Home
Introduction
Policies
Requirements &
Grading
Resources
Syllabus
Assignments
Handouts
Discussion
Web Links
Distance
Learners
Contact
TEST#2
MSE 200 Test#1 , November 8, 2001 , S.S.No:
Read the questions carefully and answer on the backside also. A set of
formulae are given at the end that may be useful.
Q1. A sample of cross sectional area 0.1 sq. inches has been subjected to a
tensile test. The load versus elongation curve is shown below. Identify the
proportional limit, UTS, and fracture point in the load elongation graph.
Calculate, the engineering stress, engineering strain, true stress, and true strain
at the point of necking. Calculate the total elongation of the sample and
fracture stress. Points:10
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
length at UTS= l=2.14 inch, initial length=lo=2, engineering
strain=0.14/2=0.07
Load at UTS=8000, Initial area of crosssection=0.1 sq.in, engineering
stress=8000/0.1=80000 psi
True strain at UTS=ln(l/lo)=ln(2.14/2)=0.0677
True stress at UTS= Engineering stress x(1+engineering strain)
=80000(1+0.07)=85600 psi
Total elongation= 2.22+0.012.008(0.001)=0.223
Total engineering strain =0.111
Fracture stress=(1.111)x7500/(0.1)=82500 psi
Q2. A high strength steel has a yield point of 1460 MPa and a critical fracture
toughness of 98 MPa(m)
1/2
. Calculate the size of the crack that will lead to
catastrophic failure at an applied stress of (1/2)Yield strength.Points:5
σ
ys=1460 Mpa, KIC=98 Mpa(m)
1/2
=
σ
f(
π
c)
1/2
σ
f=1460/2 Mpa, c=0.0014 m
Q3. In a laboratory creep experiment at 1000
o
C, a steady state creep rate of
1.5x10
6
sec
1
is observed. When the experiments are performed at 800
o
C, the
observed creep rate is 1.0x10
6
sec
1
. Predict the creep rate at a service
temperature of 600
o
C. Points 8
Strain rate
ε
'=
ε
o'exp(Q/kT),
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '08
 wholedepartment
 Materials Science, coherent, 2 K, Q7., crosssection=0.1 sq.in

Click to edit the document details