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Table of Figures
Figure 1 : Unprotected type flange coupling.........................................................8
Figure 2: Protected type flange coupling .............................................................8
Figure 3: Marine type flange coupling.................................................................9
A coupling is a device used to connect two shafts together at their ends for the purpose
of transmitting power. Flange coupling are designed for heavy loads or industrial equipment.
When joining shafts within a machine, mechanics can choose between flexible and rigid
couplings. The coupling enables torque transmission between the shafts & prevents relative
rotation between them. The connecting methods for flange couplings are usually very strong
because of either the pressure of the Material or the sometimes hazardous nature of Materials
passed through many industrial piping Systems. This project deals with stress analysis of rigid
flange couplings subjected to Static loads using Pro engineer. The outcome analysis is there’s no
danger of failure by pure shear; even if a fatigue reduction factor is included. The design of
flange coupling will be done in Pro Engineer software. To obtain computer solution Pro E is
In all areas of industry, the demand for machinery and equipment of greater
performance has ever increased. Couplings, serving as vital transmission parts, are no exception
to meet higher and more stringent quality requirements. The objective of flange shaft coupling is
as given below:
To solve a problem
To design that problem
To calculate the factor of safety
To know about coupling function
To know about its application
1.3 Problem Statement:
It cannot be de-engaged in motion.
Flanged coupling cannot transmit power between two nonlinear shafts.
If the shafts cannot be maintained in good alignment and if the loading induces relatively
high stresses fatigue failure occurs.
If the flanges are nearer to the bearing the smaller will be the deflection of shaft at the
point and the smaller the stresses included in the flanges by this deflection.
2 LITERATURE REVIEW OF FLANGE COUPLING:
Italian mathematician Girolamo Cardano in 1945 used the bases of gimbals to
convey rotational motion through an angled connection, which was advanced into the Cardan
Shaft, which can be used for a smooth ride. Shaft is always at a 90 degree angle to the axle. This
new idea was truly first seen in 1548.
In 1676, Robert Hooke evaluates the previous idea and used it to make an instrument that would
allow for a safer way to study the sun. This new instrument used a new kind of joint that allowed
for twisted motion in one shaft to be passed on to another. After 240 years, that idea was used in
automotive vehicle and industries. Spicer received a patent for the worldwide joint in 1903 and
showed his new patent in a self-designed car, which did not have chain & sprocket nor have
chain and geared. (1)
Human invented and find energy. Soon they learnt to transfer it using shaft. But in many
situations we were unable to transfer power by shafts because in shafts there can be many
problems due to misalignment, length of the shaft & its twisting property. So human work hard
& developed the new way of transmitting power by shafts in all possible situations. The
mechanical joint they invented was named coupling.
These days, human made many achievements in shaft coupling design. For example ETP-
HYCON is available for shaft 80-200 mm. It can be mounted when only one pump is to be used.
As the coupling is completely sealed, no oil drainage occurs, resulting in a more user- and
environment friendly handling. The hydro-mechanical couplings ETP-HYCON type consists of
an outer sleeve with hydraulic connections, an inner sleeve with ETP-HFC on the inside and an
on the inner sleeve assembled cylindrical nut and seals.
In present days 1st of all to coupling is designed and then manufactured. So efficiency and safety
of design is more than the previous one. Selecting a shaft coupling many performance factor are
under consideration. For example shaft misalignment, rpm, stiffness and space for fixing shaft
coupling. All these factors are most important for proper working of shaft coupling.
A single type of couplings, however, cannot be applied to every application in the field. So we
design many types of couplings for different reason. The only way to increase coupling life is to
understand that why failure of shaft coupling occurs. (2)
3.5 ASSEMBLY OF FLANGE COUPLING:
4 Theoretical Analysis:
Design of machine components from first principles requires to be able to discriminate between
critical and non-critical stress (or strains).
Critical stresses (or strains) are those that essentially determine the required dimensions
of a feature or component. These stresses or strains need to be calculated. For example, in
coupling design, the key and keyway involve critical stress and the dimensions of the keyway are
based on the allowable stress in the key and keyway.
