Tensile Butt Joint
Simple butt joint loaded in tension or compression
Stress is normal stress
Throat h does not include extra reinforcement
Reinforcement adds some strength for static loaded joints
Reinforcement adds stress concentration and should be ground
off for fatigue loaded joints
Fig. 9–7a Shigley’s Mechanical Engineering Design
Shear Butt Joint
Simplebutt joint loaded in shear
Average shear stress
Fig. 9–7b
Shigley’s Mechanical Engineering Design
Transverse Fillet Weld
Joint
loaded in tension
Weld loading is complex
Fig. 9–8
Fig. 9–9
Shigley’s Mechanical Engineering Design
Transverse Fillet Weld
Summation of forces
Law of sines
Solving for throat thickness t
Fig. 9–9
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Transverse Fillet Weld
Nominal stresses at angle
Von Mises Stress at angle
Fig. 9–9
Shigley’s Mechanical Engineering Design
Transverse Fillet Weld
Largest von Mises stress occurs at = 62.5º with value of
' = 2.16F/(hl)
Maximum shear stress occurs at = 67.5º with value of
max = 1.207F/(hl)
Fig. 9–9
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Experimental Stresses in Transverse Fillet Weld
Experimental results are more complex
Fig. 9–10
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Transverse Fillet Weld Simplified Model
No analytical approach accurately predicts the experimentally
measured stresses.
Standard practice is to use a simple and conservative model
Assume the external load is carried entirely by shear forces on
the minimum throat area.
By ignoring normal stress on throat, the shearing stresses are
inflated sufficiently to render the model conservative.
By comparison with previous maximum shear stress model, this
inflates estimated shear stress by factor of 1.414/1.207 = 1.17.
Shigley’s Mechanical Engineering Design
Parallel Fillet Welds
Same equation also applies for simpler case of simple shear
loading in fillet weld
Fig. 9–11
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Fillet Welds Loaded in Torsion
Filletwelds carrying both
direct shear V and moment M
Primary shear
Secondary shear
A is the throat area of all
welds
r is distance from centroid of
weld group to point of
interest Fig. 9–12
J is second polar moment of
area of weld group about
centroid of group Shigley’s Mechanical Engineering Design
Example of Finding A and J
Rectangles represent
throat areas. t = 0.707 h
Fig. 9–13
Shigley’s Mechanical Engineering Design
Example of Finding A and J
Note that t3 terms will be
very small compared to
b3 and d3
Usually neglected
Leaves JG1 and JG2 linear
in weld width
Can normalize by
treating each weld as a
line with unit thickness t
Results in unit second
polar moment of area, Ju
Since t = 0.707h,
Fig. 9–13
J = 0.707hJu
Shigley’s Mechanical Engineering Design
Common Torsional Properties of Fillet Welds (Table 9–1)
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Common Torsional Properties of Fillet Welds (Table 9–1)
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Example 9–1
Fig. 9–14
Shigley’s Mechanical Engineering Design
Example 9–1
Fig. 9–15
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Example 9–1
Fig. 9–15
Shigley’s Mechanical Engineering Design
Example 9–1
Fig. 9–15
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Example 9–1
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Example 9–1
Fig. 9–16
Shigley’s Mechanical Engineering Design
Example 9–1
Fig. 9–16 Shigley’s Mechanical Engineering Design
Fillet Welds Loaded in Bending
Fig. 9–17
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Bending Properties of Fillet Welds (Table 9–2)
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Bending Properties of Fillet Welds (Table 9–2)
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Strength of Welded Joints
Must check for failure in parent material and in weld
Weld strength is dependent on choice of electrode material
Weld material is often stronger than parent material
Parent material experiences heat treatment near weld
Cold drawn parent material may become more like hot rolled in
vicinity of weld
Often welded joints are designed by following codes rather than
designing by the conventional factor of safety method
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Minimum Weld-Metal Properties (Table 9–3)
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Stresses Permitted by the AISC Code for Weld Metal
Table 9–4
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Fatigue Stress-Concentration Factors
Kfs appropriate for application to shear stresses
Use for parent metal and for weld metal
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Allowable Load or Various Sizes of Fillet Welds (Table 9–6)
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Minimum Fillet Weld Size, h (Table 9–6)
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Example 9–2
Fig. 9–18
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Example 9–2
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Example 9–2
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Example 9–3
Fig. 9–19
Shigley’s Mechanical Engineering Design
Example 9–3
Shigley’s Mechanical Engineering Design
Example 9–3
Shigley’s Mechanical Engineering Design
Example 9–3
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Example 9–3
Shigley’s Mechanical Engineering Design
Example 9–3
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Example 9–4
Fig. 9–20
Shigley’s Mechanical Engineering Design
Example 9–4
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Example 9–4
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Example 9–4
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Example 9–5
Fig. 9–21
Shigley’s Mechanical Engineering Design
Example 9–5
Shigley’s Mechanical Engineering Design
Example 9–5
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Example 9–6
Fig. 9–22
Shigley’s Mechanical Engineering Design
Example 9–6
Shigley’s Mechanical Engineering Design
Example 9–6
Shigley’s Mechanical Engineering Design
