Undercut

A groove or depression at the toe of a weld where the base metal has been melted away but not properly filled by weld metal. Undercut reduces cross-sectional area and creates stress concentration, making it a critical weld defect. It is readily detected by visual inspection and NDT methods. Acceptance criteria vary by application; critical applications typically reject any undercut, while less critical applications allow limited undercut.

Detection and Assessment

Undercut must be detected early and accurately characterized to determine safety implications. Multiple NDT methods may be required for comprehensive evaluation.

Acceptance Criteria

Industry standards such as ASME Section V, AWS D1.1, and API standards provide specific acceptance limits. Whether a detected undercut is acceptable depends on material, component function, and applicable code.

Best Practices

• Always follow applicable NDT standards and procedures
• Use properly calibrated and maintained equipment
• Ensure personnel are properly trained and certified
• Document inspection procedures and results completely
• Keep current with industry standards and best practices