This pdf deals with various problems on principle stress acting on machine members in machine design with illustrative examples for better understanding the concepts.
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ME8593-DME UNIT1-Principal stress problems on machine design
1. VELAMMAL INSTITUTE OF TECHNOLOGY
Department of Mechanical Engineering
III YEAR V SEM A SECTION
ME 8593-DESIGN OF MACHINE ELEMENTS
UNIT 1
Presented by,
K.Balamanikandasuthan,
Assistant Professor, Mechanical
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
2. Topics going to discuss
• Prefered Numbers
• Problems on principle stresses
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
3. Prefered Numbers
Standardization reduces number of sizes and variety of items to reduce
cost and improve quality. These sizes are expressed numerically and are
called preferred numbers
Large number of sizes is reduced to a smaller number of sizes by the use
of Renard numbers in FIVE GEOMETRIC SEQUENCES
It consist of R5,R10,R20,R40 and R80 series.
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
5. PSGDDB Pg No 7.20
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
6. Calculation of principle stresses for
various load combinations
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
7. Points remember in Principle stress
• PSGDDB Page No:7.2
• When ever the normal stress(σ) combined with shear
stress (τ)we will apply principle stress formula for
finding the maximum, minmum principal stress and
maximum shear stress.
• Ex: σa + τ (or) σb + τ
• σa =Axial or direct stress, σb =Bending stress
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
9. Q1. A hollow shaft of 40 mm outer diameter and 25 mm inner diameter is
subjected to a twisting moment of 120 N-m, simultaneously, it is subjected to
an axial thrust of 10 kN and a bending moment of 80 N-m. Calculate the
maximum compressive and shear stresses
Note: Principle stresses formulas from PSGDDB Page No:7.2
Given:
do = 40 mm ;
di = 25 mm ;
T = 120 N-m = 120 × 103 N-mm ;
P = 10 kN = 10 × 103 N ;
M = 80 N-m = 80 × 103 N-mm
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
12. Q2. A shaft, as shown in Figure is subjected to a bending load of 3 kN,
pure torque of 1000 N-m and an axial pulling force of 15 kN. Calculate
the stresses at A and B
Given :
W = 3 kN = 3000 N ;
T = 1000 N-m = 1 × 106 N-mm ;
P = 15 kN = 15 × 103 N ;
d = 50 mm;
length x= 250 mm
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
13. This bending stress is tensile at point A and
compressive at point B.
∴ Resultant tensile stress at point A
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
19. Q3.An overhang crank with pin and shaft is shown in Fig. 5.18. A tangential
load of 15 kN acts on the crank pin. Determine the maximum principal stress
and the maximum shear stress at the centre of the crankshaft bearing.
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
21. Given :
W = 15 kN = 15 × 103 N ; d = 80 mm ;
y = 140 mm ; x = 120 mm
Bending moment at the centre of the crankshaft bearing,
M = W * x =
Torque transmitted at the axis of the shaft,
T = W × y =
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
22. Shear stress due to the torque transmitted,
09-Aug-20
K.BALAMANIKANDASUTHAN A.P/MECH
VELAMMAL I TECH
