1. Chapter 9 Welding, Bonding, and the Design of Permanent Joints
Dr. A. Aziz Bazoune
King Fahd University of Petroleum & Minerals
Mechanical Engineering Department
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

2. Chapter Outline 9-1 Welding Symbols 9-2 Butt and Fillet Welds
9-3 Stresses in Welded Joints in Torsion
9-4 Stresses in Welded Joints in Bending
9-5 The Strength of Welded Joints
9-6 Static Loading
9-7 Fatigue Loading
9-8 Resistance Welding
9-9 Bolted and Riveted Joints Loaded in Shear
9-10 Adhesive Bonding
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

3. LECTURE-40 9-1 Welding Symbols 9-2 Butt and Fillet Welds
9-3 Stresses in Welded Joints in Torsion
9-4 Stresses in Welded Joints in Bending
9-5 The Strength of Welded Joints
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

4. Introduction
Welding is the process of joining two pieces of metal together by hammering, pressure or fusion. Filler metal may or may not be used.
The strongest and most common method of permanently joining steel components together.
Arc welding is the most important since it is adaptable to various manufacturing environments and is relatively cheap.
A weldment is fabricated by welding together a collection of metal shapes.
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

5. Introduction
A pool of molten metal in which the components and electrode material coalesce, forming a homogeneous whole (ideally) when the pool later resolidifies.
The materials of components and electrode must be compatible from the point of view of strength, ductility and metallurgy.
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

6. Two most common forms are: the butt joint the fillet joint
The form of a welded joint is dictated largely by the layout of the joined components.
Two most common forms are:
the butt joint
the fillet joint
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

7. 9-1 Welding Symbols
A weld is fabricated by welding together a collection of metal shapes, cut to particular configurations.
The weld must be precisely specified on working drawing and this is done by welding symbol, Fig. 9-1.
The arrow of this symbol points to the joint to be welded.
The body of the symbol contains as many of the following elements as are deemed necessary:
Reference line
Arrow
Basic weld symbols in Fig. 9-2
Dimensions and other data
Supplementary symbols
Finish symbols
Tail
Specification or process.
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

8. Welding Symbols
WELD
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

9. Types of Welding Fillet There 2 general types of welds:
Fillet welds for general machine elements.
Butt or groove welds for pressure vessels, piping systems,...
There are also others such as: ,
Fillet welds
groove welds
Bead
Plug or slot
Plug or slot
groove
Bead
Fillet
Figure 9-2
Arc and gas-weld symbols
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

10. Residual stresses may be introduced because of clamping or holding.
Parts to be joined must be arranged so that there is sufficient clearance for welding operation.
Due to heat, there are metallurgical changes in the parent metal in the vicinity of the weld.
Residual stresses may be introduced because of clamping or holding.
These residual stresses are not severe enough to cause concern.
A light heat treatment after welding is done to relive these stresses.
When the parts to be welded are thick, a preheating will also be of benefit.
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

11. Figure 9-3
Fillet welds
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

12. Figure 9-4
The circle on the weld symbol indicates that the welding is to go all around.
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

13. Figure 9-5
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

14. Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

15. Figure 9-6
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

16. Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

17. 9-2 Butt and Fillet Welds
where h is the weld throat and l is the length of the weld. Notice that the value of h does not include the reinforcement.
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

18. The reinforcement can be desirable, but it varies somewhat and does produce stress concentration at point A in the figure. If fatigue loads exist, it is good practice to grind or machine off the reinforcement.
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

19. Stresses in Fillet Welds
Fig. 9-8 illustrates a typical transverse fillet weld.
In Fig. 9-9 a portion of the welded joint has been isolated from Fig. 9-8
At angle q the forces on each weldment consists of a normal force Fn and a shear force Fs
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

20. Stresses in Fillet Welds
The nominal stresses at the angle θ in the weldment, τ and σ, are
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

21. The von Mises stresse σ’at angle θ is
σ’max occurs at θ = 62.5o with a value of σ’max = 2.16 F/(hl).
The corresponding values of τ and σ, are τ = F/(hl) and σ = F/(hl).
τmax can be found by solving the equation [d(τ)/dθ]=0.
The stationary point occurs at θ = 67.5o with a corresponding τmax = F/(hl) and σ = 0.5 F/(hl).
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

22. Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

23. We have no analytical approach that predicts the existing stresses.
The geometry of the fillet is crude by machinery standards.
The approach has been to use a simple and conservative model, verified by testing as conservative.
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

24. The approach has been to:
Consider the external loading to be carried by shear forces on the throat area of the weld. By ignoring the normal stress on the throat, the shearing stresses are inflated sufficiently to render the model conservative.
Use the distortion energy for significant stresses
Circumscribe typical cases by code
For this model, the basis for weld analysis or design employs
which assumes the entire force F is accounted for by a shear stress in the minimum throat area.
(9.3)
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

25. Notice that this inflates the maximum estimated shear stress by a factor of 1.414/1.207=1.17.
Further, consider the parallel fillet welds shown in Fig where, as in Fig.9-8, each weld transmits a force F. However, in the case of Fig. 9-11, the maximum shear stress is at the minimum throat area and corresponds to Eq. (9-3).
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

26. Under circumstances of combined loading we:
Examine primary shear stresses due to external forces.
Examine secondary shear stresses due to torsional and bending moments.
Estimate the strength(s) of the parent metal (s).
Estimate the strength of the deposited weld metal.
Estimate the permissible load(s) for parent metal(s).
Estimate permissible load for deposited weld metal.
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

27. 9-3 Stresses in Welded Joints in Torsion
Figure 9-12 illustrates a cantilever of length l welded to a column by 2 fillet welds.
The reaction at the support of a cantilever always consists of shear force V and a moment reaction M.
The shear force produces a primary shear in the welds of magnitude
where A is the throat area of the welds.
(9.4)
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

28. The moment at the support produces secondary shear or torsion of the welds, and this stress is given by
where
r: distance from the centroid of the weld group to the point in the weld of interest.
J: second polar moment of area of the group about the centroid of the group.
(9.5)
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

29. Weld 1 has a throat width b1 = 0.707 h1
Figure 9-13 shows 2 welds in a group. The rectangles represent the throat areas of the welds.
Weld 1 has a throat width b1 = h1
Weld 2 has a throat width d2 = h2
Throat area of both welds together is
A = A1 + A2 = b1d1 + b2d2
which is the area to be used in Eq. (9-4)
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

30. The x-axis passes through the centroid G1 of the weld 1.
The second moment of area about this axis is
Similarly, the second moment of area about an axis passing through G1 parallel to the y-axis is
The second polar moment of areas of weld 1 and weld 2 about their centroids are
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

31. The centroid G of the weld group is located at
The distances r1 and r2 from G1 and G2 are respectively given by
Using the parallel axis theorem, the second polar moment of area of the weld group is
This is the quantity to be used in Eq. (9-5). The distance r must be measured from G and the moment M computed about G.
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

32. Ju : is found from table 9.1 Page 472
The quantities and , which represent the weld width are small and hence can be neglected.
The terms and Makes JG1 and JG2 linear in the weld width.
Setting weld widths b1 and d2 to unity leads to the idea of treating each fillet weld as line.
The resulting second moment of area is then a unit second polar moment of area.
The value of Ju same regardless of weld size.
Since throat width of a fillet weld is 0.707h, the relation between J and the unit value is
(9.6)
Ju : is found from table 9.1 Page 472
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

33. Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints

34. QUESTIONS ?
Thank U !
Dr. A. Aziz Bazoune Chapter9: Welding, Bonding, and the Design of Permanent Joints