AWS Distortion Control & Residual Stress Flashcards

Residual tensile stresses in a weldment are most likely to be found:

Answer: In the weld and HAZ region, parallel to the weld axis

Residual tensile stresses are highest in the weld metal and HAZ near the fusion line, acting parallel to the weld due to constrained thermal contraction.

What is the concern with residual tensile stresses in a structure subjected to fatigue loading?

Answer: They reduce the effective fatigue life by adding to applied tensile stresses

Residual tensile stresses combine with applied cyclic stresses to accelerate fatigue crack initiation and propagation.

How does 'shot peening' or 'hammer peening' of a weld toe improve fatigue life?

Answer: It introduces compressive residual stresses at the weld toe, counteracting applied tensile stresses

Peening plastically deforms the weld toe surface, inducing compressive residual stresses that counteract applied tensile stresses and inhibit crack initiation.

What is 'lamellar tearing' and which base metal condition makes it most likely?

Answer: Subsurface tearing parallel to the plate surface due to low through-thickness ductility and sulfide inclusions

Lamellar tearing occurs beneath welds in the base metal when through-thickness strains fracture planes of low ductility caused by sulfide or silicate inclusions aligned parallel to the plate surface.

Which technique for controlling distortion relies on using strong-backs, clamps, or fixtures to physically restrain the parts during welding?

Answer: Mechanical restraint (fixturing)

Mechanical restraint uses fixtures, clamps, or strong-backs to hold parts in alignment during welding, preventing distortion from occurring.

Transverse shrinkage in a butt weld is approximately proportional to:

Answer: The amount of weld metal deposited (weld cross-sectional area)

Transverse shrinkage increases with the volume of weld metal deposited, because more weld metal means more thermal contraction across the joint.