The invention discloses a quantification ultrasonic nondestructive detection method of a
diameter of a spot weld nugget. The quantification ultrasonic nondestructive detection method of the
diameter of the spot weld nugget includes the steps that step 1, a transmitting probe and a receiving probe are installed on the two sides of the spot weld nugget of a spot weld sample; step 2, a relation curve of amplitude B and a displacement x is drawn; step 3, an actual nugget
diameter is measured; step 4, a straight line is made in the relation curve, the difference of two horizontal coordinates of the
cut curve is the sum of the actual nugget diameter and the
effective diameter of the receiving probe, and a corresponding B0 value of the current
vertical coordinate of the straight line is recoded and stored; step 5, the transmitting probe and the receiving probe are installed on the two sides of the spot weld nugget of an actual
welding spot to be detected, when the receiving probe receives that the amplitude B reaches the B0 for the first time, a displacement Xa is recorded, when the receiving probe receives that the amplitude B reaches the B0 for the second time, a displacement Xb is recorded, Xt=Xb-Xa, and the diameter of the spot weld nugget of the actual
welding spot to be detected is Xt-dmin. The quantification ultrasonic nondestructive detection method of the diameter of the spot weld nugget quantitatively detects the nugget diameter of the resistance
spot welding quickly and accurately and visually reflects the
welding spot quality.