Page 68 - Analysis and Design of Machine Elements

Analysis and Design of Machine Elements
46
Steps Computation Results Units

2. Calculate −1e and −1Ne The endurance limit of the machine element −1e = 320 MPa

= −1 = 480 = 320MPa
−1e K 1.5

The endurance strength of the machine element −1Ne = 413.29 MPa
for a finite life
−1N 619.94
−1Ne = = = 413.29MPa
K
1.5
3. Draw − diagram Draw a − diagram for the infinite life of the
m a m a
for the element, as shown element A D C through (0, ).
e e −1e
in Figure E2.1
Draw a − diagram for the finite life of the
m a
element A D C,where A D is parallel
Ne Ne Ne Ne
to A D from (0, )
e e −1Ne
The slope of these lines is
0.2
′
tan = = = 0.133
K 1.5

σ
a
700
Finite life of material
(0, σ –1N ) A N α
600
D N
Infinite
life of material
500 α
(0,σ ) A
–1
(0, σ ) A
–1Ne Ne α′ D
400
D Ne
(0, σ –1e ) A e α′ Finite life of the element
300 M″
Infinite life of the element D
M′ e
200
M

100
C
0 100 200 300 400 500 600 700 800 900 σ
m
Figure E2.1 Endurance limit diagram for Example Problem 2.1.