Final answer:
A T-fillet weld is most affected by angular distortion, which changes the angles within the welded parts due to differential expansion and contraction from the heat of welding.
Step-by-step explanation:
A T-fillet weld is affected most by angular distortion. Angular distortion occurs when there is a change in the angles within the initial shape of the parts being welded; for instance, warping in the plane of the parts forming the T joint. This is a common concern when welding, as the heat introduced into the material can expand and contract different areas at different rates causing the material to bend or twist.