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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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First Principle Design

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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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1717

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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1818

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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First Principle Design

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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Fi P i i l D i

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Fi t P i i l D i

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Fi t P i i l D i

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Fi t P i i l D i

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Fi t P i i l D i

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