machine design & industrial drafting

1. Teli Prakash(150990119050)
Thakur Shivam(150990119051)
Tripathi Himanshu(150990119052)
Vansia Mitrajsinh(150990119054)
Vasava Bhavik(150990119055)

2.  1) INTRODUCTION
 2) ADVANTAGES & DISADVANTAGES OF
WELDED CONNECTIONS
 3) TYPES OF WELDING PROCESSES
 4) TYPES OF WELDED JOINTS
 5) STRESSES & STRESS CONCENTRATION
FACTORS OF WELDED JOINTS
 6) ANALYSIS OF UNSYMMETRICAL WELDED
SECTIONS WHICH ARE AXIALLY LOADED
 7) SPECIAL CASES OF FILLET JOINTS

3.  The process of permanently joining two or
more metal parts by the fusion of edges of
the metals with or without applying pressure
and a filler material is called welding
 If pressure is applied  Forge welding
 Without pressure, with a separate weld
metal Fusion welding
 In a fusion welding, heat of melting is
obtained by two ways:- a) Gas heating b)
Electric arc

4.  Advantages:-
 1. Comparatively lighter than riveted
structures
 2) Greater strength compared to riveted
joints
 3) Addition and alterations can be done
easily
 4) Better finish than riveted joints. Hence
maintenance costs and painting costs are less
 5) Lesser time consuming
 6) Tension members are not weakened in
welded joints compared to riveted joints

5.  Disadvantages:-
 1) Requires skilled labour
 2) Possibility of additional stress
development due to uneven heating and
cooling. Or in other words, the members may
get distorted
 3) Testing is difficult.
 4) As there is no provision for expansion or
contraction of joints, cracks may develop
and propogate

6.  The two important types of welded joints
are:-
 1. Butt weld
 2. Lap (Fillet joint)
3.1) Butt weld joint:-
If the edges of the two plates are touching
each other and are joined by welding, then
the joint is called butt weld joint

7.  Let l= length of weld
t= Depth of weld
F=Tensile force
σt= Allowable tensile stress
 The tensile force, F= σt x A= σt x l x t

8.  Types of butt welds are
 A) Single V butt joint
 B) Double V butt joint
 C) Single U butt joint
 D) Double U butt joint

9.  3.2) Fillet weld or lap joint
 When the two members are overlapped and
joined by welding, then the joint is called
fillet weld joint

10.  Let l= length of weld
t= Throat thickness
s= Size of weld
F=Tensile force
σt= Allowable tensile stress for weld metal

11.  Throat thickness= AB sin45=s x 0.707
 Throat area (minimum area of weld)= Length
of weld x throat thickness= l x s x 0.707
 Tensile strength of the joint/ maximum
tensile force which the fillet joint can take
P=Allowable tensile stress of the weld x
throat area= σt x0.707 x l x s
 Tensile strength of the joint for double fillet
weld= 2 x σt x0.707 x l x s= 1.414 x σt xl x s

12.  3.3) Strength of parallel fillet joint
 Parallel fillet welds are designed for shear
strength
 Consider a double parallel fillet joint as
shown below

13.  If τ is the allowable shear stress of the weld
metal, then the weld strength (shear
strength) of the joint is F= Allowable shear
stress x throat area= 2 x 0.707 x s x l x τ
 Consider a combination of transverse fillet
weld and parallel fillet weld

14.  If τ is the allowable shear stress of the weld
metal and σt is the allowable tensile stress
of the weld metal, then the weld strength
(shear strength) of the joint is F = σt x l1 x
0.707 x s + τ x l2 x 1.414 x s
 For re-inforced welded joints, the throat
dimensions may be taken as 0.85 times the
plate thickness

16.  Consider an unsymmetrical section (angle)
welded on flange edges subjected to an axial
loading
 Let la = length of the weld at the top
 lb = length of weld at the bottom
 L= total length of weld= la+lb

17.  P= Axial load
 a= Distance of the top weld from an axis
passing through the CG of the angle (known
as the gravity axis)
 b= Distance of the bottom weld from gravity
axis.
 f= Resistance offered by the weld per unit
length.
 Resistance offered by top weld= f x la

18.  Moment of the resistance offered by top
weld about the gravity axis= f x la x a
 Similarly the moment of resistance offered
by the bottom weld about the gravity axis= f
x lb x b
 For equilibrium, sum of these moments
should be zero.
 Hence f x la x a= f x lb x b
 => la x a= lb x b; l= la + lb
 Hence la= l x b / (a+ b) and lb = l x a/(a + b)

19.  6.1) Circular fillet weld subjected to
torque/ torsion
 Consider a circular rod connected to a rogid
plate by a fillet joint as shown below.

20.  Let
d= Diameter of the rod
r= Radius of the rod
T= Torque applied
s=Size of weld/ weld leg size
t= Throat thickness
 J= Polar moment of inertia of the weld
section= ∏d³t/4

21.  According to torsion equation, Maximum
shear stress generated due to torsion τ=T.r/J
 τ= T x 2/∏d²t.
 Throat thickness, t=s x 0.707
 Hence τ= 2T/(∏d² x s x0.707)
 => τ= 2.83T/∏d²s
 6.2) Circular fillet weld subjected to
bending moment
 Consider a circular rod connected to a rigid
plate by a fillet weld as shown below

22.  Let M be the bending moment to which the
weld/rod is subjected to and Z be the section
modulus.
 Z= ∏d²t/4
 Bending stress σb= M/Z= (4 x M)/ ∏d²t
 t=s x 0.707
 Hence b=5.66M/ ∏d²s