Objective
This research project seeks to demonstrate that mechanised ultrasonic testing can be successfully applied to the testing of welds in joints of complex geometry : such configurations may be found in a wide variety of welded constructions, but the most extreme examples are to be found at fabricated nodes in steel tubular lattice structures of the types used for off-shore installations, where a number of tubular members of different sizes intersect at a variety of angles.
The main objectives of the project are :
- Development of modelling routines to predict the scanning pattern to maintain full coverage of any given geometry;
- Development of signal processing and display software;
- Determination of optimum ultrasonic test parameters and demonstration of test system on laboratory scale samples;
- Design and production of a prototype scanner for large scale samples;
- System trials in air and in water on large scale samples.
During the first year of research work has been concentrated on ultrasonic procedure development and simulation and modelling of ultrasonic inspection and geometry changes.
Within procedure developments initial work has been carried out using a 900 T-node specimen containing extensive fatigue crack and the P-scan system (Projection Image scanning, a computerised ultrasonic system for weld inspection, developed and marketed by The Danish Welding Institute) in its A-scan Collection mode.
Using manual scanners with different angle probes valuable information for determining a mechanised scan pattern, was collected with regard to minimising the number of probe positions necessary to obtain full coverage and reduce scan time.
In combination with the above, work was carried out to determine the number of axis of freedom for a scanning mechanism which is able to cope with all probe positions and orientations.
Development of a software for modelling and simulation of ultrasonic wave propagation has begun. During the first year of research, work has concentrated on producing an overall description of the system, stipulating requirements to hardware/software and logical modelling of the system.
At present a first prototype coping with simple geometries has been completed with the purpose of verifying the concept of the system.
The final version will be capable of depicting images of the centre beam as well as the dispersal of the beam in a cross section of a complex structures based on the echo pulse technique. The system will be able to handle typical standard constructional elements representative for the off-shore industry, where tubular elements are the main constructional part.
The system will if possible be a real time system, which means that the images of the cross section and the A-scans will be presented in parallel while moving the probe on the structural element.
The system will include two various way of use, one is to prepare NDT-procedures before inspection in the fields to ensure reliable and reproducible examinations.
The second is to evaluate results gathered from examinations in the fields.
Application of ultrasonic testing is essential to ensure freedom from significant defects of welds in high quality fabrications.
A severe limitation of ultrasonic testing is the difficulty which the technician experiences in manipulating the ultrasonic probe to ensure adequate coverage of the welded joints, in combination with difficulties of understanding the interaction of the ultrasonic beam with any defect present. This problem is exacerbated by complex or varying weld geometries, which are common in large tubular off-shore structures.
Thus despite the fact that generally suitable computer controllable and mechanised ultrasonic testing equipment has already been developed, neither the ultrasonic techniques nor the equipment is applicable to the off-shore sector.
The develpments required to achieve the objectives of this project will be based on a typical off-shore node and comprises computer simulation and modelling of geometry variations and the ultrasonic pulse-echo technique, laboratory investigations, field tests and outlining requirements and specifications for technique and equipment for underwater ultrasonic inspection of such complex structures.
The project is divided into two main parts : Part 1 consists of laboratory studies culminating in a demonstration that the approach is valid using laboratory scale samples of a variety of complex geometries.
Part 2 will consists of procurement of number of large scale samples, production of scanner device to enable them to be tested and the carrying out of full inspection on the samples obtained to determine the performance of the complete system.
The various activities in each part is described below :
Part 1 :
Task 1 : Industrial studies qnd projectplanning
Task 2 : Procedure development and manufacture of test samples
Task 3 : Modelling and simulation of geometry changes and ultrasonic inspection
Task 4 : Development of testing software
Task 5 : Examination of test samples
Task 6 : Full scale node samples
Task 7a: Automatic scanner concept.
Part 2 :
Task 7b: Automatic scanner design and manufacture
Task 8 : Interfacing of scanner device and ultrasonic equipment Task 9 : Examination of full scaloe test node welds
Task 10: Underwater testing
Task 11: Recommandation for an underwater scanner.
Programme(s)
Topic(s)
Call for proposal
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DEM - Demonstration contractsCoordinator
2605 BROENDBY
Denmark