One specialized application of X-ray radiography is weld inspection. Incomplete penetration or lack of fusion in welded metal can lead to joint weaknesses, presenting a common welding discontinuity. Lack of fusion can induce increased natural stress, potentially causing crack propagation. In radiography, lack of fusion appears as a dark area with well-defined and straight edges. X-ray radiography can detect cracks, distortions, and deformations in components subjected to pressure, temperature, and speed.