Development of Automated Analysis Tools for Ultrasonic Investigations of Elastomeric Insulating Materials

Transcription

1 Slide 1/15 Introduction Measuring Setup Results Conclusion Development of Automated Analysis Tools for Ultrasonic Investigations of Elastomeric Insulating Materials Dipl.-Ing. Philipp Walter Diploma Thesis Aachen Univ.-Prof.Dr.-Ing. A. Schnettler Supervisor: Dr.-Ing. C. Cornelissen

2 Slide 2/15: Introduction Project Ultrasonic diagnosis for condition assessment of non-destructivity high spatial resolution early detection wide range of detectable faults low investment needs elastomeric insulating materials in the field of high voltage engineering silicone rubber EPDM cable accessories isolators

3 Slide 3/15: Introduction Measuring Principles Basics: - Penetration of the test piece with ultrasonic impulses (1-20MHz) - Reflection of the impulses on inhomogeneities like flaws or interfaces (= change of the acoustic impedance) - Detection of the damped echo by the transducer - Information about: - depth of the inhomogeneity - damping - sound velocity transducer flaw initial pulse flaw echo backwall echo impulse-echo-method: emitter = receiver

4 Slide 4/15: Measuring setup Measuring Setup: Micro Positioning System

5 Slide 5/15 : Measuring Setup Graphical Representation: Amplitude Map Scanning 0,2 mm <Min Min Max >Max

6 Slide 6/15: Objectives Development of Automated Analysis Tools for Ultrasonic Investigations of Elastomeric Insulating Materials Ultrasonic testing tasks: detection localisation evaluation classification

7 Slide 7/15: Results Detection Detectability depends on: Size and geometry of the flaw Material of the flaw Depth of the flaw Attenuation of the material Example: In silicone rubber, glass spheres with a diameter of 100µm are detectable within a depth of 30 mm.

8 Slide 8/15: Results Localisation Object recognition: Segmentation of the graphical representation Image processing: development of an adopted spatial procedure Classification of every pixel depends on: - peak value - measured points in the neighbourhood with similar depth and similar peak value Development of a gradient method to trace the object contour Information about number, location, dimensions, perimeter and shape of objects

9 Slide 9/15 : Results Scanning: Graphical Representation Peak Value < Min mm 781 Example: Silicone rubber with treeing needle (1mm) and breakdown channel

10 Slide 10/15: Results Scanning: Graphical Representation (segmented) Peak Value < Min mm 781 Example: Silicone rubber with treeing needle (1mm) and breakdown channel

11 Slide 11/15: Results Evaluation of Inhomogeneities Difficulties: Sound field divergence Ratio: transducer (5mm) / flaw (>0,1mm) Defect sizing by use of a reference method : The reflection of the flaw is comparable to the reflection of a sphere with a diameter of x mm Manufacturing of reference blocks including glass spheres Measurements on these reference blocks Objective, reproducible basis of evaluation sphere diameter [µm] 5mm 1mm peak value [db]

12 Slide 12/15: Results Classification Two aspects: Classification regarding the a) type of the inhomogeniety b) quality of the overall insulating system a) - Classification is possible - Exemplarily, a pattern recognition for the pattern needle was carried out - Further investigations can determine the range of different inhomogeneities occurring in practice b) Correlation between the results of the ultrasonic inspection and a following electrical test

13 Slide 13/15: Results Measurement Setup for High Voltage Joints

14 Slide 14/15: Results Measuring a High Voltage Joint Process: Primary scanning: detection scan Automated flaw detection and localisation Detailed scanning: evaluation scan Evaluation of the flaw regarding comparative size, shape, depth, Classification of the joint depending on quantity of flaws and their characteristics uncritical critical <Min Min Max >Max

15 Slide 15/15: Conclusion Conclusion Ultrasonic diagnostic processes are appropriate methods for condition assessment of elastomeric insulation materials. To achieve industrial appliance, the measurement and analysis of the measured data have to be executed automatically. An analysis tool is developed which is able to afford automated detailed assessment. Information about quantity, position, size and shape of the inhomogeneities can be obtained. The present ultrasonic system now offers a wide variety of applications in the quality assurance and fabrication control in the range of elastomeric insulating materials.

16 Slide 16/15 Development of Automated Analysis Tools for Ultrasonic Investigations of Elastomeric Insulating Materials Dipl.-Ing. Philipp Walter Diploma Thesis Aachen Univ.-Prof.Dr.-Ing. A. Schnettler Supervisor: Dr. C. Cornelissen

17 Slide 17/15: Outlook Issue on Interfaces: Debonding Example: compound isolator core: GRP (glass-fibre reinforced plastic) cover: silicone rubber Chemical bonding: primer Faults during production process can lead to extensive delamination GRProd primer Reduced electric strength! armature silicon rubber compound-isolator

18 Slide 18/15: Outlook Issue on Interfaces: Debonding Diagnostic principle: ultrasonic measurements of the interface along the isolator axis Reflectance factor provides information about the adhesion of the interface Preliminary investigation: interface silicone-rubber / epoxy resin glue silicone rubber glue w/o glue epoxy resin 5 mm Investigated test piece (glue on the left side) Graphical representation of the interface

19 Slide 19/15: Measuring setup Immersion Technique transducer water test piece flaw