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AUTOMATED ULTRASONIC TESTING


1. INTRODUCTION

This paper discussed various applications where the ultrasonic inspection is carried out in an automated manner. Typical applications, where high through-put rates with sturdy system set-ups are mandatory, are the inspection of tubes, bars, billets and rails. Strip inspection and gas containers are common requests. Typical sites for the operation of automated inspection systems are steel and aluminium production plants and works where such products are further-on processed.

In many cases, the ultrasonic inspection is integrated into the production process and should not limit the output of the production line. Also, several testing systems can be applied in sequence. The operation of an eddy-current system for the detection of surface cracks in combination with an ultrasonic system for the detection of internal defects is often found.

The design of automated systems is always adapted for the respective inspection task. The main goals are the highest-possible coverage of the inspected profile, a high through-put rate, high sensitivity for small defects and high repeatability. Testing protocols are produced and document the proper inspection and all test parameter settings, such that faulty specimens and faulty system operation can later be traced back.

Non-destructive testing is an important part of a quality management system which controls all involvedproductions processes. In general, the production process is well organised such that high quality is produced. But it has to be possible to track systematic faults during the production, e.g. due to wear in the production tools. A second goal is to detect those defects which still occur even if the production process is stable. The stress on the materials steadily grows and the size of defects which have to be detected decreases. On the other hand, all testing methods have physical limitations. For instance, the ultrasonic wavelength limits the minimum flaw size which can be detected. But the ultrasonic wavelength cannot be lowered without limiting the penetration depth of the ultrasonic waves. Therefore, it has to be the goal of system operators and system manufacturers to push the physical limits little by little.

If the zero-defect-philosophy can ever be reached remains questionable! A first step would be, if operators and manufactures could agree on useful standards which clearly demonstrate the capabilities of automated testing systems. This remains difficult while most testing standards were made for manual inspection routines. The defined calibration routines often represent a difficulty for automated testing systems. One example is the ultrasonic bar inspection where flat-bottom-holes are not suitable judging on the dynamic operation of a system. Axially drilled holes are more practical, but are not mentioned in the testing standards.

2.COUPLING TECHNIQUES

Since air is a bad conductor for ultrasound, water is commonly used for the ultrasonic coupling. This usually governs the design of every testing system. The principal ways to couple ultrasound into the specimen during an automated inspection are now discussed

Immersion testing is a very common method for smaller specimens. Usually the entire specimen is immersed in water and a stage carrying the ultrasonic probes is moved along the specimen. The scanning routines can be more or less automated depending on the desired through-put. The degrees of freedom for moving the probes is mainly governed by the geometry of the specimen. In most cases, an x-y-scan are performed which results in a test report such as a C-scan. For an on-line inspection of long profiles, the immersion technique presents the difficulty to keep the water chamber filled while the specimen is entering and leaving the chamber. Other coupling methods are therefore mainly used.

Partial immersion means that only the bottom of the specimen is immersed in water. This technique is often used for tube and bar inspection. Since only a small portion of the specimen is immersed, only this portion can be inspected at a time. A rotational inspection is commonly used to produce full coverage during the inspection.

COURSE CONTENTS

  • To set up and operate AUT scanners.

  • To configure software for differing weld configurations.

  • Calibration of equipment.

  • To locate and evaluate defects

  • To select the correct type of probe/ machine parameters to examine welded butt joints in steel plate.

  • To report on the location and size of defects in typical welded butt joints.

  • To interpret code requirements.

  • Results.

  • Contact office for Course fee and Course duration