Method for ultrasonically measuring a height of lack of penetration in a weld and ultrasonic flaw detector therefor

摘要

A method for measuring the height of lack of penetration includes steps of: using a probe applying an ultrasonic beam to an object to define a dividing curve of an echo height; using the probe applying the ultrasonic beam to the object at a predetermined angle to scan surfaces of a plurality of weld test samples having different heights of lack of penetration, a weld bead being disposed on the surface; obtaining beam path length information based on the dividing curve of the echo height and the height of an F echo reflected by a part of lack of penetration of a weld and returned to the probe; and formulating a regression equation showing a relation between the beam path length information and the height of lack of penetration.