This test group is designed to assess the quality of the metal structure and the non-existence of defects in it. The non-existence of defects monitoring is usually used during the certification of welding technologies and welders. After welding on the control sheet material, the samples are cut from it, which are subjected to the control for the non-existence of defects, which makes it possible to identify possible violations in the structure of the weld metal.
For the destructive non-existence of defects monitoring, three main types of tests are used: the bend test, the breakdown test of the welded joint specimen with two notches along the weld and the breakdown test of the corner sample. The deficiency can also be checked by means of non-destructive testing, for which radiographic and ultrasonic methods are often used. The first type of test (bend test) can be carried out in different ways. This is probably the most common type of test, allowing you to judge the acceptability of the control sample welded during the certification of the welder.
The various types of bending tests are usually called, depending on the orientation of the weld to the flexural force. There are three types of samples with the transverse bend of the seam: face bend, root bend and side bend. In all three cases, the weld crosses the longitudinal axis of the specimen, and the type of test is determined by the side of the weld, which is subjected to stress during the test. This means that when the seam is folded out, the front side undergoes tension, etc.
The bending tests are usually performed using the bending device. These tests are of three types: bending with a mandrel, bending with a roller with a mandrel and bending with a mandrel by a wrapping method. The standard bend test device with a mandrel consists of a plunger (also called a mandrel or pusher) and a conjugate matrix, by means of which the U shape is previously given to the rectilinear sample.
For the bending test, the sample is placed on the supports (shoulders) of the matrix, turning it to the matrix by the side on which the voltage is to act. The plunger is then positioned on the appropriate point and forcefully pressed against the specimen until it bends by 180° to U-form. The sample is then removed and evaluated.