What might indicate an absence of fusion in a weld on a radiograph?

The indication of an absence of fusion in a weld on a radiograph is characterized by the presence of two parallel dark lines. This occurrence typically represents a lack of complete bonding between the base metal and the weld metal. When fusion does not occur, voids or gaps may form between these two surfaces, and these will appear as distinct lines on the radiographic image. The parallel lines serve as visual evidence of insufficient penetration and bonding, which are critical for the weld's overall strength and integrity.

In radiographic testing, the clarity of these indications plays an essential role in assessing weld quality. While other options may display various attributes on a radiograph, only the appearance of two parallel dark lines specifically suggests a failure in weld fusion, making it a clear marker for potential defects needing further evaluation.