Solution for Tutorial Four
MECH2100, 2011
1
The University of Queensland
School of Engineering
MECH2100  Machine Element Design
Solution for Tutorial Four 2011
Q1:
This figure shows the Constant Life Fatigue Diagram. The Yaxis is
Alternating stress
and the Xaxis is
Tensile mean stress
. Point A is
Yield strength
, Point B is
Endurance
limit
, Point C is
Yield strength
, and Point D is
Ultimate tensile strength
. Line a is
Yield line
, line b is
Goodman line
, line c is
Load line
and line BEC is
Modified
Goodman line
.
Q2:
Therefore, we will start with an uncorrected endurance limit of
[0.5]
times the ultimate
tensile strength. This needs to be corrected using the correction factors in Juvinall Table
8.1. Load factor C
L
[1.0];
gradient factor C
G
=0.6; surface factor C
S
[0.9]
; temperature
factor C
T
[1.0]
and reliability factor C
R
[0.81].
The corrected endurance limit is then
found as [
none of the above
].
Q3: Sn’=1.0 x 0.6 x 0.9 x 1.0 x 0.81 x (0.5 x 700) = 153.09 (MPa)
Q4:
S
1000
= 0.9 Su = 630 MPa.
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 Three '11
 BillDaniel
 Stress, Tensile strength, yield strength, endurance limit, Tensile mean stress

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