Ultrasonic Testing Principles
Ultrasonic testing is a non-destructive testing method that uses ultrasound to detect internal defects in the material. Using a transmitter probe, ultrasonic waves are emitted from the surface of the component through a coupling agent. As ultrasonic waves propagate through the component, they generate different reflected signals (echoes) when they reach different interfaces. By exploiting the time difference between the different reflected signals sent to the probe, defects in the component can be detected. The approximate size, location, and nature of the defects can be determined based on the height and position of the echo signal displayed on the fluorescent screen.
Ultrasonic Testing Applications
Materials and defect properties relevant to ultrasonic testing:
- It is very suitable for testing metallic materials, and some non-metallic materials such as glass fiber/carbon fiber can also be tested. Mainly used to detect internal defects in workpieces. Surface defects are not as sensitive as PT/MT.
Applicable material areas for ultrasonic testing:
- Almost applicable to all product forming processes, including castings, forgings, welds, tubes and plates;
- The types of materials suitable for ultrasonic testing are:
- Cast iron;
- Various carbon and alloy steels;
- Aluminum, magnesium, copper, titanium, zirconium, hafnium and other non-ferrous metals and their alloys;
- Fiberglass/carbon fiber materials, concrete, etc.
The Ultrasonic Testing Process Flow
The ultrasonic testing process essentially includes: test procedure development, surface pretreatment, device configuration and sensitivity testing, testing and recording, as well as defect evaluation.
Surface preparation and equipment for ultrasonic testing
The. Surface requirements for inspection:
- Sufficient detection area and scanning width;
- The surface appearance must be checked and qualified;
- All paint, rust, spills and dirt in the probe movement area must be removed.
B. Items to check:
- matchmaker;
- ultrasonic flaw detector; Probe; data cable; Thermometer;
- pattern blocks; Compare test blocks.
Advantages and limitations of ultrasound examination
| Advantages of Ultrasonic Testing | Limitations of Ultrasonic Testing |
| Low work intensity | Long training periods, high demands on staff experience and significant differences in staff assessment |
| Light instrument | Instrument calibration is more complex than other methods |
| The thickness of the detected part is large | A certain scanning distance is required; Difficulty in detecting very thin parts; Difficult detection of parts with complex external structures |
| Sensitive to the type of surface/dangerous defects; Fast detection speed; Precise fault location | Insensitive to small volume defects; Qualitative difficulties |
| Light pollution/less affected by environmental factors | N/A |
Content Requirements for Ultrasound Test Protocols and Reports
- registration and report number;
- The standards and levels of inspection and acceptance execution;
- Detection object information: name, drawing number, part number, material, heat treatment status, detection location, detection proportion, surface condition, detection time, etc.;
- testing devices and equipment;
- model and number of test devices;
- Probe (type, chip size, K value of refraction angle, nominal frequency, etc.);
- test block template;
- matchmaker;
- process parameters for testing;
- Detection area and scanning position (surface, side, etc.);
- scanning method;
- detection sensitivity;
- clutch compensation
- Schematic representation of inspection;
- The location, size and echo height of the defects;
- Test data evaluation results;
- testing personnel;
- Exam time and location.
