2026-09-21T05:14:53Zhttps://bura.brunel.ac.uk/oai/request

oai:bura.brunel.ac.uk:2438/49662014-11-01T12:24:42Zcom_2438_23com_2438_58col_2438_3672col_2438_231

Fenn, R Lu, Yicheng 2011-04-04T14:51:32Z 2011-04-04T14:51:32Z 1992 http://bura.brunel.ac.uk/handle/2438/4966 This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. A computer controlled weld quality assurance system has been developed to detect weld defects ultrasonically whilst welding is in progress. This system, including a flash analogue to digital converter and built-in memories to store sampled data, a peak characters extractor and a welding process controller, enabled welding processes to be controlled automatically and welding defects to be detected concurrently with welding. In this way, the weld quality could be satisfactorily assured if no defect was detected and the welding cost was minimised either through avoiding similar defects to occur or by stopping the welding process if repair was necessary. This work demonstrated that the high temperature field around the weld pool was the major source of difficulties and unreliabilities in defect detection during welding and, had to be taken into account in welding control by ultrasonic means. The high temperatures not only influence ultrasonic characteristic parameters which are the defect judgement and assessment criterion, but also introduce noise into signals. The signal averaging technique and statistical analysis based on B-scan data have proved their feasibility to increase 'signal to noise ratio' effectively and to judge or assess weld defects. The hardware and the software for the system is explained in this work. By using this system, real-time 'A-scan' signals on screen display, and, A-scan, B-scan or three dimensional results can be printed on paper, or stored on disks, and, as a result, weld quality could be fully computerized. Submitted by Otue Ekong (lbsrooe@brunel.ac.uk) on 2011-04-04T14:51:20Z No. of bitstreams: 1 FulltextThesis.pdf: 15308281 bytes, checksum: e7b37b0405460fae180c888bc112ef24 (MD5) Approved for entry into archive by Otue Ekong(lbsrooe@brunel.ac.uk) on 2011-04-04T14:51:32Z (GMT) No. of bitstreams: 1 FulltextThesis.pdf: 15308281 bytes, checksum: e7b37b0405460fae180c888bc112ef24 (MD5) Made available in DSpace on 2011-04-04T14:51:32Z (GMT). No. of bitstreams: 1 FulltextThesis.pdf: 15308281 bytes, checksum: e7b37b0405460fae180c888bc112ef24 (MD5) Sino-British Friendship Scholarship Scheme en Brunel University School of Engineering and Design PhD Theses http://bura.brunel.ac.uk/bitstream/2438/4966/1/FulltextThesis.pdf Quality assurance system Weld defects Ultrasonic detection Computer system Real time defect detection in welds by ultrasonic means Thesis