Automatic infrared testing system DIO5000

- application for circle and square bars 70 – 300 mm, surface flaw detection
- flaw detection possibility 0.3 mm – 3.5 mm
- edge measurement, 100% surface measurement
- beginning and end of bars fully tested
- non-contact method

The automated system for thermographic crack detection uses brief pulsed eddy currents to heat steel components under inspection. Cracks, if present, will disturb the current flow and so generate changes in the temperature profile in the crack area. These changes of temperature are visualized using an infrared camera. The image acquired by the infrared camera is evaluated through an image processing system. The advantages afforded by the system are its inspection times, its excellent flaw detection sensitivity and its ability to detect hidden, subsurface cracks. The automated system consists of four IR cameras (each side of steel bar is evaluated at a time), coil, high frequency generator, and control place with computers. The system is a part of the inspection line where the subsurface and surface cracks are searched. If the crack is present, the cracked place is automatically marked. The components without cracks are then deposited apart from defective blocks. The system is fully automated and its ability is to evaluate four meter blocks within 20 seconds. This is the real reason for using this system in real industrial applications.
The automated system for infrared thermographic testing was proposed and finally developed in Starmans company Ltd. First of all, the construction of the system was discussed. The goal of the proposed system was to test the square steel blocks created by hot rolling. After the rolling the steel blocks were cut and finally shaped into quadruples. These were tested in our automated system to detect cracks or defects.
In general, the system consists of the following main parts: high frequency generator, high frequency coils, signal processing units, IR detectors (cameras), equipment and software for displaying and evaluation of indications, complete equipment for defect marking, wetting unit, mechanical parts as mechanical frame for fixing of IR detectors, mechanical frame for HF coils.
The high frequency coils are power supplied by the high frequency generator. The coils are used for steel block heating. Blocks were automatically moved onto the belt and wheels, and introduced to the coil place. Generally, the blocks speed depends on the viewing field of the IR camera and used computer system. Both used components allow to achieve linear testing speed of more than 0,2 m/s.
When the steel block was heated, it was automatically scanned by infrared cameras. The whole system contains four IR cameras. Each camera scans one side of quadruple block.

Based on drawings and visualizations, the system was constructed and technical parts were solved. The system contains a huge mechanical frame, with mounted infrared cameras (detectors). The main advantage of the mounted cameras is that these can be automatically adjusted. For the appropriate heating of material surface, the coil has to be in the center of the material. For this requirement the frame is automatically adjusted. All adjustments are engaged in the software. Before the material is introduced in to the coil, the surface is wet by steam.
This makes the homogenous distribution of the magnetic field and homogenous heating of the material surface. By passing the steel blocks through the coil the material surface is scanned by infrared cameras and acquired images are sent to PC. At the end of the system, detected cracks are automatically marked with a special marking device.
After the infrared testing, the bars are consequently tested in ultrasonic testing system.

 This feature makes it easier for attendants

Principle of material surface heating is based on induction heating. For the safe material surface heating, the special high frequency generator for induction heating was designed.

Software
Created hardware mechanical parts were placed as a part of the full inspection system (infrared + ultrasonic for subsurface flaw detection). When the material is wet, passed through the coils and heated, the IR detectors (cameras) are used for each surface scanning. Measured data is sent to industrial PC through USB port and processed and evaluated in software DIO5000. The software DIO5000 contains basic control functions.

Based on the proposal and theoretical analysis, the automated thermographic system using infrared detectors were designed and installed in industrial applications. This system as a part of the automated non-destructive line was used for the sufrace detection on square steel bars.
The system was successfully installed and the first test was accomplished on the calibration gauge containing small and large defects. Besides the small changes and parameter settings (hardware and software) on the system, the system reliably marked all defects on the calibration gauge.

The system is fully automated and in case there is a different material size, it can be easily transposed by coil changing. Developed infrared cameras involve implemented signal processing algorithms. By theoretical and experimental measurements, the methods for efficient noise suppression and crack detection were proposed. The presence of surface and subsurface flaws is automatically indicated and finally evaluated on display monitor. The presence of ambient light noise is suppressed by algorithms based on simple mathematical equations using square average.