Development of Software Package for Automated Scanning of Multiple Surface Fuel Pellets Using Ultrasonic Imaging System

Transcription

1 115 Proceedings of the National Seminar & Exhibition on Non-Destructive Evaluation NDE 2009, December 10-12, 2009 Development of Software Package for Automated Scanning of Multiple Surface Fuel Pellets Using Ultrasonic Imaging System R.K. Jain 1, A.A. Agashe 1, T.S. Ananthakrishnan 1, V.M. Joshi 1, K.L.N. Chinababu 2 and S. Muralidhar 2 1 Electronics Division, 2 Metallic Fuels Division, Bhabha Atomic Research Centre, Mumbai, India rkjain@barc.gov.in Abstract Electronics Division, BARC in association with Metallic Fuels Division has developed an Ultrasonic Imaging System suitable for automated inspection of metallic objects with multiple surface geometry. The electronics hardware and application software for this system has been developed by Electronics Division and the design and development of the mechanical scanner was done by Metallic Fuels Division, BARC. The scanner has been successfully interfaced with the high-resolution ultrasonic imaging system (ULTIMA-200SP). A very significant feature of the ULTIMA-200SP system is the application software which performs various tasks of controlling various motors of scanner in addition to data acquisition, processing, analysis and information display. All these tasks must be carried out in a well synchronized manner for generating high resolution B Scan and C Scan images of test objects. In order to meet stringent requirements of the user, ULTIMA software has been extensively upgraded with new advanced features viz. Fast (coarse) and Slow (fine) scan for the speed optimization, Scanning of Cuboids and Cylindrical objects in the user defined region of interest, 3D view of the C-Scan, gray level, dual or multiple color plot in B-Scan, C-Scan and 3D views. This paper describes the advanced Windows based application software package developed at ED, BARC and highlights its salient features along with a brief description of the system hardware and relevant information. 1. Introduction Ultrasonics Imaging Techniques are now well established in Nondestructive Testing and Evaluation (NDT/E) of materials. However, automated ultrasonic inspection of objects having multiple surface geometry is yet a challenging task. This challenge is primarily due to the difficulty in maintaining the probe normal or occasionally at a desired angle to the surface of the object during ultrasonic inspection. The only viable option for automating the inspection is the immersion testing as it enables moving the probe over the object while ensuring proper acoustic coupling. The scanner-manipulator for inspection of a complex surface needs to have multiple-axes movement of the probe. A six axes precision mechanical scannermanipulator has been fabricated by Nuclear Fuels Group, BARC. This scanner functions under the control of ULTIMA- 200SP, an Ultrasonic Imaging System developed at Electronics Division BARC. ULTIMA-200SP system consists of PCI compatible cards for Ultrasonic Pulser/ Receiver and a 200 MSPS Digitizer. The dedicated software developed for this system controls all tasks, including transducer positioning using all the six axes, data acquisition, processing, analysis and information display that are necessary for generating high resolution B & C Scan images of test object. This paper highlights salient features of the application software along with a brief description of the system hardware and relevant information. 2. Ultrasonic Imaging System Main components of the ultrasonic imaging system are: Mechanical system for manipulating the probe-head to scan different objects Electrical system for drive-motors and their control for automation Electronic system for ultrasonic generation and its reception i.e. ULTIMA200SP Application software for integrating the mechanical systems and ultrasonic detection system to obtain the desired ultrasonic images 2.1 The Mechanical system The immersion ultrasonic testing is carried out in a tank 750mm(L) X 500mm(W) X 300mm(D). The positioning of the probe-head at a precise location is achieved through a fiveaxes movement. A sturdy bridge is used on which X, Y, Z motors are mounted to locate the probe precisely along Cartesian co-ordinates. A Gimbal mechanism is used to angle the probe θ degrees (+90º to -90º) with respect to perpendicular and swivel mechanism to rotate the probe through Φ (360º) degrees. Proximity sensors and limiting switches for all the axes movements have been provided at each end of all the axes providing Cartesian and Polar movements. Shaft position encoders serve as feedback

