Page 47 - Analysis and Design of Machine Elements

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Strength of Machine Elements

Nomenclature endurance limit at r = 0, MPa
0
principal stresses, MPa
1,2,3
b cylinder length, mm a stress amplitude, MPa
E elasticmodulus,MPa b ultimate, or tensile strength, MPa
F force, N ca calculated tensile stress, MPa
K A service factor, or application factor e equivalent stress, MPa
K combined influence factor material strength, MPa
k f fatigue stress concentration factor lim mean stress, MPa
k geometric stress concentration m
t max maximum stress, MPa
factor
min minimum stress, MPa
k fatigue stress concentration factor endurance limit at stress ratio r,
in tension r
MPa
k fatigue stress concentration factor
in shear rN endurance strength at r and N,
m material constant MPa
N number of load cycles r∞ endurance limit, or fatigue limit,
MPa
N critical number of cycles
0
N equivalent number of cycles s yield strength in tension, MPa
v
q notch sensitivity factor [ ] allowable tensile stress, MPa
r stress ratio shear stress, MPa
S safety factor −1 endurance limitinshear,MPa
S calculated safety factor max maximum shear stress, MPa
ca
[S] allowable safety factor s yield strength in shear, MPa
intensify factor [ ] allowable shear stress, MPa
q
surface condition factor for tension mean stress influence factor

size factor for tension Subscripts
Poisson’s ratio −1 completely reversed stress
radius of curvature, mm
tensile stress, MPa 0 repeated stress
a stress amplitude
endurance limit of a material at
−1
r =−1, MPa e material properties of an element
endurance limit of an element at m mean stress
−1e
r =−1, MPa x,y,z coordinates
−1Nv endurance strength at r =−1and tensile stress, MPa
N = N ,MPa shear stress, MPa
v
Analysis and Design of Machine Elements, First Edition. Wei Jiang.
© 2019 John Wiley & Sons Singapore Pte. Ltd. Published 2019 by John Wiley & Sons Singapore Pte. Ltd.
Companion website: www.wiley.com/go/Jiang/analysis_of_machine_elements