. Transactions. i\ = X = ~i = ^ Likewise for 13-in. () gap X = = ^Applying the same method for 11-in. () gap X = = Now at 15-in. () gap and 20 in. (50 cm.) distance milli-ampere-minutes gives a good exposure through 3^^ in. ( mm.) of corresponding darkening would have been produced on* a bare plate byan exposure of milliampere-minutes. This corresponds to Q in ourformulak We may therefore write, since Qo = E, = E . e-ii^-lOE = e*i«-log, 10^ = ;logio lOE = ; E = Ho logio-^
. Transactions. i\ = X = ~i = ^ Likewise for 13-in. () gap X = = ^Applying the same method for 11-in. () gap X = = Now at 15-in. () gap and 20 in. (50 cm.) distance milli-ampere-minutes gives a good exposure through 3^^ in. ( mm.) of corresponding darkening would have been produced on* a bare plate byan exposure of milliampere-minutes. This corresponds to Q in ourformulak We may therefore write, since Qo = E, = E . e-ii^-lOE = e*i«-log, 10^ = ;logio lOE = ; E = Ho logio-^ ;. 156 RADIOGRAPHY OF METALS where x is the thickness of the steel in inches or E = where x is the thickness of the steel in centimeters. The corresponding formulas for 13-in. () gap are E = %Q logio^ : {x in inches) E = ^^0 logio^ {x in centimeters).. Fig. 4a. X 1 Fig. approximate formulas for 11-in. () gap are E = % logio^ (re in inches) E = % logio^ {x in centimeters). It remained to find the thickness of the smallest air-inclusion whichcould be radiographed in steel at 15-in. gap. For this purpose two plates WHEELER P. DAVEY 157 of steel were taken. The faces were machined flat and in one of them aslot was cut, thus giving a wedge of air. The slot and the faces of the steelplates were then ground smooth. When completed, each plate was %in. ( mm.) thick. The air wedge was 10 in. (250 mm.) long, 1 in.(25 mm.) wide and %4 in. ( mm.) thick at its thick end. When thetwo plates were bolted together, the air wedge simulated a blow-hole in a
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
