AWS AWS Distortion Control & Residual Stress 2

Question 1

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

Accepted Answer

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

Answer

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.

Question 2

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

Accepted Answer

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

Answer

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

Question 3

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

Accepted Answer

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

Answer

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

Question 4

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

Accepted Answer

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

Answer

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.

Question 5

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

Accepted Answer

Mechanical restraint (fixturing)

Answer

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

AWS Practice Test

AWS Practice Test

AWS AWS Distortion Control & Residual Stress 2