AWS AWS Distortion Control & Residual Stress 5

Question 1

Which post-weld treatment is most effective at redistributing and reducing residual stresses in carbon steel weldments?

Accepted Answer

Post-weld heat treatment (PWHT) / stress relief annealing

Answer

PWHT at appropriate temperatures (typically 1100–1200°F for carbon steel) allows plastic flow and creep to redistribute and reduce residual stresses.

Question 2

A fabricator is welding two plates butt-welded together and wants to minimize transverse shrinkage. Which approach is most effective?

Accepted Answer

Minimize the weld cross-sectional area by using joint designs with the least required fill

Answer

Minimizing the volume of weld metal deposited directly reduces transverse shrinkage because less material contracts upon cooling.

Question 3

What is the effect of peening on residual stresses in a weld?

Accepted Answer

Introduces compressive residual stresses at the surface, offsetting tensile residual stresses

Answer

Peening stretches the weld surface plastically, introducing compressive stresses that counteract the tensile residual stresses left by solidification shrinkage.

Question 4

When welding a closed-section box structure, why is distortion particularly difficult to control compared to open sections?

Accepted Answer

Rigid restraint of all four sides increases residual stress without allowing stress relief through distortion

Answer

In closed box sections, all sides restrain each other, preventing visible distortion but causing very high residual stresses that can lead to cracking.

Question 5

Which distortion type is characterized by a rotation of the joint members about the weld axis, causing the plates to form a V-shape when viewed from the end?

Accepted Answer

Angular distortion

Answer

Angular distortion produces a V-shape across the weld cross-section because the top of the weld shrinks more than the root due to the larger weld cross-section area at the top.

AWS Practice Test

AWS Practice Test

AWS AWS Distortion Control & Residual Stress 5