Machine Design- I

1. Welded joint
• Welding can be defined as a process of joining metalic
parts by heating to a suitable temperature with or
without the application of pressure.
• Welding is an economical and efficient method for
obtaining a permanent joint of metalic parts.
• Types of welded joints:
a) Butt joint
b) fillet joint
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2. 1. Butt joint
• A Butt joint can be defined as a joint between two components
lying approximately in the same plane. It connects the ends of the
two plates.
• The but joints may be:-
a. Square butt joint (thickness of the plates < 5 mm)
b. Single V- butt joint ( 5 < t < 25 mm )
c. Single U- butt joint ( t > 20 mm)
d. Double V- butt joint ( t > 30 mm)
e. Double U- butt joint ( t > 30 mm)
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3. 2. fillet joint
• A filet joint also called as lap joint is a joint between two
overlapping plates or components.
• The fillet joints are of two types
(a) transverse fillet- if the direction of the weld is
perpendicular to the direction of force
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(b)Parallel fillet- if the direction of the weld is
parallel to the direction of force

5. 1. Strength of Butt Joint
The average tensile stress in the weld is
given by
In this case Throat of the weld (h) = Thickness of plate (t)
Hence Strength of the butt joint
P= σt t l
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6. 2 (a) Strength of parallel fillet welded joints:
Consider a double parallel fillet welded joint:-
Let
h = Leg of the weld (size of the weld)
t = Throat of the weld ( Minimum
cross section of the weld located at
450 to the leg dimension.
t = h Cos 450 = 0.707 h
• Failure of the fillet weld occurs due to shear along the minimum cross
section at the throat.
• Shear stress in the fillet weld
• Strength of the single parallel fillet weld
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7. 2 (b) Strength of transverse fillet welded joints:
• Failure due to tensile stress occurs at the throat section.
Tensile stress in the transverse fillet
weld
Strength of weld
For double transverse
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8. 2 (C) Combination of transverse and parallel fillet
Strength of the welded joint = strength of transverse fillet +
strength of parallel fillet
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9. Problem.1 Two steel plates, 120 mm wide and 12.5 mm
thick are joint together by means of double transverse
fillet welds, as shown in fig. The maximum tensile stress
for the plates and the welding material should not
exceed 110 N/mm2. Find the required length of the weld
if the strength of weld is equal to the strength of the
plates.
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Axially Loaded welded Joint-

10. Problem.2 A steel plate, 100 mm wide and 10 mm thick is
joined with another steel plate by means of a single
transverse and double parallel fillet welds as shown in fig.
The strength of the welded joint should be equal to the
strength of the plates to be joined. The permissible tensile
and shear stress for the weld material and the plates are
70 and 50 N/mm2, respectively. Find the length of each
parallel fillet welds. Assume the tensile force acting on the
plates as static.
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Problem 3. A welded connection of steel plates as shown in
fig. is subjected to an eccentric force of 10 kN. Determine
the throat dimensions of the weld if the permissible shear
stress is limited to 95 N/mm2. Assume static conditions. All
dimensions are in mm.
Nov-Dec 2012,Nov Dec 2013
Eccentrically Loaded welded Joint-

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Problem 4. A rectangular steel plate is welded as a
cantilever to a vertical column and supports a single
concentrated load P as shown in fig. Determine the size
of the weld if shear stress in the same is not to exceed
140 MPa.
April May 2010

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Problem 5. A weld connection is subjected to eccentric
force of 60 kN in the plane of weld. Determine the size of
the weld if the permissible shear stress in the weld is
limited to 100 N/mm2.
April May 2013

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Problem 6. Determine the size of the weld required for
static loading in the eccentrically loaded weld as shown in
fig. the effective length of the weld is 12.5 mm shorter
than the weld to allow for starting and stopping of the
weld.
April May 2012

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Problem 7. A beam of rectangular cross section is
welded to a support by means of fillet welds as shown in
Fig,. Determine the size of welds, if the permissible shear
stress in the weld is limited to 75 N/mm2.
Welded Joint subjected to bending Moment-

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Problem 8. A circular shaft 50 mm in diameter is welded
to a support by means of a fillet weld as shown in fig.
determine the size of the weld if the permissible shear
stress in the weld is limited to 100 N/mm2.
April May & Nov-Dec 2011

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Problem 9. Find the maximum shear stress induced in
the weld of 6mm size when a channel as shown in fig is
welded to a plate and loaded with 20 kN force
Nov-Dec 2010