CWI Joint Design and Weld Joint Types 2 — Questions and Answers
Question 1: The theoretical throat of a fillet weld is defined as the distance from the joint root to the:
- Face of the weld
- Nearest toe of the weld
- Hypotenuse of the largest right triangle inscribed in the weld cross section (Correct answer)
- Midpoint of the weld leg
Correct answer: Hypotenuse of the largest right triangle inscribed in the weld cross section
The theoretical throat is the perpendicular distance from the root to the hypotenuse of the largest right triangle that can be inscribed within the fillet weld cross section.
Question 2: For an equal-leg fillet weld with legs at 45°, the theoretical throat is approximately what fraction of the leg size?
- 0.500 × leg size
- 0.600 × leg size
- 0.707 × leg size (Correct answer)
- 0.866 × leg size
Correct answer: 0.707 × leg size
For a 45° equal-leg fillet weld, the theoretical throat equals leg size × sin(45°) = leg size × 0.707, which is approximately 70.7% of the leg dimension.
Question 3: Per AWS D1.1, what is the minimum fillet weld size required when the thicker base metal being joined exceeds 3/4 inch (19 mm)?
- 1/4 inch (6 mm)
- 5/16 inch (8 mm) (Correct answer)
- 3/8 inch (10 mm)
- 1/2 inch (12 mm)
Correct answer: 5/16 inch (8 mm)
AWS D1.1 Table 5.8 specifies a minimum fillet weld size of 5/16 inch when the thicker base metal member exceeds 3/4 inch to ensure adequate fusion and heat input.
Question 4: A plug weld is made by:
- Preparing a groove along the edge of a base metal member
- Depositing weld metal in a hole in the overlapping member to fuse it to the underlying member (Correct answer)
- Welding along a slot cut through the length of one member
- Joining two members end to end in the same plane
Correct answer: Depositing weld metal in a hole in the overlapping member to fuse it to the underlying member
A plug weld is made in a circular hole punched or drilled in one member; weld metal fills the hole and fuses to the surface of the underlying member, joining the two overlapping pieces.
Question 5: The root face (land) in a groove weld joint is included primarily to:
- Increase the effective groove angle
- Prevent burn-through and provide a surface for the root pass to fuse against (Correct answer)
- Reduce the need for filler metal at the root
- Increase weld penetration depth
Correct answer: Prevent burn-through and provide a surface for the root pass to fuse against
The root face provides a small flat area at the base of the groove that helps control heat and prevents the arc from burning through while still allowing complete root fusion.
Question 6: Which weld joint type is generally preferred for members subject to fatigue loading because it minimizes stress concentrations?
- Lap joint with fillet welds
- Butt joint with complete joint penetration (Correct answer)
- Tee joint with fillet welds on both sides
- Corner joint with partial penetration groove welds
Correct answer: Butt joint with complete joint penetration
A CJP butt joint provides a smooth load path through the weld with no abrupt changes in cross section, minimizing the stress concentrations that initiate fatigue cracking.
Question 7: A slot weld differs from a plug weld in that:
- A slot weld is made from the back side of the joint
- A slot weld is made in an elongated hole rather than a circular hole (Correct answer)
- A slot weld requires a groove preparation unlike a plug weld
- A slot weld is always a groove weld, not a fillet weld
Correct answer: A slot weld is made in an elongated hole rather than a circular hole
A slot weld is made in an elongated (rectangular or oval) opening in the overlapping member, whereas a plug weld is made in a circular hole; both fuse the two overlapping members together.
CWI Joint Design and Weld Joint Types 2
The theoretical throat of a fillet weld is defined as the distance from the joint root to the: