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Design by First Principle
E = Mc2
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First Principle Design is a collective term for Theories, Principles
& Methods Studied in Engineering Subjects like Strength ofMaterials, Machine Design.
At the heart of Mechanical Engineering Design
Importance / Relevance of Subject
Basic requirements for any mechanical design
Engineering Sciences Mathematics
Material Sciences
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Stress terms Tensile Stress
Compressive Stress
Shear Stress
Temperature Stress
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Strength terms
Yield Strength
Tensile Strength
Compressive Strength
Fatigue Strength ( Endurance Limit)
Impact Strength
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Strain Terms
Deformation
Strain Normal Strain
Shear Strain
Deflection
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Stress-Strain Relations
Modulus of Elasticity
Modulus of Rigidity
Plasticity
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Other Terms
Poisson's Ratio
Toughness
Fatigue
Factor of Safety
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Simple Bending Theory
Simple Torsion Theory
Thin Cylinder under Internal Pressure
Principal Stress & Mohrs Circle
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Theories of Failure
Maximum Principal Stress ( Rankine)
Maximum Shear Stress ( Tresca)
Maximum Principal Strain ( Saint-Venant)
Total Strain Energy / Volume
Distortion Energy ( Von Mises)
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First Principal Vs FEA
Simplification Vs Discrete
Maximum / local Vs Global / All-over
Experimentation Vs Validation
Easily understood Vs Experts choice
Accuracy ??
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Why FEA ??
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Reserve Propulsion Shaft line
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Tapper Fitment for Propeller
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D3
do
diD2
L
Back face constrained in
axial (Z-) direction
Taper face constrained in
tangential (Y-) direction
Radial(X-) interference
(=0.0418mm) applied on
taper face
Tapper Fitment for Half Coupling
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Data for half coupling tapper fitmentTorque transmitted, TD = 7000 N-m
Safety factor on slippage = 2.8
Tapper Length, L = 150 mm
Tapper angle, =0.0334
Rad
Large diameter of tapper (do) = 109 mm
Small diameter of tapper (di) = 99 mm
Hub Diameter (D3) = 160 mm
D3
do
diD2
L
Material BS : 817M40
Yield Strength, y = 650 Mpa
Youngs modulus, E = 2.07 x105 Mpa
Poissons Ratio = 0.3
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1.4903622
2
2
2 =+
= L
ddDA
io
16.0=
Surface area of taper, mm2
Assuming a coefficient of friction,
Mean diameter of taper, mm 1042
0
2=
+=
idd
D
Tangential force on taper area, KN 92.376
22
==D
TF
D
T
Normal force on the taper area, N
Pressure on the taper area, Mpa
For shaft and disc of same material, the diametrical interference required for achieving the
above determined pressure is given by, mm
Radial interference required, mm
610356.2 ==
T
N
FF
04.48
== AF
PN
( ) 0836.012
2
2
3
2
2
2
32
int=
+
+
+= DD
DD
E
PD
0418.0int =R
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intR
a
radial interference and the axial movement of taper during fit.
Axial shift of half coupling during fit, mm
25.1sin
int ==
Ra
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Thank You
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26264686728 N
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P =4686728 N
L=350
M = P x L
Tensile Stress
Compressive Stress
N.A
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2986531
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2986531 N
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P =2986531 N
L=350
M = P x L
Tensile Stress
Compressive Stress
N.A
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i i i l i
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i i i l i
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Fi P i i l D i
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