Welding Defects cause and effect

A: Governing principle: ISO 5817 controls geometric weld imperfections because they drive stress concentration under cyclic load. Applied here, Level C sets a hard cap on undercut depth for fillet welds used structurally; continuity length doesn't buy relief once depth exceeds the limit. Distractor A traps engineers who remember averaging rules from other indications and apply them where the standard doesn't permit it.

A: Governing principle: heat input equals voltage times current times efficiency divided by travel speed. With 24×220×0.8 divided by 6 mm/s, unit handling lands at 0.88 kJ/mm once joules are converted to kilojoules. Distractor C catches people importing three-phase power logic into an arc process that doesn't use it.

A: Governing principle: fatigue cracks initiate at sharp discontinuities where stress concentration is highest. Here the hidden lack of fusion creates an effective notch at the weld toe, matching the delayed cyclic failure pattern. Distractor A explains toughness loss but doesn't create a discrete initiation site visible only after etch.

A: Governing principle: different NDT methods respond to different flaw geometries and require correlation. A planar UT signal conflicting with benign VT needs validation of technique and characterization before any accept/reject call. Distractor B appeals to hierarchy thinking instead of method capability.