Quantification of the reliability of flaw detection (NDT) using probability of detection (POD) based on synthetic data

Transcription

1 Quantification of the reliability of flaw detection (NDT) using probability of detection (POD) based on synthetic data Håkan Wirdelius /SCeNDT Chalmers

2 SCeNDT Scientific Center of Non Destructive Testing Chalmers University of Technology, Materials and Manufacturing Technology Håkan Wirdelius, director, theoretical mechanics, MM UT/MM DRT Gert Persson, ass. Prof., theoretical mechanics, MM UT/FEM Kenneth Hamberg, ass. Prof., material science, Material/NDT Peter Hammersberg, ass. Prof., material science, POD/MM DRT Lars Hammar, graduate student, DRT/ ET Qingwei Liu, graduate student, MM UT Surface and microstructure engineering, MMT Lars Nyborg, Prof., material science, Material Dynamics, Applied Mechanics Anders Boström, Prof., theoretical mechanics, MM UT Peter Bövik, ass. Prof., theoretical mechanics, MM UT/MM ET Imaging and Image Analysis, Signals and Systems Tomas Gustavsson, Prof., image reconstruction, MM DRT

3 SCeNDT Research area Develop and experimental validation of mathematical models of different NDT methods Apply mathematical modelling in the development of new NDT techniques Evaluate new commercial NDT techniques Education Graduate courses in advanced non-destructive testing Education for industry (master level) The NDT laboratory High resolution X-ray technique (HiReX) Semi-mechanized phased array-system

4 When is Quantitative NDE required? Chalmers University of Technology Structural integrity assumes that flaws of an assumed design size will not propagate into size that will induce failures in service => dependent on detection and removal of flaws larger than this size Stress amplitude (MPa) Defect depth (mm) New fatigue and fracture/damage tolerance criteria New applications or use of a design life extension of an in-service component or introduction of damage tolerance in life-cycle management (also new components)

5 NDE capabilities Probability of detection curve (POD) Flaw and object variables NDE variables (method, equipment, procedure and process) Calibration Acceptance/decision variables (procedure) Human factor Reliability Capability (POD) Reproducibility (calibration) Repeatability (NDE process control in application)

6 Degradation mechanism Defects introduced during welding: Lack of fusion Inclusions Pores Slag Hot cracks Cold cracks

7 Degradation mechanism In-service induced cracks: Stress corrosion cracks IGSCC TGSCC IDSCC Fatigue cracks Mechanical Thermal Corrosion

8 Mathematical modeling? Test pieces and artificial defects (static) Volumetric defects: cheap and available parameters can be well specified Crack like defects (notches):? Real cracks: expensive, time demanding and few available parameters can be specified Mathematical modeling (dynamic) Cost-effective Time saving Individual parameters can be altered Enables Worst Case studies

9 Mathematical modelling of UT simsundt Chalmers University of Technology The simsundt program (freeware) consists of a Windows -based preprocessor and postprocessor UTDefect used as a mathematical kernel Model of ultrasonic backscattering due to grain growth in a welded region The result can be read by a number of commercial analysis software Reduce number of test pieces and synthetic defects

10 Quantification of the reliability of flaw detection for non-destructive techniques using probability of detection (POD) based on synthetic data WP 1 Development of simulation model: Develop a mathematical model of a phased array probe and incorporate it into the simsundt software. The correlation between prescribed boundary conditions and resulting wave propagation within the material will be validated.

11 Quantification of the reliability of flaw detection for non-destructive techniques using probability of detection (POD) based on synthetic data WP 2 Experimental verification of the model: Experimentally verify and proper validate the developed model for a very specific case. The case has been chosen in order to ensure reliability when it comes to relevant parameters such as defect depths, sizes and characteristics. P-wave corner echo: db µs Rectangular crack P- and S-wave corner echo: db 0 mm Strip like-single S-wave corner echo: 1.6 db µs 55.2 mm Strip like-subdiv. 7 elements

12 Quantification of the reliability of flaw detection for non-destructive techniques using probability of detection (POD) based on synthetic data Indicators of NDT capability: a 50, a 90 and a 90/95 (95% confidence) 1 0,9 0,8 0,7 Probability of Detection 0,6 0,5 0,4 0,3 0,2 POD(a) 95% Miss Hit 0, ,025 0,05 0,075 0,1 0,125 0,15 a (defect length) WP 3 Procedure for synthetic data based POD: Develop a technique that uses mathematical models in order to develop a data base that will be used as the basis for a POD curve. The procedure shall be for a specific NDT task based on experiences made in WP1 and 2. WP 4 Experimental validation of the synthetic POD: Experimentally validate the above evolved POD curve. This in order to optimize the inspection procedure and also to make it as a convention tool in the development of POD characteristics.

13 Quantification of the reliability of flaw detection for non-destructive techniques using probability of detection (POD) based on synthetic data

14 Quantification of the reliability of flaw detection for non-destructive techniques using probability of detection (POD) based on synthetic data Budget Year Personnel (900h SR) 630* Computer 45 UT phased array equipment 250 UT probes (2) 70 Travel 15 Sum year (ksek) Year Personnel (1100h SR) 770* POD software 40 Test pieces 50 Travel 10 Sum year (ksek) Year Personnel (750h SR) 525* Travel 35 Conf. fees 10 Sum year (ksek) Total sum year (ksek)