Browsing by Author "Watmon, Titus Bitek"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Characteristics of resistance spot welding using annular recess electrodes
    (Elsevier: Journal of Advanced Joining Processes, 2020-07) Watmon, Titus Bitek; Wandera, Catherine; Apora, James
    Resistance spot welding is widely used in manufacturing industries, such as automobile structural body manufacture, rail vehicle construction, electronics manufacture, battery manufacture, etc. Resistance spot weld integrity is of paramount importance in the manufacturing industry, especially in automotive body joining to ensure that the automobile bodies can withstand the stress levels that the vehicle is subjected in operation. A number of factors - including electrode geometry, electrode force, welding current and welding time - influence the quality of the resistance spot weld. The electrode material that ensures electrical conductivity and compressive strength and electrode geometry defined by the electrode tip profile, shape, size are important factors in resistance spot welding. This paper discusses the comparative performance of resistance spot welding electrodes with annular recess design and the conventional solid design in welding of a 1 mm thick steel sheet used in construction of automobile structural bodies. The copper-based electrodes used in this study were prepared as described in the ISO 5182:2008 Standard. The annular recess electrode was designed using SolidWorks Version 2015; a hole measuring 4 mm deep and 2.50 mm in diameter was created centrally on the electrode tip and filled with heat resistant mixture of cement and kaolin ceramics. The effects of applied electrode force, current, and weld time on weld-integrity were investigated for the two designs of resistance spot welding electrodes. Linear regression analysis of data obtained established that the weld strength and nugget diameter was higher for the annular recess electrode than the conventional solid electrode. An analysis of variance established that the observed variation of the nugget diameter with weld time was statistically significant but the variations of weld strength with applied electrode force and variation of nugget diameter with current were not statistically significant which may require further study.
  • Thumbnail Image
    Item
    Coated tools with crater‐like surface structures have enhanced performance
    (AIP Conference Proceedings, 2010-10-18) Watmon, Titus Bitek
    This paper presents the result of an investigation into the cutting characteristics of electrical discharge machined (EDMed) surface‐modified carbide cutting tool inserts. The tool inserts were coated with Titanium Nitride (TiN) by physical vapour deposition (PVD) method. In this study, comparative cutting tests using TiN coated control specimens with no EDM surface structures and TiN coated EDMed tools with crater‐like surface topographies were carried out on mild steel. Various cutting speeds, up to an increase of 30% of the tool manufacturer’s recommended speed were investigated. Twenty five cuts (passes) were carried out for each inserts at the speeds investigated. After every five cuts (passes), microscopic pictures of the tool wear profiles were taken in order to monitor the progressive wear on the rake face and, on the flank of the insert. The power load was monitored for each cut using an on board meter on the machine. Results obtained confirmed advantages of cutting at all speeds investigated using EDMed coated inserts in terms of reduced tool wear. Furthermore, the surface finish on the work‐piece was consistently better for the EDMed inserts. It is therefore concluded, that TiN coated EDMed crater‐like surface structure on tool inserts can considerably improve tool performance.