The grain size of the abrasive particle is important in determining surface finish and material removal rate. Small grit sizes produce better finishes, while larger grain sizes permit larger material removal rates. Thus, a choice must be made between these two objectives when, selecting abrasive grain size. The selection of grit size also depends to some extent on the hardness of the work material. Harder work materials require smaller grain sizes to cut effectively, while softer materials require larger grit sizes.The grit size is measured using a screen mesh procedure.In this procedure, smaller grit sizes have larger numbers and vice versa. Grain sizes used in grinding wheels typically range between 8 and 250. Grit size 8 is very coarse and size 250 is very fine. Finer grit sizes are used for lapping and superfinishing.
(Mikell P.Groover, Fundamentals of Modern Manufacturing , materials,processes, and systems third edition page 596-597)
Butt Weld 26 Mart 10:38
The butt weld is a connecting weld between plates which is largely free from force flow diversion and hence has a low stress concentration factor.ıt makes a joint in the same plane or only at a slight angle.It has the following variants;square butt weld, single V butt weld, single U butt weld with or without root face, U and V welds also arise as double welds(Double V weld identical to X weld), and the raised edge butt weld.
(Dieter Radaj,Design and analysis of Fatigue Resistans Welded Structures, page 38)
Precipitation hardening 26Mart 17:37
Precipitation hardening involves the formation of fine particles (precipitates) that act to block the movement of dislocations and thus strengthen and harden the metal. It is the principal heat treatment for strengthening alloys of aluminum, copper, magnesium, nickel, and other nonferrous metals. Precipitation hardening can also be used to strengthen steel alloys that cannot form martensite by the usual method.
(Mikell P.Groover, Fundamentals of Modern Manufacturing , materials,processes, and systems
third edition page 652)
Resistance Welding 26 mart 20:39
Resistance welding (RW) is a group of fusion-welding processes thai uses a combination of heat and pressure to accomplish coalescence, the heat being generated by electrical resistance to current flow at the junction to be welded. The principal components in resistance welding are shown in Figure 31.12 for a resistance spot-weiding operation, the most widely used process in the group. The components include workparts to be welded (usually sheet metal parts), two opposing electrodes, a means of applying pressure to squeeze the parts between the electrodes, and an AC power supply from which a controlled current can be applied. The operation results in a fused zone between the two parts, called a weld nugget in spot welding.By comparison to arc welding, resistance welding uses no shielding gases, flux, or filler metal; and the electrodes that conduct electrical power to the process are noncon-sumable. RW is classified as fusion welding because the applied heat almost always causes melting of the faying surfaces. However, there are exceptions. Some welding operations based on resistance heating use temperatures below the melting points of the base metals, so fusion does not occur.
(Mikell P.Groover, Fundamentals of Modern Manufacturing , materials,processes, and systems third edition page 716)
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