C(w) x d x L x A
199
Cross-sectional area frequently involved in
basic design relationships
200
Cross sectional area
usually determined by design requirements
201
Two of the most common design requirements are:
1) The product must support a design load (strength requirement)
2) The product is to be restricted in the amount of deflection (stiffness requirement)
202
Design relationships for cross-sectional area (A)
must be developed
203
Design relationship for simple tension in a solid bar:
S = P/A or A = P/S
204
S
material strength (MPa, kpsi)
205
P
load (kN, lb)
206
A
cross sectional area (m^2, in^2)
207
Sometimes a design calls for materials when
COST is not critical for a solid rod, bar or cylinder
Examples would be:
- Airplane / aerospace industry
- Hospital equipment (implants use Titanium…)
- Sports Equipment (bikes, carabiners…)
208
For more complex loadings than simple tension the expression in return is
more complex
209
In cases with multiple constraints (e.g., load AND elongation),
critical cross-sectional areas must be calculated
210
Cost performance is only comparable for
same criteria (that is, loading)
211
In cases where load is critical for one material and elongation for another ->
ratio should not be used
212
What type(s) of bonds is (are) found between atoms within hydrocarbon molecules?
Covalent bonds
213
How do the densities compare for crystalline and amorphous polymers of the same material that have identical molecular weights?
Density of crystalline polymer > density of amorphous polymer
214
Significant tensile deformation of a semicrystalline polymer results in a highly-oriented structure (T or F)
True. Significant tensile deformation of a semicrystalline polymer results in a highly-oriented structure
215
How does annealing an undeformed semicrystalline polymer affect its yield strength?
Annealing an undeformed semicrystalline polymer produces an increase in its tensile strength
216
Which of the following factor(s) favor(s) brittle fracture in polymers?
* Increasing in temperature.
* Increasing in strain rate.
* The presence of a sharp notch.
* Decreasing specimen thickness.
- Increasing strain rate
- the presence of a sharp notch
- decreasing temperature
217
The bonding forces between adhesive and adherend surfaces are thought to be
* Electrostatic
* Covalent
* Chemical
electrostatic
218
Deformation of a semicrystalline polymer by drawing produces what?
- an increase in strength in the direction of drawing
| - a decrease in strength perpendicular to the direction of drawing
219
How does deformation by drawing of a semicrystalline polymer affect its tensile strength?
increases the tensile strength
220
How does increasing the degree of crystallinity of a semicrystalline polymer affect its tensile strength?
leads to an increase in its tensile strength. This is due to enhanced interchain bonding and forces in crystalline regions; in response to applied stresses, interchain motions become more restrained as degree of crystallinity increases
221
How does increasing the molecular weight of a semicrystalline polymer affect its tensile strength?
The tensile strength of a semicrystalline polymer increases with increasing molecular weight. This effect is explained by the increased chain entanglements at higher molecular weights
222
In order for a polymer to behave as an elastomer, what is necessary?
In order for a polymer to behave as an elastomer
* It must not crystallize easily
* Chain bond rotations must be relatively free
* The polymer must be above its glass transition temperature
223
A random and lightly crosslinked copolymer that has a glass-transition temperature of –40°C is an _______ since it is a random copolymer (i.e., is highly noncrystalline), is lightly crosslinked, and is above its glass transition temperature.
elastomer
224
A branched and isotactic polypropylene that has a glass-transition temperature of –10°C is a __________ since it has a branched structure.
thermoplastic
225
The polyethylene that has a glass-transition temperature of 0°C is a _________ since it is heavily crosslinked.
thermoset (nonelastomer)
226
Linear polyvinyl chloride that has a glass-transition temperature of 100°C is a __________ since it has a linear structure.
thermoplastic
227
What is the definition of glass transition temperature?
The glass transition temperature is the temperature at there is a slight decrease in slope of the temperature versus specific volume curve.
228
There is a definite temperature at which a liquid transforms to a glassy (or noncrystalline) solid. (T or F)
False. Unlike crystalline materials, a glassy or noncrystalline material does not transform into a solid at a definite temperature. Rather, upon cooling from the liquid, a glass becomes more viscous as the temperature decreases.
