EMA 4223
Mechanical Behavior of Materials
February 19, 2010
Test 2A
Name _
1. The bond energy curves for three engineering materials are shown in the figure. Select the best material for
use in each application described below by circling your choice.
i.

8.2
Explain why FCC metals show a ductile fracture even at low temperatures,
while BCC metals do not.
FCC metals show ductile fracture at low temperatures while BCC metals do not
because of the fact that there are many more slip systems in FCC metals that

EMA 4223 Test 2A
Mechanical Behavior of Materials
February 23, 2016
Name _
Each Question is worth 20 points unless noted.
1. A polycrystalline metal has a plastic stress-strain curve that obeys the Hollomon-Ludwik equation, = K n.
Determine n, knowing tha

9.1 A Charpy machine with a hammer weighing 200N has a 1-m long arm. The initial
height ho is equal to 1.2m. The Charpy specimen, (See Figure 9.2), absorbs 80J of energy
in the fracturing process. Determine:
(a) The velocity of the hammer upon impact with

7.24
Using the Weibull Equation, establish the tensile strength, with a 50% survival
probability, of specimens with a length of 60mm and a diameter of 5mm. Uniaxial
tensile tests carried out on specimens with a length of 20mm and the same
diameter yielded

EMA 4223
Mechanical Behavior of Materials
February 18, 2010
Test 2B
Name _
1.
A steel with a yield stress of 300 MPa is tested under a state of stress where 2 = 1/2 and 3 = 0. .(25 points)
What is the stress at which yielding occurs if it is assumed that:

Equations for Test 2 Examination
u = ln [(A0)/Au]
1 + 2 + 3 = 0
K (ddt)m
F/A = H = 30
+ K n (Holloman-Ludwik Eq.)
t = (dt / dt ) [at necking]
u = n
G = E / [2(1+]
= 0 + G b ()1/2
t = [P/A0] exp(t) = e (1 + e)
= [d/dt]= (dv/dy)
t = ln (1 + e) = ln (L/L

Plot the stress-strain curve for alumina in tension, knowing that the density of
microcracks increases linearly with stress (N= k ). The grain size is 20 m. The
failure stress is 1 GPa; given k = 5.45 x 104 m3/Pa, Eo =420 GPa.
2.48
Given: Grain size: 20 m

Equations for Test 1 Examination
u = ln [(A0)/Au]
1 + 2 + 3 = 0
K (ddt)m
= M/V
V = A0L0 = AL (constant volume)
G = E / [2(1+]
vl = (E)1/2
t = [P/A]
e = [P/ A0]
t = ln (1 + e) = ln (L/L0)
n = e = l/lo
E = ; G =
A exp [ Q/RT]
exp(t) = e (1 + e)
= [d/dt]

EMA 4223 Test 2
Mechanical Behavior of Materials
Example
Name _
Each Question is worth 20 points unless noted.
1. A polycrystalline metal has a plastic stress-strain curve that obeys the Hollomon-Ludwik equation, = K n.
Determine n, knowing that the flow

EMA 4223
Mechanical Behavior of Materials
Date
Test 1B
Name _
1. .[15 points] (a) Sketch the specific volume as a function of temperature for an amorphous material and for a
crystalline material for two different cooling rates, i.e., rapid and slow. Indic

Review for Test 2 Covering Chapters 3, 4, 5 & 6 in Meyers and Chawla + Notes.
1. Generally know the classification of defects (i.e., 0, 1, 2 & 3-D) and be able to identify examples.
a. Atomic/point defects (0D)
i. Types
1. Vacancy
a. An atomic position in

6.16
The flow stress is given:
i G b () 1/2
Experimental observation (p.351) = k /D where k is a constant and D is grain size
i G b (k/D) 1/2
This is in the form of
ik (D) -1/2 where k = G b k1/2
Q.E.D.
6.18
= 25 MPa + 200 0.5 MPa
The area under the true