2 116 Jain et al. : Proceedings of the National Seminar & Exhibition on Non-Destructive Evaluation motion sensors and Digital Read Outs (DRO s) display the position value for all axes. 2.2 Electrical system All the drives, Cartesian and Polar, are motorized and use stepper-motors to move the probe-head. These are controllable using a PC through an appropriate motion controller interface card. The encoders and limit switches have been mounted at the extremities of all the axes to ensure safety of the drive mechanism and the system. A pendant mode has also been provided for manual control and movement of an individual axis. An emergency stop button that over-rides all commands and brings the system to a halt has been provided on the pendant. All the drives, power supplies and computer interfaces have been provided in a standard 19" electronic rack mount. 2.3 Electronic system This consists of two parts. First one controls the motion of the drives to position the probe-head accurately. The motors for all the axes are controlled through respective controller and all the encoders are connected to Digital Read Outs which display the co-ordinate location of each axis. The motors move through motion controller cards which are controlled by the application software. The second unit is the ULTIMA200SP whose hardware contains (i) PCI bus based pulser-receiver and (ii) a high speed digitizer card. The Pulser section generates the high voltage transmit pulse needed for the excitation of the ultrasonic transducer and the RF echo signals sensed by the same transducer are routed to the receiver section for amplification. The processed signal is fed to the digitizer card which is capable of sampling ultrasonic echo signals (i.e. A-Scan waveforms) at a maximum sampling rate of 200 MSPS. The digitizer also provides trigger signal to the Pulser receiver card as per the selected Pulse Repetition Frequency (PRF) ranging from 100Hz to 6KHz. For immersion scanning mode, first echo detection circuit, which initiates the acquisition on receiving the first echo (from top surface of the specimen) has also been incorporated. Block diagram of this system is given in Fig Application Software A powerful, Windows based software has been developed for this system. This software enables the operator to position the transducer suitably and select appropriate for acquiring optimum data for presenting the information in a meaningful way. Besides digitized A-Scan data, all the associated parameters (such as sampling rate, pulser receiver settings, Amplifier gain etc.) are also stored. This is extremely useful for future referencing. Provision has been made to display the A-scan data & amplitude spectrum (FFT) of a selected portion (of the A-Scan) simultaneously. The echo signals can thus be analyzed in frequency domain online. A status window indicating the major parameters selected by the user is always available on the screen. Another useful feature of the system is the provision of two independent user selectable gates. User can define and locate each gate at the desired portion of the A-Scan and also specify the desired amplitude threshold. If this threshold is crossed within the gate interval an audible beep is generated. Fig. 2 shows a typical display of the software. 3. Software Features Fig. 1 : Simplified block diagram of the Ultrasonic Imaging System

3 NDE 2009, December 10-12, This system is installed and is being used for one year at the user s site. With the feedback from the user, ULTIMA software has been extensively upgraded and new advanced features like Scanning of Cuboids and Cylindrical objects in the user defined region of interest, Fast and Slow scan for the speed optimization, 3D view of the C-Scan, Gray level, dual or multiple color plot in B-Scan have been incorporated. 3.1 Fast (coarse) and Slow (fine) scan for the speed optimization Typical scanning steps are: (Algorithm 1) In algorithm 1, there are three main operation carried out. One is motor movement (5 mm/sec), second one is echo data Algorithm 1 Fig. 2 : Initial Screen of the Ultrasonic Imaging System

