YB/T 951-2014Method of the ultrasonic testing for rails (English PDF)

3.1 Center of rail base

Any point on the longitudinal axis of the rail base surface of the rail.

3.2 Stability

The actual sensitivity change range during the rail flaw detection.

3.3 Stability indices

The limitation of stability during rail flaw detection.

3.4 Benchmark echo height

The reference height for determining the relative height of various echoes, generally in a percentage of the full scale. The range of the benchmark echo height: 50% to 80% of the full scale.

3.5 Modified value of sensitivity

The difference in sensitivity between the special comparative test piece and the static sample piece, the dynamic sample rail due to the material and surface condition.

3.6 Special comparative test piece

The test piece that is made, according to the method specified in GB/T 11259, by reference to the artificial defects that is required by the technical conditions of the rail.

3.7 Static sample piece

The test piece that is made, according to the specified artificial defects, of a rail of which the length is not less than 100 mm, the shape is same as the rail of flaw detection, the portion is same as the detection position, and there is no alarm-level defect.

3.8 Dynamic sample rail

The sample that is made, according to the specified equivalent artificial defect, of the same section rail with a length of not less than 6 m, no defect above the alarm level.

3.9 Reference sensitivity

The sensitivity value of the specified alarm gate that the artificial defect amplitude reaches on the dynamic sample rail.

5.1 Use the pulse reflection method to perform automatic inspection under the

condition that the probe and the rail move relative to each other.

5.2 During the inspection, coupling medium with good sound permeability and

no damage to the surface of the rail, such as water, shall be used.

10.1 It uses the general analog ultrasonic flaw detector or digital ultrasonic flaw

detector, of which, the technical requirements shall comply with the provisions of JB/T 10061.

10.2 It uses the multi-gate system; the initial position, width and alarm sensitivity

of the alarm gate are adjustable. After 8 hours of continuous operation, the alarm gate drift is no more than the sound path of 1 mm carbon steel.

10.3 The frequency of the flaw detector shall meet the requirements for flaw detection.

10.4 The flaw detector repeat frequency F is calculated according to Formula (1):

Where:

F -- repeat frequency, in per second (1/s);

v -- detection speed, in millimeters per second (mm/s);

B -- wafer width, in millimeters (mm).

13.2 Reference sensitivity adjustment: adjust the artificial defect echo on the

dynamic sample rail to the alarm state.

13.3 Stability adjustment: use dynamic rail to go back and forth for several times, so that the stability meets the requirements.

13.4 Flaw detection sensitivity adjustment: the flaw detection sensitivity shall be at least 4 dB higher than the reference sensitivity that is specified in 13.2.

13.5 Alarm gate adjustment: use the dynamic sample rail to adjust the gate

range to meet the flaw detection area and continuous monitoring requirements.

The noise within the gate range shall be lower than the threshold value of 12 dB.

13.6 Flaw detection: after the above ultrasonic test adjustments are completed, perform the flaw detection according to the flaw detection sensitivity.

14.1 Result determination: when the defect reflection wave exceeds the alarm

gate of flaw detection sensitivity in 13.4, the sensitivity shall be improved by 2 dB for further ultrasonic detection. Use the improved sensitivity to perform the ultrasonic detection, and when the defect signal of the rail still exceeds the threshold value, the section of the rail shall be scrapped or the defective part shall be cut off.

14.2 Marking: rails that fail to pass the flaw detection must be marked.

14.3 Record

14.3.1 Rails that fail to pass the flaw detection must have a flaw detection record.

14.3.2 The modification of flaw detection sensitivity must be recorded.

14.4 Flaw detection report

14.4.1 Rails that pass the flaw detection must be issued with a report.

14.4.2 Main contents of the flaw detection report: date, steel number, flaw

detection conditions, equipment, personnel, etc.

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