| dc.description.abstract | Radiography is an effective Non Destructive Testing (NDT) method for inspecting internal and
surface defects in engineering materials. It has been applied in this study to establish the integrity
of welded joints in Jua Kali fabricated products. The welds were evaluated and classified based
on type and size of defects observed as per ISO 5817 standard.
Specifically, welded Pull type of hoes and Tee type hinges were the Jua Kali products
investigated. Hoe specimens were sourced from Shauri moyo Jua Kali open air market in Nairobi
along Jogoo road. While hinge specimens were sourced from Nyeri Jua Kali shades next to Nyeri
Municipal Hall. Thirty samples of each were analyzed for defects at the Kenya Bureau of
Standards (KEBS). For comparison purposes, standard based welded specimens were also
evaluated. These specimens were obtained from Kenya Bureau of Standards NDT laboratory
where radiography test was carried out. Radiographic exposure was done in accordance to ISO
17636 standard, while evaluation and classification of defects was done in accordance to ISO 5817
standard.
Key instruments used include x ray machine of model 300, Kodak industrex AA400 films, lead
intensifying screens of 0.1 mm thick, 10FE EN wire penetrameter and DDS2 digital type of a
densitometer. X-ray star type of developer and Primax PT-F type of fixer were used in film
processing.
Lack of fusion was found to be the widely spread defect in Jua Kali welds inspected. Of the sixty
Jua Kali welds inspected, 52 or 83% were observed to have lack of fusion defect. Second in
occurrence was underfill, with a 70% representation. Other observed defects include; porosity,
undercut, burn through, slag and crack. The study showed that 86% to 100% of the Jua Kali welds
were defective hence non compliant to ISO 5817 standard. On the contrary, standard based welded
joints failed to comply with only 10% defective welds. The quality welds have been attributed to
application of welding standard by qualified welders.
The results show that at α = 0.5 level of significance, the three types of welds tested are
significantly different. Jua Kali hinges are heavily defective, followed by Jua Kali hoes, whereas
standard based welds were found to have very minimal defects.
Key recommendations include application of welding standards, use of Non Destructive Testing
(NDT) techniques for quality control and revision ofapplicable product standards to accommodate
Jua Kali innovations. Further study to correlate weld quality and product application has also been
recommended. | en_US |