4 118 Jain et al. : Proceedings of the National Seminar & Exhibition on Non-Destructive Evaluation acquisition with the sampling rate of MSPS to 200 MSPS (» 1280 to 5 nano seconds per sample) and third one is GUI updation (»msec). It can be seen that time is mainly taken up by motor movement and GUI updation. In the experimental setup we are using 25MSPS, 8K data and No averages for each channel. Dimension for the Test object is of the order of 200mm X 60mm and steps of 0.5 mm were used in both directions. Total time required for this acquisition is approx. 11 hrs. This scanning is termed as slow scan which can be adopted to obtain very fine details. Another way of acquiring the data is by using following algorithm: (Algorithm 2) In algorithm 2, motor movement and data acquisition is independent but both operation is synchronized with the timer interrupt. Our aim is to acquire data after every 0.5 mm in each direction and motor speed is 5 mm/sec so we require acquisition after every 50msec. Total time required for this acquisition is approx. 1 hrs giving an effective saving of time of the order of 11. This scanning is termed as fast scan. As shown in Fig. 3, display appears somewhat coarse, but the information content is more or less same as in the case of slow scan. 3.2 Scanning of Cuboids and Cylindrical objects in the user defined region of interest Fig. 3 : C-Scan with (a) Slow movement (b) Fast movement. (c) Experimental setup. Object may have different shapes viz. Cuboids or Cylindrical. For Cuboidal object, we require to move the motor in X and Y direction. For Cylindrical objects, theta and DZ motors movement is required. Facility is provided in C-Scan panel to select which type of object is used for scanning. Accordingly, motors are initialized and moved for getting B-Scan, C-Scan and 3-D image. Fig. 4 shows the C- Scan panel which provides facility for selecting different geometry D view of the echo from Cylindrical Object When we scan a cylindrical object, we want to visualize echoes within cylindrical region. To incorporate this feature, we used 3D graph activex control. One can see the object from any angle. Zooming/Panning feature to see the defect in details is also provided. Fig. 4 also shows the C-Scan panel with 3D view of cylindrical objects. Fig. 4 : C-Scan panel for selecting different geometry, Motion, Gray or color display, Dual color display, Invert color display.

5 NDE 2009, December 10-12, Gray level, dual or multiple color plot in B-Scan In B-Scan view, facility is provided to see the ultrasonic images either in gray scale or in dual color or in multiple colors. The input signal (0-255) is mapped in gray level of and is plotted in different gray intensity. For dual color display, slider is provided which decides the threshold value (between 0-255), below which every pixel is displayed as white and above pixels are displayed as black color. For multiple color display, color palette of 8 colors (with a window of 32) is provided. All the pixels in the same window are displayed in same color. Fig. 4 shows this feature. 4. Conclusion As shown in Fig. 3, there is no major change in the information display. It must be noted that no defect is missed in fast scan. Ability of detection of small defects and their qualitative as well as quantitative characterization by fast scan gives immense confidence in this methodology of NDT. Other features like Scanning of Cuboids and Cylindrical objects in the user defined region of interest, 3D view of the C-Scan, gray level, dual or multiple color plot in B-Scan, C- Scan and 3D views etc. are required for enhancing the user s experience, ease of operation and simplicity in understanding the ultrasonic images. So we can say that Ultrasonics has very bright prospects in the detection of small flaws with reliability and repeatability in reduced scanning time. Acknowledgments The authors place on record their thanks to Shri P.K. Mukhopadhyay, Head, ED; Dr. G.J. Prasad, Head, MFD; Shri G.P. Srivastava, Director EIG and Shri H.S. Kamath, Director NFG for their encouragement and support. This work involves the contribution of many colleagues in MFD and ED and the authors would like to place on record their appreciation to them. In particular the authors gratefully acknowledge the efforts and contributions made by Ms. Bhagyashree Sarade in interfacing the motor drive with the PC and Shri Harish Badgujar for performing test trials. References 1. Agashe A A, Badgujar H D, Chinnababu K L N, Jain R K, Mittal R K, Muralidhar S, Randale G D, Sivakumar U, Tamhane A B, Ananthakrishnan T S, Joshi V M, Mahule K N and Prasad G J, An Ultrasonic Imaging System for Inspection of Objects with a Multiple Surface Geometry, Proc. Of the National Sminar on Challenges and Innovations in NDT (NDE 2009) held at Lonavala, Mumbai (Dec. 1999) 2. Joshi V M, More S R, Patankar V H, Jyoti P, Kataria S K, ULTIMA 100+: An Ultrasonic imaging system for non destructive testing of materials, BARC news letter No. 204, (Jan 2001) 3. Motiwala P D, Agashe A A, More S R, Joshi V M and Kataria S K, PCI bus based high speed digitizer for capture and analysis of Ultrasonic signals, Proc. Of the International conference and Exhibition on Ultrasonics (ICEU 99) held at New Delhi (Dec. 1999) 4. Joshi V M, More S R, Motiwala P D, Agashe A A, Lalwani S K, Ananthakrishnan T S and Kataria S K, Development of PCI bus based PC add-on cards for waveform analysis & video image capture, B.A.R.C. news letter No. 196, May 2000.