Non-critical stresses (or strains) are those that have a low value and do not influence
dimensions. The dimensions in this case are determined by appearance or some other functional
requirement other than stress or strain. For example, in a coupling, the width of the outer flange
is a non-critical dimension and is usually determined by appearance/safety considerations (giving
adequate protection from the protruding bolts and nuts).
Where critical stresses are involved, the analysis can be done by calculation using
formulas. This is the approach adopted here. It is important to realize that this approach involves
some "esstimation" because certain assumptions and approximations are usually necessary. This
is where experience and skill of a mechanical design engineer is required, to know what
assumptions to make and to have a feel for the types of stresses involved and to be able to
discriminate between those that are critical and those that are not. Another method of stress and
strain analysis is using Finite Element Method (FEM) using a computer. This is a more accurate
method but involves study in its own right.
4.1 Types of Flanged Coupling:
4.1.1 Unprotected type flange coupling
Figure 1 : Unprotected type flange coupling
The usual proportions for an unprotected type cast iron flange couplings, as shown in
Fig. 13.12, are as follows :
If d is the diameter of the shaft or inner diameter of the hub, then
Outside diameter of hub, = 4, for d upto 100 mm
= 6, for d upto 180 mm
4.1.2 Protected type flange coupling
sFigure 2: Protected type flange coupling
4.1.3 Marine type flange coupling:
Figure 3: Marine type flange coupling
4.2 DESIGN OF FLANGE COUPLING:
Consider a flange coupling as shown in Fig 13.12 and Fig 13.13.
d = Diameter of shaft or inner diameter of hub,
D = Outer diameter of hub,
d1 = Nominal or outside diameter of bolt,
D1 = Diameter of bolt circle,
n = Number of bolts,
𝑡𝑓= Thickness of flange,
𝜏𝑠 𝜏 𝑏 𝑎𝑛𝑑 𝜏 𝑘 = Allowable shear stress for shaft, bolt and key material respective
𝜏 𝑐 = Allowable shear stress for the flange material i.e. cast iron,
𝜎𝑐𝑘 and σcb= Allowable crushing stress for bolt and key material respectively.
The flange coupling is designed as discussed below :
1. Design for hub:
The hub is designed by considering it as a hollow shaft, transmitting the same
torque (T) as that of a solid shaft.
x 𝜏 𝑐 ( 𝐷4 −𝑑4
2. Design for flange:
The flange at the junction of the hub is under shear while transmitting the
torque. Therefore, the troque transmitted,
T = πD x τc x tf x
x τc x tf
3. Design for bolts:
The bolts are subjected to shear stress due to the torque transmitted. The number of
bolts (n) depends upon the diameter of shaft and the pitch circle diameter of bolts (𝐷1) is taken as
3 d. We know that
Load on each bolt =
( 𝑑1)2 x τb
∴ Total load on all the bolts =
( 𝑑1)2 x τb x n
and torque transmitted, T =
( 𝑑1)2 x τb x n x
From this equation, the diameter of bolt (d1) may be obtained. Now the diameter of bolt may be
checked in crushing. We know that area resisting crushing of all the bolts
= n x 𝑑1 x 𝑡𝑓
and crushing strength of all the bolts = ( n x 𝑑1 x 𝑡𝑓 ) σcb
∴ Torque, = ( n x 𝑑1 x 𝑡𝑓 x σcb)
Design a rigid flange coupling to transmit a torque of 250 N-m between two co-axial shafts. The
shaft is made of alloy steel, flanges out of cast iron and bolts out of steel. Four bolts are used to
couple the flanges. The shafts are keyed to the flange hub. The permissible stresses are given
Shear stress on shaft =100 MPa
Bearing or crushing stress on shaft =250 MPa
Shear stress on keys =100 MPa
Bearing stress on keys =250 MPa
Shearing stress on cast iron =200 MPa
Shear stress on bolts =100 MPa
After designing the various elements, make a neat sketch of the assembly on CAD / CAM
indicating the important dimensions. The stresses developed in the various members may be
checked if thumb rules are used for fixing the dimensions
T = 250 N-m = 250 × 103 N-mm ; n = 4; τS = 100 MPa = 100 N/𝑚𝑚2
;. σcb = 250 MPa = 250
; τk = 100 MPa = 100 N/𝑚𝑚2
; σck = 250 MPa = 250 N/𝑚𝑚2
; τc = 200 MPa = 200
; τb = 100 MPa = 100 N/𝑚𝑚2
1. Design for hub:
First of all, let us find the diameter of the shaft (d). We know that the torque transmitted by the
shaft ( T ),
250 × 103
x τS x 𝑑3
x 100 x 𝑑3
= 250 ×103
/ 19.64 = 12 729 or d = 23.35 say 25 mm Ans.