3.1 A polycrystalline metal has a plastic stress-strain curve that obeys Hollomons equation.
= K n
Determine n, knowing that the flow stresses of this material at 2% and 10% plastic deformation (offset) are equal to 175
and 185 MPa, respectively.
At 2% s

Problem 1.15 Different polymorphs of a material can have different mechanical properties. Give some
examples.
A.
There are a number of answers possible. One example is zirconia. Zirconia at room
temperature is monoclinic and easily cracks. Zirconia transi

f,t t", Z Failure by generalyield or fast fracture
plotted against crack
Figure 16.7 shows the loci of general yielding and fast fracture
and is simPlY given b1'
size. The yield locus is obviousiy independent of crack size,
+
G e n e r o ly i e l d r n g

EMA 4223
Mechanical Behavior Test 3A
April 2, 2015
Name _
1(a)An engineering ceramic has a flexure strength that obeys Weibull statistics with m = 10. If the flexure strength is equal
to 200 MPa at 50 % survival probability, what is the flexure strength l

EMA 4223
Mechanical Behavior of Materials
February 18, 2010
Test 2A
Name _
1. The curve of true stress against true strain for a metal wire approximates to:
= (10 + 350 0.4) MPa.
Estimate the work required to take 1 m3 of the wire to necking. (25 points)

EMA 4223
Mechanical Behavior of Materials
Test 3 C
Name _
Each question is worth 25 points (except as noted).
1. Sketch the general yield and fast fracture loci for a pressure-vessel steel ( KIC = 170 MPa m1/2, y = 1000
MPa ) and an aluminum alloy ( KIC =

EMA 4223
Mechanical Behavior Test 4A
April 21, 2015
Name_
Each Question is worth 25 points unless noted.
1. Estimate the minimum specimen thickness for a valid plane-strain fracture toughness test for a material having the
following properties: yield stre

EMA 4223
Mechanical Behavior Test 3B
April 2, 2015
Name _
1 You are offered an opportunity to earn $10 million by simply hanging on a rope for only one minute. The rope is
attached to a glass sheet (300 cm long by 10 cm wide and 0.127 cm thick). Complicat

EMA 4223
Mechanical Behavior of Materials
February 5, 2015
Test 1A
Name _Solutions_
1. [25 points] For the FCC Copper structure calculate the angle between the [111] and [112] directions, respectively.
The atomic mass (or weight) of copper is 63.54 g /g.

7.1 In a polyvinyl chloride (PVC) plate, there is an elliptical, tbrough-the-thickness
cavity. The dimensions of the cavity are:
Major axis = Imm,
Minor axis = O.lmm.
Compute the stress concentrationfactor Kt, at the extremities of the cavity.
Solution
K

Materials Selection: General
Role of Materials Selection
There are more than 50,000 materials available to an
engineer
Need a rational procedure to select materials
Role of Materials Selection in DESIGN
When designing a new material, you need a place to s

Topics Covered on Exam 2
1. Chapter 4 I mperfections: Point and Line Defects
a. Types of defects: point, line, interfacial, volume
b. Theoretical strength of materials
c. Point defects
i. Types of atomic defects: vacancy, interstitial, substitutional, Fre

EMA 4223
Mechanical Behavior
April 21, 2015
Example Test 4
1.A large thick plate of steel is examined by X-ray methods and found to contain no detectable cracks. The
equipment can detect a single edge-crack of depth a = 1 mm or greater. Laboratory tests s

EMA 4223
Mechanical Behavior of Materials
Test 3 Example
Name _
Each Question is worth 20 points unless noted.
1. Can you suggest a quick technique to check weather lines observed in an optical microscope on the surface of a
polished sample after deformat

A large thick plate of steel is examined by X-ray methods and
Indicate briefly how and why the following would
found to contain no detectable cracks. The equipment can detect
affect the fatigue life of components:
a single edge-crack of depth a = 1 mm or