We know that the outer diameter of the hub,
D =2 d = 2 × 25 = 50 mm
and length of hub , L = 1.5 d = 1.5 × 25 = 37.5 mm
Let us now check the induced shear stress in the hub by considering it as a hollow shaft. We
know that the torque transmitted (T),
250 × 103
x 𝜏 𝑐 ( 𝐷4−𝑑4
x 𝜏 𝑐 (
𝜏 𝑐 = 250 × 103/23 013 = 10.86 N/𝑚𝑚2
= 10.86 MPa
Since the induced shear stress for the hub material (i.e. cast iron) is less than 200 MPa, therefore
the design for hub is safe.
2. Design for key:
We find that the proportions of key for a 25 mm diameter shaft are :
Width of key, w = 10 mm Ans.
and thickness of key, t = 8 mm Ans.
The length of key ( l ) is taken equal to the length of hub,
∴ l = L = 37.5 mm Ans.
Let us now check the induced shear and crushing stresses in the key. Considering the key in
shearing. We know that the torque transmitted ( T ),
250 × 103
= l x w x τk x
= 37.5 x 10 x 𝜏 𝑘 x
𝜏 𝑘 = 53.3 MPa Ans.
Considering the key in crushing. We know that the torque transmitted (T),
250 × 103
= l x
x σck σck = 133.3 MPa Ans.
Since the induced shear and crushing stresses in the key are less than the given stresses, therefore
the design of key is safe.
3. Design for flange:
The thickness of the flange (𝑡𝑓) is taken as 0.5 d.
∴ 𝑡 𝑓 = 0.5 d = 0.5 × 25 = 12.5 mm Ans.
Let us now check the induced shear stress in the flange by considering the flange at the junction
of the hub in shear. We know that the torque transmitted ( T ),
250 × 103
x 𝑡𝑓 x 𝜏 𝑐 =
x 𝜏 𝑐 x 12.5 𝜏 𝑐 = 5.1MPa Ans.
Since the induced shear stress in the flange of cast iron is less than 200 MPa, therefore design of
flange is safe.
4. Design for bolts:
Let 𝑑1= Nominal diameter of bolts.
We know that the pitch circle diameter of bolts,
∴ 𝐷1= =3 d = 3 × 25 = 75 mm Ans.
The bolts are subjected to shear stress due to the torque transmitted. We know that torque
250 × 103
x ( 𝑑1)2
𝜏 𝑏 x n x
𝑑1 = 4.6 mm Ans.
Other proportions of the flange are taken as follows :
Outer diameter of the flange, 𝐷2 =4 d = 4 × 25 = 100 mm Ans.
Thickness of the protective circumferential flange
𝑡 𝑝 = 0.25 d = 0.25 × 25 = 6.25 mm Ans
5 Advantages & Disadvantages:
It is cheap Can’t be de-engaged in motion
Drawbacks of flanged coupling are as following-
Flanged coupling can’t transmit power between two non linear shaft.
7.1 Result & Discussion:
If the shafts can not be maintained in good alignment and if the loading induces relatively high
stresses fatigue failure occurs. If the flanges are nearer to the bearings the smaller will be the
deflection of the shaft at the point and the smaller the stresses included in the flanges by this
deflection. So the design will be safe from failure.
7.2 Concluding remarks:
By performing this project we had learnt the design of a flanged coupling, analysis of a flanged
coupling, calculating safety factor of it & the safe arrangement of it. In future it will be helpful
for us to choose the right coupling among various types of couplings.
1. Seminar Report on Coupling. Scribd. [Online] www.scribd.com/document/179095009/A-
2. Flange Coupling. Slide Share. [Online] www.slideshare.net/MdAnamulHasan/report-on-